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
|
package nametransform
import (
"crypto/aes"
"path/filepath"
"strings"
"syscall"
"golang.org/x/sys/unix"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
)
const (
// BadNameFlag is appended to filenames in plaintext view if a corrupt
// ciphername is shown due to a matching `-badname` pattern
BadNameFlag = " GOCRYPTFS_BAD_NAME"
)
// EncryptAndHashBadName tries to find the "name" substring, which (encrypted and hashed)
// leads to an unique existing file
// Returns ENOENT if cipher file does not exist or is not unique
func (be *NameTransform) EncryptAndHashBadName(name string, iv []byte, dirfd int) (cName string, err error) {
var st unix.Stat_t
var filesFound int
lastFoundName, err := be.EncryptAndHashName(name, iv)
if !strings.HasSuffix(name, BadNameFlag) || err != nil {
//Default mode: same behaviour on error or no BadNameFlag on "name"
return lastFoundName, err
}
//Default mode: Check if File extists without modifications
err = syscallcompat.Fstatat(dirfd, lastFoundName, &st, unix.AT_SYMLINK_NOFOLLOW)
if err == nil {
//file found, return result
return lastFoundName, nil
}
//BadName Mode: check if the name was tranformed without change (badname suffix and undecryptable cipher name)
err = syscallcompat.Fstatat(dirfd, name[:len(name)-len(BadNameFlag)], &st, unix.AT_SYMLINK_NOFOLLOW)
if err == nil {
filesFound++
lastFoundName = name[:len(name)-len(BadNameFlag)]
}
// search for the longest badname pattern match
for charpos := len(name) - len(BadNameFlag); charpos > 0; charpos-- {
//only use original cipher name and append assumed suffix (without badname flag)
cNamePart, err := be.EncryptName(name[:charpos], iv)
if err != nil {
//expand suffix on error
continue
}
if be.longNames && len(cName) > NameMax {
cNamePart = be.HashLongName(cName)
}
cNameBadReverse := cNamePart + name[charpos:len(name)-len(BadNameFlag)]
err = syscallcompat.Fstatat(dirfd, cNameBadReverse, &st, unix.AT_SYMLINK_NOFOLLOW)
if err == nil {
filesFound++
lastFoundName = cNameBadReverse
}
}
if filesFound == 1 {
return lastFoundName, nil
}
// more than 1 possible file found, ignore
return "", syscall.ENOENT
}
func (n *NameTransform) decryptBadname(cipherName string, iv []byte) (string, error) {
for _, pattern := range n.badnamePatterns {
match, err := filepath.Match(pattern, cipherName)
// Pattern should have been validated already
if err == nil && match {
// 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 "", syscall.EBADMSG
}
// HaveBadnamePatterns returns true if `-badname` patterns were provided
func (n *NameTransform) HaveBadnamePatterns() bool {
return len(n.badnamePatterns) > 0
}
|
