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Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/server.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/server.go | 593 |
1 files changed, 0 insertions, 593 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/server.go b/vendor/golang.org/x/crypto/ssh/server.go deleted file mode 100644 index d0f4825..0000000 --- a/vendor/golang.org/x/crypto/ssh/server.go +++ /dev/null @@ -1,593 +0,0 @@ -// Copyright 2011 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 ssh - -import ( - "bytes" - "errors" - "fmt" - "io" - "net" - "strings" -) - -// The Permissions type holds fine-grained permissions that are -// specific to a user or a specific authentication method for a user. -// The Permissions value for a successful authentication attempt is -// available in ServerConn, so it can be used to pass information from -// the user-authentication phase to the application layer. -type Permissions struct { - // CriticalOptions indicate restrictions to the default - // permissions, and are typically used in conjunction with - // user certificates. The standard for SSH certificates - // defines "force-command" (only allow the given command to - // execute) and "source-address" (only allow connections from - // the given address). The SSH package currently only enforces - // the "source-address" critical option. It is up to server - // implementations to enforce other critical options, such as - // "force-command", by checking them after the SSH handshake - // is successful. In general, SSH servers should reject - // connections that specify critical options that are unknown - // or not supported. - CriticalOptions map[string]string - - // Extensions are extra functionality that the server may - // offer on authenticated connections. Lack of support for an - // extension does not preclude authenticating a user. Common - // extensions are "permit-agent-forwarding", - // "permit-X11-forwarding". The Go SSH library currently does - // not act on any extension, and it is up to server - // implementations to honor them. Extensions can be used to - // pass data from the authentication callbacks to the server - // application layer. - Extensions map[string]string -} - -// ServerConfig holds server specific configuration data. -type ServerConfig struct { - // Config contains configuration shared between client and server. - Config - - hostKeys []Signer - - // NoClientAuth is true if clients are allowed to connect without - // authenticating. - NoClientAuth bool - - // MaxAuthTries specifies the maximum number of authentication attempts - // permitted per connection. If set to a negative number, the number of - // attempts are unlimited. If set to zero, the number of attempts are limited - // to 6. - MaxAuthTries int - - // PasswordCallback, if non-nil, is called when a user - // attempts to authenticate using a password. - PasswordCallback func(conn ConnMetadata, password []byte) (*Permissions, error) - - // PublicKeyCallback, if non-nil, is called when a client - // offers a public key for authentication. It must return a nil error - // if the given public key can be used to authenticate the - // given user. For example, see CertChecker.Authenticate. A - // call to this function does not guarantee that the key - // offered is in fact used to authenticate. To record any data - // depending on the public key, store it inside a - // Permissions.Extensions entry. - PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error) - - // KeyboardInteractiveCallback, if non-nil, is called when - // keyboard-interactive authentication is selected (RFC - // 4256). The client object's Challenge function should be - // used to query the user. The callback may offer multiple - // Challenge rounds. To avoid information leaks, the client - // should be presented a challenge even if the user is - // unknown. - KeyboardInteractiveCallback func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error) - - // AuthLogCallback, if non-nil, is called to log all authentication - // attempts. - AuthLogCallback func(conn ConnMetadata, method string, err error) - - // ServerVersion is the version identification string to announce in - // the public handshake. - // If empty, a reasonable default is used. - // 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 -// key exists with the same algorithm, it is overwritten. Each server -// config must have at least one host key. -func (s *ServerConfig) AddHostKey(key Signer) { - for i, k := range s.hostKeys { - if k.PublicKey().Type() == key.PublicKey().Type() { - s.hostKeys[i] = key - return - } - } - - s.hostKeys = append(s.hostKeys, key) -} - -// cachedPubKey contains the results of querying whether a public key is -// acceptable for a user. -type cachedPubKey struct { - user string - pubKeyData []byte - result error - perms *Permissions -} - -const maxCachedPubKeys = 16 - -// pubKeyCache caches tests for public keys. Since SSH clients -// will query whether a public key is acceptable before attempting to -// authenticate with it, we end up with duplicate queries for public -// key validity. The cache only applies to a single ServerConn. -type pubKeyCache struct { - keys []cachedPubKey -} - -// get returns the result for a given user/algo/key tuple. -func (c *pubKeyCache) get(user string, pubKeyData []byte) (cachedPubKey, bool) { - for _, k := range c.keys { - if k.user == user && bytes.Equal(k.pubKeyData, pubKeyData) { - return k, true - } - } - return cachedPubKey{}, false -} - -// add adds the given tuple to the cache. -func (c *pubKeyCache) add(candidate cachedPubKey) { - if len(c.keys) < maxCachedPubKeys { - c.keys = append(c.keys, candidate) - } -} - -// ServerConn is an authenticated SSH connection, as seen from the -// server -type ServerConn struct { - Conn - - // If the succeeding authentication callback returned a - // non-nil Permissions pointer, it is stored here. - Permissions *Permissions -} - -// NewServerConn starts a new SSH server with c as the underlying -// transport. It starts with a handshake and, if the handshake is -// 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() - if fullConf.MaxAuthTries == 0 { - fullConf.MaxAuthTries = 6 - } - - s := &connection{ - sshConn: sshConn{conn: c}, - } - perms, err := s.serverHandshake(&fullConf) - if err != nil { - c.Close() - return nil, nil, nil, err - } - return &ServerConn{s, perms}, s.mux.incomingChannels, s.mux.incomingRequests, nil -} - -// signAndMarshal signs the data with the appropriate algorithm, -// and serializes the result in SSH wire format. -func signAndMarshal(k Signer, rand io.Reader, data []byte) ([]byte, error) { - sig, err := k.Sign(rand, data) - if err != nil { - return nil, err - } - - return Marshal(sig), nil -} - -// handshake performs key exchange and user authentication. -func (s *connection) serverHandshake(config *ServerConfig) (*Permissions, error) { - if len(config.hostKeys) == 0 { - return nil, errors.New("ssh: server has no host keys") - } - - if !config.NoClientAuth && config.PasswordCallback == nil && config.PublicKeyCallback == nil && config.KeyboardInteractiveCallback == nil { - return nil, errors.New("ssh: no authentication methods configured but NoClientAuth is also false") - } - - if config.ServerVersion != "" { - s.serverVersion = []byte(config.ServerVersion) - } else { - s.serverVersion = []byte(packageVersion) - } - var err error - s.clientVersion, err = exchangeVersions(s.sshConn.conn, s.serverVersion) - if err != nil { - return nil, err - } - - tr := newTransport(s.sshConn.conn, config.Rand, false /* not client */) - s.transport = newServerTransport(tr, s.clientVersion, s.serverVersion, config) - - if err := s.transport.waitSession(); err != nil { - return nil, err - } - - // We just did the key change, so the session ID is established. - s.sessionID = s.transport.getSessionID() - - var packet []byte - if packet, err = s.transport.readPacket(); err != nil { - return nil, err - } - - var serviceRequest serviceRequestMsg - if err = Unmarshal(packet, &serviceRequest); err != nil { - return nil, err - } - if serviceRequest.Service != serviceUserAuth { - return nil, errors.New("ssh: requested service '" + serviceRequest.Service + "' before authenticating") - } - serviceAccept := serviceAcceptMsg{ - Service: serviceUserAuth, - } - if err := s.transport.writePacket(Marshal(&serviceAccept)); err != nil { - return nil, err - } - - perms, err := s.serverAuthenticate(config) - if err != nil { - return nil, err - } - s.mux = newMux(s.transport) - return perms, err -} - -func isAcceptableAlgo(algo string) bool { - switch algo { - case KeyAlgoRSA, KeyAlgoDSA, KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, KeyAlgoED25519, - CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01: - return true - } - return false -} - -func checkSourceAddress(addr net.Addr, sourceAddrs string) error { - if addr == nil { - return errors.New("ssh: no address known for client, but source-address match required") - } - - tcpAddr, ok := addr.(*net.TCPAddr) - if !ok { - return fmt.Errorf("ssh: remote address %v is not an TCP address when checking source-address match", addr) - } - - for _, sourceAddr := range strings.Split(sourceAddrs, ",") { - if allowedIP := net.ParseIP(sourceAddr); allowedIP != nil { - if allowedIP.Equal(tcpAddr.IP) { - return nil - } - } else { - _, ipNet, err := net.ParseCIDR(sourceAddr) - if err != nil { - return fmt.Errorf("ssh: error parsing source-address restriction %q: %v", sourceAddr, err) - } - - if ipNet.Contains(tcpAddr.IP) { - return nil - } - } - } - - return fmt.Errorf("ssh: remote address %v is not allowed because of source-address restriction", addr) -} - -// 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. The first entry is typically ErrNoAuth. - Errors []error -} - -func (l ServerAuthError) Error() string { - var errs []string - for _, err := range l.Errors { - errs = append(errs, err.Error()) - } - 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 - var perms *Permissions - - authFailures := 0 - var authErrs []error - var displayedBanner bool - -userAuthLoop: - for { - if authFailures >= config.MaxAuthTries && config.MaxAuthTries > 0 { - discMsg := &disconnectMsg{ - Reason: 2, - Message: "too many authentication failures", - } - - if err := s.transport.writePacket(Marshal(discMsg)); err != nil { - return nil, err - } - - return nil, discMsg - } - - var userAuthReq userAuthRequestMsg - if packet, err := s.transport.readPacket(); err != nil { - if err == io.EOF { - return nil, &ServerAuthError{Errors: authErrs} - } - return nil, err - } else if err = Unmarshal(packet, &userAuthReq); err != nil { - return nil, err - } - - if userAuthReq.Service != serviceSSH { - return nil, errors.New("ssh: client attempted to negotiate for unknown service: " + userAuthReq.Service) - } - - 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 := ErrNoAuth - - switch userAuthReq.Method { - case "none": - if config.NoClientAuth { - authErr = nil - } - - // allow initial attempt of 'none' without penalty - if authFailures == 0 { - authFailures-- - } - case "password": - if config.PasswordCallback == nil { - authErr = errors.New("ssh: password auth not configured") - break - } - payload := userAuthReq.Payload - if len(payload) < 1 || payload[0] != 0 { - return nil, parseError(msgUserAuthRequest) - } - payload = payload[1:] - password, payload, ok := parseString(payload) - if !ok || len(payload) > 0 { - return nil, parseError(msgUserAuthRequest) - } - - perms, authErr = config.PasswordCallback(s, password) - case "keyboard-interactive": - if config.KeyboardInteractiveCallback == nil { - authErr = errors.New("ssh: keyboard-interactive auth not configubred") - break - } - - prompter := &sshClientKeyboardInteractive{s} - perms, authErr = config.KeyboardInteractiveCallback(s, prompter.Challenge) - case "publickey": - if config.PublicKeyCallback == nil { - authErr = errors.New("ssh: publickey auth not configured") - break - } - payload := userAuthReq.Payload - if len(payload) < 1 { - return nil, parseError(msgUserAuthRequest) - } - isQuery := payload[0] == 0 - payload = payload[1:] - algoBytes, payload, ok := parseString(payload) - if !ok { - return nil, parseError(msgUserAuthRequest) - } - algo := string(algoBytes) - if !isAcceptableAlgo(algo) { - authErr = fmt.Errorf("ssh: algorithm %q not accepted", algo) - break - } - - pubKeyData, payload, ok := parseString(payload) - if !ok { - return nil, parseError(msgUserAuthRequest) - } - - pubKey, err := ParsePublicKey(pubKeyData) - if err != nil { - return nil, err - } - - candidate, ok := cache.get(s.user, pubKeyData) - if !ok { - candidate.user = s.user - candidate.pubKeyData = pubKeyData - candidate.perms, candidate.result = config.PublicKeyCallback(s, pubKey) - if candidate.result == nil && candidate.perms != nil && candidate.perms.CriticalOptions != nil && candidate.perms.CriticalOptions[sourceAddressCriticalOption] != "" { - candidate.result = checkSourceAddress( - s.RemoteAddr(), - candidate.perms.CriticalOptions[sourceAddressCriticalOption]) - } - cache.add(candidate) - } - - if isQuery { - // The client can query if the given public key - // would be okay. - - if len(payload) > 0 { - return nil, parseError(msgUserAuthRequest) - } - - if candidate.result == nil { - okMsg := userAuthPubKeyOkMsg{ - Algo: algo, - PubKey: pubKeyData, - } - if err = s.transport.writePacket(Marshal(&okMsg)); err != nil { - return nil, err - } - continue userAuthLoop - } - authErr = candidate.result - } else { - sig, payload, ok := parseSignature(payload) - if !ok || len(payload) > 0 { - return nil, parseError(msgUserAuthRequest) - } - // Ensure the public key algo and signature algo - // are supported. Compare the private key - // algorithm name that corresponds to algo with - // sig.Format. This is usually the same, but - // for certs, the names differ. - if !isAcceptableAlgo(sig.Format) { - break - } - signedData := buildDataSignedForAuth(sessionID, userAuthReq, algoBytes, pubKeyData) - - if err := pubKey.Verify(signedData, sig); err != nil { - return nil, err - } - - authErr = candidate.result - perms = candidate.perms - } - default: - authErr = fmt.Errorf("ssh: unknown method %q", userAuthReq.Method) - } - - authErrs = append(authErrs, authErr) - - if config.AuthLogCallback != nil { - config.AuthLogCallback(s, userAuthReq.Method, authErr) - } - - if authErr == nil { - break userAuthLoop - } - - authFailures++ - - var failureMsg userAuthFailureMsg - if config.PasswordCallback != nil { - failureMsg.Methods = append(failureMsg.Methods, "password") - } - if config.PublicKeyCallback != nil { - failureMsg.Methods = append(failureMsg.Methods, "publickey") - } - if config.KeyboardInteractiveCallback != nil { - failureMsg.Methods = append(failureMsg.Methods, "keyboard-interactive") - } - - if len(failureMsg.Methods) == 0 { - return nil, errors.New("ssh: no authentication methods configured but NoClientAuth is also false") - } - - if err := s.transport.writePacket(Marshal(&failureMsg)); err != nil { - return nil, err - } - } - - if err := s.transport.writePacket([]byte{msgUserAuthSuccess}); err != nil { - return nil, err - } - return perms, nil -} - -// sshClientKeyboardInteractive implements a ClientKeyboardInteractive by -// asking the client on the other side of a ServerConn. -type sshClientKeyboardInteractive struct { - *connection -} - -func (c *sshClientKeyboardInteractive) Challenge(user, instruction string, questions []string, echos []bool) (answers []string, err error) { - if len(questions) != len(echos) { - return nil, errors.New("ssh: echos and questions must have equal length") - } - - var prompts []byte - for i := range questions { - prompts = appendString(prompts, questions[i]) - prompts = appendBool(prompts, echos[i]) - } - - if err := c.transport.writePacket(Marshal(&userAuthInfoRequestMsg{ - Instruction: instruction, - NumPrompts: uint32(len(questions)), - Prompts: prompts, - })); err != nil { - return nil, err - } - - packet, err := c.transport.readPacket() - if err != nil { - return nil, err - } - if packet[0] != msgUserAuthInfoResponse { - return nil, unexpectedMessageError(msgUserAuthInfoResponse, packet[0]) - } - packet = packet[1:] - - n, packet, ok := parseUint32(packet) - if !ok || int(n) != len(questions) { - return nil, parseError(msgUserAuthInfoResponse) - } - - for i := uint32(0); i < n; i++ { - ans, rest, ok := parseString(packet) - if !ok { - return nil, parseError(msgUserAuthInfoResponse) - } - - answers = append(answers, string(ans)) - packet = rest - } - if len(packet) != 0 { - return nil, errors.New("ssh: junk at end of message") - } - - return answers, nil -} |