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
49 static const char *
get_username(void)50 get_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
71 int
main(int argc,char * argv[])72 main(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