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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
package cryptfs
// Filename encryption / decryption function
import (
"crypto/cipher"
"crypto/aes"
"fmt"
"strings"
"encoding/base64"
"errors"
)
const (
ENCRYPT = true
DECRYPT = false
)
// DecryptName - decrypt filename
func (be *CryptFS) decryptName(cipherName string) (string, error) {
bin, err := base64.URLEncoding.DecodeString(cipherName)
if err != nil {
return "", err
}
if len(bin) % aes.BlockSize != 0 {
return "", errors.New(fmt.Sprintf("Name len=%d is not a multiple of 16", len(bin)))
}
iv := make([]byte, aes.BlockSize) // TODO ?
cbc := cipher.NewCBCDecrypter(be.blockCipher, iv)
cbc.CryptBlocks(bin, bin)
bin, err = be.unPad16(bin)
if err != nil {
return "", err
}
plain := string(bin)
return plain, err
}
// EncryptName - encrypt filename
func (be *CryptFS) encryptName(plainName string) string {
bin := []byte(plainName)
bin = be.pad16(bin)
iv := make([]byte, 16) // TODO ?
cbc := cipher.NewCBCEncrypter(be.blockCipher, iv)
cbc.CryptBlocks(bin, bin)
cipherName64 := base64.URLEncoding.EncodeToString(bin)
return cipherName64
}
// TranslatePath - encrypt or decrypt path. Just splits the string on "/"
// and hands the parts to EncryptName() / DecryptName()
func (be *CryptFS) translatePath(path string, op bool) (string, error) {
var err error
// Empty string means root directory
if path == "" {
return path, err
}
// Run operation on each path component
var translatedParts []string
parts := strings.Split(path, "/")
for _, part := range parts {
var newPart string
if op == ENCRYPT {
newPart = be.encryptName(part)
} else {
newPart, err = be.decryptName(part)
if err != nil {
return "", err
}
}
translatedParts = append(translatedParts, newPart)
}
return strings.Join(translatedParts, "/"), err
}
// EncryptPath - encrypt filename or path. Just hands it to TranslatePath().
func (be *CryptFS) EncryptPath(path string) string {
newPath, _ := be.translatePath(path, ENCRYPT)
return newPath
}
// DecryptPath - decrypt filename or path. Just hands it to TranslatePath().
func (be *CryptFS) DecryptPath(path string) (string, error) {
return be.translatePath(path, DECRYPT)
}
// pad16 - pad filename to 16 byte blocks using standard PKCS#7 padding
// https://tools.ietf.org/html/rfc5652#section-6.3
func (be *CryptFS) pad16(orig []byte) (padded []byte) {
oldLen := len(orig)
if oldLen == 0 {
panic("Padding zero-length string makes no sense")
}
padLen := aes.BlockSize - oldLen % aes.BlockSize
if padLen == 0 {
padLen = aes.BlockSize
}
newLen := oldLen + padLen
padded = make([]byte, newLen)
copy(padded, orig)
padByte := byte(padLen)
for i := oldLen; i < newLen; i++ {
padded[i] = padByte
}
return padded
}
// unPad16 - remove padding
func (be *CryptFS) unPad16(orig []byte) ([]byte, error) {
oldLen := len(orig)
if oldLen % aes.BlockSize != 0 {
return nil, errors.New("Unaligned size")
}
// The last byte is always a padding byte
padByte := orig[oldLen -1]
// The padding byte's value is the padding length
padLen := int(padByte)
// Padding must be at least 1 byte
if padLen <= 0 {
return nil, errors.New("Padding cannot be zero-length")
}
// Larger paddings make no sense
if padLen > aes.BlockSize {
return nil, errors.New("Padding cannot be larger than 16")
}
// All padding bytes must be identical
for i := oldLen - padLen; i < oldLen; i++ {
if orig[i] != padByte {
return nil, errors.New(fmt.Sprintf("Padding byte at i=%d is invalid", i))
}
}
newLen := oldLen - padLen
// Padding an empty string makes no sense
if newLen == 0 {
return nil, errors.New("Unpadded length is zero")
}
return orig[0:newLen], nil
}
|
