shadow/src/su.c

/*
 * Copyright 1989 - 1994, Julianne Frances Haugh
 * 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 Julianne F. Haugh 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 JULIE HAUGH 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 JULIE HAUGH 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 <config.h>

#include "rcsid.h"
RCSID(PKG_VER "$Id: su.c,v 1.18 2001/06/28 20:47:06 kloczek Exp $")

#include <sys/types.h>
#include <stdio.h>

#ifdef USE_PAM
#include "pam_defs.h"

static const struct pam_conv conv = {
        misc_conv,
        NULL
};

static pam_handle_t *pamh = NULL;
#endif

#include "prototypes.h"
#include "defines.h"

#include <grp.h>
#include <signal.h>
#include <pwd.h>
#include "pwauth.h"
#include "getdef.h"

/*
 * Assorted #defines to control su's behavior
 */

/*
 * Global variables
 */

/* not needed by sulog.c anymore */
static char name[BUFSIZ];
static char oldname[BUFSIZ];

static char *Prog;

struct	passwd	pwent;

/*
 * External identifiers
 */

extern char **newenvp;
extern size_t newenvc;

extern char **environ;

/* local function prototypes */

#ifndef USE_PAM

static RETSIGTYPE die(int);
static int iswheel(const char *);

/*
 * die - set or reset termio modes.
 *
 *	die() is called before processing begins.  signal() is then
 *	called with die() as the signal handler.  If signal later
 *	calls die() with a signal number, the terminal modes are
 *	then reset.
 */

static RETSIGTYPE
die(int killed)
{
	static TERMIO sgtty;

	if (killed)
		STTY(0, &sgtty);
	else
		GTTY(0, &sgtty);

	if (killed) {
		closelog();
		exit(killed);
	}
}

static int
iswheel(const char *username)
{
	struct group *grp;

	grp = getgrgid(0);
	if (!grp || !grp->gr_mem)
		return 0;
	return is_on_list(grp->gr_mem, username);
}
#endif /* !USE_PAM */


static void
su_failure(const char *tty)
{
	sulog(tty, 0, oldname, name);  /* log failed attempt */
#ifdef USE_SYSLOG
	if (getdef_bool("SYSLOG_SU_ENAB"))
		SYSLOG((pwent.pw_uid ? LOG_INFO:LOG_NOTICE,
			"- %s %s-%s\n", tty,
			oldname[0] ? oldname:"???",
			name[0] ? name:"???"));
	closelog();
#endif
	puts(_("Sorry."));
	exit(1);
}


/*
 * su - switch user id
 *
 *	su changes the user's ids to the values for the specified user.
 *	if no new user name is specified, "root" is used by default.
 *
 *	The only valid option is a "-" character, which is interpreted
 *	as requiring a new login session to be simulated.
 *
 *	Any additional arguments are passed to the user's shell.  In
 *	particular, the argument "-c" will cause the next argument to
 *	be interpreted as a command by the common shell programs.
 */

int
main(int argc, char **argv)
{
	char	*cp;
	const char *tty = 0;		/* Name of tty SU is run from        */
	int	doshell = 0;
	int	fakelogin = 0;
	int	amroot = 0;
	uid_t my_uid;
	struct	passwd	*pw = 0;
	char	**envp = environ;
#ifdef USE_PAM
	int ret;
#else  /* !USE_PAM */
	RETSIGTYPE (*oldsig)();
	int is_console = 0;
#ifdef	SHADOWPWD
	struct	spwd	*spwd = 0;
#endif
#ifdef SU_ACCESS
	char *oldpass;
#endif
#endif /* !USE_PAM */

	sanitize_env();

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);

	/*
	 * Get the program name.  The program name is used as a
	 * prefix to most error messages.
	 */

	Prog = Basename(argv[0]);

	OPENLOG("su");

	initenv();

	my_uid = getuid();
	amroot = (my_uid == 0);

	/*
	 * Get the tty name.  Entries will be logged indicating that
	 * the user tried to change to the named new user from the
	 * current terminal.
	 */

	if (isatty(0) && (cp = ttyname(0))) {
		if (strncmp (cp, "/dev/", 5) == 0)
			tty = cp + 5;
		else
			tty = cp;
#ifndef USE_PAM
		is_console = console(tty);
#endif
	} else {
		/*
		 * Be more paranoid, like su from SimplePAMApps.  --marekm
		 */
		if (!amroot) {
			fprintf(stderr, _("%s: must be run from a terminal\n"),
				Prog);
			exit(1);
		}
		tty = "???";
	}

	/*
	 * Process the command line arguments. 
	 */

	argc--; argv++;			/* shift out command name */

	if (argc > 0 && strcmp(argv[0], "-") == 0) {
		fakelogin = 1;
		argc--; argv++;		/* shift ... */
	}

	/*
	 * If a new login is being set up, the old environment will
	 * be ignored and a new one created later on.
	 */

	if (fakelogin) {
		if ((cp=getdef_str("ENV_TZ")))
			addenv(*cp == '/' ? tz(cp) : cp, NULL);
	/*
	 * The clock frequency will be reset to the login value if required
	 */
		if ((cp=getdef_str("ENV_HZ")))
			addenv(cp, NULL);  /* set the default $HZ, if one */
	/*
	 * The terminal type will be left alone if it is present in the
	 * environment already.
	 */
		if ((cp = getenv ("TERM")))
			addenv("TERM", cp);
	} else {
		while (*envp)
			addenv(*envp++, NULL);
	}

	/*
	 * The next argument must be either a user ID, or some flag to
	 * a subshell.  Pretty sticky since you can't have an argument
	 * which doesn't start with a "-" unless you specify the new user
	 * name.  Any remaining arguments will be passed to the user's
	 * login shell.
	 */

	if (argc > 0 && argv[0][0] != '-') {
		STRFCPY(name, argv[0]);	/* use this login id */
		argc--; argv++;		/* shift ... */
	}
	if (! name[0]) 			/* use default user ID */
		(void) strcpy (name, "root");

	doshell = argc == 0;		/* any arguments remaining? */

	/*
	 * Get the user's real name.  The current UID is used to determine
	 * who has executed su.  That user ID must exist.
	 */

	pw = get_my_pwent();
	if (!pw) {
		SYSLOG((LOG_CRIT, "Unknown UID: %d\n", (int) my_uid));
		su_failure(tty);
	}
	STRFCPY(oldname, pw->pw_name);

#ifndef USE_PAM
#ifdef SU_ACCESS
	/*
	 * Sort out the password of user calling su, in case needed later
	 * -- chris
	 */
#ifdef SHADOWPWD
	if ((spwd = getspnam(oldname)))
		pw->pw_passwd = spwd->sp_pwdp;
#endif
	oldpass = xstrdup(pw->pw_passwd);
#endif  /* SU_ACCESS */

#else  /* USE_PAM */
	ret = pam_start("su", name, &conv, &pamh);
	if (ret != PAM_SUCCESS) {
		SYSLOG((LOG_ERR, "pam_start: error %d\n", ret);
		fprintf(stderr, _("%s: pam_start: error %d\n"), Prog, ret));
		exit(1);
	}

	ret = pam_set_item(pamh, PAM_TTY, (const void *) tty);
	if (ret == PAM_SUCCESS)
		ret = pam_set_item(pamh, PAM_RUSER, (const void *) oldname);
	if (ret != PAM_SUCCESS) {
		SYSLOG((LOG_ERR, "pam_set_item: %s\n", pam_strerror(pamh, ret)));
		fprintf(stderr, "%s: %s\n", Prog, pam_strerror(pamh, ret));
		pam_end(pamh, ret);
		exit(1);
	}
#endif  /* USE_PAM */

top:
	/*
	 * This is the common point for validating a user whose name
	 * is known.  It will be reached either by normal processing,
	 * or if the user is to be logged into a subsystem root.
	 *
	 * The password file entries for the user is gotten and the
	 * account validated.
	 */

	if (!(pw = getpwnam(name))) {
		(void) fprintf (stderr, _("Unknown id: %s\n"), name);
		closelog();
		exit(1);
	}

#ifndef USE_PAM
#ifdef SHADOWPWD
	spwd = NULL;
	if (strcmp(pw->pw_passwd, SHADOW_PASSWD_STRING) == 0 && (spwd = getspnam(name)))
		pw->pw_passwd = spwd->sp_pwdp;
#endif
#endif  /* !USE_PAM */
	pwent = *pw;

#ifndef USE_PAM
	/*
	 * BSD systems only allow "wheel" to SU to root.  USG systems
	 * don't, so we make this a configurable option.
	 */

	/* The original Shadow 3.3.2 did this differently.  Do it like BSD:

	   - check for uid 0 instead of name "root" - there are systems
	   with several root accounts under different names,

	   - check the contents of /etc/group instead of the current group
	   set (you must be listed as a member, GID 0 is not sufficient).

	   In addition to this traditional feature, we now have complete
	   su access control (allow, deny, no password, own password).
	   Thanks to Chris Evans <lady0110@sable.ox.ac.uk>.  */

	if (!amroot) {
		if (pwent.pw_uid == 0 && getdef_bool("SU_WHEEL_ONLY")
		    && !iswheel(oldname)) {
			fprintf(stderr, _("You are not authorized to su %s\n"), name);
			exit(1);
		}
#ifdef SU_ACCESS
		switch (check_su_auth(oldname, name)) {
		case 0:  /* normal su, require target user's password */
			break;
		case 1:  /* require no password */
			pwent.pw_passwd = "";  /* XXX warning: const */
			break;
		case 2:  /* require own password */
			puts(_("(Enter your own password.)"));
			pwent.pw_passwd = oldpass;
			break;
		default:  /* access denied (-1) or unexpected value */
			fprintf(stderr, _("You are not authorized to su %s\n"), name);
			exit(1);
		}
#endif  /* SU_ACCESS */
	}
#endif  /* !USE_PAM */

	/*
	 * Set the default shell.
	 */

	if (pwent.pw_shell[0] == '\0')
		pwent.pw_shell = "/bin/sh";  /* XXX warning: const */

#ifdef USE_PAM
	ret = pam_authenticate(pamh, 0);
	if (ret != PAM_SUCCESS) {
		SYSLOG((LOG_ERR, "pam_authenticate: %s\n",
			pam_strerror(pamh, ret)));
		fprintf(stderr, "%s: %s\n", Prog, pam_strerror(pamh, ret));
		pam_end(pamh, ret);
		su_failure(tty);
	}

	ret = pam_acct_mgmt(pamh, 0);
	if (ret != PAM_SUCCESS) {
		if (amroot) {
			fprintf(stderr, _("%s: %s\n(Ignored)\n"), Prog, pam_strerror(pamh, ret));
		} else {
			SYSLOG((LOG_ERR, "pam_acct_mgmt: %s\n",
				pam_strerror(pamh, ret)));
			fprintf(stderr, "%s: %s\n", Prog, pam_strerror(pamh, ret));
			pam_end(pamh, ret);
			su_failure(tty);
		}
	}
#else  /* !USE_PAM */
	/*
	 * Set up a signal handler in case the user types QUIT.
	 */

	die (0);
	oldsig = signal (SIGQUIT, die);

	/*
	 * See if the system defined authentication method is being used.
	 * The first character of an administrator defined method is an
	 * '@' character.
	 */

	if (! amroot && pw_auth (pwent.pw_passwd, name, PW_SU, (char *) 0)) {
		SYSLOG((pwent.pw_uid ? LOG_NOTICE:LOG_WARN,
			"Authentication failed for %s\n", name));
		su_failure(tty);
	}
	signal (SIGQUIT, oldsig);

	/*
	 * Check to see if the account is expired.  root gets to
	 * ignore any expired accounts, but normal users can't become
	 * a user with an expired password.
	 */

	if (! amroot) {
#ifdef	SHADOWPWD
		if (!spwd)
			spwd = pwd_to_spwd(&pwent);

		if (isexpired(&pwent, spwd)) {
			SYSLOG((pwent.pw_uid ? LOG_WARN : LOG_CRIT,
				"Expired account %s\n", name));
			su_failure(tty);
		}
#else
#if defined(ATT_AGE) && defined(AGING)
		else if (pwent.pw_age[0] &&
				isexpired (&pwent)) {
			SYSLOG((pwent.pw_uid ? LOG_WARN:LOG_CRIT,
				"Expired account %s\n", name));
			su_failure(tty);
		}
#endif	/* ATT_AGE */
#endif
	}

	/*
	 * Check to see if the account permits "su".  root gets to
	 * ignore any restricted accounts, but normal users can't become
	 * a user if there is a "SU" entry in the /etc/porttime file
	 * denying access to the account.
	 */

	if (! amroot) {
		if (! isttytime (pwent.pw_name, "SU", time ((time_t *) 0))) {
			SYSLOG((pwent.pw_uid ? LOG_WARN : LOG_CRIT,
				"SU by %s to restricted account %s\n",
					oldname, name));
			su_failure(tty);
		}
	}
#endif  /* !USE_PAM */

	signal(SIGINT, SIG_DFL);
	cp = getdef_str((pwent.pw_uid == 0) ? "ENV_SUPATH" : "ENV_PATH");
#if 0
	addenv(cp ? cp : "PATH=/bin:/usr/bin", NULL);
#else
	/* XXX very similar code duplicated in libmisc/setupenv.c */
	if (!cp) {
		addenv("PATH=/bin:/usr/bin", NULL);
	} else if (strchr(cp, '=')) {
		addenv(cp, NULL);
	} else {
		addenv("PATH", cp);
	}
#endif

	environ = newenvp;		/* make new environment active */

	if (getenv ("IFS"))		/* don't export user IFS ... */
		addenv("IFS= \t\n", NULL);	/* ... instead, set a safe IFS */

	if (pwent.pw_shell[0] == '*') { /* subsystem root required */
		pwent.pw_shell++;	/* skip the '*' */
		subsystem (&pwent);	/* figure out what to execute */
		endpwent ();
#ifdef SHADOWPWD
		endspent ();
#endif
		goto top;
	}

	sulog(tty, 1, oldname, name);		/* save SU information */
	endpwent ();
#ifdef SHADOWPWD
	endspent ();
#endif
#ifdef USE_SYSLOG
	if (getdef_bool("SYSLOG_SU_ENAB"))
		SYSLOG((LOG_INFO, "+ %s %s-%s\n", tty,
			oldname[0] ? oldname:"???", name[0] ? name:"???"));
#endif

#ifdef USE_PAM
	/* set primary group id and supplementary groups */
	if (setup_groups(&pwent)) {
		pam_end(pamh, PAM_ABORT);
		exit(1);
	}

	/* pam_setcred() may do things like resource limits, console groups,
	   and much more, depending on the configured modules */
	ret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
	if (ret != PAM_SUCCESS) {
		SYSLOG((LOG_ERR, "pam_setcred: %s\n", pam_strerror(pamh, ret)));
		fprintf(stderr, "%s: %s\n", Prog, pam_strerror(pamh, ret));
		pam_end(pamh, ret);
		exit(1);
	}

	/* become the new user */
	if (change_uid(&pwent)) {
		pam_setcred(pamh, PAM_DELETE_CRED);
		pam_end(pamh, PAM_ABORT);
		exit(1);
	}

	/* now we are done using PAM */
	pam_end(pamh, PAM_SUCCESS);

#else  /* !USE_PAM */
	if (!amroot)  /* no limits if su from root */
		setup_limits(&pwent);

	if (setup_uid_gid(&pwent, is_console))
		exit(1);
#endif  /* !USE_PAM */

	if (fakelogin)
		setup_env(&pwent);
#if 1  /* Suggested by Joey Hess.  XXX - is this right?  */
	else
		addenv("HOME", pwent.pw_dir);
#endif

	/*
	 * This is a workaround for Linux libc bug/feature (?) - the
	 * /dev/log file descriptor is open without the close-on-exec
	 * flag and used to be passed to the new shell.  There is
	 * "fcntl(LogFile, F_SETFD, 1)" in libc/misc/syslog.c, but
	 * it is commented out (at least in 5.4.33).  Why?  --marekm
	 */
	closelog();

	/*
	 * See if the user has extra arguments on the command line.  In
	 * that case they will be provided to the new user's shell as
	 * arguments.
	 */

	if (fakelogin) {
		char *arg0;

#if 0  /* XXX - GNU su doesn't do this.  --marekm */
		if (! hushed (&pwent)) {
			motd ();
			mailcheck ();
		}
#endif
		cp = getdef_str("SU_NAME");
		if (!cp)
			cp = Basename(pwent.pw_shell);

		arg0 = xmalloc(strlen(cp) + 2);
		arg0[0] = '-';
		strcpy(arg0 + 1, cp);
		cp = arg0;
	} else
		cp = Basename(pwent.pw_shell);

	if (! doshell) {

		/*
		 * Use new user's shell from /etc/passwd and create an
		 * argv with the rest of the command line included.
		 */

		argv[-1] = pwent.pw_shell;
		(void) execv (pwent.pw_shell, &argv[-1]);
		(void) fprintf (stderr, _("No shell\n"));
		SYSLOG((LOG_WARN, "Cannot execute %s\n", pwent.pw_shell));
		closelog();
		exit (1);
	}

	shell(pwent.pw_shell, cp);
	/*NOTREACHED*/
	exit(1);
}