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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
package fusefrontend_reverse
import (
"bytes"
"io"
"os"
"syscall"
// In newer Go versions, this has moved to just "sync/syncmap".
"golang.org/x/sync/syncmap"
"github.com/hanwen/go-fuse/fuse"
"github.com/hanwen/go-fuse/fuse/nodefs"
"github.com/rfjakob/gocryptfs/internal/contentenc"
"github.com/rfjakob/gocryptfs/internal/pathiv"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
type reverseFile struct {
// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
nodefs.File
// Backing FD
fd *os.File
// File header (contains the IV)
header contentenc.FileHeader
// IV for block 0
block0IV []byte
// Content encryption helper
contentEnc *contentenc.ContentEnc
}
var inodeTable syncmap.Map
// newFile decrypts and opens the path "relPath" and returns a reverseFile
// object. The backing file descriptor is always read-only.
func (rfs *ReverseFS) newFile(relPath string) (*reverseFile, fuse.Status) {
if rfs.isExcluded(relPath) {
// Excluded paths should have been filtered out beforehand. Better safe
// than sorry.
tlog.Warn.Printf("BUG: newFile: received excluded path %q. This should not happen.", relPath)
return nil, fuse.ENOENT
}
pRelPath, err := rfs.decryptPath(relPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
fd, err := syscallcompat.OpenNofollow(rfs.args.Cipherdir, pRelPath, syscall.O_RDONLY, 0)
if err != nil {
return nil, fuse.ToStatus(err)
}
var st syscall.Stat_t
err = syscall.Fstat(fd, &st)
if err != nil {
tlog.Warn.Printf("newFile: Fstat error: %v", err)
syscall.Close(fd)
return nil, fuse.ToStatus(err)
}
// Reject access if the file descriptor does not refer to a regular file.
var a fuse.Attr
a.FromStat(&st)
if !a.IsRegular() {
tlog.Warn.Printf("ino%d: newFile: not a regular file", st.Ino)
syscall.Close(fd)
return nil, fuse.ToStatus(syscall.EACCES)
}
// See if we have that inode number already in the table
// (even if Nlink has dropped to 1)
var derivedIVs pathiv.FileIVs
v, found := inodeTable.Load(st.Ino)
if found {
tlog.Debug.Printf("ino%d: newFile: found in the inode table", st.Ino)
derivedIVs = v.(pathiv.FileIVs)
} else {
derivedIVs = pathiv.DeriveFile(relPath)
// Nlink > 1 means there is more than one path to this file.
// Store the derived values so we always return the same data,
// regardless of the path that is used to access the file.
// This means that the first path wins.
if st.Nlink > 1 {
v, found = inodeTable.LoadOrStore(st.Ino, derivedIVs)
if found {
// Another thread has stored a different value before we could.
derivedIVs = v.(pathiv.FileIVs)
} else {
tlog.Debug.Printf("ino%d: newFile: Nlink=%d, stored in the inode table", st.Ino, st.Nlink)
}
}
}
header := contentenc.FileHeader{
Version: contentenc.CurrentVersion,
ID: derivedIVs.ID,
}
return &reverseFile{
File: nodefs.NewDefaultFile(),
fd: os.NewFile(uintptr(fd), pRelPath),
header: header,
block0IV: derivedIVs.Block0IV,
contentEnc: rfs.contentEnc,
}, fuse.OK
}
// GetAttr - FUSE call
// Triggered by fstat() from userspace
func (rf *reverseFile) GetAttr(*fuse.Attr) fuse.Status {
tlog.Debug.Printf("reverseFile.GetAttr fd=%d\n", rf.fd.Fd())
// The kernel should fall back to stat()
return fuse.ENOSYS
}
// encryptBlocks - encrypt "plaintext" into a number of ciphertext blocks.
// "plaintext" must already be block-aligned.
func (rf *reverseFile) encryptBlocks(plaintext []byte, firstBlockNo uint64, fileID []byte, block0IV []byte) []byte {
inBuf := bytes.NewBuffer(plaintext)
var outBuf bytes.Buffer
bs := int(rf.contentEnc.PlainBS())
for blockNo := firstBlockNo; inBuf.Len() > 0; blockNo++ {
inBlock := inBuf.Next(bs)
iv := pathiv.BlockIV(block0IV, blockNo)
outBlock := rf.contentEnc.EncryptBlockNonce(inBlock, blockNo, fileID, iv)
outBuf.Write(outBlock)
}
return outBuf.Bytes()
}
// readBackingFile: read from the backing plaintext file, encrypt it, return the
// ciphertext.
// "off" ... ciphertext offset (must be >= HEADER_LEN)
// "length" ... ciphertext length
func (rf *reverseFile) readBackingFile(off uint64, length uint64) (out []byte, err error) {
blocks := rf.contentEnc.ExplodeCipherRange(off, length)
// Read the backing plaintext in one go
alignedOffset, alignedLength := contentenc.JointPlaintextRange(blocks)
plaintext := make([]byte, int(alignedLength))
n, err := rf.fd.ReadAt(plaintext, int64(alignedOffset))
if err != nil && err != io.EOF {
tlog.Warn.Printf("readBackingFile: ReadAt: %s", err.Error())
return nil, err
}
// Truncate buffer down to actually read bytes
plaintext = plaintext[0:n]
// Encrypt blocks
ciphertext := rf.encryptBlocks(plaintext, blocks[0].BlockNo, rf.header.ID, rf.block0IV)
// Crop down to the relevant part
lenHave := len(ciphertext)
skip := blocks[0].Skip
endWant := int(skip + length)
if lenHave > endWant {
out = ciphertext[skip:endWant]
} else if lenHave > int(skip) {
out = ciphertext[skip:lenHave]
} // else: out stays empty, file was smaller than the requested offset
return out, nil
}
// Read - FUSE call
func (rf *reverseFile) Read(buf []byte, ioff int64) (resultData fuse.ReadResult, status fuse.Status) {
length := uint64(len(buf))
off := uint64(ioff)
var out bytes.Buffer
var header []byte
// Synthesize file header
if off < contentenc.HeaderLen {
header = rf.header.Pack()
// Truncate to requested part
end := int(off) + len(buf)
if end > len(header) {
end = len(header)
}
header = header[off:end]
// Write into output buffer and adjust offsets
out.Write(header)
hLen := uint64(len(header))
off += hLen
length -= hLen
}
// Read actual file data
if length > 0 {
fileData, err := rf.readBackingFile(off, length)
if err != nil {
return nil, fuse.ToStatus(err)
}
if len(fileData) == 0 {
// If we could not read any actual data, we also don't want to
// return the file header. An empty file stays empty in encrypted
// form.
return nil, fuse.OK
}
out.Write(fileData)
}
return fuse.ReadResultData(out.Bytes()), fuse.OK
}
// Release - FUSE call, close file
func (rf *reverseFile) Release() {
rf.fd.Close()
}
|
