dist/openpam/bin/su/su.c

   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,v 1.1.1.2 2008/01/27 00:54:54 christos Exp $
  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 }