libgocryptfs/mount.go

375 lines
13 KiB
Go

package main
import (
"encoding/json"
"fmt"
"log/syslog"
"net"
"os"
"os/exec"
"os/signal"
"path"
"path/filepath"
"runtime"
"runtime/debug"
"strings"
"syscall"
"time"
"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/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/readpassword"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// doMount mounts an encrypted directory.
// Called from main.
func doMount(args *argContainer) int {
// 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 = checkDir(args.mountpoint)
} else {
err = checkDirEmpty(args.mountpoint)
}
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.Print(err)
}
}()
}
// Get master key (may prompt for the password)
var masterkey []byte
var confFile *configfile.ConfFile
if args.masterkey != "" {
// "-masterkey"
masterkey = parseMasterKey(args.masterkey)
} else if args.zerokey {
// "-zerokey"
tlog.Info.Printf("Using all-zero dummy master key.")
tlog.Info.Printf(tlog.ColorYellow +
"ZEROKEY MODE PROVIDES NO SECURITY AT ALL AND SHOULD ONLY BE USED FOR TESTING." +
tlog.ColorReset)
masterkey = make([]byte, cryptocore.KeyLen)
} else {
// Load master key from config file
// Prompts the user for the password
masterkey, confFile, err = loadConfig(args)
if err != nil {
if args._ctlsockFd != nil {
// Close the socket file (which also deletes it)
args._ctlsockFd.Close()
}
exitcodes.Exit(err)
}
readpassword.CheckTrailingGarbage()
printMasterKey(masterkey)
}
// We cannot use JSON for pretty-printing as the fields are unexported
tlog.Debug.Printf("cli args: %#v", args)
// Initialize FUSE server
srv := initFuseFrontend(masterkey, args, confFile)
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.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()
// Jump into server loop. Returns when it gets an umount request from the kernel.
srv.Serve()
return 0
}
// 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}" ^
}
}
// initFuseFrontend - initialize gocryptfs/fusefrontend
// Calls os.Exit on errors
func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile.ConfFile) *fuse.Server {
// 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,
CryptoBackend: cryptoBackend,
ConfigCustom: args._configCustom,
Raw64: args.raw64,
NoPrealloc: args.noprealloc,
HKDF: args.hkdf,
SerializeReads: args.serialize_reads,
ForceDecode: args.forcedecode,
ForceOwner: args._forceOwner,
}
// 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)
frontendArgs.Raw64 = confFile.IsFeatureFlagSet(configfile.FlagRaw64)
frontendArgs.HKDF = confFile.IsFeatureFlagSet(configfile.FlagHKDF)
if confFile.IsFeatureFlagSet(configfile.FlagAESSIV) {
frontendArgs.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))
var finalFs pathfs.FileSystem
var ctlSockBackend ctlsock.Interface
// 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 {
// The dance with the intermediate variables is because we need to
// cast the FS into pathfs.FileSystem *and* ctlsock.Interface. This
// avoids using interface{}.
fs := fusefrontend_reverse.NewFS(masterkey, frontendArgs)
finalFs = fs
ctlSockBackend = fs
// 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
} else {
fs := fusefrontend.NewFS(masterkey, frontendArgs)
finalFs = fs
ctlSockBackend = fs
}
// fusefrontend / fusefrontend_reverse have initialized their crypto with
// derived keys (HKDF), we can purge the master key from memory.
for i := range masterkey {
masterkey[i] = 0
}
// 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, ctlSockBackend)
}
pathFs := pathfs.NewPathNodeFs(finalFs, 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 explicitely.
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
}
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" {
mOpts.Options = append(mOpts.Options, "volname="+path.Base(args.mountpoint))
}
// 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")
}
// 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: %v", err)
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
err := srv.Unmount()
if err != nil {
tlog.Warn.Print(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()
}
}
os.Exit(exitcodes.SigInt)
}()
}