// Copyright 2011 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.

// Socket control messages

package unix

import "unsafe"

// UnixCredentials encodes credentials into a socket control message

// for sending to another process. This can be used for

// authentication.

func UnixCredentials(ucred *Ucred) []byte {

	b := make([]byte, CmsgSpace(SizeofUcred))

	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))

	h.Level = SOL_SOCKET

	h.Type = SCM_CREDENTIALS

	h.SetLen(CmsgLen(SizeofUcred))

	return b

}

// ParseUnixCredentials decodes a socket control message that contains

// credentials in a Ucred structure. To receive such a message, the

// SO_PASSCRED option must be enabled on the socket.

func ParseUnixCredentials(m *SocketControlMessage) (*Ucred, error) {

	if m.Header.Level != SOL_SOCKET {

		return nil, EINVAL

	}

	if m.Header.Type != SCM_CREDENTIALS {

		return nil, EINVAL

	}

	ucred := *(*Ucred)(unsafe.Pointer(&m.Data[0]))

	return &ucred, nil

}