mirror of
https://github.com/Luzifer/cloudkeys-go.git
synced 2024-11-10 07:00:08 +00:00
429 lines
11 KiB
Go
429 lines
11 KiB
Go
// 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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"errors"
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"fmt"
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"hash"
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"io"
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"strconv"
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"time"
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)
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var (
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errNoCodecs = errors.New("securecookie: no codecs provided")
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errHashKeyNotSet = errors.New("securecookie: hash key is not set")
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ErrMacInvalid = errors.New("securecookie: 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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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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}
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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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// 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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// 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 = errors.New("securecookie: block key is not set")
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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 = err
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}
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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, and
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// 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 encoding/gob. To store special structures, they must be
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// registered first using gob.Register().
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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 = serialize(value); err != nil {
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return "", err
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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 "", err
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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 "", errors.New("securecookie: the value is too long")
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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 errors.New("securecookie: the value is too long")
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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 errors.New("securecookie: invalid value %v")
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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 errors.New("securecookie: invalid timestamp")
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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 errors.New("securecookie: timestamp is too new")
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}
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if s.maxAge != 0 && t1 < t2-s.maxAge {
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return errors.New("securecookie: expired timestamp")
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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 = deserialize(b, dst); err != nil {
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return err
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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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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, errors.New("securecookie: failed to generate random iv")
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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, errors.New("securecookie: the value could not be decrypted")
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}
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// Serialization --------------------------------------------------------------
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// serialize encodes a value using gob.
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func serialize(src interface{}) ([]byte, error) {
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buf := new(bytes.Buffer)
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enc := gob.NewEncoder(buf)
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if err := enc.Encode(src); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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// deserialize decodes a value using gob.
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func deserialize(src []byte, dst interface{}) error {
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dec := gob.NewDecoder(bytes.NewBuffer(src))
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if err := dec.Decode(dst); err != nil {
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return err
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}
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return nil
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}
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// Encoding -------------------------------------------------------------------
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// encode encodes a value using base64.
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func encode(value []byte) []byte {
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encoded := make([]byte, base64.URLEncoding.EncodedLen(len(value)))
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base64.URLEncoding.Encode(encoded, value)
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return encoded
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}
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// decode decodes a cookie using base64.
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func decode(value []byte) ([]byte, error) {
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decoded := make([]byte, base64.URLEncoding.DecodedLen(len(value)))
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b, err := base64.URLEncoding.Decode(decoded, value)
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if err != nil {
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return nil, err
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}
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return decoded[:b], nil
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}
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// Helpers --------------------------------------------------------------------
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// GenerateRandomKey creates a random key with the given strength.
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func GenerateRandomKey(strength int) []byte {
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k := make([]byte, strength)
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if _, err := io.ReadFull(rand.Reader, k); err != nil {
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return nil
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}
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return k
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}
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// CodecsFromPairs returns a slice of SecureCookie instances.
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//
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// It is a convenience function to create a list of codecs for key rotation.
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func CodecsFromPairs(keyPairs ...[]byte) []Codec {
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codecs := make([]Codec, len(keyPairs)/2+len(keyPairs)%2)
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for i := 0; i < len(keyPairs); i += 2 {
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var blockKey []byte
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if i+1 < len(keyPairs) {
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blockKey = keyPairs[i+1]
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}
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codecs[i/2] = New(keyPairs[i], blockKey)
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}
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return codecs
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}
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// EncodeMulti encodes a cookie value using a group of codecs.
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//
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// The codecs are tried in order. Multiple codecs are accepted to allow
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// key rotation.
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func EncodeMulti(name string, value interface{}, codecs ...Codec) (string, error) {
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if len(codecs) == 0 {
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return "", errNoCodecs
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}
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var errors MultiError
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for _, codec := range codecs {
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if encoded, err := codec.Encode(name, value); err == nil {
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return encoded, nil
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} else {
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errors = append(errors, err)
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}
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}
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return "", errors
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}
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// DecodeMulti decodes a cookie value using a group of codecs.
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//
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// The codecs are tried in order. Multiple codecs are accepted to allow
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// key rotation.
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func DecodeMulti(name string, value string, dst interface{}, codecs ...Codec) error {
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if len(codecs) == 0 {
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return errNoCodecs
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}
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var errors MultiError
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for _, codec := range codecs {
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if err := codec.Decode(name, value, dst); err == nil {
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return nil
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} else {
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errors = append(errors, err)
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}
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}
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return errors
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}
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// MultiError groups multiple errors.
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type MultiError []error
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func (m MultiError) Error() string {
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s, n := "", 0
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for _, e := range m {
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if e != nil {
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if n == 0 {
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s = e.Error()
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}
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n++
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}
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}
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switch n {
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case 0:
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return "(0 errors)"
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case 1:
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return s
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case 2:
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return s + " (and 1 other error)"
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}
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return fmt.Sprintf("%s (and %d other errors)", s, n-1)
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}
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