xref: /freebsd/contrib/openpam/bin/su/su.c (revision 7aa383846770374466b1dcb2cefd71bde9acf463)
1 /*-
2  * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
3  * Copyright (c) 2004-2007 Dag-Erling Smørgrav
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 408 2007-12-21 11:36:24Z des $
36  */
37 
38 #include <sys/param.h>
39 #include <sys/wait.h>
40 
41 #include <err.h>
42 #include <grp.h>
43 #include <pwd.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <syslog.h>
48 #include <unistd.h>
49 
50 #include <security/pam_appl.h>
51 #include <security/openpam.h>	/* for openpam_ttyconv() */
52 
53 extern char **environ;
54 
55 static pam_handle_t *pamh;
56 static struct pam_conv pamc;
57 
58 static void
59 usage(void)
60 {
61 
62 	fprintf(stderr, "Usage: su [login [args]]\n");
63 	exit(1);
64 }
65 
66 int
67 main(int argc, char *argv[])
68 {
69 	char hostname[MAXHOSTNAMELEN];
70 	const char *user, *tty;
71 	const void *item;
72 	char **args, **pam_envlist, **pam_env;
73 	struct passwd *pwd;
74 	int o, pam_err, status;
75 	pid_t pid;
76 
77 	while ((o = getopt(argc, argv, "h")) != -1)
78 		switch (o) {
79 		case 'h':
80 		default:
81 			usage();
82 		}
83 
84 	argc -= optind;
85 	argv += optind;
86 
87 	if (argc > 0) {
88 		user = *argv;
89 		--argc;
90 		++argv;
91 	} else {
92 		user = "root";
93 	}
94 
95 	/* initialize PAM */
96 	pamc.conv = &openpam_ttyconv;
97 	pam_start("su", user, &pamc, &pamh);
98 
99 	/* set some items */
100 	gethostname(hostname, sizeof(hostname));
101 	if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS)
102 		goto pamerr;
103 	user = getlogin();
104 	if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS)
105 		goto pamerr;
106 	tty = ttyname(STDERR_FILENO);
107 	if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS)
108 		goto pamerr;
109 
110 	/* authenticate the applicant */
111 	if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS)
112 		goto pamerr;
113 	if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD)
114 		pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
115 	if (pam_err != PAM_SUCCESS)
116 		goto pamerr;
117 
118 	/* establish the requested credentials */
119 	if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
120 		goto pamerr;
121 
122 	/* authentication succeeded; open a session */
123 	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
124 		goto pamerr;
125 
126 	/* get mapped user name; PAM may have changed it */
127 	pam_err = pam_get_item(pamh, PAM_USER, &item);
128 	if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user = item)) == NULL)
129 		goto pamerr;
130 
131 	/* export PAM environment */
132 	if ((pam_envlist = pam_getenvlist(pamh)) != NULL) {
133 		for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
134 			putenv(*pam_env);
135 			free(*pam_env);
136 		}
137 		free(pam_envlist);
138 	}
139 
140 	/* build argument list */
141 	if ((args = calloc(argc + 2, sizeof *args)) == NULL) {
142 		warn("calloc()");
143 		goto err;
144 	}
145 	*args = pwd->pw_shell;
146 	memcpy(args + 1, argv, argc * sizeof *args);
147 
148 	/* fork and exec */
149 	switch ((pid = fork())) {
150 	case -1:
151 		warn("fork()");
152 		goto err;
153 	case 0:
154 		/* child: give up privs and start a shell */
155 
156 		/* set uid and groups */
157 		if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
158 			warn("initgroups()");
159 			_exit(1);
160 		}
161 		if (setgid(pwd->pw_gid) == -1) {
162 			warn("setgid()");
163 			_exit(1);
164 		}
165 		if (setuid(pwd->pw_uid) == -1) {
166 			warn("setuid()");
167 			_exit(1);
168 		}
169 		execve(*args, args, environ);
170 		warn("execve()");
171 		_exit(1);
172 	default:
173 		/* parent: wait for child to exit */
174 		waitpid(pid, &status, 0);
175 
176 		/* close the session and release PAM resources */
177 		pam_err = pam_close_session(pamh, 0);
178 		pam_end(pamh, pam_err);
179 
180 		exit(WEXITSTATUS(status));
181 	}
182 
183 pamerr:
184 	fprintf(stderr, "Sorry\n");
185 err:
186 	pam_end(pamh, pam_err);
187 	exit(1);
188 }
189