1 /* $NetBSD: su.c,v 1.72 2015/06/16 22:54:11 christos Exp $ */
2
3 /*
4 * Copyright (c) 1988 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 #ifndef lint
34 __COPYRIGHT("@(#) Copyright (c) 1988\
35 The Regents of the University of California. All rights reserved.");
36 #endif /* not lint */
37
38 #ifndef lint
39 #if 0
40 static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94";*/
41 #else
42 __RCSID("$NetBSD: su.c,v 1.72 2015/06/16 22:54:11 christos Exp $");
43 #endif
44 #endif /* not lint */
45
46 #include <sys/param.h>
47 #include <sys/time.h>
48 #include <sys/resource.h>
49 #include <err.h>
50 #include <errno.h>
51 #include <grp.h>
52 #include <paths.h>
53 #include <pwd.h>
54 #include <stdio.h>
55 #ifdef SKEY
56 #include <skey.h>
57 #endif
58 #include <stdlib.h>
59 #include <string.h>
60 #include <syslog.h>
61 #include <time.h>
62 #include <tzfile.h>
63 #include <unistd.h>
64 #include <util.h>
65
66 #ifdef LOGIN_CAP
67 #include <login_cap.h>
68 #endif
69
70 #ifdef KERBEROS5
71 #include <krb5.h>
72 #endif
73
74 #ifdef ALLOW_GROUP_CHANGE
75 #include "grutil.h"
76 #endif
77 #include "suutil.h"
78
79 #ifdef KERBEROS5
80 #define ARGSTRX "-Kdflm"
81 static int kerberos5(char *, const char *, uid_t);
82 int use_kerberos = 1;
83 #else
84 #define ARGSTRX "-dflm"
85 #endif
86
87 #ifndef SU_GROUP
88 #define SU_GROUP "wheel"
89 #endif
90
91 #define GROUP_PASSWORD "Group Password:"
92
93 #ifdef LOGIN_CAP
94 #define ARGSTR ARGSTRX "c:"
95 #else
96 #define ARGSTR ARGSTRX
97 #endif
98
99 static int check_ingroup(int, const char *, const char *, int);
100
101 int
main(int argc,char ** argv)102 main(int argc, char **argv)
103 {
104 extern char **environ;
105 struct passwd *pwd;
106 char *p;
107 #ifdef BSD4_4
108 struct timeval tp;
109 #endif
110 uid_t ruid;
111 int asme, ch, asthem, fastlogin, prio, gohome;
112 enum { UNSET, YES, NO } iscsh = UNSET;
113 const char *user, *shell, *avshell;
114 char *username, **np;
115 #ifdef SU_ROOTAUTH
116 char *userpass;
117 #endif
118 char *class;
119 char shellbuf[MAXPATHLEN], avshellbuf[MAXPATHLEN];
120 time_t pw_warntime = _PASSWORD_WARNDAYS * SECSPERDAY;
121 #ifdef LOGIN_CAP
122 login_cap_t *lc;
123 #endif
124 #ifdef ALLOW_GROUP_CHANGE
125 char *gname;
126 #endif
127
128 (void)setprogname(argv[0]);
129 asme = asthem = fastlogin = 0;
130 gohome = 1;
131 shell = class = NULL;
132 while ((ch = getopt(argc, argv, ARGSTR)) != -1)
133 switch((char)ch) {
134 #ifdef KERBEROS5
135 case 'K':
136 use_kerberos = 0;
137 break;
138 #endif
139 #ifdef LOGIN_CAP
140 case 'c':
141 class = optarg;
142 break;
143 #endif
144 case 'd':
145 asme = 0;
146 asthem = 1;
147 gohome = 0;
148 break;
149 case 'f':
150 fastlogin = 1;
151 break;
152 case '-':
153 case 'l':
154 asme = 0;
155 asthem = 1;
156 break;
157 case 'm':
158 asme = 1;
159 asthem = 0;
160 break;
161 case '?':
162 default:
163 (void)fprintf(stderr,
164 #ifdef ALLOW_GROUP_CHANGE
165 "usage: %s [%s] [login[:group] [shell arguments]]\n",
166 #else
167 "usage: %s [%s] [login [shell arguments]]\n",
168 #endif
169 getprogname(), ARGSTR);
170 exit(EXIT_FAILURE);
171 }
172 argv += optind;
173
174 /* Lower the priority so su runs faster */
175 errno = 0;
176 prio = getpriority(PRIO_PROCESS, 0);
177 if (errno)
178 prio = 0;
179 if (prio > -2)
180 (void)setpriority(PRIO_PROCESS, 0, -2);
181 openlog("su", 0, LOG_AUTH);
182
183 /* get current login name and shell */
184 ruid = getuid();
185 username = getlogin();
186 if (username == NULL || (pwd = getpwnam(username)) == NULL ||
187 pwd->pw_uid != ruid)
188 pwd = getpwuid(ruid);
189 if (pwd == NULL)
190 errx(EXIT_FAILURE, "who are you?");
191 username = estrdup(pwd->pw_name);
192 #ifdef SU_ROOTAUTH
193 userpass = estrdup(pwd->pw_passwd);
194 #endif
195
196 if (asme) {
197 if (pwd->pw_shell && *pwd->pw_shell) {
198 (void)estrlcpy(shellbuf, pwd->pw_shell, sizeof(shellbuf));
199 shell = shellbuf;
200 } else {
201 shell = _PATH_BSHELL;
202 iscsh = NO;
203 }
204 }
205 /* get target login information, default to root */
206 user = *argv ? *argv : "root";
207 np = *argv ? argv : argv - 1;
208
209 #ifdef ALLOW_GROUP_CHANGE
210 if ((p = strchr(user, ':')) != NULL) {
211 *p = '\0';
212 gname = ++p;
213 }
214 else
215 gname = NULL;
216
217 #ifdef ALLOW_EMPTY_USER
218 if (user[0] == '\0' && gname != NULL)
219 user = username;
220 #endif
221 #endif
222 if ((pwd = getpwnam(user)) == NULL)
223 errx(EXIT_FAILURE, "unknown login `%s'", user);
224
225 #ifdef LOGIN_CAP
226 /* force the usage of specified class */
227 if (class) {
228 if (ruid)
229 errx(EXIT_FAILURE, "Only root may use -c");
230
231 pwd->pw_class = class;
232 }
233 if ((lc = login_getclass(pwd->pw_class)) == NULL)
234 errx(EXIT_FAILURE, "Unknown class %s", pwd->pw_class);
235
236 pw_warntime = (time_t)login_getcaptime(lc, "password-warn",
237 _PASSWORD_WARNDAYS * SECSPERDAY,
238 _PASSWORD_WARNDAYS * SECSPERDAY);
239 #endif
240
241 if (ruid
242 #ifdef KERBEROS5
243 && (!use_kerberos || kerberos5(username, user, pwd->pw_uid))
244 #endif
245 ) {
246 char *pass = pwd->pw_passwd;
247 int ok = pwd->pw_uid != 0;
248
249 #ifdef SU_ROOTAUTH
250 /*
251 * Allow those in group rootauth to su to root, by supplying
252 * their own password.
253 */
254 if (!ok) {
255 if ((ok = check_ingroup(-1, SU_ROOTAUTH, username, 0))) {
256 pass = userpass;
257 user = username;
258 }
259 }
260 #endif
261 /*
262 * Only allow those in group SU_GROUP to su to root,
263 * but only if that group has any members.
264 * If SU_GROUP has no members, allow anyone to su root
265 */
266 if (!ok)
267 ok = check_ingroup(-1, SU_GROUP, username, 1);
268 if (!ok)
269 errx(EXIT_FAILURE,
270 "you are not listed in the correct secondary group (%s) to su %s.",
271 SU_GROUP, user);
272 /* if target requires a password, verify it */
273 if (*pass && pwd->pw_uid != ruid) { /* XXX - OK? */
274 p = getpass("Password:");
275 #ifdef SKEY
276 if (strcasecmp(p, "s/key") == 0) {
277 if (skey_haskey(user))
278 errx(EXIT_FAILURE,
279 "Sorry, you have no s/key.");
280 else {
281 if (skey_authenticate(user)) {
282 goto badlogin;
283 }
284 }
285
286 } else
287 #endif
288 if (strcmp(pass, crypt(p, pass)) != 0) {
289 #ifdef SKEY
290 badlogin:
291 #endif
292 (void)fprintf(stderr, "Sorry\n");
293 syslog(LOG_WARNING,
294 "BAD SU %s to %s%s", username,
295 pwd->pw_name, ontty());
296 exit(EXIT_FAILURE);
297 }
298 }
299 }
300
301 if (asme) {
302 /* if asme and non-standard target shell, must be root */
303 if (chshell(pwd->pw_shell) == 0 && ruid)
304 errx(EXIT_FAILURE, "permission denied (shell).");
305 } else if (pwd->pw_shell && *pwd->pw_shell) {
306 shell = pwd->pw_shell;
307 iscsh = UNSET;
308 } else {
309 shell = _PATH_BSHELL;
310 iscsh = NO;
311 }
312
313 if ((p = strrchr(shell, '/')) != NULL)
314 avshell = p+1;
315 else
316 avshell = shell;
317
318 /* if we're forking a csh, we want to slightly muck the args */
319 if (iscsh == UNSET)
320 iscsh = strstr(avshell, "csh") ? YES : NO;
321
322 /* set permissions */
323 #ifdef LOGIN_CAP
324 # ifdef ALLOW_GROUP_CHANGE
325 /* if we aren't changing users, keep the current group members */
326 if (ruid != pwd->pw_uid &&
327 setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) == -1)
328 err(EXIT_FAILURE, "setting user context");
329
330 addgroup(lc, gname, pwd, ruid, GROUP_PASSWORD);
331
332 if (setusercontext(lc, pwd, pwd->pw_uid,
333 (u_int)(asthem ? (LOGIN_SETPRIORITY | LOGIN_SETUMASK) : 0) |
334 LOGIN_SETRESOURCES | LOGIN_SETUSER) == -1)
335 err(EXIT_FAILURE, "setting user context");
336 # else
337 if (setusercontext(lc, pwd, pwd->pw_uid,
338 (u_int)(asthem ? (LOGIN_SETPRIORITY | LOGIN_SETUMASK) : 0) |
339 LOGIN_SETRESOURCES | LOGIN_SETGROUP | LOGIN_SETUSER) == -1)
340 err(EXIT_FAILURE, "setting user context");
341 # endif
342 #else
343 if (setgid(pwd->pw_gid) == -1)
344 err(EXIT_FAILURE, "setgid");
345 /* if we aren't changing users, keep the current group members */
346 if (ruid != pwd->pw_uid && initgroups(user, pwd->pw_gid) != 0)
347 errx(EXIT_FAILURE, "initgroups failed");
348 # ifdef ALLOW_GROUP_CHANGE
349 addgroup(/*EMPTY*/, gname, pwd, ruid, GROUP_PASSWORD);
350 # endif
351 if (setuid(pwd->pw_uid) == -1)
352 err(EXIT_FAILURE, "setuid");
353 #endif
354
355 if (!asme) {
356 if (asthem) {
357 p = getenv("TERM");
358 /* Create an empty environment */
359 environ = emalloc(sizeof(char *));
360 environ[0] = NULL;
361 #ifdef LOGIN_CAP
362 if (setusercontext(lc, pwd, pwd->pw_uid,
363 LOGIN_SETPATH) == -1)
364 err(EXIT_FAILURE, "setting user context");
365 #else
366 (void)setenv("PATH", _PATH_DEFPATH, 1);
367 #endif
368 if (p)
369 (void)setenv("TERM", p, 1);
370 if (gohome && chdir(pwd->pw_dir) == -1)
371 errx(EXIT_FAILURE, "no directory");
372 }
373
374 if (asthem || pwd->pw_uid) {
375 (void)setenv("LOGNAME", pwd->pw_name, 1);
376 (void)setenv("USER", pwd->pw_name, 1);
377 }
378 (void)setenv("HOME", pwd->pw_dir, 1);
379 (void)setenv("SHELL", shell, 1);
380 }
381 (void)setenv("SU_FROM", username, 1);
382
383 if (iscsh == YES) {
384 if (fastlogin)
385 *np-- = __UNCONST("-f");
386 if (asme)
387 *np-- = __UNCONST("-m");
388 } else {
389 if (fastlogin)
390 (void)unsetenv("ENV");
391 }
392
393 if (asthem) {
394 avshellbuf[0] = '-';
395 (void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
396 avshell = avshellbuf;
397 } else if (iscsh == YES) {
398 /* csh strips the first character... */
399 avshellbuf[0] = '_';
400 (void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
401 avshell = avshellbuf;
402 }
403 *np = __UNCONST(avshell);
404
405 #ifdef BSD4_4
406 if (pwd->pw_change || pwd->pw_expire)
407 (void)gettimeofday(&tp, NULL);
408 if (pwd->pw_change) {
409 if (tp.tv_sec >= pwd->pw_change) {
410 (void)printf("%s -- %s's password has expired.\n",
411 (ruid ? "Sorry" : "Note"), user);
412 if (ruid != 0)
413 exit(EXIT_FAILURE);
414 } else if (pwd->pw_change - tp.tv_sec < pw_warntime)
415 (void)printf("Warning: %s's password expires on %s",
416 user, ctime(&pwd->pw_change));
417 }
418 if (pwd->pw_expire) {
419 if (tp.tv_sec >= pwd->pw_expire) {
420 (void)printf("%s -- %s's account has expired.\n",
421 (ruid ? "Sorry" : "Note"), user);
422 if (ruid != 0)
423 exit(EXIT_FAILURE);
424 } else if (pwd->pw_expire - tp.tv_sec <
425 _PASSWORD_WARNDAYS * SECSPERDAY)
426 (void)printf("Warning: %s's account expires on %s",
427 user, ctime(&pwd->pw_expire));
428 }
429 #endif
430 if (ruid != 0)
431 syslog(LOG_NOTICE, "%s to %s%s",
432 username, pwd->pw_name, ontty());
433
434 /* Raise our priority back to what we had before */
435 (void)setpriority(PRIO_PROCESS, 0, prio);
436
437 (void)execv(shell, np);
438 err(EXIT_FAILURE, "%s", shell);
439 /* NOTREACHED */
440 }
441
442
443 #ifdef KERBEROS5
444 static int
kerberos5(char * username,const char * user,uid_t uid)445 kerberos5(char *username, const char *user, uid_t uid)
446 {
447 krb5_error_code ret;
448 krb5_context context;
449 krb5_principal princ = NULL;
450 krb5_ccache ccache, ccache2;
451 char *cc_name;
452 const char *filename;
453
454 ret = krb5_init_context(&context);
455 if (ret)
456 return 1;
457
458 if (strcmp(user, "root") == 0)
459 ret = krb5_make_principal(context, &princ,
460 NULL, username, "root", NULL);
461 else
462 ret = krb5_make_principal(context, &princ,
463 NULL, user, NULL);
464 if (ret)
465 goto fail;
466 if (!krb5_kuserok(context, princ, user) && !uid) {
467 warnx("kerberos5: not in %s's ACL.", user);
468 goto fail;
469 }
470 ret = krb5_cc_new_unique(context, krb5_mcc_ops.prefix, NULL, &ccache);
471 if (ret)
472 goto fail;
473 ret = krb5_verify_user_lrealm(context, princ, ccache, NULL, TRUE,
474 NULL);
475 if (ret) {
476 krb5_cc_destroy(context, ccache);
477 switch (ret) {
478 case KRB5_LIBOS_PWDINTR :
479 break;
480 case KRB5KRB_AP_ERR_BAD_INTEGRITY:
481 case KRB5KRB_AP_ERR_MODIFIED:
482 krb5_warnx(context, "Password incorrect");
483 break;
484 default :
485 krb5_warn(context, ret, "krb5_verify_user");
486 break;
487 }
488 goto fail;
489 }
490 ret = krb5_cc_new_unique(context, krb5_mcc_ops.prefix, NULL, &ccache2);
491 if (ret) {
492 krb5_cc_destroy(context, ccache);
493 goto fail;
494 }
495 ret = krb5_cc_copy_cache(context, ccache, ccache2);
496 if (ret) {
497 krb5_cc_destroy(context, ccache);
498 krb5_cc_destroy(context, ccache2);
499 goto fail;
500 }
501
502 filename = krb5_cc_get_name(context, ccache2);
503 (void)easprintf(&cc_name, "%s:%s", krb5_cc_get_type(context, ccache2),
504 filename);
505 if (chown(filename, uid, NOGROUP) == -1) {
506 warn("chown %s", filename);
507 free(cc_name);
508 krb5_cc_destroy(context, ccache);
509 krb5_cc_destroy(context, ccache2);
510 goto fail;
511 }
512
513 (void)setenv("KRB5CCNAME", cc_name, 1);
514 free(cc_name);
515 krb5_cc_close(context, ccache2);
516 krb5_cc_destroy(context, ccache);
517 return 0;
518
519 fail:
520 if (princ != NULL)
521 krb5_free_principal(context, princ);
522 krb5_free_context(context);
523 return 1;
524 }
525 #endif /* KERBEROS5 */
526
527 static int
check_ingroup(int gid,const char * gname,const char * user,int ifempty)528 check_ingroup(int gid, const char *gname, const char *user, int ifempty)
529 {
530 struct group *gr;
531 char **g;
532 #ifdef SU_INDIRECT_GROUP
533 char **gr_mem;
534 int n = 0;
535 int i = 0;
536 #endif
537 int ok = 0;
538
539 if (gname == NULL)
540 gr = getgrgid((gid_t) gid);
541 else
542 gr = getgrnam(gname);
543
544 /*
545 * XXX we are relying on the fact that we only set ifempty when
546 * calling to check for SU_GROUP and that is the only time a
547 * missing group is acceptable.
548 */
549 if (gr == NULL)
550 return ifempty;
551 if (!*gr->gr_mem) /* empty */
552 return ifempty;
553
554 /*
555 * Ok, first see if user is in gr_mem
556 */
557 for (g = gr->gr_mem; *g; ++g) {
558 if (strcmp(*g, user) == 0)
559 return 1; /* ok */
560 #ifdef SU_INDIRECT_GROUP
561 ++n; /* count them */
562 #endif
563 }
564 #ifdef SU_INDIRECT_GROUP
565 /*
566 * No.
567 * Now we need to duplicate the gr_mem list, and recurse for
568 * each member to see if it is a group, and if so whether user is
569 * in it.
570 */
571 gr_mem = emalloc((n + 1) * sizeof (char *));
572 for (g = gr->gr_mem, i = 0; *g; ++g) {
573 gr_mem[i] = estrdup(*g);
574 i++;
575 }
576 gr_mem[i++] = NULL;
577
578 for (g = gr_mem; ok == 0 && *g; ++g) {
579 /*
580 * If we get this far we don't accept empty/missing groups.
581 */
582 ok = check_ingroup(-1, *g, user, 0);
583 }
584 for (g = gr_mem; *g; ++g) {
585 free(*g);
586 }
587 free(gr_mem);
588 #endif
589 return ok;
590 }
591