mirror of
https://github.com/go-gitea/gitea.git
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647 lines
19 KiB
Go
647 lines
19 KiB
Go
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// Copyright 2012 The Gorilla Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package securecookie
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"crypto/subtle"
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"encoding/base64"
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"encoding/gob"
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"encoding/json"
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"fmt"
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"hash"
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"io"
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"strconv"
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"strings"
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"time"
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)
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// Error is the interface of all errors returned by functions in this library.
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type Error interface {
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error
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// IsUsage returns true for errors indicating the client code probably
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// uses this library incorrectly. For example, the client may have
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// failed to provide a valid hash key, or may have failed to configure
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// the Serializer adequately for encoding value.
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IsUsage() bool
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// IsDecode returns true for errors indicating that a cookie could not
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// be decoded and validated. Since cookies are usually untrusted
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// user-provided input, errors of this type should be expected.
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// Usually, the proper action is simply to reject the request.
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IsDecode() bool
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// IsInternal returns true for unexpected errors occurring in the
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// securecookie implementation.
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IsInternal() bool
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// Cause, if it returns a non-nil value, indicates that this error was
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// propagated from some underlying library. If this method returns nil,
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// this error was raised directly by this library.
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//
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// Cause is provided principally for debugging/logging purposes; it is
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// rare that application logic should perform meaningfully different
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// logic based on Cause. See, for example, the caveats described on
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// (MultiError).Cause().
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Cause() error
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}
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// errorType is a bitmask giving the error type(s) of an cookieError value.
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type errorType int
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const (
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usageError = errorType(1 << iota)
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decodeError
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internalError
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)
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type cookieError struct {
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typ errorType
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msg string
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cause error
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}
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func (e cookieError) IsUsage() bool { return (e.typ & usageError) != 0 }
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func (e cookieError) IsDecode() bool { return (e.typ & decodeError) != 0 }
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func (e cookieError) IsInternal() bool { return (e.typ & internalError) != 0 }
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func (e cookieError) Cause() error { return e.cause }
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func (e cookieError) Error() string {
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parts := []string{"securecookie: "}
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if e.msg == "" {
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parts = append(parts, "error")
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} else {
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parts = append(parts, e.msg)
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}
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if c := e.Cause(); c != nil {
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parts = append(parts, " - caused by: ", c.Error())
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}
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return strings.Join(parts, "")
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}
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var (
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errGeneratingIV = cookieError{typ: internalError, msg: "failed to generate random iv"}
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errNoCodecs = cookieError{typ: usageError, msg: "no codecs provided"}
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errHashKeyNotSet = cookieError{typ: usageError, msg: "hash key is not set"}
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errBlockKeyNotSet = cookieError{typ: usageError, msg: "block key is not set"}
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errEncodedValueTooLong = cookieError{typ: usageError, msg: "the value is too long"}
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errValueToDecodeTooLong = cookieError{typ: decodeError, msg: "the value is too long"}
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errTimestampInvalid = cookieError{typ: decodeError, msg: "invalid timestamp"}
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errTimestampTooNew = cookieError{typ: decodeError, msg: "timestamp is too new"}
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errTimestampExpired = cookieError{typ: decodeError, msg: "expired timestamp"}
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errDecryptionFailed = cookieError{typ: decodeError, msg: "the value could not be decrypted"}
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errValueNotByte = cookieError{typ: decodeError, msg: "value not a []byte."}
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errValueNotBytePtr = cookieError{typ: decodeError, msg: "value not a pointer to []byte."}
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// ErrMacInvalid indicates that cookie decoding failed because the HMAC
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// could not be extracted and verified. Direct use of this error
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// variable is deprecated; it is public only for legacy compatibility,
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// and may be privatized in the future, as it is rarely useful to
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// distinguish between this error and other Error implementations.
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ErrMacInvalid = cookieError{typ: decodeError, msg: "the value is not valid"}
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)
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// Codec defines an interface to encode and decode cookie values.
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type Codec interface {
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Encode(name string, value interface{}) (string, error)
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Decode(name, value string, dst interface{}) error
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}
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// New returns a new SecureCookie.
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//
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// hashKey is required, used to authenticate values using HMAC. Create it using
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// GenerateRandomKey(). It is recommended to use a key with 32 or 64 bytes.
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//
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// blockKey is optional, used to encrypt values. Create it using
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// GenerateRandomKey(). The key length must correspond to the block size
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// of the encryption algorithm. For AES, used by default, valid lengths are
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// 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
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// The default encoder used for cookie serialization is encoding/gob.
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//
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// Note that keys created using GenerateRandomKey() are not automatically
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// persisted. New keys will be created when the application is restarted, and
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// previously issued cookies will not be able to be decoded.
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func New(hashKey, blockKey []byte) *SecureCookie {
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s := &SecureCookie{
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hashKey: hashKey,
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blockKey: blockKey,
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hashFunc: sha256.New,
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maxAge: 86400 * 30,
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maxLength: 4096,
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sz: GobEncoder{},
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}
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if hashKey == nil {
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s.err = errHashKeyNotSet
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}
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if blockKey != nil {
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s.BlockFunc(aes.NewCipher)
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}
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return s
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}
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// SecureCookie encodes and decodes authenticated and optionally encrypted
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// cookie values.
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type SecureCookie struct {
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hashKey []byte
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hashFunc func() hash.Hash
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blockKey []byte
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block cipher.Block
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maxLength int
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maxAge int64
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minAge int64
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err error
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sz Serializer
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// For testing purposes, the function that returns the current timestamp.
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// If not set, it will use time.Now().UTC().Unix().
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timeFunc func() int64
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}
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// Serializer provides an interface for providing custom serializers for cookie
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// values.
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type Serializer interface {
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Serialize(src interface{}) ([]byte, error)
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Deserialize(src []byte, dst interface{}) error
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}
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// GobEncoder encodes cookie values using encoding/gob. This is the simplest
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// encoder and can handle complex types via gob.Register.
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type GobEncoder struct{}
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// JSONEncoder encodes cookie values using encoding/json. Users who wish to
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// encode complex types need to satisfy the json.Marshaller and
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// json.Unmarshaller interfaces.
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type JSONEncoder struct{}
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// NopEncoder does not encode cookie values, and instead simply accepts a []byte
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// (as an interface{}) and returns a []byte. This is particularly useful when
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// you encoding an object upstream and do not wish to re-encode it.
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type NopEncoder struct{}
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// MaxLength restricts the maximum length, in bytes, for the cookie value.
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//
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// Default is 4096, which is the maximum value accepted by Internet Explorer.
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func (s *SecureCookie) MaxLength(value int) *SecureCookie {
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s.maxLength = value
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return s
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}
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// MaxAge restricts the maximum age, in seconds, for the cookie value.
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//
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// Default is 86400 * 30. Set it to 0 for no restriction.
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func (s *SecureCookie) MaxAge(value int) *SecureCookie {
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s.maxAge = int64(value)
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return s
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}
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// MinAge restricts the minimum age, in seconds, for the cookie value.
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//
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// Default is 0 (no restriction).
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func (s *SecureCookie) MinAge(value int) *SecureCookie {
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s.minAge = int64(value)
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return s
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}
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// HashFunc sets the hash function used to create HMAC.
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//
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// Default is crypto/sha256.New.
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func (s *SecureCookie) HashFunc(f func() hash.Hash) *SecureCookie {
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s.hashFunc = f
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return s
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}
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// BlockFunc sets the encryption function used to create a cipher.Block.
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//
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// Default is crypto/aes.New.
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func (s *SecureCookie) BlockFunc(f func([]byte) (cipher.Block, error)) *SecureCookie {
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if s.blockKey == nil {
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s.err = errBlockKeyNotSet
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} else if block, err := f(s.blockKey); err == nil {
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s.block = block
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} else {
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s.err = cookieError{cause: err, typ: usageError}
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}
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return s
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}
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// Encoding sets the encoding/serialization method for cookies.
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//
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// Default is encoding/gob. To encode special structures using encoding/gob,
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// they must be registered first using gob.Register().
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func (s *SecureCookie) SetSerializer(sz Serializer) *SecureCookie {
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s.sz = sz
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return s
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}
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// Encode encodes a cookie value.
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//
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// It serializes, optionally encrypts, signs with a message authentication code,
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// and finally encodes the value.
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//
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// The name argument is the cookie name. It is stored with the encoded value.
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// The value argument is the value to be encoded. It can be any value that can
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// be encoded using the currently selected serializer; see SetSerializer().
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//
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// It is the client's responsibility to ensure that value, when encoded using
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// the current serialization/encryption settings on s and then base64-encoded,
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// is shorter than the maximum permissible length.
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func (s *SecureCookie) Encode(name string, value interface{}) (string, error) {
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if s.err != nil {
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return "", s.err
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}
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if s.hashKey == nil {
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s.err = errHashKeyNotSet
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return "", s.err
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}
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var err error
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var b []byte
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// 1. Serialize.
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if b, err = s.sz.Serialize(value); err != nil {
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return "", cookieError{cause: err, typ: usageError}
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}
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// 2. Encrypt (optional).
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if s.block != nil {
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if b, err = encrypt(s.block, b); err != nil {
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return "", cookieError{cause: err, typ: usageError}
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}
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}
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b = encode(b)
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// 3. Create MAC for "name|date|value". Extra pipe to be used later.
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b = []byte(fmt.Sprintf("%s|%d|%s|", name, s.timestamp(), b))
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mac := createMac(hmac.New(s.hashFunc, s.hashKey), b[:len(b)-1])
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// Append mac, remove name.
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b = append(b, mac...)[len(name)+1:]
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// 4. Encode to base64.
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b = encode(b)
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// 5. Check length.
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if s.maxLength != 0 && len(b) > s.maxLength {
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return "", errEncodedValueTooLong
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}
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// Done.
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return string(b), nil
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}
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// Decode decodes a cookie value.
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//
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// It decodes, verifies a message authentication code, optionally decrypts and
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// finally deserializes the value.
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//
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// The name argument is the cookie name. It must be the same name used when
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// it was stored. The value argument is the encoded cookie value. The dst
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// argument is where the cookie will be decoded. It must be a pointer.
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func (s *SecureCookie) Decode(name, value string, dst interface{}) error {
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if s.err != nil {
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return s.err
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}
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if s.hashKey == nil {
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s.err = errHashKeyNotSet
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return s.err
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}
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// 1. Check length.
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if s.maxLength != 0 && len(value) > s.maxLength {
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return errValueToDecodeTooLong
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}
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// 2. Decode from base64.
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b, err := decode([]byte(value))
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if err != nil {
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return err
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}
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// 3. Verify MAC. Value is "date|value|mac".
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parts := bytes.SplitN(b, []byte("|"), 3)
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if len(parts) != 3 {
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return ErrMacInvalid
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}
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h := hmac.New(s.hashFunc, s.hashKey)
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b = append([]byte(name+"|"), b[:len(b)-len(parts[2])-1]...)
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if err = verifyMac(h, b, parts[2]); err != nil {
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return err
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}
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// 4. Verify date ranges.
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var t1 int64
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if t1, err = strconv.ParseInt(string(parts[0]), 10, 64); err != nil {
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return errTimestampInvalid
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}
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t2 := s.timestamp()
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if s.minAge != 0 && t1 > t2-s.minAge {
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return errTimestampTooNew
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}
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if s.maxAge != 0 && t1 < t2-s.maxAge {
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return errTimestampExpired
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}
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// 5. Decrypt (optional).
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b, err = decode(parts[1])
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if err != nil {
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return err
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}
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if s.block != nil {
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if b, err = decrypt(s.block, b); err != nil {
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return err
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}
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}
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// 6. Deserialize.
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if err = s.sz.Deserialize(b, dst); err != nil {
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return cookieError{cause: err, typ: decodeError}
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}
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// Done.
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return nil
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}
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// timestamp returns the current timestamp, in seconds.
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//
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// For testing purposes, the function that generates the timestamp can be
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// overridden. If not set, it will return time.Now().UTC().Unix().
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func (s *SecureCookie) timestamp() int64 {
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if s.timeFunc == nil {
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return time.Now().UTC().Unix()
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}
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return s.timeFunc()
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}
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// Authentication -------------------------------------------------------------
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// createMac creates a message authentication code (MAC).
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func createMac(h hash.Hash, value []byte) []byte {
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h.Write(value)
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return h.Sum(nil)
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}
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// verifyMac verifies that a message authentication code (MAC) is valid.
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func verifyMac(h hash.Hash, value []byte, mac []byte) error {
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mac2 := createMac(h, value)
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// Check that both MACs are of equal length, as subtle.ConstantTimeCompare
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// does not do this prior to Go 1.4.
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if len(mac) == len(mac2) && subtle.ConstantTimeCompare(mac, mac2) == 1 {
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return nil
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}
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return ErrMacInvalid
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}
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// Encryption -----------------------------------------------------------------
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// encrypt encrypts a value using the given block in counter mode.
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//
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// A random initialization vector (http://goo.gl/zF67k) with the length of the
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// block size is prepended to the resulting ciphertext.
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func encrypt(block cipher.Block, value []byte) ([]byte, error) {
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iv := GenerateRandomKey(block.BlockSize())
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if iv == nil {
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return nil, errGeneratingIV
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}
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// Encrypt it.
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stream := cipher.NewCTR(block, iv)
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stream.XORKeyStream(value, value)
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// Return iv + ciphertext.
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return append(iv, value...), nil
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}
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// decrypt decrypts a value using the given block in counter mode.
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//
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// The value to be decrypted must be prepended by a initialization vector
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// (http://goo.gl/zF67k) with the length of the block size.
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func decrypt(block cipher.Block, value []byte) ([]byte, error) {
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size := block.BlockSize()
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if len(value) > size {
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// Extract iv.
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iv := value[:size]
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// Extract ciphertext.
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value = value[size:]
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// Decrypt it.
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stream := cipher.NewCTR(block, iv)
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stream.XORKeyStream(value, value)
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return value, nil
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}
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return nil, errDecryptionFailed
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}
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// Serialization --------------------------------------------------------------
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// Serialize encodes a value using gob.
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||
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func (e GobEncoder) Serialize(src interface{}) ([]byte, error) {
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||
|
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 dat, ok := dst.(*[]byte); ok {
|
||
|
*dat = src
|
||
|
return nil
|
||
|
}
|
||
|
return errValueNotBytePtr
|
||
|
}
|
||
|
|
||
|
// 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
|
||
|
}
|