/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2002, 2005 Networks Associates Technologies, Inc.
 * All rights reserved.
 *
 * Portions of this software were developed for the FreeBSD Project by
 * ThinkSec AS and NAI Labs, 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.
 *
 * 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.
 */
/*-
 * Copyright (c) 1988, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

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

#ifdef USE_BSM_AUDIT
#include <bsm/libbsm.h>
#include <bsm/audit_uevents.h>
#endif

#include <err.h>
#include <errno.h>
#include <grp.h>
#include <login_cap.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <stdarg.h>

#include <security/pam_appl.h>
#include <security/openpam.h>

#define PAM_END() do {                                                  \
        int local_ret;                                                  \
        if (pamh != NULL) {                                             \
                local_ret = pam_setcred(pamh, PAM_DELETE_CRED);         \
                if (local_ret != PAM_SUCCESS)                           \
                        syslog(LOG_ERR, "pam_setcred: %s",              \
                                pam_strerror(pamh, local_ret));         \
                if (asthem) {                                           \
                        local_ret = pam_close_session(pamh, 0);         \
                        if (local_ret != PAM_SUCCESS)                   \
                                syslog(LOG_ERR, "pam_close_session: %s",\
                                        pam_strerror(pamh, local_ret)); \
                }                                                       \
                local_ret = pam_end(pamh, local_ret);                   \
                if (local_ret != PAM_SUCCESS)                           \
                        syslog(LOG_ERR, "pam_end: %s",                  \
                                pam_strerror(pamh, local_ret));         \
        }                                                               \
} while (0)


#define PAM_SET_ITEM(what, item) do {                                   \
        int local_ret;                                                  \
        local_ret = pam_set_item(pamh, what, item);                     \
        if (local_ret != PAM_SUCCESS) {                                 \
                syslog(LOG_ERR, "pam_set_item(" #what "): %s",          \
                        pam_strerror(pamh, local_ret));                 \
                errx(1, "pam_set_item(" #what "): %s",                  \
                        pam_strerror(pamh, local_ret));                 \
                /* NOTREACHED */                                        \
        }                                                               \
} while (0)

enum tristate { UNSET, YES, NO };

static pam_handle_t *pamh = NULL;
static char     **environ_pam;

static char     *ontty(void);
static int      chshell(const char *);
static void     usage(void) __dead2;
static void     export_pam_environment(void);
static int      ok_to_export(const char *);

extern char     **environ;

int
main(int argc, char *argv[])
{
        static char     *cleanenv;
        struct passwd   *pwd = NULL;
        struct pam_conv conv = { openpam_ttyconv, NULL };
        enum tristate   iscsh;
        login_cap_t     *lc;
        union {
                const char      **a;
                char            * const *b;
        }               np;
        uid_t           ruid;
        pid_t           child_pid, child_pgrp, pid;
        int             asme, ch, asthem, fastlogin, prio, i, retcode,
                        statusp, setmaclabel;
        u_int           setwhat;
        char            *username, *class, shellbuf[MAXPATHLEN];
        const char      *p, *user, *shell, *mytty, **nargv;
        const void      *v;
        struct sigaction sa, sa_int, sa_quit, sa_pipe;
        int temp, fds[2];
#ifdef USE_BSM_AUDIT
        const char      *aerr;
        au_id_t          auid;
#endif

        p = shell = class = cleanenv = NULL;
        asme = asthem = fastlogin = statusp = 0;
        user = "root";
        iscsh = UNSET;
        setmaclabel = 0;

        while ((ch = getopt(argc, argv, "-flmsc:")) != -1)
                switch ((char)ch) {
                case 'f':
                        fastlogin = 1;
                        break;
                case '-':
                case 'l':
                        asme = 0;
                        asthem = 1;
                        break;
                case 'm':
                        asme = 1;
                        asthem = 0;
                        break;
                case 's':
                        setmaclabel = 1;
                        break;
                case 'c':
                        class = optarg;
                        break;
                case '?':
                default:
                        usage();
                /* NOTREACHED */
                }

        if (optind < argc)
                user = argv[optind++];

        if (user == NULL)
                usage();
        /* NOTREACHED */

        /*
         * Try to provide more helpful debugging output if su(1) is running
         * non-setuid, or was run from a file system not mounted setuid.
         */
        if (geteuid() != 0)
                errx(1, "not running setuid");

#ifdef USE_BSM_AUDIT
        if (getauid(&auid) < 0 && errno != ENOSYS) {
                syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno));
                errx(1, "Permission denied");
        }
#endif
        if (strlen(user) > MAXLOGNAME - 1) {
#ifdef USE_BSM_AUDIT
                if (audit_submit(AUE_su, auid,
                    EPERM, 1, "username too long: '%s'", user))
                        errx(1, "Permission denied");
#endif
                errx(1, "username too long");
        }

        nargv = malloc(sizeof(char *) * (size_t)(argc + 4));
        if (nargv == NULL)
                errx(1, "malloc failure");

        nargv[argc + 3] = NULL;
        for (i = argc; i >= optind; i--)
                nargv[i + 3] = argv[i];
        np.a = &nargv[i + 3];

        argv += optind;

        errno = 0;
        prio = getpriority(PRIO_PROCESS, 0);
        if (errno)
                prio = 0;

        setpriority(PRIO_PROCESS, 0, -2);
        openlog("su", LOG_CONS, LOG_AUTH);

        /* get current login name, real uid and shell */
        ruid = getuid();
        username = getlogin();
        if (username != NULL)
                pwd = getpwnam(username);
        if (pwd == NULL || pwd->pw_uid != ruid)
                pwd = getpwuid(ruid);
        if (pwd == NULL) {
#ifdef USE_BSM_AUDIT
                if (audit_submit(AUE_su, auid, EPERM, 1,
                    "unable to determine invoking subject: '%s'", username))
                        errx(1, "Permission denied");
#endif
                errx(1, "who are you?");
        }

        username = strdup(pwd->pw_name);
        if (username == NULL)
                err(1, "strdup failure");

        if (asme) {
                if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
                        /* must copy - pwd memory is recycled */
                        strlcpy(shellbuf, pwd->pw_shell,
                            sizeof(shellbuf));
                        shell = shellbuf;
                }
                else {
                        shell = _PATH_BSHELL;
                        iscsh = NO;
                }
        }

        /* Do the whole PAM startup thing */
        retcode = pam_start("su", user, &conv, &pamh);
        if (retcode != PAM_SUCCESS) {
                syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode));
                errx(1, "pam_start: %s", pam_strerror(pamh, retcode));
        }

        PAM_SET_ITEM(PAM_RUSER, username);

        mytty = ttyname(STDERR_FILENO);
        if (!mytty)
                mytty = "tty";
        PAM_SET_ITEM(PAM_TTY, mytty);

        retcode = pam_authenticate(pamh, 0);
        if (retcode != PAM_SUCCESS) {
#ifdef USE_BSM_AUDIT
                if (audit_submit(AUE_su, auid, EPERM, 1, "bad su %s to %s on %s",
                    username, user, mytty))
                        errx(1, "Permission denied");
#endif
                syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s",
                    username, user, mytty);
                errx(1, "Sorry");
        }
#ifdef USE_BSM_AUDIT
        if (audit_submit(AUE_su, auid, 0, 0, "successful authentication"))
                errx(1, "Permission denied");
#endif
        retcode = pam_get_item(pamh, PAM_USER, &v);
        if (retcode == PAM_SUCCESS)
                user = v;
        else
                syslog(LOG_ERR, "pam_get_item(PAM_USER): %s",
                    pam_strerror(pamh, retcode));
        pwd = getpwnam(user);
        if (pwd == NULL) {
#ifdef USE_BSM_AUDIT
                if (audit_submit(AUE_su, auid, EPERM, 1,
                    "unknown subject: %s", user))
                        errx(1, "Permission denied");
#endif
                errx(1, "unknown login: %s", user);
        }

        retcode = pam_acct_mgmt(pamh, 0);
        if (retcode == PAM_NEW_AUTHTOK_REQD) {
                retcode = pam_chauthtok(pamh,
                        PAM_CHANGE_EXPIRED_AUTHTOK);
                if (retcode != PAM_SUCCESS) {
#ifdef USE_BSM_AUDIT
                        aerr = pam_strerror(pamh, retcode);
                        if (aerr == NULL)
                                aerr = "Unknown PAM error";
                        if (audit_submit(AUE_su, auid, EPERM, 1,
                            "pam_chauthtok: %s", aerr))
                                errx(1, "Permission denied");
#endif
                        syslog(LOG_ERR, "pam_chauthtok: %s",
                            pam_strerror(pamh, retcode));
                        errx(1, "Sorry");
                }
        }
        if (retcode != PAM_SUCCESS) {
#ifdef USE_BSM_AUDIT
                if (audit_submit(AUE_su, auid, EPERM, 1, "pam_acct_mgmt: %s",
                    pam_strerror(pamh, retcode)))
                        errx(1, "Permission denied");
#endif
                syslog(LOG_ERR, "pam_acct_mgmt: %s",
                        pam_strerror(pamh, retcode));
                errx(1, "Sorry");
        }

        /* get target login information */
        if (class == NULL)
                lc = login_getpwclass(pwd);
        else {
                if (ruid != 0) {
#ifdef USE_BSM_AUDIT
                        if (audit_submit(AUE_su, auid, EPERM, 1,
                            "only root may use -c"))
                                errx(1, "Permission denied");
#endif
                        errx(1, "only root may use -c");
                }
                lc = login_getclass(class);
                if (lc == NULL)
                        err(1, "login_getclass");
                if (lc->lc_class == NULL || strcmp(class, lc->lc_class) != 0)
                        errx(1, "unknown class: %s", class);
        }

        /* if asme and non-standard target shell, must be root */
        if (asme) {
                if (ruid != 0 && !chshell(pwd->pw_shell))
                        errx(1, "permission denied (shell)");
        }
        else if (pwd->pw_shell && *pwd->pw_shell) {
                shell = pwd->pw_shell;
                iscsh = UNSET;
        }
        else {
                shell = _PATH_BSHELL;
                iscsh = NO;
        }

        /* if we're forking a csh, we want to slightly muck the args */
        if (iscsh == UNSET) {
                p = strrchr(shell, '/');
                if (p)
                        ++p;
                else
                        p = shell;
                iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES;
        }
        setpriority(PRIO_PROCESS, 0, prio);

        /*
         * PAM modules might add supplementary groups in pam_setcred(), so
         * initialize them first.
         */
        if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0)
                err(1, "setusercontext");

        retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
        if (retcode != PAM_SUCCESS) {
                syslog(LOG_ERR, "pam_setcred: %s",
                    pam_strerror(pamh, retcode));
                errx(1, "failed to establish credentials.");
        }
        if (asthem) {
                retcode = pam_open_session(pamh, 0);
                if (retcode != PAM_SUCCESS) {
                        syslog(LOG_ERR, "pam_open_session: %s",
                            pam_strerror(pamh, retcode));
                        errx(1, "failed to open session.");
                }
        }

        /*
         * We must fork() before setuid() because we need to call
         * pam_setcred(pamh, PAM_DELETE_CRED) as root.
         */
        sa.sa_flags = SA_RESTART;
        sa.sa_handler = SIG_IGN;
        sigemptyset(&sa.sa_mask);
        sigaction(SIGINT, &sa, &sa_int);
        sigaction(SIGQUIT, &sa, &sa_quit);
        sigaction(SIGPIPE, &sa, &sa_pipe);
        sa.sa_handler = SIG_DFL;
        sigaction(SIGTSTP, &sa, NULL);
        statusp = 1;
        if (pipe(fds) == -1) {
                PAM_END();
                err(1, "pipe");
        }
        child_pid = fork();
        switch (child_pid) {
        default:
                sa.sa_handler = SIG_IGN;
                sigaction(SIGTTOU, &sa, NULL);
                close(fds[0]);
                setpgid(child_pid, child_pid);
                if (tcgetpgrp(STDERR_FILENO) == getpgrp())
                        tcsetpgrp(STDERR_FILENO, child_pid);
                close(fds[1]);
                sigaction(SIGPIPE, &sa_pipe, NULL);
                while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) {
                        if (WIFSTOPPED(statusp)) {
                                child_pgrp = getpgid(child_pid);
                                if (tcgetpgrp(STDERR_FILENO) == child_pgrp)
                                        tcsetpgrp(STDERR_FILENO, getpgrp());
                                kill(getpid(), SIGSTOP);
                                if (tcgetpgrp(STDERR_FILENO) == getpgrp()) {
                                        child_pgrp = getpgid(child_pid);
                                        tcsetpgrp(STDERR_FILENO, child_pgrp);
                                }
                                kill(child_pid, SIGCONT);
                                statusp = 1;
                                continue;
                        }
                        break;
                }
                tcsetpgrp(STDERR_FILENO, getpgrp());
                if (pid == -1)
                        err(1, "waitpid");
                PAM_END();
                exit(WEXITSTATUS(statusp));
        case -1:
                PAM_END();
                err(1, "fork");
        case 0:
                close(fds[1]);
                read(fds[0], &temp, 1);
                close(fds[0]);
                sigaction(SIGPIPE, &sa_pipe, NULL);
                sigaction(SIGINT, &sa_int, NULL);
                sigaction(SIGQUIT, &sa_quit, NULL);

                /*
                 * Set all user context except for: Environmental variables
                 * Umask Login records (wtmp, etc) Path
                 */
                setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK |
                           LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP |
                           LOGIN_SETMAC);
                /*
                 * If -s is present, also set the MAC label.
                 */
                if (setmaclabel)
                        setwhat |= LOGIN_SETMAC;
                /*
                 * Don't touch resource/priority settings if -m has been used
                 * or -l and -c hasn't, and we're not su'ing to root.
                 */
                if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
                        setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES);
                if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
                        err(1, "setusercontext");

                if (!asme) {
                        if (asthem) {
                                p = getenv("TERM");
                                environ = &cleanenv;
                        }

                        if (asthem || pwd->pw_uid)
                                setenv("USER", pwd->pw_name, 1);
                        setenv("HOME", pwd->pw_dir, 1);
                        setenv("SHELL", shell, 1);

                        if (asthem) {
                                /*
                                 * Add any environmental variables that the
                                 * PAM modules may have set.
                                 */
                                environ_pam = pam_getenvlist(pamh);
                                if (environ_pam)
                                        export_pam_environment();

                                /* set the su'd user's environment & umask */
                                setusercontext(lc, pwd, pwd->pw_uid,
                                        LOGIN_SETPATH | LOGIN_SETUMASK |
                                        LOGIN_SETENV);
                                if (p)
                                        setenv("TERM", p, 1);

                                p = pam_getenv(pamh, "HOME");
                                if (chdir(p ? p : pwd->pw_dir) < 0)
                                        errx(1, "no directory");
                        }
                }
                login_close(lc);

                if (iscsh == YES) {
                        if (fastlogin)
                                *np.a-- = "-f";
                        if (asme)
                                *np.a-- = "-m";
                }
                /* csh strips the first character... */
                *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su";

                if (ruid != 0)
                        syslog(LOG_NOTICE, "%s to %s%s", username, user,
                            ontty());

                execv(shell, np.b);
                err(1, "%s", shell);
        }
}

static void
export_pam_environment(void)
{
        char    **pp;
        char    *p;

        for (pp = environ_pam; *pp != NULL; pp++) {
                if (ok_to_export(*pp)) {
                        p = strchr(*pp, '=');
                        *p = '\0';
                        setenv(*pp, p + 1, 1);
                }
                free(*pp);
        }
}

/*
 * Sanity checks on PAM environmental variables:
 * - Make sure there is an '=' in the string.
 * - Make sure the string doesn't run on too long.
 * - Do not export certain variables.  This list was taken from the
 *   Solaris pam_putenv(3) man page.
 * Note that if the user is chrooted, PAM may have a better idea than we
 * do of where her home directory is.
 */
static int
ok_to_export(const char *s)
{
        static const char *noexport[] = {
                "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH",
                "IFS", "PATH", NULL
        };
        const char **pp;
        size_t n;

        if (strlen(s) > 1024 || strchr(s, '=') == NULL)
                return 0;
        if (strncmp(s, "LD_", 3) == 0)
                return 0;
        for (pp = noexport; *pp != NULL; pp++) {
                n = strlen(*pp);
                if (s[n] == '=' && strncmp(s, *pp, n) == 0)
                        return 0;
        }
        return 1;
}

static void
usage(void)
{

        fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n");
        exit(1);
        /* NOTREACHED */
}

static int
chshell(const char *sh)
{
        int r;
        char *cp;

        r = 0;
        setusershell();
        while ((cp = getusershell()) != NULL && !r)
            r = (strcmp(cp, sh) == 0);
        endusershell();
        return r;
}

static char *
ontty(void)
{
        char *p;
        static char buf[MAXPATHLEN + 4];

        buf[0] = 0;
        p = ttyname(STDERR_FILENO);
        if (p)
                snprintf(buf, sizeof(buf), " on %s", p);
        return buf;
}