su.c revision 50477 
1/*
2 * Copyright (c) 1988, 1993, 1994
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifndef lint
35static const char copyright[] =
36"@(#) Copyright (c) 1988, 1993, 1994\n\
37	The Regents of the University of California.  All rights reserved.\n";
38#endif /* not lint */
39
40#ifndef lint
41#if 0
42static char sccsid[] = "@(#)su.c	8.3 (Berkeley) 4/2/94";
43#endif
44static const char rcsid[] =
45  "$FreeBSD: head/usr.bin/su/su.c 50477 1999-08-28 01:08:13Z peter $";
46#endif /* not lint */
47
48#include <sys/param.h>
49#include <sys/time.h>
50#include <sys/resource.h>
51
52#include <err.h>
53#include <errno.h>
54#include <grp.h>
55#include <paths.h>
56#include <pwd.h>
57#include <stdio.h>
58#include <stdlib.h>
59#include <string.h>
60#include <syslog.h>
61#include <unistd.h>
62#include <libutil.h>
63
64#ifdef LOGIN_CAP
65#include <login_cap.h>
66#endif
67
68#ifdef	SKEY
69#include <skey.h>
70#endif
71
72#ifdef KERBEROS
73#include <des.h>
74#include <krb.h>
75#include <netdb.h>
76
77#ifdef LOGIN_CAP
78#define	ARGSTR	"-Kflmc:"
79#else
80#define	ARGSTR	"-Kflm"
81#endif
82
83static int kerberos(char *username, char *user, int uid, char *pword);
84static int koktologin(char *name, char *toname);
85
86int use_kerberos = 1;
87#else /* !KERBEROS */
88#ifdef LOGIN_CAP
89#define	ARGSTR	"-flmc:"
90#else
91#define	ARGSTR	"-flm"
92#endif
93#endif /* KERBEROS */
94
95char   *ontty __P((void));
96int	chshell __P((char *));
97static void usage __P((void));
98
99int
100main(argc, argv)
101	int argc;
102	char **argv;
103{
104	extern char **environ;
105	struct passwd *pwd;
106#ifdef WHEELSU
107	char *targetpass;
108	int iswheelsu;
109#endif /* WHEELSU */
110	char *p, **g, *user, *shell=NULL, *username, **cleanenv, **nargv, **np;
111	struct group *gr;
112	uid_t ruid;
113	gid_t gid;
114	int asme, ch, asthem, fastlogin, prio, i;
115	enum { UNSET, YES, NO } iscsh = UNSET;
116#ifdef LOGIN_CAP
117	login_cap_t *lc;
118	char *class=NULL;
119	int setwhat;
120#endif
121#ifdef KERBEROS
122	char *k;
123#endif
124	char shellbuf[MAXPATHLEN];
125
126#ifdef WHEELSU
127	iswheelsu =
128#endif /* WHEELSU */
129	asme = asthem = fastlogin = 0;
130	user = "root";
131	while((ch = getopt(argc, argv, ARGSTR)) != -1)
132		switch((char)ch) {
133#ifdef KERBEROS
134		case 'K':
135			use_kerberos = 0;
136			break;
137#endif
138		case 'f':
139			fastlogin = 1;
140			break;
141		case '-':
142		case 'l':
143			asme = 0;
144			asthem = 1;
145			break;
146		case 'm':
147			asme = 1;
148			asthem = 0;
149			break;
150#ifdef LOGIN_CAP
151		case 'c':
152			class = optarg;
153			break;
154#endif
155		case '?':
156		default:
157			usage();
158		}
159
160	if (optind < argc)
161		user = argv[optind++];
162
163	if (strlen(user) > MAXLOGNAME - 1) {
164		(void)fprintf(stderr, "su: username too long.\n");
165		exit(1);
166	}
167
168	if (user == NULL)
169		usage();
170
171	if ((nargv = malloc (sizeof (char *) * (argc + 4))) == NULL) {
172	    errx(1, "malloc failure");
173	}
174
175	nargv[argc + 3] = NULL;
176	for (i = argc; i >= optind; i--)
177	    nargv[i + 3] = argv[i];
178	np = &nargv[i + 3];
179
180	argv += optind;
181
182#ifdef KERBEROS
183	k = auth_getval("auth_list");
184	if (k && !strstr(k, "kerberos"))
185	    use_kerberos = 0;
186#endif
187	errno = 0;
188	prio = getpriority(PRIO_PROCESS, 0);
189	if (errno)
190		prio = 0;
191	(void)setpriority(PRIO_PROCESS, 0, -2);
192	openlog("su", LOG_CONS, 0);
193
194	/* get current login name and shell */
195	ruid = getuid();
196	username = getlogin();
197	if (username == NULL || (pwd = getpwnam(username)) == NULL ||
198	    pwd->pw_uid != ruid)
199		pwd = getpwuid(ruid);
200	if (pwd == NULL)
201		errx(1, "who are you?");
202	username = strdup(pwd->pw_name);
203	gid = pwd->pw_gid;
204	if (username == NULL)
205		err(1, NULL);
206	if (asme) {
207		if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
208			/* copy: pwd memory is recycled */
209			shell = strncpy(shellbuf,  pwd->pw_shell, sizeof shellbuf);
210			shellbuf[sizeof shellbuf - 1] = '\0';
211		} else {
212			shell = _PATH_BSHELL;
213			iscsh = NO;
214		}
215	}
216
217	/* get target login information, default to root */
218	if ((pwd = getpwnam(user)) == NULL) {
219		errx(1, "unknown login: %s", user);
220	}
221#ifdef LOGIN_CAP
222	if (class==NULL) {
223		lc = login_getpwclass(pwd);
224	} else {
225		if (ruid)
226			errx(1, "only root may use -c");
227		lc = login_getclass(class);
228		if (lc == NULL)
229			errx(1, "unknown class: %s", class);
230	}
231#endif
232
233#ifdef WHEELSU
234	targetpass = strdup(pwd->pw_passwd);
235#endif /* WHEELSU */
236
237	if (ruid) {
238#ifdef KERBEROS
239		if (use_kerberos && koktologin(username, user)
240		    && !pwd->pw_uid) {
241			warnx("kerberos: not in %s's ACL.", user);
242			use_kerberos = 0;
243		}
244#endif
245		{
246			/*
247			 * Only allow those with pw_gid==0 or those listed in
248			 * group zero to su to root.  If group zero entry is
249			 * missing or empty, then allow anyone to su to root.
250			 * iswheelsu will only be set if the user is EXPLICITLY
251			 * listed in group zero.
252			 */
253			if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)) &&
254			    gr->gr_mem && *(gr->gr_mem))
255				for (g = gr->gr_mem;; ++g) {
256					if (!*g) {
257						if (gid == 0)
258							break;
259						else
260							errx(1, "you are not in the correct group to su %s.", user);
261					}
262					if (strcmp(username, *g) == 0) {
263#ifdef WHEELSU
264						iswheelsu = 1;
265#endif /* WHEELSU */
266						break;
267					}
268				}
269		}
270		/* if target requires a password, verify it */
271		if (*pwd->pw_passwd) {
272#ifdef	SKEY
273#ifdef WHEELSU
274			if (iswheelsu) {
275				pwd = getpwnam(username);
276			}
277#endif /* WHEELSU */
278			p = skey_getpass("Password:", pwd, 1);
279			if (!(!strcmp(pwd->pw_passwd, skey_crypt(p, pwd->pw_passwd, pwd, 1))
280#ifdef WHEELSU
281			      || (iswheelsu && !strcmp(targetpass, crypt(p,targetpass)))
282#endif /* WHEELSU */
283			      )) {
284#else
285			p = getpass("Password:");
286			if (strcmp(pwd->pw_passwd, crypt(p, pwd->pw_passwd))) {
287#endif
288#ifdef KERBEROS
289	    			if (!use_kerberos || (use_kerberos && kerberos(username, user, pwd->pw_uid, p)))
290#endif
291					{
292					fprintf(stderr, "Sorry\n");
293					syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s%s", username, user, ontty());
294					exit(1);
295				}
296			}
297#ifdef WHEELSU
298			if (iswheelsu) {
299				pwd = getpwnam(user);
300			}
301#endif /* WHEELSU */
302		}
303		if (pwd->pw_expire && time(NULL) >= pwd->pw_expire) {
304			fprintf(stderr, "Sorry - account expired\n");
305			syslog(LOG_AUTH|LOG_WARNING,
306				"BAD SU %s to %s%s", username,
307				user, ontty());
308			exit(1);
309		}
310	}
311
312	if (asme) {
313		/* if asme and non-standard target shell, must be root */
314		if (!chshell(pwd->pw_shell) && ruid)
315			errx(1, "permission denied (shell).");
316	} else if (pwd->pw_shell && *pwd->pw_shell) {
317		shell = pwd->pw_shell;
318		iscsh = UNSET;
319	} else {
320		shell = _PATH_BSHELL;
321		iscsh = NO;
322	}
323
324	/* if we're forking a csh, we want to slightly muck the args */
325	if (iscsh == UNSET) {
326		p = strrchr(shell, '/');
327		if (p)
328			++p;
329		else
330			p = shell;
331		if ((iscsh = strcmp(p, "csh") ? NO : YES) == NO)
332		    iscsh = strcmp(p, "tcsh") ? NO : YES;
333	}
334
335	(void)setpriority(PRIO_PROCESS, 0, prio);
336
337#ifdef LOGIN_CAP
338	/* Set everything now except the environment & umask */
339	setwhat = LOGIN_SETUSER|LOGIN_SETGROUP|LOGIN_SETRESOURCES|LOGIN_SETPRIORITY;
340	/*
341	 * Don't touch resource/priority settings if -m has been
342	 * used or -l and -c hasn't, and we're not su'ing to root.
343	 */
344        if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
345		setwhat &= ~(LOGIN_SETPRIORITY|LOGIN_SETRESOURCES);
346	if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
347		err(1, "setusercontext");
348#else
349	/* set permissions */
350	if (setgid(pwd->pw_gid) < 0)
351		err(1, "setgid");
352	if (initgroups(user, pwd->pw_gid))
353		errx(1, "initgroups failed");
354	if (setuid(pwd->pw_uid) < 0)
355		err(1, "setuid");
356#endif
357
358	if (!asme) {
359		if (asthem) {
360			p = getenv("TERM");
361#ifdef KERBEROS
362			k = getenv("KRBTKFILE");
363#endif
364			if ((cleanenv = calloc(20, sizeof(char*))) == NULL)
365				errx(1, "calloc");
366			cleanenv[0] = NULL;
367			environ = cleanenv;
368#ifdef LOGIN_CAP
369			/* set the su'd user's environment & umask */
370			setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
371#else
372			(void)setenv("PATH", _PATH_DEFPATH, 1);
373#endif
374			if (p)
375				(void)setenv("TERM", p, 1);
376#ifdef KERBEROS
377			if (k)
378				(void)setenv("KRBTKFILE", k, 1);
379#endif
380			if (chdir(pwd->pw_dir) < 0)
381				errx(1, "no directory");
382		}
383		if (asthem || pwd->pw_uid)
384			(void)setenv("USER", pwd->pw_name, 1);
385		(void)setenv("HOME", pwd->pw_dir, 1);
386		(void)setenv("SHELL", shell, 1);
387	}
388	if (iscsh == YES) {
389		if (fastlogin)
390			*np-- = "-f";
391		if (asme)
392			*np-- = "-m";
393	}
394
395	/* csh strips the first character... */
396	*np = asthem ? "-su" : iscsh == YES ? "_su" : "su";
397
398	if (ruid != 0)
399		syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
400		    username, user, ontty());
401
402	login_close(lc);
403
404	execv(shell, np);
405	err(1, "%s", shell);
406}
407
408static void
409usage()
410{
411	(void)fprintf(stderr, "usage: su [%s] [login [args]]\n", ARGSTR);
412	exit(1);
413}
414
415int
416chshell(sh)
417	char *sh;
418{
419	int  r = 0;
420	char *cp;
421
422	setusershell();
423	while (!r && (cp = getusershell()) != NULL)
424		r = strcmp(cp, sh) == 0;
425	endusershell();
426	return r;
427}
428
429char *
430ontty()
431{
432	char *p;
433	static char buf[MAXPATHLEN + 4];
434
435	buf[0] = 0;
436	p = ttyname(STDERR_FILENO);
437	if (p)
438		snprintf(buf, sizeof(buf), " on %s", p);
439	return (buf);
440}
441
442#ifdef KERBEROS
443int
444kerberos(username, user, uid, pword)
445	char *username, *user;
446	int uid;
447	char *pword;
448{
449	KTEXT_ST ticket;
450	AUTH_DAT authdata;
451	int kerno;
452	u_long faddr;
453	char lrealm[REALM_SZ], krbtkfile[MAXPATHLEN];
454	char hostname[MAXHOSTNAMELEN], savehost[MAXHOSTNAMELEN];
455	char *krb_get_phost();
456	struct hostent *hp;
457
458	if (krb_get_lrealm(lrealm, 1) != KSUCCESS)
459		return (1);
460	(void)sprintf(krbtkfile, "%s_%s_%lu", TKT_ROOT, user,
461	    (unsigned long)getuid());
462
463	(void)setenv("KRBTKFILE", krbtkfile, 1);
464	(void)krb_set_tkt_string(krbtkfile);
465	/*
466	 * Set real as well as effective ID to 0 for the moment,
467	 * to make the kerberos library do the right thing.
468	 */
469	if (setuid(0) < 0) {
470		warn("setuid");
471		return (1);
472	}
473
474	/*
475	 * Little trick here -- if we are su'ing to root,
476	 * we need to get a ticket for "xxx.root", where xxx represents
477	 * the name of the person su'ing.  Otherwise (non-root case),
478	 * we need to get a ticket for "yyy.", where yyy represents
479	 * the name of the person being su'd to, and the instance is null
480	 *
481	 * We should have a way to set the ticket lifetime,
482	 * with a system default for root.
483	 */
484	kerno = krb_get_pw_in_tkt((uid == 0 ? username : user),
485		(uid == 0 ? "root" : ""), lrealm,
486	    	"krbtgt", lrealm, DEFAULT_TKT_LIFE, pword);
487
488	if (kerno != KSUCCESS) {
489		if (kerno == KDC_PR_UNKNOWN) {
490			warnx("kerberos: principal unknown: %s.%s@%s",
491				(uid == 0 ? username : user),
492				(uid == 0 ? "root" : ""), lrealm);
493			return (1);
494		}
495		warnx("kerberos: unable to su: %s", krb_err_txt[kerno]);
496		syslog(LOG_NOTICE|LOG_AUTH,
497		    "BAD Kerberos SU: %s to %s%s: %s",
498		    username, user, ontty(), krb_err_txt[kerno]);
499		return (1);
500	}
501
502	if (chown(krbtkfile, uid, -1) < 0) {
503		warn("chown");
504		(void)unlink(krbtkfile);
505		return (1);
506	}
507
508	(void)setpriority(PRIO_PROCESS, 0, -2);
509
510	if (gethostname(hostname, sizeof(hostname)) == -1) {
511		warn("gethostname");
512		dest_tkt();
513		return (1);
514	}
515
516	(void)strncpy(savehost, krb_get_phost(hostname), sizeof(savehost));
517	savehost[sizeof(savehost) - 1] = '\0';
518
519	kerno = krb_mk_req(&ticket, "rcmd", savehost, lrealm, 33);
520
521	if (kerno == KDC_PR_UNKNOWN) {
522		warnx("Warning: TGT not verified.");
523		syslog(LOG_NOTICE|LOG_AUTH,
524		    "%s to %s%s, TGT not verified (%s); %s.%s not registered?",
525		    username, user, ontty(), krb_err_txt[kerno],
526		    "rcmd", savehost);
527	} else if (kerno != KSUCCESS) {
528		warnx("Unable to use TGT: %s", krb_err_txt[kerno]);
529		syslog(LOG_NOTICE|LOG_AUTH, "failed su: %s to %s%s: %s",
530		    username, user, ontty(), krb_err_txt[kerno]);
531		dest_tkt();
532		return (1);
533	} else {
534		if (!(hp = gethostbyname(hostname))) {
535			warnx("can't get addr of %s", hostname);
536			dest_tkt();
537			return (1);
538		}
539		memmove((char *)&faddr, (char *)hp->h_addr, sizeof(faddr));
540
541		if ((kerno = krb_rd_req(&ticket, "rcmd", savehost, faddr,
542		    &authdata, "")) != KSUCCESS) {
543			warnx("kerberos: unable to verify rcmd ticket: %s\n",
544			    krb_err_txt[kerno]);
545			syslog(LOG_NOTICE|LOG_AUTH,
546			    "failed su: %s to %s%s: %s", username,
547			     user, ontty(), krb_err_txt[kerno]);
548			dest_tkt();
549			return (1);
550		}
551	}
552	return (0);
553}
554
555int
556koktologin(name, toname)
557	char *name, *toname;
558{
559	AUTH_DAT *kdata;
560	AUTH_DAT kdata_st;
561	char realm[REALM_SZ];
562
563	if (krb_get_lrealm(realm, 1) != KSUCCESS)
564		return (1);
565	kdata = &kdata_st;
566	memset((char *)kdata, 0, sizeof(*kdata));
567	(void)strncpy(kdata->pname, name, sizeof kdata->pname - 1);
568	(void)strncpy(kdata->pinst,
569	    ((strcmp(toname, "root") == 0) ? "root" : ""), sizeof kdata->pinst - 1);
570	(void)strncpy(kdata->prealm, realm, sizeof kdata->prealm - 1);
571	return (kuserok(kdata, toname));
572}
573#endif
574