ctlsock: sanitize paths before passing them to the backend

You used to be able to crash gocryptfs by passing "/foo"
of "foo/" to the ctlsock.

Fixes https://github.com/rfjakob/gocryptfs/issues/66

1 files changed, 20 insertions, 0 deletions

diff --git a/internal/ctlsock/sanitize.go b/internal/ctlsock/sanitize.go
new file mode 100644
index 0000000..5bc3706
--- /dev/null
+++ b/internal/ctlsock/sanitize.go
@@ -0,0 +1,20 @@
+package ctlsock
+
+import (
+	"path/filepath"
+)
+
+// SanitizePath adapts filepath.Clean for FUSE paths.
+// 1) It always returns a relative path
+// 2) It returns "" instead of "."
+// See the TestSanitizePath testcases for examples.
+func SanitizePath(path string) string {
+	clean := filepath.Clean(path)
+	if clean == "." || clean == "/" {
+		return ""
+	}
+	if clean[0] == '/' {
+		clean = clean[1:]
+	}
+	return clean
+}