aboutsummaryrefslogtreecommitdiff
path: root/internal/fusefrontend/node.go
blob: 657a3bca340d8497bb98d838dd72383e53fb4485 (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
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
package fusefrontend

import (
	"context"
	"syscall"

	"golang.org/x/sys/unix"

	"github.com/hanwen/go-fuse/v2/fs"
	"github.com/hanwen/go-fuse/v2/fuse"

	"github.com/rfjakob/gocryptfs/internal/nametransform"
	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
	"github.com/rfjakob/gocryptfs/internal/tlog"
)

// Node is a file or directory in the filesystem tree
// in a gocryptfs mount.
type Node struct {
	fs.Inode
}

// Lookup - FUSE call for discovering a file.
func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	// Get device number and inode number into `st`
	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
	if err != nil {
		return nil, fs.ToErrno(err)
	}

	// Create new inode and fill `out`
	ch = n.newChild(ctx, st, out)

	// Translate ciphertext size in `out.Attr.Size` to plaintext size
	n.translateSize(dirfd, cName, &out.Attr)

	return ch, 0
}

// GetAttr - FUSE call for stat()ing a file.
//
// GetAttr is symlink-safe through use of openBackingDir() and Fstatat().
func (n *Node) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) (errno syscall.Errno) {
	// If the kernel gives us a file handle, use it.
	if f != nil {
		return f.(fs.FileGetattrer).Getattr(ctx, out)
	}

	dirfd, cName, errno := n.prepareAtSyscall("")
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
	if err != nil {
		return fs.ToErrno(err)
	}

	// Fix inode number
	rn := n.rootNode()
	rn.inoMap.TranslateStat(st)
	out.Attr.FromStat(st)

	// Translate ciphertext size in `out.Attr.Size` to plaintext size
	n.translateSize(dirfd, cName, &out.Attr)

	if rn.args.ForceOwner != nil {
		out.Owner = *rn.args.ForceOwner
	}
	return 0
}

// Unlink - FUSE call. Delete a file.
//
// Symlink-safe through use of Unlinkat().
func (n *Node) Unlink(ctx context.Context, name string) (errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	// Delete content
	err := syscallcompat.Unlinkat(dirfd, cName, 0)
	if err != nil {
		return fs.ToErrno(err)
	}
	// Delete ".name" file
	if !n.rootNode().args.PlaintextNames && nametransform.IsLongContent(cName) {
		err = nametransform.DeleteLongNameAt(dirfd, cName)
		if err != nil {
			tlog.Warn.Printf("Unlink: could not delete .name file: %v", err)
		}
	}
	return fs.ToErrno(err)
}

// Readlink - FUSE call.
//
// Symlink-safe through openBackingDir() + Readlinkat().
func (n *Node) Readlink(ctx context.Context) (out []byte, errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall("")
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	return n.readlink(dirfd, cName)
}

// Setattr - FUSE call. Called for chmod, truncate, utimens, ...
func (n *Node) Setattr(ctx context.Context, f fs.FileHandle, in *fuse.SetAttrIn, out *fuse.AttrOut) (errno syscall.Errno) {
	// Use the fd if the kernel gave us one
	if f != nil {
		f2 := f.(*File)
		return f2.Setattr(ctx, in, out)
	}

	dirfd, cName, errno := n.prepareAtSyscall("")
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	// chmod(2)
	//
	// gocryptfs.diriv & gocryptfs.longname.[sha256].name files do NOT get chmod'ed
	// or chown'ed with their parent file/dir for simplicity.
	// See nametransform/perms.go for details.
	if mode, ok := in.GetMode(); ok {
		errno = fs.ToErrno(syscallcompat.FchmodatNofollow(dirfd, cName, mode))
		if errno != 0 {
			return errno
		}
	}

	// chown(2)
	uid32, uOk := in.GetUID()
	gid32, gOk := in.GetGID()
	if uOk || gOk {
		uid := -1
		gid := -1

		if uOk {
			uid = int(uid32)
		}
		if gOk {
			gid = int(gid32)
		}
		errno = fs.ToErrno(syscallcompat.Fchownat(dirfd, cName, uid, gid, unix.AT_SYMLINK_NOFOLLOW))
		if errno != 0 {
			return errno
		}
	}

	// utimens(2)
	mtime, mok := in.GetMTime()
	atime, aok := in.GetATime()
	if mok || aok {
		ap := &atime
		mp := &mtime
		if !aok {
			ap = nil
		}
		if !mok {
			mp = nil
		}
		errno = fs.ToErrno(syscallcompat.UtimesNanoAtNofollow(dirfd, cName, ap, mp))
		if errno != 0 {
			return errno
		}
	}

	// For truncate, the user has to have write permissions. That means we can
	// depend on opening a RDWR fd and letting the File handle truncate.
	if sz, ok := in.GetSize(); ok {
		f, _, errno := n.Open(ctx, syscall.O_RDWR)
		if errno != 0 {
			return errno
		}
		f2 := f.(*File)
		defer f2.Release(ctx)
		errno = syscall.Errno(f2.truncate(sz))
		if errno != 0 {
			return errno
		}
		return f2.Getattr(ctx, out)
	}

	return n.Getattr(ctx, nil, out)
}

// StatFs - FUSE call. Returns information about the filesystem.
//
// Symlink-safe because the path is ignored.
func (n *Node) Statfs(ctx context.Context, out *fuse.StatfsOut) syscall.Errno {
	p := n.rootNode().args.Cipherdir
	var st syscall.Statfs_t
	err := syscall.Statfs(p, &st)
	if err != nil {
		return fs.ToErrno(err)
	}
	out.FromStatfsT(&st)
	return 0
}

// Mknod - FUSE call. Create a device file.
//
// Symlink-safe through use of Mknodat().
func (n *Node) Mknod(ctx context.Context, name string, mode, rdev uint32, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	// Make sure context is nil if we don't want to preserve the owner
	rn := n.rootNode()
	if !rn.args.PreserveOwner {
		ctx = nil
	}

	// Create ".name" file to store long file name (except in PlaintextNames mode)
	var err error
	ctx2 := toFuseCtx(ctx)
	if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
		err := rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
		if err != nil {
			errno = fs.ToErrno(err)
			return
		}
		// Create "gocryptfs.longfile." device node
		err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
		if err != nil {
			nametransform.DeleteLongNameAt(dirfd, cName)
		}
	} else {
		// Create regular device node
		err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
	}
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}

	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}
	inode = n.newChild(ctx, st, out)
	return inode, 0
}

// Link - FUSE call. Creates a hard link at "newPath" pointing to file
// "oldPath".
//
// Symlink-safe through use of Linkat().
func (n *Node) Link(ctx context.Context, target fs.InodeEmbedder, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	n2 := toNode(target)
	dirfd2, cName2, errno := n2.prepareAtSyscall("")
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd2)

	// Handle long file name (except in PlaintextNames mode)
	rn := n.rootNode()
	var err error
	if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
		err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
		if err != nil {
			errno = fs.ToErrno(err)
			return
		}
		// Create "gocryptfs.longfile." link
		err = unix.Linkat(dirfd2, cName2, dirfd, cName, 0)
		if err != nil {
			nametransform.DeleteLongNameAt(dirfd, cName)
		}
	} else {
		// Create regular link
		err = unix.Linkat(dirfd2, cName2, dirfd, cName, 0)
	}
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}

	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}
	inode = n.newChild(ctx, st, out)
	return inode, 0
}

// Symlink - FUSE call. Create a symlink.
//
// Symlink-safe through use of Symlinkat.
func (n *Node) Symlink(ctx context.Context, target, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	// Make sure context is nil if we don't want to preserve the owner
	rn := n.rootNode()
	if !rn.args.PreserveOwner {
		ctx = nil
	}

	cTarget := target
	if !rn.args.PlaintextNames {
		// Symlinks are encrypted like file contents (GCM) and base64-encoded
		cTarget = rn.encryptSymlinkTarget(target)
	}
	// Create ".name" file to store long file name (except in PlaintextNames mode)
	var err error
	ctx2 := toFuseCtx(ctx)
	if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
		err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
		if err != nil {
			errno = fs.ToErrno(err)
			return
		}
		// Create "gocryptfs.longfile." symlink
		err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
		if err != nil {
			nametransform.DeleteLongNameAt(dirfd, cName)
		}
	} else {
		// Create symlink
		err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
	}

	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}
	inode = n.newChild(ctx, st, out)
	return inode, 0
}

// xfstests generic/013 now also exercises RENAME_EXCHANGE and RENAME_WHITEOUT,
// uncovering lots of problems with longnames
//
// Reject those flags with syscall.EINVAL.
// If we can handle the flags, this function returns 0.
func rejectRenameFlags(flags uint32) syscall.Errno {
	// Normal rename, we can handle that
	if flags == 0 {
		return 0
	}
	// We also can handle RENAME_NOREPLACE
	if flags == syscallcompat.RENAME_NOREPLACE {
		return 0
	}
	// We cannot handle RENAME_EXCHANGE and RENAME_WHITEOUT yet.
	// Needs extra code for .name files.
	return syscall.EINVAL
}

// Rename - FUSE call.
// This function is called on the PARENT DIRECTORY of `name`.
//
// Symlink-safe through Renameat().
func (n *Node) Rename(ctx context.Context, name string, newParent fs.InodeEmbedder, newName string, flags uint32) (errno syscall.Errno) {
	if errno = rejectRenameFlags(flags); errno != 0 {
		return errno
	}

	dirfd, cName, errno := n.prepareAtSyscall(name)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd)

	n2 := toNode(newParent)
	dirfd2, cName2, errno := n2.prepareAtSyscall(newName)
	if errno != 0 {
		return
	}
	defer syscall.Close(dirfd2)

	// Easy case.
	rn := n.rootNode()
	if rn.args.PlaintextNames {
		return fs.ToErrno(syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags)))
	}
	// Long destination file name: create .name file
	nameFileAlreadyThere := false
	var err error
	if nametransform.IsLongContent(cName2) {
		err = rn.nameTransform.WriteLongNameAt(dirfd2, cName2, newName)
		// Failure to write the .name file is expected when the target path already
		// exists. Since hashes are pretty unique, there is no need to modify the
		// .name file in this case, and we ignore the error.
		if err == syscall.EEXIST {
			nameFileAlreadyThere = true
		} else if err != nil {
			return fs.ToErrno(err)
		}
	}
	// Actual rename
	tlog.Debug.Printf("Renameat %d/%s -> %d/%s\n", dirfd, cName, dirfd2, cName2)
	err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
	if (flags&syscallcompat.RENAME_NOREPLACE == 0) && (err == syscall.ENOTEMPTY || err == syscall.EEXIST) {
		// If an empty directory is overwritten we will always get an error as
		// the "empty" directory will still contain gocryptfs.diriv.
		// Interestingly, ext4 returns ENOTEMPTY while xfs returns EEXIST.
		// We handle that by trying to fs.Rmdir() the target directory and trying
		// again.
		tlog.Debug.Printf("Rename: Handling ENOTEMPTY")
		if n2.Rmdir(ctx, newName) == 0 {
			err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
		}
	}
	if err != nil {
		if nametransform.IsLongContent(cName2) && nameFileAlreadyThere == false {
			// Roll back .name creation unless the .name file was already there
			nametransform.DeleteLongNameAt(dirfd2, cName2)
		}
		return fs.ToErrno(err)
	}
	if nametransform.IsLongContent(cName) {
		nametransform.DeleteLongNameAt(dirfd, cName)
	}
	return 0
}