1// Copyright 2024 The Go Authors. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5// Socket control messages
 6
 7package unix
 8
 9import "unsafe"
10
11// UnixCredentials encodes credentials into a socket control message
12// for sending to another process. This can be used for
13// authentication.
14func UnixCredentials(ucred *Ucred) []byte {
15	b := make([]byte, CmsgSpace(SizeofUcred))
16	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
17	h.Level = SOL_SOCKET
18	h.Type = SCM_CREDENTIALS
19	h.SetLen(CmsgLen(SizeofUcred))
20	*(*Ucred)(h.data(0)) = *ucred
21	return b
22}
23
24// ParseUnixCredentials decodes a socket control message that contains
25// credentials in a Ucred structure. To receive such a message, the
26// SO_PASSCRED option must be enabled on the socket.
27func ParseUnixCredentials(m *SocketControlMessage) (*Ucred, error) {
28	if m.Header.Level != SOL_SOCKET {
29		return nil, EINVAL
30	}
31	if m.Header.Type != SCM_CREDENTIALS {
32		return nil, EINVAL
33	}
34	ucred := *(*Ucred)(unsafe.Pointer(&m.Data[0]))
35	return &ucred, nil
36}
37
38// PktInfo4 encodes Inet4Pktinfo into a socket control message of type IP_PKTINFO.
39func PktInfo4(info *Inet4Pktinfo) []byte {
40	b := make([]byte, CmsgSpace(SizeofInet4Pktinfo))
41	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
42	h.Level = SOL_IP
43	h.Type = IP_PKTINFO
44	h.SetLen(CmsgLen(SizeofInet4Pktinfo))
45	*(*Inet4Pktinfo)(h.data(0)) = *info
46	return b
47}
48
49// PktInfo6 encodes Inet6Pktinfo into a socket control message of type IPV6_PKTINFO.
50func PktInfo6(info *Inet6Pktinfo) []byte {
51	b := make([]byte, CmsgSpace(SizeofInet6Pktinfo))
52	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
53	h.Level = SOL_IPV6
54	h.Type = IPV6_PKTINFO
55	h.SetLen(CmsgLen(SizeofInet6Pktinfo))
56	*(*Inet6Pktinfo)(h.data(0)) = *info
57	return b
58}