1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2009 Ed Schouten <ed@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30#include <pwd.h>
31#include <unistd.h>
32#include <stdlib.h>
33#include <string.h>
34#include <sysexits.h>
35#include <ulog.h>
36
37/*
38 * This setuid helper utility writes user login records to disk.
39 * Unprivileged processes are not capable of writing records to utmpx,
40 * but we do want to allow this for pseudo-terminals.  Because a file
41 * descriptor to a pseudo-terminal master device can only be obtained by
42 * processes using the pseudo-terminal, we expect such a descriptor on
43 * stdin.
44 *
45 * It uses the real user ID of the calling process to determine the
46 * username.  It does allow users to log arbitrary hostnames.
47 */
48
49static const char *
50get_username(void)
51{
52	const struct passwd *pw;
53	const char *login;
54	uid_t uid;
55
56	/*
57	 * Attempt to determine the username corresponding to this login
58	 * session.  First, validate the results of getlogin() against
59	 * the password database.  If getlogin() returns invalid data,
60	 * return an arbitrary username corresponding to this uid.
61	 */
62	uid = getuid();
63	if ((login = getlogin()) != NULL && (pw = getpwnam(login)) != NULL &&
64	    pw->pw_uid == uid)
65		return (login);
66	if ((pw = getpwuid(uid)) != NULL)
67		return (pw->pw_name);
68	return (NULL);
69}
70
71int
72main(int argc, char *argv[])
73{
74	const char *line, *user, *host;
75
76	/* Device line name. */
77	if ((line = ptsname(STDIN_FILENO)) == NULL)
78		return (EX_USAGE);
79
80	if ((argc == 2 || argc == 3) && strcmp(argv[1], "login") == 0) {
81		/* Username. */
82		user = get_username();
83		if (user == NULL)
84			return (EX_OSERR);
85
86		/* Hostname. */
87		host = argc == 3 ? argv[2] : NULL;
88
89		ulog_login(line, user, host);
90		return (EX_OK);
91	} else if (argc == 2 && strcmp(argv[1], "logout") == 0) {
92		ulog_logout(line);
93		return (EX_OK);
94	}
95
96	return (EX_USAGE);
97}
98