1/*	$NetBSD: su.c,v 1.2 2011/12/25 22:27:55 christos Exp $	*/
2
3/*-
4 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
5 * Copyright (c) 2004-2011 Dag-Erling Smørgrav
6 * All rights reserved.
7 *
8 * This software was developed for the FreeBSD Project by ThinkSec AS and
9 * Network Associates Laboratories, the Security Research Division of
10 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
11 * ("CBOSS"), as part of the DARPA CHATS research program.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 *    notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 *    notice, this list of conditions and the following disclaimer in the
20 *    documentation and/or other materials provided with the distribution.
21 * 3. The name of the author may not be used to endorse or promote
22 *    products derived from this software without specific prior written
23 *    permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * SUCH DAMAGE.
36 *
37 * Id: su.c 458 2011-11-02 13:10:25Z des
38 */
39
40#ifdef HAVE_CONFIG_H
41# include "config.h"
42#endif
43
44#include <sys/param.h>
45#include <sys/wait.h>
46
47#include <err.h>
48#include <grp.h>
49#include <pwd.h>
50#include <stdio.h>
51#include <stdlib.h>
52#include <string.h>
53#include <syslog.h>
54#include <unistd.h>
55
56#include <security/pam_appl.h>
57#include <security/openpam.h>	/* for openpam_ttyconv() */
58
59extern char **environ;
60
61static pam_handle_t *pamh;
62static struct pam_conv pamc;
63
64static void
65usage(void)
66{
67
68	fprintf(stderr, "usage: su [login [args]]\n");
69	exit(1);
70}
71
72int
73main(int argc, char *argv[])
74{
75	char hostname[MAXHOSTNAMELEN];
76	const char *user, *tty;
77	const void *item;
78	char **args, **pam_envlist, **pam_env;
79	struct passwd *pwd;
80	int o, pam_err, status;
81	pid_t pid;
82
83	while ((o = getopt(argc, argv, "")) != -1)
84		switch (o) {
85		default:
86			usage();
87		}
88
89	argc -= optind;
90	argv += optind;
91
92	if (argc > 0) {
93		user = *argv;
94		--argc;
95		++argv;
96	} else {
97		user = "root";
98	}
99
100	/* initialize PAM */
101	pamc.conv = &openpam_ttyconv;
102	pam_start("su", user, &pamc, &pamh);
103
104	/* set some items */
105	gethostname(hostname, sizeof(hostname));
106	if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS)
107		goto pamerr;
108	user = getlogin();
109	if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS)
110		goto pamerr;
111	tty = ttyname(STDERR_FILENO);
112	if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS)
113		goto pamerr;
114
115	/* authenticate the applicant */
116	if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS)
117		goto pamerr;
118	if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD)
119		pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
120	if (pam_err != PAM_SUCCESS)
121		goto pamerr;
122
123	/* establish the requested credentials */
124	if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
125		goto pamerr;
126
127	/* authentication succeeded; open a session */
128	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
129		goto pamerr;
130
131	/* get mapped user name; PAM may have changed it */
132	pam_err = pam_get_item(pamh, PAM_USER, &item);
133	if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user = item)) == NULL)
134		goto pamerr;
135
136	/* export PAM environment */
137	if ((pam_envlist = pam_getenvlist(pamh)) != NULL) {
138		for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
139			putenv(*pam_env);
140			free(*pam_env);
141		}
142		free(pam_envlist);
143	}
144
145	/* build argument list */
146	if ((args = calloc(argc + 2, sizeof *args)) == NULL) {
147		warn("calloc()");
148		goto err;
149	}
150	*args = pwd->pw_shell;
151	memcpy(args + 1, argv, argc * sizeof *args);
152
153	/* fork and exec */
154	switch ((pid = fork())) {
155	case -1:
156		warn("fork()");
157		goto err;
158	case 0:
159		/* child: give up privs and start a shell */
160
161		/* set uid and groups */
162		if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
163			warn("initgroups()");
164			_exit(1);
165		}
166		if (setgid(pwd->pw_gid) == -1) {
167			warn("setgid()");
168			_exit(1);
169		}
170		if (setuid(pwd->pw_uid) == -1) {
171			warn("setuid()");
172			_exit(1);
173		}
174		execve(*args, args, environ);
175		warn("execve()");
176		_exit(1);
177	default:
178		/* parent: wait for child to exit */
179		waitpid(pid, &status, 0);
180
181		/* close the session and release PAM resources */
182		pam_err = pam_close_session(pamh, 0);
183		pam_end(pamh, pam_err);
184
185		exit(WEXITSTATUS(status));
186	}
187
188pamerr:
189	fprintf(stderr, "Sorry\n");
190err:
191	pam_end(pamh, pam_err);
192	exit(1);
193}
194