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
|
// Package nametransform encrypts and decrypts filenames.
package nametransform
import (
"crypto/aes"
"encoding/base64"
"path/filepath"
"syscall"
"github.com/rfjakob/eme"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// Like ext4, we allow at most 255 bytes for a file name.
NameMax = 255
//BadNameFlag is appended to filenames in plain mode if a ciphername is inavlid but is shown
BadNameFlag = " GOCRYPTFS_BAD_NAME"
)
// NameTransformer is an interface used to transform filenames.
type NameTransformer interface {
DecryptName(cipherName string, iv []byte) (string, error)
EncryptName(plainName string, iv []byte) (string, error)
EncryptAndHashName(name string, iv []byte) (string, error)
EncryptAndHashBadName(name string, iv []byte, dirfd int) (string, error)
// HashLongName - take the hash of a long string "name" and return
// "gocryptfs.longname.[sha256]"
//
// This function does not do any I/O.
HashLongName(name string) string
HaveBadnamePatterns() bool
WriteLongNameAt(dirfd int, hashName string, plainName string) error
B64EncodeToString(src []byte) string
B64DecodeString(s string) ([]byte, error)
}
// NameTransform is used to transform filenames.
type NameTransform struct {
emeCipher *eme.EMECipher
longNames bool
// B64 = either base64.URLEncoding or base64.RawURLEncoding, depending
// on the Raw64 feature flag
B64 *base64.Encoding
// Patterns to bypass decryption
BadnamePatterns []string
}
// New returns a new NameTransform instance.
func New(e *eme.EMECipher, longNames bool, raw64 bool) *NameTransform {
b64 := base64.URLEncoding
if raw64 {
b64 = base64.RawURLEncoding
}
return &NameTransform{
emeCipher: e,
longNames: longNames,
B64: b64,
}
}
// DecryptName calls decryptName to try and decrypt a base64-encoded encrypted
// filename "cipherName", and failing that checks if it can be bypassed
func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error) {
res, err := n.decryptName(cipherName, iv)
if err != nil {
for _, pattern := range n.BadnamePatterns {
match, err := filepath.Match(pattern, cipherName)
if err == nil && match { // Pattern should have been validated already
// Find longest decryptable substring
// At least 16 bytes due to AES --> at least 22 characters in base64
nameMin := n.B64.EncodedLen(aes.BlockSize)
for charpos := len(cipherName) - 1; charpos >= nameMin; charpos-- {
res, err = n.decryptName(cipherName[:charpos], iv)
if err == nil {
return res + cipherName[charpos:] + BadNameFlag, nil
}
}
return cipherName + BadNameFlag, nil
}
}
}
return res, err
}
// decryptName decrypts a base64-encoded encrypted filename "cipherName" using the
// initialization vector "iv".
func (n *NameTransform) decryptName(cipherName string, iv []byte) (string, error) {
bin, err := n.B64.DecodeString(cipherName)
if err != nil {
return "", err
}
if len(bin) == 0 {
tlog.Warn.Printf("DecryptName: empty input")
return "", syscall.EBADMSG
}
if len(bin)%aes.BlockSize != 0 {
tlog.Debug.Printf("DecryptName %q: decoded length %d is not a multiple of 16", cipherName, len(bin))
return "", syscall.EBADMSG
}
bin = n.emeCipher.Decrypt(iv, bin)
bin, err = unPad16(bin)
if err != nil {
tlog.Warn.Printf("DecryptName %q: unPad16 error: %v", cipherName, err)
return "", syscall.EBADMSG
}
plain := string(bin)
if err := IsValidName(plain); err != nil {
tlog.Warn.Printf("DecryptName %q: invalid name after decryption: %v", cipherName, err)
return "", syscall.EBADMSG
}
return plain, err
}
// EncryptName encrypts "plainName", returns a base64-encoded "cipherName64",
// encrypted using EME (https://github.com/rfjakob/eme).
//
// This function is exported because in some cases, fusefrontend needs access
// to the full (not hashed) name if longname is used.
func (n *NameTransform) EncryptName(plainName string, iv []byte) (cipherName64 string, err error) {
if err := IsValidName(plainName); err != nil {
tlog.Warn.Printf("EncryptName %q: invalid plainName: %v", plainName, err)
return "", syscall.EBADMSG
}
bin := []byte(plainName)
bin = pad16(bin)
bin = n.emeCipher.Encrypt(iv, bin)
cipherName64 = n.B64.EncodeToString(bin)
return cipherName64, nil
}
// B64EncodeToString returns a Base64-encoded string
func (n *NameTransform) B64EncodeToString(src []byte) string {
return n.B64.EncodeToString(src)
}
// B64DecodeString decodes a Base64-encoded string
func (n *NameTransform) B64DecodeString(s string) ([]byte, error) {
return n.B64.DecodeString(s)
}
// HaveBadnamePatterns returns true if BadName patterns were provided
func (n *NameTransform) HaveBadnamePatterns() bool {
return len(n.BadnamePatterns) > 0
}
|
