1 /* $NetBSD: su.c,v 1.8 2023/06/30 21:46:20 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
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
57 extern char **environ;
58
59 static pam_handle_t *pamh;
60 static struct pam_conv pamc;
61
62 static void
usage(void)63 usage(void)
64 {
65
66 fprintf(stderr, "usage: su [login [args]]\n");
67 exit(1);
68 }
69
70 int
main(int argc,char * argv[])71 main(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
186 pamerr:
187 fprintf(stderr, "Sorry\n");
188 err:
189 pam_end(pamh, pam_err);
190 exit(1);
191 }
192