su.c revision 294192 
1/*-
2 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
3 * Copyright (c) 2004-2011 Dag-Erling Sm��rgrav
4 * All rights reserved.
5 *
6 * This software was developed for the FreeBSD Project by ThinkSec AS and
7 * Network Associates Laboratories, the Security Research Division of
8 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
9 * ("CBOSS"), as part of the DARPA CHATS research program.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 * 3. The name of the author may not be used to endorse or promote
20 *    products derived from this software without specific prior written
21 *    permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * $Id: su.c 648 2013-03-05 17:54:27Z des $
36 */
37
38#ifdef HAVE_CONFIG_H
39# include "config.h"
40#endif
41
42#include <sys/param.h>
43#include <sys/wait.h>
44
45#include <err.h>
46#include <grp.h>
47#include <pwd.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51#include <syslog.h>
52#include <unistd.h>
53
54#include <security/pam_appl.h>
55#include <security/openpam.h>	/* for openpam_ttyconv() */
56
57extern char **environ;
58
59static pam_handle_t *pamh;
60static struct pam_conv pamc;
61
62static void
63usage(void)
64{
65
66	fprintf(stderr, "usage: su [login [args]]\n");
67	exit(1);
68}
69
70int
71main(int argc, char *argv[])
72{
73	char hostname[MAXHOSTNAMELEN];
74	const char *user, *tty;
75	const void *item;
76	char **args, **pam_envlist, **pam_env;
77	struct passwd *pwd;
78	int o, pam_err, status;
79	pid_t pid;
80
81	while ((o = getopt(argc, argv, "")) != -1)
82		switch (o) {
83		default:
84			usage();
85		}
86
87	argc -= optind;
88	argv += optind;
89
90	if (argc > 0) {
91		user = *argv;
92		--argc;
93		++argv;
94	} else {
95		user = "root";
96	}
97
98	/* initialize PAM */
99	pamc.conv = &openpam_ttyconv;
100	pam_start("su", user, &pamc, &pamh);
101
102	/* set some items */
103	gethostname(hostname, sizeof(hostname));
104	if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS)
105		goto pamerr;
106	user = getlogin();
107	if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS)
108		goto pamerr;
109	tty = ttyname(STDERR_FILENO);
110	if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS)
111		goto pamerr;
112
113	/* authenticate the applicant */
114	if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS)
115		goto pamerr;
116	if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD)
117		pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
118	if (pam_err != PAM_SUCCESS)
119		goto pamerr;
120
121	/* establish the requested credentials */
122	if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
123		goto pamerr;
124
125	/* authentication succeeded; open a session */
126	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
127		goto pamerr;
128
129	/* get mapped user name; PAM may have changed it */
130	pam_err = pam_get_item(pamh, PAM_USER, &item);
131	if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user = item)) == NULL)
132		goto pamerr;
133
134	/* export PAM environment */
135	if ((pam_envlist = pam_getenvlist(pamh)) != NULL) {
136		for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
137			putenv(*pam_env);
138			free(*pam_env);
139		}
140		free(pam_envlist);
141	}
142
143	/* build argument list */
144	if ((args = calloc(argc + 2, sizeof *args)) == NULL) {
145		warn("calloc()");
146		goto err;
147	}
148	*args = pwd->pw_shell;
149	memcpy(args + 1, argv, argc * sizeof *args);
150
151	/* fork and exec */
152	switch ((pid = fork())) {
153	case -1:
154		warn("fork()");
155		goto err;
156	case 0:
157		/* child: give up privs and start a shell */
158
159		/* set uid and groups */
160		if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
161			warn("initgroups()");
162			_exit(1);
163		}
164		if (setgid(pwd->pw_gid) == -1) {
165			warn("setgid()");
166			_exit(1);
167		}
168		if (setuid(pwd->pw_uid) == -1) {
169			warn("setuid()");
170			_exit(1);
171		}
172		execve(*args, args, environ);
173		warn("execve()");
174		_exit(1);
175	default:
176		/* parent: wait for child to exit */
177		waitpid(pid, &status, 0);
178
179		/* close the session and release PAM resources */
180		pam_err = pam_close_session(pamh, 0);
181		pam_end(pamh, pam_err);
182
183		exit(WEXITSTATUS(status));
184	}
185
186pamerr:
187	fprintf(stderr, "Sorry\n");
188err:
189	pam_end(pamh, pam_err);
190	exit(1);
191}
192