forked from saracen/go7z
/
aes.go
132 lines (109 loc) · 2.38 KB
/
aes.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
package filters
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/sha256"
"encoding/binary"
"hash"
"io"
"strings"
"unicode/utf16"
)
var km keyManager
func init() {
km.cache = make(map[string][]byte)
km.hasher = sha256.New()
}
// AESDecrypter is an AES-256 decryptor.
type AESDecrypter struct {
r io.Reader
rbuf bytes.Buffer
cbc cipher.BlockMode
buf [aes.BlockSize]byte
}
type keyManager struct {
hasher hash.Hash
cache map[string][]byte
}
func (km *keyManager) Key(power int, salt []byte, password string) []byte {
var cacheKey strings.Builder
cacheKey.WriteString(password)
cacheKey.Write(salt)
cacheKey.WriteByte(byte(power))
key, ok := km.cache[cacheKey.String()]
if ok {
return key
}
b := bytes.NewBuffer(nil)
for _, p := range utf16.Encode([]rune(password)) {
binary.Write(b, binary.LittleEndian, p)
}
if power == 0x3f {
key = km.stretch(salt, b.Bytes())
} else {
key = km.sha256Stretch(power, salt, b.Bytes())
}
km.cache[cacheKey.String()] = key
return key
}
func (km *keyManager) stretch(salt, password []byte) []byte {
var key [aes.BlockSize]byte
var pos int
for pos = 0; pos < len(salt); pos++ {
key[pos] = salt[pos]
}
for i := 0; i < len(password) && pos < len(key); i++ {
key[pos] = password[i]
pos++
}
for ; pos < len(key); pos++ {
key[pos] = 0
}
return key[:]
}
func (km *keyManager) sha256Stretch(power int, salt, password []byte) []byte {
var temp [8]byte
for round := 0; round < 1<<uint(power); round++ {
km.hasher.Write(salt)
km.hasher.Write(password)
km.hasher.Write(temp[:])
for i := 0; i < 8; i++ {
temp[i]++
if temp[i] != 0 {
break
}
}
}
defer km.hasher.Reset()
return km.hasher.Sum(nil)
}
// NewAESDecrypter returns a new AES-256 decryptor.
func NewAESDecrypter(r io.Reader, power int, salt, iv []byte, password string) (*AESDecrypter, error) {
key := km.Key(power, salt, password)
cb, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
var aesiv [aes.BlockSize]byte
copy(aesiv[:], iv)
return &AESDecrypter{
r: r,
cbc: cipher.NewCBCDecrypter(cb, aesiv[:]),
}, nil
}
func (d *AESDecrypter) Read(p []byte) (int, error) {
for d.rbuf.Len() < len(p) {
_, err := d.r.Read(d.buf[:])
if err != nil {
return 0, err
}
d.cbc.CryptBlocks(d.buf[:], d.buf[:])
_, err = d.rbuf.Write(d.buf[:])
if err != nil {
return 0, err
}
}
n, err := d.rbuf.Read(p)
return n, err
}