reverse: implement dynamic diriv

Introduce a unique per-directory diriv that is generated
by hashing the encrypted directory path.

1 files changed, 10 insertions, 37 deletions

diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
index 7e11ca3..a15b31a 100644
--- a/internal/fusefrontend_reverse/rpath.go
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -2,18 +2,11 @@ package fusefrontend_reverse
 
 import (
 	"encoding/base64"
-	"fmt"
 	"path/filepath"
 	"strings"
 	"syscall"
 )
 
-var zeroDirIV []byte
-
-func init() {
-	zeroDirIV = make([]byte, 16)
-}
-
 func (rfs *reverseFS) abs(relPath string, err error) (string, error) {
 	if err != nil {
 		return "", err
@@ -21,45 +14,25 @@ func (rfs *reverseFS) abs(relPath string, err error) (string, error) {
 	return filepath.Join(rfs.args.Cipherdir, relPath), nil
 }
 
-const (
-	ENCRYPT = iota
-	DECRYPT
-)
-
-func (rfs *reverseFS) encryptPath(relPath string) (string, error) {
-	return rfs.transformPath(relPath, ENCRYPT)
-}
-
 func (rfs *reverseFS) decryptPath(relPath string) (string, error) {
-	return rfs.transformPath(relPath, DECRYPT)
-}
-
-func (rfs *reverseFS) transformPath(relPath string, direction int) (string, error) {
 	if rfs.args.PlaintextNames || relPath == "" {
 		return relPath, nil
 	}
 	var err error
 	var transformedParts []string
 	parts := strings.Split(relPath, "/")
-	for _, part := range parts {
+	for i, part := range parts {
 		var transformedPart string
-		switch direction {
-		case ENCRYPT:
-			transformedPart = rfs.nameTransform.EncryptName(part, zeroDirIV)
-		case DECRYPT:
-			transformedPart, err = rfs.nameTransform.DecryptName(part, zeroDirIV)
-			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 {
-					fmt.Printf("converting to ENOENT\n")
-					return "", syscall.ENOENT
-				}
-				return "", err
+		dirIV := deriveDirIV(filepath.Join(parts[:i]...))
+		transformedPart, err = rfs.nameTransform.DecryptName(part, 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
 			}
-		default:
-			panic("bug: invalid direction value")
+			return "", err
 		}
 		transformedParts = append(transformedParts, transformedPart)
 	}