From b883dd10a62eb8d7ddf589e2878d8e0f65a90e83 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sun, 25 Sep 2016 18:01:24 +0200
Subject: reverse: add symlink encryption and Readlink support

---
 internal/fusefrontend_reverse/rfs.go   | 21 +++++++++++++++++++++
 internal/fusefrontend_reverse/rpath.go |  6 ++++++
 2 files changed, 27 insertions(+)

(limited to 'internal/fusefrontend_reverse')

diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go
index 6089d41..cfe23b6 100644
--- a/internal/fusefrontend_reverse/rfs.go
+++ b/internal/fusefrontend_reverse/rfs.go
@@ -1,6 +1,7 @@
 package fusefrontend_reverse
 
 import (
+	"encoding/base64"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -275,3 +276,23 @@ func (rfs *reverseFS) OpenDir(cipherPath string, context *fuse.Context) ([]fuse.
 func (rfs *reverseFS) StatFs(name string) *fuse.StatfsOut {
 	return rfs.loopbackfs.StatFs(name)
 }
+
+// Readlink - FUSE call
+func (rfs *reverseFS) Readlink(cipherPath string, context *fuse.Context) (string, fuse.Status) {
+	absPath, err := rfs.abs(rfs.decryptPath(cipherPath))
+	if err != nil {
+		return "", fuse.ToStatus(err)
+	}
+	plainTarget, err := os.Readlink(absPath)
+	if err != nil {
+		return "", fuse.ToStatus(err)
+	}
+	if rfs.args.PlaintextNames {
+		return plainTarget, fuse.OK
+	}
+	nonce := derivePathIV(cipherPath)
+	// Symlinks are encrypted like file contents and base64-encoded
+	cBinTarget := rfs.contentEnc.EncryptBlock([]byte(plainTarget), 0, nil, contentenc.ExternalNonce, nonce)
+	cTarget := base64.URLEncoding.EncodeToString(cBinTarget)
+	return cTarget, fuse.OK
+}
diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
index c603cad..6d418e0 100644
--- a/internal/fusefrontend_reverse/rpath.go
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -47,6 +47,12 @@ func (rfs *reverseFS) decryptPath(relPath string) (string, error) {
 				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 {
-- 
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