aboutsummaryrefslogtreecommitdiff
path: root/internal/fusefrontend_reverse/rfs.go
blob: 4b04b865a0ad14969af82871f690ce3d1868d7bc (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
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
package fusefrontend_reverse

import (
	"fmt"
	"os"
	"path/filepath"
	"syscall"

	"github.com/hanwen/go-fuse/fuse"
	"github.com/hanwen/go-fuse/fuse/nodefs"
	"github.com/hanwen/go-fuse/fuse/pathfs"

	"github.com/rfjakob/gocryptfs/internal/configfile"
	"github.com/rfjakob/gocryptfs/internal/contentenc"
	"github.com/rfjakob/gocryptfs/internal/cryptocore"
	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
	"github.com/rfjakob/gocryptfs/internal/nametransform"
)

const (
	DirIVMode = syscall.S_IFREG | 0400
)

type reverseFS struct {
	// Embed pathfs.defaultFileSystem for a ENOSYS implementation of all methods
	pathfs.FileSystem
	// pathfs.loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
	loopbackfs pathfs.FileSystem
	// Stores configuration arguments
	args fusefrontend.Args
	// Filename encryption helper
	nameTransform *nametransform.NameTransform
	// Content encryption helper
	contentEnc *contentenc.ContentEnc
}

// Encrypted FUSE overlay filesystem
func NewFS(args fusefrontend.Args) *reverseFS {
	cryptoCore := cryptocore.New(args.Masterkey, args.CryptoBackend, contentenc.IVBitLen)
	contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS)
	nameTransform := nametransform.New(cryptoCore, args.LongNames)

	return &reverseFS{
		// pathfs.defaultFileSystem returns ENOSYS for all operations
		FileSystem:    pathfs.NewDefaultFileSystem(),
		loopbackfs:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
		args:          args,
		nameTransform: nameTransform,
		contentEnc:    contentEnc,
	}
}

// relDir is identical to filepath.Dir excepts that it returns "" when
// filepath.Dir would return ".".
// In the FUSE API, the root directory is called "", and we actually want that.
func relDir(path string) string {
	dir := filepath.Dir(path)
	if dir == "." {
		return ""
	}
	return dir
}

// dirIVAttr handles GetAttr requests for the virtual gocryptfs.diriv files.
func (rfs *reverseFS) dirIVAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
	cDir := relDir(relPath)
	dir, err := rfs.decryptPath(cDir)
	if err != nil {
		fmt.Printf("decrypt err %q\n", cDir)
		return nil, fuse.ToStatus(err)
	}
	// Does the parent dir exist?
	a, status := rfs.loopbackfs.GetAttr(dir, context)
	if !status.Ok() {
		fmt.Printf("missing parent\n")
		return nil, status
	}
	// Is it a dir at all?
	if !a.IsDir() {
		fmt.Printf("not isdir\n")
		return nil, fuse.ENOTDIR
	}
	// Does the user have execute permissions?
	if a.Mode&syscall.S_IXUSR == 0 {
		fmt.Printf("not exec")
		return nil, fuse.EPERM
	}
	// All good. Let's fake the file.
	// We use the inode number of the parent dir (can this cause problems?).
	a.Mode = DirIVMode
	a.Size = nametransform.DirIVLen
	a.Nlink = 1

	return a, fuse.OK
}

// isDirIV determines if the path points to a gocryptfs.diriv file
func isDirIV(relPath string) bool {
	return filepath.Base(relPath) == nametransform.DirIVFilename
}

// GetAttr - FUSE call
func (rfs *reverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
	if relPath == configfile.ConfDefaultName {
		return rfs.loopbackfs.GetAttr(configfile.ConfReverseName, context)
	}
	if isDirIV(relPath) {
		return rfs.dirIVAttr(relPath, context)
	}
	if rfs.isFiltered(relPath) {
		return nil, fuse.EPERM
	}
	relPath, err := rfs.decryptPath(relPath)
	if err != nil {
		return nil, fuse.ToStatus(err)
	}
	a, status := rfs.loopbackfs.GetAttr(relPath, context)
	if !status.Ok() {
		return nil, status
	}
	// Calculate encrypted file size
	if a.IsRegular() {
		a.Size = rfs.contentEnc.PlainSizeToCipherSize(a.Size)
	}
	return a, fuse.OK
}

// Access - FUSE call
func (rfs *reverseFS) Access(relPath string, mode uint32, context *fuse.Context) fuse.Status {
	if isDirIV(relPath) {
		return fuse.OK
	}
	if rfs.isFiltered(relPath) {
		return fuse.EPERM
	}
	absPath, err := rfs.abs(rfs.decryptPath(relPath))
	if err != nil {
		return fuse.ToStatus(err)
	}
	return fuse.ToStatus(syscall.Access(absPath, mode))
}

// Open - FUSE call
func (rfs *reverseFS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
	if relPath == configfile.ConfDefaultName {
		// gocryptfs.conf maps to .gocryptfs.reverse.conf in the plaintext directory
		return rfs.loopbackfs.Open(configfile.ConfReverseName, flags, context)
	}
	if isDirIV(relPath) {
		return NewDirIVFile(relDir(relPath))
	}
	if rfs.isFiltered(relPath) {
		return nil, fuse.EPERM
	}
	absPath, err := rfs.abs(rfs.decryptPath(relPath))
	if err != nil {
		return nil, fuse.ToStatus(err)
	}
	f, err := os.OpenFile(absPath, int(flags), 0666)
	if err != nil {
		return nil, fuse.ToStatus(err)
	}
	return NewFile(f, rfs.contentEnc)
}

// OpenDir - FUSE readdir call
func (rfs *reverseFS) OpenDir(cipherPath string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
	relPath, err := rfs.decryptPath(cipherPath)
	if err != nil {
		return nil, fuse.ToStatus(err)
	}
	// Read plaintext dir
	entries, status := rfs.loopbackfs.OpenDir(relPath, context)
	if entries == nil {
		return nil, status
	}
	// Encrypt names
	dirIV := deriveDirIV(cipherPath)
	for i := range entries {
		// ".gocryptfs.reverse.conf" in the root directory is mapped to "gocryptfs.conf"
		if cipherPath == "" && entries[i].Name == configfile.ConfReverseName {
			entries[i].Name = configfile.ConfDefaultName
		} else {
			entries[i].Name = rfs.nameTransform.EncryptName(entries[i].Name, dirIV)
		}
	}
	// Add virtual gocryptfs.diriv
	entries = append(entries, fuse.DirEntry{syscall.S_IFREG | 0400, nametransform.DirIVFilename})

	return entries, fuse.OK
}