Plan 9 support

Since Plan 9 does not have symlinks, these problems do not occur.
Therefore, SecureJoinVFS and SecureJoin can map to filepath.Join.

Signed-off-by: Ronald G Minnich <[email protected]>

Author: rminnich

join.go

@@ -3,6 +3,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !plan9
+
 package securejoin
 
 import (

join_plan9.go

@@ -0,0 +1,19 @@
+// Copyright (C) 2014-2015 Docker Inc & Go Authors. All rights reserved.
+// Copyright (C) 2017-2025 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package securejoin
+
+import "path/filepath"
+
+// SecureJoin is equivalent to filepath.Join, as plan9 doesn't have symlinks.
+func SecureJoin(root, unsafePath string) (string, error) {
+	unsafePath = filepath.Join(string(filepath.Separator), unsafePath)
+	return filepath.Join(root, unsafePath), nil
+}
+
+// SecureJoinVFS is equivalent to filepath.Join, as plan9 doesn't have symlinks.
+func SecureJoinVFS(root, unsafePath string, _ VFS) (string, error) {
+	return SecureJoin(root, unsafePath)
+}

join_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !plan9
+
 package securejoin
 
 import (