From 04858ddd222bbf7156f33f99cfb293a9b1e15ec8 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Wed, 2 Jun 2021 14:21:30 +0200
Subject: nametransform: check name validity on encryption

xfstests generic/523 discovered that we allowed to set
xattrs with "/" in the name, but did not allow to read
them later.

With this change we do not allow to set them in the first
place.
---
 internal/nametransform/valid.go | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 internal/nametransform/valid.go

(limited to 'internal/nametransform/valid.go')

diff --git a/internal/nametransform/valid.go b/internal/nametransform/valid.go
new file mode 100644
index 0000000..b991074
--- /dev/null
+++ b/internal/nametransform/valid.go
@@ -0,0 +1,27 @@
+package nametransform
+
+import (
+	"fmt"
+	"strings"
+)
+
+// IsValidName checks if `name` is a valid name for a normal file
+// (does not contain null bytes or "/" etc...).
+func IsValidName(name string) error {
+	if name == "" {
+		return fmt.Errorf("empty input")
+	}
+	if len(name) > NameMax {
+		return fmt.Errorf("too long")
+	}
+	// A name can never contain a null byte or "/". Make sure we never return those
+	// to the kernel, even when we read a corrupted (or fuzzed) filesystem.
+	if strings.Contains(name, "\000") || strings.Contains(name, "/") {
+		return fmt.Errorf("contains forbidden bytes")
+	}
+	// The name should never be "." or "..".
+	if name == "." || name == ".." {
+		return fmt.Errorf(". and .. are forbidden names")
+	}
+	return nil
+}
-- 
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