-
Notifications
You must be signed in to change notification settings - Fork 3
/
symmetric.go
131 lines (105 loc) · 2.82 KB
/
symmetric.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
//Original source: https://github.com/gokyle/marchat
package signature
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"fmt"
"io"
)
const KeySize = 16
var (
ErrPadding = fmt.Errorf("invalid padding")
ErrRandomFailure = fmt.Errorf("failed to read enough random data")
ErrInvalidIV = fmt.Errorf("invalid IV")
)
func Decrypt(key string, encryptedMessage []byte) ([]byte, error) {
cypher, err := aes.NewCipher(getEncryptionKey(key))
if err != nil {
return nil, err
}
clonedEncryptedMessage := make([]byte, len(encryptedMessage))
copy(clonedEncryptedMessage, encryptedMessage)
if len(clonedEncryptedMessage) < aes.BlockSize {
return nil, ErrInvalidIV
}
iv := clonedEncryptedMessage[:aes.BlockSize]
message := clonedEncryptedMessage[aes.BlockSize:]
cbc := cipher.NewCBCDecrypter(cypher, iv)
cbc.CryptBlocks(message, message)
return unpadBuffer(message)
}
func DigestBytes(message []byte) []byte {
hasher := sha256.New()
hasher.Write(message)
hashedKey := hasher.Sum(nil)
return hashedKey
}
func Encrypt(key string, message []byte) ([]byte, error) {
cypher, err := aes.NewCipher(getEncryptionKey(key))
if err != nil {
return nil, err
}
iv, err := generateIV()
if err != nil {
return nil, err
}
paddedMessage, err := padBuffer(message)
if err != nil {
return nil, err
}
cbc := cipher.NewCBCEncrypter(cypher, iv)
cbc.CryptBlocks(paddedMessage, paddedMessage)
encryptedMessage := append(iv, paddedMessage...)
return encryptedMessage, nil
}
func getEncryptionKey(key string) []byte {
hasher := sha256.New()
io.WriteString(hasher, key)
hashedKey := hasher.Sum(nil)
return []byte(hashedKey)[:16]
}
func generateIV() ([]byte, error) {
return random(aes.BlockSize)
}
func random(size int) ([]byte, error) {
randomBytes := make([]byte, size)
n, err := rand.Read(randomBytes)
if err != nil {
return []byte{}, err
} else if size != n {
err = ErrRandomFailure
}
return randomBytes, err
}
func padBuffer(message []byte) ([]byte, error) {
messageLen := len(message)
paddedMessage := make([]byte, messageLen)
copy(paddedMessage, message)
if len(paddedMessage) != messageLen {
return paddedMessage, ErrPadding
}
bytesToPad := aes.BlockSize - messageLen%aes.BlockSize
paddedMessage = append(paddedMessage, 0x80)
for i := 1; i < bytesToPad; i++ {
paddedMessage = append(paddedMessage, 0x0)
}
return paddedMessage, nil
}
func unpadBuffer(paddedMessage []byte) ([]byte, error) {
message := paddedMessage
var paddedMessageLen int
origLen := len(message)
for paddedMessageLen = origLen - 1; paddedMessageLen >= 0; paddedMessageLen-- {
if message[paddedMessageLen] == 0x80 {
break
}
if message[paddedMessageLen] != 0x0 || (origLen-paddedMessageLen) > aes.BlockSize {
err := ErrPadding
return nil, err
}
}
message = message[:paddedMessageLen]
return message, nil
}