su.c revision 1.5 
1<<<<<<< su.c
2/*	$NetBSD: su.c,v 1.5 2014/10/24 18:17:56 christos Exp $	*/
3
4=======
5>>>>>>> 1.1.1.4
6/*-
7 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
8 * Copyright (c) 2004-2011 Dag-Erling Sm��rgrav
9 * All rights reserved.
10 *
11 * This software was developed for the FreeBSD Project by ThinkSec AS and
12 * Network Associates Laboratories, the Security Research Division of
13 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
14 * ("CBOSS"), as part of the DARPA CHATS research program.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 *    notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 *    notice, this list of conditions and the following disclaimer in the
23 *    documentation and/or other materials provided with the distribution.
24 * 3. The name of the author may not be used to endorse or promote
25 *    products derived from this software without specific prior written
26 *    permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * Id: su.c 648 2013-03-05 17:54:27Z des
41 */
42
43#ifdef HAVE_CONFIG_H
44# include "config.h"
45#endif
46
47#include <sys/param.h>
48#include <sys/wait.h>
49
50#include <err.h>
51#include <grp.h>
52#include <pwd.h>
53#include <stdio.h>
54#include <stdlib.h>
55#include <string.h>
56#include <syslog.h>
57#include <unistd.h>
58
59#include <security/pam_appl.h>
60#include <security/openpam.h>	/* for openpam_ttyconv() */
61
62extern char **environ;
63
64static pam_handle_t *pamh;
65static struct pam_conv pamc;
66
67static void
68usage(void)
69{
70
71	fprintf(stderr, "usage: su [login [args]]\n");
72	exit(1);
73}
74
75int
76main(int argc, char *argv[])
77{
78	char hostname[MAXHOSTNAMELEN];
79	const char *user, *tty;
80	const void *item;
81	char **args, **pam_envlist, **pam_env;
82	struct passwd *pwd;
83	int o, pam_err, status;
84	pid_t pid;
85
86	while ((o = getopt(argc, argv, "")) != -1)
87		switch (o) {
88		default:
89			usage();
90		}
91
92	argc -= optind;
93	argv += optind;
94
95	if (argc > 0) {
96		user = *argv;
97		--argc;
98		++argv;
99	} else {
100		user = "root";
101	}
102
103	/* initialize PAM */
104	pamc.conv = &openpam_ttyconv;
105	pam_start("su", user, &pamc, &pamh);
106
107	/* set some items */
108	gethostname(hostname, sizeof(hostname));
109	if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS)
110		goto pamerr;
111	user = getlogin();
112	if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS)
113		goto pamerr;
114	tty = ttyname(STDERR_FILENO);
115	if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS)
116		goto pamerr;
117
118	/* authenticate the applicant */
119	if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS)
120		goto pamerr;
121	if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD)
122		pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
123	if (pam_err != PAM_SUCCESS)
124		goto pamerr;
125
126	/* establish the requested credentials */
127	if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
128		goto pamerr;
129
130	/* authentication succeeded; open a session */
131	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
132		goto pamerr;
133
134	/* get mapped user name; PAM may have changed it */
135	pam_err = pam_get_item(pamh, PAM_USER, &item);
136	if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user = item)) == NULL)
137		goto pamerr;
138
139	/* export PAM environment */
140	if ((pam_envlist = pam_getenvlist(pamh)) != NULL) {
141		for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
142			putenv(*pam_env);
143			free(*pam_env);
144		}
145		free(pam_envlist);
146	}
147
148	/* build argument list */
149	if ((args = calloc(argc + 2, sizeof *args)) == NULL) {
150		warn("calloc()");
151		goto err;
152	}
153	*args = pwd->pw_shell;
154	memcpy(args + 1, argv, argc * sizeof *args);
155
156	/* fork and exec */
157	switch ((pid = fork())) {
158	case -1:
159		warn("fork()");
160		goto err;
161	case 0:
162		/* child: give up privs and start a shell */
163
164		/* set uid and groups */
165		if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
166			warn("initgroups()");
167			_exit(1);
168		}
169		if (setgid(pwd->pw_gid) == -1) {
170			warn("setgid()");
171			_exit(1);
172		}
173		if (setuid(pwd->pw_uid) == -1) {
174			warn("setuid()");
175			_exit(1);
176		}
177		execve(*args, args, environ);
178		warn("execve()");
179		_exit(1);
180	default:
181		/* parent: wait for child to exit */
182		waitpid(pid, &status, 0);
183
184		/* close the session and release PAM resources */
185		pam_err = pam_close_session(pamh, 0);
186		pam_end(pamh, pam_err);
187
188		exit(WEXITSTATUS(status));
189	}
190
191pamerr:
192	fprintf(stderr, "Sorry\n");
193err:
194	pam_end(pamh, pam_err);
195	exit(1);
196}
197