summaryrefslogtreecommitdiff
path: root/mount.go
blob: eeeffe8c4a6f2424572499b06842aa1089cd8979 (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
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
package main

import (
	"encoding/json"
	"fmt"
	"log"
	"log/syslog"
	"math"
	"net"
	"os"
	"os/exec"
	"os/signal"
	"path"
	"path/filepath"
	"runtime"
	"runtime/debug"
	"strings"
	"sync/atomic"
	"syscall"
	"time"

	"golang.org/x/sys/unix"

	"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/ctlsock"
	"github.com/rfjakob/gocryptfs/internal/exitcodes"
	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
	"github.com/rfjakob/gocryptfs/internal/fusefrontend_reverse"
	"github.com/rfjakob/gocryptfs/internal/nametransform"
	"github.com/rfjakob/gocryptfs/internal/openfiletable"
	"github.com/rfjakob/gocryptfs/internal/tlog"
)

// doMount mounts an encrypted directory.
// Called from main.
func doMount(args *argContainer) {
	// Check mountpoint
	var err error
	args.mountpoint, err = filepath.Abs(flagSet.Arg(1))
	if err != nil {
		tlog.Fatal.Printf("Invalid mountpoint: %v", err)
		os.Exit(exitcodes.MountPoint)
	}
	// We cannot mount "/home/user/.cipher" at "/home/user" because the mount
	// will hide ".cipher" also for us.
	if args.cipherdir == args.mountpoint || strings.HasPrefix(args.cipherdir, args.mountpoint+"/") {
		tlog.Fatal.Printf("Mountpoint %q would shadow cipherdir %q, this is not supported",
			args.mountpoint, args.cipherdir)
		os.Exit(exitcodes.MountPoint)
	}
	// Reverse-mounting "/foo" at "/foo/mnt" means we would be recursively
	// encrypting ourselves.
	if strings.HasPrefix(args.mountpoint, args.cipherdir+"/") {
		tlog.Fatal.Printf("Mountpoint %q is contained in cipherdir %q, this is not supported",
			args.mountpoint, args.cipherdir)
		os.Exit(exitcodes.MountPoint)
	}
	if args.nonempty {
		err = isDir(args.mountpoint)
	} else {
		err = isEmptyDir(args.mountpoint)
		// OSXFuse will create the mountpoint for us ( https://github.com/rfjakob/gocryptfs/issues/194 )
		if runtime.GOOS == "darwin" && os.IsNotExist(err) {
			tlog.Info.Printf("Mountpoint %q does not exist, but should be created by OSXFuse",
				args.mountpoint)
			err = nil
		}
	}
	if err != nil {
		tlog.Fatal.Printf("Invalid mountpoint: %v", err)
		os.Exit(exitcodes.MountPoint)
	}
	// Open control socket early so we can error out before asking the user
	// for the password
	if args.ctlsock != "" {
		// We must use an absolute path because we cd to / when daemonizing.
		// This messes up the delete-on-close logic in the unix socket object.
		args.ctlsock, _ = filepath.Abs(args.ctlsock)
		var sock net.Listener
		sock, err = net.Listen("unix", args.ctlsock)
		if err != nil {
			tlog.Fatal.Printf("ctlsock: %v", err)
			os.Exit(exitcodes.CtlSock)
		}
		args._ctlsockFd = sock
		// Close also deletes the socket file
		defer func() {
			err = sock.Close()
			if err != nil {
				tlog.Warn.Printf("ctlsock close: %v", err)
			}
		}()
	}
	// Preallocation on Btrfs is broken ( https://github.com/rfjakob/gocryptfs/issues/395 )
	// and slow ( https://github.com/rfjakob/gocryptfs/issues/63 ).
	if !args.noprealloc {
		// darwin does not have unix.BTRFS_SUPER_MAGIC, so we define it here
		const BTRFS_SUPER_MAGIC = 0x9123683e
		var st unix.Statfs_t
		err = unix.Statfs(args.cipherdir, &st)
		// Cast to uint32 avoids compile error on arm: "constant 2435016766 overflows int32"
		if err == nil && uint32(st.Type) == BTRFS_SUPER_MAGIC {
			tlog.Info.Printf(tlog.ColorYellow +
				"Btrfs detected, forcing -noprealloc. See https://github.com/rfjakob/gocryptfs/issues/395 for why." +
				tlog.ColorReset)
			args.noprealloc = true
		}
	}
	// We cannot use JSON for pretty-printing as the fields are unexported
	tlog.Debug.Printf("cli args: %#v", args)
	// Initialize gocryptfs (read config file, ask for password, ...)
	fs, wipeKeys := initFuseFrontend(args)
	// Initialize go-fuse FUSE server
	srv := initGoFuse(fs, args)
	// Try to wipe secret keys from memory after unmount
	defer wipeKeys()

	tlog.Info.Println(tlog.ColorGreen + "Filesystem mounted and ready." + tlog.ColorReset)
	// We have been forked into the background, as evidenced by the set
	// "notifypid".
	if args.notifypid > 0 {
		// Chdir to the root directory so we don't block unmounting the CWD
		os.Chdir("/")
		// Switch to syslog
		if !args.nosyslog {
			// Switch all of our logs and the generic logger to syslog
			tlog.Info.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_INFO)
			tlog.Debug.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_DEBUG)
			tlog.Warn.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
			tlog.Fatal.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_CRIT)
			tlog.SwitchLoggerToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
			// Daemons should redirect stdin, stdout and stderr
			redirectStdFds()
		}
		// Disconnect from the controlling terminal by creating a new session.
		// This prevents us from getting SIGINT when the user presses Ctrl-C
		// to exit a running script that has called gocryptfs.
		_, err = syscall.Setsid()
		if err != nil {
			tlog.Warn.Printf("Setsid: %v", err)
		}
		// Send SIGUSR1 to our parent
		sendUsr1(args.notifypid)
	}
	// Increase the open file limit to 4096. This is not essential, so do it after
	// we have switched to syslog and don't bother the user with warnings.
	setOpenFileLimit()
	// Wait for SIGINT in the background and unmount ourselves if we get it.
	// This prevents a dangling "Transport endpoint is not connected"
	// mountpoint if the user hits CTRL-C.
	handleSigint(srv, args.mountpoint)
	// Return memory that was allocated for scrypt (64M by default!) and other
	// stuff that is no longer needed to the OS
	debug.FreeOSMemory()
	// Set up autounmount, if requested.
	if args.idle > 0 && !args.reverse {
		// Not being in reverse mode means we always have a forward file system.
		fwdFs := fs.(*fusefrontend.FS)
		go idleMonitor(args.idle, fwdFs, srv, args.mountpoint)
	}
	// Jump into server loop. Returns when it gets an umount request from the kernel.
	srv.Serve()
}

// Based on the EncFS idle monitor:
// https://github.com/vgough/encfs/blob/1974b417af189a41ffae4c6feb011d2a0498e437/encfs/main.cpp#L851
// idleMonitor is a function to be run as a thread that checks for
// filesystem idleness and unmounts if we've been idle for long enough.
const checksDuringTimeoutPeriod = 4

func idleMonitor(idleTimeout time.Duration, fs *fusefrontend.FS, srv *fuse.Server, mountpoint string) {
	sleepTimeBetweenChecks := contentenc.MinUint64(
		uint64(idleTimeout/checksDuringTimeoutPeriod),
		uint64(2*time.Minute))
	timeoutCycles := int(math.Ceil(float64(idleTimeout) / float64(sleepTimeBetweenChecks)))
	idleCount := 0
	for {
		// Atomically check whether the access flag is set and reset it to 0 if so.
		recentAccess := atomic.CompareAndSwapUint32(&fs.AccessedSinceLastCheck, 1, 0)
		// Any form of current or recent access resets the idle counter.
		openFileCount := openfiletable.CountOpenFiles()
		if recentAccess || openFileCount > 0 {
			idleCount = 0
		} else {
			idleCount++
		}
		tlog.Debug.Printf(
			"Checking for idle (recentAccess = %t, open = %d): %s",
			recentAccess, openFileCount, time.Now().String())
		if idleCount > 0 && idleCount%timeoutCycles == 0 {
			tlog.Info.Printf("Filesystem idle; unmounting: %s", mountpoint)
			unmount(srv, mountpoint)
		}
		time.Sleep(time.Duration(sleepTimeBetweenChecks))
	}
}

// setOpenFileLimit tries to increase the open file limit to 4096 (the default hard
// limit on Linux).
func setOpenFileLimit() {
	var lim syscall.Rlimit
	err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
	if err != nil {
		tlog.Warn.Printf("Getting RLIMIT_NOFILE failed: %v", err)
		return
	}
	if lim.Cur >= 4096 {
		return
	}
	lim.Cur = 4096
	err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &lim)
	if err != nil {
		tlog.Warn.Printf("Setting RLIMIT_NOFILE to %+v failed: %v", lim, err)
		//         %+v output: "{Cur:4097 Max:4096}" ^
	}
}

// ctlsockFs satisfies both the pathfs.FileSystem and the ctlsock.Interface
// interfaces
type ctlsockFs interface {
	pathfs.FileSystem
	ctlsock.Interface
}

// initFuseFrontend - initialize gocryptfs/fusefrontend
// Calls os.Exit on errors
func initFuseFrontend(args *argContainer) (pfs pathfs.FileSystem, wipeKeys func()) {
	// Get master key (may prompt for the password) and read config file
	masterkey, confFile := getMasterKey(args)
	// Reconciliate CLI and config file arguments into a fusefrontend.Args struct
	// that is passed to the filesystem implementation
	cryptoBackend := cryptocore.BackendGoGCM
	if args.openssl {
		cryptoBackend = cryptocore.BackendOpenSSL
	}
	if args.aessiv {
		cryptoBackend = cryptocore.BackendAESSIV
	}
	// forceOwner implies allow_other, as documented.
	// Set this early, so args.allow_other can be relied on below this point.
	if args._forceOwner != nil {
		args.allow_other = true
	}
	frontendArgs := fusefrontend.Args{
		Cipherdir:       args.cipherdir,
		PlaintextNames:  args.plaintextnames,
		LongNames:       args.longnames,
		ConfigCustom:    args._configCustom,
		NoPrealloc:      args.noprealloc,
		SerializeReads:  args.serialize_reads,
		ForceDecode:     args.forcedecode,
		ForceOwner:      args._forceOwner,
		Exclude:         args.exclude,
		ExcludeWildcard: args.excludeWildcard,
		ExcludeFrom:     args.excludeFrom,
	}
	// confFile is nil when "-zerokey" or "-masterkey" was used
	if confFile != nil {
		// Settings from the config file override command line args
		frontendArgs.PlaintextNames = confFile.IsFeatureFlagSet(configfile.FlagPlaintextNames)
		args.raw64 = confFile.IsFeatureFlagSet(configfile.FlagRaw64)
		args.hkdf = confFile.IsFeatureFlagSet(configfile.FlagHKDF)
		if confFile.IsFeatureFlagSet(configfile.FlagAESSIV) {
			cryptoBackend = cryptocore.BackendAESSIV
		} else if args.reverse {
			tlog.Fatal.Printf("AES-SIV is required by reverse mode, but not enabled in the config file")
			os.Exit(exitcodes.Usage)
		}
	}
	// If allow_other is set and we run as root, try to give newly created files to
	// the right user.
	if args.allow_other && os.Getuid() == 0 {
		frontendArgs.PreserveOwner = true
	}
	jsonBytes, _ := json.MarshalIndent(frontendArgs, "", "\t")
	tlog.Debug.Printf("frontendArgs: %s", string(jsonBytes))

	// Init crypto backend
	cCore := cryptocore.New(masterkey, cryptoBackend, contentenc.DefaultIVBits, args.hkdf, args.forcedecode)
	cEnc := contentenc.New(cCore, contentenc.DefaultBS, args.forcedecode)
	nameTransform := nametransform.New(cCore.EMECipher, frontendArgs.LongNames, args.raw64)
	// After the crypto backend is initialized,
	// we can purge the master key from memory.
	for i := range masterkey {
		masterkey[i] = 0
	}
	masterkey = nil
	// Spawn fusefrontend
	var fs ctlsockFs
	if args.reverse {
		if cryptoBackend != cryptocore.BackendAESSIV {
			log.Panic("reverse mode must use AES-SIV, everything else is insecure")
		}
		fs = fusefrontend_reverse.NewFS(frontendArgs, cEnc, nameTransform)

	} else {
		fs = fusefrontend.NewFS(frontendArgs, cEnc, nameTransform)
	}
	// We have opened the socket early so that we cannot fail here after
	// asking the user for the password
	if args._ctlsockFd != nil {
		go ctlsock.Serve(args._ctlsockFd, fs)
	}
	return fs, func() { cCore.Wipe() }
}

func initGoFuse(fs pathfs.FileSystem, args *argContainer) *fuse.Server {
	// pathFsOpts are passed into go-fuse/pathfs
	pathFsOpts := &pathfs.PathNodeFsOptions{ClientInodes: true}
	if args.sharedstorage {
		// shared storage mode disables hard link tracking as the backing inode
		// numbers may change behind our back:
		// https://github.com/rfjakob/gocryptfs/issues/156
		pathFsOpts.ClientInodes = false
	}
	if args.reverse {
		// Reverse mode is read-only, so we don't need a working link().
		// Disable hard link tracking to avoid strange breakage on duplicate
		// inode numbers ( https://github.com/rfjakob/gocryptfs/issues/149 ).
		pathFsOpts.ClientInodes = false
	}
	pathFs := pathfs.NewPathNodeFs(fs, pathFsOpts)
	var fuseOpts *nodefs.Options
	if args.sharedstorage {
		// sharedstorage mode sets all cache timeouts to zero so changes to the
		// backing shared storage show up immediately.
		fuseOpts = &nodefs.Options{}
	} else {
		fuseOpts = &nodefs.Options{
			// These options are to be compatible with libfuse defaults,
			// making benchmarking easier.
			NegativeTimeout: time.Second,
			AttrTimeout:     time.Second,
			EntryTimeout:    time.Second,
		}
	}
	conn := nodefs.NewFileSystemConnector(pathFs.Root(), fuseOpts)
	mOpts := fuse.MountOptions{
		// Writes and reads are usually capped at 128kiB on Linux through
		// the FUSE_MAX_PAGES_PER_REQ kernel constant in fuse_i.h. Our
		// sync.Pool buffer pools are sized acc. to the default. Users may set
		// the kernel constant higher, and Synology NAS kernels are known to
		// have it >128kiB. We cannot handle more than 128kiB, so we tell
		// the kernel to limit the size explicitly.
		MaxWrite: fuse.MAX_KERNEL_WRITE,
		Options:  []string{fmt.Sprintf("max_read=%d", fuse.MAX_KERNEL_WRITE)},
	}
	if args.allow_other {
		tlog.Info.Printf(tlog.ColorYellow + "The option \"-allow_other\" is set. Make sure the file " +
			"permissions protect your data from unwanted access." + tlog.ColorReset)
		mOpts.AllowOther = true
		// Make the kernel check the file permissions for us
		mOpts.Options = append(mOpts.Options, "default_permissions")
	}
	if args.forcedecode {
		tlog.Info.Printf(tlog.ColorYellow + "THE OPTION \"-forcedecode\" IS ACTIVE. GOCRYPTFS WILL RETURN CORRUPT DATA!" +
			tlog.ColorReset)
	}
	if args.nonempty {
		mOpts.Options = append(mOpts.Options, "nonempty")
	}
	// Set values shown in "df -T" and friends
	// First column, "Filesystem"
	fsname := args.cipherdir
	if args.fsname != "" {
		fsname = args.fsname
	}
	fsname2 := strings.Replace(fsname, ",", "_", -1)
	if fsname2 != fsname {
		tlog.Warn.Printf("Warning: %q will be displayed as %q in \"df -T\"", fsname, fsname2)
		fsname = fsname2
	}
	mOpts.Options = append(mOpts.Options, "fsname="+fsname)
	// Second column, "Type", will be shown as "fuse." + Name
	mOpts.Name = "gocryptfs"
	if args.reverse {
		mOpts.Name += "-reverse"
	}
	// Add a volume name if running osxfuse. Otherwise the Finder will show it as
	// something like "osxfuse Volume 0 (gocryptfs)".
	if runtime.GOOS == "darwin" {
		volname := strings.Replace(path.Base(args.mountpoint), ",", "_", -1)
		mOpts.Options = append(mOpts.Options, "volname="+volname)
	}
	// The kernel enforces read-only operation, we just have to pass "ro".
	// Reverse mounts are always read-only.
	if args.ro || args.reverse {
		mOpts.Options = append(mOpts.Options, "ro")
	} else if args.rw {
		mOpts.Options = append(mOpts.Options, "rw")
	}
	// If both "nosuid" and "suid" were passed, the safer option wins.
	if args.nosuid {
		mOpts.Options = append(mOpts.Options, "nosuid")
	} else if args.suid {
		mOpts.Options = append(mOpts.Options, "suid")
	}
	if args.nodev {
		mOpts.Options = append(mOpts.Options, "nodev")
	} else if args.dev {
		mOpts.Options = append(mOpts.Options, "dev")
	}
	if args.noexec {
		mOpts.Options = append(mOpts.Options, "noexec")
	} else if args.exec {
		mOpts.Options = append(mOpts.Options, "exec")
	}
	// Add additional mount options (if any) after the stock ones, so the user has
	// a chance to override them.
	if args.ko != "" {
		parts := strings.Split(args.ko, ",")
		tlog.Debug.Printf("Adding -ko mount options: %v", parts)
		mOpts.Options = append(mOpts.Options, parts...)
	}
	srv, err := fuse.NewServer(conn.RawFS(), args.mountpoint, &mOpts)
	if err != nil {
		tlog.Fatal.Printf("fuse.NewServer failed: %s", strings.TrimSpace(err.Error()))
		if runtime.GOOS == "darwin" {
			tlog.Info.Printf("Maybe you should run: /Library/Filesystems/osxfuse.fs/Contents/Resources/load_osxfuse")
		}
		os.Exit(exitcodes.FuseNewServer)
	}
	srv.SetDebug(args.fusedebug)

	// All FUSE file and directory create calls carry explicit permission
	// information. We need an unrestricted umask to create the files and
	// directories with the requested permissions.
	syscall.Umask(0000)

	return srv
}

func handleSigint(srv *fuse.Server, mountpoint string) {
	ch := make(chan os.Signal, 1)
	signal.Notify(ch, os.Interrupt)
	signal.Notify(ch, syscall.SIGTERM)
	go func() {
		<-ch
		unmount(srv, mountpoint)
		os.Exit(exitcodes.SigInt)
	}()
}

func unmount(srv *fuse.Server, mountpoint string) {
	err := srv.Unmount()
	if err != nil {
		tlog.Warn.Printf("unmount: srv.Unmount returned %v", err)
		if runtime.GOOS == "linux" {
			// MacOSX does not support lazy unmount
			tlog.Info.Printf("Trying lazy unmount")
			cmd := exec.Command("fusermount", "-u", "-z", mountpoint)
			cmd.Stdout = os.Stdout
			cmd.Stderr = os.Stderr
			cmd.Run()
		}
	}
}