From ef089c9f804556c8b7208991a482360637aa63bd Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher <jakobunt@gmail.com>
Date: Tue, 3 Jan 2017 17:46:11 +0100
Subject: [PATCH] reverse: factor out rDecryptName

This prepares the code for the introduction of a path cache.
---
 internal/fusefrontend_reverse/rpath.go | 72 ++++++++++++++------------
 1 file changed, 40 insertions(+), 32 deletions(-)

diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
index edffc1e..af49776 100644
--- a/internal/fusefrontend_reverse/rpath.go
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -44,46 +44,54 @@ func (rfs *ReverseFS) abs(relPath string, err error) (string, error) {
 	return filepath.Join(rfs.args.Cipherdir, relPath), nil
 }
 
+func (rfs *ReverseFS) 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.EINVAL {
+				return "", syscall.ENOENT
+			}
+			return "", err
+		}
+	} else if nameType == nametransform.LongNameContent {
+		pName, err = rfs.findLongnameParent(pDir, dirIV, cName)
+		if err != nil {
+			return "", err
+		}
+	} else {
+		// It makes no sense to decrypt a ".name" file. This is a virtual file
+		// that has no represantation in the plaintext filesystem. ".name"
+		// files should have already been handled in virtualfile.go.
+		tlog.Warn.Printf("decryptPath: tried to decrypt %q!? Returning EINVAL.", cName)
+		return "", syscall.EINVAL
+	}
+	return pName, nil
+}
+
 func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
 	if rfs.args.PlaintextNames || relPath == "" {
 		return relPath, nil
 	}
-	var err error
-	var transformedParts []string
 	parts := strings.Split(relPath, "/")
-	for i, part := range parts {
+	var transformedParts []string
+	for i := range parts {
 		// Start at the top and recurse
 		currentCipherDir := filepath.Join(parts[:i]...)
-		nameType := nametransform.NameType(part)
+		currentPlainDir := filepath.Join(transformedParts[:i]...)
 		dirIV := derivePathIV(currentCipherDir, ivPurposeDirIV)
-		var transformedPart string
-		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
-				}
-				// 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.EINVAL {
-					return "", syscall.ENOENT
-				}
-				return "", err
-			}
-		} else if nameType == nametransform.LongNameContent {
-			currentPlainDir := filepath.Join(transformedParts[:i]...)
-			transformedPart, err = rfs.findLongnameParent(currentPlainDir, dirIV, part)
-			if err != nil {
-				return "", err
-			}
-		} else {
-			// It makes no sense to decrypt a ".name" file
-			tlog.Warn.Printf("decryptPath: tried to decrypt %q!? Returning EINVAL.", part)
-			return "", syscall.EINVAL
+		transformedPart, err := rfs.rDecryptName(parts[i], dirIV, currentPlainDir)
+		if err != nil {
+			return "", err
 		}
 		transformedParts = append(transformedParts, transformedPart)
 	}