source: openpam/trunk/bin/su/su.c @ 221

/*-
 * Copyright (c) 2002,2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by ThinkSec AS and
 * Network Associates Laboratories, the Security Research Division of
 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $P4: //depot/projects/openpam/bin/su/su.c#10 $
 */

#include <sys/param.h>
#include <sys/wait.h>

#include <err.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#include <security/pam_appl.h>
#include <security/openpam.h>   /* for openpam_ttyconv() */

extern char **environ;

static pam_handle_t *pamh;
static struct pam_conv pamc;

static void
usage(void)
{

        fprintf(stderr, "Usage: su [login [args]]\n");
        exit(1);
}

int
main(int argc, char *argv[])
{
        char hostname[MAXHOSTNAMELEN];
        const char *user, *tty;
        char **args, **pam_envlist, **pam_env;
        struct passwd *pwd;
        int o, pam_err, status;
        pid_t pid;

        while ((o = getopt(argc, argv, "h")) != -1)
                switch (o) {
                case 'h':
                default:
                        usage();
                }

        argc -= optind;
        argv += optind;

        if (argc > 0) {
                user = *argv;
                --argc;
                ++argv;
        } else {
                user = "root";
        }

        /* initialize PAM */
        pamc.conv = &openpam_ttyconv;
        pam_start("su", user, &pamc, &pamh);

        /* set some items */
        gethostname(hostname, sizeof(hostname));
        if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS)
                goto pamerr;
        user = getlogin();
        if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS)
                goto pamerr;
        tty = ttyname(STDERR_FILENO);
        if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS)
                goto pamerr;

        /* authenticate the applicant */
        if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS)
                goto pamerr;
        if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD)
                pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
        if (pam_err != PAM_SUCCESS)
                goto pamerr;

        /* establish the requested credentials */
        if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
                goto pamerr;

        /* authentication succeeded; open a session */
        if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS)
                goto pamerr;

        /* get mapped user name; PAM may have changed it */
        pam_err = pam_get_item(pamh, PAM_USER, (const void **)&user);
        if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user)) == NULL)
                goto pamerr;

        /* export PAM environment */
        if ((pam_envlist = pam_getenvlist(pamh)) != NULL) {
                for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
                        putenv(*pam_env);
                        free(*pam_env);
                }
                free(pam_envlist);
        }

        /* build argument list */
        if ((args = calloc(argc + 2, sizeof *args)) == NULL) {
                warn("calloc()");
                goto err;
        }
        *args = pwd->pw_shell;
        memcpy(args + 1, argv, argc * sizeof *args);

        /* fork and exec */
        switch ((pid = fork())) {
        case -1:
                warn("fork()");
                goto err;
        case 0:
                /* child: give up privs and start a shell */

                /* set uid and groups */
                if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
                        warn("initgroups()");
                        _exit(1);
                }
                if (setgid(pwd->pw_gid) == -1) {
                        warn("setgid()");
                        _exit(1);
                }
                if (setuid(pwd->pw_uid) == -1) {
                        warn("setuid()");
                        _exit(1);
                }
                execve(*args, args, environ);
                warn("execve()");
                _exit(1);
        default:
                /* parent: wait for child to exit */
                waitpid(pid, &status, 0);

                /* close the session and release PAM resources */
                pam_err = pam_close_session(pamh, 0);
                pam_end(pamh, pam_err);

                exit(WEXITSTATUS(status));
        }

pamerr:
        fprintf(stderr, "Sorry\n");
err:
        pam_end(pamh, pam_err);
        exit(1);
}