freebsd-dev/usr.bin/su/su.c

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1988, 1993, 1994\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)su.c	8.3 (Berkeley) 4/2/94";
#endif
static const char rcsid[] =
  "$FreeBSD$";
#endif /* not lint */

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

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

#ifdef USE_PAM
#include <security/pam_appl.h>
#include <security/pam_misc.h>
#include <signal.h>
#include <sys/wait.h>

static int export_pam_environment __P((void));
static int ok_to_export __P((const char *));

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

#define PAM_END { \
	if ((retcode = pam_setcred(pamh, PAM_DELETE_CRED)) != PAM_SUCCESS) { \
		syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, retcode)); \
	} \
	if ((retcode = pam_end(pamh,retcode)) != PAM_SUCCESS) { \
		syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, retcode)); \
	} \
}
#else /* !USE_PAM */
#ifdef	SKEY
#include <skey.h>
#endif
#endif /* USE_PAM */

#define	ARGSTR	"-flmc:"

char   *ontty __P((void));
int	chshell __P((char *));
static void usage __P((void));

int
main(argc, argv)
	int argc;
	char **argv;
{
	extern char **environ;
	struct passwd *pwd;
#ifdef WHEELSU
	char *targetpass;
	int iswheelsu;
#endif /* WHEELSU */
	char *p, *user, *shell=NULL, *username, *cleanenv = NULL, **nargv, **np;
	uid_t ruid;
	gid_t gid;
	int asme, ch, asthem, fastlogin, prio, i;
	enum { UNSET, YES, NO } iscsh = UNSET;
	login_cap_t *lc;
	char *class=NULL;
	int setwhat;
#ifdef USE_PAM
	int retcode;
	struct pam_conv conv = { misc_conv, NULL };
	char myhost[MAXHOSTNAMELEN + 1], *mytty;
	int statusp=0;
	int child_pid, child_pgrp, ret_pid;
#else /* !USE_PAM */
	char **g;
	struct group *gr;
#endif /* USE_PAM */
	char shellbuf[MAXPATHLEN];

#ifdef WHEELSU
	iswheelsu =
#endif /* WHEELSU */
	asme = asthem = fastlogin = 0;
	user = "root";
	while((ch = getopt(argc, argv, ARGSTR)) != -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 'c':
			class = optarg;
			break;
		case '?':
		default:
			usage();
		}

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

	if (strlen(user) > MAXLOGNAME - 1) {
		errx(1, "username too long");
	}
		
	if (user == NULL)
		usage();

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

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

	argv += optind;

	errno = 0;
	prio = getpriority(PRIO_PROCESS, 0);
	if (errno)
		prio = 0;
	(void)setpriority(PRIO_PROCESS, 0, -2);
	openlog("su", LOG_CONS, LOG_AUTH);

	/* get current login name and shell */
	ruid = getuid();
	username = getlogin();
	if (username == NULL || (pwd = getpwnam(username)) == NULL ||
	    pwd->pw_uid != ruid)
		pwd = getpwuid(ruid);
	if (pwd == NULL)
		errx(1, "who are you?");
	username = strdup(pwd->pw_name);
	gid = pwd->pw_gid;
	if (username == NULL)
		err(1, NULL);
	if (asme) {
		if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
			/* copy: pwd memory is recycled */
			shell = strncpy(shellbuf,  pwd->pw_shell, sizeof shellbuf);
			shellbuf[sizeof shellbuf - 1] = '\0';
		} else {
			shell = _PATH_BSHELL;
			iscsh = NO;
		}
	}

#ifdef USE_PAM
	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));
	}

	gethostname(myhost, sizeof(myhost));
	retcode = pam_set_item(pamh, PAM_RHOST, myhost);
	if (retcode != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s", pam_strerror(pamh, retcode));
		errx(1, "pam_set_item(PAM_RHOST): %s", pam_strerror(pamh, retcode));
	}

	mytty = ttyname(STDERR_FILENO);
	if (!mytty)
		mytty = "tty";
	retcode = pam_set_item(pamh, PAM_TTY, mytty);
	if (retcode != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_set_item(PAM_TTY): %s", pam_strerror(pamh, retcode));
		errx(1, "pam_set_item(PAM_TTY): %s", pam_strerror(pamh, retcode));
	}

	if (ruid) {
		retcode = pam_authenticate(pamh, 0);
		if (retcode != PAM_SUCCESS) {
			syslog(LOG_ERR, "pam_authenticate: %s", pam_strerror(pamh, retcode));
			errx(1, "Sorry");
		}

		if ((retcode = pam_get_item(pamh, PAM_USER, (const void **) &p)) == PAM_SUCCESS) {
			user = p;
		} else
			syslog(LOG_ERR, "pam_get_item(PAM_USER): %s",
			       pam_strerror(pamh, retcode));

		retcode = pam_acct_mgmt(pamh, 0);
		if (retcode == PAM_NEW_AUTHTOK_REQD) {
			retcode = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
			if (retcode != PAM_SUCCESS) {
				syslog(LOG_ERR, "pam_chauthtok: %s", pam_strerror(pamh, retcode));
				errx(1, "Sorry");
			}
		}
		if (retcode != PAM_SUCCESS) {
			syslog(LOG_ERR, "pam_acct_mgmt: %s", pam_strerror(pamh, retcode));
			errx(1, "Sorry");
		}
	}
#endif /* USE_PAM */

	/* get target login information, default to root */
	if ((pwd = getpwnam(user)) == NULL) {
		errx(1, "unknown login: %s", user);
	}
	if (class==NULL) {
		lc = login_getpwclass(pwd);
	} else {
		if (ruid)
			errx(1, "only root may use -c");
		lc = login_getclass(class);
		if (lc == NULL)
			errx(1, "unknown class: %s", class);
	}

#ifndef USE_PAM
#ifdef WHEELSU
	targetpass = strdup(pwd->pw_passwd);
#endif /* WHEELSU */

	if (ruid) {
		{
			/*
			 * Only allow those with pw_gid==0 or those listed in
			 * group zero to su to root.  If group zero entry is
			 * missing or empty, then allow anyone to su to root.
			 * iswheelsu will only be set if the user is EXPLICITLY
			 * listed in group zero.
			 */
			if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)) &&
			    gr->gr_mem && *(gr->gr_mem))
				for (g = gr->gr_mem;; ++g) {
					if (!*g) {
						if (gid == 0)
							break;
						else
							errx(1,
			     "you are not in the correct group (%s) to su %s.",
							    gr->gr_name,
							    user);
					}
					if (strcmp(username, *g) == 0) {
#ifdef WHEELSU
						iswheelsu = 1;
#endif /* WHEELSU */
						break;
					}
				}
		}
		/* if target requires a password, verify it */
		if (*pwd->pw_passwd) {
#ifdef	SKEY
#ifdef WHEELSU
			if (iswheelsu) {
				pwd = getpwnam(username);
			}
#endif /* WHEELSU */
			p = skey_getpass("Password:", pwd, 1);
			if (!(!strcmp(pwd->pw_passwd, skey_crypt(p, pwd->pw_passwd, pwd, 1))
#ifdef WHEELSU
			      || (iswheelsu && !strcmp(targetpass, crypt(p,targetpass)))
#endif /* WHEELSU */
			      ))
#else /* !SKEY */
			p = getpass("Password:");
			if (strcmp(pwd->pw_passwd, crypt(p, pwd->pw_passwd)))
#endif /* SKEY */
			{
				{
					syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s%s", username, user, ontty());
					errx(1, "Sorry");
				}
			}
#ifdef WHEELSU
			if (iswheelsu) {
				pwd = getpwnam(user);
			}
#endif /* WHEELSU */
		}
		if (pwd->pw_expire && time(NULL) >= pwd->pw_expire) {
			syslog(LOG_AUTH|LOG_WARNING,
				"BAD SU %s to %s%s", username,
				user, ontty());
			errx(1, "Sorry - account expired");
		}
	}
#endif /* USE_PAM */

	if (asme) {
		/* if asme and non-standard target shell, must be root */
		if (ruid && !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;
		if ((iscsh = strcmp(p, "csh") ? NO : YES) == NO)
		    iscsh = strcmp(p, "tcsh") ? NO : YES;
	}

	(void)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");

#ifdef USE_PAM
	retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
	if (retcode != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, retcode));
	}

	/*
	 * We must fork() before setuid() because we need to call
	 * pam_setcred(pamh, PAM_DELETE_CRED) as root.
	 */

	statusp = 1;
	switch ((child_pid = fork())) {
	default:
            while ((ret_pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) {
		if (WIFSTOPPED(statusp)) {
		    child_pgrp = tcgetpgrp(1);
		    kill(getpid(), SIGSTOP);
		    tcsetpgrp(1, child_pgrp);
		    kill(child_pid, SIGCONT); 
		    statusp = 1;
		    continue;
		}
		break;
            }
	    if (ret_pid == -1)
		err(1, "waitpid");
	    PAM_END;
	    exit(statusp);
	case -1:
	    err(1, "fork");
	    PAM_END;
	    exit (1);
	case 0:
#endif /* USE_PAM */

	/*
	 * 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);

	/*
	 * 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;

#ifdef USE_PAM
			/*
			 * Add any environmental variables that the
			 * PAM modules may have set.
			 */
			environ_pam = pam_getenvlist(pamh);
			if (environ_pam)
				export_pam_environment();
#endif /* USE_PAM */

			/* set the su'd user's environment & umask */
			setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
			if (p)
				(void)setenv("TERM", p, 1);
			if (chdir(pwd->pw_dir) < 0)
				errx(1, "no directory");
		}
		if (asthem || pwd->pw_uid)
			(void)setenv("USER", pwd->pw_name, 1);
		(void)setenv("HOME", pwd->pw_dir, 1);
		(void)setenv("SHELL", shell, 1);
	}

	login_close(lc);

	if (iscsh == YES) {
		if (fastlogin)
			*np-- = "-f";
		if (asme)
			*np-- = "-m";
	}

	/* csh strips the first character... */
	*np = asthem ? "-su" : iscsh == YES ? "_su" : "su";

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

	execv(shell, np);
	err(1, "%s", shell);
#ifdef USE_PAM
	}
#endif /* USE_PAM */
}

#ifdef USE_PAM
static int
export_pam_environment()
{
	char	**pp;

	for (pp = environ_pam; *pp != NULL; pp++) {
		if (ok_to_export(*pp))
			(void) putenv(*pp);
		free(*pp);
	}
	return PAM_SUCCESS;
}

/*
 * 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.
 */
static int
ok_to_export(s)
	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;
}
#endif /* USE_PAM */

static void
usage()
{
	errx(1, "usage: su [%s] [login [args]]", ARGSTR);
}

int
chshell(sh)
	char *sh;
{
	int  r = 0;
	char *cp;

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

char *
ontty()
{
	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);
}