src/syscall/creds_test.go

// Copyright 2012 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build linux

package syscall_test

import (
	"bytes"
	"net"
	"os"
	"syscall"
	"testing"
)

// TestSCMCredentials tests the sending and receiving of credentials
// (PID, UID, GID) in an ancillary message between two UNIX
// sockets. The SO_PASSCRED socket option is enabled on the sending
// socket for this to work.
func TestSCMCredentials(t *testing.T) {
	fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
	if err != nil {
		t.Fatalf("Socketpair: %v", err)
	}
	defer syscall.Close(fds[0])
	defer syscall.Close(fds[1])

	err = syscall.SetsockoptInt(fds[0], syscall.SOL_SOCKET, syscall.SO_PASSCRED, 1)
	if err != nil {
		t.Fatalf("SetsockoptInt: %v", err)
	}

	srvFile := os.NewFile(uintptr(fds[0]), "server")
	defer srvFile.Close()
	srv, err := net.FileConn(srvFile)
	if err != nil {
		t.Errorf("FileConn: %v", err)
		return
	}
	defer srv.Close()

	cliFile := os.NewFile(uintptr(fds[1]), "client")
	defer cliFile.Close()
	cli, err := net.FileConn(cliFile)
	if err != nil {
		t.Errorf("FileConn: %v", err)
		return
	}
	defer cli.Close()

	var ucred syscall.Ucred
	if os.Getuid() != 0 {
		ucred.Pid = int32(os.Getpid())
		ucred.Uid = 0
		ucred.Gid = 0
		oob := syscall.UnixCredentials(&ucred)
		_, _, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
		if err.(*net.OpError).Err != syscall.EPERM {
			t.Fatalf("WriteMsgUnix failed with %v, want EPERM", err)
		}
	}

	ucred.Pid = int32(os.Getpid())
	ucred.Uid = uint32(os.Getuid())
	ucred.Gid = uint32(os.Getgid())
	oob := syscall.UnixCredentials(&ucred)

	// this is going to send a dummy byte
	n, oobn, err := cli.(*net.UnixConn).WriteMsgUnix(nil, oob, nil)
	if err != nil {
		t.Fatalf("WriteMsgUnix: %v", err)
	}
	if n != 0 {
		t.Fatalf("WriteMsgUnix n = %d, want 0", n)
	}
	if oobn != len(oob) {
		t.Fatalf("WriteMsgUnix oobn = %d, want %d", oobn, len(oob))
	}

	oob2 := make([]byte, 10*len(oob))
	n, oobn2, flags, _, err := srv.(*net.UnixConn).ReadMsgUnix(nil, oob2)
	if err != nil {
		t.Fatalf("ReadMsgUnix: %v", err)
	}
	if flags != 0 {
		t.Fatalf("ReadMsgUnix flags = 0x%x, want 0", flags)
	}
	if n != 1 {
		t.Fatalf("ReadMsgUnix n = %d, want 1 (dummy byte)", n)
	}
	if oobn2 != oobn {
		// without SO_PASSCRED set on the socket, ReadMsgUnix will
		// return zero oob bytes
		t.Fatalf("ReadMsgUnix oobn = %d, want %d", oobn2, oobn)
	}
	oob2 = oob2[:oobn2]
	if !bytes.Equal(oob, oob2) {
		t.Fatal("ReadMsgUnix oob bytes don't match")
	}

	scm, err := syscall.ParseSocketControlMessage(oob2)
	if err != nil {
		t.Fatalf("ParseSocketControlMessage: %v", err)
	}
	newUcred, err := syscall.ParseUnixCredentials(&scm[0])
	if err != nil {
		t.Fatalf("ParseUnixCredentials: %v", err)
	}
	if *newUcred != ucred {
		t.Fatalf("ParseUnixCredentials = %+v, want %+v", newUcred, ucred)
	}
}