tailscale/atomicfile/atomicfile_test.go

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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build !js && !windows
package atomicfile
import (
"net"
"os"
"path/filepath"
"runtime"
"strings"
"testing"
)
func TestDoesNotOverwriteIrregularFiles(t *testing.T) {
// Per tailscale/tailscale#7658 as one example, almost any imagined use of
// atomicfile.Write should likely not attempt to overwrite an irregular file
// such as a device node, socket, or named pipe.
const filename = "TestDoesNotOverwriteIrregularFiles"
var path string
// macOS private temp does not allow unix socket creation, but /tmp does.
if runtime.GOOS == "darwin" {
path = filepath.Join("/tmp", filename)
t.Cleanup(func() { os.Remove(path) })
} else {
path = filepath.Join(t.TempDir(), filename)
}
// The least troublesome thing to make that is not a file is a unix socket.
// Making a null device sadly requires root.
l, err := net.ListenUnix("unix", &net.UnixAddr{Name: path, Net: "unix"})
if err != nil {
t.Fatal(err)
}
defer l.Close()
err = WriteFile(path, []byte("hello"), 0644)
if err == nil {
t.Fatal("expected error, got nil")
}
if !strings.Contains(err.Error(), "is not a regular file") {
t.Fatalf("unexpected error: %v", err)
}
}