package fusefrontend_reverse import ( "encoding/base64" "log" "path/filepath" "strings" "syscall" "github.com/rfjakob/gocryptfs/internal/nametransform" "github.com/rfjakob/gocryptfs/internal/pathiv" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) // rDecryptName decrypts the ciphertext name "cName", given the dirIV of the // directory "cName" lies in. The relative plaintext path to the directory // "pDir" is used if a "gocryptfs.longname.XYZ.name" must be resolved. func (rfs *RootNode) rDecryptName(cName string, dirIV []byte, pDir string) (pName string, err error) { nameType := nametransform.NameType(cName) if nameType == nametransform.LongNameNone { pName, err = rfs.nameTransform.DecryptName(cName, dirIV) if err != nil { // We get lots of decrypt requests for names like ".Trash" that // are invalid base64. Convert them to ENOENT so the correct // error gets returned to the user. if _, ok := err.(base64.CorruptInputError); ok { return "", syscall.ENOENT } // Stat attempts on the link target of encrypted symlinks. // These are always valid base64 but the length is not a // multiple of 16. if err == syscall.EBADMSG { return "", syscall.ENOENT } return "", err } } else if nameType == nametransform.LongNameContent { dirfd, err := syscallcompat.OpenDirNofollow(rfs.args.Cipherdir, filepath.Dir(pDir)) if err != nil { return "", err } defer syscall.Close(dirfd) fd, err := syscallcompat.Openat(dirfd, filepath.Base(pDir), syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0) if err != nil { return "", err } defer syscall.Close(fd) var errno syscall.Errno pName, _, errno = rfs.findLongnameParent(fd, dirIV, cName) if errno != 0 { return "", errno } } else { // It makes no sense to decrypt a ".name" file. This is a virtual file // that has no representation in the plaintext filesystem. ".name" // files should have already been handled in virtualfile.go. tlog.Warn.Printf("rDecryptName: cannot decrypt virtual file %q", cName) return "", syscall.EINVAL } return pName, nil } // decryptPath decrypts a relative ciphertext path to a relative plaintext // path. func (rn *RootNode) decryptPath(cPath string) (string, error) { if rn.args.PlaintextNames || cPath == "" { return cPath, nil } parts := strings.Split(cPath, "/") var transformedParts []string for i := range parts { // Start at the top and recurse currentCipherDir := filepath.Join(parts[:i]...) currentPlainDir := filepath.Join(transformedParts[:i]...) dirIV := rn.deriveDirIV(currentCipherDir) transformedPart, err := rn.rDecryptName(parts[i], dirIV, currentPlainDir) if err != nil { return "", err } transformedParts = append(transformedParts, transformedPart) } pRelPath := filepath.Join(transformedParts...) return pRelPath, nil } // deriveDirIV wraps pathiv.Derive but takes DeterministicNames into account. func (rn *RootNode) deriveDirIV(cPath string) []byte { if rn.args.PlaintextNames { log.Panic("BUG: deriveDirIV called but PlaintextNames is set") } if rn.args.DeterministicNames { return make([]byte, nametransform.DirIVLen) } return pathiv.Derive(cPath, pathiv.PurposeDirIV) } // openBackingDir receives an already decrypted relative path // "pRelPath", opens the directory that contains the target file/dir // and returns the fd to the directory and the decrypted name of the // target file. The fd/name pair is intended for use with fchownat and // friends. func (rn *RootNode) openBackingDir(cPath string) (dirfd int, pPath string, err error) { defer func() { tlog.Debug.Printf("openBackingDir %q -> %d %q %v\n", cPath, dirfd, pPath, err) }() dirfd = -1 pPath, err = rn.decryptPath(cPath) if err != nil { return } if rn.isExcludedPlain(pPath) { err = syscall.EPERM return } // Open directory, safe against symlink races pDir := filepath.Dir(pPath) dirfd, err = syscallcompat.OpenDirNofollow(rn.args.Cipherdir, pDir) if err != nil { return } return dirfd, pPath, nil }