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Diffstat (limited to 'internal/fusefrontend/openbackingdir.go')
-rw-r--r--internal/fusefrontend/openbackingdir.go63
1 files changed, 63 insertions, 0 deletions
diff --git a/internal/fusefrontend/openbackingdir.go b/internal/fusefrontend/openbackingdir.go
new file mode 100644
index 0000000..849a486
--- /dev/null
+++ b/internal/fusefrontend/openbackingdir.go
@@ -0,0 +1,63 @@
+package fusefrontend
+
+import (
+ "path/filepath"
+ "strings"
+ "syscall"
+
+ "github.com/rfjakob/gocryptfs/internal/nametransform"
+ "github.com/rfjakob/gocryptfs/internal/syscallcompat"
+)
+
+// openBackingDir opens the parent ciphertext directory of plaintext path
+// "relPath" and returns the dirfd and the encrypted basename.
+//
+// The caller should then use Openat(dirfd, cName, ...) and friends.
+// For convenience, if relPath is "", cName is going to be ".".
+//
+// openBackingDir is secure against symlink races by using Openat and
+// ReadDirIVAt.
+func (fs *FS) openBackingDir(relPath string) (dirfd int, cName string, err error) {
+ // With PlaintextNames, we don't need to read DirIVs. Easy.
+ if fs.args.PlaintextNames {
+ dir := nametransform.Dir(relPath)
+ dirfd, err = syscallcompat.OpenDirNofollow(fs.args.Cipherdir, dir)
+ if err != nil {
+ return -1, "", err
+ }
+ // If relPath is empty, cName is ".".
+ cName = filepath.Base(relPath)
+ return dirfd, cName, nil
+ }
+ // Open cipherdir (following symlinks)
+ dirfd, err = syscall.Open(fs.args.Cipherdir, syscall.O_RDONLY|syscall.O_DIRECTORY|syscallcompat.O_PATH, 0)
+ if err != nil {
+ return -1, "", err
+ }
+ // If relPath is empty, cName is ".".
+ if relPath == "" {
+ return dirfd, ".", nil
+ }
+ // Walk the directory tree
+ parts := strings.Split(relPath, "/")
+ for i, name := range parts {
+ iv, err := nametransform.ReadDirIVAt(dirfd)
+ if err != nil {
+ syscall.Close(dirfd)
+ return -1, "", err
+ }
+ cName = fs.nameTransform.EncryptAndHashName(name, iv)
+ // Last part? We are done.
+ if i == len(parts)-1 {
+ break
+ }
+ // Not the last part? Descend into next directory.
+ dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_DIRECTORY|syscallcompat.O_PATH, 0)
+ syscall.Close(dirfd)
+ if err != nil {
+ return -1, "", err
+ }
+ dirfd = dirfd2
+ }
+ return dirfd, cName, nil
+}