Report correct symbolic link dentry sizes

Prior to this commit, gocryptfs's reverse mode did not report correct
directory entry sizes for symbolic links, where the dentry size needs to
be the same as the length of a string containing the target path.

This commit corrects this issue and adds a test case to verify the
correctness of the implementation.

This issue was discovered during the use of a strict file copying program
on a reverse-mounted gocryptfs file system.

1 files changed, 10 insertions, 0 deletions

diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go
index f9a2979..a3a3d3b 100644
--- a/internal/fusefrontend_reverse/rfs.go
+++ b/internal/fusefrontend_reverse/rfs.go
@@ -221,6 +221,16 @@ func (rfs *ReverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr
 	// Calculate encrypted file size
 	if a.IsRegular() {
 		a.Size = rfs.contentEnc.PlainSizeToCipherSize(a.Size)
+	} else if a.IsSymlink() {
+		var linkTarget string
+		var readlinkStatus fuse.Status
+
+		linkTarget, readlinkStatus = rfs.Readlink(relPath, context)
+		if !readlinkStatus.Ok() {
+			return nil, readlinkStatus
+		}
+
+		a.Size = uint64(len(linkTarget))
 	}
 	return a, fuse.OK
 }