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libgocryptfs
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Rmdir: handle creating and removing unreadable directories 

This patch also splits off Mkdir and Rmdir into its own file.

Fixes issue #8, thanks to @diseq for the bug report.
This commit is contained in:
Jakob Unterwurzacher 2015-12-11 19:54:53 +01:00
parent 78cd97c5e9
commit e99e841713
5 changed files with 196 additions and 100 deletions
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7
cryptfs/nonce.go
View File

@ -1,6 +1,7 @@
package cryptfs
import (
"encoding/binary"
"bytes"
"crypto/rand"
"encoding/hex"
@ -17,6 +18,12 @@ func RandBytes(n int) []byte {
return b
}
// Return a secure random uint64
func RandUint64() uint64 {
b := RandBytes(8)
return binary.BigEndian.Uint64(b)
}
var gcmNonce nonce96
type nonce96 struct {

32
integration_tests/helpers.go
View File

@ -127,6 +127,38 @@ func testMkdirRmdir(t *testing.T, plainDir string) {
if err != nil {
t.Fatal(err)
}
// Removing a non-empty dir should fail with ENOTEMPTY
if os.Mkdir(dir, 0777) != nil {
t.Fatal(err)
}
f, err := os.Create(dir + "/file")
if err != nil {
t.Fatal(err)
}
f.Close()
err = syscall.Rmdir(dir)
errno := err.(syscall.Errno)
if errno != syscall.ENOTEMPTY {
t.Errorf("Should have gotten ENOTEMPTY, go %v", errno)
}
if syscall.Unlink(dir + "/file") != nil {
t.Fatal(err)
}
if syscall.Rmdir(dir) != nil {
t.Fatal(err)
}
// We should also be able to remove a directory we do not have permissions to
// read or write
err = os.Mkdir(dir, 0000)
if err != nil {
t.Fatal(err)
}
err = syscall.Rmdir(dir)
if err != nil {
t.Fatal(err)
}
}
// Create and rename a file

7
main.go
View File

@ -159,7 +159,7 @@ func main() {
"Setting this to a lower value speeds up mounting but makes the password susceptible to brute-force attacks")
flagSet.Parse(os.Args[1:])
// Fork a child into the background if "-f" is not set and we are mounting a filesystem
// Fork a child into the background if "-f" is not set AND we are mounting a filesystem
if !args.foreground && flagSet.NArg() == 2 {
forkChild() // does not return
}
@ -339,6 +339,11 @@ func pathfsFrontend(key []byte, args argContainer, confFile *cryptfs.ConfFile) *
}
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
}

99
pathfs_frontend/fs.go
View File

@ -2,7 +2,6 @@ package pathfs_frontend
import (
"encoding/base64"
"fmt"
"os"
"path/filepath"
"sync"
@ -245,40 +244,7 @@ func (fs *FS) Readlink(path string, context *fuse.Context) (out string, status f
return string(target), fuse.OK
}
func (fs *FS) Mkdir(relPath string, mode uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(relPath) {
return fuse.EPERM
}
encPath, err := fs.getBackingPath(relPath)
if err != nil {
return fuse.ToStatus(err)
}
if !fs.args.DirIV {
return fuse.ToStatus(os.Mkdir(encPath, os.FileMode(mode)))
}
// The new directory may take the place of an older one that is still in the cache
fs.CryptFS.DirIVCacheEnc.Clear()
// Create directory
fs.dirIVLock.Lock()
defer fs.dirIVLock.Unlock()
err = os.Mkdir(encPath, os.FileMode(mode))
if err != nil {
return fuse.ToStatus(err)
}
// Create gocryptfs.diriv inside
err = cryptfs.WriteDirIV(encPath)
if err != nil {
// This should not happen
cryptfs.Warn.Printf("Creating %s in dir %s failed: %v\n", cryptfs.DIRIV_FILENAME, encPath, err)
err2 := syscall.Rmdir(encPath)
if err2 != nil {
cryptfs.Warn.Printf("Mkdir: Rollback failed: %v\n", err2)
}
return fuse.ToStatus(err)
}
return fuse.OK
}
func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(path) {
@ -291,71 +257,6 @@ func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
return fuse.ToStatus(syscall.Unlink(cPath))
}
func (fs *FS) Rmdir(name string, context *fuse.Context) (code fuse.Status) {
encPath, err := fs.getBackingPath(name)
if err != nil {
return fuse.ToStatus(err)
}
if !fs.args.DirIV {
return fuse.ToStatus(syscall.Rmdir(encPath))
}
// If the directory is not empty besides gocryptfs.diriv, do not even
// attempt the dance around gocryptfs.diriv.
fd, err := os.Open(encPath)
if err != nil {
return fuse.ToStatus(err)
}
defer fd.Close()
list, err := fd.Readdirnames(10)
if err != nil {
return fuse.ToStatus(err)
}
if len(list) > 1 {
return fuse.ToStatus(syscall.ENOTEMPTY)
}
// Move "gocryptfs.diriv" to the parent dir under name "gocryptfs.diriv.rmdir.INODENUMBER"
var st syscall.Stat_t
err = syscall.Fstat(int(fd.Fd()), &st)
if err != nil {
return fuse.ToStatus(err)
}
dirivPath := filepath.Join(encPath, cryptfs.DIRIV_FILENAME)
parentDir := filepath.Dir(encPath)
tmpName := fmt.Sprintf("gocryptfs.diriv.rmdir.%d", st.Ino)
tmpDirivPath := filepath.Join(parentDir, tmpName)
cryptfs.Debug.Printf("Rmdir: Renaming %s to %s\n", cryptfs.DIRIV_FILENAME, tmpDirivPath)
// The directory is in an inconsistent state between rename and rmdir. Protect against
// concurrent readers.
fs.dirIVLock.Lock()
defer fs.dirIVLock.Unlock()
err = os.Rename(dirivPath, tmpDirivPath)
if err != nil {
cryptfs.Warn.Printf("Rmdir: Renaming %s to %s failed: %v\n", cryptfs.DIRIV_FILENAME, tmpDirivPath, err)
return fuse.ToStatus(err)
}
// Actual Rmdir
err = syscall.Rmdir(encPath)
if err != nil {
// This can happen if another file in the directory was created in the
// meantime, undo the rename
err2 := os.Rename(tmpDirivPath, dirivPath)
if err2 != nil {
cryptfs.Warn.Printf("Rmdir: Rollback failed: %v\n", err2)
}
return fuse.ToStatus(err)
}
// Delete "gocryptfs.diriv.rmdir.INODENUMBER"
err = syscall.Unlink(tmpDirivPath)
if err != nil {
cryptfs.Warn.Printf("Rmdir: Could not clean up %s: %v\n", tmpName, err)
}
// The now-deleted directory may have been in the DirIV cache. Clear it.
fs.CryptFS.DirIVCacheEnc.Clear()
return fuse.OK
}
func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (code fuse.Status) {
cryptfs.Debug.Printf("Symlink(\"%s\", \"%s\")\n", target, linkName)
if fs.isFiltered(linkName) {

151
pathfs_frontend/fs_dir.go Normal file
View File

@ -0,0 +1,151 @@
package pathfs_frontend
import (
"os"
"path/filepath"
"syscall"
"fmt"
"github.com/hanwen/go-fuse/fuse"
"github.com/rfjakob/gocryptfs/cryptfs"
)
func (fs *FS) Mkdir(relPath string, mode uint32, context *fuse.Context) (code fuse.Status) {
if fs.isFiltered(relPath) {
return fuse.EPERM
}
encPath, err := fs.getBackingPath(relPath)
if err != nil {
return fuse.ToStatus(err)
}
if !fs.args.DirIV {
return fuse.ToStatus(os.Mkdir(encPath, os.FileMode(mode)))
}
// We need write and execute permissions to create gocryptfs.diriv
origMode := mode
mode = mode | 0300
// The new directory may take the place of an older one that is still in the cache
fs.CryptFS.DirIVCacheEnc.Clear()
// Create directory
fs.dirIVLock.Lock()
defer fs.dirIVLock.Unlock()
err = os.Mkdir(encPath, os.FileMode(mode))
if err != nil {
return fuse.ToStatus(err)
}
// Create gocryptfs.diriv inside
err = cryptfs.WriteDirIV(encPath)
if err != nil {
// This should not happen
cryptfs.Warn.Printf("Mkdir: WriteDirIV failed: %v\n", err)
err2 := syscall.Rmdir(encPath)
if err2 != nil {
cryptfs.Warn.Printf("Mkdir: Rmdir rollback failed: %v\n", err2)
}
return fuse.ToStatus(err)
}
// Set permissions back to what the user wanted
if origMode != mode {
err = os.Chmod(encPath, os.FileMode(origMode))
if err != nil {
cryptfs.Warn.Printf("Mkdir: Chmod failed: %v\n", err)
}
}
return fuse.OK
}
func (fs *FS) Rmdir(name string, context *fuse.Context) (code fuse.Status) {
encPath, err := fs.getBackingPath(name)
if err != nil {
return fuse.ToStatus(err)
}
if !fs.args.DirIV {
return fuse.ToStatus(syscall.Rmdir(encPath))
}
// If the directory is not empty besides gocryptfs.diriv, do not even
// attempt the dance around gocryptfs.diriv.
fd, err := os.Open(encPath)
if perr, ok := err.(*os.PathError); ok && perr.Err == syscall.EACCES {
// We need permission to read and modify the directory
cryptfs.Debug.Printf("Rmdir: handling EACCESS\n")
fi, err2 := os.Stat(encPath)
if err2 != nil {
cryptfs.Debug.Printf("Rmdir: Stat: %v\n", err2)
return fuse.ToStatus(err2)
}
origMode := fi.Mode()
newMode := origMode | 0700
err2 = os.Chmod(encPath, newMode)
if err2 != nil {
cryptfs.Debug.Printf("Rmdir: Chmod failed: %v\n", err2)
return fuse.ToStatus(err)
}
defer func () {
if code != fuse.OK {
// Undo the chmod if removing the directory failed
err3 := os.Chmod(encPath, origMode)
if err3 != nil {
cryptfs.Warn.Printf("Rmdir: Chmod rollback failed: %v\n", err2)
}
}
}()
// Retry open
fd, err = os.Open(encPath)
}
if err != nil {
cryptfs.Debug.Printf("Rmdir: Open: %v\n", err)
return fuse.ToStatus(err)
}
list, err := fd.Readdirnames(10)
fd.Close()
if err != nil {
cryptfs.Debug.Printf("Rmdir: Readdirnames: %v\n", err)
return fuse.ToStatus(err)
}
if len(list) > 1 {
return fuse.ToStatus(syscall.ENOTEMPTY)
} else if len(list) == 0 {
cryptfs.Warn.Printf("Rmdir: gocryptfs.diriv missing, allowing deletion\n")
return fuse.ToStatus(syscall.Rmdir(encPath))
}
// Move "gocryptfs.diriv" to the parent dir as "gocryptfs.diriv.rmdir.XYZ"
dirivPath := filepath.Join(encPath, cryptfs.DIRIV_FILENAME)
parentDir := filepath.Dir(encPath)
tmpName := fmt.Sprintf("gocryptfs.diriv.rmdir.%d", cryptfs.RandUint64())
tmpDirivPath := filepath.Join(parentDir, tmpName)
cryptfs.Debug.Printf("Rmdir: Renaming %s to %s\n", cryptfs.DIRIV_FILENAME, tmpDirivPath)
// The directory is in an inconsistent state between rename and rmdir. Protect against
// concurrent readers.
fs.dirIVLock.Lock()
defer fs.dirIVLock.Unlock()
err = os.Rename(dirivPath, tmpDirivPath)
if err != nil {
cryptfs.Warn.Printf("Rmdir: Renaming %s to %s failed: %v\n", cryptfs.DIRIV_FILENAME, tmpDirivPath, err)
return fuse.ToStatus(err)
}
// Actual Rmdir
err = syscall.Rmdir(encPath)
if err != nil {
// This can happen if another file in the directory was created in the
// meantime, undo the rename
err2 := os.Rename(tmpDirivPath, dirivPath)
if err2 != nil {
cryptfs.Warn.Printf("Rmdir: Rename rollback failed: %v\n", err2)
}
return fuse.ToStatus(err)
}
// Delete "gocryptfs.diriv.rmdir.INODENUMBER"
err = syscall.Unlink(tmpDirivPath)
if err != nil {
cryptfs.Warn.Printf("Rmdir: Could not clean up %s: %v\n", tmpName, err)
}
// The now-deleted directory may have been in the DirIV cache. Clear it.
fs.CryptFS.DirIVCacheEnc.Clear()
return fuse.OK
}