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
151
152
153
|
package nametransform
import (
"crypto/sha256"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// LongNameSuffix is the suffix used for files with long names.
// Files with long names are stored in two files:
// gocryptfs.longname.[sha256] <--- File content, prefix = gocryptfs.longname.
// gocryptfs.longname.[sha256].name <--- File name, suffix = .name
LongNameSuffix = ".name"
longNamePrefix = "gocryptfs.longname."
)
// HashLongName - take the hash of a long string "name" and return
// "gocryptfs.longname.[sha256]"
//
// This function does not do any I/O.
func (n *NameTransform) HashLongName(name string) string {
hashBin := sha256.Sum256([]byte(name))
hashBase64 := n.B64.EncodeToString(hashBin[:])
return longNamePrefix + hashBase64
}
// Values returned by IsLongName
const (
// LongNameContent is the file that stores the file content.
// Example: gocryptfs.longname.URrM8kgxTKYMgCk4hKk7RO9Lcfr30XQof4L_5bD9Iro=
LongNameContent = iota
// LongNameFilename is the file that stores the full encrypted filename.
// Example: gocryptfs.longname.URrM8kgxTKYMgCk4hKk7RO9Lcfr30XQof4L_5bD9Iro=.name
LongNameFilename = iota
// LongNameNone is used when the file does not have a long name.
// Example: i1bpTaVLZq7sRNA9mL_2Ig==
LongNameNone = iota
)
// NameType - detect if cName is
// gocryptfs.longname.[sha256] ........ LongNameContent (content of a long name file)
// gocryptfs.longname.[sha256].name .... LongNameFilename (full file name of a long name file)
// else ................................ LongNameNone (normal file)
//
// This function does not do any I/O.
func NameType(cName string) int {
if !strings.HasPrefix(cName, longNamePrefix) {
return LongNameNone
}
if strings.HasSuffix(cName, LongNameSuffix) {
return LongNameFilename
}
return LongNameContent
}
// IsLongContent returns true if "cName" is the content store of a long name
// file (looks like "gocryptfs.longname.[sha256]").
//
// This function does not do any I/O.
func IsLongContent(cName string) bool {
return NameType(cName) == LongNameContent
}
// ReadLongName - read cName + ".name" from the directory opened as dirfd.
//
// Symlink-safe through Openat().
func ReadLongNameAt(dirfd int, cName string) (string, error) {
cName += LongNameSuffix
fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_NOFOLLOW, 0)
if err != nil {
return "", err
}
defer syscall.Close(fd)
// 256 (=255 padded to 16) bytes base64-encoded take 344 bytes: "AAAAAAA...AAA=="
lim := 344
// Allocate a bigger buffer so we see whether the file is too big
buf := make([]byte, lim+1)
n, err := syscall.Pread(fd, buf, 0)
if err != nil && err != io.EOF {
return "", err
}
if n == 0 {
return "", fmt.Errorf("ReadLongName: empty file")
}
if n > lim {
return "", fmt.Errorf("ReadLongName: size=%d > limit=%d", n, lim)
}
return string(buf[0:n]), nil
}
// DeleteLongName deletes "hashName.name" in the directory openend at "dirfd".
//
// This function is symlink-safe through the use of Unlinkat().
func DeleteLongName(dirfd int, hashName string) error {
err := syscallcompat.Unlinkat(dirfd, hashName+LongNameSuffix, 0)
if err != nil {
tlog.Warn.Printf("DeleteLongName: %v", err)
}
return err
}
// WriteLongName encrypts plainName and writes it into "hashName.name".
// For the convenience of the caller, plainName may also be a path and will be
// Base()named internally.
//
// This function is symlink-safe through the use of Openat().
func (n *NameTransform) WriteLongName(dirfd int, hashName string, plainName string) (err error) {
plainName = filepath.Base(plainName)
// Encrypt the basename
dirIV, err := ReadDirIVAt(dirfd)
if err != nil {
return err
}
cName := n.EncryptName(plainName, dirIV)
// Write the encrypted name into hashName.name
fdRaw, err := syscallcompat.Openat(dirfd, hashName+LongNameSuffix,
syscall.O_WRONLY|syscall.O_CREAT|syscall.O_EXCL, 0600)
if err != nil {
// Don't warn if the file already exists - this is allowed for renames
// and should be handled by the caller.
if err != syscall.EEXIST {
tlog.Warn.Printf("WriteLongName: Openat: %v", err)
}
return err
}
fd := os.NewFile(uintptr(fdRaw), hashName+LongNameSuffix)
_, err = fd.Write([]byte(cName))
if err != nil {
fd.Close()
tlog.Warn.Printf("WriteLongName: Write: %v", err)
// Delete incomplete longname file
syscallcompat.Unlinkat(dirfd, hashName+LongNameSuffix, 0)
return err
}
err = fd.Close()
if err != nil {
tlog.Warn.Printf("WriteLongName: Close: %v", err)
// Delete incomplete longname file
syscallcompat.Unlinkat(dirfd, hashName+LongNameSuffix, 0)
return err
}
return nil
}
|
