Update dependencies

45 files changed, 5158 insertions, 762 deletions

diff --git a/vendor/golang.org/x/crypto/acme/acme.go b/vendor/golang.org/x/crypto/acme/acme.go
index e8388b0..8257ffb 100644
--- a/vendor/golang.org/x/crypto/acme/acme.go
+++ b/vendor/golang.org/x/crypto/acme/acme.go
@@ -14,7 +14,6 @@
 package acme
 
 import (
-	"bytes"
 	"context"
 	"crypto"
 	"crypto/ecdsa"
@@ -23,6 +22,8 @@ import (
 	"crypto/sha256"
 	"crypto/tls"
 	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
@@ -33,7 +34,6 @@ import (
 	"io/ioutil"
 	"math/big"
 	"net/http"
-	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -42,6 +42,9 @@ import (
 // LetsEncryptURL is the Directory endpoint of Let's Encrypt CA.
 const LetsEncryptURL = "https://acme-v01.api.letsencrypt.org/directory"
 
+// idPeACMEIdentifierV1 is the OID for the ACME extension for the TLS-ALPN challenge.
+var idPeACMEIdentifierV1 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 30, 1}
+
 const (
 	maxChainLen = 5       // max depth and breadth of a certificate chain
 	maxCertSize = 1 << 20 // max size of a certificate, in bytes
@@ -76,6 +79,22 @@ type Client struct {
 	// will have no effect.
 	DirectoryURL string
 
+	// RetryBackoff computes the duration after which the nth retry of a failed request
+	// should occur. The value of n for the first call on failure is 1.
+	// The values of r and resp are the request and response of the last failed attempt.
+	// If the returned value is negative or zero, no more retries are done and an error
+	// is returned to the caller of the original method.
+	//
+	// Requests which result in a 4xx client error are not retried,
+	// except for 400 Bad Request due to "bad nonce" errors and 429 Too Many Requests.
+	//
+	// If RetryBackoff is nil, a truncated exponential backoff algorithm
+	// with the ceiling of 10 seconds is used, where each subsequent retry n
+	// is done after either ("Retry-After" + jitter) or (2^n seconds + jitter),
+	// preferring the former if "Retry-After" header is found in the resp.
+	// The jitter is a random value up to 1 second.
+	RetryBackoff func(n int, r *http.Request, resp *http.Response) time.Duration
+
 	dirMu sync.Mutex // guards writes to dir
 	dir   *Directory // cached result of Client's Discover method
 
@@ -99,15 +118,12 @@ func (c *Client) Discover(ctx context.Context) (Directory, error) {
 	if dirURL == "" {
 		dirURL = LetsEncryptURL
 	}
-	res, err := c.get(ctx, dirURL)
+	res, err := c.get(ctx, dirURL, wantStatus(http.StatusOK))
 	if err != nil {
 		return Directory{}, err
 	}
 	defer res.Body.Close()
 	c.addNonce(res.Header)
-	if res.StatusCode != http.StatusOK {
-		return Directory{}, responseError(res)
-	}
 
 	var v struct {
 		Reg    string `json:"new-reg"`
@@ -142,7 +158,7 @@ func (c *Client) Discover(ctx context.Context) (Directory, error) {
 //
 // In the case where CA server does not provide the issued certificate in the response,
 // CreateCert will poll certURL using c.FetchCert, which will result in additional round-trips.
-// In such scenario the caller can cancel the polling with ctx.
+// In such a scenario, the caller can cancel the polling with ctx.
 //
 // CreateCert returns an error if the CA's response or chain was unreasonably large.
 // Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features.
@@ -166,14 +182,11 @@ func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration,
 		req.NotAfter = now.Add(exp).Format(time.RFC3339)
 	}
 
-	res, err := c.retryPostJWS(ctx, c.Key, c.dir.CertURL, req)
+	res, err := c.post(ctx, c.Key, c.dir.CertURL, req, wantStatus(http.StatusCreated))
 	if err != nil {
 		return nil, "", err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusCreated {
-		return nil, "", responseError(res)
-	}
 
 	curl := res.Header.Get("Location") // cert permanent URL
 	if res.ContentLength == 0 {
@@ -196,26 +209,11 @@ func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration,
 // Callers are encouraged to parse the returned value to ensure the certificate is valid
 // and has expected features.
 func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]byte, error) {
-	for {
-		res, err := c.get(ctx, url)
-		if err != nil {
-			return nil, err
-		}
-		defer res.Body.Close()
-		if res.StatusCode == http.StatusOK {
-			return c.responseCert(ctx, res, bundle)
-		}
-		if res.StatusCode > 299 {
-			return nil, responseError(res)
-		}
-		d := retryAfter(res.Header.Get("Retry-After"), 3*time.Second)
-		select {
-		case <-time.After(d):
-			// retry
-		case <-ctx.Done():
-			return nil, ctx.Err()
-		}
+	res, err := c.get(ctx, url, wantStatus(http.StatusOK))
+	if err != nil {
+		return nil, err
 	}
+	return c.responseCert(ctx, res, bundle)
 }
 
 // RevokeCert revokes a previously issued certificate cert, provided in DER format.
@@ -241,14 +239,11 @@ func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte,
 	if key == nil {
 		key = c.Key
 	}
-	res, err := c.retryPostJWS(ctx, key, c.dir.RevokeURL, body)
+	res, err := c.post(ctx, key, c.dir.RevokeURL, body, wantStatus(http.StatusOK))
 	if err != nil {
 		return err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusOK {
-		return responseError(res)
-	}
 	return nil
 }
 
@@ -257,7 +252,7 @@ func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte,
 func AcceptTOS(tosURL string) bool { return true }
 
 // Register creates a new account registration by following the "new-reg" flow.
-// It returns registered account. The account is not modified.
+// It returns the registered account. The account is not modified.
 //
 // The registration may require the caller to agree to the CA's Terms of Service (TOS).
 // If so, and the account has not indicated the acceptance of the terms (see Account for details),
@@ -329,14 +324,11 @@ func (c *Client) Authorize(ctx context.Context, domain string) (*Authorization,
 		Resource:   "new-authz",
 		Identifier: authzID{Type: "dns", Value: domain},
 	}
-	res, err := c.retryPostJWS(ctx, c.Key, c.dir.AuthzURL, req)
+	res, err := c.post(ctx, c.Key, c.dir.AuthzURL, req, wantStatus(http.StatusCreated))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusCreated {
-		return nil, responseError(res)
-	}
 
 	var v wireAuthz
 	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
@@ -353,14 +345,11 @@ func (c *Client) Authorize(ctx context.Context, domain string) (*Authorization,
 // If a caller needs to poll an authorization until its status is final,
 // see the WaitAuthorization method.
 func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorization, error) {
-	res, err := c.get(ctx, url)
+	res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
-		return nil, responseError(res)
-	}
 	var v wireAuthz
 	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
 		return nil, fmt.Errorf("acme: invalid response: %v", err)
@@ -387,56 +376,58 @@ func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
 		Status:   "deactivated",
 		Delete:   true,
 	}
-	res, err := c.retryPostJWS(ctx, c.Key, url, req)
+	res, err := c.post(ctx, c.Key, url, req, wantStatus(http.StatusOK))
 	if err != nil {
 		return err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusOK {
-		return responseError(res)
-	}
 	return nil
 }
 
 // WaitAuthorization polls an authorization at the given URL
 // until it is in one of the final states, StatusValid or StatusInvalid,
-// or the context is done.
+// the ACME CA responded with a 4xx error code, or the context is done.
 //
 // It returns a non-nil Authorization only if its Status is StatusValid.
 // In all other cases WaitAuthorization returns an error.
 // If the Status is StatusInvalid, the returned error is of type *AuthorizationError.
 func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorization, error) {
-	sleep := sleeper(ctx)
 	for {
-		res, err := c.get(ctx, url)
+		res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
 		if err != nil {
 			return nil, err
 		}
-		retry := res.Header.Get("Retry-After")
-		if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
-			res.Body.Close()
-			if err := sleep(retry, 1); err != nil {
-				return nil, err
-			}
-			continue
-		}
+
 		var raw wireAuthz
 		err = json.NewDecoder(res.Body).Decode(&raw)
 		res.Body.Close()
-		if err != nil {
-			if err := sleep(retry, 0); err != nil {
-				return nil, err
-			}
-			continue
-		}
-		if raw.Status == StatusValid {
+		switch {
+		case err != nil:
+			// Skip and retry.
+		case raw.Status == StatusValid:
 			return raw.authorization(url), nil
-		}
-		if raw.Status == StatusInvalid {
+		case raw.Status == StatusInvalid:
 			return nil, raw.error(url)
 		}
-		if err := sleep(retry, 0); err != nil {
-			return nil, err
+
+		// Exponential backoff is implemented in c.get above.
+		// This is just to prevent continuously hitting the CA
+		// while waiting for a final authorization status.
+		d := retryAfter(res.Header.Get("Retry-After"))
+		if d == 0 {
+			// Given that the fastest challenges TLS-SNI and HTTP-01
+			// require a CA to make at least 1 network round trip
+			// and most likely persist a challenge state,
+			// this default delay seems reasonable.
+			d = time.Second
+		}
+		t := time.NewTimer(d)
+		select {
+		case <-ctx.Done():
+			t.Stop()
+			return nil, ctx.Err()
+		case <-t.C:
+			// Retry.
 		}
 	}
 }
@@ -445,14 +436,11 @@ func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorizat
 //
 // A client typically polls a challenge status using this method.
 func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, error) {
-	res, err := c.get(ctx, url)
+	res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
-		return nil, responseError(res)
-	}
 	v := wireChallenge{URI: url}
 	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
 		return nil, fmt.Errorf("acme: invalid response: %v", err)
@@ -479,16 +467,14 @@ func (c *Client) Accept(ctx context.Context, chal *Challenge) (*Challenge, error
 		Type:     chal.Type,
 		Auth:     auth,
 	}
-	res, err := c.retryPostJWS(ctx, c.Key, chal.URI, req)
+	res, err := c.post(ctx, c.Key, chal.URI, req, wantStatus(
+		http.StatusOK,       // according to the spec
+		http.StatusAccepted, // Let's Encrypt: see https://goo.gl/WsJ7VT (acme-divergences.md)
+	))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	// Note: the protocol specifies 200 as the expected response code, but
-	// letsencrypt seems to be returning 202.
-	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusAccepted {
-		return nil, responseError(res)
-	}
 
 	var v wireChallenge
 	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
@@ -545,7 +531,7 @@ func (c *Client) HTTP01ChallengePath(token string) string {
 // If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
 //
 // The returned certificate is valid for the next 24 hours and must be presented only when
-// the server name of the client hello matches exactly the returned name value.
+// the server name of the TLS ClientHello matches exactly the returned name value.
 func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
 	ka, err := keyAuth(c.Key.Public(), token)
 	if err != nil {
@@ -572,7 +558,7 @@ func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tl
 // If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
 //
 // The returned certificate is valid for the next 24 hours and must be presented only when
-// the server name in the client hello matches exactly the returned name value.
+// the server name in the TLS ClientHello matches exactly the returned name value.
 func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
 	b := sha256.Sum256([]byte(token))
 	h := hex.EncodeToString(b[:])
@@ -593,6 +579,52 @@ func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tl
 	return cert, sanA, nil
 }
 
+// TLSALPN01ChallengeCert creates a certificate for TLS-ALPN-01 challenge response.
+// Servers can present the certificate to validate the challenge and prove control
+// over a domain name. For more details on TLS-ALPN-01 see
+// https://tools.ietf.org/html/draft-shoemaker-acme-tls-alpn-00#section-3
+//
+// The token argument is a Challenge.Token value.
+// If a WithKey option is provided, its private part signs the returned cert,
+// and the public part is used to specify the signee.
+// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
+//
+// The returned certificate is valid for the next 24 hours and must be presented only when
+// the server name in the TLS ClientHello matches the domain, and the special acme-tls/1 ALPN protocol
+// has been specified.
+func (c *Client) TLSALPN01ChallengeCert(token, domain string, opt ...CertOption) (cert tls.Certificate, err error) {
+	ka, err := keyAuth(c.Key.Public(), token)
+	if err != nil {
+		return tls.Certificate{}, err
+	}
+	shasum := sha256.Sum256([]byte(ka))
+	extValue, err := asn1.Marshal(shasum[:])
+	if err != nil {
+		return tls.Certificate{}, err
+	}
+	acmeExtension := pkix.Extension{
+		Id:       idPeACMEIdentifierV1,
+		Critical: true,
+		Value:    extValue,
+	}
+
+	tmpl := defaultTLSChallengeCertTemplate()
+
+	var newOpt []CertOption
+	for _, o := range opt {
+		switch o := o.(type) {
+		case *certOptTemplate:
+			t := *(*x509.Certificate)(o) // shallow copy is ok
+			tmpl = &t
+		default:
+			newOpt = append(newOpt, o)
+		}
+	}
+	tmpl.ExtraExtensions = append(tmpl.ExtraExtensions, acmeExtension)
+	newOpt = append(newOpt, WithTemplate(tmpl))
+	return tlsChallengeCert([]string{domain}, newOpt)
+}
+
 // doReg sends all types of registration requests.
 // The type of request is identified by typ argument, which is a "resource"
 // in the ACME spec terms.
@@ -612,14 +644,14 @@ func (c *Client) doReg(ctx context.Context, url string, typ string, acct *Accoun
 		req.Contact = acct.Contact
 		req.Agreement = acct.AgreedTerms
 	}
-	res, err := c.retryPostJWS(ctx, c.Key, url, req)
+	res, err := c.post(ctx, c.Key, url, req, wantStatus(
+		http.StatusOK,      // updates and deletes
+		http.StatusCreated, // new account creation
+	))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	if res.StatusCode < 200 || res.StatusCode > 299 {
-		return nil, responseError(res)
-	}
 
 	var v struct {
 		Contact        []string
@@ -649,59 +681,6 @@ func (c *Client) doReg(ctx context.Context, url string, typ string, acct *Accoun
 	}, nil
 }
 
-// retryPostJWS will retry calls to postJWS if there is a badNonce error,
-// clearing the stored nonces after each error.
-// If the response was 4XX-5XX, then responseError is called on the body,
-// the body is closed, and the error returned.
-func (c *Client) retryPostJWS(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, error) {
-	sleep := sleeper(ctx)
-	for {
-		res, err := c.postJWS(ctx, key, url, body)
-		if err != nil {
-			return nil, err
-		}
-		// handle errors 4XX-5XX with responseError
-		if res.StatusCode >= 400 && res.StatusCode <= 599 {
-			err := responseError(res)
-			res.Body.Close()
-			// according to spec badNonce is urn:ietf:params:acme:error:badNonce
-			// however, acme servers in the wild return their version of the error
-			// https://tools.ietf.org/html/draft-ietf-acme-acme-02#section-5.4
-			if ae, ok := err.(*Error); ok && strings.HasSuffix(strings.ToLower(ae.ProblemType), ":badnonce") {
-				// clear any nonces that we might've stored that might now be
-				// considered bad
-				c.clearNonces()
-				retry := res.Header.Get("Retry-After")
-				if err := sleep(retry, 1); err != nil {
-					return nil, err
-				}
-				continue
-			}
-			return nil, err
-		}
-		return res, nil
-	}
-}
-
-// postJWS signs the body with the given key and POSTs it to the provided url.
-// The body argument must be JSON-serializable.
-func (c *Client) postJWS(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, error) {
-	nonce, err := c.popNonce(ctx, url)
-	if err != nil {
-		return nil, err
-	}
-	b, err := jwsEncodeJSON(body, key, nonce)
-	if err != nil {
-		return nil, err
-	}
-	res, err := c.post(ctx, url, "application/jose+json", bytes.NewReader(b))
-	if err != nil {
-		return nil, err
-	}
-	c.addNonce(res.Header)
-	return res, nil
-}
-
 // popNonce returns a nonce value previously stored with c.addNonce
 // or fetches a fresh one from the given URL.
 func (c *Client) popNonce(ctx context.Context, url string) (string, error) {
@@ -742,58 +721,12 @@ func (c *Client) addNonce(h http.Header) {
 	c.nonces[v] = struct{}{}
 }
 
-func (c *Client) httpClient() *http.Client {
-	if c.HTTPClient != nil {
-		return c.HTTPClient
-	}
-	return http.DefaultClient
-}
-
-func (c *Client) get(ctx context.Context, urlStr string) (*http.Response, error) {
-	req, err := http.NewRequest("GET", urlStr, nil)
-	if err != nil {
-		return nil, err
-	}
-	return c.do(ctx, req)
-}
-
-func (c *Client) head(ctx context.Context, urlStr string) (*http.Response, error) {
-	req, err := http.NewRequest("HEAD", urlStr, nil)
-	if err != nil {
-		return nil, err
-	}
-	return c.do(ctx, req)
-}
-
-func (c *Client) post(ctx context.Context, urlStr, contentType string, body io.Reader) (*http.Response, error) {
-	req, err := http.NewRequest("POST", urlStr, body)
-	if err != nil {
-		return nil, err
-	}
-	req.Header.Set("Content-Type", contentType)
-	return c.do(ctx, req)
-}
-
-func (c *Client) do(ctx context.Context, req *http.Request) (*http.Response, error) {
-	res, err := c.httpClient().Do(req.WithContext(ctx))
+func (c *Client) fetchNonce(ctx context.Context, url string) (string, error) {
+	r, err := http.NewRequest("HEAD", url, nil)
 	if err != nil {
-		select {
-		case <-ctx.Done():
-			// Prefer the unadorned context error.
-			// (The acme package had tests assuming this, previously from ctxhttp's
-			// behavior, predating net/http supporting contexts natively)
-			// TODO(bradfitz): reconsider this in the future. But for now this
-			// requires no test updates.
-			return nil, ctx.Err()
-		default:
-			return nil, err
-		}
+		return "", err
 	}
-	return res, nil
-}
-
-func (c *Client) fetchNonce(ctx context.Context, url string) (string, error) {
-	resp, err := c.head(ctx, url)
+	resp, err := c.doNoRetry(ctx, r)
 	if err != nil {
 		return "", err
 	}
@@ -845,24 +778,6 @@ func (c *Client) responseCert(ctx context.Context, res *http.Response, bundle bo
 	return cert, nil
 }
 
-// responseError creates an error of Error type from resp.
-func responseError(resp *http.Response) error {
-	// don't care if ReadAll returns an error:
-	// json.Unmarshal will fail in that case anyway
-	b, _ := ioutil.ReadAll(resp.Body)
-	e := &wireError{Status: resp.StatusCode}
-	if err := json.Unmarshal(b, e); err != nil {
-		// this is not a regular error response:
-		// populate detail with anything we received,
-		// e.Status will already contain HTTP response code value
-		e.Detail = string(b)
-		if e.Detail == "" {
-			e.Detail = resp.Status
-		}
-	}
-	return e.error(resp.Header)
-}
-
 // chainCert fetches CA certificate chain recursively by following "up" links.
 // Each recursive call increments the depth by 1, resulting in an error
 // if the recursion level reaches maxChainLen.
@@ -873,14 +788,11 @@ func (c *Client) chainCert(ctx context.Context, url string, depth int) ([][]byte
 		return nil, errors.New("acme: certificate chain is too deep")
 	}
 
-	res, err := c.get(ctx, url)
+	res, err := c.get(ctx, url, wantStatus(http.StatusOK))
 	if err != nil {
 		return nil, err
 	}
 	defer res.Body.Close()
-	if res.StatusCode != http.StatusOK {
-		return nil, responseError(res)
-	}
 	b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1))
 	if err != nil {
 		return nil, err
@@ -925,65 +837,6 @@ func linkHeader(h http.Header, rel string) []string {
 	return links
 }
 
-// sleeper returns a function that accepts the Retry-After HTTP header value
-// and an increment that's used with backoff to increasingly sleep on
-// consecutive calls until the context is done. If the Retry-After header
-// cannot be parsed, then backoff is used with a maximum sleep time of 10
-// seconds.
-func sleeper(ctx context.Context) func(ra string, inc int) error {
-	var count int
-	return func(ra string, inc int) error {
-		count += inc
-		d := backoff(count, 10*time.Second)
-		d = retryAfter(ra, d)
-		wakeup := time.NewTimer(d)
-		defer wakeup.Stop()
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		case <-wakeup.C:
-			return nil
-		}
-	}
-}
-
-// retryAfter parses a Retry-After HTTP header value,
-// trying to convert v into an int (seconds) or use http.ParseTime otherwise.
-// It returns d if v cannot be parsed.
-func retryAfter(v string, d time.Duration) time.Duration {
-	if i, err := strconv.Atoi(v); err == nil {
-		return time.Duration(i) * time.Second
-	}
-	t, err := http.ParseTime(v)
-	if err != nil {
-		return d
-	}
-	return t.Sub(timeNow())
-}
-
-// backoff computes a duration after which an n+1 retry iteration should occur
-// using truncated exponential backoff algorithm.
-//
-// The n argument is always bounded between 0 and 30.
-// The max argument defines upper bound for the returned value.
-func backoff(n int, max time.Duration) time.Duration {
-	if n < 0 {
-		n = 0
-	}
-	if n > 30 {
-		n = 30
-	}
-	var d time.Duration
-	if x, err := rand.Int(rand.Reader, big.NewInt(1000)); err == nil {
-		d = time.Duration(x.Int64()) * time.Millisecond
-	}
-	d += time.Duration(1<<uint(n)) * time.Second
-	if d > max {
-		return max
-	}
-	return d
-}
-
 // keyAuth generates a key authorization string for a given token.
 func keyAuth(pub crypto.PublicKey, token string) (string, error) {
 	th, err := JWKThumbprint(pub)
@@ -993,14 +846,25 @@ func keyAuth(pub crypto.PublicKey, token string) (string, error) {
 	return fmt.Sprintf("%s.%s", token, th), nil
 }
 
+// defaultTLSChallengeCertTemplate is a template used to create challenge certs for TLS challenges.
+func defaultTLSChallengeCertTemplate() *x509.Certificate {
+	return &x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().Add(24 * time.Hour),
+		BasicConstraintsValid: true,
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+	}
+}
+
 // tlsChallengeCert creates a temporary certificate for TLS-SNI challenges
 // with the given SANs and auto-generated public/private key pair.
+// The Subject Common Name is set to the first SAN to aid debugging.
 // To create a cert with a custom key pair, specify WithKey option.
 func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) {
-	var (
-		key  crypto.Signer
-		tmpl *x509.Certificate
-	)
+	var key crypto.Signer
+	tmpl := defaultTLSChallengeCertTemplate()
 	for _, o := range opt {
 		switch o := o.(type) {
 		case *certOptKey:
@@ -1009,7 +873,7 @@ func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) {
 			}
 			key = o.key
 		case *certOptTemplate:
-			var t = *(*x509.Certificate)(o) // shallow copy is ok
+			t := *(*x509.Certificate)(o) // shallow copy is ok
 			tmpl = &t
 		default:
 			// package's fault, if we let this happen:
@@ -1022,17 +886,10 @@ func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) {
 			return tls.Certificate{}, err
 		}
 	}
-	if tmpl == nil {
-		tmpl = &x509.Certificate{
-			SerialNumber:          big.NewInt(1),
-			NotBefore:             time.Now(),
-			NotAfter:              time.Now().Add(24 * time.Hour),
-			BasicConstraintsValid: true,
-			KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
-			ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
-		}
-	}
 	tmpl.DNSNames = san
+	if len(san) > 0 {
+		tmpl.Subject.CommonName = san[0]
+	}
 
 	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, key.Public(), key)
 	if err != nil {
diff --git a/vendor/golang.org/x/crypto/acme/autocert/autocert.go b/vendor/golang.org/x/crypto/acme/autocert/autocert.go
index b101020..c8fa4e6 100644
--- a/vendor/golang.org/x/crypto/acme/autocert/autocert.go
+++ b/vendor/golang.org/x/crypto/acme/autocert/autocert.go
@@ -24,8 +24,9 @@ import (
 	"fmt"
 	"io"
 	mathrand "math/rand"
+	"net"
 	"net/http"
-	"strconv"
+	"path"
 	"strings"
 	"sync"
 	"time"
@@ -80,8 +81,9 @@ func defaultHostPolicy(context.Context, string) error {
 }
 
 // Manager is a stateful certificate manager built on top of acme.Client.
-// It obtains and refreshes certificates automatically,
-// as well as providing them to a TLS server via tls.Config.
+// It obtains and refreshes certificates automatically using "tls-sni-01",
+// "tls-sni-02" and "http-01" challenge types, as well as providing them
+// to a TLS server via tls.Config.
 //
 // You must specify a cache implementation, such as DirCache,
 // to reuse obtained certificates across program restarts.
@@ -96,11 +98,11 @@ type Manager struct {
 	// To always accept the terms, the callers can use AcceptTOS.
 	Prompt func(tosURL string) bool
 
-	// Cache optionally stores and retrieves previously-obtained certificates.
-	// If nil, certs will only be cached for the lifetime of the Manager.
+	// Cache optionally stores and retrieves previously-obtained certificates
+	// and other state. If nil, certs will only be cached for the lifetime of
+	// the Manager. Multiple Managers can share the same Cache.
 	//
-	// Manager passes the Cache certificates data encoded in PEM, with private/public
-	// parts combined in a single Cache.Put call, private key first.
+	// Using a persistent Cache, such as DirCache, is strongly recommended.
 	Cache Cache
 
 	// HostPolicy controls which domains the Manager will attempt
@@ -125,8 +127,10 @@ type Manager struct {
 
 	// Client is used to perform low-level operations, such as account registration
 	// and requesting new certificates.
+	//
 	// If Client is nil, a zero-value acme.Client is used with acme.LetsEncryptURL
-	// directory endpoint and a newly-generated ECDSA P-256 key.
+	// as directory endpoint. If the Client.Key is nil, a new ECDSA P-256 key is
+	// generated and, if Cache is not nil, stored in cache.
 	//
 	// Mutating the field after the first call of GetCertificate method will have no effect.
 	Client *acme.Client
@@ -138,27 +142,63 @@ type Manager struct {
 	// If the Client's account key is already registered, Email is not used.
 	Email string
 
-	// ForceRSA makes the Manager generate certificates with 2048-bit RSA keys.
+	// ForceRSA used to make the Manager generate RSA certificates. It is now ignored.
 	//
-	// If false, a default is used. Currently the default
-	// is EC-based keys using the P-256 curve.
+	// Deprecated: the Manager will request the correct type of certificate based
+	// on what each client supports.
 	ForceRSA bool
 
+	// ExtraExtensions are used when generating a new CSR (Certificate Request),
+	// thus allowing customization of the resulting certificate.
+	// For instance, TLS Feature Extension (RFC 7633) can be used
+	// to prevent an OCSP downgrade attack.
+	//
+	// The field value is passed to crypto/x509.CreateCertificateRequest
+	// in the template's ExtraExtensions field as is.
+	ExtraExtensions []pkix.Extension
+
 	clientMu sync.Mutex
 	client   *acme.Client // initialized by acmeClient method
 
 	stateMu sync.Mutex
-	state   map[string]*certState // keyed by domain name
-
-	// tokenCert is keyed by token domain name, which matches server name
-	// of ClientHello. Keys always have ".acme.invalid" suffix.
-	tokenCertMu sync.RWMutex
-	tokenCert   map[string]*tls.Certificate
+	state   map[certKey]*certState
 
 	// renewal tracks the set of domains currently running renewal timers.
-	// It is keyed by domain name.
 	renewalMu sync.Mutex
-	renewal   map[string]*domainRenewal
+	renewal   map[certKey]*domainRenewal
+
+	// tokensMu guards the rest of the fields: tryHTTP01, certTokens and httpTokens.
+	tokensMu sync.RWMutex
+	// tryHTTP01 indicates whether the Manager should try "http-01" challenge type
+	// during the authorization flow.
+	tryHTTP01 bool
+	// httpTokens contains response body values for http-01 challenges
+	// and is keyed by the URL path at which a challenge response is expected
+	// to be provisioned.
+	// The entries are stored for the duration of the authorization flow.
+	httpTokens map[string][]byte
+	// certTokens contains temporary certificates for tls-sni challenges
+	// and is keyed by token domain name, which matches server name of ClientHello.
+	// Keys always have ".acme.invalid" suffix.
+	// The entries are stored for the duration of the authorization flow.
+	certTokens map[string]*tls.Certificate
+}
+
+// certKey is the key by which certificates are tracked in state, renewal and cache.
+type certKey struct {
+	domain  string // without trailing dot
+	isRSA   bool   // RSA cert for legacy clients (as opposed to default ECDSA)
+	isToken bool   // tls-sni challenge token cert; key type is undefined regardless of isRSA
+}
+
+func (c certKey) String() string {
+	if c.isToken {
+		return c.domain + "+token"
+	}
+	if c.isRSA {
+		return c.domain + "+rsa"
+	}
+	return c.domain
 }
 
 // GetCertificate implements the tls.Config.GetCertificate hook.
@@ -181,21 +221,23 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 	if !strings.Contains(strings.Trim(name, "."), ".") {
 		return nil, errors.New("acme/autocert: server name component count invalid")
 	}
-	if strings.ContainsAny(name, `/\`) {
+	if strings.ContainsAny(name, `+/\`) {
 		return nil, errors.New("acme/autocert: server name contains invalid character")
 	}
 
+	// In the worst-case scenario, the timeout needs to account for caching, host policy,
+	// domain ownership verification and certificate issuance.
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
 	defer cancel()
 
 	// check whether this is a token cert requested for TLS-SNI challenge
 	if strings.HasSuffix(name, ".acme.invalid") {
-		m.tokenCertMu.RLock()
-		defer m.tokenCertMu.RUnlock()
-		if cert := m.tokenCert[name]; cert != nil {
+		m.tokensMu.RLock()
+		defer m.tokensMu.RUnlock()
+		if cert := m.certTokens[name]; cert != nil {
 			return cert, nil
 		}
-		if cert, err := m.cacheGet(ctx, name); err == nil {
+		if cert, err := m.cacheGet(ctx, certKey{domain: name, isToken: true}); err == nil {
 			return cert, nil
 		}
 		// TODO: cache error results?
@@ -203,8 +245,11 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 	}
 
 	// regular domain
-	name = strings.TrimSuffix(name, ".") // golang.org/issue/18114
-	cert, err := m.cert(ctx, name)
+	ck := certKey{
+		domain: strings.TrimSuffix(name, "."), // golang.org/issue/18114
+		isRSA:  !supportsECDSA(hello),
+	}
+	cert, err := m.cert(ctx, ck)
 	if err == nil {
 		return cert, nil
 	}
@@ -216,27 +261,135 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 	if err := m.hostPolicy()(ctx, name); err != nil {
 		return nil, err
 	}
-	cert, err = m.createCert(ctx, name)
+	cert, err = m.createCert(ctx, ck)
 	if err != nil {
 		return nil, err
 	}
-	m.cachePut(ctx, name, cert)
+	m.cachePut(ctx, ck, cert)
 	return cert, nil
 }
 
+func supportsECDSA(hello *tls.ClientHelloInfo) bool {
+	// The "signature_algorithms" extension, if present, limits the key exchange
+	// algorithms allowed by the cipher suites. See RFC 5246, section 7.4.1.4.1.
+	if hello.SignatureSchemes != nil {
+		ecdsaOK := false
+	schemeLoop:
+		for _, scheme := range hello.SignatureSchemes {
+			const tlsECDSAWithSHA1 tls.SignatureScheme = 0x0203 // constant added in Go 1.10
+			switch scheme {
+			case tlsECDSAWithSHA1, tls.ECDSAWithP256AndSHA256,
+				tls.ECDSAWithP384AndSHA384, tls.ECDSAWithP521AndSHA512:
+				ecdsaOK = true
+				break schemeLoop
+			}
+		}
+		if !ecdsaOK {
+			return false
+		}
+	}
+	if hello.SupportedCurves != nil {
+		ecdsaOK := false
+		for _, curve := range hello.SupportedCurves {
+			if curve == tls.CurveP256 {
+				ecdsaOK = true
+				break
+			}
+		}
+		if !ecdsaOK {
+			return false
+		}
+	}
+	for _, suite := range hello.CipherSuites {
+		switch suite {
+		case tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+			tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305:
+			return true
+		}
+	}
+	return false
+}
+
+// HTTPHandler configures the Manager to provision ACME "http-01" challenge responses.
+// It returns an http.Handler that responds to the challenges and must be
+// running on port 80. If it receives a request that is not an ACME challenge,
+// it delegates the request to the optional fallback handler.
+//
+// If fallback is nil, the returned handler redirects all GET and HEAD requests
+// to the default TLS port 443 with 302 Found status code, preserving the original
+// request path and query. It responds with 400 Bad Request to all other HTTP methods.
+// The fallback is not protected by the optional HostPolicy.
+//
+// Because the fallback handler is run with unencrypted port 80 requests,
+// the fallback should not serve TLS-only requests.
+//
+// If HTTPHandler is never called, the Manager will only use TLS SNI
+// challenges for domain verification.
+func (m *Manager) HTTPHandler(fallback http.Handler) http.Handler {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	m.tryHTTP01 = true
+
+	if fallback == nil {
+		fallback = http.HandlerFunc(handleHTTPRedirect)
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.HasPrefix(r.URL.Path, "/.well-known/acme-challenge/") {
+			fallback.ServeHTTP(w, r)
+			return
+		}
+		// A reasonable context timeout for cache and host policy only,
+		// because we don't wait for a new certificate issuance here.
+		ctx, cancel := context.WithTimeout(r.Context(), time.Minute)
+		defer cancel()
+		if err := m.hostPolicy()(ctx, r.Host); err != nil {
+			http.Error(w, err.Error(), http.StatusForbidden)
+			return
+		}
+		data, err := m.httpToken(ctx, r.URL.Path)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusNotFound)
+			return
+		}
+		w.Write(data)
+	})
+}
+
+func handleHTTPRedirect(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "GET" && r.Method != "HEAD" {
+		http.Error(w, "Use HTTPS", http.StatusBadRequest)
+		return
+	}
+	target := "https://" + stripPort(r.Host) + r.URL.RequestURI()
+	http.Redirect(w, r, target, http.StatusFound)
+}
+
+func stripPort(hostport string) string {
+	host, _, err := net.SplitHostPort(hostport)
+	if err != nil {
+		return hostport
+	}
+	return net.JoinHostPort(host, "443")
+}
+
 // cert returns an existing certificate either from m.state or cache.
 // If a certificate is found in cache but not in m.state, the latter will be filled
 // with the cached value.
-func (m *Manager) cert(ctx context.Context, name string) (*tls.Certificate, error) {
+func (m *Manager) cert(ctx context.Context, ck certKey) (*tls.Certificate, error) {
 	m.stateMu.Lock()
-	if s, ok := m.state[name]; ok {
+	if s, ok := m.state[ck]; ok {
 		m.stateMu.Unlock()
 		s.RLock()
 		defer s.RUnlock()
 		return s.tlscert()
 	}
 	defer m.stateMu.Unlock()
-	cert, err := m.cacheGet(ctx, name)
+	cert, err := m.cacheGet(ctx, ck)
 	if err != nil {
 		return nil, err
 	}
@@ -245,25 +398,25 @@ func (m *Manager) cert(ctx context.Context, name string) (*tls.Certificate, erro
 		return nil, errors.New("acme/autocert: private key cannot sign")
 	}
 	if m.state == nil {
-		m.state = make(map[string]*certState)
+		m.state = make(map[certKey]*certState)
 	}
 	s := &certState{
 		key:  signer,
 		cert: cert.Certificate,
 		leaf: cert.Leaf,
 	}
-	m.state[name] = s
-	go m.renew(name, s.key, s.leaf.NotAfter)
+	m.state[ck] = s
+	go m.renew(ck, s.key, s.leaf.NotAfter)
 	return cert, nil
 }
 
 // cacheGet always returns a valid certificate, or an error otherwise.
-// If a cached certficate exists but is not valid, ErrCacheMiss is returned.
-func (m *Manager) cacheGet(ctx context.Context, domain string) (*tls.Certificate, error) {
+// If a cached certificate exists but is not valid, ErrCacheMiss is returned.
+func (m *Manager) cacheGet(ctx context.Context, ck certKey) (*tls.Certificate, error) {
 	if m.Cache == nil {
 		return nil, ErrCacheMiss
 	}
-	data, err := m.Cache.Get(ctx, domain)
+	data, err := m.Cache.Get(ctx, ck.String())
 	if err != nil {
 		return nil, err
 	}
@@ -294,7 +447,7 @@ func (m *Manager) cacheGet(ctx context.Context, domain string) (*tls.Certificate
 	}
 
 	// verify and create TLS cert
-	leaf, err := validCert(domain, pubDER, privKey)
+	leaf, err := validCert(ck, pubDER, privKey)
 	if err != nil {
 		return nil, ErrCacheMiss
 	}
@@ -306,7 +459,7 @@ func (m *Manager) cacheGet(ctx context.Context, domain string) (*tls.Certificate
 	return tlscert, nil
 }
 
-func (m *Manager) cachePut(ctx context.Context, domain string, tlscert *tls.Certificate) error {
+func (m *Manager) cachePut(ctx context.Context, ck certKey, tlscert *tls.Certificate) error {
 	if m.Cache == nil {
 		return nil
 	}
@@ -338,7 +491,7 @@ func (m *Manager) cachePut(ctx context.Context, domain string, tlscert *tls.Cert
 		}
 	}
 
-	return m.Cache.Put(ctx, domain, buf.Bytes())
+	return m.Cache.Put(ctx, ck.String(), buf.Bytes())
 }
 
 func encodeECDSAKey(w io.Writer, key *ecdsa.PrivateKey) error {
@@ -355,9 +508,9 @@ func encodeECDSAKey(w io.Writer, key *ecdsa.PrivateKey) error {
 //
 // If the domain is already being verified, it waits for the existing verification to complete.
 // Either way, createCert blocks for the duration of the whole process.
-func (m *Manager) createCert(ctx context.Context, domain string) (*tls.Certificate, error) {
+func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate, error) {
 	// TODO: maybe rewrite this whole piece using sync.Once
-	state, err := m.certState(domain)
+	state, err := m.certState(ck)
 	if err != nil {
 		return nil, err
 	}
@@ -371,48 +524,48 @@ func (m *Manager) createCert(ctx context.Context, domain string) (*tls.Certifica
 
 	// We are the first; state is locked.
 	// Unblock the readers when domain ownership is verified
-	// and the we got the cert or the process failed.
+	// and we got the cert or the process failed.
 	defer state.Unlock()
 	state.locked = false
 
-	der, leaf, err := m.authorizedCert(ctx, state.key, domain)
+	der, leaf, err := m.authorizedCert(ctx, state.key, ck)
 	if err != nil {
 		// Remove the failed state after some time,
 		// making the manager call createCert again on the following TLS hello.
 		time.AfterFunc(createCertRetryAfter, func() {
-			defer testDidRemoveState(domain)
+			defer testDidRemoveState(ck)
 			m.stateMu.Lock()
 			defer m.stateMu.Unlock()
 			// Verify the state hasn't changed and it's still invalid
 			// before deleting.
-			s, ok := m.state[domain]
+			s, ok := m.state[ck]
 			if !ok {
 				return
 			}
-			if _, err := validCert(domain, s.cert, s.key); err == nil {
+			if _, err := validCert(ck, s.cert, s.key); err == nil {
 				return
 			}
-			delete(m.state, domain)
+			delete(m.state, ck)
 		})
 		return nil, err
 	}
 	state.cert = der
 	state.leaf = leaf
-	go m.renew(domain, state.key, state.leaf.NotAfter)
+	go m.renew(ck, state.key, state.leaf.NotAfter)
 	return state.tlscert()
 }
 
 // certState returns a new or existing certState.
 // If a new certState is returned, state.exist is false and the state is locked.
 // The returned error is non-nil only in the case where a new state could not be created.
-func (m *Manager) certState(domain string) (*certState, error) {
+func (m *Manager) certState(ck certKey) (*certState, error) {
 	m.stateMu.Lock()
 	defer m.stateMu.Unlock()
 	if m.state == nil {
-		m.state = make(map[string]*certState)
+		m.state = make(map[certKey]*certState)
 	}
 	// existing state
-	if state, ok := m.state[domain]; ok {
+	if state, ok := m.state[ck]; ok {
 		return state, nil
 	}
 
@@ -421,7 +574,7 @@ func (m *Manager) certState(domain string) (*certState, error) {
 		err error
 		key crypto.Signer
 	)
-	if m.ForceRSA {
+	if ck.isRSA {
 		key, err = rsa.GenerateKey(rand.Reader, 2048)
 	} else {
 		key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
@@ -435,21 +588,22 @@ func (m *Manager) certState(domain string) (*certState, error) {
 		locked: true,
 	}
 	state.Lock() // will be unlocked by m.certState caller
-	m.state[domain] = state
+	m.state[ck] = state
 	return state, nil
 }
 
-// authorizedCert starts domain ownership verification process and requests a new cert upon success.
+// authorizedCert starts the domain ownership verification process and requests a new cert upon success.
 // The key argument is the certificate private key.
-func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, domain string) (der [][]byte, leaf *x509.Certificate, err error) {
-	if err := m.verify(ctx, domain); err != nil {
-		return nil, nil, err
-	}
+func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, ck certKey) (der [][]byte, leaf *x509.Certificate, err error) {
 	client, err := m.acmeClient(ctx)
 	if err != nil {
 		return nil, nil, err
 	}
-	csr, err := certRequest(key, domain)
+
+	if err := m.verify(ctx, client, ck.domain); err != nil {
+		return nil, nil, err
+	}
+	csr, err := certRequest(key, ck.domain, m.ExtraExtensions)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -457,105 +611,220 @@ func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, domain
 	if err != nil {
 		return nil, nil, err
 	}
-	leaf, err = validCert(domain, der, key)
+	leaf, err = validCert(ck, der, key)
 	if err != nil {
 		return nil, nil, err
 	}
 	return der, leaf, nil
 }
 
-// verify starts a new identifier (domain) authorization flow.
-// It prepares a challenge response and then blocks until the authorization
-// is marked as "completed" by the CA (either succeeded or failed).
-//
-// verify returns nil iff the verification was successful.
-func (m *Manager) verify(ctx context.Context, domain string) error {
+// revokePendingAuthz revokes all authorizations idenfied by the elements of uri slice.
+// It ignores revocation errors.
+func (m *Manager) revokePendingAuthz(ctx context.Context, uri []string) {
 	client, err := m.acmeClient(ctx)
 	if err != nil {
-		return err
+		return
 	}
-
-	// start domain authorization and get the challenge
-	authz, err := client.Authorize(ctx, domain)
-	if err != nil {
-		return err
+	for _, u := range uri {
+		client.RevokeAuthorization(ctx, u)
 	}
-	// maybe don't need to at all
-	if authz.Status == acme.StatusValid {
-		return nil
+}
+
+// verify runs the identifier (domain) authorization flow
+// using each applicable ACME challenge type.
+func (m *Manager) verify(ctx context.Context, client *acme.Client, domain string) error {
+	// The list of challenge types we'll try to fulfill
+	// in this specific order.
+	challengeTypes := []string{"tls-sni-02", "tls-sni-01"}
+	m.tokensMu.RLock()
+	if m.tryHTTP01 {
+		challengeTypes = append(challengeTypes, "http-01")
 	}
+	m.tokensMu.RUnlock()
 
-	// pick a challenge: prefer tls-sni-02 over tls-sni-01
-	// TODO: consider authz.Combinations
-	var chal *acme.Challenge
-	for _, c := range authz.Challenges {
-		if c.Type == "tls-sni-02" {
-			chal = c
-			break
+	// Keep track of pending authzs and revoke the ones that did not validate.
+	pendingAuthzs := make(map[string]bool)
+	defer func() {
+		var uri []string
+		for k, pending := range pendingAuthzs {
+			if pending {
+				uri = append(uri, k)
+			}
 		}
-		if c.Type == "tls-sni-01" {
-			chal = c
+		if len(uri) > 0 {
+			// Use "detached" background context.
+			// The revocations need not happen in the current verification flow.
+			go m.revokePendingAuthz(context.Background(), uri)
 		}
+	}()
+
+	// errs accumulates challenge failure errors, printed if all fail
+	errs := make(map[*acme.Challenge]error)
+	var nextTyp int // challengeType index of the next challenge type to try
+	for {
+		// Start domain authorization and get the challenge.
+		authz, err := client.Authorize(ctx, domain)
+		if err != nil {
+			return err
+		}
+		// No point in accepting challenges if the authorization status
+		// is in a final state.
+		switch authz.Status {
+		case acme.StatusValid:
+			return nil // already authorized
+		case acme.StatusInvalid:
+			return fmt.Errorf("acme/autocert: invalid authorization %q", authz.URI)
+		}
+
+		pendingAuthzs[authz.URI] = true
+
+		// Pick the next preferred challenge.
+		var chal *acme.Challenge
+		for chal == nil && nextTyp < len(challengeTypes) {
+			chal = pickChallenge(challengeTypes[nextTyp], authz.Challenges)
+			nextTyp++
+		}
+		if chal == nil {
+			errorMsg := fmt.Sprintf("acme/autocert: unable to authorize %q", domain)
+			for chal, err := range errs {
+				errorMsg += fmt.Sprintf("; challenge %q failed with error: %v", chal.Type, err)
+			}
+			return errors.New(errorMsg)
+		}
+		cleanup, err := m.fulfill(ctx, client, chal)
+		if err != nil {
+			errs[chal] = err
+			continue
+		}
+		defer cleanup()
+		if _, err := client.Accept(ctx, chal); err != nil {
+			errs[chal] = err
+			continue
+		}
+
+		// A challenge is fulfilled and accepted: wait for the CA to validate.
+		if _, err := client.WaitAuthorization(ctx, authz.URI); err != nil {
+			errs[chal] = err
+			continue
+		}
+		delete(pendingAuthzs, authz.URI)
+		return nil
 	}
-	if chal == nil {
-		return errors.New("acme/autocert: no supported challenge type found")
-	}
+}
 
-	// create a token cert for the challenge response
-	var (
-		cert tls.Certificate
-		name string
-	)
+// fulfill provisions a response to the challenge chal.
+// The cleanup is non-nil only if provisioning succeeded.
+func (m *Manager) fulfill(ctx context.Context, client *acme.Client, chal *acme.Challenge) (cleanup func(), err error) {
 	switch chal.Type {
 	case "tls-sni-01":
-		cert, name, err = client.TLSSNI01ChallengeCert(chal.Token)
+		cert, name, err := client.TLSSNI01ChallengeCert(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		m.putCertToken(ctx, name, &cert)
+		return func() { go m.deleteCertToken(name) }, nil
 	case "tls-sni-02":
-		cert, name, err = client.TLSSNI02ChallengeCert(chal.Token)
-	default:
-		err = fmt.Errorf("acme/autocert: unknown challenge type %q", chal.Type)
+		cert, name, err := client.TLSSNI02ChallengeCert(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		m.putCertToken(ctx, name, &cert)
+		return func() { go m.deleteCertToken(name) }, nil
+	case "http-01":
+		resp, err := client.HTTP01ChallengeResponse(chal.Token)
+		if err != nil {
+			return nil, err
+		}
+		p := client.HTTP01ChallengePath(chal.Token)
+		m.putHTTPToken(ctx, p, resp)
+		return func() { go m.deleteHTTPToken(p) }, nil
 	}
-	if err != nil {
-		return err
+	return nil, fmt.Errorf("acme/autocert: unknown challenge type %q", chal.Type)
+}
+
+func pickChallenge(typ string, chal []*acme.Challenge) *acme.Challenge {
+	for _, c := range chal {
+		if c.Type == typ {
+			return c
+		}
 	}
-	m.putTokenCert(ctx, name, &cert)
-	defer func() {
-		// verification has ended at this point
-		// don't need token cert anymore
-		go m.deleteTokenCert(name)
-	}()
+	return nil
+}
 
-	// ready to fulfill the challenge
-	if _, err := client.Accept(ctx, chal); err != nil {
-		return err
+// putCertToken stores the token certificate with the specified name
+// in both m.certTokens map and m.Cache.
+func (m *Manager) putCertToken(ctx context.Context, name string, cert *tls.Certificate) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	if m.certTokens == nil {
+		m.certTokens = make(map[string]*tls.Certificate)
+	}
+	m.certTokens[name] = cert
+	m.cachePut(ctx, certKey{domain: name, isToken: true}, cert)
+}
+
+// deleteCertToken removes the token certificate with the specified name
+// from both m.certTokens map and m.Cache.
+func (m *Manager) deleteCertToken(name string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	delete(m.certTokens, name)
+	if m.Cache != nil {
+		ck := certKey{domain: name, isToken: true}
+		m.Cache.Delete(context.Background(), ck.String())
+	}
+}
+
+// httpToken retrieves an existing http-01 token value from an in-memory map
+// or the optional cache.
+func (m *Manager) httpToken(ctx context.Context, tokenPath string) ([]byte, error) {
+	m.tokensMu.RLock()
+	defer m.tokensMu.RUnlock()
+	if v, ok := m.httpTokens[tokenPath]; ok {
+		return v, nil
+	}
+	if m.Cache == nil {
+		return nil, fmt.Errorf("acme/autocert: no token at %q", tokenPath)
 	}
-	// wait for the CA to validate
-	_, err = client.WaitAuthorization(ctx, authz.URI)
-	return err
+	return m.Cache.Get(ctx, httpTokenCacheKey(tokenPath))
 }
 
-// putTokenCert stores the cert under the named key in both m.tokenCert map
-// and m.Cache.
-func (m *Manager) putTokenCert(ctx context.Context, name string, cert *tls.Certificate) {
-	m.tokenCertMu.Lock()
-	defer m.tokenCertMu.Unlock()
-	if m.tokenCert == nil {
-		m.tokenCert = make(map[string]*tls.Certificate)
+// putHTTPToken stores an http-01 token value using tokenPath as key
+// in both in-memory map and the optional Cache.
+//
+// It ignores any error returned from Cache.Put.
+func (m *Manager) putHTTPToken(ctx context.Context, tokenPath, val string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	if m.httpTokens == nil {
+		m.httpTokens = make(map[string][]byte)
+	}
+	b := []byte(val)
+	m.httpTokens[tokenPath] = b
+	if m.Cache != nil {
+		m.Cache.Put(ctx, httpTokenCacheKey(tokenPath), b)
 	}
-	m.tokenCert[name] = cert
-	m.cachePut(ctx, name, cert)
 }
 
-// deleteTokenCert removes the token certificate for the specified domain name
-// from both m.tokenCert map and m.Cache.
-func (m *Manager) deleteTokenCert(name string) {
-	m.tokenCertMu.Lock()
-	defer m.tokenCertMu.Unlock()
-	delete(m.tokenCert, name)
+// deleteHTTPToken removes an http-01 token value from both in-memory map
+// and the optional Cache, ignoring any error returned from the latter.
+//
+// If m.Cache is non-nil, it blocks until Cache.Delete returns without a timeout.
+func (m *Manager) deleteHTTPToken(tokenPath string) {
+	m.tokensMu.Lock()
+	defer m.tokensMu.Unlock()
+	delete(m.httpTokens, tokenPath)
 	if m.Cache != nil {
-		m.Cache.Delete(context.Background(), name)
+		m.Cache.Delete(context.Background(), httpTokenCacheKey(tokenPath))
 	}
 }
 
+// httpTokenCacheKey returns a key at which an http-01 token value may be stored
+// in the Manager's optional Cache.
+func httpTokenCacheKey(tokenPath string) string {
+	return path.Base(tokenPath) + "+http-01"
+}
+
 // renew starts a cert renewal timer loop, one per domain.
 //
 // The loop is scheduled in two cases:
@@ -564,18 +833,18 @@ func (m *Manager) deleteTokenCert(name string) {
 //
 // The key argument is a certificate private key.
 // The exp argument is the cert expiration time (NotAfter).
-func (m *Manager) renew(domain string, key crypto.Signer, exp time.Time) {
+func (m *Manager) renew(ck certKey, key crypto.Signer, exp time.Time) {
 	m.renewalMu.Lock()
 	defer m.renewalMu.Unlock()
-	if m.renewal[domain] != nil {
+	if m.renewal[ck] != nil {
 		// another goroutine is already on it
 		return
 	}
 	if m.renewal == nil {
-		m.renewal = make(map[string]*domainRenewal)
+		m.renewal = make(map[certKey]*domainRenewal)
 	}
-	dr := &domainRenewal{m: m, domain: domain, key: key}
-	m.renewal[domain] = dr
+	dr := &domainRenewal{m: m, ck: ck, key: key}
+	m.renewal[ck] = dr
 	dr.start(exp)
 }
 
@@ -591,7 +860,10 @@ func (m *Manager) stopRenew() {
 }
 
 func (m *Manager) accountKey(ctx context.Context) (crypto.Signer, error) {
-	const keyName = "acme_account.key"
+	const keyName = "acme_account+key"
+
+	// Previous versions of autocert stored the value under a different key.
+	const legacyKeyName = "acme_account.key"
 
 	genKey := func() (*ecdsa.PrivateKey, error) {
 		return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
@@ -603,6 +875,9 @@ func (m *Manager) accountKey(ctx context.Context) (crypto.Signer, error) {
 
 	data, err := m.Cache.Get(ctx, keyName)
 	if err == ErrCacheMiss {
+		data, err = m.Cache.Get(ctx, legacyKeyName)
+	}
+	if err == ErrCacheMiss {
 		key, err := genKey()
 		if err != nil {
 			return nil, err
@@ -698,12 +973,12 @@ func (s *certState) tlscert() (*tls.Certificate, error) {
 	}, nil
 }
 
-// certRequest creates a certificate request for the given common name cn
-// and optional SANs.
-func certRequest(key crypto.Signer, cn string, san ...string) ([]byte, error) {
+// certRequest generates a CSR for the given common name cn and optional SANs.
+func certRequest(key crypto.Signer, cn string, ext []pkix.Extension, san ...string) ([]byte, error) {
 	req := &x509.CertificateRequest{
-		Subject:  pkix.Name{CommonName: cn},
-		DNSNames: san,
+		Subject:         pkix.Name{CommonName: cn},
+		DNSNames:        san,
+		ExtraExtensions: ext,
 	}
 	return x509.CreateCertificateRequest(rand.Reader, req, key)
 }
@@ -734,12 +1009,12 @@ func parsePrivateKey(der []byte) (crypto.Signer, error) {
 	return nil, errors.New("acme/autocert: failed to parse private key")
 }
 
-// validCert parses a cert chain provided as der argument and verifies the leaf, der[0],
-// corresponds to the private key, as well as the domain match and expiration dates.
-// It doesn't do any revocation checking.
+// validCert parses a cert chain provided as der argument and verifies the leaf and der[0]
+// correspond to the private key, the domain and key type match, and expiration dates
+// are valid. It doesn't do any revocation checking.
 //
 // The returned value is the verified leaf cert.
-func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certificate, err error) {
+func validCert(ck certKey, der [][]byte, key crypto.Signer) (leaf *x509.Certificate, err error) {
 	// parse public part(s)
 	var n int
 	for _, b := range der {
@@ -751,7 +1026,7 @@ func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certi
 		n += copy(pub[n:], b)
 	}
 	x509Cert, err := x509.ParseCertificates(pub)
-	if len(x509Cert) == 0 {
+	if err != nil || len(x509Cert) == 0 {
 		return nil, errors.New("acme/autocert: no public key found")
 	}
 	// verify the leaf is not expired and matches the domain name
@@ -763,10 +1038,10 @@ func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certi
 	if now.After(leaf.NotAfter) {
 		return nil, errors.New("acme/autocert: expired certificate")
 	}
-	if err := leaf.VerifyHostname(domain); err != nil {
+	if err := leaf.VerifyHostname(ck.domain); err != nil {
 		return nil, err
 	}
-	// ensure the leaf corresponds to the private key
+	// ensure the leaf corresponds to the private key and matches the certKey type
 	switch pub := leaf.PublicKey.(type) {
 	case *rsa.PublicKey:
 		prv, ok := key.(*rsa.PrivateKey)
@@ -776,6 +1051,9 @@ func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certi
 		if pub.N.Cmp(prv.N) != 0 {
 			return nil, errors.New("acme/autocert: private key does not match public key")
 		}
+		if !ck.isRSA && !ck.isToken {
+			return nil, errors.New("acme/autocert: key type does not match expected value")
+		}
 	case *ecdsa.PublicKey:
 		prv, ok := key.(*ecdsa.PrivateKey)
 		if !ok {
@@ -784,22 +1062,15 @@ func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certi
 		if pub.X.Cmp(prv.X) != 0 || pub.Y.Cmp(prv.Y) != 0 {
 			return nil, errors.New("acme/autocert: private key does not match public key")
 		}
+		if ck.isRSA && !ck.isToken {
+			return nil, errors.New("acme/autocert: key type does not match expected value")
+		}
 	default:
 		return nil, errors.New("acme/autocert: unknown public key algorithm")
 	}
 	return leaf, nil
 }
 
-func retryAfter(v string) time.Duration {
-	if i, err := strconv.Atoi(v); err == nil {
-		return time.Duration(i) * time.Second
-	}
-	if t, err := http.ParseTime(v); err == nil {
-		return t.Sub(timeNow())
-	}
-	return time.Second
-}
-
 type lockedMathRand struct {
 	sync.Mutex
 	rnd *mathrand.Rand
@@ -817,5 +1088,5 @@ var (
 	timeNow = time.Now
 
 	// Called when a state is removed.
-	testDidRemoveState = func(domain string) {}
+	testDidRemoveState = func(certKey) {}
 )
diff --git a/vendor/golang.org/x/crypto/acme/autocert/cache.go b/vendor/golang.org/x/crypto/acme/autocert/cache.go
index 61a5fd2..aa9aa84 100644
--- a/vendor/golang.org/x/crypto/acme/autocert/cache.go
+++ b/vendor/golang.org/x/crypto/acme/autocert/cache.go
@@ -16,10 +16,10 @@ import (
 var ErrCacheMiss = errors.New("acme/autocert: certificate cache miss")
 
 // Cache is used by Manager to store and retrieve previously obtained certificates
-// as opaque data.
+// and other account data as opaque blobs.
 //
-// The key argument of the methods refers to a domain name but need not be an FQDN.
-// Cache implementations should not rely on the key naming pattern.
+// Cache implementations should not rely on the key naming pattern. Keys can
+// include any printable ASCII characters, except the following: \/:*?"<>|
 type Cache interface {
 	// Get returns a certificate data for the specified key.
 	// If there's no such key, Get returns ErrCacheMiss.
diff --git a/vendor/golang.org/x/crypto/acme/autocert/renewal.go b/vendor/golang.org/x/crypto/acme/autocert/renewal.go
index 6c5da2b..ef3e44e 100644
--- a/vendor/golang.org/x/crypto/acme/autocert/renewal.go
+++ b/vendor/golang.org/x/crypto/acme/autocert/renewal.go
@@ -17,9 +17,9 @@ const renewJitter = time.Hour
 // domainRenewal tracks the state used by the periodic timers
 // renewing a single domain's cert.
 type domainRenewal struct {
-	m      *Manager
-	domain string
-	key    crypto.Signer
+	m   *Manager
+	ck  certKey
+	key crypto.Signer
 
 	timerMu sync.Mutex
 	timer   *time.Timer
@@ -71,25 +71,43 @@ func (dr *domainRenewal) renew() {
 	testDidRenewLoop(next, err)
 }
 
+// updateState locks and replaces the relevant Manager.state item with the given
+// state. It additionally updates dr.key with the given state's key.
+func (dr *domainRenewal) updateState(state *certState) {
+	dr.m.stateMu.Lock()
+	defer dr.m.stateMu.Unlock()
+	dr.key = state.key
+	dr.m.state[dr.ck] = state
+}
+
 // do is similar to Manager.createCert but it doesn't lock a Manager.state item.
 // Instead, it requests a new certificate independently and, upon success,
 // replaces dr.m.state item with a new one and updates cache for the given domain.
 //
-// It may return immediately if the expiration date of the currently cached cert
-// is far enough in the future.
+// It may lock and update the Manager.state if the expiration date of the currently
+// cached cert is far enough in the future.
 //
 // The returned value is a time interval after which the renewal should occur again.
 func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
 	// a race is likely unavoidable in a distributed environment
 	// but we try nonetheless
-	if tlscert, err := dr.m.cacheGet(ctx, dr.domain); err == nil {
+	if tlscert, err := dr.m.cacheGet(ctx, dr.ck); err == nil {
 		next := dr.next(tlscert.Leaf.NotAfter)
 		if next > dr.m.renewBefore()+renewJitter {
-			return next, nil
+			signer, ok := tlscert.PrivateKey.(crypto.Signer)
+			if ok {
+				state := &certState{
+					key:  signer,
+					cert: tlscert.Certificate,
+					leaf: tlscert.Leaf,
+				}
+				dr.updateState(state)
+				return next, nil
+			}
 		}
 	}
 
-	der, leaf, err := dr.m.authorizedCert(ctx, dr.key, dr.domain)
+	der, leaf, err := dr.m.authorizedCert(ctx, dr.key, dr.ck)
 	if err != nil {
 		return 0, err
 	}
@@ -102,11 +120,10 @@ func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
 	if err != nil {
 		return 0, err
 	}
-	dr.m.cachePut(ctx, dr.domain, tlscert)
-	dr.m.stateMu.Lock()
-	defer dr.m.stateMu.Unlock()
-	// m.state is guaranteed to be non-nil at this point
-	dr.m.state[dr.domain] = state
+	if err := dr.m.cachePut(ctx, dr.ck, tlscert); err != nil {
+		return 0, err
+	}
+	dr.updateState(state)
 	return dr.next(leaf.NotAfter), nil
 }
 
diff --git a/vendor/golang.org/x/crypto/acme/http.go b/vendor/golang.org/x/crypto/acme/http.go
new file mode 100644
index 0000000..56ba53a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/acme/http.go
@@ -0,0 +1,276 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package acme
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"math/big"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// retryTimer encapsulates common logic for retrying unsuccessful requests.
+// It is not safe for concurrent use.
+type retryTimer struct {
+	// backoffFn provides backoff delay sequence for retries.
+	// See Client.RetryBackoff doc comment.
+	backoffFn func(n int, r *http.Request, res *http.Response) time.Duration
+	// n is the current retry attempt.
+	n int
+}
+
+func (t *retryTimer) inc() {
+	t.n++
+}
+
+// backoff pauses the current goroutine as described in Client.RetryBackoff.
+func (t *retryTimer) backoff(ctx context.Context, r *http.Request, res *http.Response) error {
+	d := t.backoffFn(t.n, r, res)
+	if d <= 0 {
+		return fmt.Errorf("acme: no more retries for %s; tried %d time(s)", r.URL, t.n)
+	}
+	wakeup := time.NewTimer(d)
+	defer wakeup.Stop()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-wakeup.C:
+		return nil
+	}
+}
+
+func (c *Client) retryTimer() *retryTimer {
+	f := c.RetryBackoff
+	if f == nil {
+		f = defaultBackoff
+	}
+	return &retryTimer{backoffFn: f}
+}
+
+// defaultBackoff provides default Client.RetryBackoff implementation
+// using a truncated exponential backoff algorithm,
+// as described in Client.RetryBackoff.
+//
+// The n argument is always bounded between 1 and 30.
+// The returned value is always greater than 0.
+func defaultBackoff(n int, r *http.Request, res *http.Response) time.Duration {
+	const max = 10 * time.Second
+	var jitter time.Duration
+	if x, err := rand.Int(rand.Reader, big.NewInt(1000)); err == nil {
+		// Set the minimum to 1ms to avoid a case where
+		// an invalid Retry-After value is parsed into 0 below,
+		// resulting in the 0 returned value which would unintentionally
+		// stop the retries.
+		jitter = (1 + time.Duration(x.Int64())) * time.Millisecond
+	}
+	if v, ok := res.Header["Retry-After"]; ok {
+		return retryAfter(v[0]) + jitter
+	}
+
+	if n < 1 {
+		n = 1
+	}
+	if n > 30 {
+		n = 30
+	}
+	d := time.Duration(1<<uint(n-1))*time.Second + jitter
+	if d > max {
+		return max
+	}
+	return d
+}
+
+// retryAfter parses a Retry-After HTTP header value,
+// trying to convert v into an int (seconds) or use http.ParseTime otherwise.
+// It returns zero value if v cannot be parsed.
+func retryAfter(v string) time.Duration {
+	if i, err := strconv.Atoi(v); err == nil {
+		return time.Duration(i) * time.Second
+	}
+	t, err := http.ParseTime(v)
+	if err != nil {
+		return 0
+	}
+	return t.Sub(timeNow())
+}
+
+// resOkay is a function that reports whether the provided response is okay.
+// It is expected to keep the response body unread.
+type resOkay func(*http.Response) bool
+
+// wantStatus returns a function which reports whether the code
+// matches the status code of a response.
+func wantStatus(codes ...int) resOkay {
+	return func(res *http.Response) bool {
+		for _, code := range codes {
+			if code == res.StatusCode {
+				return true
+			}
+		}
+		return false
+	}
+}
+
+// get issues an unsigned GET request to the specified URL.
+// It returns a non-error value only when ok reports true.
+//
+// get retries unsuccessful attempts according to c.RetryBackoff
+// until the context is done or a non-retriable error is received.
+func (c *Client) get(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
+	retry := c.retryTimer()
+	for {
+		req, err := http.NewRequest("GET", url, nil)
+		if err != nil {
+			return nil, err
+		}
+		res, err := c.doNoRetry(ctx, req)
+		switch {
+		case err != nil:
+			return nil, err
+		case ok(res):
+			return res, nil
+		case isRetriable(res.StatusCode):
+			res.Body.Close()
+			retry.inc()
+			if err := retry.backoff(ctx, req, res); err != nil {
+				return nil, err
+			}
+		default:
+			defer res.Body.Close()
+			return nil, responseError(res)
+		}
+	}
+}
+
+// post issues a signed POST request in JWS format using the provided key
+// to the specified URL.
+// It returns a non-error value only when ok reports true.
+//
+// post retries unsuccessful attempts according to c.RetryBackoff
+// until the context is done or a non-retriable error is received.
+// It uses postNoRetry to make individual requests.
+func (c *Client) post(ctx context.Context, key crypto.Signer, url string, body interface{}, ok resOkay) (*http.Response, error) {
+	retry := c.retryTimer()
+	for {
+		res, req, err := c.postNoRetry(ctx, key, url, body)
+		if err != nil {
+			return nil, err
+		}
+		if ok(res) {
+			return res, nil
+		}
+		err = responseError(res)
+		res.Body.Close()
+		switch {
+		// Check for bad nonce before isRetriable because it may have been returned
+		// with an unretriable response code such as 400 Bad Request.
+		case isBadNonce(err):
+			// Consider any previously stored nonce values to be invalid.
+			c.clearNonces()
+		case !isRetriable(res.StatusCode):
+			return nil, err
+		}
+		retry.inc()
+		if err := retry.backoff(ctx, req, res); err != nil {
+			return nil, err
+		}
+	}
+}
+
+// postNoRetry signs the body with the given key and POSTs it to the provided url.
+// The body argument must be JSON-serializable.
+// It is used by c.post to retry unsuccessful attempts.
+func (c *Client) postNoRetry(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, *http.Request, error) {
+	nonce, err := c.popNonce(ctx, url)
+	if err != nil {
+		return nil, nil, err
+	}
+	b, err := jwsEncodeJSON(body, key, nonce)
+	if err != nil {
+		return nil, nil, err
+	}
+	req, err := http.NewRequest("POST", url, bytes.NewReader(b))
+	if err != nil {
+		return nil, nil, err
+	}
+	req.Header.Set("Content-Type", "application/jose+json")
+	res, err := c.doNoRetry(ctx, req)
+	if err != nil {
+		return nil, nil, err
+	}
+	c.addNonce(res.Header)
+	return res, req, nil
+}
+
+// doNoRetry issues a request req, replacing its context (if any) with ctx.
+func (c *Client) doNoRetry(ctx context.Context, req *http.Request) (*http.Response, error) {
+	res, err := c.httpClient().Do(req.WithContext(ctx))
+	if err != nil {
+		select {
+		case <-ctx.Done():
+			// Prefer the unadorned context error.
+			// (The acme package had tests assuming this, previously from ctxhttp's
+			// behavior, predating net/http supporting contexts natively)
+			// TODO(bradfitz): reconsider this in the future. But for now this
+			// requires no test updates.
+			return nil, ctx.Err()
+		default:
+			return nil, err
+		}
+	}
+	return res, nil
+}
+
+func (c *Client) httpClient() *http.Client {
+	if c.HTTPClient != nil {
+		return c.HTTPClient
+	}
+	return http.DefaultClient
+}
+
+// isBadNonce reports whether err is an ACME "badnonce" error.
+func isBadNonce(err error) bool {
+	// According to the spec badNonce is urn:ietf:params:acme:error:badNonce.
+	// However, ACME servers in the wild return their versions of the error.
+	// See https://tools.ietf.org/html/draft-ietf-acme-acme-02#section-5.4
+	// and https://github.com/letsencrypt/boulder/blob/0e07eacb/docs/acme-divergences.md#section-66.
+	ae, ok := err.(*Error)
+	return ok && strings.HasSuffix(strings.ToLower(ae.ProblemType), ":badnonce")
+}
+
+// isRetriable reports whether a request can be retried
+// based on the response status code.
+//
+// Note that a "bad nonce" error is returned with a non-retriable 400 Bad Request code.
+// Callers should parse the response and check with isBadNonce.
+func isRetriable(code int) bool {
+	return code <= 399 || code >= 500 || code == http.StatusTooManyRequests
+}
+
+// responseError creates an error of Error type from resp.
+func responseError(resp *http.Response) error {
+	// don't care if ReadAll returns an error:
+	// json.Unmarshal will fail in that case anyway
+	b, _ := ioutil.ReadAll(resp.Body)
+	e := &wireError{Status: resp.StatusCode}
+	if err := json.Unmarshal(b, e); err != nil {
+		// this is not a regular error response:
+		// populate detail with anything we received,
+		// e.Status will already contain HTTP response code value
+		e.Detail = string(b)
+		if e.Detail == "" {
+			e.Detail = resp.Status
+		}
+	}
+	return e.error(resp.Header)
+}
diff --git a/vendor/golang.org/x/crypto/acme/types.go b/vendor/golang.org/x/crypto/acme/types.go
index 3e19974..54792c0 100644
--- a/vendor/golang.org/x/crypto/acme/types.go
+++ b/vendor/golang.org/x/crypto/acme/types.go
@@ -104,7 +104,7 @@ func RateLimit(err error) (time.Duration, bool) {
 	if e.Header == nil {
 		return 0, true
 	}
-	return retryAfter(e.Header.Get("Retry-After"), 0), true
+	return retryAfter(e.Header.Get("Retry-After")), true
 }
 
 // Account is a user account. It is associated with a private key.
@@ -296,8 +296,8 @@ func (e *wireError) error(h http.Header) *Error {
 	}
 }
 
-// CertOption is an optional argument type for the TLSSNIxChallengeCert methods for
-// customizing a temporary certificate for TLS-SNI challenges.
+// CertOption is an optional argument type for the TLS ChallengeCert methods for
+// customizing a temporary certificate for TLS-based challenges.
 type CertOption interface {
 	privateCertOpt()
 }
@@ -317,7 +317,7 @@ func (*certOptKey) privateCertOpt() {}
 // WithTemplate creates an option for specifying a certificate template.
 // See x509.CreateCertificate for template usage details.
 //
-// In TLSSNIxChallengeCert methods, the template is also used as parent,
+// In TLS ChallengeCert methods, the template is also used as parent,
 // resulting in a self-signed certificate.
 // The DNSNames field of t is always overwritten for tls-sni challenge certs.
 func WithTemplate(t *x509.Certificate) CertOption {
diff --git a/vendor/golang.org/x/crypto/curve25519/curve25519.go b/vendor/golang.org/x/crypto/curve25519/curve25519.go
new file mode 100644
index 0000000..cb8fbc5
--- /dev/null
+++ b/vendor/golang.org/x/crypto/curve25519/curve25519.go
@@ -0,0 +1,834 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// We have an implementation in amd64 assembly so this code is only run on
+// non-amd64 platforms. The amd64 assembly does not support gccgo.
+// +build !amd64 gccgo appengine
+
+package curve25519
+
+import (
+	"encoding/binary"
+)
+
+// This code is a port of the public domain, "ref10" implementation of
+// curve25519 from SUPERCOP 20130419 by D. J. Bernstein.
+
+// fieldElement represents an element of the field GF(2^255 - 19). An element
+// t, entries t[0]...t[9], represents the integer t[0]+2^26 t[1]+2^51 t[2]+2^77
+// t[3]+2^102 t[4]+...+2^230 t[9]. Bounds on each t[i] vary depending on
+// context.
+type fieldElement [10]int32
+
+func feZero(fe *fieldElement) {
+	for i := range fe {
+		fe[i] = 0
+	}
+}
+
+func feOne(fe *fieldElement) {
+	feZero(fe)
+	fe[0] = 1
+}
+
+func feAdd(dst, a, b *fieldElement) {
+	for i := range dst {
+		dst[i] = a[i] + b[i]
+	}
+}
+
+func feSub(dst, a, b *fieldElement) {
+	for i := range dst {
+		dst[i] = a[i] - b[i]
+	}
+}
+
+func feCopy(dst, src *fieldElement) {
+	for i := range dst {
+		dst[i] = src[i]
+	}
+}
+
+// feCSwap replaces (f,g) with (g,f) if b == 1; replaces (f,g) with (f,g) if b == 0.
+//
+// Preconditions: b in {0,1}.
+func feCSwap(f, g *fieldElement, b int32) {
+	b = -b
+	for i := range f {
+		t := b & (f[i] ^ g[i])
+		f[i] ^= t
+		g[i] ^= t
+	}
+}
+
+// load3 reads a 24-bit, little-endian value from in.
+func load3(in []byte) int64 {
+	var r int64
+	r = int64(in[0])
+	r |= int64(in[1]) << 8
+	r |= int64(in[2]) << 16
+	return r
+}
+
+// load4 reads a 32-bit, little-endian value from in.
+func load4(in []byte) int64 {
+	return int64(binary.LittleEndian.Uint32(in))
+}
+
+func feFromBytes(dst *fieldElement, src *[32]byte) {
+	h0 := load4(src[:])
+	h1 := load3(src[4:]) << 6
+	h2 := load3(src[7:]) << 5
+	h3 := load3(src[10:]) << 3
+	h4 := load3(src[13:]) << 2
+	h5 := load4(src[16:])
+	h6 := load3(src[20:]) << 7
+	h7 := load3(src[23:]) << 5
+	h8 := load3(src[26:]) << 4
+	h9 := load3(src[29:]) << 2
+
+	var carry [10]int64
+	carry[9] = (h9 + 1<<24) >> 25
+	h0 += carry[9] * 19
+	h9 -= carry[9] << 25
+	carry[1] = (h1 + 1<<24) >> 25
+	h2 += carry[1]
+	h1 -= carry[1] << 25
+	carry[3] = (h3 + 1<<24) >> 25
+	h4 += carry[3]
+	h3 -= carry[3] << 25
+	carry[5] = (h5 + 1<<24) >> 25
+	h6 += carry[5]
+	h5 -= carry[5] << 25
+	carry[7] = (h7 + 1<<24) >> 25
+	h8 += carry[7]
+	h7 -= carry[7] << 25
+
+	carry[0] = (h0 + 1<<25) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+	carry[2] = (h2 + 1<<25) >> 26
+	h3 += carry[2]
+	h2 -= carry[2] << 26
+	carry[4] = (h4 + 1<<25) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+	carry[6] = (h6 + 1<<25) >> 26
+	h7 += carry[6]
+	h6 -= carry[6] << 26
+	carry[8] = (h8 + 1<<25) >> 26
+	h9 += carry[8]
+	h8 -= carry[8] << 26
+
+	dst[0] = int32(h0)
+	dst[1] = int32(h1)
+	dst[2] = int32(h2)
+	dst[3] = int32(h3)
+	dst[4] = int32(h4)
+	dst[5] = int32(h5)
+	dst[6] = int32(h6)
+	dst[7] = int32(h7)
+	dst[8] = int32(h8)
+	dst[9] = int32(h9)
+}
+
+// feToBytes marshals h to s.
+// Preconditions:
+//   |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+//
+// Write p=2^255-19; q=floor(h/p).
+// Basic claim: q = floor(2^(-255)(h + 19 2^(-25)h9 + 2^(-1))).
+//
+// Proof:
+//   Have |h|<=p so |q|<=1 so |19^2 2^(-255) q|<1/4.
+//   Also have |h-2^230 h9|<2^230 so |19 2^(-255)(h-2^230 h9)|<1/4.
+//
+//   Write y=2^(-1)-19^2 2^(-255)q-19 2^(-255)(h-2^230 h9).
+//   Then 0<y<1.
+//
+//   Write r=h-pq.
+//   Have 0<=r<=p-1=2^255-20.
+//   Thus 0<=r+19(2^-255)r<r+19(2^-255)2^255<=2^255-1.
+//
+//   Write x=r+19(2^-255)r+y.
+//   Then 0<x<2^255 so floor(2^(-255)x) = 0 so floor(q+2^(-255)x) = q.
+//
+//   Have q+2^(-255)x = 2^(-255)(h + 19 2^(-25) h9 + 2^(-1))
+//   so floor(2^(-255)(h + 19 2^(-25) h9 + 2^(-1))) = q.
+func feToBytes(s *[32]byte, h *fieldElement) {
+	var carry [10]int32
+
+	q := (19*h[9] + (1 << 24)) >> 25
+	q = (h[0] + q) >> 26
+	q = (h[1] + q) >> 25
+	q = (h[2] + q) >> 26
+	q = (h[3] + q) >> 25
+	q = (h[4] + q) >> 26
+	q = (h[5] + q) >> 25
+	q = (h[6] + q) >> 26
+	q = (h[7] + q) >> 25
+	q = (h[8] + q) >> 26
+	q = (h[9] + q) >> 25
+
+	// Goal: Output h-(2^255-19)q, which is between 0 and 2^255-20.
+	h[0] += 19 * q
+	// Goal: Output h-2^255 q, which is between 0 and 2^255-20.
+
+	carry[0] = h[0] >> 26
+	h[1] += carry[0]
+	h[0] -= carry[0] << 26
+	carry[1] = h[1] >> 25
+	h[2] += carry[1]
+	h[1] -= carry[1] << 25
+	carry[2] = h[2] >> 26
+	h[3] += carry[2]
+	h[2] -= carry[2] << 26
+	carry[3] = h[3] >> 25
+	h[4] += carry[3]
+	h[3] -= carry[3] << 25
+	carry[4] = h[4] >> 26
+	h[5] += carry[4]
+	h[4] -= carry[4] << 26
+	carry[5] = h[5] >> 25
+	h[6] += carry[5]
+	h[5] -= carry[5] << 25
+	carry[6] = h[6] >> 26
+	h[7] += carry[6]
+	h[6] -= carry[6] << 26
+	carry[7] = h[7] >> 25
+	h[8] += carry[7]
+	h[7] -= carry[7] << 25
+	carry[8] = h[8] >> 26
+	h[9] += carry[8]
+	h[8] -= carry[8] << 26
+	carry[9] = h[9] >> 25
+	h[9] -= carry[9] << 25
+	// h10 = carry9
+
+	// Goal: Output h[0]+...+2^255 h10-2^255 q, which is between 0 and 2^255-20.
+	// Have h[0]+...+2^230 h[9] between 0 and 2^255-1;
+	// evidently 2^255 h10-2^255 q = 0.
+	// Goal: Output h[0]+...+2^230 h[9].
+
+	s[0] = byte(h[0] >> 0)
+	s[1] = byte(h[0] >> 8)
+	s[2] = byte(h[0] >> 16)
+	s[3] = byte((h[0] >> 24) | (h[1] << 2))
+	s[4] = byte(h[1] >> 6)
+	s[5] = byte(h[1] >> 14)
+	s[6] = byte((h[1] >> 22) | (h[2] << 3))
+	s[7] = byte(h[2] >> 5)
+	s[8] = byte(h[2] >> 13)
+	s[9] = byte((h[2] >> 21) | (h[3] << 5))
+	s[10] = byte(h[3] >> 3)
+	s[11] = byte(h[3] >> 11)
+	s[12] = byte((h[3] >> 19) | (h[4] << 6))
+	s[13] = byte(h[4] >> 2)
+	s[14] = byte(h[4] >> 10)
+	s[15] = byte(h[4] >> 18)
+	s[16] = byte(h[5] >> 0)
+	s[17] = byte(h[5] >> 8)
+	s[18] = byte(h[5] >> 16)
+	s[19] = byte((h[5] >> 24) | (h[6] << 1))
+	s[20] = byte(h[6] >> 7)
+	s[21] = byte(h[6] >> 15)
+	s[22] = byte((h[6] >> 23) | (h[7] << 3))
+	s[23] = byte(h[7] >> 5)
+	s[24] = byte(h[7] >> 13)
+	s[25] = byte((h[7] >> 21) | (h[8] << 4))
+	s[26] = byte(h[8] >> 4)
+	s[27] = byte(h[8] >> 12)
+	s[28] = byte((h[8] >> 20) | (h[9] << 6))
+	s[29] = byte(h[9] >> 2)
+	s[30] = byte(h[9] >> 10)
+	s[31] = byte(h[9] >> 18)
+}
+
+// feMul calculates h = f * g
+// Can overlap h with f or g.
+//
+// Preconditions:
+//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
+//    |g| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
+//
+// Postconditions:
+//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+//
+// Notes on implementation strategy:
+//
+// Using schoolbook multiplication.
+// Karatsuba would save a little in some cost models.
+//
+// Most multiplications by 2 and 19 are 32-bit precomputations;
+// cheaper than 64-bit postcomputations.
+//
+// There is one remaining multiplication by 19 in the carry chain;
+// one *19 precomputation can be merged into this,
+// but the resulting data flow is considerably less clean.
+//
+// There are 12 carries below.
+// 10 of them are 2-way parallelizable and vectorizable.
+// Can get away with 11 carries, but then data flow is much deeper.
+//
+// With tighter constraints on inputs can squeeze carries into int32.
+func feMul(h, f, g *fieldElement) {
+	f0 := f[0]
+	f1 := f[1]
+	f2 := f[2]
+	f3 := f[3]
+	f4 := f[4]
+	f5 := f[5]
+	f6 := f[6]
+	f7 := f[7]
+	f8 := f[8]
+	f9 := f[9]
+	g0 := g[0]
+	g1 := g[1]
+	g2 := g[2]
+	g3 := g[3]
+	g4 := g[4]
+	g5 := g[5]
+	g6 := g[6]
+	g7 := g[7]
+	g8 := g[8]
+	g9 := g[9]
+	g1_19 := 19 * g1 // 1.4*2^29
+	g2_19 := 19 * g2 // 1.4*2^30; still ok
+	g3_19 := 19 * g3
+	g4_19 := 19 * g4
+	g5_19 := 19 * g5
+	g6_19 := 19 * g6
+	g7_19 := 19 * g7
+	g8_19 := 19 * g8
+	g9_19 := 19 * g9
+	f1_2 := 2 * f1
+	f3_2 := 2 * f3
+	f5_2 := 2 * f5
+	f7_2 := 2 * f7
+	f9_2 := 2 * f9
+	f0g0 := int64(f0) * int64(g0)
+	f0g1 := int64(f0) * int64(g1)
+	f0g2 := int64(f0) * int64(g2)
+	f0g3 := int64(f0) * int64(g3)
+	f0g4 := int64(f0) * int64(g4)
+	f0g5 := int64(f0) * int64(g5)
+	f0g6 := int64(f0) * int64(g6)
+	f0g7 := int64(f0) * int64(g7)
+	f0g8 := int64(f0) * int64(g8)
+	f0g9 := int64(f0) * int64(g9)
+	f1g0 := int64(f1) * int64(g0)
+	f1g1_2 := int64(f1_2) * int64(g1)
+	f1g2 := int64(f1) * int64(g2)
+	f1g3_2 := int64(f1_2) * int64(g3)
+	f1g4 := int64(f1) * int64(g4)
+	f1g5_2 := int64(f1_2) * int64(g5)
+	f1g6 := int64(f1) * int64(g6)
+	f1g7_2 := int64(f1_2) * int64(g7)
+	f1g8 := int64(f1) * int64(g8)
+	f1g9_38 := int64(f1_2) * int64(g9_19)
+	f2g0 := int64(f2) * int64(g0)
+	f2g1 := int64(f2) * int64(g1)
+	f2g2 := int64(f2) * int64(g2)
+	f2g3 := int64(f2) * int64(g3)
+	f2g4 := int64(f2) * int64(g4)
+	f2g5 := int64(f2) * int64(g5)
+	f2g6 := int64(f2) * int64(g6)
+	f2g7 := int64(f2) * int64(g7)
+	f2g8_19 := int64(f2) * int64(g8_19)
+	f2g9_19 := int64(f2) * int64(g9_19)
+	f3g0 := int64(f3) * int64(g0)
+	f3g1_2 := int64(f3_2) * int64(g1)
+	f3g2 := int64(f3) * int64(g2)
+	f3g3_2 := int64(f3_2) * int64(g3)
+	f3g4 := int64(f3) * int64(g4)
+	f3g5_2 := int64(f3_2) * int64(g5)
+	f3g6 := int64(f3) * int64(g6)
+	f3g7_38 := int64(f3_2) * int64(g7_19)
+	f3g8_19 := int64(f3) * int64(g8_19)
+	f3g9_38 := int64(f3_2) * int64(g9_19)
+	f4g0 := int64(f4) * int64(g0)
+	f4g1 := int64(f4) * int64(g1)
+	f4g2 := int64(f4) * int64(g2)
+	f4g3 := int64(f4) * int64(g3)
+	f4g4 := int64(f4) * int64(g4)
+	f4g5 := int64(f4) * int64(g5)
+	f4g6_19 := int64(f4) * int64(g6_19)
+	f4g7_19 := int64(f4) * int64(g7_19)
+	f4g8_19 := int64(f4) * int64(g8_19)
+	f4g9_19 := int64(f4) * int64(g9_19)
+	f5g0 := int64(f5) * int64(g0)
+	f5g1_2 := int64(f5_2) * int64(g1)
+	f5g2 := int64(f5) * int64(g2)
+	f5g3_2 := int64(f5_2) * int64(g3)
+	f5g4 := int64(f5) * int64(g4)
+	f5g5_38 := int64(f5_2) * int64(g5_19)
+	f5g6_19 := int64(f5) * int64(g6_19)
+	f5g7_38 := int64(f5_2) * int64(g7_19)
+	f5g8_19 := int64(f5) * int64(g8_19)
+	f5g9_38 := int64(f5_2) * int64(g9_19)
+	f6g0 := int64(f6) * int64(g0)
+	f6g1 := int64(f6) * int64(g1)
+	f6g2 := int64(f6) * int64(g2)
+	f6g3 := int64(f6) * int64(g3)
+	f6g4_19 := int64(f6) * int64(g4_19)
+	f6g5_19 := int64(f6) * int64(g5_19)
+	f6g6_19 := int64(f6) * int64(g6_19)
+	f6g7_19 := int64(f6) * int64(g7_19)
+	f6g8_19 := int64(f6) * int64(g8_19)
+	f6g9_19 := int64(f6) * int64(g9_19)
+	f7g0 := int64(f7) * int64(g0)
+	f7g1_2 := int64(f7_2) * int64(g1)
+	f7g2 := int64(f7) * int64(g2)
+	f7g3_38 := int64(f7_2) * int64(g3_19)
+	f7g4_19 := int64(f7) * int64(g4_19)
+	f7g5_38 := int64(f7_2) * int64(g5_19)
+	f7g6_19 := int64(f7) * int64(g6_19)
+	f7g7_38 := int64(f7_2) * int64(g7_19)
+	f7g8_19 := int64(f7) * int64(g8_19)
+	f7g9_38 := int64(f7_2) * int64(g9_19)
+	f8g0 := int64(f8) * int64(g0)
+	f8g1 := int64(f8) * int64(g1)
+	f8g2_19 := int64(f8) * int64(g2_19)
+	f8g3_19 := int64(f8) * int64(g3_19)
+	f8g4_19 := int64(f8) * int64(g4_19)
+	f8g5_19 := int64(f8) * int64(g5_19)
+	f8g6_19 := int64(f8) * int64(g6_19)
+	f8g7_19 := int64(f8) * int64(g7_19)
+	f8g8_19 := int64(f8) * int64(g8_19)
+	f8g9_19 := int64(f8) * int64(g9_19)
+	f9g0 := int64(f9) * int64(g0)
+	f9g1_38 := int64(f9_2) * int64(g1_19)
+	f9g2_19 := int64(f9) * int64(g2_19)
+	f9g3_38 := int64(f9_2) * int64(g3_19)
+	f9g4_19 := int64(f9) * int64(g4_19)
+	f9g5_38 := int64(f9_2) * int64(g5_19)
+	f9g6_19 := int64(f9) * int64(g6_19)
+	f9g7_38 := int64(f9_2) * int64(g7_19)
+	f9g8_19 := int64(f9) * int64(g8_19)
+	f9g9_38 := int64(f9_2) * int64(g9_19)
+	h0 := f0g0 + f1g9_38 + f2g8_19 + f3g7_38 + f4g6_19 + f5g5_38 + f6g4_19 + f7g3_38 + f8g2_19 + f9g1_38
+	h1 := f0g1 + f1g0 + f2g9_19 + f3g8_19 + f4g7_19 + f5g6_19 + f6g5_19 + f7g4_19 + f8g3_19 + f9g2_19
+	h2 := f0g2 + f1g1_2 + f2g0 + f3g9_38 + f4g8_19 + f5g7_38 + f6g6_19 + f7g5_38 + f8g4_19 + f9g3_38
+	h3 := f0g3 + f1g2 + f2g1 + f3g0 + f4g9_19 + f5g8_19 + f6g7_19 + f7g6_19 + f8g5_19 + f9g4_19
+	h4 := f0g4 + f1g3_2 + f2g2 + f3g1_2 + f4g0 + f5g9_38 + f6g8_19 + f7g7_38 + f8g6_19 + f9g5_38
+	h5 := f0g5 + f1g4 + f2g3 + f3g2 + f4g1 + f5g0 + f6g9_19 + f7g8_19 + f8g7_19 + f9g6_19
+	h6 := f0g6 + f1g5_2 + f2g4 + f3g3_2 + f4g2 + f5g1_2 + f6g0 + f7g9_38 + f8g8_19 + f9g7_38
+	h7 := f0g7 + f1g6 + f2g5 + f3g4 + f4g3 + f5g2 + f6g1 + f7g0 + f8g9_19 + f9g8_19
+	h8 := f0g8 + f1g7_2 + f2g6 + f3g5_2 + f4g4 + f5g3_2 + f6g2 + f7g1_2 + f8g0 + f9g9_38
+	h9 := f0g9 + f1g8 + f2g7 + f3g6 + f4g5 + f5g4 + f6g3 + f7g2 + f8g1 + f9g0
+	var carry [10]int64
+
+	// |h0| <= (1.1*1.1*2^52*(1+19+19+19+19)+1.1*1.1*2^50*(38+38+38+38+38))
+	//   i.e. |h0| <= 1.2*2^59; narrower ranges for h2, h4, h6, h8
+	// |h1| <= (1.1*1.1*2^51*(1+1+19+19+19+19+19+19+19+19))
+	//   i.e. |h1| <= 1.5*2^58; narrower ranges for h3, h5, h7, h9
+
+	carry[0] = (h0 + (1 << 25)) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+	carry[4] = (h4 + (1 << 25)) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+	// |h0| <= 2^25
+	// |h4| <= 2^25
+	// |h1| <= 1.51*2^58
+	// |h5| <= 1.51*2^58
+
+	carry[1] = (h1 + (1 << 24)) >> 25
+	h2 += carry[1]
+	h1 -= carry[1] << 25
+	carry[5] = (h5 + (1 << 24)) >> 25
+	h6 += carry[5]
+	h5 -= carry[5] << 25
+	// |h1| <= 2^24; from now on fits into int32
+	// |h5| <= 2^24; from now on fits into int32
+	// |h2| <= 1.21*2^59
+	// |h6| <= 1.21*2^59
+
+	carry[2] = (h2 + (1 << 25)) >> 26
+	h3 += carry[2]
+	h2 -= carry[2] << 26
+	carry[6] = (h6 + (1 << 25)) >> 26
+	h7 += carry[6]
+	h6 -= carry[6] << 26
+	// |h2| <= 2^25; from now on fits into int32 unchanged
+	// |h6| <= 2^25; from now on fits into int32 unchanged
+	// |h3| <= 1.51*2^58
+	// |h7| <= 1.51*2^58
+
+	carry[3] = (h3 + (1 << 24)) >> 25
+	h4 += carry[3]
+	h3 -= carry[3] << 25
+	carry[7] = (h7 + (1 << 24)) >> 25
+	h8 += carry[7]
+	h7 -= carry[7] << 25
+	// |h3| <= 2^24; from now on fits into int32 unchanged
+	// |h7| <= 2^24; from now on fits into int32 unchanged
+	// |h4| <= 1.52*2^33
+	// |h8| <= 1.52*2^33
+
+	carry[4] = (h4 + (1 << 25)) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+	carry[8] = (h8 + (1 << 25)) >> 26
+	h9 += carry[8]
+	h8 -= carry[8] << 26
+	// |h4| <= 2^25; from now on fits into int32 unchanged
+	// |h8| <= 2^25; from now on fits into int32 unchanged
+	// |h5| <= 1.01*2^24
+	// |h9| <= 1.51*2^58
+
+	carry[9] = (h9 + (1 << 24)) >> 25
+	h0 += carry[9] * 19
+	h9 -= carry[9] << 25
+	// |h9| <= 2^24; from now on fits into int32 unchanged
+	// |h0| <= 1.8*2^37
+
+	carry[0] = (h0 + (1 << 25)) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+	// |h0| <= 2^25; from now on fits into int32 unchanged
+	// |h1| <= 1.01*2^24
+
+	h[0] = int32(h0)
+	h[1] = int32(h1)
+	h[2] = int32(h2)
+	h[3] = int32(h3)
+	h[4] = int32(h4)
+	h[5] = int32(h5)
+	h[6] = int32(h6)
+	h[7] = int32(h7)
+	h[8] = int32(h8)
+	h[9] = int32(h9)
+}
+
+// feSquare calculates h = f*f. Can overlap h with f.
+//
+// Preconditions:
+//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
+//
+// Postconditions:
+//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+func feSquare(h, f *fieldElement) {
+	f0 := f[0]
+	f1 := f[1]
+	f2 := f[2]
+	f3 := f[3]
+	f4 := f[4]
+	f5 := f[5]
+	f6 := f[6]
+	f7 := f[7]
+	f8 := f[8]
+	f9 := f[9]
+	f0_2 := 2 * f0
+	f1_2 := 2 * f1
+	f2_2 := 2 * f2
+	f3_2 := 2 * f3
+	f4_2 := 2 * f4
+	f5_2 := 2 * f5
+	f6_2 := 2 * f6
+	f7_2 := 2 * f7
+	f5_38 := 38 * f5 // 1.31*2^30
+	f6_19 := 19 * f6 // 1.31*2^30
+	f7_38 := 38 * f7 // 1.31*2^30
+	f8_19 := 19 * f8 // 1.31*2^30
+	f9_38 := 38 * f9 // 1.31*2^30
+	f0f0 := int64(f0) * int64(f0)
+	f0f1_2 := int64(f0_2) * int64(f1)
+	f0f2_2 := int64(f0_2) * int64(f2)
+	f0f3_2 := int64(f0_2) * int64(f3)
+	f0f4_2 := int64(f0_2) * int64(f4)
+	f0f5_2 := int64(f0_2) * int64(f5)
+	f0f6_2 := int64(f0_2) * int64(f6)
+	f0f7_2 := int64(f0_2) * int64(f7)
+	f0f8_2 := int64(f0_2) * int64(f8)
+	f0f9_2 := int64(f0_2) * int64(f9)
+	f1f1_2 := int64(f1_2) * int64(f1)
+	f1f2_2 := int64(f1_2) * int64(f2)
+	f1f3_4 := int64(f1_2) * int64(f3_2)
+	f1f4_2 := int64(f1_2) * int64(f4)
+	f1f5_4 := int64(f1_2) * int64(f5_2)
+	f1f6_2 := int64(f1_2) * int64(f6)
+	f1f7_4 := int64(f1_2) * int64(f7_2)
+	f1f8_2 := int64(f1_2) * int64(f8)
+	f1f9_76 := int64(f1_2) * int64(f9_38)
+	f2f2 := int64(f2) * int64(f2)
+	f2f3_2 := int64(f2_2) * int64(f3)
+	f2f4_2 := int64(f2_2) * int64(f4)
+	f2f5_2 := int64(f2_2) * int64(f5)
+	f2f6_2 := int64(f2_2) * int64(f6)
+	f2f7_2 := int64(f2_2) * int64(f7)
+	f2f8_38 := int64(f2_2) * int64(f8_19)
+	f2f9_38 := int64(f2) * int64(f9_38)
+	f3f3_2 := int64(f3_2) * int64(f3)
+	f3f4_2 := int64(f3_2) * int64(f4)
+	f3f5_4 := int64(f3_2) * int64(f5_2)
+	f3f6_2 := int64(f3_2) * int64(f6)
+	f3f7_76 := int64(f3_2) * int64(f7_38)
+	f3f8_38 := int64(f3_2) * int64(f8_19)
+	f3f9_76 := int64(f3_2) * int64(f9_38)
+	f4f4 := int64(f4) * int64(f4)
+	f4f5_2 := int64(f4_2) * int64(f5)
+	f4f6_38 := int64(f4_2) * int64(f6_19)
+	f4f7_38 := int64(f4) * int64(f7_38)
+	f4f8_38 := int64(f4_2) * int64(f8_19)
+	f4f9_38 := int64(f4) * int64(f9_38)
+	f5f5_38 := int64(f5) * int64(f5_38)
+	f5f6_38 := int64(f5_2) * int64(f6_19)
+	f5f7_76 := int64(f5_2) * int64(f7_38)
+	f5f8_38 := int64(f5_2) * int64(f8_19)
+	f5f9_76 := int64(f5_2) * int64(f9_38)
+	f6f6_19 := int64(f6) * int64(f6_19)
+	f6f7_38 := int64(f6) * int64(f7_38)
+	f6f8_38 := int64(f6_2) * int64(f8_19)
+	f6f9_38 := int64(f6) * int64(f9_38)
+	f7f7_38 := int64(f7) * int64(f7_38)
+	f7f8_38 := int64(f7_2) * int64(f8_19)
+	f7f9_76 := int64(f7_2) * int64(f9_38)
+	f8f8_19 := int64(f8) * int64(f8_19)
+	f8f9_38 := int64(f8) * int64(f9_38)
+	f9f9_38 := int64(f9) * int64(f9_38)
+	h0 := f0f0 + f1f9_76 + f2f8_38 + f3f7_76 + f4f6_38 + f5f5_38
+	h1 := f0f1_2 + f2f9_38 + f3f8_38 + f4f7_38 + f5f6_38
+	h2 := f0f2_2 + f1f1_2 + f3f9_76 + f4f8_38 + f5f7_76 + f6f6_19
+	h3 := f0f3_2 + f1f2_2 + f4f9_38 + f5f8_38 + f6f7_38
+	h4 := f0f4_2 + f1f3_4 + f2f2 + f5f9_76 + f6f8_38 + f7f7_38
+	h5 := f0f5_2 + f1f4_2 + f2f3_2 + f6f9_38 + f7f8_38
+	h6 := f0f6_2 + f1f5_4 + f2f4_2 + f3f3_2 + f7f9_76 + f8f8_19
+	h7 := f0f7_2 + f1f6_2 + f2f5_2 + f3f4_2 + f8f9_38
+	h8 := f0f8_2 + f1f7_4 + f2f6_2 + f3f5_4 + f4f4 + f9f9_38
+	h9 := f0f9_2 + f1f8_2 + f2f7_2 + f3f6_2 + f4f5_2
+	var carry [10]int64
+
+	carry[0] = (h0 + (1 << 25)) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+	carry[4] = (h4 + (1 << 25)) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+
+	carry[1] = (h1 + (1 << 24)) >> 25
+	h2 += carry[1]
+	h1 -= carry[1] << 25
+	carry[5] = (h5 + (1 << 24)) >> 25
+	h6 += carry[5]
+	h5 -= carry[5] << 25
+
+	carry[2] = (h2 + (1 << 25)) >> 26
+	h3 += carry[2]
+	h2 -= carry[2] << 26
+	carry[6] = (h6 + (1 << 25)) >> 26
+	h7 += carry[6]
+	h6 -= carry[6] << 26
+
+	carry[3] = (h3 + (1 << 24)) >> 25
+	h4 += carry[3]
+	h3 -= carry[3] << 25
+	carry[7] = (h7 + (1 << 24)) >> 25
+	h8 += carry[7]
+	h7 -= carry[7] << 25
+
+	carry[4] = (h4 + (1 << 25)) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+	carry[8] = (h8 + (1 << 25)) >> 26
+	h9 += carry[8]
+	h8 -= carry[8] << 26
+
+	carry[9] = (h9 + (1 << 24)) >> 25
+	h0 += carry[9] * 19
+	h9 -= carry[9] << 25
+
+	carry[0] = (h0 + (1 << 25)) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+
+	h[0] = int32(h0)
+	h[1] = int32(h1)
+	h[2] = int32(h2)
+	h[3] = int32(h3)
+	h[4] = int32(h4)
+	h[5] = int32(h5)
+	h[6] = int32(h6)
+	h[7] = int32(h7)
+	h[8] = int32(h8)
+	h[9] = int32(h9)
+}
+
+// feMul121666 calculates h = f * 121666. Can overlap h with f.
+//
+// Preconditions:
+//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
+//
+// Postconditions:
+//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+func feMul121666(h, f *fieldElement) {
+	h0 := int64(f[0]) * 121666
+	h1 := int64(f[1]) * 121666
+	h2 := int64(f[2]) * 121666
+	h3 := int64(f[3]) * 121666
+	h4 := int64(f[4]) * 121666
+	h5 := int64(f[5]) * 121666
+	h6 := int64(f[6]) * 121666
+	h7 := int64(f[7]) * 121666
+	h8 := int64(f[8]) * 121666
+	h9 := int64(f[9]) * 121666
+	var carry [10]int64
+
+	carry[9] = (h9 + (1 << 24)) >> 25
+	h0 += carry[9] * 19
+	h9 -= carry[9] << 25
+	carry[1] = (h1 + (1 << 24)) >> 25
+	h2 += carry[1]
+	h1 -= carry[1] << 25
+	carry[3] = (h3 + (1 << 24)) >> 25
+	h4 += carry[3]
+	h3 -= carry[3] << 25
+	carry[5] = (h5 + (1 << 24)) >> 25
+	h6 += carry[5]
+	h5 -= carry[5] << 25
+	carry[7] = (h7 + (1 << 24)) >> 25
+	h8 += carry[7]
+	h7 -= carry[7] << 25
+
+	carry[0] = (h0 + (1 << 25)) >> 26
+	h1 += carry[0]
+	h0 -= carry[0] << 26
+	carry[2] = (h2 + (1 << 25)) >> 26
+	h3 += carry[2]
+	h2 -= carry[2] << 26
+	carry[4] = (h4 + (1 << 25)) >> 26
+	h5 += carry[4]
+	h4 -= carry[4] << 26
+	carry[6] = (h6 + (1 << 25)) >> 26
+	h7 += carry[6]
+	h6 -= carry[6] << 26
+	carry[8] = (h8 + (1 << 25)) >> 26
+	h9 += carry[8]
+	h8 -= carry[8] << 26
+
+	h[0] = int32(h0)
+	h[1] = int32(h1)
+	h[2] = int32(h2)
+	h[3] = int32(h3)
+	h[4] = int32(h4)
+	h[5] = int32(h5)
+	h[6] = int32(h6)
+	h[7] = int32(h7)
+	h[8] = int32(h8)
+	h[9] = int32(h9)
+}
+
+// feInvert sets out = z^-1.
+func feInvert(out, z *fieldElement) {
+	var t0, t1, t2, t3 fieldElement
+	var i int
+
+	feSquare(&t0, z)
+	for i = 1; i < 1; i++ {
+		feSquare(&t0, &t0)
+	}
+	feSquare(&t1, &t0)
+	for i = 1; i < 2; i++ {
+		feSquare(&t1, &t1)
+	}
+	feMul(&t1, z, &t1)
+	feMul(&t0, &t0, &t1)
+	feSquare(&t2, &t0)
+	for i = 1; i < 1; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t1, &t1, &t2)
+	feSquare(&t2, &t1)
+	for i = 1; i < 5; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t1, &t2, &t1)
+	feSquare(&t2, &t1)
+	for i = 1; i < 10; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t2, &t2, &t1)
+	feSquare(&t3, &t2)
+	for i = 1; i < 20; i++ {
+		feSquare(&t3, &t3)
+	}
+	feMul(&t2, &t3, &t2)
+	feSquare(&t2, &t2)
+	for i = 1; i < 10; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t1, &t2, &t1)
+	feSquare(&t2, &t1)
+	for i = 1; i < 50; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t2, &t2, &t1)
+	feSquare(&t3, &t2)
+	for i = 1; i < 100; i++ {
+		feSquare(&t3, &t3)
+	}
+	feMul(&t2, &t3, &t2)
+	feSquare(&t2, &t2)
+	for i = 1; i < 50; i++ {
+		feSquare(&t2, &t2)
+	}
+	feMul(&t1, &t2, &t1)
+	feSquare(&t1, &t1)
+	for i = 1; i < 5; i++ {
+		feSquare(&t1, &t1)
+	}
+	feMul(out, &t1, &t0)
+}
+
+func scalarMult(out, in, base *[32]byte) {
+	var e [32]byte
+
+	copy(e[:], in[:])
+	e[0] &= 248
+	e[31] &= 127
+	e[31] |= 64
+
+	var x1, x2, z2, x3, z3, tmp0, tmp1 fieldElement
+	feFromBytes(&x1, base)
+	feOne(&x2)
+	feCopy(&x3, &x1)
+	feOne(&z3)
+
+	swap := int32(0)
+	for pos := 254; pos >= 0; pos-- {
+		b := e[pos/8] >> uint(pos&7)
+		b &= 1
+		swap ^= int32(b)
+		feCSwap(&x2, &x3, swap)
+		feCSwap(&z2, &z3, swap)
+		swap = int32(b)
+
+		feSub(&tmp0, &x3, &z3)
+		feSub(&tmp1, &x2, &z2)
+		feAdd(&x2, &x2, &z2)
+		feAdd(&z2, &x3, &z3)
+		feMul(&z3, &tmp0, &x2)
+		feMul(&z2, &z2, &tmp1)
+		feSquare(&tmp0, &tmp1)
+		feSquare(&tmp1, &x2)
+		feAdd(&x3, &z3, &z2)
+		feSub(&z2, &z3, &z2)
+		feMul(&x2, &tmp1, &tmp0)
+		feSub(&tmp1, &tmp1, &tmp0)
+		feSquare(&z2, &z2)
+		feMul121666(&z3, &tmp1)
+		feSquare(&x3, &x3)
+		feAdd(&tmp0, &tmp0, &z3)
+		feMul(&z3, &x1, &z2)
+		feMul(&z2, &tmp1, &tmp0)
+	}
+
+	feCSwap(&x2, &x3, swap)
+	feCSwap(&z2, &z3, swap)
+
+	feInvert(&z2, &z2)
+	feMul(&x2, &x2, &z2)
+	feToBytes(out, &x2)
+}
diff --git a/vendor/golang.org/x/crypto/ed25519/ed25519.go b/vendor/golang.org/x/crypto/ed25519/ed25519.go
index 16cd385..d6f683b 100644
--- a/vendor/golang.org/x/crypto/ed25519/ed25519.go
+++ b/vendor/golang.org/x/crypto/ed25519/ed25519.go
@@ -6,7 +6,10 @@
 // https://ed25519.cr.yp.to/.
 //
 // These functions are also compatible with the “Ed25519” function defined in
-// https://tools.ietf.org/html/draft-irtf-cfrg-eddsa-05.
+// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
+// representation includes a public key suffix to make multiple signing
+// operations with the same key more efficient. This package refers to the RFC
+// 8032 private key as the “seed”.
 package ed25519
 
 // This code is a port of the public domain, “ref10” implementation of ed25519
@@ -31,6 +34,8 @@ const (
 	PrivateKeySize = 64
 	// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
 	SignatureSize = 64
+	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
+	SeedSize = 32
 )
 
 // PublicKey is the type of Ed25519 public keys.
@@ -46,6 +51,15 @@ func (priv PrivateKey) Public() crypto.PublicKey {
 	return PublicKey(publicKey)
 }
 
+// Seed returns the private key seed corresponding to priv. It is provided for
+// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
+// in this package.
+func (priv PrivateKey) Seed() []byte {
+	seed := make([]byte, SeedSize)
+	copy(seed, priv[:32])
+	return seed
+}
+
 // Sign signs the given message with priv.
 // Ed25519 performs two passes over messages to be signed and therefore cannot
 // handle pre-hashed messages. Thus opts.HashFunc() must return zero to
@@ -61,19 +75,33 @@ func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOp
 
 // GenerateKey generates a public/private key pair using entropy from rand.
 // If rand is nil, crypto/rand.Reader will be used.
-func GenerateKey(rand io.Reader) (publicKey PublicKey, privateKey PrivateKey, err error) {
+func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
 	if rand == nil {
 		rand = cryptorand.Reader
 	}
 
-	privateKey = make([]byte, PrivateKeySize)
-	publicKey = make([]byte, PublicKeySize)
-	_, err = io.ReadFull(rand, privateKey[:32])
-	if err != nil {
+	seed := make([]byte, SeedSize)
+	if _, err := io.ReadFull(rand, seed); err != nil {
 		return nil, nil, err
 	}
 
-	digest := sha512.Sum512(privateKey[:32])
+	privateKey := NewKeyFromSeed(seed)
+	publicKey := make([]byte, PublicKeySize)
+	copy(publicKey, privateKey[32:])
+
+	return publicKey, privateKey, nil
+}
+
+// NewKeyFromSeed calculates a private key from a seed. It will panic if
+// len(seed) is not SeedSize. This function is provided for interoperability
+// with RFC 8032. RFC 8032's private keys correspond to seeds in this
+// package.
+func NewKeyFromSeed(seed []byte) PrivateKey {
+	if l := len(seed); l != SeedSize {
+		panic("ed25519: bad seed length: " + strconv.Itoa(l))
+	}
+
+	digest := sha512.Sum512(seed)
 	digest[0] &= 248
 	digest[31] &= 127
 	digest[31] |= 64
@@ -85,10 +113,11 @@ func GenerateKey(rand io.Reader) (publicKey PublicKey, privateKey PrivateKey, er
 	var publicKeyBytes [32]byte
 	A.ToBytes(&publicKeyBytes)
 
+	privateKey := make([]byte, PrivateKeySize)
+	copy(privateKey, seed)
 	copy(privateKey[32:], publicKeyBytes[:])
-	copy(publicKey, publicKeyBytes[:])
 
-	return publicKey, privateKey, nil
+	return privateKey
 }
 
 // Sign signs the message with privateKey and returns a signature. It will
@@ -171,9 +200,16 @@ func Verify(publicKey PublicKey, message, sig []byte) bool {
 	edwards25519.ScReduce(&hReduced, &digest)
 
 	var R edwards25519.ProjectiveGroupElement
-	var b [32]byte
-	copy(b[:], sig[32:])
-	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &b)
+	var s [32]byte
+	copy(s[:], sig[32:])
+
+	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
+	// the range [0, order) in order to prevent signature malleability.
+	if !edwards25519.ScMinimal(&s) {
+		return false
+	}
+
+	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)
 
 	var checkR [32]byte
 	R.ToBytes(&checkR)
diff --git a/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go b/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
index 5f8b994..fd03c25 100644
--- a/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
+++ b/vendor/golang.org/x/crypto/ed25519/internal/edwards25519/edwards25519.go
@@ -4,6 +4,8 @@
 
 package edwards25519
 
+import "encoding/binary"
+
 // This code is a port of the public domain, “ref10” implementation of ed25519
 // from SUPERCOP.
 
@@ -1769,3 +1771,23 @@ func ScReduce(out *[32]byte, s *[64]byte) {
 	out[30] = byte(s11 >> 9)
 	out[31] = byte(s11 >> 17)
 }
+
+// order is the order of Curve25519 in little-endian form.
+var order = [4]uint64{0x5812631a5cf5d3ed, 0x14def9dea2f79cd6, 0, 0x1000000000000000}
+
+// ScMinimal returns true if the given scalar is less than the order of the
+// curve.
+func ScMinimal(scalar *[32]byte) bool {
+	for i := 3; ; i-- {
+		v := binary.LittleEndian.Uint64(scalar[i*8:])
+		if v > order[i] {
+			return false
+		} else if v < order[i] {
+			break
+		} else if i == 0 {
+			return false
+		}
+	}
+
+	return true
+}
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/asm_s390x.s b/vendor/golang.org/x/crypto/internal/chacha20/asm_s390x.s
new file mode 100644
index 0000000..98427c5
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/asm_s390x.s
@@ -0,0 +1,283 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,!gccgo,!appengine
+
+#include "go_asm.h"
+#include "textflag.h"
+
+// This is an implementation of the ChaCha20 encryption algorithm as
+// specified in RFC 7539. It uses vector instructions to compute
+// 4 keystream blocks in parallel (256 bytes) which are then XORed
+// with the bytes in the input slice.
+
+GLOBL ·constants<>(SB), RODATA|NOPTR, $32
+// BSWAP: swap bytes in each 4-byte element
+DATA ·constants<>+0x00(SB)/4, $0x03020100
+DATA ·constants<>+0x04(SB)/4, $0x07060504
+DATA ·constants<>+0x08(SB)/4, $0x0b0a0908
+DATA ·constants<>+0x0c(SB)/4, $0x0f0e0d0c
+// J0: [j0, j1, j2, j3]
+DATA ·constants<>+0x10(SB)/4, $0x61707865
+DATA ·constants<>+0x14(SB)/4, $0x3320646e
+DATA ·constants<>+0x18(SB)/4, $0x79622d32
+DATA ·constants<>+0x1c(SB)/4, $0x6b206574
+
+// EXRL targets:
+TEXT ·mvcSrcToBuf(SB), NOFRAME|NOSPLIT, $0
+	MVC $1, (R1), (R8)
+	RET
+
+TEXT ·mvcBufToDst(SB), NOFRAME|NOSPLIT, $0
+	MVC $1, (R8), (R9)
+	RET
+
+#define BSWAP V5
+#define J0    V6
+#define KEY0  V7
+#define KEY1  V8
+#define NONCE V9
+#define CTR   V10
+#define M0    V11
+#define M1    V12
+#define M2    V13
+#define M3    V14
+#define INC   V15
+#define X0    V16
+#define X1    V17
+#define X2    V18
+#define X3    V19
+#define X4    V20
+#define X5    V21
+#define X6    V22
+#define X7    V23
+#define X8    V24
+#define X9    V25
+#define X10   V26
+#define X11   V27
+#define X12   V28
+#define X13   V29
+#define X14   V30
+#define X15   V31
+
+#define NUM_ROUNDS 20
+
+#define ROUND4(a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3, d0, d1, d2, d3) \
+	VAF    a1, a0, a0  \
+	VAF    b1, b0, b0  \
+	VAF    c1, c0, c0  \
+	VAF    d1, d0, d0  \
+	VX     a0, a2, a2  \
+	VX     b0, b2, b2  \
+	VX     c0, c2, c2  \
+	VX     d0, d2, d2  \
+	VERLLF $16, a2, a2 \
+	VERLLF $16, b2, b2 \
+	VERLLF $16, c2, c2 \
+	VERLLF $16, d2, d2 \
+	VAF    a2, a3, a3  \
+	VAF    b2, b3, b3  \
+	VAF    c2, c3, c3  \
+	VAF    d2, d3, d3  \
+	VX     a3, a1, a1  \
+	VX     b3, b1, b1  \
+	VX     c3, c1, c1  \
+	VX     d3, d1, d1  \
+	VERLLF $12, a1, a1 \
+	VERLLF $12, b1, b1 \
+	VERLLF $12, c1, c1 \
+	VERLLF $12, d1, d1 \
+	VAF    a1, a0, a0  \
+	VAF    b1, b0, b0  \
+	VAF    c1, c0, c0  \
+	VAF    d1, d0, d0  \
+	VX     a0, a2, a2  \
+	VX     b0, b2, b2  \
+	VX     c0, c2, c2  \
+	VX     d0, d2, d2  \
+	VERLLF $8, a2, a2  \
+	VERLLF $8, b2, b2  \
+	VERLLF $8, c2, c2  \
+	VERLLF $8, d2, d2  \
+	VAF    a2, a3, a3  \
+	VAF    b2, b3, b3  \
+	VAF    c2, c3, c3  \
+	VAF    d2, d3, d3  \
+	VX     a3, a1, a1  \
+	VX     b3, b1, b1  \
+	VX     c3, c1, c1  \
+	VX     d3, d1, d1  \
+	VERLLF $7, a1, a1  \
+	VERLLF $7, b1, b1  \
+	VERLLF $7, c1, c1  \
+	VERLLF $7, d1, d1
+
+#define PERMUTE(mask, v0, v1, v2, v3) \
+	VPERM v0, v0, mask, v0 \
+	VPERM v1, v1, mask, v1 \
+	VPERM v2, v2, mask, v2 \
+	VPERM v3, v3, mask, v3
+
+#define ADDV(x, v0, v1, v2, v3) \
+	VAF x, v0, v0 \
+	VAF x, v1, v1 \
+	VAF x, v2, v2 \
+	VAF x, v3, v3
+
+#define XORV(off, dst, src, v0, v1, v2, v3) \
+	VLM  off(src), M0, M3          \
+	PERMUTE(BSWAP, v0, v1, v2, v3) \
+	VX   v0, M0, M0                \
+	VX   v1, M1, M1                \
+	VX   v2, M2, M2                \
+	VX   v3, M3, M3                \
+	VSTM M0, M3, off(dst)
+
+#define SHUFFLE(a, b, c, d, t, u, v, w) \
+	VMRHF a, c, t \ // t = {a[0], c[0], a[1], c[1]}
+	VMRHF b, d, u \ // u = {b[0], d[0], b[1], d[1]}
+	VMRLF a, c, v \ // v = {a[2], c[2], a[3], c[3]}
+	VMRLF b, d, w \ // w = {b[2], d[2], b[3], d[3]}
+	VMRHF t, u, a \ // a = {a[0], b[0], c[0], d[0]}
+	VMRLF t, u, b \ // b = {a[1], b[1], c[1], d[1]}
+	VMRHF v, w, c \ // c = {a[2], b[2], c[2], d[2]}
+	VMRLF v, w, d // d = {a[3], b[3], c[3], d[3]}
+
+// func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32, buf *[256]byte, len *int)
+TEXT ·xorKeyStreamVX(SB), NOSPLIT, $0
+	MOVD $·constants<>(SB), R1
+	MOVD dst+0(FP), R2         // R2=&dst[0]
+	LMG  src+24(FP), R3, R4    // R3=&src[0] R4=len(src)
+	MOVD key+48(FP), R5        // R5=key
+	MOVD nonce+56(FP), R6      // R6=nonce
+	MOVD counter+64(FP), R7    // R7=counter
+	MOVD buf+72(FP), R8        // R8=buf
+	MOVD len+80(FP), R9        // R9=len
+
+	// load BSWAP and J0
+	VLM (R1), BSWAP, J0
+
+	// set up tail buffer
+	ADD     $-1, R4, R12
+	MOVBZ   R12, R12
+	CMPUBEQ R12, $255, aligned
+	MOVD    R4, R1
+	AND     $~255, R1
+	MOVD    $(R3)(R1*1), R1
+	EXRL    $·mvcSrcToBuf(SB), R12
+	MOVD    $255, R0
+	SUB     R12, R0
+	MOVD    R0, (R9)               // update len
+
+aligned:
+	// setup
+	MOVD  $95, R0
+	VLM   (R5), KEY0, KEY1
+	VLL   R0, (R6), NONCE
+	VZERO M0
+	VLEIB $7, $32, M0
+	VSRLB M0, NONCE, NONCE
+
+	// initialize counter values
+	VLREPF (R7), CTR
+	VZERO  INC
+	VLEIF  $1, $1, INC
+	VLEIF  $2, $2, INC
+	VLEIF  $3, $3, INC
+	VAF    INC, CTR, CTR
+	VREPIF $4, INC
+
+chacha:
+	VREPF $0, J0, X0
+	VREPF $1, J0, X1
+	VREPF $2, J0, X2
+	VREPF $3, J0, X3
+	VREPF $0, KEY0, X4
+	VREPF $1, KEY0, X5
+	VREPF $2, KEY0, X6
+	VREPF $3, KEY0, X7
+	VREPF $0, KEY1, X8
+	VREPF $1, KEY1, X9
+	VREPF $2, KEY1, X10
+	VREPF $3, KEY1, X11
+	VLR   CTR, X12
+	VREPF $1, NONCE, X13
+	VREPF $2, NONCE, X14
+	VREPF $3, NONCE, X15
+
+	MOVD $(NUM_ROUNDS/2), R1
+
+loop:
+	ROUND4(X0, X4, X12,  X8, X1, X5, X13,  X9, X2, X6, X14, X10, X3, X7, X15, X11)
+	ROUND4(X0, X5, X15, X10, X1, X6, X12, X11, X2, X7, X13, X8,  X3, X4, X14, X9)
+
+	ADD $-1, R1
+	BNE loop
+
+	// decrement length
+	ADD $-256, R4
+	BLT tail
+
+continue:
+	// rearrange vectors
+	SHUFFLE(X0, X1, X2, X3, M0, M1, M2, M3)
+	ADDV(J0, X0, X1, X2, X3)
+	SHUFFLE(X4, X5, X6, X7, M0, M1, M2, M3)
+	ADDV(KEY0, X4, X5, X6, X7)
+	SHUFFLE(X8, X9, X10, X11, M0, M1, M2, M3)
+	ADDV(KEY1, X8, X9, X10, X11)
+	VAF CTR, X12, X12
+	SHUFFLE(X12, X13, X14, X15, M0, M1, M2, M3)
+	ADDV(NONCE, X12, X13, X14, X15)
+
+	// increment counters
+	VAF INC, CTR, CTR
+
+	// xor keystream with plaintext
+	XORV(0*64, R2, R3, X0, X4,  X8, X12)
+	XORV(1*64, R2, R3, X1, X5,  X9, X13)
+	XORV(2*64, R2, R3, X2, X6, X10, X14)
+	XORV(3*64, R2, R3, X3, X7, X11, X15)
+
+	// increment pointers
+	MOVD $256(R2), R2
+	MOVD $256(R3), R3
+
+	CMPBNE  R4, $0, chacha
+	CMPUBEQ R12, $255, return
+	EXRL    $·mvcBufToDst(SB), R12 // len was updated during setup
+
+return:
+	VSTEF $0, CTR, (R7)
+	RET
+
+tail:
+	MOVD R2, R9
+	MOVD R8, R2
+	MOVD R8, R3
+	MOVD $0, R4
+	JMP  continue
+
+// func hasVectorFacility() bool
+TEXT ·hasVectorFacility(SB), NOSPLIT, $24-1
+	MOVD  $x-24(SP), R1
+	XC    $24, 0(R1), 0(R1) // clear the storage
+	MOVD  $2, R0            // R0 is the number of double words stored -1
+	WORD  $0xB2B01000       // STFLE 0(R1)
+	XOR   R0, R0            // reset the value of R0
+	MOVBZ z-8(SP), R1
+	AND   $0x40, R1
+	BEQ   novector
+
+vectorinstalled:
+	// check if the vector instruction has been enabled
+	VLEIB  $0, $0xF, V16
+	VLGVB  $0, V16, R1
+	CMPBNE R1, $0xF, novector
+	MOVB   $1, ret+0(FP)      // have vx
+	RET
+
+novector:
+	MOVB $0, ret+0(FP) // no vx
+	RET
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go
new file mode 100644
index 0000000..523751f
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go
@@ -0,0 +1,236 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ChaCha20 implements the core ChaCha20 function as specified
+// in https://tools.ietf.org/html/rfc7539#section-2.3.
+package chacha20
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+
+	"golang.org/x/crypto/internal/subtle"
+)
+
+// assert that *Cipher implements cipher.Stream
+var _ cipher.Stream = (*Cipher)(nil)
+
+// Cipher is a stateful instance of ChaCha20 using a particular key
+// and nonce. A *Cipher implements the cipher.Stream interface.
+type Cipher struct {
+	key     [8]uint32
+	counter uint32 // incremented after each block
+	nonce   [3]uint32
+	buf     [bufSize]byte // buffer for unused keystream bytes
+	len     int           // number of unused keystream bytes at end of buf
+}
+
+// New creates a new ChaCha20 stream cipher with the given key and nonce.
+// The initial counter value is set to 0.
+func New(key [8]uint32, nonce [3]uint32) *Cipher {
+	return &Cipher{key: key, nonce: nonce}
+}
+
+// XORKeyStream XORs each byte in the given slice with a byte from the
+// cipher's key stream. Dst and src must overlap entirely or not at all.
+//
+// If len(dst) < len(src), XORKeyStream will panic. It is acceptable
+// to pass a dst bigger than src, and in that case, XORKeyStream will
+// only update dst[:len(src)] and will not touch the rest of dst.
+//
+// Multiple calls to XORKeyStream behave as if the concatenation of
+// the src buffers was passed in a single run. That is, Cipher
+// maintains state and does not reset at each XORKeyStream call.
+func (s *Cipher) XORKeyStream(dst, src []byte) {
+	if len(dst) < len(src) {
+		panic("chacha20: output smaller than input")
+	}
+	if subtle.InexactOverlap(dst[:len(src)], src) {
+		panic("chacha20: invalid buffer overlap")
+	}
+
+	// xor src with buffered keystream first
+	if s.len != 0 {
+		buf := s.buf[len(s.buf)-s.len:]
+		if len(src) < len(buf) {
+			buf = buf[:len(src)]
+		}
+		td, ts := dst[:len(buf)], src[:len(buf)] // BCE hint
+		for i, b := range buf {
+			td[i] = ts[i] ^ b
+		}
+		s.len -= len(buf)
+		if s.len != 0 {
+			return
+		}
+		s.buf = [len(s.buf)]byte{} // zero the empty buffer
+		src = src[len(buf):]
+		dst = dst[len(buf):]
+	}
+
+	if len(src) == 0 {
+		return
+	}
+	if haveAsm {
+		s.xorKeyStreamAsm(dst, src)
+		return
+	}
+
+	// set up a 64-byte buffer to pad out the final block if needed
+	// (hoisted out of the main loop to avoid spills)
+	rem := len(src) % 64  // length of final block
+	fin := len(src) - rem // index of final block
+	if rem > 0 {
+		copy(s.buf[len(s.buf)-64:], src[fin:])
+	}
+
+	// qr calculates a quarter round
+	qr := func(a, b, c, d uint32) (uint32, uint32, uint32, uint32) {
+		a += b
+		d ^= a
+		d = (d << 16) | (d >> 16)
+		c += d
+		b ^= c
+		b = (b << 12) | (b >> 20)
+		a += b
+		d ^= a
+		d = (d << 8) | (d >> 24)
+		c += d
+		b ^= c
+		b = (b << 7) | (b >> 25)
+		return a, b, c, d
+	}
+
+	// ChaCha20 constants
+	const (
+		j0 = 0x61707865
+		j1 = 0x3320646e
+		j2 = 0x79622d32
+		j3 = 0x6b206574
+	)
+
+	// pre-calculate most of the first round
+	s1, s5, s9, s13 := qr(j1, s.key[1], s.key[5], s.nonce[0])
+	s2, s6, s10, s14 := qr(j2, s.key[2], s.key[6], s.nonce[1])
+	s3, s7, s11, s15 := qr(j3, s.key[3], s.key[7], s.nonce[2])
+
+	n := len(src)
+	src, dst = src[:n:n], dst[:n:n] // BCE hint
+	for i := 0; i < n; i += 64 {
+		// calculate the remainder of the first round
+		s0, s4, s8, s12 := qr(j0, s.key[0], s.key[4], s.counter)
+
+		// execute the second round
+		x0, x5, x10, x15 := qr(s0, s5, s10, s15)
+		x1, x6, x11, x12 := qr(s1, s6, s11, s12)
+		x2, x7, x8, x13 := qr(s2, s7, s8, s13)
+		x3, x4, x9, x14 := qr(s3, s4, s9, s14)
+
+		// execute the remaining 18 rounds
+		for i := 0; i < 9; i++ {
+			x0, x4, x8, x12 = qr(x0, x4, x8, x12)
+			x1, x5, x9, x13 = qr(x1, x5, x9, x13)
+			x2, x6, x10, x14 = qr(x2, x6, x10, x14)
+			x3, x7, x11, x15 = qr(x3, x7, x11, x15)
+
+			x0, x5, x10, x15 = qr(x0, x5, x10, x15)
+			x1, x6, x11, x12 = qr(x1, x6, x11, x12)
+			x2, x7, x8, x13 = qr(x2, x7, x8, x13)
+			x3, x4, x9, x14 = qr(x3, x4, x9, x14)
+		}
+
+		x0 += j0
+		x1 += j1
+		x2 += j2
+		x3 += j3
+
+		x4 += s.key[0]
+		x5 += s.key[1]
+		x6 += s.key[2]
+		x7 += s.key[3]
+		x8 += s.key[4]
+		x9 += s.key[5]
+		x10 += s.key[6]
+		x11 += s.key[7]
+
+		x12 += s.counter
+		x13 += s.nonce[0]
+		x14 += s.nonce[1]
+		x15 += s.nonce[2]
+
+		// increment the counter
+		s.counter += 1
+		if s.counter == 0 {
+			panic("chacha20: counter overflow")
+		}
+
+		// pad to 64 bytes if needed
+		in, out := src[i:], dst[i:]
+		if i == fin {
+			// src[fin:] has already been copied into s.buf before
+			// the main loop
+			in, out = s.buf[len(s.buf)-64:], s.buf[len(s.buf)-64:]
+		}
+		in, out = in[:64], out[:64] // BCE hint
+
+		// XOR the key stream with the source and write out the result
+		xor(out[0:], in[0:], x0)
+		xor(out[4:], in[4:], x1)
+		xor(out[8:], in[8:], x2)
+		xor(out[12:], in[12:], x3)
+		xor(out[16:], in[16:], x4)
+		xor(out[20:], in[20:], x5)
+		xor(out[24:], in[24:], x6)
+		xor(out[28:], in[28:], x7)
+		xor(out[32:], in[32:], x8)
+		xor(out[36:], in[36:], x9)
+		xor(out[40:], in[40:], x10)
+		xor(out[44:], in[44:], x11)
+		xor(out[48:], in[48:], x12)
+		xor(out[52:], in[52:], x13)
+		xor(out[56:], in[56:], x14)
+		xor(out[60:], in[60:], x15)
+	}
+	// copy any trailing bytes out of the buffer and into dst
+	if rem != 0 {
+		s.len = 64 - rem
+		copy(dst[fin:], s.buf[len(s.buf)-64:])
+	}
+}
+
+// Advance discards bytes in the key stream until the next 64 byte block
+// boundary is reached and updates the counter accordingly. If the key
+// stream is already at a block boundary no bytes will be discarded and
+// the counter will be unchanged.
+func (s *Cipher) Advance() {
+	s.len -= s.len % 64
+	if s.len == 0 {
+		s.buf = [len(s.buf)]byte{}
+	}
+}
+
+// XORKeyStream crypts bytes from in to out using the given key and counters.
+// In and out must overlap entirely or not at all. Counter contains the raw
+// ChaCha20 counter bytes (i.e. block counter followed by nonce).
+func XORKeyStream(out, in []byte, counter *[16]byte, key *[32]byte) {
+	s := Cipher{
+		key: [8]uint32{
+			binary.LittleEndian.Uint32(key[0:4]),
+			binary.LittleEndian.Uint32(key[4:8]),
+			binary.LittleEndian.Uint32(key[8:12]),
+			binary.LittleEndian.Uint32(key[12:16]),
+			binary.LittleEndian.Uint32(key[16:20]),
+			binary.LittleEndian.Uint32(key[20:24]),
+			binary.LittleEndian.Uint32(key[24:28]),
+			binary.LittleEndian.Uint32(key[28:32]),
+		},
+		nonce: [3]uint32{
+			binary.LittleEndian.Uint32(counter[4:8]),
+			binary.LittleEndian.Uint32(counter[8:12]),
+			binary.LittleEndian.Uint32(counter[12:16]),
+		},
+		counter: binary.LittleEndian.Uint32(counter[0:4]),
+	}
+	s.XORKeyStream(out, in)
+}
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/chacha_noasm.go b/vendor/golang.org/x/crypto/internal/chacha20/chacha_noasm.go
new file mode 100644
index 0000000..91520d1
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_noasm.go
@@ -0,0 +1,16 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !s390x gccgo appengine
+
+package chacha20
+
+const (
+	bufSize = 64
+	haveAsm = false
+)
+
+func (*Cipher) xorKeyStreamAsm(dst, src []byte) {
+	panic("not implemented")
+}
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/chacha_s390x.go b/vendor/golang.org/x/crypto/internal/chacha20/chacha_s390x.go
new file mode 100644
index 0000000..0c1c671
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_s390x.go
@@ -0,0 +1,30 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,!gccgo,!appengine
+
+package chacha20
+
+var haveAsm = hasVectorFacility()
+
+const bufSize = 256
+
+// hasVectorFacility reports whether the machine supports the vector
+// facility (vx).
+// Implementation in asm_s390x.s.
+func hasVectorFacility() bool
+
+// xorKeyStreamVX is an assembly implementation of XORKeyStream. It must only
+// be called when the vector facility is available.
+// Implementation in asm_s390x.s.
+//go:noescape
+func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32, buf *[256]byte, len *int)
+
+func (c *Cipher) xorKeyStreamAsm(dst, src []byte) {
+	xorKeyStreamVX(dst, src, &c.key, &c.nonce, &c.counter, &c.buf, &c.len)
+}
+
+// EXRL targets, DO NOT CALL!
+func mvcSrcToBuf()
+func mvcBufToDst()
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/xor.go b/vendor/golang.org/x/crypto/internal/chacha20/xor.go
new file mode 100644
index 0000000..9c5ba0b
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/xor.go
@@ -0,0 +1,43 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found src the LICENSE file.
+
+package chacha20
+
+import (
+	"runtime"
+)
+
+// Platforms that have fast unaligned 32-bit little endian accesses.
+const unaligned = runtime.GOARCH == "386" ||
+	runtime.GOARCH == "amd64" ||
+	runtime.GOARCH == "arm64" ||
+	runtime.GOARCH == "ppc64le" ||
+	runtime.GOARCH == "s390x"
+
+// xor reads a little endian uint32 from src, XORs it with u and
+// places the result in little endian byte order in dst.
+func xor(dst, src []byte, u uint32) {
+	_, _ = src[3], dst[3] // eliminate bounds checks
+	if unaligned {
+		// The compiler should optimize this code into
+		// 32-bit unaligned little endian loads and stores.
+		// TODO: delete once the compiler does a reliably
+		// good job with the generic code below.
+		// See issue #25111 for more details.
+		v := uint32(src[0])
+		v |= uint32(src[1]) << 8
+		v |= uint32(src[2]) << 16
+		v |= uint32(src[3]) << 24
+		v ^= u
+		dst[0] = byte(v)
+		dst[1] = byte(v >> 8)
+		dst[2] = byte(v >> 16)
+		dst[3] = byte(v >> 24)
+	} else {
+		dst[0] = src[0] ^ byte(u)
+		dst[1] = src[1] ^ byte(u>>8)
+		dst[2] = src[2] ^ byte(u>>16)
+		dst[3] = src[3] ^ byte(u>>24)
+	}
+}
diff --git a/vendor/golang.org/x/crypto/internal/subtle/aliasing.go b/vendor/golang.org/x/crypto/internal/subtle/aliasing.go
new file mode 100644
index 0000000..f38797b
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/subtle/aliasing.go
@@ -0,0 +1,32 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+
+// Package subtle implements functions that are often useful in cryptographic
+// code but require careful thought to use correctly.
+package subtle // import "golang.org/x/crypto/internal/subtle"
+
+import "unsafe"
+
+// AnyOverlap reports whether x and y share memory at any (not necessarily
+// corresponding) index. The memory beyond the slice length is ignored.
+func AnyOverlap(x, y []byte) bool {
+	return len(x) > 0 && len(y) > 0 &&
+		uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
+		uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
+}
+
+// InexactOverlap reports whether x and y share memory at any non-corresponding
+// index. The memory beyond the slice length is ignored. Note that x and y can
+// have different lengths and still not have any inexact overlap.
+//
+// InexactOverlap can be used to implement the requirements of the crypto/cipher
+// AEAD, Block, BlockMode and Stream interfaces.
+func InexactOverlap(x, y []byte) bool {
+	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
+		return false
+	}
+	return AnyOverlap(x, y)
+}
diff --git a/vendor/golang.org/x/crypto/internal/subtle/aliasing_appengine.go b/vendor/golang.org/x/crypto/internal/subtle/aliasing_appengine.go
new file mode 100644
index 0000000..0cc4a8a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/subtle/aliasing_appengine.go
@@ -0,0 +1,35 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine
+
+// Package subtle implements functions that are often useful in cryptographic
+// code but require careful thought to use correctly.
+package subtle // import "golang.org/x/crypto/internal/subtle"
+
+// This is the Google App Engine standard variant based on reflect
+// because the unsafe package and cgo are disallowed.
+
+import "reflect"
+
+// AnyOverlap reports whether x and y share memory at any (not necessarily
+// corresponding) index. The memory beyond the slice length is ignored.
+func AnyOverlap(x, y []byte) bool {
+	return len(x) > 0 && len(y) > 0 &&
+		reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() &&
+		reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer()
+}
+
+// InexactOverlap reports whether x and y share memory at any non-corresponding
+// index. The memory beyond the slice length is ignored. Note that x and y can
+// have different lengths and still not have any inexact overlap.
+//
+// InexactOverlap can be used to implement the requirements of the crypto/cipher
+// AEAD, Block, BlockMode and Stream interfaces.
+func InexactOverlap(x, y []byte) bool {
+	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
+		return false
+	}
+	return AnyOverlap(x, y)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/poly1305.go b/vendor/golang.org/x/crypto/poly1305/poly1305.go
new file mode 100644
index 0000000..f562fa5
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/poly1305.go
@@ -0,0 +1,33 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package poly1305 implements Poly1305 one-time message authentication code as
+specified in https://cr.yp.to/mac/poly1305-20050329.pdf.
+
+Poly1305 is a fast, one-time authentication function. It is infeasible for an
+attacker to generate an authenticator for a message without the key. However, a
+key must only be used for a single message. Authenticating two different
+messages with the same key allows an attacker to forge authenticators for other
+messages with the same key.
+
+Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was
+used with a fixed key in order to generate one-time keys from an nonce.
+However, in this package AES isn't used and the one-time key is specified
+directly.
+*/
+package poly1305 // import "golang.org/x/crypto/poly1305"
+
+import "crypto/subtle"
+
+// TagSize is the size, in bytes, of a poly1305 authenticator.
+const TagSize = 16
+
+// Verify returns true if mac is a valid authenticator for m with the given
+// key.
+func Verify(mac *[16]byte, m []byte, key *[32]byte) bool {
+	var tmp [16]byte
+	Sum(&tmp, m, key)
+	return subtle.ConstantTimeCompare(tmp[:], mac[:]) == 1
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_amd64.go b/vendor/golang.org/x/crypto/poly1305/sum_amd64.go
new file mode 100644
index 0000000..4dd72fe
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_amd64.go
@@ -0,0 +1,22 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build amd64,!gccgo,!appengine
+
+package poly1305
+
+// This function is implemented in sum_amd64.s
+//go:noescape
+func poly1305(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
+
+// Sum generates an authenticator for m using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[16]byte, m []byte, key *[32]byte) {
+	var mPtr *byte
+	if len(m) > 0 {
+		mPtr = &m[0]
+	}
+	poly1305(out, mPtr, uint64(len(m)), key)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_amd64.s b/vendor/golang.org/x/crypto/poly1305/sum_amd64.s
new file mode 100644
index 0000000..2edae63
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_amd64.s
@@ -0,0 +1,125 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build amd64,!gccgo,!appengine
+
+#include "textflag.h"
+
+#define POLY1305_ADD(msg, h0, h1, h2) \
+	ADDQ 0(msg), h0;  \
+	ADCQ 8(msg), h1;  \
+	ADCQ $1, h2;      \
+	LEAQ 16(msg), msg
+
+#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3) \
+	MOVQ  r0, AX;                  \
+	MULQ  h0;                      \
+	MOVQ  AX, t0;                  \
+	MOVQ  DX, t1;                  \
+	MOVQ  r0, AX;                  \
+	MULQ  h1;                      \
+	ADDQ  AX, t1;                  \
+	ADCQ  $0, DX;                  \
+	MOVQ  r0, t2;                  \
+	IMULQ h2, t2;                  \
+	ADDQ  DX, t2;                  \
+	                               \
+	MOVQ  r1, AX;                  \
+	MULQ  h0;                      \
+	ADDQ  AX, t1;                  \
+	ADCQ  $0, DX;                  \
+	MOVQ  DX, h0;                  \
+	MOVQ  r1, t3;                  \
+	IMULQ h2, t3;                  \
+	MOVQ  r1, AX;                  \
+	MULQ  h1;                      \
+	ADDQ  AX, t2;                  \
+	ADCQ  DX, t3;                  \
+	ADDQ  h0, t2;                  \
+	ADCQ  $0, t3;                  \
+	                               \
+	MOVQ  t0, h0;                  \
+	MOVQ  t1, h1;                  \
+	MOVQ  t2, h2;                  \
+	ANDQ  $3, h2;                  \
+	MOVQ  t2, t0;                  \
+	ANDQ  $0xFFFFFFFFFFFFFFFC, t0; \
+	ADDQ  t0, h0;                  \
+	ADCQ  t3, h1;                  \
+	ADCQ  $0, h2;                  \
+	SHRQ  $2, t3, t2;              \
+	SHRQ  $2, t3;                  \
+	ADDQ  t2, h0;                  \
+	ADCQ  t3, h1;                  \
+	ADCQ  $0, h2
+
+DATA ·poly1305Mask<>+0x00(SB)/8, $0x0FFFFFFC0FFFFFFF
+DATA ·poly1305Mask<>+0x08(SB)/8, $0x0FFFFFFC0FFFFFFC
+GLOBL ·poly1305Mask<>(SB), RODATA, $16
+
+// func poly1305(out *[16]byte, m *byte, mlen uint64, key *[32]key)
+TEXT ·poly1305(SB), $0-32
+	MOVQ out+0(FP), DI
+	MOVQ m+8(FP), SI
+	MOVQ mlen+16(FP), R15
+	MOVQ key+24(FP), AX
+
+	MOVQ 0(AX), R11
+	MOVQ 8(AX), R12
+	ANDQ ·poly1305Mask<>(SB), R11   // r0
+	ANDQ ·poly1305Mask<>+8(SB), R12 // r1
+	XORQ R8, R8                    // h0
+	XORQ R9, R9                    // h1
+	XORQ R10, R10                  // h2
+
+	CMPQ R15, $16
+	JB   bytes_between_0_and_15
+
+loop:
+	POLY1305_ADD(SI, R8, R9, R10)
+
+multiply:
+	POLY1305_MUL(R8, R9, R10, R11, R12, BX, CX, R13, R14)
+	SUBQ $16, R15
+	CMPQ R15, $16
+	JAE  loop
+
+bytes_between_0_and_15:
+	TESTQ R15, R15
+	JZ    done
+	MOVQ  $1, BX
+	XORQ  CX, CX
+	XORQ  R13, R13
+	ADDQ  R15, SI
+
+flush_buffer:
+	SHLQ $8, BX, CX
+	SHLQ $8, BX
+	MOVB -1(SI), R13
+	XORQ R13, BX
+	DECQ SI
+	DECQ R15
+	JNZ  flush_buffer
+
+	ADDQ BX, R8
+	ADCQ CX, R9
+	ADCQ $0, R10
+	MOVQ $16, R15
+	JMP  multiply
+
+done:
+	MOVQ    R8, AX
+	MOVQ    R9, BX
+	SUBQ    $0xFFFFFFFFFFFFFFFB, AX
+	SBBQ    $0xFFFFFFFFFFFFFFFF, BX
+	SBBQ    $3, R10
+	CMOVQCS R8, AX
+	CMOVQCS R9, BX
+	MOVQ    key+24(FP), R8
+	ADDQ    16(R8), AX
+	ADCQ    24(R8), BX
+
+	MOVQ AX, 0(DI)
+	MOVQ BX, 8(DI)
+	RET
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_arm.go b/vendor/golang.org/x/crypto/poly1305/sum_arm.go
new file mode 100644
index 0000000..5dc321c
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_arm.go
@@ -0,0 +1,22 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build arm,!gccgo,!appengine,!nacl
+
+package poly1305
+
+// This function is implemented in sum_arm.s
+//go:noescape
+func poly1305_auth_armv6(out *[16]byte, m *byte, mlen uint32, key *[32]byte)
+
+// Sum generates an authenticator for m using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[16]byte, m []byte, key *[32]byte) {
+	var mPtr *byte
+	if len(m) > 0 {
+		mPtr = &m[0]
+	}
+	poly1305_auth_armv6(out, mPtr, uint32(len(m)), key)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_arm.s b/vendor/golang.org/x/crypto/poly1305/sum_arm.s
new file mode 100644
index 0000000..f70b4ac
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_arm.s
@@ -0,0 +1,427 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build arm,!gccgo,!appengine,!nacl
+
+#include "textflag.h"
+
+// This code was translated into a form compatible with 5a from the public
+// domain source by Andrew Moon: github.com/floodyberry/poly1305-opt/blob/master/app/extensions/poly1305.
+
+DATA ·poly1305_init_constants_armv6<>+0x00(SB)/4, $0x3ffffff
+DATA ·poly1305_init_constants_armv6<>+0x04(SB)/4, $0x3ffff03
+DATA ·poly1305_init_constants_armv6<>+0x08(SB)/4, $0x3ffc0ff
+DATA ·poly1305_init_constants_armv6<>+0x0c(SB)/4, $0x3f03fff
+DATA ·poly1305_init_constants_armv6<>+0x10(SB)/4, $0x00fffff
+GLOBL ·poly1305_init_constants_armv6<>(SB), 8, $20
+
+// Warning: the linker may use R11 to synthesize certain instructions. Please
+// take care and verify that no synthetic instructions use it.
+
+TEXT poly1305_init_ext_armv6<>(SB), NOSPLIT, $0
+	// Needs 16 bytes of stack and 64 bytes of space pointed to by R0.  (It
+	// might look like it's only 60 bytes of space but the final four bytes
+	// will be written by another function.) We need to skip over four
+	// bytes of stack because that's saving the value of 'g'.
+	ADD       $4, R13, R8
+	MOVM.IB   [R4-R7], (R8)
+	MOVM.IA.W (R1), [R2-R5]
+	MOVW      $·poly1305_init_constants_armv6<>(SB), R7
+	MOVW      R2, R8
+	MOVW      R2>>26, R9
+	MOVW      R3>>20, g
+	MOVW      R4>>14, R11
+	MOVW      R5>>8, R12
+	ORR       R3<<6, R9, R9
+	ORR       R4<<12, g, g
+	ORR       R5<<18, R11, R11
+	MOVM.IA   (R7), [R2-R6]
+	AND       R8, R2, R2
+	AND       R9, R3, R3
+	AND       g, R4, R4
+	AND       R11, R5, R5
+	AND       R12, R6, R6
+	MOVM.IA.W [R2-R6], (R0)
+	EOR       R2, R2, R2
+	EOR       R3, R3, R3
+	EOR       R4, R4, R4
+	EOR       R5, R5, R5
+	EOR       R6, R6, R6
+	MOVM.IA.W [R2-R6], (R0)
+	MOVM.IA.W (R1), [R2-R5]
+	MOVM.IA   [R2-R6], (R0)
+	ADD       $20, R13, R0
+	MOVM.DA   (R0), [R4-R7]
+	RET
+
+#define MOVW_UNALIGNED(Rsrc, Rdst, Rtmp, offset) \
+	MOVBU (offset+0)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+0)(Rdst); \
+	MOVBU (offset+1)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+1)(Rdst); \
+	MOVBU (offset+2)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+2)(Rdst); \
+	MOVBU (offset+3)(Rsrc), Rtmp; \
+	MOVBU Rtmp, (offset+3)(Rdst)
+
+TEXT poly1305_blocks_armv6<>(SB), NOSPLIT, $0
+	// Needs 24 bytes of stack for saved registers and then 88 bytes of
+	// scratch space after that. We assume that 24 bytes at (R13) have
+	// already been used: four bytes for the link register saved in the
+	// prelude of poly1305_auth_armv6, four bytes for saving the value of g
+	// in that function and 16 bytes of scratch space used around
+	// poly1305_finish_ext_armv6_skip1.
+	ADD     $24, R13, R12
+	MOVM.IB [R4-R8, R14], (R12)
+	MOVW    R0, 88(R13)
+	MOVW    R1, 92(R13)
+	MOVW    R2, 96(R13)
+	MOVW    R1, R14
+	MOVW    R2, R12
+	MOVW    56(R0), R8
+	WORD    $0xe1180008                // TST R8, R8 not working see issue 5921
+	EOR     R6, R6, R6
+	MOVW.EQ $(1<<24), R6
+	MOVW    R6, 84(R13)
+	ADD     $116, R13, g
+	MOVM.IA (R0), [R0-R9]
+	MOVM.IA [R0-R4], (g)
+	CMP     $16, R12
+	BLO     poly1305_blocks_armv6_done
+
+poly1305_blocks_armv6_mainloop:
+	WORD    $0xe31e0003                            // TST R14, #3 not working see issue 5921
+	BEQ     poly1305_blocks_armv6_mainloop_aligned
+	ADD     $100, R13, g
+	MOVW_UNALIGNED(R14, g, R0, 0)
+	MOVW_UNALIGNED(R14, g, R0, 4)
+	MOVW_UNALIGNED(R14, g, R0, 8)
+	MOVW_UNALIGNED(R14, g, R0, 12)
+	MOVM.IA (g), [R0-R3]
+	ADD     $16, R14
+	B       poly1305_blocks_armv6_mainloop_loaded
+
+poly1305_blocks_armv6_mainloop_aligned:
+	MOVM.IA.W (R14), [R0-R3]
+
+poly1305_blocks_armv6_mainloop_loaded:
+	MOVW    R0>>26, g
+	MOVW    R1>>20, R11
+	MOVW    R2>>14, R12
+	MOVW    R14, 92(R13)
+	MOVW    R3>>8, R4
+	ORR     R1<<6, g, g
+	ORR     R2<<12, R11, R11
+	ORR     R3<<18, R12, R12
+	BIC     $0xfc000000, R0, R0
+	BIC     $0xfc000000, g, g
+	MOVW    84(R13), R3
+	BIC     $0xfc000000, R11, R11
+	BIC     $0xfc000000, R12, R12
+	ADD     R0, R5, R5
+	ADD     g, R6, R6
+	ORR     R3, R4, R4
+	ADD     R11, R7, R7
+	ADD     $116, R13, R14
+	ADD     R12, R8, R8
+	ADD     R4, R9, R9
+	MOVM.IA (R14), [R0-R4]
+	MULLU   R4, R5, (R11, g)
+	MULLU   R3, R5, (R14, R12)
+	MULALU  R3, R6, (R11, g)
+	MULALU  R2, R6, (R14, R12)
+	MULALU  R2, R7, (R11, g)
+	MULALU  R1, R7, (R14, R12)
+	ADD     R4<<2, R4, R4
+	ADD     R3<<2, R3, R3
+	MULALU  R1, R8, (R11, g)
+	MULALU  R0, R8, (R14, R12)
+	MULALU  R0, R9, (R11, g)
+	MULALU  R4, R9, (R14, R12)
+	MOVW    g, 76(R13)
+	MOVW    R11, 80(R13)
+	MOVW    R12, 68(R13)
+	MOVW    R14, 72(R13)
+	MULLU   R2, R5, (R11, g)
+	MULLU   R1, R5, (R14, R12)
+	MULALU  R1, R6, (R11, g)
+	MULALU  R0, R6, (R14, R12)
+	MULALU  R0, R7, (R11, g)
+	MULALU  R4, R7, (R14, R12)
+	ADD     R2<<2, R2, R2
+	ADD     R1<<2, R1, R1
+	MULALU  R4, R8, (R11, g)
+	MULALU  R3, R8, (R14, R12)
+	MULALU  R3, R9, (R11, g)
+	MULALU  R2, R9, (R14, R12)
+	MOVW    g, 60(R13)
+	MOVW    R11, 64(R13)
+	MOVW    R12, 52(R13)
+	MOVW    R14, 56(R13)
+	MULLU   R0, R5, (R11, g)
+	MULALU  R4, R6, (R11, g)
+	MULALU  R3, R7, (R11, g)
+	MULALU  R2, R8, (R11, g)
+	MULALU  R1, R9, (R11, g)
+	ADD     $52, R13, R0
+	MOVM.IA (R0), [R0-R7]
+	MOVW    g>>26, R12
+	MOVW    R4>>26, R14
+	ORR     R11<<6, R12, R12
+	ORR     R5<<6, R14, R14
+	BIC     $0xfc000000, g, g
+	BIC     $0xfc000000, R4, R4
+	ADD.S   R12, R0, R0
+	ADC     $0, R1, R1
+	ADD.S   R14, R6, R6
+	ADC     $0, R7, R7
+	MOVW    R0>>26, R12
+	MOVW    R6>>26, R14
+	ORR     R1<<6, R12, R12
+	ORR     R7<<6, R14, R14
+	BIC     $0xfc000000, R0, R0
+	BIC     $0xfc000000, R6, R6
+	ADD     R14<<2, R14, R14
+	ADD.S   R12, R2, R2
+	ADC     $0, R3, R3
+	ADD     R14, g, g
+	MOVW    R2>>26, R12
+	MOVW    g>>26, R14
+	ORR     R3<<6, R12, R12
+	BIC     $0xfc000000, g, R5
+	BIC     $0xfc000000, R2, R7
+	ADD     R12, R4, R4
+	ADD     R14, R0, R0
+	MOVW    R4>>26, R12
+	BIC     $0xfc000000, R4, R8
+	ADD     R12, R6, R9
+	MOVW    96(R13), R12
+	MOVW    92(R13), R14
+	MOVW    R0, R6
+	CMP     $32, R12
+	SUB     $16, R12, R12
+	MOVW    R12, 96(R13)
+	BHS     poly1305_blocks_armv6_mainloop
+
+poly1305_blocks_armv6_done:
+	MOVW    88(R13), R12
+	MOVW    R5, 20(R12)
+	MOVW    R6, 24(R12)
+	MOVW    R7, 28(R12)
+	MOVW    R8, 32(R12)
+	MOVW    R9, 36(R12)
+	ADD     $48, R13, R0
+	MOVM.DA (R0), [R4-R8, R14]
+	RET
+
+#define MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp) \
+	MOVBU.P 1(Rsrc), Rtmp; \
+	MOVBU.P Rtmp, 1(Rdst); \
+	MOVBU.P 1(Rsrc), Rtmp; \
+	MOVBU.P Rtmp, 1(Rdst)
+
+#define MOVWP_UNALIGNED(Rsrc, Rdst, Rtmp) \
+	MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp); \
+	MOVHUP_UNALIGNED(Rsrc, Rdst, Rtmp)
+
+// func poly1305_auth_armv6(out *[16]byte, m *byte, mlen uint32, key *[32]key)
+TEXT ·poly1305_auth_armv6(SB), $196-16
+	// The value 196, just above, is the sum of 64 (the size of the context
+	// structure) and 132 (the amount of stack needed).
+	//
+	// At this point, the stack pointer (R13) has been moved down. It
+	// points to the saved link register and there's 196 bytes of free
+	// space above it.
+	//
+	// The stack for this function looks like:
+	//
+	// +---------------------
+	// |
+	// | 64 bytes of context structure
+	// |
+	// +---------------------
+	// |
+	// | 112 bytes for poly1305_blocks_armv6
+	// |
+	// +---------------------
+	// | 16 bytes of final block, constructed at
+	// | poly1305_finish_ext_armv6_skip8
+	// +---------------------
+	// | four bytes of saved 'g'
+	// +---------------------
+	// | lr, saved by prelude    <- R13 points here
+	// +---------------------
+	MOVW g, 4(R13)
+
+	MOVW out+0(FP), R4
+	MOVW m+4(FP), R5
+	MOVW mlen+8(FP), R6
+	MOVW key+12(FP), R7
+
+	ADD  $136, R13, R0 // 136 = 4 + 4 + 16 + 112
+	MOVW R7, R1
+
+	// poly1305_init_ext_armv6 will write to the stack from R13+4, but
+	// that's ok because none of the other values have been written yet.
+	BL    poly1305_init_ext_armv6<>(SB)
+	BIC.S $15, R6, R2
+	BEQ   poly1305_auth_armv6_noblocks
+	ADD   $136, R13, R0
+	MOVW  R5, R1
+	ADD   R2, R5, R5
+	SUB   R2, R6, R6
+	BL    poly1305_blocks_armv6<>(SB)
+
+poly1305_auth_armv6_noblocks:
+	ADD  $136, R13, R0
+	MOVW R5, R1
+	MOVW R6, R2
+	MOVW R4, R3
+
+	MOVW  R0, R5
+	MOVW  R1, R6
+	MOVW  R2, R7
+	MOVW  R3, R8
+	AND.S R2, R2, R2
+	BEQ   poly1305_finish_ext_armv6_noremaining
+	EOR   R0, R0
+	ADD   $8, R13, R9                           // 8 = offset to 16 byte scratch space
+	MOVW  R0, (R9)
+	MOVW  R0, 4(R9)
+	MOVW  R0, 8(R9)
+	MOVW  R0, 12(R9)
+	WORD  $0xe3110003                           // TST R1, #3 not working see issue 5921
+	BEQ   poly1305_finish_ext_armv6_aligned
+	WORD  $0xe3120008                           // TST R2, #8 not working see issue 5921
+	BEQ   poly1305_finish_ext_armv6_skip8
+	MOVWP_UNALIGNED(R1, R9, g)
+	MOVWP_UNALIGNED(R1, R9, g)
+
+poly1305_finish_ext_armv6_skip8:
+	WORD $0xe3120004                     // TST $4, R2 not working see issue 5921
+	BEQ  poly1305_finish_ext_armv6_skip4
+	MOVWP_UNALIGNED(R1, R9, g)
+
+poly1305_finish_ext_armv6_skip4:
+	WORD $0xe3120002                     // TST $2, R2 not working see issue 5921
+	BEQ  poly1305_finish_ext_armv6_skip2
+	MOVHUP_UNALIGNED(R1, R9, g)
+	B    poly1305_finish_ext_armv6_skip2
+
+poly1305_finish_ext_armv6_aligned:
+	WORD      $0xe3120008                             // TST R2, #8 not working see issue 5921
+	BEQ       poly1305_finish_ext_armv6_skip8_aligned
+	MOVM.IA.W (R1), [g-R11]
+	MOVM.IA.W [g-R11], (R9)
+
+poly1305_finish_ext_armv6_skip8_aligned:
+	WORD   $0xe3120004                             // TST $4, R2 not working see issue 5921
+	BEQ    poly1305_finish_ext_armv6_skip4_aligned
+	MOVW.P 4(R1), g
+	MOVW.P g, 4(R9)
+
+poly1305_finish_ext_armv6_skip4_aligned:
+	WORD    $0xe3120002                     // TST $2, R2 not working see issue 5921
+	BEQ     poly1305_finish_ext_armv6_skip2
+	MOVHU.P 2(R1), g
+	MOVH.P  g, 2(R9)
+
+poly1305_finish_ext_armv6_skip2:
+	WORD    $0xe3120001                     // TST $1, R2 not working see issue 5921
+	BEQ     poly1305_finish_ext_armv6_skip1
+	MOVBU.P 1(R1), g
+	MOVBU.P g, 1(R9)
+
+poly1305_finish_ext_armv6_skip1:
+	MOVW  $1, R11
+	MOVBU R11, 0(R9)
+	MOVW  R11, 56(R5)
+	MOVW  R5, R0
+	ADD   $8, R13, R1
+	MOVW  $16, R2
+	BL    poly1305_blocks_armv6<>(SB)
+
+poly1305_finish_ext_armv6_noremaining:
+	MOVW      20(R5), R0
+	MOVW      24(R5), R1
+	MOVW      28(R5), R2
+	MOVW      32(R5), R3
+	MOVW      36(R5), R4
+	MOVW      R4>>26, R12
+	BIC       $0xfc000000, R4, R4
+	ADD       R12<<2, R12, R12
+	ADD       R12, R0, R0
+	MOVW      R0>>26, R12
+	BIC       $0xfc000000, R0, R0
+	ADD       R12, R1, R1
+	MOVW      R1>>26, R12
+	BIC       $0xfc000000, R1, R1
+	ADD       R12, R2, R2
+	MOVW      R2>>26, R12
+	BIC       $0xfc000000, R2, R2
+	ADD       R12, R3, R3
+	MOVW      R3>>26, R12
+	BIC       $0xfc000000, R3, R3
+	ADD       R12, R4, R4
+	ADD       $5, R0, R6
+	MOVW      R6>>26, R12
+	BIC       $0xfc000000, R6, R6
+	ADD       R12, R1, R7
+	MOVW      R7>>26, R12
+	BIC       $0xfc000000, R7, R7
+	ADD       R12, R2, g
+	MOVW      g>>26, R12
+	BIC       $0xfc000000, g, g
+	ADD       R12, R3, R11
+	MOVW      $-(1<<26), R12
+	ADD       R11>>26, R12, R12
+	BIC       $0xfc000000, R11, R11
+	ADD       R12, R4, R9
+	MOVW      R9>>31, R12
+	SUB       $1, R12
+	AND       R12, R6, R6
+	AND       R12, R7, R7
+	AND       R12, g, g
+	AND       R12, R11, R11
+	AND       R12, R9, R9
+	MVN       R12, R12
+	AND       R12, R0, R0
+	AND       R12, R1, R1
+	AND       R12, R2, R2
+	AND       R12, R3, R3
+	AND       R12, R4, R4
+	ORR       R6, R0, R0
+	ORR       R7, R1, R1
+	ORR       g, R2, R2
+	ORR       R11, R3, R3
+	ORR       R9, R4, R4
+	ORR       R1<<26, R0, R0
+	MOVW      R1>>6, R1
+	ORR       R2<<20, R1, R1
+	MOVW      R2>>12, R2
+	ORR       R3<<14, R2, R2
+	MOVW      R3>>18, R3
+	ORR       R4<<8, R3, R3
+	MOVW      40(R5), R6
+	MOVW      44(R5), R7
+	MOVW      48(R5), g
+	MOVW      52(R5), R11
+	ADD.S     R6, R0, R0
+	ADC.S     R7, R1, R1
+	ADC.S     g, R2, R2
+	ADC.S     R11, R3, R3
+	MOVM.IA   [R0-R3], (R8)
+	MOVW      R5, R12
+	EOR       R0, R0, R0
+	EOR       R1, R1, R1
+	EOR       R2, R2, R2
+	EOR       R3, R3, R3
+	EOR       R4, R4, R4
+	EOR       R5, R5, R5
+	EOR       R6, R6, R6
+	EOR       R7, R7, R7
+	MOVM.IA.W [R0-R7], (R12)
+	MOVM.IA   [R0-R7], (R12)
+	MOVW      4(R13), g
+	RET
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_noasm.go b/vendor/golang.org/x/crypto/poly1305/sum_noasm.go
new file mode 100644
index 0000000..751eec5
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_noasm.go
@@ -0,0 +1,14 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,!go1.11 !arm,!amd64,!s390x gccgo appengine nacl
+
+package poly1305
+
+// Sum generates an authenticator for msg using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[TagSize]byte, msg []byte, key *[32]byte) {
+	sumGeneric(out, msg, key)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_ref.go b/vendor/golang.org/x/crypto/poly1305/sum_ref.go
new file mode 100644
index 0000000..c4d59bd
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_ref.go
@@ -0,0 +1,139 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poly1305
+
+import "encoding/binary"
+
+// sumGeneric generates an authenticator for msg using a one-time key and
+// puts the 16-byte result into out. This is the generic implementation of
+// Sum and should be called if no assembly implementation is available.
+func sumGeneric(out *[TagSize]byte, msg []byte, key *[32]byte) {
+	var (
+		h0, h1, h2, h3, h4 uint32 // the hash accumulators
+		r0, r1, r2, r3, r4 uint64 // the r part of the key
+	)
+
+	r0 = uint64(binary.LittleEndian.Uint32(key[0:]) & 0x3ffffff)
+	r1 = uint64((binary.LittleEndian.Uint32(key[3:]) >> 2) & 0x3ffff03)
+	r2 = uint64((binary.LittleEndian.Uint32(key[6:]) >> 4) & 0x3ffc0ff)
+	r3 = uint64((binary.LittleEndian.Uint32(key[9:]) >> 6) & 0x3f03fff)
+	r4 = uint64((binary.LittleEndian.Uint32(key[12:]) >> 8) & 0x00fffff)
+
+	R1, R2, R3, R4 := r1*5, r2*5, r3*5, r4*5
+
+	for len(msg) >= TagSize {
+		// h += msg
+		h0 += binary.LittleEndian.Uint32(msg[0:]) & 0x3ffffff
+		h1 += (binary.LittleEndian.Uint32(msg[3:]) >> 2) & 0x3ffffff
+		h2 += (binary.LittleEndian.Uint32(msg[6:]) >> 4) & 0x3ffffff
+		h3 += (binary.LittleEndian.Uint32(msg[9:]) >> 6) & 0x3ffffff
+		h4 += (binary.LittleEndian.Uint32(msg[12:]) >> 8) | (1 << 24)
+
+		// h *= r
+		d0 := (uint64(h0) * r0) + (uint64(h1) * R4) + (uint64(h2) * R3) + (uint64(h3) * R2) + (uint64(h4) * R1)
+		d1 := (d0 >> 26) + (uint64(h0) * r1) + (uint64(h1) * r0) + (uint64(h2) * R4) + (uint64(h3) * R3) + (uint64(h4) * R2)
+		d2 := (d1 >> 26) + (uint64(h0) * r2) + (uint64(h1) * r1) + (uint64(h2) * r0) + (uint64(h3) * R4) + (uint64(h4) * R3)
+		d3 := (d2 >> 26) + (uint64(h0) * r3) + (uint64(h1) * r2) + (uint64(h2) * r1) + (uint64(h3) * r0) + (uint64(h4) * R4)
+		d4 := (d3 >> 26) + (uint64(h0) * r4) + (uint64(h1) * r3) + (uint64(h2) * r2) + (uint64(h3) * r1) + (uint64(h4) * r0)
+
+		// h %= p
+		h0 = uint32(d0) & 0x3ffffff
+		h1 = uint32(d1) & 0x3ffffff
+		h2 = uint32(d2) & 0x3ffffff
+		h3 = uint32(d3) & 0x3ffffff
+		h4 = uint32(d4) & 0x3ffffff
+
+		h0 += uint32(d4>>26) * 5
+		h1 += h0 >> 26
+		h0 = h0 & 0x3ffffff
+
+		msg = msg[TagSize:]
+	}
+
+	if len(msg) > 0 {
+		var block [TagSize]byte
+		off := copy(block[:], msg)
+		block[off] = 0x01
+
+		// h += msg
+		h0 += binary.LittleEndian.Uint32(block[0:]) & 0x3ffffff
+		h1 += (binary.LittleEndian.Uint32(block[3:]) >> 2) & 0x3ffffff
+		h2 += (binary.LittleEndian.Uint32(block[6:]) >> 4) & 0x3ffffff
+		h3 += (binary.LittleEndian.Uint32(block[9:]) >> 6) & 0x3ffffff
+		h4 += (binary.LittleEndian.Uint32(block[12:]) >> 8)
+
+		// h *= r
+		d0 := (uint64(h0) * r0) + (uint64(h1) * R4) + (uint64(h2) * R3) + (uint64(h3) * R2) + (uint64(h4) * R1)
+		d1 := (d0 >> 26) + (uint64(h0) * r1) + (uint64(h1) * r0) + (uint64(h2) * R4) + (uint64(h3) * R3) + (uint64(h4) * R2)
+		d2 := (d1 >> 26) + (uint64(h0) * r2) + (uint64(h1) * r1) + (uint64(h2) * r0) + (uint64(h3) * R4) + (uint64(h4) * R3)
+		d3 := (d2 >> 26) + (uint64(h0) * r3) + (uint64(h1) * r2) + (uint64(h2) * r1) + (uint64(h3) * r0) + (uint64(h4) * R4)
+		d4 := (d3 >> 26) + (uint64(h0) * r4) + (uint64(h1) * r3) + (uint64(h2) * r2) + (uint64(h3) * r1) + (uint64(h4) * r0)
+
+		// h %= p
+		h0 = uint32(d0) & 0x3ffffff
+		h1 = uint32(d1) & 0x3ffffff
+		h2 = uint32(d2) & 0x3ffffff
+		h3 = uint32(d3) & 0x3ffffff
+		h4 = uint32(d4) & 0x3ffffff
+
+		h0 += uint32(d4>>26) * 5
+		h1 += h0 >> 26
+		h0 = h0 & 0x3ffffff
+	}
+
+	// h %= p reduction
+	h2 += h1 >> 26
+	h1 &= 0x3ffffff
+	h3 += h2 >> 26
+	h2 &= 0x3ffffff
+	h4 += h3 >> 26
+	h3 &= 0x3ffffff
+	h0 += 5 * (h4 >> 26)
+	h4 &= 0x3ffffff
+	h1 += h0 >> 26
+	h0 &= 0x3ffffff
+
+	// h - p
+	t0 := h0 + 5
+	t1 := h1 + (t0 >> 26)
+	t2 := h2 + (t1 >> 26)
+	t3 := h3 + (t2 >> 26)
+	t4 := h4 + (t3 >> 26) - (1 << 26)
+	t0 &= 0x3ffffff
+	t1 &= 0x3ffffff
+	t2 &= 0x3ffffff
+	t3 &= 0x3ffffff
+
+	// select h if h < p else h - p
+	t_mask := (t4 >> 31) - 1
+	h_mask := ^t_mask
+	h0 = (h0 & h_mask) | (t0 & t_mask)
+	h1 = (h1 & h_mask) | (t1 & t_mask)
+	h2 = (h2 & h_mask) | (t2 & t_mask)
+	h3 = (h3 & h_mask) | (t3 & t_mask)
+	h4 = (h4 & h_mask) | (t4 & t_mask)
+
+	// h %= 2^128
+	h0 |= h1 << 26
+	h1 = ((h1 >> 6) | (h2 << 20))
+	h2 = ((h2 >> 12) | (h3 << 14))
+	h3 = ((h3 >> 18) | (h4 << 8))
+
+	// s: the s part of the key
+	// tag = (h + s) % (2^128)
+	t := uint64(h0) + uint64(binary.LittleEndian.Uint32(key[16:]))
+	h0 = uint32(t)
+	t = uint64(h1) + uint64(binary.LittleEndian.Uint32(key[20:])) + (t >> 32)
+	h1 = uint32(t)
+	t = uint64(h2) + uint64(binary.LittleEndian.Uint32(key[24:])) + (t >> 32)
+	h2 = uint32(t)
+	t = uint64(h3) + uint64(binary.LittleEndian.Uint32(key[28:])) + (t >> 32)
+	h3 = uint32(t)
+
+	binary.LittleEndian.PutUint32(out[0:], h0)
+	binary.LittleEndian.PutUint32(out[4:], h1)
+	binary.LittleEndian.PutUint32(out[8:], h2)
+	binary.LittleEndian.PutUint32(out[12:], h3)
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_s390x.go b/vendor/golang.org/x/crypto/poly1305/sum_s390x.go
new file mode 100644
index 0000000..7a266ce
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_s390x.go
@@ -0,0 +1,49 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,go1.11,!gccgo,!appengine
+
+package poly1305
+
+// hasVectorFacility reports whether the machine supports
+// the vector facility (vx).
+func hasVectorFacility() bool
+
+// hasVMSLFacility reports whether the machine supports
+// Vector Multiply Sum Logical (VMSL).
+func hasVMSLFacility() bool
+
+var hasVX = hasVectorFacility()
+var hasVMSL = hasVMSLFacility()
+
+// poly1305vx is an assembly implementation of Poly1305 that uses vector
+// instructions. It must only be called if the vector facility (vx) is
+// available.
+//go:noescape
+func poly1305vx(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
+
+// poly1305vmsl is an assembly implementation of Poly1305 that uses vector
+// instructions, including VMSL. It must only be called if the vector facility (vx) is
+// available and if VMSL is supported.
+//go:noescape
+func poly1305vmsl(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
+
+// Sum generates an authenticator for m using a one-time key and puts the
+// 16-byte result into out. Authenticating two different messages with the same
+// key allows an attacker to forge messages at will.
+func Sum(out *[16]byte, m []byte, key *[32]byte) {
+	if hasVX {
+		var mPtr *byte
+		if len(m) > 0 {
+			mPtr = &m[0]
+		}
+		if hasVMSL && len(m) > 256 {
+			poly1305vmsl(out, mPtr, uint64(len(m)), key)
+		} else {
+			poly1305vx(out, mPtr, uint64(len(m)), key)
+		}
+	} else {
+		sumGeneric(out, m, key)
+	}
+}
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_s390x.s b/vendor/golang.org/x/crypto/poly1305/sum_s390x.s
new file mode 100644
index 0000000..356c07a
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_s390x.s
@@ -0,0 +1,400 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,go1.11,!gccgo,!appengine
+
+#include "textflag.h"
+
+// Implementation of Poly1305 using the vector facility (vx).
+
+// constants
+#define MOD26 V0
+#define EX0   V1
+#define EX1   V2
+#define EX2   V3
+
+// temporaries
+#define T_0 V4
+#define T_1 V5
+#define T_2 V6
+#define T_3 V7
+#define T_4 V8
+
+// key (r)
+#define R_0  V9
+#define R_1  V10
+#define R_2  V11
+#define R_3  V12
+#define R_4  V13
+#define R5_1 V14
+#define R5_2 V15
+#define R5_3 V16
+#define R5_4 V17
+#define RSAVE_0 R5
+#define RSAVE_1 R6
+#define RSAVE_2 R7
+#define RSAVE_3 R8
+#define RSAVE_4 R9
+#define R5SAVE_1 V28
+#define R5SAVE_2 V29
+#define R5SAVE_3 V30
+#define R5SAVE_4 V31
+
+// message block
+#define F_0 V18
+#define F_1 V19
+#define F_2 V20
+#define F_3 V21
+#define F_4 V22
+
+// accumulator
+#define H_0 V23
+#define H_1 V24
+#define H_2 V25
+#define H_3 V26
+#define H_4 V27
+
+GLOBL ·keyMask<>(SB), RODATA, $16
+DATA ·keyMask<>+0(SB)/8, $0xffffff0ffcffff0f
+DATA ·keyMask<>+8(SB)/8, $0xfcffff0ffcffff0f
+
+GLOBL ·bswapMask<>(SB), RODATA, $16
+DATA ·bswapMask<>+0(SB)/8, $0x0f0e0d0c0b0a0908
+DATA ·bswapMask<>+8(SB)/8, $0x0706050403020100
+
+GLOBL ·constants<>(SB), RODATA, $64
+// MOD26
+DATA ·constants<>+0(SB)/8, $0x3ffffff
+DATA ·constants<>+8(SB)/8, $0x3ffffff
+// EX0
+DATA ·constants<>+16(SB)/8, $0x0006050403020100
+DATA ·constants<>+24(SB)/8, $0x1016151413121110
+// EX1
+DATA ·constants<>+32(SB)/8, $0x060c0b0a09080706
+DATA ·constants<>+40(SB)/8, $0x161c1b1a19181716
+// EX2
+DATA ·constants<>+48(SB)/8, $0x0d0d0d0d0d0f0e0d
+DATA ·constants<>+56(SB)/8, $0x1d1d1d1d1d1f1e1d
+
+// h = (f*g) % (2**130-5) [partial reduction]
+#define MULTIPLY(f0, f1, f2, f3, f4, g0, g1, g2, g3, g4, g51, g52, g53, g54, h0, h1, h2, h3, h4) \
+	VMLOF  f0, g0, h0        \
+	VMLOF  f0, g1, h1        \
+	VMLOF  f0, g2, h2        \
+	VMLOF  f0, g3, h3        \
+	VMLOF  f0, g4, h4        \
+	VMLOF  f1, g54, T_0      \
+	VMLOF  f1, g0, T_1       \
+	VMLOF  f1, g1, T_2       \
+	VMLOF  f1, g2, T_3       \
+	VMLOF  f1, g3, T_4       \
+	VMALOF f2, g53, h0, h0   \
+	VMALOF f2, g54, h1, h1   \
+	VMALOF f2, g0, h2, h2    \
+	VMALOF f2, g1, h3, h3    \
+	VMALOF f2, g2, h4, h4    \
+	VMALOF f3, g52, T_0, T_0 \
+	VMALOF f3, g53, T_1, T_1 \
+	VMALOF f3, g54, T_2, T_2 \
+	VMALOF f3, g0, T_3, T_3  \
+	VMALOF f3, g1, T_4, T_4  \
+	VMALOF f4, g51, h0, h0   \
+	VMALOF f4, g52, h1, h1   \
+	VMALOF f4, g53, h2, h2   \
+	VMALOF f4, g54, h3, h3   \
+	VMALOF f4, g0, h4, h4    \
+	VAG    T_0, h0, h0       \
+	VAG    T_1, h1, h1       \
+	VAG    T_2, h2, h2       \
+	VAG    T_3, h3, h3       \
+	VAG    T_4, h4, h4
+
+// carry h0->h1 h3->h4, h1->h2 h4->h0, h0->h1 h2->h3, h3->h4
+#define REDUCE(h0, h1, h2, h3, h4) \
+	VESRLG $26, h0, T_0  \
+	VESRLG $26, h3, T_1  \
+	VN     MOD26, h0, h0 \
+	VN     MOD26, h3, h3 \
+	VAG    T_0, h1, h1   \
+	VAG    T_1, h4, h4   \
+	VESRLG $26, h1, T_2  \
+	VESRLG $26, h4, T_3  \
+	VN     MOD26, h1, h1 \
+	VN     MOD26, h4, h4 \
+	VESLG  $2, T_3, T_4  \
+	VAG    T_3, T_4, T_4 \
+	VAG    T_2, h2, h2   \
+	VAG    T_4, h0, h0   \
+	VESRLG $26, h2, T_0  \
+	VESRLG $26, h0, T_1  \
+	VN     MOD26, h2, h2 \
+	VN     MOD26, h0, h0 \
+	VAG    T_0, h3, h3   \
+	VAG    T_1, h1, h1   \
+	VESRLG $26, h3, T_2  \
+	VN     MOD26, h3, h3 \
+	VAG    T_2, h4, h4
+
+// expand in0 into d[0] and in1 into d[1]
+#define EXPAND(in0, in1, d0, d1, d2, d3, d4) \
+	VGBM   $0x0707, d1       \ // d1=tmp
+	VPERM  in0, in1, EX2, d4 \
+	VPERM  in0, in1, EX0, d0 \
+	VPERM  in0, in1, EX1, d2 \
+	VN     d1, d4, d4        \
+	VESRLG $26, d0, d1       \
+	VESRLG $30, d2, d3       \
+	VESRLG $4, d2, d2        \
+	VN     MOD26, d0, d0     \
+	VN     MOD26, d1, d1     \
+	VN     MOD26, d2, d2     \
+	VN     MOD26, d3, d3
+
+// pack h4:h0 into h1:h0 (no carry)
+#define PACK(h0, h1, h2, h3, h4) \
+	VESLG $26, h1, h1  \
+	VESLG $26, h3, h3  \
+	VO    h0, h1, h0   \
+	VO    h2, h3, h2   \
+	VESLG $4, h2, h2   \
+	VLEIB $7, $48, h1  \
+	VSLB  h1, h2, h2   \
+	VO    h0, h2, h0   \
+	VLEIB $7, $104, h1 \
+	VSLB  h1, h4, h3   \
+	VO    h3, h0, h0   \
+	VLEIB $7, $24, h1  \
+	VSRLB h1, h4, h1
+
+// if h > 2**130-5 then h -= 2**130-5
+#define MOD(h0, h1, t0, t1, t2) \
+	VZERO t0          \
+	VLEIG $1, $5, t0  \
+	VACCQ h0, t0, t1  \
+	VAQ   h0, t0, t0  \
+	VONE  t2          \
+	VLEIG $1, $-4, t2 \
+	VAQ   t2, t1, t1  \
+	VACCQ h1, t1, t1  \
+	VONE  t2          \
+	VAQ   t2, t1, t1  \
+	VN    h0, t1, t2  \
+	VNC   t0, t1, t1  \
+	VO    t1, t2, h0
+
+// func poly1305vx(out *[16]byte, m *byte, mlen uint64, key *[32]key)
+TEXT ·poly1305vx(SB), $0-32
+	// This code processes up to 2 blocks (32 bytes) per iteration
+	// using the algorithm described in:
+	// NEON crypto, Daniel J. Bernstein & Peter Schwabe
+	// https://cryptojedi.org/papers/neoncrypto-20120320.pdf
+	LMG out+0(FP), R1, R4 // R1=out, R2=m, R3=mlen, R4=key
+
+	// load MOD26, EX0, EX1 and EX2
+	MOVD $·constants<>(SB), R5
+	VLM  (R5), MOD26, EX2
+
+	// setup r
+	VL   (R4), T_0
+	MOVD $·keyMask<>(SB), R6
+	VL   (R6), T_1
+	VN   T_0, T_1, T_0
+	EXPAND(T_0, T_0, R_0, R_1, R_2, R_3, R_4)
+
+	// setup r*5
+	VLEIG $0, $5, T_0
+	VLEIG $1, $5, T_0
+
+	// store r (for final block)
+	VMLOF T_0, R_1, R5SAVE_1
+	VMLOF T_0, R_2, R5SAVE_2
+	VMLOF T_0, R_3, R5SAVE_3
+	VMLOF T_0, R_4, R5SAVE_4
+	VLGVG $0, R_0, RSAVE_0
+	VLGVG $0, R_1, RSAVE_1
+	VLGVG $0, R_2, RSAVE_2
+	VLGVG $0, R_3, RSAVE_3
+	VLGVG $0, R_4, RSAVE_4
+
+	// skip r**2 calculation
+	CMPBLE R3, $16, skip
+
+	// calculate r**2
+	MULTIPLY(R_0, R_1, R_2, R_3, R_4, R_0, R_1, R_2, R_3, R_4, R5SAVE_1, R5SAVE_2, R5SAVE_3, R5SAVE_4, H_0, H_1, H_2, H_3, H_4)
+	REDUCE(H_0, H_1, H_2, H_3, H_4)
+	VLEIG $0, $5, T_0
+	VLEIG $1, $5, T_0
+	VMLOF T_0, H_1, R5_1
+	VMLOF T_0, H_2, R5_2
+	VMLOF T_0, H_3, R5_3
+	VMLOF T_0, H_4, R5_4
+	VLR   H_0, R_0
+	VLR   H_1, R_1
+	VLR   H_2, R_2
+	VLR   H_3, R_3
+	VLR   H_4, R_4
+
+	// initialize h
+	VZERO H_0
+	VZERO H_1
+	VZERO H_2
+	VZERO H_3
+	VZERO H_4
+
+loop:
+	CMPBLE R3, $32, b2
+	VLM    (R2), T_0, T_1
+	SUB    $32, R3
+	MOVD   $32(R2), R2
+	EXPAND(T_0, T_1, F_0, F_1, F_2, F_3, F_4)
+	VLEIB  $4, $1, F_4
+	VLEIB  $12, $1, F_4
+
+multiply:
+	VAG    H_0, F_0, F_0
+	VAG    H_1, F_1, F_1
+	VAG    H_2, F_2, F_2
+	VAG    H_3, F_3, F_3
+	VAG    H_4, F_4, F_4
+	MULTIPLY(F_0, F_1, F_2, F_3, F_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, H_0, H_1, H_2, H_3, H_4)
+	REDUCE(H_0, H_1, H_2, H_3, H_4)
+	CMPBNE R3, $0, loop
+
+finish:
+	// sum vectors
+	VZERO  T_0
+	VSUMQG H_0, T_0, H_0
+	VSUMQG H_1, T_0, H_1
+	VSUMQG H_2, T_0, H_2
+	VSUMQG H_3, T_0, H_3
+	VSUMQG H_4, T_0, H_4
+
+	// h may be >= 2*(2**130-5) so we need to reduce it again
+	REDUCE(H_0, H_1, H_2, H_3, H_4)
+
+	// carry h1->h4
+	VESRLG $26, H_1, T_1
+	VN     MOD26, H_1, H_1
+	VAQ    T_1, H_2, H_2
+	VESRLG $26, H_2, T_2
+	VN     MOD26, H_2, H_2
+	VAQ    T_2, H_3, H_3
+	VESRLG $26, H_3, T_3
+	VN     MOD26, H_3, H_3
+	VAQ    T_3, H_4, H_4
+
+	// h is now < 2*(2**130-5)
+	// pack h into h1 (hi) and h0 (lo)
+	PACK(H_0, H_1, H_2, H_3, H_4)
+
+	// if h > 2**130-5 then h -= 2**130-5
+	MOD(H_0, H_1, T_0, T_1, T_2)
+
+	// h += s
+	MOVD  $·bswapMask<>(SB), R5
+	VL    (R5), T_1
+	VL    16(R4), T_0
+	VPERM T_0, T_0, T_1, T_0    // reverse bytes (to big)
+	VAQ   T_0, H_0, H_0
+	VPERM H_0, H_0, T_1, H_0    // reverse bytes (to little)
+	VST   H_0, (R1)
+
+	RET
+
+b2:
+	CMPBLE R3, $16, b1
+
+	// 2 blocks remaining
+	SUB    $17, R3
+	VL     (R2), T_0
+	VLL    R3, 16(R2), T_1
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, T_1
+	EXPAND(T_0, T_1, F_0, F_1, F_2, F_3, F_4)
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $12, $1, F_4
+	VLEIB  $4, $1, F_4
+
+	// setup [r²,r]
+	VLVGG $1, RSAVE_0, R_0
+	VLVGG $1, RSAVE_1, R_1
+	VLVGG $1, RSAVE_2, R_2
+	VLVGG $1, RSAVE_3, R_3
+	VLVGG $1, RSAVE_4, R_4
+	VPDI  $0, R5_1, R5SAVE_1, R5_1
+	VPDI  $0, R5_2, R5SAVE_2, R5_2
+	VPDI  $0, R5_3, R5SAVE_3, R5_3
+	VPDI  $0, R5_4, R5SAVE_4, R5_4
+
+	MOVD $0, R3
+	BR   multiply
+
+skip:
+	VZERO H_0
+	VZERO H_1
+	VZERO H_2
+	VZERO H_3
+	VZERO H_4
+
+	CMPBEQ R3, $0, finish
+
+b1:
+	// 1 block remaining
+	SUB    $1, R3
+	VLL    R3, (R2), T_0
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, T_0
+	VZERO  T_1
+	EXPAND(T_0, T_1, F_0, F_1, F_2, F_3, F_4)
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $4, $1, F_4
+	VLEIG  $1, $1, R_0
+	VZERO  R_1
+	VZERO  R_2
+	VZERO  R_3
+	VZERO  R_4
+	VZERO  R5_1
+	VZERO  R5_2
+	VZERO  R5_3
+	VZERO  R5_4
+
+	// setup [r, 1]
+	VLVGG $0, RSAVE_0, R_0
+	VLVGG $0, RSAVE_1, R_1
+	VLVGG $0, RSAVE_2, R_2
+	VLVGG $0, RSAVE_3, R_3
+	VLVGG $0, RSAVE_4, R_4
+	VPDI  $0, R5SAVE_1, R5_1, R5_1
+	VPDI  $0, R5SAVE_2, R5_2, R5_2
+	VPDI  $0, R5SAVE_3, R5_3, R5_3
+	VPDI  $0, R5SAVE_4, R5_4, R5_4
+
+	MOVD $0, R3
+	BR   multiply
+
+TEXT ·hasVectorFacility(SB), NOSPLIT, $24-1
+	MOVD  $x-24(SP), R1
+	XC    $24, 0(R1), 0(R1) // clear the storage
+	MOVD  $2, R0            // R0 is the number of double words stored -1
+	WORD  $0xB2B01000       // STFLE 0(R1)
+	XOR   R0, R0            // reset the value of R0
+	MOVBZ z-8(SP), R1
+	AND   $0x40, R1
+	BEQ   novector
+
+vectorinstalled:
+	// check if the vector instruction has been enabled
+	VLEIB  $0, $0xF, V16
+	VLGVB  $0, V16, R1
+	CMPBNE R1, $0xF, novector
+	MOVB   $1, ret+0(FP)      // have vx
+	RET
+
+novector:
+	MOVB $0, ret+0(FP) // no vx
+	RET
diff --git a/vendor/golang.org/x/crypto/poly1305/sum_vmsl_s390x.s b/vendor/golang.org/x/crypto/poly1305/sum_vmsl_s390x.s
new file mode 100644
index 0000000..e548020
--- /dev/null
+++ b/vendor/golang.org/x/crypto/poly1305/sum_vmsl_s390x.s
@@ -0,0 +1,931 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build s390x,go1.11,!gccgo,!appengine
+
+#include "textflag.h"
+
+// Implementation of Poly1305 using the vector facility (vx) and the VMSL instruction.
+
+// constants
+#define EX0   V1
+#define EX1   V2
+#define EX2   V3
+
+// temporaries
+#define T_0 V4
+#define T_1 V5
+#define T_2 V6
+#define T_3 V7
+#define T_4 V8
+#define T_5 V9
+#define T_6 V10
+#define T_7 V11
+#define T_8 V12
+#define T_9 V13
+#define T_10 V14
+
+// r**2 & r**4
+#define R_0  V15
+#define R_1  V16
+#define R_2  V17
+#define R5_1 V18
+#define R5_2 V19
+// key (r)
+#define RSAVE_0 R7
+#define RSAVE_1 R8
+#define RSAVE_2 R9
+#define R5SAVE_1 R10
+#define R5SAVE_2 R11
+
+// message block
+#define M0 V20
+#define M1 V21
+#define M2 V22
+#define M3 V23
+#define M4 V24
+#define M5 V25
+
+// accumulator
+#define H0_0 V26
+#define H1_0 V27
+#define H2_0 V28
+#define H0_1 V29
+#define H1_1 V30
+#define H2_1 V31
+
+GLOBL ·keyMask<>(SB), RODATA, $16
+DATA ·keyMask<>+0(SB)/8, $0xffffff0ffcffff0f
+DATA ·keyMask<>+8(SB)/8, $0xfcffff0ffcffff0f
+
+GLOBL ·bswapMask<>(SB), RODATA, $16
+DATA ·bswapMask<>+0(SB)/8, $0x0f0e0d0c0b0a0908
+DATA ·bswapMask<>+8(SB)/8, $0x0706050403020100
+
+GLOBL ·constants<>(SB), RODATA, $48
+// EX0
+DATA ·constants<>+0(SB)/8, $0x18191a1b1c1d1e1f
+DATA ·constants<>+8(SB)/8, $0x0000050403020100
+// EX1
+DATA ·constants<>+16(SB)/8, $0x18191a1b1c1d1e1f
+DATA ·constants<>+24(SB)/8, $0x00000a0908070605
+// EX2
+DATA ·constants<>+32(SB)/8, $0x18191a1b1c1d1e1f
+DATA ·constants<>+40(SB)/8, $0x0000000f0e0d0c0b
+
+GLOBL ·c<>(SB), RODATA, $48
+// EX0
+DATA ·c<>+0(SB)/8, $0x0000050403020100
+DATA ·c<>+8(SB)/8, $0x0000151413121110
+// EX1
+DATA ·c<>+16(SB)/8, $0x00000a0908070605
+DATA ·c<>+24(SB)/8, $0x00001a1918171615
+// EX2
+DATA ·c<>+32(SB)/8, $0x0000000f0e0d0c0b
+DATA ·c<>+40(SB)/8, $0x0000001f1e1d1c1b
+
+GLOBL ·reduce<>(SB), RODATA, $32
+// 44 bit
+DATA ·reduce<>+0(SB)/8, $0x0
+DATA ·reduce<>+8(SB)/8, $0xfffffffffff
+// 42 bit
+DATA ·reduce<>+16(SB)/8, $0x0
+DATA ·reduce<>+24(SB)/8, $0x3ffffffffff
+
+// h = (f*g) % (2**130-5) [partial reduction]
+// uses T_0...T_9 temporary registers
+// input: m02_0, m02_1, m02_2, m13_0, m13_1, m13_2, r_0, r_1, r_2, r5_1, r5_2, m4_0, m4_1, m4_2, m5_0, m5_1, m5_2
+// temp: t0, t1, t2, t3, t4, t5, t6, t7, t8, t9
+// output: m02_0, m02_1, m02_2, m13_0, m13_1, m13_2
+#define MULTIPLY(m02_0, m02_1, m02_2, m13_0, m13_1, m13_2, r_0, r_1, r_2, r5_1, r5_2, m4_0, m4_1, m4_2, m5_0, m5_1, m5_2, t0, t1, t2, t3, t4, t5, t6, t7, t8, t9) \
+	\ // Eliminate the dependency for the last 2 VMSLs
+	VMSLG m02_0, r_2, m4_2, m4_2                       \
+	VMSLG m13_0, r_2, m5_2, m5_2                       \ // 8 VMSLs pipelined
+	VMSLG m02_0, r_0, m4_0, m4_0                       \
+	VMSLG m02_1, r5_2, V0, T_0                         \
+	VMSLG m02_0, r_1, m4_1, m4_1                       \
+	VMSLG m02_1, r_0, V0, T_1                          \
+	VMSLG m02_1, r_1, V0, T_2                          \
+	VMSLG m02_2, r5_1, V0, T_3                         \
+	VMSLG m02_2, r5_2, V0, T_4                         \
+	VMSLG m13_0, r_0, m5_0, m5_0                       \
+	VMSLG m13_1, r5_2, V0, T_5                         \
+	VMSLG m13_0, r_1, m5_1, m5_1                       \
+	VMSLG m13_1, r_0, V0, T_6                          \
+	VMSLG m13_1, r_1, V0, T_7                          \
+	VMSLG m13_2, r5_1, V0, T_8                         \
+	VMSLG m13_2, r5_2, V0, T_9                         \
+	VMSLG m02_2, r_0, m4_2, m4_2                       \
+	VMSLG m13_2, r_0, m5_2, m5_2                       \
+	VAQ   m4_0, T_0, m02_0                             \
+	VAQ   m4_1, T_1, m02_1                             \
+	VAQ   m5_0, T_5, m13_0                             \
+	VAQ   m5_1, T_6, m13_1                             \
+	VAQ   m02_0, T_3, m02_0                            \
+	VAQ   m02_1, T_4, m02_1                            \
+	VAQ   m13_0, T_8, m13_0                            \
+	VAQ   m13_1, T_9, m13_1                            \
+	VAQ   m4_2, T_2, m02_2                             \
+	VAQ   m5_2, T_7, m13_2                             \
+
+// SQUARE uses three limbs of r and r_2*5 to output square of r
+// uses T_1, T_5 and T_7 temporary registers
+// input: r_0, r_1, r_2, r5_2
+// temp: TEMP0, TEMP1, TEMP2
+// output: p0, p1, p2
+#define SQUARE(r_0, r_1, r_2, r5_2, p0, p1, p2, TEMP0, TEMP1, TEMP2) \
+	VMSLG r_0, r_0, p0, p0     \
+	VMSLG r_1, r5_2, V0, TEMP0 \
+	VMSLG r_2, r5_2, p1, p1    \
+	VMSLG r_0, r_1, V0, TEMP1  \
+	VMSLG r_1, r_1, p2, p2     \
+	VMSLG r_0, r_2, V0, TEMP2  \
+	VAQ   TEMP0, p0, p0        \
+	VAQ   TEMP1, p1, p1        \
+	VAQ   TEMP2, p2, p2        \
+	VAQ   TEMP0, p0, p0        \
+	VAQ   TEMP1, p1, p1        \
+	VAQ   TEMP2, p2, p2        \
+
+// carry h0->h1->h2->h0 || h3->h4->h5->h3
+// uses T_2, T_4, T_5, T_7, T_8, T_9
+//       t6,  t7,  t8,  t9, t10, t11
+// input: h0, h1, h2, h3, h4, h5
+// temp: t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11
+// output: h0, h1, h2, h3, h4, h5
+#define REDUCE(h0, h1, h2, h3, h4, h5, t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11) \
+	VLM    (R12), t6, t7  \ // 44 and 42 bit clear mask
+	VLEIB  $7, $0x28, t10 \ // 5 byte shift mask
+	VREPIB $4, t8         \ // 4 bit shift mask
+	VREPIB $2, t11        \ // 2 bit shift mask
+	VSRLB  t10, h0, t0    \ // h0 byte shift
+	VSRLB  t10, h1, t1    \ // h1 byte shift
+	VSRLB  t10, h2, t2    \ // h2 byte shift
+	VSRLB  t10, h3, t3    \ // h3 byte shift
+	VSRLB  t10, h4, t4    \ // h4 byte shift
+	VSRLB  t10, h5, t5    \ // h5 byte shift
+	VSRL   t8, t0, t0     \ // h0 bit shift
+	VSRL   t8, t1, t1     \ // h2 bit shift
+	VSRL   t11, t2, t2    \ // h2 bit shift
+	VSRL   t8, t3, t3     \ // h3 bit shift
+	VSRL   t8, t4, t4     \ // h4 bit shift
+	VESLG  $2, t2, t9     \ // h2 carry x5
+	VSRL   t11, t5, t5    \ // h5 bit shift
+	VN     t6, h0, h0     \ // h0 clear carry
+	VAQ    t2, t9, t2     \ // h2 carry x5
+	VESLG  $2, t5, t9     \ // h5 carry x5
+	VN     t6, h1, h1     \ // h1 clear carry
+	VN     t7, h2, h2     \ // h2 clear carry
+	VAQ    t5, t9, t5     \ // h5 carry x5
+	VN     t6, h3, h3     \ // h3 clear carry
+	VN     t6, h4, h4     \ // h4 clear carry
+	VN     t7, h5, h5     \ // h5 clear carry
+	VAQ    t0, h1, h1     \ // h0->h1
+	VAQ    t3, h4, h4     \ // h3->h4
+	VAQ    t1, h2, h2     \ // h1->h2
+	VAQ    t4, h5, h5     \ // h4->h5
+	VAQ    t2, h0, h0     \ // h2->h0
+	VAQ    t5, h3, h3     \ // h5->h3
+	VREPG  $1, t6, t6     \ // 44 and 42 bit masks across both halves
+	VREPG  $1, t7, t7     \
+	VSLDB  $8, h0, h0, h0 \ // set up [h0/1/2, h3/4/5]
+	VSLDB  $8, h1, h1, h1 \
+	VSLDB  $8, h2, h2, h2 \
+	VO     h0, h3, h3     \
+	VO     h1, h4, h4     \
+	VO     h2, h5, h5     \
+	VESRLG $44, h3, t0    \ // 44 bit shift right
+	VESRLG $44, h4, t1    \
+	VESRLG $42, h5, t2    \
+	VN     t6, h3, h3     \ // clear carry bits
+	VN     t6, h4, h4     \
+	VN     t7, h5, h5     \
+	VESLG  $2, t2, t9     \ // multiply carry by 5
+	VAQ    t9, t2, t2     \
+	VAQ    t0, h4, h4     \
+	VAQ    t1, h5, h5     \
+	VAQ    t2, h3, h3     \
+
+// carry h0->h1->h2->h0
+// input: h0, h1, h2
+// temp: t0, t1, t2, t3, t4, t5, t6, t7, t8
+// output: h0, h1, h2
+#define REDUCE2(h0, h1, h2, t0, t1, t2, t3, t4, t5, t6, t7, t8) \
+	VLEIB  $7, $0x28, t3 \ // 5 byte shift mask
+	VREPIB $4, t4        \ // 4 bit shift mask
+	VREPIB $2, t7        \ // 2 bit shift mask
+	VGBM   $0x003F, t5   \ // mask to clear carry bits
+	VSRLB  t3, h0, t0    \
+	VSRLB  t3, h1, t1    \
+	VSRLB  t3, h2, t2    \
+	VESRLG $4, t5, t5    \ // 44 bit clear mask
+	VSRL   t4, t0, t0    \
+	VSRL   t4, t1, t1    \
+	VSRL   t7, t2, t2    \
+	VESRLG $2, t5, t6    \ // 42 bit clear mask
+	VESLG  $2, t2, t8    \
+	VAQ    t8, t2, t2    \
+	VN     t5, h0, h0    \
+	VN     t5, h1, h1    \
+	VN     t6, h2, h2    \
+	VAQ    t0, h1, h1    \
+	VAQ    t1, h2, h2    \
+	VAQ    t2, h0, h0    \
+	VSRLB  t3, h0, t0    \
+	VSRLB  t3, h1, t1    \
+	VSRLB  t3, h2, t2    \
+	VSRL   t4, t0, t0    \
+	VSRL   t4, t1, t1    \
+	VSRL   t7, t2, t2    \
+	VN     t5, h0, h0    \
+	VN     t5, h1, h1    \
+	VESLG  $2, t2, t8    \
+	VN     t6, h2, h2    \
+	VAQ    t0, h1, h1    \
+	VAQ    t8, t2, t2    \
+	VAQ    t1, h2, h2    \
+	VAQ    t2, h0, h0    \
+
+// expands two message blocks into the lower halfs of the d registers
+// moves the contents of the d registers into upper halfs
+// input: in1, in2, d0, d1, d2, d3, d4, d5
+// temp: TEMP0, TEMP1, TEMP2, TEMP3
+// output: d0, d1, d2, d3, d4, d5
+#define EXPACC(in1, in2, d0, d1, d2, d3, d4, d5, TEMP0, TEMP1, TEMP2, TEMP3) \
+	VGBM   $0xff3f, TEMP0      \
+	VGBM   $0xff1f, TEMP1      \
+	VESLG  $4, d1, TEMP2       \
+	VESLG  $4, d4, TEMP3       \
+	VESRLG $4, TEMP0, TEMP0    \
+	VPERM  in1, d0, EX0, d0    \
+	VPERM  in2, d3, EX0, d3    \
+	VPERM  in1, d2, EX2, d2    \
+	VPERM  in2, d5, EX2, d5    \
+	VPERM  in1, TEMP2, EX1, d1 \
+	VPERM  in2, TEMP3, EX1, d4 \
+	VN     TEMP0, d0, d0       \
+	VN     TEMP0, d3, d3       \
+	VESRLG $4, d1, d1          \
+	VESRLG $4, d4, d4          \
+	VN     TEMP1, d2, d2       \
+	VN     TEMP1, d5, d5       \
+	VN     TEMP0, d1, d1       \
+	VN     TEMP0, d4, d4       \
+
+// expands one message block into the lower halfs of the d registers
+// moves the contents of the d registers into upper halfs
+// input: in, d0, d1, d2
+// temp: TEMP0, TEMP1, TEMP2
+// output: d0, d1, d2
+#define EXPACC2(in, d0, d1, d2, TEMP0, TEMP1, TEMP2) \
+	VGBM   $0xff3f, TEMP0     \
+	VESLG  $4, d1, TEMP2      \
+	VGBM   $0xff1f, TEMP1     \
+	VPERM  in, d0, EX0, d0    \
+	VESRLG $4, TEMP0, TEMP0   \
+	VPERM  in, d2, EX2, d2    \
+	VPERM  in, TEMP2, EX1, d1 \
+	VN     TEMP0, d0, d0      \
+	VN     TEMP1, d2, d2      \
+	VESRLG $4, d1, d1         \
+	VN     TEMP0, d1, d1      \
+
+// pack h2:h0 into h1:h0 (no carry)
+// input: h0, h1, h2
+// output: h0, h1, h2
+#define PACK(h0, h1, h2) \
+	VMRLG  h1, h2, h2  \ // copy h1 to upper half h2
+	VESLG  $44, h1, h1 \ // shift limb 1 44 bits, leaving 20
+	VO     h0, h1, h0  \ // combine h0 with 20 bits from limb 1
+	VESRLG $20, h2, h1 \ // put top 24 bits of limb 1 into h1
+	VLEIG  $1, $0, h1  \ // clear h2 stuff from lower half of h1
+	VO     h0, h1, h0  \ // h0 now has 88 bits (limb 0 and 1)
+	VLEIG  $0, $0, h2  \ // clear upper half of h2
+	VESRLG $40, h2, h1 \ // h1 now has upper two bits of result
+	VLEIB  $7, $88, h1 \ // for byte shift (11 bytes)
+	VSLB   h1, h2, h2  \ // shift h2 11 bytes to the left
+	VO     h0, h2, h0  \ // combine h0 with 20 bits from limb 1
+	VLEIG  $0, $0, h1  \ // clear upper half of h1
+
+// if h > 2**130-5 then h -= 2**130-5
+// input: h0, h1
+// temp: t0, t1, t2
+// output: h0
+#define MOD(h0, h1, t0, t1, t2) \
+	VZERO t0          \
+	VLEIG $1, $5, t0  \
+	VACCQ h0, t0, t1  \
+	VAQ   h0, t0, t0  \
+	VONE  t2          \
+	VLEIG $1, $-4, t2 \
+	VAQ   t2, t1, t1  \
+	VACCQ h1, t1, t1  \
+	VONE  t2          \
+	VAQ   t2, t1, t1  \
+	VN    h0, t1, t2  \
+	VNC   t0, t1, t1  \
+	VO    t1, t2, h0  \
+
+// func poly1305vmsl(out *[16]byte, m *byte, mlen uint64, key *[32]key)
+TEXT ·poly1305vmsl(SB), $0-32
+	// This code processes 6 + up to 4 blocks (32 bytes) per iteration
+	// using the algorithm described in:
+	// NEON crypto, Daniel J. Bernstein & Peter Schwabe
+	// https://cryptojedi.org/papers/neoncrypto-20120320.pdf
+	// And as moddified for VMSL as described in
+	// Accelerating Poly1305 Cryptographic Message Authentication on the z14
+	// O'Farrell et al, CASCON 2017, p48-55
+	// https://ibm.ent.box.com/s/jf9gedj0e9d2vjctfyh186shaztavnht
+
+	LMG   out+0(FP), R1, R4 // R1=out, R2=m, R3=mlen, R4=key
+	VZERO V0                // c
+
+	// load EX0, EX1 and EX2
+	MOVD $·constants<>(SB), R5
+	VLM  (R5), EX0, EX2        // c
+
+	// setup r
+	VL    (R4), T_0
+	MOVD  $·keyMask<>(SB), R6
+	VL    (R6), T_1
+	VN    T_0, T_1, T_0
+	VZERO T_2                 // limbs for r
+	VZERO T_3
+	VZERO T_4
+	EXPACC2(T_0, T_2, T_3, T_4, T_1, T_5, T_7)
+
+	// T_2, T_3, T_4: [0, r]
+
+	// setup r*20
+	VLEIG $0, $0, T_0
+	VLEIG $1, $20, T_0       // T_0: [0, 20]
+	VZERO T_5
+	VZERO T_6
+	VMSLG T_0, T_3, T_5, T_5
+	VMSLG T_0, T_4, T_6, T_6
+
+	// store r for final block in GR
+	VLGVG $1, T_2, RSAVE_0  // c
+	VLGVG $1, T_3, RSAVE_1  // c
+	VLGVG $1, T_4, RSAVE_2  // c
+	VLGVG $1, T_5, R5SAVE_1 // c
+	VLGVG $1, T_6, R5SAVE_2 // c
+
+	// initialize h
+	VZERO H0_0
+	VZERO H1_0
+	VZERO H2_0
+	VZERO H0_1
+	VZERO H1_1
+	VZERO H2_1
+
+	// initialize pointer for reduce constants
+	MOVD $·reduce<>(SB), R12
+
+	// calculate r**2 and 20*(r**2)
+	VZERO R_0
+	VZERO R_1
+	VZERO R_2
+	SQUARE(T_2, T_3, T_4, T_6, R_0, R_1, R_2, T_1, T_5, T_7)
+	REDUCE2(R_0, R_1, R_2, M0, M1, M2, M3, M4, R5_1, R5_2, M5, T_1)
+	VZERO R5_1
+	VZERO R5_2
+	VMSLG T_0, R_1, R5_1, R5_1
+	VMSLG T_0, R_2, R5_2, R5_2
+
+	// skip r**4 calculation if 3 blocks or less
+	CMPBLE R3, $48, b4
+
+	// calculate r**4 and 20*(r**4)
+	VZERO T_8
+	VZERO T_9
+	VZERO T_10
+	SQUARE(R_0, R_1, R_2, R5_2, T_8, T_9, T_10, T_1, T_5, T_7)
+	REDUCE2(T_8, T_9, T_10, M0, M1, M2, M3, M4, T_2, T_3, M5, T_1)
+	VZERO T_2
+	VZERO T_3
+	VMSLG T_0, T_9, T_2, T_2
+	VMSLG T_0, T_10, T_3, T_3
+
+	// put r**2 to the right and r**4 to the left of R_0, R_1, R_2
+	VSLDB $8, T_8, T_8, T_8
+	VSLDB $8, T_9, T_9, T_9
+	VSLDB $8, T_10, T_10, T_10
+	VSLDB $8, T_2, T_2, T_2
+	VSLDB $8, T_3, T_3, T_3
+
+	VO T_8, R_0, R_0
+	VO T_9, R_1, R_1
+	VO T_10, R_2, R_2
+	VO T_2, R5_1, R5_1
+	VO T_3, R5_2, R5_2
+
+	CMPBLE R3, $80, load // less than or equal to 5 blocks in message
+
+	// 6(or 5+1) blocks
+	SUB    $81, R3
+	VLM    (R2), M0, M4
+	VLL    R3, 80(R2), M5
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBGE R3, $16, 2(PC)
+	VLVGB  R3, R0, M5
+	MOVD   $96(R2), R2
+	EXPACC(M0, M1, H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_0, T_1, T_2, T_3)
+	EXPACC(M2, M3, H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_0, T_1, T_2, T_3)
+	VLEIB  $2, $1, H2_0
+	VLEIB  $2, $1, H2_1
+	VLEIB  $10, $1, H2_0
+	VLEIB  $10, $1, H2_1
+
+	VZERO  M0
+	VZERO  M1
+	VZERO  M2
+	VZERO  M3
+	VZERO  T_4
+	VZERO  T_10
+	EXPACC(M4, M5, M0, M1, M2, M3, T_4, T_10, T_0, T_1, T_2, T_3)
+	VLR    T_4, M4
+	VLEIB  $10, $1, M2
+	CMPBLT R3, $16, 2(PC)
+	VLEIB  $10, $1, T_10
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, T_10, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, M2, M3, M4, T_4, T_5, T_2, T_7, T_8, T_9)
+	VMRHG  V0, H0_1, H0_0
+	VMRHG  V0, H1_1, H1_0
+	VMRHG  V0, H2_1, H2_0
+	VMRLG  V0, H0_1, H0_1
+	VMRLG  V0, H1_1, H1_1
+	VMRLG  V0, H2_1, H2_1
+
+	SUB    $16, R3
+	CMPBLE R3, $0, square
+
+load:
+	// load EX0, EX1 and EX2
+	MOVD $·c<>(SB), R5
+	VLM  (R5), EX0, EX2
+
+loop:
+	CMPBLE R3, $64, add // b4	// last 4 or less blocks left
+
+	// next 4 full blocks
+	VLM  (R2), M2, M5
+	SUB  $64, R3
+	MOVD $64(R2), R2
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, T_0, T_1, T_3, T_4, T_5, T_2, T_7, T_8, T_9)
+
+	// expacc in-lined to create [m2, m3] limbs
+	VGBM   $0x3f3f, T_0     // 44 bit clear mask
+	VGBM   $0x1f1f, T_1     // 40 bit clear mask
+	VPERM  M2, M3, EX0, T_3
+	VESRLG $4, T_0, T_0     // 44 bit clear mask ready
+	VPERM  M2, M3, EX1, T_4
+	VPERM  M2, M3, EX2, T_5
+	VN     T_0, T_3, T_3
+	VESRLG $4, T_4, T_4
+	VN     T_1, T_5, T_5
+	VN     T_0, T_4, T_4
+	VMRHG  H0_1, T_3, H0_0
+	VMRHG  H1_1, T_4, H1_0
+	VMRHG  H2_1, T_5, H2_0
+	VMRLG  H0_1, T_3, H0_1
+	VMRLG  H1_1, T_4, H1_1
+	VMRLG  H2_1, T_5, H2_1
+	VLEIB  $10, $1, H2_0
+	VLEIB  $10, $1, H2_1
+	VPERM  M4, M5, EX0, T_3
+	VPERM  M4, M5, EX1, T_4
+	VPERM  M4, M5, EX2, T_5
+	VN     T_0, T_3, T_3
+	VESRLG $4, T_4, T_4
+	VN     T_1, T_5, T_5
+	VN     T_0, T_4, T_4
+	VMRHG  V0, T_3, M0
+	VMRHG  V0, T_4, M1
+	VMRHG  V0, T_5, M2
+	VMRLG  V0, T_3, M3
+	VMRLG  V0, T_4, M4
+	VMRLG  V0, T_5, M5
+	VLEIB  $10, $1, M2
+	VLEIB  $10, $1, M5
+
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	CMPBNE R3, $0, loop
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, M3, M4, M5, T_4, T_5, T_2, T_7, T_8, T_9)
+	VMRHG  V0, H0_1, H0_0
+	VMRHG  V0, H1_1, H1_0
+	VMRHG  V0, H2_1, H2_0
+	VMRLG  V0, H0_1, H0_1
+	VMRLG  V0, H1_1, H1_1
+	VMRLG  V0, H2_1, H2_1
+
+	// load EX0, EX1, EX2
+	MOVD $·constants<>(SB), R5
+	VLM  (R5), EX0, EX2
+
+	// sum vectors
+	VAQ H0_0, H0_1, H0_0
+	VAQ H1_0, H1_1, H1_0
+	VAQ H2_0, H2_1, H2_0
+
+	// h may be >= 2*(2**130-5) so we need to reduce it again
+	// M0...M4 are used as temps here
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, T_9, T_10, H0_1, M5)
+
+next:  // carry h1->h2
+	VLEIB  $7, $0x28, T_1
+	VREPIB $4, T_2
+	VGBM   $0x003F, T_3
+	VESRLG $4, T_3
+
+	// byte shift
+	VSRLB T_1, H1_0, T_4
+
+	// bit shift
+	VSRL T_2, T_4, T_4
+
+	// clear h1 carry bits
+	VN T_3, H1_0, H1_0
+
+	// add carry
+	VAQ T_4, H2_0, H2_0
+
+	// h is now < 2*(2**130-5)
+	// pack h into h1 (hi) and h0 (lo)
+	PACK(H0_0, H1_0, H2_0)
+
+	// if h > 2**130-5 then h -= 2**130-5
+	MOD(H0_0, H1_0, T_0, T_1, T_2)
+
+	// h += s
+	MOVD  $·bswapMask<>(SB), R5
+	VL    (R5), T_1
+	VL    16(R4), T_0
+	VPERM T_0, T_0, T_1, T_0    // reverse bytes (to big)
+	VAQ   T_0, H0_0, H0_0
+	VPERM H0_0, H0_0, T_1, H0_0 // reverse bytes (to little)
+	VST   H0_0, (R1)
+	RET
+
+add:
+	// load EX0, EX1, EX2
+	MOVD $·constants<>(SB), R5
+	VLM  (R5), EX0, EX2
+
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, M3, M4, M5, T_4, T_5, T_2, T_7, T_8, T_9)
+	VMRHG  V0, H0_1, H0_0
+	VMRHG  V0, H1_1, H1_0
+	VMRHG  V0, H2_1, H2_0
+	VMRLG  V0, H0_1, H0_1
+	VMRLG  V0, H1_1, H1_1
+	VMRLG  V0, H2_1, H2_1
+	CMPBLE R3, $64, b4
+
+b4:
+	CMPBLE R3, $48, b3 // 3 blocks or less
+
+	// 4(3+1) blocks remaining
+	SUB    $49, R3
+	VLM    (R2), M0, M2
+	VLL    R3, 48(R2), M3
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, M3
+	MOVD   $64(R2), R2
+	EXPACC(M0, M1, H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_0, T_1, T_2, T_3)
+	VLEIB  $10, $1, H2_0
+	VLEIB  $10, $1, H2_1
+	VZERO  M0
+	VZERO  M1
+	VZERO  M4
+	VZERO  M5
+	VZERO  T_4
+	VZERO  T_10
+	EXPACC(M2, M3, M0, M1, M4, M5, T_4, T_10, T_0, T_1, T_2, T_3)
+	VLR    T_4, M2
+	VLEIB  $10, $1, M4
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $10, $1, T_10
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M4, M5, M2, T_10, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, M3, M4, M5, T_4, T_5, T_2, T_7, T_8, T_9)
+	VMRHG  V0, H0_1, H0_0
+	VMRHG  V0, H1_1, H1_0
+	VMRHG  V0, H2_1, H2_0
+	VMRLG  V0, H0_1, H0_1
+	VMRLG  V0, H1_1, H1_1
+	VMRLG  V0, H2_1, H2_1
+	SUB    $16, R3
+	CMPBLE R3, $0, square // this condition must always hold true!
+
+b3:
+	CMPBLE R3, $32, b2
+
+	// 3 blocks remaining
+
+	// setup [r²,r]
+	VSLDB $8, R_0, R_0, R_0
+	VSLDB $8, R_1, R_1, R_1
+	VSLDB $8, R_2, R_2, R_2
+	VSLDB $8, R5_1, R5_1, R5_1
+	VSLDB $8, R5_2, R5_2, R5_2
+
+	VLVGG $1, RSAVE_0, R_0
+	VLVGG $1, RSAVE_1, R_1
+	VLVGG $1, RSAVE_2, R_2
+	VLVGG $1, R5SAVE_1, R5_1
+	VLVGG $1, R5SAVE_2, R5_2
+
+	// setup [h0, h1]
+	VSLDB $8, H0_0, H0_0, H0_0
+	VSLDB $8, H1_0, H1_0, H1_0
+	VSLDB $8, H2_0, H2_0, H2_0
+	VO    H0_1, H0_0, H0_0
+	VO    H1_1, H1_0, H1_0
+	VO    H2_1, H2_0, H2_0
+	VZERO H0_1
+	VZERO H1_1
+	VZERO H2_1
+
+	VZERO M0
+	VZERO M1
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+
+	// H*[r**2, r]
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, H0_1, H1_1, T_10, M5)
+
+	SUB    $33, R3
+	VLM    (R2), M0, M1
+	VLL    R3, 32(R2), M2
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, M2
+
+	// H += m0
+	VZERO T_1
+	VZERO T_2
+	VZERO T_3
+	EXPACC2(M0, T_1, T_2, T_3, T_4, T_5, T_6)
+	VLEIB $10, $1, T_3
+	VAG   H0_0, T_1, H0_0
+	VAG   H1_0, T_2, H1_0
+	VAG   H2_0, T_3, H2_0
+
+	VZERO M0
+	VZERO M3
+	VZERO M4
+	VZERO M5
+	VZERO T_10
+
+	// (H+m0)*r
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M3, M4, M5, V0, T_10, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M3, M4, M5, T_10, H0_1, H1_1, H2_1, T_9)
+
+	// H += m1
+	VZERO V0
+	VZERO T_1
+	VZERO T_2
+	VZERO T_3
+	EXPACC2(M1, T_1, T_2, T_3, T_4, T_5, T_6)
+	VLEIB $10, $1, T_3
+	VAQ   H0_0, T_1, H0_0
+	VAQ   H1_0, T_2, H1_0
+	VAQ   H2_0, T_3, H2_0
+	REDUCE2(H0_0, H1_0, H2_0, M0, M3, M4, M5, T_9, H0_1, H1_1, H2_1, T_10)
+
+	// [H, m2] * [r**2, r]
+	EXPACC2(M2, H0_0, H1_0, H2_0, T_1, T_2, T_3)
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $10, $1, H2_0
+	VZERO  M0
+	VZERO  M1
+	VZERO  M2
+	VZERO  M3
+	VZERO  M4
+	VZERO  M5
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, H0_1, H1_1, M5, T_10)
+	SUB    $16, R3
+	CMPBLE R3, $0, next   // this condition must always hold true!
+
+b2:
+	CMPBLE R3, $16, b1
+
+	// 2 blocks remaining
+
+	// setup [r²,r]
+	VSLDB $8, R_0, R_0, R_0
+	VSLDB $8, R_1, R_1, R_1
+	VSLDB $8, R_2, R_2, R_2
+	VSLDB $8, R5_1, R5_1, R5_1
+	VSLDB $8, R5_2, R5_2, R5_2
+
+	VLVGG $1, RSAVE_0, R_0
+	VLVGG $1, RSAVE_1, R_1
+	VLVGG $1, RSAVE_2, R_2
+	VLVGG $1, R5SAVE_1, R5_1
+	VLVGG $1, R5SAVE_2, R5_2
+
+	// setup [h0, h1]
+	VSLDB $8, H0_0, H0_0, H0_0
+	VSLDB $8, H1_0, H1_0, H1_0
+	VSLDB $8, H2_0, H2_0, H2_0
+	VO    H0_1, H0_0, H0_0
+	VO    H1_1, H1_0, H1_0
+	VO    H2_1, H2_0, H2_0
+	VZERO H0_1
+	VZERO H1_1
+	VZERO H2_1
+
+	VZERO M0
+	VZERO M1
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+
+	// H*[r**2, r]
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, T_10, M0, M1, M2, M3, M4, T_4, T_5, T_2, T_7, T_8, T_9)
+	VMRHG V0, H0_1, H0_0
+	VMRHG V0, H1_1, H1_0
+	VMRHG V0, H2_1, H2_0
+	VMRLG V0, H0_1, H0_1
+	VMRLG V0, H1_1, H1_1
+	VMRLG V0, H2_1, H2_1
+
+	// move h to the left and 0s at the right
+	VSLDB $8, H0_0, H0_0, H0_0
+	VSLDB $8, H1_0, H1_0, H1_0
+	VSLDB $8, H2_0, H2_0, H2_0
+
+	// get message blocks and append 1 to start
+	SUB    $17, R3
+	VL     (R2), M0
+	VLL    R3, 16(R2), M1
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, M1
+	VZERO  T_6
+	VZERO  T_7
+	VZERO  T_8
+	EXPACC2(M0, T_6, T_7, T_8, T_1, T_2, T_3)
+	EXPACC2(M1, T_6, T_7, T_8, T_1, T_2, T_3)
+	VLEIB  $2, $1, T_8
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $10, $1, T_8
+
+	// add [m0, m1] to h
+	VAG H0_0, T_6, H0_0
+	VAG H1_0, T_7, H1_0
+	VAG H2_0, T_8, H2_0
+
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+	VZERO T_10
+	VZERO M0
+
+	// at this point R_0 .. R5_2 look like [r**2, r]
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M2, M3, M4, M5, T_10, M0, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M2, M3, M4, M5, T_9, H0_1, H1_1, H2_1, T_10)
+	SUB    $16, R3, R3
+	CMPBLE R3, $0, next
+
+b1:
+	CMPBLE R3, $0, next
+
+	// 1 block remaining
+
+	// setup [r²,r]
+	VSLDB $8, R_0, R_0, R_0
+	VSLDB $8, R_1, R_1, R_1
+	VSLDB $8, R_2, R_2, R_2
+	VSLDB $8, R5_1, R5_1, R5_1
+	VSLDB $8, R5_2, R5_2, R5_2
+
+	VLVGG $1, RSAVE_0, R_0
+	VLVGG $1, RSAVE_1, R_1
+	VLVGG $1, RSAVE_2, R_2
+	VLVGG $1, R5SAVE_1, R5_1
+	VLVGG $1, R5SAVE_2, R5_2
+
+	// setup [h0, h1]
+	VSLDB $8, H0_0, H0_0, H0_0
+	VSLDB $8, H1_0, H1_0, H1_0
+	VSLDB $8, H2_0, H2_0, H2_0
+	VO    H0_1, H0_0, H0_0
+	VO    H1_1, H1_0, H1_0
+	VO    H2_1, H2_0, H2_0
+	VZERO H0_1
+	VZERO H1_1
+	VZERO H2_1
+
+	VZERO M0
+	VZERO M1
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+
+	// H*[r**2, r]
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, T_9, T_10, H0_1, M5)
+
+	// set up [0, m0] limbs
+	SUB    $1, R3
+	VLL    R3, (R2), M0
+	ADD    $1, R3
+	MOVBZ  $1, R0
+	CMPBEQ R3, $16, 2(PC)
+	VLVGB  R3, R0, M0
+	VZERO  T_1
+	VZERO  T_2
+	VZERO  T_3
+	EXPACC2(M0, T_1, T_2, T_3, T_4, T_5, T_6)// limbs: [0, m]
+	CMPBNE R3, $16, 2(PC)
+	VLEIB  $10, $1, T_3
+
+	// h+m0
+	VAQ H0_0, T_1, H0_0
+	VAQ H1_0, T_2, H1_0
+	VAQ H2_0, T_3, H2_0
+
+	VZERO M0
+	VZERO M1
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, T_9, T_10, H0_1, M5)
+
+	BR next
+
+square:
+	// setup [r²,r]
+	VSLDB $8, R_0, R_0, R_0
+	VSLDB $8, R_1, R_1, R_1
+	VSLDB $8, R_2, R_2, R_2
+	VSLDB $8, R5_1, R5_1, R5_1
+	VSLDB $8, R5_2, R5_2, R5_2
+
+	VLVGG $1, RSAVE_0, R_0
+	VLVGG $1, RSAVE_1, R_1
+	VLVGG $1, RSAVE_2, R_2
+	VLVGG $1, R5SAVE_1, R5_1
+	VLVGG $1, R5SAVE_2, R5_2
+
+	// setup [h0, h1]
+	VSLDB $8, H0_0, H0_0, H0_0
+	VSLDB $8, H1_0, H1_0, H1_0
+	VSLDB $8, H2_0, H2_0, H2_0
+	VO    H0_1, H0_0, H0_0
+	VO    H1_1, H1_0, H1_0
+	VO    H2_1, H2_0, H2_0
+	VZERO H0_1
+	VZERO H1_1
+	VZERO H2_1
+
+	VZERO M0
+	VZERO M1
+	VZERO M2
+	VZERO M3
+	VZERO M4
+	VZERO M5
+
+	// (h0*r**2) + (h1*r)
+	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
+	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, T_9, T_10, H0_1, M5)
+	BR next
+
+TEXT ·hasVMSLFacility(SB), NOSPLIT, $24-1
+	MOVD  $x-24(SP), R1
+	XC    $24, 0(R1), 0(R1) // clear the storage
+	MOVD  $2, R0            // R0 is the number of double words stored -1
+	WORD  $0xB2B01000       // STFLE 0(R1)
+	XOR   R0, R0            // reset the value of R0
+	MOVBZ z-8(SP), R1
+	AND   $0x01, R1
+	BEQ   novmsl
+
+vectorinstalled:
+	// check if the vector instruction has been enabled
+	VLEIB  $0, $0xF, V16
+	VLGVB  $0, V16, R1
+	CMPBNE R1, $0xF, novmsl
+	MOVB   $1, ret+0(FP)    // have vx
+	RET
+
+novmsl:
+	MOVB $0, ret+0(FP) // no vx
+	RET
diff --git a/vendor/golang.org/x/crypto/ssh/agent/client.go b/vendor/golang.org/x/crypto/ssh/agent/client.go
index dce7682..b1808dd 100644
--- a/vendor/golang.org/x/crypto/ssh/agent/client.go
+++ b/vendor/golang.org/x/crypto/ssh/agent/client.go
@@ -8,7 +8,7 @@
 // ssh-agent process using the sample server.
 //
 // References:
-//  [PROTOCOL.agent]:    http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.agent?rev=HEAD
+//  [PROTOCOL.agent]: https://tools.ietf.org/html/draft-miller-ssh-agent-00
 package agent // import "golang.org/x/crypto/ssh/agent"
 
 import (
@@ -98,7 +98,7 @@ const (
 	agentAddIdentity         = 17
 	agentRemoveIdentity      = 18
 	agentRemoveAllIdentities = 19
-	agentAddIdConstrained    = 25
+	agentAddIDConstrained    = 25
 
 	// 3.3 Key-type independent requests from client to agent
 	agentAddSmartcardKey            = 20
@@ -515,7 +515,7 @@ func (c *client) insertKey(s interface{}, comment string, constraints []byte) er
 
 	// if constraints are present then the message type needs to be changed.
 	if len(constraints) != 0 {
-		req[0] = agentAddIdConstrained
+		req[0] = agentAddIDConstrained
 	}
 
 	resp, err := c.call(req)
@@ -577,11 +577,11 @@ func (c *client) Add(key AddedKey) error {
 		constraints = append(constraints, agentConstrainConfirm)
 	}
 
-	if cert := key.Certificate; cert == nil {
+	cert := key.Certificate
+	if cert == nil {
 		return c.insertKey(key.PrivateKey, key.Comment, constraints)
-	} else {
-		return c.insertCert(key.PrivateKey, cert, key.Comment, constraints)
 	}
+	return c.insertCert(key.PrivateKey, cert, key.Comment, constraints)
 }
 
 func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string, constraints []byte) error {
@@ -633,7 +633,7 @@ func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string
 
 	// if constraints are present then the message type needs to be changed.
 	if len(constraints) != 0 {
-		req[0] = agentAddIdConstrained
+		req[0] = agentAddIDConstrained
 	}
 
 	signer, err := ssh.NewSignerFromKey(s)
diff --git a/vendor/golang.org/x/crypto/ssh/agent/keyring.go b/vendor/golang.org/x/crypto/ssh/agent/keyring.go
index a6ba06a..1a51632 100644
--- a/vendor/golang.org/x/crypto/ssh/agent/keyring.go
+++ b/vendor/golang.org/x/crypto/ssh/agent/keyring.go
@@ -102,7 +102,7 @@ func (r *keyring) Unlock(passphrase []byte) error {
 	if !r.locked {
 		return errors.New("agent: not locked")
 	}
-	if len(passphrase) != len(r.passphrase) || 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
+	if 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
 		return fmt.Errorf("agent: incorrect passphrase")
 	}
 
diff --git a/vendor/golang.org/x/crypto/ssh/agent/server.go b/vendor/golang.org/x/crypto/ssh/agent/server.go
index 321e48a..2e4692c 100644
--- a/vendor/golang.org/x/crypto/ssh/agent/server.go
+++ b/vendor/golang.org/x/crypto/ssh/agent/server.go
@@ -148,7 +148,7 @@ func (s *server) processRequest(data []byte) (interface{}, error) {
 		}
 		return rep, nil
 
-	case agentAddIdConstrained, agentAddIdentity:
+	case agentAddIDConstrained, agentAddIdentity:
 		return nil, s.insertIdentity(data)
 	}
 
diff --git a/vendor/golang.org/x/crypto/ssh/certs.go b/vendor/golang.org/x/crypto/ssh/certs.go
index b1f0220..42106f3 100644
--- a/vendor/golang.org/x/crypto/ssh/certs.go
+++ b/vendor/golang.org/x/crypto/ssh/certs.go
@@ -44,7 +44,9 @@ type Signature struct {
 const CertTimeInfinity = 1<<64 - 1
 
 // An Certificate represents an OpenSSH certificate as defined in
-// [PROTOCOL.certkeys]?rev=1.8.
+// [PROTOCOL.certkeys]?rev=1.8. The Certificate type implements the
+// PublicKey interface, so it can be unmarshaled using
+// ParsePublicKey.
 type Certificate struct {
 	Nonce           []byte
 	Key             PublicKey
@@ -340,10 +342,10 @@ func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permis
 // the signature of the certificate.
 func (c *CertChecker) CheckCert(principal string, cert *Certificate) error {
 	if c.IsRevoked != nil && c.IsRevoked(cert) {
-		return fmt.Errorf("ssh: certicate serial %d revoked", cert.Serial)
+		return fmt.Errorf("ssh: certificate serial %d revoked", cert.Serial)
 	}
 
-	for opt, _ := range cert.CriticalOptions {
+	for opt := range cert.CriticalOptions {
 		// sourceAddressCriticalOption will be enforced by
 		// serverAuthenticate
 		if opt == sourceAddressCriticalOption {
diff --git a/vendor/golang.org/x/crypto/ssh/channel.go b/vendor/golang.org/x/crypto/ssh/channel.go
index 195530e..c0834c0 100644
--- a/vendor/golang.org/x/crypto/ssh/channel.go
+++ b/vendor/golang.org/x/crypto/ssh/channel.go
@@ -205,32 +205,32 @@ type channel struct {
 
 // writePacket sends a packet. If the packet is a channel close, it updates
 // sentClose. This method takes the lock c.writeMu.
-func (c *channel) writePacket(packet []byte) error {
-	c.writeMu.Lock()
-	if c.sentClose {
-		c.writeMu.Unlock()
+func (ch *channel) writePacket(packet []byte) error {
+	ch.writeMu.Lock()
+	if ch.sentClose {
+		ch.writeMu.Unlock()
 		return io.EOF
 	}
-	c.sentClose = (packet[0] == msgChannelClose)
-	err := c.mux.conn.writePacket(packet)
-	c.writeMu.Unlock()
+	ch.sentClose = (packet[0] == msgChannelClose)
+	err := ch.mux.conn.writePacket(packet)
+	ch.writeMu.Unlock()
 	return err
 }
 
-func (c *channel) sendMessage(msg interface{}) error {
+func (ch *channel) sendMessage(msg interface{}) error {
 	if debugMux {
-		log.Printf("send(%d): %#v", c.mux.chanList.offset, msg)
+		log.Printf("send(%d): %#v", ch.mux.chanList.offset, msg)
 	}
 
 	p := Marshal(msg)
-	binary.BigEndian.PutUint32(p[1:], c.remoteId)
-	return c.writePacket(p)
+	binary.BigEndian.PutUint32(p[1:], ch.remoteId)
+	return ch.writePacket(p)
 }
 
 // WriteExtended writes data to a specific extended stream. These streams are
 // used, for example, for stderr.
-func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err error) {
-	if c.sentEOF {
+func (ch *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err error) {
+	if ch.sentEOF {
 		return 0, io.EOF
 	}
 	// 1 byte message type, 4 bytes remoteId, 4 bytes data length
@@ -241,16 +241,16 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		opCode = msgChannelExtendedData
 	}
 
-	c.writeMu.Lock()
-	packet := c.packetPool[extendedCode]
+	ch.writeMu.Lock()
+	packet := ch.packetPool[extendedCode]
 	// We don't remove the buffer from packetPool, so
 	// WriteExtended calls from different goroutines will be
 	// flagged as errors by the race detector.
-	c.writeMu.Unlock()
+	ch.writeMu.Unlock()
 
 	for len(data) > 0 {
-		space := min(c.maxRemotePayload, len(data))
-		if space, err = c.remoteWin.reserve(space); err != nil {
+		space := min(ch.maxRemotePayload, len(data))
+		if space, err = ch.remoteWin.reserve(space); err != nil {
 			return n, err
 		}
 		if want := headerLength + space; uint32(cap(packet)) < want {
@@ -262,13 +262,13 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		todo := data[:space]
 
 		packet[0] = opCode
-		binary.BigEndian.PutUint32(packet[1:], c.remoteId)
+		binary.BigEndian.PutUint32(packet[1:], ch.remoteId)
 		if extendedCode > 0 {
 			binary.BigEndian.PutUint32(packet[5:], uint32(extendedCode))
 		}
 		binary.BigEndian.PutUint32(packet[headerLength-4:], uint32(len(todo)))
 		copy(packet[headerLength:], todo)
-		if err = c.writePacket(packet); err != nil {
+		if err = ch.writePacket(packet); err != nil {
 			return n, err
 		}
 
@@ -276,14 +276,14 @@ func (c *channel) WriteExtended(data []byte, extendedCode uint32) (n int, err er
 		data = data[len(todo):]
 	}
 
-	c.writeMu.Lock()
-	c.packetPool[extendedCode] = packet
-	c.writeMu.Unlock()
+	ch.writeMu.Lock()
+	ch.packetPool[extendedCode] = packet
+	ch.writeMu.Unlock()
 
 	return n, err
 }
 
-func (c *channel) handleData(packet []byte) error {
+func (ch *channel) handleData(packet []byte) error {
 	headerLen := 9
 	isExtendedData := packet[0] == msgChannelExtendedData
 	if isExtendedData {
@@ -303,7 +303,7 @@ func (c *channel) handleData(packet []byte) error {
 	if length == 0 {
 		return nil
 	}
-	if length > c.maxIncomingPayload {
+	if length > ch.maxIncomingPayload {
 		// TODO(hanwen): should send Disconnect?
 		return errors.New("ssh: incoming packet exceeds maximum payload size")
 	}
@@ -313,21 +313,21 @@ func (c *channel) handleData(packet []byte) error {
 		return errors.New("ssh: wrong packet length")
 	}
 
-	c.windowMu.Lock()
-	if c.myWindow < length {
-		c.windowMu.Unlock()
+	ch.windowMu.Lock()
+	if ch.myWindow < length {
+		ch.windowMu.Unlock()
 		// TODO(hanwen): should send Disconnect with reason?
 		return errors.New("ssh: remote side wrote too much")
 	}
-	c.myWindow -= length
-	c.windowMu.Unlock()
+	ch.myWindow -= length
+	ch.windowMu.Unlock()
 
 	if extended == 1 {
-		c.extPending.write(data)
+		ch.extPending.write(data)
 	} else if extended > 0 {
 		// discard other extended data.
 	} else {
-		c.pending.write(data)
+		ch.pending.write(data)
 	}
 	return nil
 }
@@ -384,31 +384,31 @@ func (c *channel) close() {
 // responseMessageReceived is called when a success or failure message is
 // received on a channel to check that such a message is reasonable for the
 // given channel.
-func (c *channel) responseMessageReceived() error {
-	if c.direction == channelInbound {
+func (ch *channel) responseMessageReceived() error {
+	if ch.direction == channelInbound {
 		return errors.New("ssh: channel response message received on inbound channel")
 	}
-	if c.decided {
+	if ch.decided {
 		return errors.New("ssh: duplicate response received for channel")
 	}
-	c.decided = true
+	ch.decided = true
 	return nil
 }
 
-func (c *channel) handlePacket(packet []byte) error {
+func (ch *channel) handlePacket(packet []byte) error {
 	switch packet[0] {
 	case msgChannelData, msgChannelExtendedData:
-		return c.handleData(packet)
+		return ch.handleData(packet)
 	case msgChannelClose:
-		c.sendMessage(channelCloseMsg{PeersId: c.remoteId})
-		c.mux.chanList.remove(c.localId)
-		c.close()
+		ch.sendMessage(channelCloseMsg{PeersID: ch.remoteId})
+		ch.mux.chanList.remove(ch.localId)
+		ch.close()
 		return nil
 	case msgChannelEOF:
 		// RFC 4254 is mute on how EOF affects dataExt messages but
 		// it is logical to signal EOF at the same time.
-		c.extPending.eof()
-		c.pending.eof()
+		ch.extPending.eof()
+		ch.pending.eof()
 		return nil
 	}
 
@@ -419,24 +419,24 @@ func (c *channel) handlePacket(packet []byte) error {
 
 	switch msg := decoded.(type) {
 	case *channelOpenFailureMsg:
-		if err := c.responseMessageReceived(); err != nil {
+		if err := ch.responseMessageReceived(); err != nil {
 			return err
 		}
-		c.mux.chanList.remove(msg.PeersId)
-		c.msg <- msg
+		ch.mux.chanList.remove(msg.PeersID)
+		ch.msg <- msg
 	case *channelOpenConfirmMsg:
-		if err := c.responseMessageReceived(); err != nil {
+		if err := ch.responseMessageReceived(); err != nil {
 			return err
 		}
 		if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
 			return fmt.Errorf("ssh: invalid MaxPacketSize %d from peer", msg.MaxPacketSize)
 		}
-		c.remoteId = msg.MyId
-		c.maxRemotePayload = msg.MaxPacketSize
-		c.remoteWin.add(msg.MyWindow)
-		c.msg <- msg
+		ch.remoteId = msg.MyID
+		ch.maxRemotePayload = msg.MaxPacketSize
+		ch.remoteWin.add(msg.MyWindow)
+		ch.msg <- msg
 	case *windowAdjustMsg:
-		if !c.remoteWin.add(msg.AdditionalBytes) {
+		if !ch.remoteWin.add(msg.AdditionalBytes) {
 			return fmt.Errorf("ssh: invalid window update for %d bytes", msg.AdditionalBytes)
 		}
 	case *channelRequestMsg:
@@ -444,12 +444,12 @@ func (c *channel) handlePacket(packet []byte) error {
 			Type:      msg.Request,
 			WantReply: msg.WantReply,
 			Payload:   msg.RequestSpecificData,
-			ch:        c,
+			ch:        ch,
 		}
 
-		c.incomingRequests <- &req
+		ch.incomingRequests <- &req
 	default:
-		c.msg <- msg
+		ch.msg <- msg
 	}
 	return nil
 }
@@ -488,23 +488,23 @@ func (e *extChannel) Read(data []byte) (n int, err error) {
 	return e.ch.ReadExtended(data, e.code)
 }
 
-func (c *channel) Accept() (Channel, <-chan *Request, error) {
-	if c.decided {
+func (ch *channel) Accept() (Channel, <-chan *Request, error) {
+	if ch.decided {
 		return nil, nil, errDecidedAlready
 	}
-	c.maxIncomingPayload = channelMaxPacket
+	ch.maxIncomingPayload = channelMaxPacket
 	confirm := channelOpenConfirmMsg{
-		PeersId:       c.remoteId,
-		MyId:          c.localId,
-		MyWindow:      c.myWindow,
-		MaxPacketSize: c.maxIncomingPayload,
+		PeersID:       ch.remoteId,
+		MyID:          ch.localId,
+		MyWindow:      ch.myWindow,
+		MaxPacketSize: ch.maxIncomingPayload,
 	}
-	c.decided = true
-	if err := c.sendMessage(confirm); err != nil {
+	ch.decided = true
+	if err := ch.sendMessage(confirm); err != nil {
 		return nil, nil, err
 	}
 
-	return c, c.incomingRequests, nil
+	return ch, ch.incomingRequests, nil
 }
 
 func (ch *channel) Reject(reason RejectionReason, message string) error {
@@ -512,7 +512,7 @@ func (ch *channel) Reject(reason RejectionReason, message string) error {
 		return errDecidedAlready
 	}
 	reject := channelOpenFailureMsg{
-		PeersId:  ch.remoteId,
+		PeersID:  ch.remoteId,
 		Reason:   reason,
 		Message:  message,
 		Language: "en",
@@ -541,7 +541,7 @@ func (ch *channel) CloseWrite() error {
 	}
 	ch.sentEOF = true
 	return ch.sendMessage(channelEOFMsg{
-		PeersId: ch.remoteId})
+		PeersID: ch.remoteId})
 }
 
 func (ch *channel) Close() error {
@@ -550,7 +550,7 @@ func (ch *channel) Close() error {
 	}
 
 	return ch.sendMessage(channelCloseMsg{
-		PeersId: ch.remoteId})
+		PeersID: ch.remoteId})
 }
 
 // Extended returns an io.ReadWriter that sends and receives data on the given,
@@ -577,7 +577,7 @@ func (ch *channel) SendRequest(name string, wantReply bool, payload []byte) (boo
 	}
 
 	msg := channelRequestMsg{
-		PeersId:             ch.remoteId,
+		PeersID:             ch.remoteId,
 		Request:             name,
 		WantReply:           wantReply,
 		RequestSpecificData: payload,
@@ -614,11 +614,11 @@ func (ch *channel) ackRequest(ok bool) error {
 	var msg interface{}
 	if !ok {
 		msg = channelRequestFailureMsg{
-			PeersId: ch.remoteId,
+			PeersID: ch.remoteId,
 		}
 	} else {
 		msg = channelRequestSuccessMsg{
-			PeersId: ch.remoteId,
+			PeersID: ch.remoteId,
 		}
 	}
 	return ch.sendMessage(msg)
diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go
index 22bb30c..67b0126 100644
--- a/vendor/golang.org/x/crypto/ssh/cipher.go
+++ b/vendor/golang.org/x/crypto/ssh/cipher.go
@@ -16,6 +16,10 @@ import (
 	"hash"
 	"io"
 	"io/ioutil"
+	"math/bits"
+
+	"golang.org/x/crypto/internal/chacha20"
+	"golang.org/x/crypto/poly1305"
 )
 
 const (
@@ -53,78 +57,78 @@ func newRC4(key, iv []byte) (cipher.Stream, error) {
 	return rc4.NewCipher(key)
 }
 
-type streamCipherMode struct {
-	keySize    int
-	ivSize     int
-	skip       int
-	createFunc func(key, iv []byte) (cipher.Stream, error)
+type cipherMode struct {
+	keySize int
+	ivSize  int
+	create  func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error)
 }
 
-func (c *streamCipherMode) createStream(key, iv []byte) (cipher.Stream, error) {
-	if len(key) < c.keySize {
-		panic("ssh: key length too small for cipher")
-	}
-	if len(iv) < c.ivSize {
-		panic("ssh: iv too small for cipher")
-	}
-
-	stream, err := c.createFunc(key[:c.keySize], iv[:c.ivSize])
-	if err != nil {
-		return nil, err
-	}
+func streamCipherMode(skip int, createFunc func(key, iv []byte) (cipher.Stream, error)) func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+	return func(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+		stream, err := createFunc(key, iv)
+		if err != nil {
+			return nil, err
+		}
 
-	var streamDump []byte
-	if c.skip > 0 {
-		streamDump = make([]byte, 512)
-	}
+		var streamDump []byte
+		if skip > 0 {
+			streamDump = make([]byte, 512)
+		}
 
-	for remainingToDump := c.skip; remainingToDump > 0; {
-		dumpThisTime := remainingToDump
-		if dumpThisTime > len(streamDump) {
-			dumpThisTime = len(streamDump)
+		for remainingToDump := skip; remainingToDump > 0; {
+			dumpThisTime := remainingToDump
+			if dumpThisTime > len(streamDump) {
+				dumpThisTime = len(streamDump)
+			}
+			stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime])
+			remainingToDump -= dumpThisTime
 		}
-		stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime])
-		remainingToDump -= dumpThisTime
-	}
 
-	return stream, nil
+		mac := macModes[algs.MAC].new(macKey)
+		return &streamPacketCipher{
+			mac:       mac,
+			etm:       macModes[algs.MAC].etm,
+			macResult: make([]byte, mac.Size()),
+			cipher:    stream,
+		}, nil
+	}
 }
 
 // cipherModes documents properties of supported ciphers. Ciphers not included
 // are not supported and will not be negotiated, even if explicitly requested in
 // ClientConfig.Crypto.Ciphers.
-var cipherModes = map[string]*streamCipherMode{
+var cipherModes = map[string]*cipherMode{
 	// Ciphers from RFC4344, which introduced many CTR-based ciphers. Algorithms
 	// are defined in the order specified in the RFC.
-	"aes128-ctr": {16, aes.BlockSize, 0, newAESCTR},
-	"aes192-ctr": {24, aes.BlockSize, 0, newAESCTR},
-	"aes256-ctr": {32, aes.BlockSize, 0, newAESCTR},
+	"aes128-ctr": {16, aes.BlockSize, streamCipherMode(0, newAESCTR)},
+	"aes192-ctr": {24, aes.BlockSize, streamCipherMode(0, newAESCTR)},
+	"aes256-ctr": {32, aes.BlockSize, streamCipherMode(0, newAESCTR)},
 
 	// Ciphers from RFC4345, which introduces security-improved arcfour ciphers.
 	// They are defined in the order specified in the RFC.
-	"arcfour128": {16, 0, 1536, newRC4},
-	"arcfour256": {32, 0, 1536, newRC4},
+	"arcfour128": {16, 0, streamCipherMode(1536, newRC4)},
+	"arcfour256": {32, 0, streamCipherMode(1536, newRC4)},
 
 	// Cipher defined in RFC 4253, which describes SSH Transport Layer Protocol.
 	// Note that this cipher is not safe, as stated in RFC 4253: "Arcfour (and
 	// RC4) has problems with weak keys, and should be used with caution."
 	// RFC4345 introduces improved versions of Arcfour.
-	"arcfour": {16, 0, 0, newRC4},
+	"arcfour": {16, 0, streamCipherMode(0, newRC4)},
 
-	// AES-GCM is not a stream cipher, so it is constructed with a
-	// special case. If we add any more non-stream ciphers, we
-	// should invest a cleaner way to do this.
-	gcmCipherID: {16, 12, 0, nil},
+	// AEAD ciphers
+	gcmCipherID:        {16, 12, newGCMCipher},
+	chacha20Poly1305ID: {64, 0, newChaCha20Cipher},
 
 	// CBC mode is insecure and so is not included in the default config.
 	// (See http://www.isg.rhul.ac.uk/~kp/SandPfinal.pdf). If absolutely
 	// needed, it's possible to specify a custom Config to enable it.
 	// You should expect that an active attacker can recover plaintext if
 	// you do.
-	aes128cbcID: {16, aes.BlockSize, 0, nil},
+	aes128cbcID: {16, aes.BlockSize, newAESCBCCipher},
 
-	// 3des-cbc is insecure and is disabled by default.
-	tripledescbcID: {24, des.BlockSize, 0, nil},
+	// 3des-cbc is insecure and is not included in the default
+	// config.
+	tripledescbcID: {24, des.BlockSize, newTripleDESCBCCipher},
 }
 
 // prefixLen is the length of the packet prefix that contains the packet length
@@ -304,7 +308,7 @@ type gcmCipher struct {
 	buf    []byte
 }
 
-func newGCMCipher(iv, key, macKey []byte) (packetCipher, error) {
+func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) {
 	c, err := aes.NewCipher(key)
 	if err != nil {
 		return nil, err
@@ -372,7 +376,7 @@ func (c *gcmCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	}
 	length := binary.BigEndian.Uint32(c.prefix[:])
 	if length > maxPacket {
-		return nil, errors.New("ssh: max packet length exceeded.")
+		return nil, errors.New("ssh: max packet length exceeded")
 	}
 
 	if cap(c.buf) < int(length+gcmTagSize) {
@@ -422,7 +426,7 @@ type cbcCipher struct {
 	oracleCamouflage uint32
 }
 
-func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newCBCCipher(c cipher.Block, key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	cbc := &cbcCipher{
 		mac:        macModes[algs.MAC].new(macKey),
 		decrypter:  cipher.NewCBCDecrypter(c, iv),
@@ -436,13 +440,13 @@ func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorith
 	return cbc, nil
 }
 
-func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newAESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	c, err := aes.NewCipher(key)
 	if err != nil {
 		return nil, err
 	}
 
-	cbc, err := newCBCCipher(c, iv, key, macKey, algs)
+	cbc, err := newCBCCipher(c, key, iv, macKey, algs)
 	if err != nil {
 		return nil, err
 	}
@@ -450,13 +454,13 @@ func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCi
 	return cbc, nil
 }
 
-func newTripleDESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
+func newTripleDESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) {
 	c, err := des.NewTripleDESCipher(key)
 	if err != nil {
 		return nil, err
 	}
 
-	cbc, err := newCBCCipher(c, iv, key, macKey, algs)
+	cbc, err := newCBCCipher(c, key, iv, macKey, algs)
 	if err != nil {
 		return nil, err
 	}
@@ -548,11 +552,11 @@ func (c *cbcCipher) readPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error)
 		c.packetData = c.packetData[:entirePacketSize]
 	}
 
-	if n, err := io.ReadFull(r, c.packetData[firstBlockLength:]); err != nil {
+	n, err := io.ReadFull(r, c.packetData[firstBlockLength:])
+	if err != nil {
 		return nil, err
-	} else {
-		c.oracleCamouflage -= uint32(n)
 	}
+	c.oracleCamouflage -= uint32(n)
 
 	remainingCrypted := c.packetData[firstBlockLength:macStart]
 	c.decrypter.CryptBlocks(remainingCrypted, remainingCrypted)
@@ -627,3 +631,140 @@ func (c *cbcCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, pack
 
 	return nil
 }
+
+const chacha20Poly1305ID = "chacha20-poly1305@openssh.com"
+
+// chacha20Poly1305Cipher implements the chacha20-poly1305@openssh.com
+// AEAD, which is described here:
+//
+//   https://tools.ietf.org/html/draft-josefsson-ssh-chacha20-poly1305-openssh-00
+//
+// the methods here also implement padding, which RFC4253 Section 6
+// also requires of stream ciphers.
+type chacha20Poly1305Cipher struct {
+	lengthKey  [8]uint32
+	contentKey [8]uint32
+	buf        []byte
+}
+
+func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) {
+	if len(key) != 64 {
+		panic(len(key))
+	}
+
+	c := &chacha20Poly1305Cipher{
+		buf: make([]byte, 256),
+	}
+
+	for i := range c.contentKey {
+		c.contentKey[i] = binary.LittleEndian.Uint32(key[i*4 : (i+1)*4])
+	}
+	for i := range c.lengthKey {
+		c.lengthKey[i] = binary.LittleEndian.Uint32(key[(i+8)*4 : (i+9)*4])
+	}
+	return c, nil
+}
+
+func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+	nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)}
+	s := chacha20.New(c.contentKey, nonce)
+	var polyKey [32]byte
+	s.XORKeyStream(polyKey[:], polyKey[:])
+	s.Advance() // skip next 32 bytes
+
+	encryptedLength := c.buf[:4]
+	if _, err := io.ReadFull(r, encryptedLength); err != nil {
+		return nil, err
+	}
+
+	var lenBytes [4]byte
+	chacha20.New(c.lengthKey, nonce).XORKeyStream(lenBytes[:], encryptedLength)
+
+	length := binary.BigEndian.Uint32(lenBytes[:])
+	if length > maxPacket {
+		return nil, errors.New("ssh: invalid packet length, packet too large")
+	}
+
+	contentEnd := 4 + length
+	packetEnd := contentEnd + poly1305.TagSize
+	if uint32(cap(c.buf)) < packetEnd {
+		c.buf = make([]byte, packetEnd)
+		copy(c.buf[:], encryptedLength)
+	} else {
+		c.buf = c.buf[:packetEnd]
+	}
+
+	if _, err := io.ReadFull(r, c.buf[4:packetEnd]); err != nil {
+		return nil, err
+	}
+
+	var mac [poly1305.TagSize]byte
+	copy(mac[:], c.buf[contentEnd:packetEnd])
+	if !poly1305.Verify(&mac, c.buf[:contentEnd], &polyKey) {
+		return nil, errors.New("ssh: MAC failure")
+	}
+
+	plain := c.buf[4:contentEnd]
+	s.XORKeyStream(plain, plain)
+
+	padding := plain[0]
+	if padding < 4 {
+		// padding is a byte, so it automatically satisfies
+		// the maximum size, which is 255.
+		return nil, fmt.Errorf("ssh: illegal padding %d", padding)
+	}
+
+	if int(padding)+1 >= len(plain) {
+		return nil, fmt.Errorf("ssh: padding %d too large", padding)
+	}
+
+	plain = plain[1 : len(plain)-int(padding)]
+
+	return plain, nil
+}
+
+func (c *chacha20Poly1305Cipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error {
+	nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)}
+	s := chacha20.New(c.contentKey, nonce)
+	var polyKey [32]byte
+	s.XORKeyStream(polyKey[:], polyKey[:])
+	s.Advance() // skip next 32 bytes
+
+	// There is no blocksize, so fall back to multiple of 8 byte
+	// padding, as described in RFC 4253, Sec 6.
+	const packetSizeMultiple = 8
+
+	padding := packetSizeMultiple - (1+len(payload))%packetSizeMultiple
+	if padding < 4 {
+		padding += packetSizeMultiple
+	}
+
+	// size (4 bytes), padding (1), payload, padding, tag.
+	totalLength := 4 + 1 + len(payload) + padding + poly1305.TagSize
+	if cap(c.buf) < totalLength {
+		c.buf = make([]byte, totalLength)
+	} else {
+		c.buf = c.buf[:totalLength]
+	}
+
+	binary.BigEndian.PutUint32(c.buf, uint32(1+len(payload)+padding))
+	chacha20.New(c.lengthKey, nonce).XORKeyStream(c.buf, c.buf[:4])
+	c.buf[4] = byte(padding)
+	copy(c.buf[5:], payload)
+	packetEnd := 5 + len(payload) + padding
+	if _, err := io.ReadFull(rand, c.buf[5+len(payload):packetEnd]); err != nil {
+		return err
+	}
+
+	s.XORKeyStream(c.buf[4:], c.buf[4:packetEnd])
+
+	var mac [poly1305.TagSize]byte
+	poly1305.Sum(&mac, c.buf[:packetEnd], &polyKey)
+
+	copy(c.buf[packetEnd:], mac[:])
+
+	if _, err := w.Write(c.buf); err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/vendor/golang.org/x/crypto/ssh/client.go b/vendor/golang.org/x/crypto/ssh/client.go
index a7e3263..ae6ca77 100644
--- a/vendor/golang.org/x/crypto/ssh/client.go
+++ b/vendor/golang.org/x/crypto/ssh/client.go
@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"os"
 	"sync"
 	"time"
 )
@@ -18,6 +19,8 @@ import (
 type Client struct {
 	Conn
 
+	handleForwardsOnce sync.Once // guards calling (*Client).handleForwards
+
 	forwards        forwardList // forwarded tcpip connections from the remote side
 	mu              sync.Mutex
 	channelHandlers map[string]chan NewChannel
@@ -59,8 +62,6 @@ func NewClient(c Conn, chans <-chan NewChannel, reqs <-chan *Request) *Client {
 		conn.Wait()
 		conn.forwards.closeAll()
 	}()
-	go conn.forwards.handleChannels(conn.HandleChannelOpen("forwarded-tcpip"))
-	go conn.forwards.handleChannels(conn.HandleChannelOpen("forwarded-streamlocal@openssh.com"))
 	return conn
 }
 
@@ -187,6 +188,10 @@ func Dial(network, addr string, config *ClientConfig) (*Client, error) {
 // net.Conn underlying the the SSH connection.
 type HostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error
 
+// BannerCallback is the function type used for treat the banner sent by
+// the server. A BannerCallback receives the message sent by the remote server.
+type BannerCallback func(message string) error
+
 // A ClientConfig structure is used to configure a Client. It must not be
 // modified after having been passed to an SSH function.
 type ClientConfig struct {
@@ -209,6 +214,12 @@ type ClientConfig struct {
 	// FixedHostKey can be used for simplistic host key checks.
 	HostKeyCallback HostKeyCallback
 
+	// BannerCallback is called during the SSH dance to display a custom
+	// server's message. The client configuration can supply this callback to
+	// handle it as wished. The function BannerDisplayStderr can be used for
+	// simplistic display on Stderr.
+	BannerCallback BannerCallback
+
 	// ClientVersion contains the version identification string that will
 	// be used for the connection. If empty, a reasonable default is used.
 	ClientVersion string
@@ -255,3 +266,13 @@ func FixedHostKey(key PublicKey) HostKeyCallback {
 	hk := &fixedHostKey{key}
 	return hk.check
 }
+
+// BannerDisplayStderr returns a function that can be used for
+// ClientConfig.BannerCallback to display banners on os.Stderr.
+func BannerDisplayStderr() BannerCallback {
+	return func(banner string) error {
+		_, err := os.Stderr.WriteString(banner)
+
+		return err
+	}
+}
diff --git a/vendor/golang.org/x/crypto/ssh/client_auth.go b/vendor/golang.org/x/crypto/ssh/client_auth.go
index 3acd8d4..5f44b77 100644
--- a/vendor/golang.org/x/crypto/ssh/client_auth.go
+++ b/vendor/golang.org/x/crypto/ssh/client_auth.go
@@ -11,6 +11,14 @@ import (
 	"io"
 )
 
+type authResult int
+
+const (
+	authFailure authResult = iota
+	authPartialSuccess
+	authSuccess
+)
+
 // clientAuthenticate authenticates with the remote server. See RFC 4252.
 func (c *connection) clientAuthenticate(config *ClientConfig) error {
 	// initiate user auth session
@@ -37,11 +45,12 @@ func (c *connection) clientAuthenticate(config *ClientConfig) error {
 		if err != nil {
 			return err
 		}
-		if ok {
+		if ok == authSuccess {
 			// success
 			return nil
+		} else if ok == authFailure {
+			tried[auth.method()] = true
 		}
-		tried[auth.method()] = true
 		if methods == nil {
 			methods = lastMethods
 		}
@@ -82,7 +91,7 @@ type AuthMethod interface {
 	// If authentication is not successful, a []string of alternative
 	// method names is returned. If the slice is nil, it will be ignored
 	// and the previous set of possible methods will be reused.
-	auth(session []byte, user string, p packetConn, rand io.Reader) (bool, []string, error)
+	auth(session []byte, user string, p packetConn, rand io.Reader) (authResult, []string, error)
 
 	// method returns the RFC 4252 method name.
 	method() string
@@ -91,13 +100,13 @@ type AuthMethod interface {
 // "none" authentication, RFC 4252 section 5.2.
 type noneAuth int
 
-func (n *noneAuth) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (n *noneAuth) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	if err := c.writePacket(Marshal(&userAuthRequestMsg{
 		User:    user,
 		Service: serviceSSH,
 		Method:  "none",
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	return handleAuthResponse(c)
@@ -111,7 +120,7 @@ func (n *noneAuth) method() string {
 // a function call, e.g. by prompting the user.
 type passwordCallback func() (password string, err error)
 
-func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	type passwordAuthMsg struct {
 		User     string `sshtype:"50"`
 		Service  string
@@ -125,7 +134,7 @@ func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand
 	// The program may only find out that the user doesn't have a password
 	// when prompting.
 	if err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	if err := c.writePacket(Marshal(&passwordAuthMsg{
@@ -135,7 +144,7 @@ func (cb passwordCallback) auth(session []byte, user string, c packetConn, rand
 		Reply:    false,
 		Password: pw,
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	return handleAuthResponse(c)
@@ -178,7 +187,7 @@ func (cb publicKeyCallback) method() string {
 	return "publickey"
 }
 
-func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	// Authentication is performed by sending an enquiry to test if a key is
 	// acceptable to the remote. If the key is acceptable, the client will
 	// attempt to authenticate with the valid key.  If not the client will repeat
@@ -186,13 +195,13 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 
 	signers, err := cb()
 	if err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 	var methods []string
 	for _, signer := range signers {
 		ok, err := validateKey(signer.PublicKey(), user, c)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 		if !ok {
 			continue
@@ -206,7 +215,7 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 			Method:  cb.method(),
 		}, []byte(pub.Type()), pubKey))
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// manually wrap the serialized signature in a string
@@ -224,24 +233,24 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 		}
 		p := Marshal(&msg)
 		if err := c.writePacket(p); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
-		var success bool
+		var success authResult
 		success, methods, err = handleAuthResponse(c)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// If authentication succeeds or the list of available methods does not
 		// contain the "publickey" method, do not attempt to authenticate with any
 		// other keys.  According to RFC 4252 Section 7, the latter can occur when
 		// additional authentication methods are required.
-		if success || !containsMethod(methods, cb.method()) {
+		if success == authSuccess || !containsMethod(methods, cb.method()) {
 			return success, methods, err
 		}
 	}
 
-	return false, methods, nil
+	return authFailure, methods, nil
 }
 
 func containsMethod(methods []string, method string) bool {
@@ -283,7 +292,9 @@ func confirmKeyAck(key PublicKey, c packetConn) (bool, error) {
 		}
 		switch packet[0] {
 		case msgUserAuthBanner:
-			// TODO(gpaul): add callback to present the banner to the user
+			if err := handleBannerResponse(c, packet); err != nil {
+				return false, err
+			}
 		case msgUserAuthPubKeyOk:
 			var msg userAuthPubKeyOkMsg
 			if err := Unmarshal(packet, &msg); err != nil {
@@ -316,30 +327,53 @@ func PublicKeysCallback(getSigners func() (signers []Signer, err error)) AuthMet
 // handleAuthResponse returns whether the preceding authentication request succeeded
 // along with a list of remaining authentication methods to try next and
 // an error if an unexpected response was received.
-func handleAuthResponse(c packetConn) (bool, []string, error) {
+func handleAuthResponse(c packetConn) (authResult, []string, error) {
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		switch packet[0] {
 		case msgUserAuthBanner:
-			// TODO: add callback to present the banner to the user
+			if err := handleBannerResponse(c, packet); err != nil {
+				return authFailure, nil, err
+			}
 		case msgUserAuthFailure:
 			var msg userAuthFailureMsg
 			if err := Unmarshal(packet, &msg); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
+			}
+			if msg.PartialSuccess {
+				return authPartialSuccess, msg.Methods, nil
 			}
-			return false, msg.Methods, nil
+			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
-			return true, nil, nil
+			return authSuccess, nil, nil
 		default:
-			return false, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0])
+			return authFailure, nil, unexpectedMessageError(msgUserAuthSuccess, packet[0])
 		}
 	}
 }
 
+func handleBannerResponse(c packetConn, packet []byte) error {
+	var msg userAuthBannerMsg
+	if err := Unmarshal(packet, &msg); err != nil {
+		return err
+	}
+
+	transport, ok := c.(*handshakeTransport)
+	if !ok {
+		return nil
+	}
+
+	if transport.bannerCallback != nil {
+		return transport.bannerCallback(msg.Message)
+	}
+
+	return nil
+}
+
 // KeyboardInteractiveChallenge should print questions, optionally
 // disabling echoing (e.g. for passwords), and return all the answers.
 // Challenge may be called multiple times in a single session. After
@@ -359,7 +393,7 @@ func (cb KeyboardInteractiveChallenge) method() string {
 	return "keyboard-interactive"
 }
 
-func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader) (bool, []string, error) {
+func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader) (authResult, []string, error) {
 	type initiateMsg struct {
 		User       string `sshtype:"50"`
 		Service    string
@@ -373,37 +407,42 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		Service: serviceSSH,
 		Method:  "keyboard-interactive",
 	})); err != nil {
-		return false, nil, err
+		return authFailure, nil, err
 	}
 
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// like handleAuthResponse, but with less options.
 		switch packet[0] {
 		case msgUserAuthBanner:
-			// TODO: Print banners during userauth.
+			if err := handleBannerResponse(c, packet); err != nil {
+				return authFailure, nil, err
+			}
 			continue
 		case msgUserAuthInfoRequest:
 			// OK
 		case msgUserAuthFailure:
 			var msg userAuthFailureMsg
 			if err := Unmarshal(packet, &msg); err != nil {
-				return false, nil, err
+				return authFailure, nil, err
+			}
+			if msg.PartialSuccess {
+				return authPartialSuccess, msg.Methods, nil
 			}
-			return false, msg.Methods, nil
+			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
-			return true, nil, nil
+			return authSuccess, nil, nil
 		default:
-			return false, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
+			return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
 		}
 
 		var msg userAuthInfoRequestMsg
 		if err := Unmarshal(packet, &msg); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		// Manually unpack the prompt/echo pairs.
@@ -413,7 +452,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		for i := 0; i < int(msg.NumPrompts); i++ {
 			prompt, r, ok := parseString(rest)
 			if !ok || len(r) == 0 {
-				return false, nil, errors.New("ssh: prompt format error")
+				return authFailure, nil, errors.New("ssh: prompt format error")
 			}
 			prompts = append(prompts, string(prompt))
 			echos = append(echos, r[0] != 0)
@@ -421,16 +460,16 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		}
 
 		if len(rest) != 0 {
-			return false, nil, errors.New("ssh: extra data following keyboard-interactive pairs")
+			return authFailure, nil, errors.New("ssh: extra data following keyboard-interactive pairs")
 		}
 
 		answers, err := cb(msg.User, msg.Instruction, prompts, echos)
 		if err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 
 		if len(answers) != len(prompts) {
-			return false, nil, errors.New("ssh: not enough answers from keyboard-interactive callback")
+			return authFailure, nil, errors.New("ssh: not enough answers from keyboard-interactive callback")
 		}
 		responseLength := 1 + 4
 		for _, a := range answers {
@@ -446,7 +485,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		}
 
 		if err := c.writePacket(serialized); err != nil {
-			return false, nil, err
+			return authFailure, nil, err
 		}
 	}
 }
@@ -456,10 +495,10 @@ type retryableAuthMethod struct {
 	maxTries   int
 }
 
-func (r *retryableAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader) (ok bool, methods []string, err error) {
+func (r *retryableAuthMethod) auth(session []byte, user string, c packetConn, rand io.Reader) (ok authResult, methods []string, err error) {
 	for i := 0; r.maxTries <= 0 || i < r.maxTries; i++ {
 		ok, methods, err = r.authMethod.auth(session, user, c, rand)
-		if ok || err != nil { // either success or error terminate
+		if ok != authFailure || err != nil { // either success, partial success or error terminate
 			return ok, methods, err
 		}
 	}
diff --git a/vendor/golang.org/x/crypto/ssh/common.go b/vendor/golang.org/x/crypto/ssh/common.go
index dc39e4d..04f3620 100644
--- a/vendor/golang.org/x/crypto/ssh/common.go
+++ b/vendor/golang.org/x/crypto/ssh/common.go
@@ -24,11 +24,21 @@ const (
 	serviceSSH      = "ssh-connection"
 )
 
-// supportedCiphers specifies the supported ciphers in preference order.
+// supportedCiphers lists ciphers we support but might not recommend.
 var supportedCiphers = []string{
 	"aes128-ctr", "aes192-ctr", "aes256-ctr",
 	"aes128-gcm@openssh.com",
-	"arcfour256", "arcfour128",
+	chacha20Poly1305ID,
+	"arcfour256", "arcfour128", "arcfour",
+	aes128cbcID,
+	tripledescbcID,
+}
+
+// preferredCiphers specifies the default preference for ciphers.
+var preferredCiphers = []string{
+	"aes128-gcm@openssh.com",
+	chacha20Poly1305ID,
+	"aes128-ctr", "aes192-ctr", "aes256-ctr",
 }
 
 // supportedKexAlgos specifies the supported key-exchange algorithms in
@@ -211,7 +221,7 @@ func (c *Config) SetDefaults() {
 		c.Rand = rand.Reader
 	}
 	if c.Ciphers == nil {
-		c.Ciphers = supportedCiphers
+		c.Ciphers = preferredCiphers
 	}
 	var ciphers []string
 	for _, c := range c.Ciphers {
@@ -242,7 +252,7 @@ func (c *Config) SetDefaults() {
 
 // buildDataSignedForAuth returns the data that is signed in order to prove
 // possession of a private key. See RFC 4252, section 7.
-func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
+func buildDataSignedForAuth(sessionID []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
 	data := struct {
 		Session []byte
 		Type    byte
@@ -253,7 +263,7 @@ func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubK
 		Algo    []byte
 		PubKey  []byte
 	}{
-		sessionId,
+		sessionID,
 		msgUserAuthRequest,
 		req.User,
 		req.Service,
diff --git a/vendor/golang.org/x/crypto/ssh/handshake.go b/vendor/golang.org/x/crypto/ssh/handshake.go
index 932ce83..4f7912e 100644
--- a/vendor/golang.org/x/crypto/ssh/handshake.go
+++ b/vendor/golang.org/x/crypto/ssh/handshake.go
@@ -78,6 +78,11 @@ type handshakeTransport struct {
 	dialAddress     string
 	remoteAddr      net.Addr
 
+	// bannerCallback is non-empty if we are the client and it has been set in
+	// ClientConfig. In that case it is called during the user authentication
+	// dance to handle a custom server's message.
+	bannerCallback BannerCallback
+
 	// Algorithms agreed in the last key exchange.
 	algorithms *algorithms
 
@@ -120,6 +125,7 @@ func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byt
 	t.dialAddress = dialAddr
 	t.remoteAddr = addr
 	t.hostKeyCallback = config.HostKeyCallback
+	t.bannerCallback = config.BannerCallback
 	if config.HostKeyAlgorithms != nil {
 		t.hostKeyAlgorithms = config.HostKeyAlgorithms
 	} else {
diff --git a/vendor/golang.org/x/crypto/ssh/kex.go b/vendor/golang.org/x/crypto/ssh/kex.go
index f91c277..f34bcc0 100644
--- a/vendor/golang.org/x/crypto/ssh/kex.go
+++ b/vendor/golang.org/x/crypto/ssh/kex.go
@@ -119,7 +119,7 @@ func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handsha
 		return nil, err
 	}
 
-	kInt, err := group.diffieHellman(kexDHReply.Y, x)
+	ki, err := group.diffieHellman(kexDHReply.Y, x)
 	if err != nil {
 		return nil, err
 	}
@@ -129,8 +129,8 @@ func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handsha
 	writeString(h, kexDHReply.HostKey)
 	writeInt(h, X)
 	writeInt(h, kexDHReply.Y)
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	return &kexResult{
@@ -164,7 +164,7 @@ func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handsha
 	}
 
 	Y := new(big.Int).Exp(group.g, y, group.p)
-	kInt, err := group.diffieHellman(kexDHInit.X, y)
+	ki, err := group.diffieHellman(kexDHInit.X, y)
 	if err != nil {
 		return nil, err
 	}
@@ -177,8 +177,8 @@ func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handsha
 	writeInt(h, kexDHInit.X)
 	writeInt(h, Y)
 
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	H := h.Sum(nil)
@@ -462,9 +462,9 @@ func (kex *curve25519sha256) Client(c packetConn, rand io.Reader, magics *handsh
 	writeString(h, kp.pub[:])
 	writeString(h, reply.EphemeralPubKey)
 
-	kInt := new(big.Int).SetBytes(secret[:])
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	ki := new(big.Int).SetBytes(secret[:])
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	return &kexResult{
@@ -510,9 +510,9 @@ func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handsh
 	writeString(h, kexInit.ClientPubKey)
 	writeString(h, kp.pub[:])
 
-	kInt := new(big.Int).SetBytes(secret[:])
-	K := make([]byte, intLength(kInt))
-	marshalInt(K, kInt)
+	ki := new(big.Int).SetBytes(secret[:])
+	K := make([]byte, intLength(ki))
+	marshalInt(K, ki)
 	h.Write(K)
 
 	H := h.Sum(nil)
diff --git a/vendor/golang.org/x/crypto/ssh/keys.go b/vendor/golang.org/x/crypto/ssh/keys.go
index b682c17..73697de 100644
--- a/vendor/golang.org/x/crypto/ssh/keys.go
+++ b/vendor/golang.org/x/crypto/ssh/keys.go
@@ -276,7 +276,8 @@ type PublicKey interface {
 	Type() string
 
 	// Marshal returns the serialized key data in SSH wire format,
-	// with the name prefix.
+	// with the name prefix. To unmarshal the returned data, use
+	// the ParsePublicKey function.
 	Marshal() []byte
 
 	// Verify that sig is a signature on the given data using this
@@ -363,7 +364,7 @@ func (r *rsaPublicKey) CryptoPublicKey() crypto.PublicKey {
 
 type dsaPublicKey dsa.PublicKey
 
-func (r *dsaPublicKey) Type() string {
+func (k *dsaPublicKey) Type() string {
 	return "ssh-dss"
 }
 
@@ -481,12 +482,12 @@ func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
 
 type ecdsaPublicKey ecdsa.PublicKey
 
-func (key *ecdsaPublicKey) Type() string {
-	return "ecdsa-sha2-" + key.nistID()
+func (k *ecdsaPublicKey) Type() string {
+	return "ecdsa-sha2-" + k.nistID()
 }
 
-func (key *ecdsaPublicKey) nistID() string {
-	switch key.Params().BitSize {
+func (k *ecdsaPublicKey) nistID() string {
+	switch k.Params().BitSize {
 	case 256:
 		return "nistp256"
 	case 384:
@@ -499,7 +500,7 @@ func (key *ecdsaPublicKey) nistID() string {
 
 type ed25519PublicKey ed25519.PublicKey
 
-func (key ed25519PublicKey) Type() string {
+func (k ed25519PublicKey) Type() string {
 	return KeyAlgoED25519
 }
 
@@ -518,23 +519,23 @@ func parseED25519(in []byte) (out PublicKey, rest []byte, err error) {
 	return (ed25519PublicKey)(key), w.Rest, nil
 }
 
-func (key ed25519PublicKey) Marshal() []byte {
+func (k ed25519PublicKey) Marshal() []byte {
 	w := struct {
 		Name     string
 		KeyBytes []byte
 	}{
 		KeyAlgoED25519,
-		[]byte(key),
+		[]byte(k),
 	}
 	return Marshal(&w)
 }
 
-func (key ed25519PublicKey) Verify(b []byte, sig *Signature) error {
-	if sig.Format != key.Type() {
-		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, key.Type())
+func (k ed25519PublicKey) Verify(b []byte, sig *Signature) error {
+	if sig.Format != k.Type() {
+		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
 
-	edKey := (ed25519.PublicKey)(key)
+	edKey := (ed25519.PublicKey)(k)
 	if ok := ed25519.Verify(edKey, b, sig.Blob); !ok {
 		return errors.New("ssh: signature did not verify")
 	}
@@ -595,9 +596,9 @@ func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
 	return (*ecdsaPublicKey)(key), w.Rest, nil
 }
 
-func (key *ecdsaPublicKey) Marshal() []byte {
+func (k *ecdsaPublicKey) Marshal() []byte {
 	// See RFC 5656, section 3.1.
-	keyBytes := elliptic.Marshal(key.Curve, key.X, key.Y)
+	keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y)
 	// ECDSA publickey struct layout should match the struct used by
 	// parseECDSACert in the x/crypto/ssh/agent package.
 	w := struct {
@@ -605,20 +606,20 @@ func (key *ecdsaPublicKey) Marshal() []byte {
 		ID   string
 		Key  []byte
 	}{
-		key.Type(),
-		key.nistID(),
+		k.Type(),
+		k.nistID(),
 		keyBytes,
 	}
 
 	return Marshal(&w)
 }
 
-func (key *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
-	if sig.Format != key.Type() {
-		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, key.Type())
+func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
+	if sig.Format != k.Type() {
+		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
 
-	h := ecHash(key.Curve).New()
+	h := ecHash(k.Curve).New()
 	h.Write(data)
 	digest := h.Sum(nil)
 
@@ -635,7 +636,7 @@ func (key *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
 		return err
 	}
 
-	if ecdsa.Verify((*ecdsa.PublicKey)(key), digest, ecSig.R, ecSig.S) {
+	if ecdsa.Verify((*ecdsa.PublicKey)(k), digest, ecSig.R, ecSig.S) {
 		return nil
 	}
 	return errors.New("ssh: signature did not verify")
@@ -758,7 +759,7 @@ func NewPublicKey(key interface{}) (PublicKey, error) {
 		return (*rsaPublicKey)(key), nil
 	case *ecdsa.PublicKey:
 		if !supportedEllipticCurve(key.Curve) {
-			return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported.")
+			return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported")
 		}
 		return (*ecdsaPublicKey)(key), nil
 	case *dsa.PublicKey:
diff --git a/vendor/golang.org/x/crypto/ssh/messages.go b/vendor/golang.org/x/crypto/ssh/messages.go
index e6ecd3a..08d2811 100644
--- a/vendor/golang.org/x/crypto/ssh/messages.go
+++ b/vendor/golang.org/x/crypto/ssh/messages.go
@@ -23,10 +23,6 @@ const (
 	msgUnimplemented = 3
 	msgDebug         = 4
 	msgNewKeys       = 21
-
-	// Standard authentication messages
-	msgUserAuthSuccess = 52
-	msgUserAuthBanner  = 53
 )
 
 // SSH messages:
@@ -137,6 +133,18 @@ type userAuthFailureMsg struct {
 	PartialSuccess bool
 }
 
+// See RFC 4252, section 5.1
+const msgUserAuthSuccess = 52
+
+// See RFC 4252, section 5.4
+const msgUserAuthBanner = 53
+
+type userAuthBannerMsg struct {
+	Message string `sshtype:"53"`
+	// unused, but required to allow message parsing
+	Language string
+}
+
 // See RFC 4256, section 3.2
 const msgUserAuthInfoRequest = 60
 const msgUserAuthInfoResponse = 61
@@ -154,7 +162,7 @@ const msgChannelOpen = 90
 
 type channelOpenMsg struct {
 	ChanType         string `sshtype:"90"`
-	PeersId          uint32
+	PeersID          uint32
 	PeersWindow      uint32
 	MaxPacketSize    uint32
 	TypeSpecificData []byte `ssh:"rest"`
@@ -165,7 +173,7 @@ const msgChannelData = 94
 
 // Used for debug print outs of packets.
 type channelDataMsg struct {
-	PeersId uint32 `sshtype:"94"`
+	PeersID uint32 `sshtype:"94"`
 	Length  uint32
 	Rest    []byte `ssh:"rest"`
 }
@@ -174,8 +182,8 @@ type channelDataMsg struct {
 const msgChannelOpenConfirm = 91
 
 type channelOpenConfirmMsg struct {
-	PeersId          uint32 `sshtype:"91"`
-	MyId             uint32
+	PeersID          uint32 `sshtype:"91"`
+	MyID             uint32
 	MyWindow         uint32
 	MaxPacketSize    uint32
 	TypeSpecificData []byte `ssh:"rest"`
@@ -185,7 +193,7 @@ type channelOpenConfirmMsg struct {
 const msgChannelOpenFailure = 92
 
 type channelOpenFailureMsg struct {
-	PeersId  uint32 `sshtype:"92"`
+	PeersID  uint32 `sshtype:"92"`
 	Reason   RejectionReason
 	Message  string
 	Language string
@@ -194,7 +202,7 @@ type channelOpenFailureMsg struct {
 const msgChannelRequest = 98
 
 type channelRequestMsg struct {
-	PeersId             uint32 `sshtype:"98"`
+	PeersID             uint32 `sshtype:"98"`
 	Request             string
 	WantReply           bool
 	RequestSpecificData []byte `ssh:"rest"`
@@ -204,28 +212,28 @@ type channelRequestMsg struct {
 const msgChannelSuccess = 99
 
 type channelRequestSuccessMsg struct {
-	PeersId uint32 `sshtype:"99"`
+	PeersID uint32 `sshtype:"99"`
 }
 
 // See RFC 4254, section 5.4.
 const msgChannelFailure = 100
 
 type channelRequestFailureMsg struct {
-	PeersId uint32 `sshtype:"100"`
+	PeersID uint32 `sshtype:"100"`
 }
 
 // See RFC 4254, section 5.3
 const msgChannelClose = 97
 
 type channelCloseMsg struct {
-	PeersId uint32 `sshtype:"97"`
+	PeersID uint32 `sshtype:"97"`
 }
 
 // See RFC 4254, section 5.3
 const msgChannelEOF = 96
 
 type channelEOFMsg struct {
-	PeersId uint32 `sshtype:"96"`
+	PeersID uint32 `sshtype:"96"`
 }
 
 // See RFC 4254, section 4
@@ -255,7 +263,7 @@ type globalRequestFailureMsg struct {
 const msgChannelWindowAdjust = 93
 
 type windowAdjustMsg struct {
-	PeersId         uint32 `sshtype:"93"`
+	PeersID         uint32 `sshtype:"93"`
 	AdditionalBytes uint32
 }
 
diff --git a/vendor/golang.org/x/crypto/ssh/mux.go b/vendor/golang.org/x/crypto/ssh/mux.go
index 27a527c..f190162 100644
--- a/vendor/golang.org/x/crypto/ssh/mux.go
+++ b/vendor/golang.org/x/crypto/ssh/mux.go
@@ -278,7 +278,7 @@ func (m *mux) handleChannelOpen(packet []byte) error {
 
 	if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
 		failMsg := channelOpenFailureMsg{
-			PeersId:  msg.PeersId,
+			PeersID:  msg.PeersID,
 			Reason:   ConnectionFailed,
 			Message:  "invalid request",
 			Language: "en_US.UTF-8",
@@ -287,7 +287,7 @@ func (m *mux) handleChannelOpen(packet []byte) error {
 	}
 
 	c := m.newChannel(msg.ChanType, channelInbound, msg.TypeSpecificData)
-	c.remoteId = msg.PeersId
+	c.remoteId = msg.PeersID
 	c.maxRemotePayload = msg.MaxPacketSize
 	c.remoteWin.add(msg.PeersWindow)
 	m.incomingChannels <- c
@@ -313,7 +313,7 @@ func (m *mux) openChannel(chanType string, extra []byte) (*channel, error) {
 		PeersWindow:      ch.myWindow,
 		MaxPacketSize:    ch.maxIncomingPayload,
 		TypeSpecificData: extra,
-		PeersId:          ch.localId,
+		PeersID:          ch.localId,
 	}
 	if err := m.sendMessage(open); err != nil {
 		return nil, err
diff --git a/vendor/golang.org/x/crypto/ssh/server.go b/vendor/golang.org/x/crypto/ssh/server.go
index 8a78b7c..d0f4825 100644
--- a/vendor/golang.org/x/crypto/ssh/server.go
+++ b/vendor/golang.org/x/crypto/ssh/server.go
@@ -95,6 +95,10 @@ type ServerConfig struct {
 	// Note that RFC 4253 section 4.2 requires that this string start with
 	// "SSH-2.0-".
 	ServerVersion string
+
+	// BannerCallback, if present, is called and the return string is sent to
+	// the client after key exchange completed but before authentication.
+	BannerCallback func(conn ConnMetadata) string
 }
 
 // AddHostKey adds a private key as a host key. If an existing host
@@ -162,6 +166,9 @@ type ServerConn struct {
 // unsuccessful, it closes the connection and returns an error.  The
 // Request and NewChannel channels must be serviced, or the connection
 // will hang.
+//
+// The returned error may be of type *ServerAuthError for
+// authentication errors.
 func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewChannel, <-chan *Request, error) {
 	fullConf := *config
 	fullConf.SetDefaults()
@@ -252,7 +259,7 @@ func (s *connection) serverHandshake(config *ServerConfig) (*Permissions, error)
 func isAcceptableAlgo(algo string) bool {
 	switch algo {
 	case KeyAlgoRSA, KeyAlgoDSA, KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, KeyAlgoED25519,
-		CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01:
+		CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01:
 		return true
 	}
 	return false
@@ -288,12 +295,13 @@ func checkSourceAddress(addr net.Addr, sourceAddrs string) error {
 	return fmt.Errorf("ssh: remote address %v is not allowed because of source-address restriction", addr)
 }
 
-// ServerAuthError implements the error interface. It appends any authentication
-// errors that may occur, and is returned if all of the authentication methods
-// provided by the user failed to authenticate.
+// ServerAuthError represents server authentication errors and is
+// sometimes returned by NewServerConn. It appends any authentication
+// errors that may occur, and is returned if all of the authentication
+// methods provided by the user failed to authenticate.
 type ServerAuthError struct {
 	// Errors contains authentication errors returned by the authentication
-	// callback methods.
+	// callback methods. The first entry is typically ErrNoAuth.
 	Errors []error
 }
 
@@ -305,6 +313,13 @@ func (l ServerAuthError) Error() string {
 	return "[" + strings.Join(errs, ", ") + "]"
 }
 
+// ErrNoAuth is the error value returned if no
+// authentication method has been passed yet. This happens as a normal
+// part of the authentication loop, since the client first tries
+// 'none' authentication to discover available methods.
+// It is returned in ServerAuthError.Errors from NewServerConn.
+var ErrNoAuth = errors.New("ssh: no auth passed yet")
+
 func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, error) {
 	sessionID := s.transport.getSessionID()
 	var cache pubKeyCache
@@ -312,6 +327,7 @@ func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, err
 
 	authFailures := 0
 	var authErrs []error
+	var displayedBanner bool
 
 userAuthLoop:
 	for {
@@ -343,8 +359,22 @@ userAuthLoop:
 		}
 
 		s.user = userAuthReq.User
+
+		if !displayedBanner && config.BannerCallback != nil {
+			displayedBanner = true
+			msg := config.BannerCallback(s)
+			if msg != "" {
+				bannerMsg := &userAuthBannerMsg{
+					Message: msg,
+				}
+				if err := s.transport.writePacket(Marshal(bannerMsg)); err != nil {
+					return nil, err
+				}
+			}
+		}
+
 		perms = nil
-		authErr := errors.New("no auth passed yet")
+		authErr := ErrNoAuth
 
 		switch userAuthReq.Method {
 		case "none":
diff --git a/vendor/golang.org/x/crypto/ssh/session.go b/vendor/golang.org/x/crypto/ssh/session.go
index cc06e03..d3321f6 100644
--- a/vendor/golang.org/x/crypto/ssh/session.go
+++ b/vendor/golang.org/x/crypto/ssh/session.go
@@ -406,7 +406,7 @@ func (s *Session) Wait() error {
 		s.stdinPipeWriter.Close()
 	}
 	var copyError error
-	for _ = range s.copyFuncs {
+	for range s.copyFuncs {
 		if err := <-s.errors; err != nil && copyError == nil {
 			copyError = err
 		}
diff --git a/vendor/golang.org/x/crypto/ssh/streamlocal.go b/vendor/golang.org/x/crypto/ssh/streamlocal.go
index a2dccc6..b171b33 100644
--- a/vendor/golang.org/x/crypto/ssh/streamlocal.go
+++ b/vendor/golang.org/x/crypto/ssh/streamlocal.go
@@ -32,6 +32,7 @@ type streamLocalChannelForwardMsg struct {
 
 // ListenUnix is similar to ListenTCP but uses a Unix domain socket.
 func (c *Client) ListenUnix(socketPath string) (net.Listener, error) {
+	c.handleForwardsOnce.Do(c.handleForwards)
 	m := streamLocalChannelForwardMsg{
 		socketPath,
 	}
diff --git a/vendor/golang.org/x/crypto/ssh/tcpip.go b/vendor/golang.org/x/crypto/ssh/tcpip.go
index acf1717..80d35f5 100644
--- a/vendor/golang.org/x/crypto/ssh/tcpip.go
+++ b/vendor/golang.org/x/crypto/ssh/tcpip.go
@@ -90,10 +90,19 @@ type channelForwardMsg struct {
 	rport uint32
 }
 
+// handleForwards starts goroutines handling forwarded connections.
+// It's called on first use by (*Client).ListenTCP to not launch
+// goroutines until needed.
+func (c *Client) handleForwards() {
+	go c.forwards.handleChannels(c.HandleChannelOpen("forwarded-tcpip"))
+	go c.forwards.handleChannels(c.HandleChannelOpen("forwarded-streamlocal@openssh.com"))
+}
+
 // ListenTCP requests the remote peer open a listening socket
 // on laddr. Incoming connections will be available by calling
 // Accept on the returned net.Listener.
 func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) {
+	c.handleForwardsOnce.Do(c.handleForwards)
 	if laddr.Port == 0 && isBrokenOpenSSHVersion(string(c.ServerVersion())) {
 		return c.autoPortListenWorkaround(laddr)
 	}
diff --git a/vendor/golang.org/x/crypto/ssh/transport.go b/vendor/golang.org/x/crypto/ssh/transport.go
index f9780e0..f6fae1d 100644
--- a/vendor/golang.org/x/crypto/ssh/transport.go
+++ b/vendor/golang.org/x/crypto/ssh/transport.go
@@ -6,6 +6,7 @@ package ssh
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"io"
 	"log"
@@ -76,17 +77,17 @@ type connectionState struct {
 // both directions are triggered by reading and writing a msgNewKey packet
 // respectively.
 func (t *transport) prepareKeyChange(algs *algorithms, kexResult *kexResult) error {
-	if ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult); err != nil {
+	ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult)
+	if err != nil {
 		return err
-	} else {
-		t.reader.pendingKeyChange <- ciph
 	}
+	t.reader.pendingKeyChange <- ciph
 
-	if ciph, err := newPacketCipher(t.writer.dir, algs.w, kexResult); err != nil {
+	ciph, err = newPacketCipher(t.writer.dir, algs.w, kexResult)
+	if err != nil {
 		return err
-	} else {
-		t.writer.pendingKeyChange <- ciph
 	}
+	t.writer.pendingKeyChange <- ciph
 
 	return nil
 }
@@ -139,7 +140,7 @@ func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) {
 			case cipher := <-s.pendingKeyChange:
 				s.packetCipher = cipher
 			default:
-				return nil, errors.New("ssh: got bogus newkeys message.")
+				return nil, errors.New("ssh: got bogus newkeys message")
 			}
 
 		case msgDisconnect:
@@ -232,52 +233,22 @@ var (
 	clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}}
 )
 
-// generateKeys generates key material for IV, MAC and encryption.
-func generateKeys(d direction, algs directionAlgorithms, kex *kexResult) (iv, key, macKey []byte) {
+// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
+// described in RFC 4253, section 6.4. direction should either be serverKeys
+// (to setup server->client keys) or clientKeys (for client->server keys).
+func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
 	cipherMode := cipherModes[algs.Cipher]
 	macMode := macModes[algs.MAC]
 
-	iv = make([]byte, cipherMode.ivSize)
-	key = make([]byte, cipherMode.keySize)
-	macKey = make([]byte, macMode.keySize)
+	iv := make([]byte, cipherMode.ivSize)
+	key := make([]byte, cipherMode.keySize)
+	macKey := make([]byte, macMode.keySize)
 
 	generateKeyMaterial(iv, d.ivTag, kex)
 	generateKeyMaterial(key, d.keyTag, kex)
 	generateKeyMaterial(macKey, d.macKeyTag, kex)
-	return
-}
-
-// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
-// described in RFC 4253, section 6.4. direction should either be serverKeys
-// (to setup server->client keys) or clientKeys (for client->server keys).
-func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
-	iv, key, macKey := generateKeys(d, algs, kex)
-
-	if algs.Cipher == gcmCipherID {
-		return newGCMCipher(iv, key, macKey)
-	}
-
-	if algs.Cipher == aes128cbcID {
-		return newAESCBCCipher(iv, key, macKey, algs)
-	}
-
-	if algs.Cipher == tripledescbcID {
-		return newTripleDESCBCCipher(iv, key, macKey, algs)
-	}
 
-	c := &streamPacketCipher{
-		mac: macModes[algs.MAC].new(macKey),
-		etm: macModes[algs.MAC].etm,
-	}
-	c.macResult = make([]byte, c.mac.Size())
-
-	var err error
-	c.cipher, err = cipherModes[algs.Cipher].createStream(key, iv)
-	if err != nil {
-		return nil, err
-	}
-
-	return c, nil
+	return cipherModes[algs.Cipher].create(key, iv, macKey, algs)
 }
 
 // generateKeyMaterial fills out with key material generated from tag, K, H
@@ -342,7 +313,7 @@ func readVersion(r io.Reader) ([]byte, error) {
 	var ok bool
 	var buf [1]byte
 
-	for len(versionString) < maxVersionStringBytes {
+	for length := 0; length < maxVersionStringBytes; length++ {
 		_, err := io.ReadFull(r, buf[:])
 		if err != nil {
 			return nil, err
@@ -350,6 +321,13 @@ func readVersion(r io.Reader) ([]byte, error) {
 		// The RFC says that the version should be terminated with \r\n
 		// but several SSH servers actually only send a \n.
 		if buf[0] == '\n' {
+			if !bytes.HasPrefix(versionString, []byte("SSH-")) {
+				// RFC 4253 says we need to ignore all version string lines
+				// except the one containing the SSH version (provided that
+				// all the lines do not exceed 255 bytes in total).
+				versionString = versionString[:0]
+				continue
+			}
 			ok = true
 			break
 		}