reverse: resolve long names in Open and GetAttr

The last patch added functionality for generating gocryptfs.longname.*
files, this patch adds support for mapping them back to the full
filenames.

Note that resolving a long name needs a full readdir. A cache
will be implemented later on to improve performance.

1 files changed, 32 insertions, 9 deletions

diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
index a15b31a..19539bb 100644
--- a/internal/fusefrontend_reverse/rpath.go
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -5,8 +5,19 @@ import (
 	"path/filepath"
 	"strings"
 	"syscall"
+
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
 )
 
+// saneDir is like filepath.Dir but returns "" instead of "."
+func saneDir(path string) string {
+	d := filepath.Dir(path)
+	if d == "." {
+		return ""
+	}
+	return d
+}
+
 func (rfs *reverseFS) abs(relPath string, err error) (string, error) {
 	if err != nil {
 		return "", err
@@ -22,17 +33,29 @@ func (rfs *reverseFS) decryptPath(relPath string) (string, error) {
 	var transformedParts []string
 	parts := strings.Split(relPath, "/")
 	for i, part := range parts {
+		// Start at the top and recurse
+		currentDir := filepath.Join(parts[:i]...)
+		nameType := nametransform.NameType(part)
+		dirIV := deriveDirIV(currentDir)
 		var transformedPart string
-		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
+		if nameType == nametransform.LongNameNone {
+			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
+				}
+				return "", err
+			}
+		} else if nameType == nametransform.LongNameContent {
+			transformedPart, err = rfs.findLongnameParent(currentDir, dirIV, part)
+			if err != nil {
+				return "", err
 			}
-			return "", err
+		} else {
+			panic("longname bug, .name files should have been handled earlier")
 		}
 		transformedParts = append(transformedParts, transformedPart)
 	}