1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package pkcs12
6
7import (
8 "bytes"
9 "crypto/cipher"
10 "crypto/des"
11 "crypto/x509/pkix"
12 "encoding/asn1"
13 "errors"
14
15 "golang.org/x/crypto/pkcs12/internal/rc2"
16)
17
18var (
19 oidPBEWithSHAAnd3KeyTripleDESCBC = asn1.ObjectIdentifier([]int{1, 2, 840, 113549, 1, 12, 1, 3})
20 oidPBEWithSHAAnd40BitRC2CBC = asn1.ObjectIdentifier([]int{1, 2, 840, 113549, 1, 12, 1, 6})
21)
22
23// pbeCipher is an abstraction of a PKCS#12 cipher.
24type pbeCipher interface {
25 // create returns a cipher.Block given a key.
26 create(key []byte) (cipher.Block, error)
27 // deriveKey returns a key derived from the given password and salt.
28 deriveKey(salt, password []byte, iterations int) []byte
29 // deriveIV returns an IV derived from the given password and salt.
30 deriveIV(salt, password []byte, iterations int) []byte
31}
32
33type shaWithTripleDESCBC struct{}
34
35func (shaWithTripleDESCBC) create(key []byte) (cipher.Block, error) {
36 return des.NewTripleDESCipher(key)
37}
38
39func (shaWithTripleDESCBC) deriveKey(salt, password []byte, iterations int) []byte {
40 return pbkdf(sha1Sum, 20, 64, salt, password, iterations, 1, 24)
41}
42
43func (shaWithTripleDESCBC) deriveIV(salt, password []byte, iterations int) []byte {
44 return pbkdf(sha1Sum, 20, 64, salt, password, iterations, 2, 8)
45}
46
47type shaWith40BitRC2CBC struct{}
48
49func (shaWith40BitRC2CBC) create(key []byte) (cipher.Block, error) {
50 return rc2.New(key, len(key)*8)
51}
52
53func (shaWith40BitRC2CBC) deriveKey(salt, password []byte, iterations int) []byte {
54 return pbkdf(sha1Sum, 20, 64, salt, password, iterations, 1, 5)
55}
56
57func (shaWith40BitRC2CBC) deriveIV(salt, password []byte, iterations int) []byte {
58 return pbkdf(sha1Sum, 20, 64, salt, password, iterations, 2, 8)
59}
60
61type pbeParams struct {
62 Salt []byte
63 Iterations int
64}
65
66func pbDecrypterFor(algorithm pkix.AlgorithmIdentifier, password []byte) (cipher.BlockMode, int, error) {
67 var cipherType pbeCipher
68
69 switch {
70 case algorithm.Algorithm.Equal(oidPBEWithSHAAnd3KeyTripleDESCBC):
71 cipherType = shaWithTripleDESCBC{}
72 case algorithm.Algorithm.Equal(oidPBEWithSHAAnd40BitRC2CBC):
73 cipherType = shaWith40BitRC2CBC{}
74 default:
75 return nil, 0, NotImplementedError("algorithm " + algorithm.Algorithm.String() + " is not supported")
76 }
77
78 var params pbeParams
79 if err := unmarshal(algorithm.Parameters.FullBytes, ¶ms); err != nil {
80 return nil, 0, err
81 }
82
83 key := cipherType.deriveKey(params.Salt, password, params.Iterations)
84 iv := cipherType.deriveIV(params.Salt, password, params.Iterations)
85
86 block, err := cipherType.create(key)
87 if err != nil {
88 return nil, 0, err
89 }
90
91 return cipher.NewCBCDecrypter(block, iv), block.BlockSize(), nil
92}
93
94func pbDecrypt(info decryptable, password []byte) (decrypted []byte, err error) {
95 cbc, blockSize, err := pbDecrypterFor(info.Algorithm(), password)
96 if err != nil {
97 return nil, err
98 }
99
100 encrypted := info.Data()
101 if len(encrypted) == 0 {
102 return nil, errors.New("pkcs12: empty encrypted data")
103 }
104 if len(encrypted)%blockSize != 0 {
105 return nil, errors.New("pkcs12: input is not a multiple of the block size")
106 }
107 decrypted = make([]byte, len(encrypted))
108 cbc.CryptBlocks(decrypted, encrypted)
109
110 psLen := int(decrypted[len(decrypted)-1])
111 if psLen == 0 || psLen > blockSize {
112 return nil, ErrDecryption
113 }
114
115 if len(decrypted) < psLen {
116 return nil, ErrDecryption
117 }
118 ps := decrypted[len(decrypted)-psLen:]
119 decrypted = decrypted[:len(decrypted)-psLen]
120 if !bytes.Equal(ps, bytes.Repeat([]byte{byte(psLen)}, psLen)) {
121 return nil, ErrDecryption
122 }
123
124 return
125}
126
127// decryptable abstracts an object that contains ciphertext.
128type decryptable interface {
129 Algorithm() pkix.AlgorithmIdentifier
130 Data() []byte
131}