aboutsummaryrefslogtreecommitdiff
path: root/internal/nametransform/longnames.go
blob: da18ebbec15dcfd91da7960782e4a422c0c82e08 (plain)
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
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]"
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)
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]").
func IsLongContent(cName string) bool {
	return NameType(cName) == LongNameContent
}

// ReadLongName - read "$path.name"
func ReadLongName(path string) (string, error) {
	path += LongNameSuffix
	fd, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer fd.Close()
	// 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 := fd.ReadAt(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".
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
// converted internally.
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
}