diff options
Diffstat (limited to 'vendor/github.com/gorilla/securecookie/securecookie.go')
| -rw-r--r-- | vendor/github.com/gorilla/securecookie/securecookie.go | 646 |
1 files changed, 646 insertions, 0 deletions
diff --git a/vendor/github.com/gorilla/securecookie/securecookie.go b/vendor/github.com/gorilla/securecookie/securecookie.go new file mode 100644 index 0000000..83dd606 --- /dev/null +++ b/vendor/github.com/gorilla/securecookie/securecookie.go @@ -0,0 +1,646 @@ +// Copyright 2012 The Gorilla 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 securecookie + +import ( + "bytes" + "crypto/aes" + "crypto/cipher" + "crypto/hmac" + "crypto/rand" + "crypto/sha256" + "crypto/subtle" + "encoding/base64" + "encoding/gob" + "encoding/json" + "fmt" + "hash" + "io" + "strconv" + "strings" + "time" +) + +// Error is the interface of all errors returned by functions in this library. +type Error interface { + error + + // IsUsage returns true for errors indicating the client code probably + // uses this library incorrectly. For example, the client may have + // failed to provide a valid hash key, or may have failed to configure + // the Serializer adequately for encoding value. + IsUsage() bool + + // IsDecode returns true for errors indicating that a cookie could not + // be decoded and validated. Since cookies are usually untrusted + // user-provided input, errors of this type should be expected. + // Usually, the proper action is simply to reject the request. + IsDecode() bool + + // IsInternal returns true for unexpected errors occurring in the + // securecookie implementation. + IsInternal() bool + + // Cause, if it returns a non-nil value, indicates that this error was + // propagated from some underlying library. If this method returns nil, + // this error was raised directly by this library. + // + // Cause is provided principally for debugging/logging purposes; it is + // rare that application logic should perform meaningfully different + // logic based on Cause. See, for example, the caveats described on + // (MultiError).Cause(). + Cause() error +} + +// errorType is a bitmask giving the error type(s) of an cookieError value. +type errorType int + +const ( + usageError = errorType(1 << iota) + decodeError + internalError +) + +type cookieError struct { + typ errorType + msg string + cause error +} + +func (e cookieError) IsUsage() bool { return (e.typ & usageError) != 0 } +func (e cookieError) IsDecode() bool { return (e.typ & decodeError) != 0 } +func (e cookieError) IsInternal() bool { return (e.typ & internalError) != 0 } + +func (e cookieError) Cause() error { return e.cause } + +func (e cookieError) Error() string { + parts := []string{"securecookie: "} + if e.msg == "" { + parts = append(parts, "error") + } else { + parts = append(parts, e.msg) + } + if c := e.Cause(); c != nil { + parts = append(parts, " - caused by: ", c.Error()) + } + return strings.Join(parts, "") +} + +var ( + errGeneratingIV = cookieError{typ: internalError, msg: "failed to generate random iv"} + + errNoCodecs = cookieError{typ: usageError, msg: "no codecs provided"} + errHashKeyNotSet = cookieError{typ: usageError, msg: "hash key is not set"} + errBlockKeyNotSet = cookieError{typ: usageError, msg: "block key is not set"} + errEncodedValueTooLong = cookieError{typ: usageError, msg: "the value is too long"} + + errValueToDecodeTooLong = cookieError{typ: decodeError, msg: "the value is too long"} + errTimestampInvalid = cookieError{typ: decodeError, msg: "invalid timestamp"} + errTimestampTooNew = cookieError{typ: decodeError, msg: "timestamp is too new"} + errTimestampExpired = cookieError{typ: decodeError, msg: "expired timestamp"} + errDecryptionFailed = cookieError{typ: decodeError, msg: "the value could not be decrypted"} + errValueNotByte = cookieError{typ: decodeError, msg: "value not a []byte."} + + // ErrMacInvalid indicates that cookie decoding failed because the HMAC + // could not be extracted and verified. Direct use of this error + // variable is deprecated; it is public only for legacy compatibility, + // and may be privatized in the future, as it is rarely useful to + // distinguish between this error and other Error implementations. + ErrMacInvalid = cookieError{typ: decodeError, msg: "the value is not valid"} +) + +// Codec defines an interface to encode and decode cookie values. +type Codec interface { + Encode(name string, value interface{}) (string, error) + Decode(name, value string, dst interface{}) error +} + +// New returns a new SecureCookie. +// +// hashKey is required, used to authenticate values using HMAC. Create it using +// GenerateRandomKey(). It is recommended to use a key with 32 or 64 bytes. +// +// blockKey is optional, used to encrypt values. Create it using +// GenerateRandomKey(). The key length must correspond to the block size +// of the encryption algorithm. For AES, used by default, valid lengths are +// 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256. +// The default encoder used for cookie serialization is encoding/gob. +// +// Note that keys created using GenerateRandomKey() are not automatically +// persisted. New keys will be created when the application is restarted, and +// previously issued cookies will not be able to be decoded. +func New(hashKey, blockKey []byte) *SecureCookie { + s := &SecureCookie{ + hashKey: hashKey, + blockKey: blockKey, + hashFunc: sha256.New, + maxAge: 86400 * 30, + maxLength: 4096, + sz: GobEncoder{}, + } + if hashKey == nil { + s.err = errHashKeyNotSet + } + if blockKey != nil { + s.BlockFunc(aes.NewCipher) + } + return s +} + +// SecureCookie encodes and decodes authenticated and optionally encrypted +// cookie values. +type SecureCookie struct { + hashKey []byte + hashFunc func() hash.Hash + blockKey []byte + block cipher.Block + maxLength int + maxAge int64 + minAge int64 + err error + sz Serializer + // For testing purposes, the function that returns the current timestamp. + // If not set, it will use time.Now().UTC().Unix(). + timeFunc func() int64 +} + +// Serializer provides an interface for providing custom serializers for cookie +// values. +type Serializer interface { + Serialize(src interface{}) ([]byte, error) + Deserialize(src []byte, dst interface{}) error +} + +// GobEncoder encodes cookie values using encoding/gob. This is the simplest +// encoder and can handle complex types via gob.Register. +type GobEncoder struct{} + +// JSONEncoder encodes cookie values using encoding/json. Users who wish to +// encode complex types need to satisfy the json.Marshaller and +// json.Unmarshaller interfaces. +type JSONEncoder struct{} + +// NopEncoder does not encode cookie values, and instead simply accepts a []byte +// (as an interface{}) and returns a []byte. This is particularly useful when +// you encoding an object upstream and do not wish to re-encode it. +type NopEncoder struct{} + +// MaxLength restricts the maximum length, in bytes, for the cookie value. +// +// Default is 4096, which is the maximum value accepted by Internet Explorer. +func (s *SecureCookie) MaxLength(value int) *SecureCookie { + s.maxLength = value + return s +} + +// MaxAge restricts the maximum age, in seconds, for the cookie value. +// +// Default is 86400 * 30. Set it to 0 for no restriction. +func (s *SecureCookie) MaxAge(value int) *SecureCookie { + s.maxAge = int64(value) + return s +} + +// MinAge restricts the minimum age, in seconds, for the cookie value. +// +// Default is 0 (no restriction). +func (s *SecureCookie) MinAge(value int) *SecureCookie { + s.minAge = int64(value) + return s +} + +// HashFunc sets the hash function used to create HMAC. +// +// Default is crypto/sha256.New. +func (s *SecureCookie) HashFunc(f func() hash.Hash) *SecureCookie { + s.hashFunc = f + return s +} + +// BlockFunc sets the encryption function used to create a cipher.Block. +// +// Default is crypto/aes.New. +func (s *SecureCookie) BlockFunc(f func([]byte) (cipher.Block, error)) *SecureCookie { + if s.blockKey == nil { + s.err = errBlockKeyNotSet + } else if block, err := f(s.blockKey); err == nil { + s.block = block + } else { + s.err = cookieError{cause: err, typ: usageError} + } + return s +} + +// Encoding sets the encoding/serialization method for cookies. +// +// Default is encoding/gob. To encode special structures using encoding/gob, +// they must be registered first using gob.Register(). +func (s *SecureCookie) SetSerializer(sz Serializer) *SecureCookie { + s.sz = sz + + return s +} + +// Encode encodes a cookie value. +// +// It serializes, optionally encrypts, signs with a message authentication code, +// and finally encodes the value. +// +// The name argument is the cookie name. It is stored with the encoded value. +// The value argument is the value to be encoded. It can be any value that can +// be encoded using the currently selected serializer; see SetSerializer(). +// +// It is the client's responsibility to ensure that value, when encoded using +// the current serialization/encryption settings on s and then base64-encoded, +// is shorter than the maximum permissible length. +func (s *SecureCookie) Encode(name string, value interface{}) (string, error) { + if s.err != nil { + return "", s.err + } + if s.hashKey == nil { + s.err = errHashKeyNotSet + return "", s.err + } + var err error + var b []byte + // 1. Serialize. + if b, err = s.sz.Serialize(value); err != nil { + return "", cookieError{cause: err, typ: usageError} + } + // 2. Encrypt (optional). + if s.block != nil { + if b, err = encrypt(s.block, b); err != nil { + return "", cookieError{cause: err, typ: usageError} + } + } + b = encode(b) + // 3. Create MAC for "name|date|value". Extra pipe to be used later. + b = []byte(fmt.Sprintf("%s|%d|%s|", name, s.timestamp(), b)) + mac := createMac(hmac.New(s.hashFunc, s.hashKey), b[:len(b)-1]) + // Append mac, remove name. + b = append(b, mac...)[len(name)+1:] + // 4. Encode to base64. + b = encode(b) + // 5. Check length. + if s.maxLength != 0 && len(b) > s.maxLength { + return "", errEncodedValueTooLong + } + // Done. + return string(b), nil +} + +// Decode decodes a cookie value. +// +// It decodes, verifies a message authentication code, optionally decrypts and +// finally deserializes the value. +// +// The name argument is the cookie name. It must be the same name used when +// it was stored. The value argument is the encoded cookie value. The dst +// argument is where the cookie will be decoded. It must be a pointer. +func (s *SecureCookie) Decode(name, value string, dst interface{}) error { + if s.err != nil { + return s.err + } + if s.hashKey == nil { + s.err = errHashKeyNotSet + return s.err + } + // 1. Check length. + if s.maxLength != 0 && len(value) > s.maxLength { + return errValueToDecodeTooLong + } + // 2. Decode from base64. + b, err := decode([]byte(value)) + if err != nil { + return err + } + // 3. Verify MAC. Value is "date|value|mac". + parts := bytes.SplitN(b, []byte("|"), 3) + if len(parts) != 3 { + return ErrMacInvalid + } + h := hmac.New(s.hashFunc, s.hashKey) + b = append([]byte(name+"|"), b[:len(b)-len(parts[2])-1]...) + if err = verifyMac(h, b, parts[2]); err != nil { + return err + } + // 4. Verify date ranges. + var t1 int64 + if t1, err = strconv.ParseInt(string(parts[0]), 10, 64); err != nil { + return errTimestampInvalid + } + t2 := s.timestamp() + if s.minAge != 0 && t1 > t2-s.minAge { + return errTimestampTooNew + } + if s.maxAge != 0 && t1 < t2-s.maxAge { + return errTimestampExpired + } + // 5. Decrypt (optional). + b, err = decode(parts[1]) + if err != nil { + return err + } + if s.block != nil { + if b, err = decrypt(s.block, b); err != nil { + return err + } + } + // 6. Deserialize. + if err = s.sz.Deserialize(b, dst); err != nil { + return cookieError{cause: err, typ: decodeError} + } + // Done. + return nil +} + +// timestamp returns the current timestamp, in seconds. +// +// For testing purposes, the function that generates the timestamp can be +// overridden. If not set, it will return time.Now().UTC().Unix(). +func (s *SecureCookie) timestamp() int64 { + if s.timeFunc == nil { + return time.Now().UTC().Unix() + } + return s.timeFunc() +} + +// Authentication ------------------------------------------------------------- + +// createMac creates a message authentication code (MAC). +func createMac(h hash.Hash, value []byte) []byte { + h.Write(value) + return h.Sum(nil) +} + +// verifyMac verifies that a message authentication code (MAC) is valid. +func verifyMac(h hash.Hash, value []byte, mac []byte) error { + mac2 := createMac(h, value) + // Check that both MACs are of equal length, as subtle.ConstantTimeCompare + // does not do this prior to Go 1.4. + if len(mac) == len(mac2) && subtle.ConstantTimeCompare(mac, mac2) == 1 { + return nil + } + return ErrMacInvalid +} + +// Encryption ----------------------------------------------------------------- + +// encrypt encrypts a value using the given block in counter mode. +// +// A random initialization vector (http://goo.gl/zF67k) with the length of the +// block size is prepended to the resulting ciphertext. +func encrypt(block cipher.Block, value []byte) ([]byte, error) { + iv := GenerateRandomKey(block.BlockSize()) + if iv == nil { + return nil, errGeneratingIV + } + // Encrypt it. + stream := cipher.NewCTR(block, iv) + stream.XORKeyStream(value, value) + // Return iv + ciphertext. + return append(iv, value...), nil +} + +// decrypt decrypts a value using the given block in counter mode. +// +// The value to be decrypted must be prepended by a initialization vector +// (http://goo.gl/zF67k) with the length of the block size. +func decrypt(block cipher.Block, value []byte) ([]byte, error) { + size := block.BlockSize() + if len(value) > size { + // Extract iv. + iv := value[:size] + // Extract ciphertext. + value = value[size:] + // Decrypt it. + stream := cipher.NewCTR(block, iv) + stream.XORKeyStream(value, value) + return value, nil + } + return nil, errDecryptionFailed +} + +// Serialization -------------------------------------------------------------- + +// Serialize encodes a value using gob. +func (e GobEncoder) Serialize(src interface{}) ([]byte, error) { + buf := new(bytes.Buffer) + enc := gob.NewEncoder(buf) + if err := enc.Encode(src); err != nil { + return nil, cookieError{cause: err, typ: usageError} + } + return buf.Bytes(), nil +} + +// Deserialize decodes a value using gob. +func (e GobEncoder) Deserialize(src []byte, dst interface{}) error { + dec := gob.NewDecoder(bytes.NewBuffer(src)) + if err := dec.Decode(dst); err != nil { + return cookieError{cause: err, typ: decodeError} + } + return nil +} + +// Serialize encodes a value using encoding/json. +func (e JSONEncoder) Serialize(src interface{}) ([]byte, error) { + buf := new(bytes.Buffer) + enc := json.NewEncoder(buf) + if err := enc.Encode(src); err != nil { + return nil, cookieError{cause: err, typ: usageError} + } + return buf.Bytes(), nil +} + +// Deserialize decodes a value using encoding/json. +func (e JSONEncoder) Deserialize(src []byte, dst interface{}) error { + dec := json.NewDecoder(bytes.NewReader(src)) + if err := dec.Decode(dst); err != nil { + return cookieError{cause: err, typ: decodeError} + } + return nil +} + +// Serialize passes a []byte through as-is. +func (e NopEncoder) Serialize(src interface{}) ([]byte, error) { + if b, ok := src.([]byte); ok { + return b, nil + } + + return nil, errValueNotByte +} + +// Deserialize passes a []byte through as-is. +func (e NopEncoder) Deserialize(src []byte, dst interface{}) error { + if _, ok := dst.([]byte); ok { + dst = src + return nil + } + + return errValueNotByte +} + +// Encoding ------------------------------------------------------------------- + +// encode encodes a value using base64. +func encode(value []byte) []byte { + encoded := make([]byte, base64.URLEncoding.EncodedLen(len(value))) + base64.URLEncoding.Encode(encoded, value) + return encoded +} + +// decode decodes a cookie using base64. +func decode(value []byte) ([]byte, error) { + decoded := make([]byte, base64.URLEncoding.DecodedLen(len(value))) + b, err := base64.URLEncoding.Decode(decoded, value) + if err != nil { + return nil, cookieError{cause: err, typ: decodeError, msg: "base64 decode failed"} + } + return decoded[:b], nil +} + +// Helpers -------------------------------------------------------------------- + +// GenerateRandomKey creates a random key with the given length in bytes. +// On failure, returns nil. +// +// Callers should explicitly check for the possibility of a nil return, treat +// it as a failure of the system random number generator, and not continue. +func GenerateRandomKey(length int) []byte { + k := make([]byte, length) + if _, err := io.ReadFull(rand.Reader, k); err != nil { + return nil + } + return k +} + +// CodecsFromPairs returns a slice of SecureCookie instances. +// +// It is a convenience function to create a list of codecs for key rotation. Note +// that the generated Codecs will have the default options applied: callers +// should iterate over each Codec and type-assert the underlying *SecureCookie to +// change these. +// +// Example: +// +// codecs := securecookie.CodecsFromPairs( +// []byte("new-hash-key"), +// []byte("new-block-key"), +// []byte("old-hash-key"), +// []byte("old-block-key"), +// ) +// +// // Modify each instance. +// for _, s := range codecs { +// if cookie, ok := s.(*securecookie.SecureCookie); ok { +// cookie.MaxAge(86400 * 7) +// cookie.SetSerializer(securecookie.JSONEncoder{}) +// cookie.HashFunc(sha512.New512_256) +// } +// } +// +func CodecsFromPairs(keyPairs ...[]byte) []Codec { + codecs := make([]Codec, len(keyPairs)/2+len(keyPairs)%2) + for i := 0; i < len(keyPairs); i += 2 { + var blockKey []byte + if i+1 < len(keyPairs) { + blockKey = keyPairs[i+1] + } + codecs[i/2] = New(keyPairs[i], blockKey) + } + return codecs +} + +// EncodeMulti encodes a cookie value using a group of codecs. +// +// The codecs are tried in order. Multiple codecs are accepted to allow +// key rotation. +// +// On error, may return a MultiError. +func EncodeMulti(name string, value interface{}, codecs ...Codec) (string, error) { + if len(codecs) == 0 { + return "", errNoCodecs + } + + var errors MultiError + for _, codec := range codecs { + encoded, err := codec.Encode(name, value) + if err == nil { + return encoded, nil + } + errors = append(errors, err) + } + return "", errors +} + +// DecodeMulti decodes a cookie value using a group of codecs. +// +// The codecs are tried in order. Multiple codecs are accepted to allow +// key rotation. +// +// On error, may return a MultiError. +func DecodeMulti(name string, value string, dst interface{}, codecs ...Codec) error { + if len(codecs) == 0 { + return errNoCodecs + } + + var errors MultiError + for _, codec := range codecs { + err := codec.Decode(name, value, dst) + if err == nil { + return nil + } + errors = append(errors, err) + } + return errors +} + +// MultiError groups multiple errors. +type MultiError []error + +func (m MultiError) IsUsage() bool { return m.any(func(e Error) bool { return e.IsUsage() }) } +func (m MultiError) IsDecode() bool { return m.any(func(e Error) bool { return e.IsDecode() }) } +func (m MultiError) IsInternal() bool { return m.any(func(e Error) bool { return e.IsInternal() }) } + +// Cause returns nil for MultiError; there is no unique underlying cause in the +// general case. +// +// Note: we could conceivably return a non-nil Cause only when there is exactly +// one child error with a Cause. However, it would be brittle for client code +// to rely on the arity of causes inside a MultiError, so we have opted not to +// provide this functionality. Clients which really wish to access the Causes +// of the underlying errors are free to iterate through the errors themselves. +func (m MultiError) Cause() error { return nil } + +func (m MultiError) Error() string { + s, n := "", 0 + for _, e := range m { + if e != nil { + if n == 0 { + s = e.Error() + } + n++ + } + } + switch n { + case 0: + return "(0 errors)" + case 1: + return s + case 2: + return s + " (and 1 other error)" + } + return fmt.Sprintf("%s (and %d other errors)", s, n-1) +} + +// any returns true if any element of m is an Error for which pred returns true. +func (m MultiError) any(pred func(Error) bool) bool { + for _, e := range m { + if ourErr, ok := e.(Error); ok && pred(ourErr) { + return true + } + } + return false +} |