1 /* 2 * Copyright (c) 2002, 2005 Networks Associates Technologies, Inc. 3 * All rights reserved. 4 * 5 * Portions of this software were developed for the FreeBSD Project by 6 * ThinkSec AS and NAI Labs, the Security Research Division of Network 7 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 8 * ("CBOSS"), as part of the DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 * Copyright (c) 1988, 1993, 1994 33 * The Regents of the University of California. All rights reserved. 34 * 35 * Redistribution and use in source and binary forms, with or without 36 * modification, are permitted provided that the following conditions 37 * are met: 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. Neither the name of the University nor the names of its contributors 44 * may be used to endorse or promote products derived from this software 45 * without specific prior written permission. 46 * 47 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 48 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 49 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 50 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 51 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 52 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 53 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 54 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 55 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 56 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 57 * SUCH DAMAGE. 58 * 59 * @(#)su.c 8.3 (Berkeley) 4/2/94 60 * $FreeBSD: src/usr.bin/su/su.c,v 1.88 2008/06/04 19:16:54 dwmalone Exp $ 61 */ 62 63 #include <sys/param.h> 64 #include <sys/time.h> 65 #include <sys/resource.h> 66 #include <sys/wait.h> 67 68 #ifdef USE_BSM_AUDIT 69 #include <bsm/libbsm.h> 70 #include <bsm/audit_uevents.h> 71 #endif 72 73 #include <err.h> 74 #include <errno.h> 75 #include <grp.h> 76 #include <login_cap.h> 77 #include <paths.h> 78 #include <pwd.h> 79 #include <signal.h> 80 #include <stdio.h> 81 #include <stdlib.h> 82 #include <string.h> 83 #include <syslog.h> 84 #include <unistd.h> 85 #include <stdarg.h> 86 87 #include <security/pam_appl.h> 88 #include <security/openpam.h> 89 90 #define PAM_END() do { \ 91 int local_ret; \ 92 if (pamh != NULL) { \ 93 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 94 if (local_ret != PAM_SUCCESS) \ 95 syslog(LOG_ERR, "pam_setcred: %s", \ 96 pam_strerror(pamh, local_ret)); \ 97 if (asthem) { \ 98 local_ret = pam_close_session(pamh, 0); \ 99 if (local_ret != PAM_SUCCESS) \ 100 syslog(LOG_ERR, "pam_close_session: %s",\ 101 pam_strerror(pamh, local_ret)); \ 102 } \ 103 local_ret = pam_end(pamh, local_ret); \ 104 if (local_ret != PAM_SUCCESS) \ 105 syslog(LOG_ERR, "pam_end: %s", \ 106 pam_strerror(pamh, local_ret)); \ 107 } \ 108 } while (0) 109 110 111 #define PAM_SET_ITEM(what, item) do { \ 112 int local_ret; \ 113 local_ret = pam_set_item(pamh, what, item); \ 114 if (local_ret != PAM_SUCCESS) { \ 115 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 116 pam_strerror(pamh, local_ret)); \ 117 errx(1, "pam_set_item(" #what "): %s", \ 118 pam_strerror(pamh, local_ret)); \ 119 /* NOTREACHED */ \ 120 } \ 121 } while (0) 122 123 enum tristate { UNSET, YES, NO }; 124 125 static pam_handle_t *pamh = NULL; 126 static char **environ_pam; 127 128 static char *ontty(void); 129 static int chshell(const char *); 130 static void usage(void) __dead2; 131 static void export_pam_environment(void); 132 static int ok_to_export(const char *); 133 134 extern char **environ; 135 136 int 137 main(int argc, char **argv) 138 { 139 static char *cleanenv; 140 struct passwd *pwd; 141 struct pam_conv conv = { openpam_ttyconv, NULL }; 142 enum tristate iscsh; 143 login_cap_t *lc; 144 union { 145 const char **a; 146 char * const *b; 147 } np; 148 uid_t ruid; 149 pid_t child_pid, child_pgrp, pid; 150 int asme, ch, asthem, fastlogin, prio, i, retcode, 151 statusp; 152 u_int setwhat; 153 char *username, *class, shellbuf[MAXPATHLEN]; 154 const char *p = NULL, *user, *shell, *mytty, **nargv; 155 const void *v; 156 struct sigaction sa, sa_int, sa_quit, sa_pipe; 157 int temp, fds[2]; 158 #ifdef USE_BSM_AUDIT 159 const char *aerr; 160 au_id_t auid; 161 #endif 162 163 shell = class = cleanenv = NULL; 164 asme = asthem = fastlogin = statusp = 0; 165 user = "root"; 166 iscsh = UNSET; 167 168 while ((ch = getopt(argc, argv, "-flmc:")) != -1) 169 switch ((char)ch) { 170 case 'f': 171 fastlogin = 1; 172 break; 173 case '-': 174 case 'l': 175 asme = 0; 176 asthem = 1; 177 break; 178 case 'm': 179 asme = 1; 180 asthem = 0; 181 break; 182 case 'c': 183 class = optarg; 184 break; 185 case '?': 186 default: 187 usage(); 188 /* NOTREACHED */ 189 } 190 191 if (optind < argc && strcmp(argv[optind], "-") == 0) { 192 asme = 0; 193 asthem = 1; 194 optind++; 195 } 196 197 if (optind < argc) 198 user = argv[optind++]; 199 200 if (user == NULL) 201 usage(); 202 /* NOTREACHED */ 203 204 /* 205 * Try to provide more helpful debugging output if su(1) is running 206 * non-setuid, or was run from a file system not mounted setuid. 207 */ 208 if (geteuid() != 0) 209 errx(1, "not running setuid"); 210 211 #ifdef USE_BSM_AUDIT 212 if (getauid(&auid) < 0 && errno != ENOSYS) { 213 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 214 errx(1, "Permission denied"); 215 } 216 #endif 217 if (strlen(user) > MAXLOGNAME - 1) { 218 #ifdef USE_BSM_AUDIT 219 if (audit_submit(AUE_su, auid, 220 1, EPERM, "username too long: '%s'", user)) 221 errx(1, "Permission denied"); 222 #endif 223 errx(1, "username too long"); 224 } 225 226 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 227 if (nargv == NULL) 228 errx(1, "malloc failure"); 229 230 nargv[argc + 3] = NULL; 231 for (i = argc; i >= optind; i--) 232 nargv[i + 3] = argv[i]; 233 np.a = &nargv[i + 3]; 234 235 argv += optind; 236 237 errno = 0; 238 prio = getpriority(PRIO_PROCESS, 0); 239 if (errno) 240 prio = 0; 241 242 setpriority(PRIO_PROCESS, 0, -2); 243 openlog("su", LOG_CONS, LOG_AUTH); 244 245 /* get current login name, real uid and shell */ 246 ruid = getuid(); 247 username = getlogin(); 248 pwd = getpwnam(username); 249 if (username == NULL || pwd == NULL || pwd->pw_uid != ruid) 250 pwd = getpwuid(ruid); 251 if (pwd == NULL) { 252 #ifdef USE_BSM_AUDIT 253 if (audit_submit(AUE_su, auid, 1, EPERM, 254 "unable to determine invoking subject: '%s'", username)) 255 errx(1, "Permission denied"); 256 #endif 257 errx(1, "who are you?"); 258 } 259 260 username = strdup(pwd->pw_name); 261 if (username == NULL) 262 err(1, "strdup failure"); 263 264 if (asme) { 265 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 266 /* must copy - pwd memory is recycled */ 267 shell = strncpy(shellbuf, pwd->pw_shell, 268 sizeof(shellbuf)); 269 shellbuf[sizeof(shellbuf) - 1] = '\0'; 270 } 271 else { 272 shell = _PATH_BSHELL; 273 iscsh = NO; 274 } 275 } 276 277 /* Do the whole PAM startup thing */ 278 retcode = pam_start("su", user, &conv, &pamh); 279 if (retcode != PAM_SUCCESS) { 280 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 281 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 282 } 283 284 PAM_SET_ITEM(PAM_RUSER, username); 285 286 mytty = ttyname(STDERR_FILENO); 287 if (!mytty) 288 mytty = "tty"; 289 PAM_SET_ITEM(PAM_TTY, mytty); 290 291 retcode = pam_authenticate(pamh, 0); 292 if (retcode != PAM_SUCCESS) { 293 #ifdef USE_BSM_AUDIT 294 if (audit_submit(AUE_su, auid, 1, EPERM, "bad su %s to %s on %s", 295 username, user, mytty)) 296 errx(1, "Permission denied"); 297 #endif 298 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 299 username, user, mytty); 300 errx(1, "Sorry"); 301 } 302 #ifdef USE_BSM_AUDIT 303 if (audit_submit(AUE_su, auid, 0, 0, "successful authentication")) 304 errx(1, "Permission denied"); 305 #endif 306 retcode = pam_get_item(pamh, PAM_USER, &v); 307 if (retcode == PAM_SUCCESS) 308 user = v; 309 else 310 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 311 pam_strerror(pamh, retcode)); 312 pwd = getpwnam(user); 313 if (pwd == NULL) { 314 #ifdef USE_BSM_AUDIT 315 if (audit_submit(AUE_su, auid, 1, EPERM, 316 "unknown subject: %s", user)) 317 errx(1, "Permission denied"); 318 #endif 319 errx(1, "unknown login: %s", user); 320 } 321 322 retcode = pam_acct_mgmt(pamh, 0); 323 if (retcode == PAM_NEW_AUTHTOK_REQD) { 324 retcode = pam_chauthtok(pamh, 325 PAM_CHANGE_EXPIRED_AUTHTOK); 326 if (retcode != PAM_SUCCESS) { 327 #ifdef USE_BSM_AUDIT 328 aerr = pam_strerror(pamh, retcode); 329 if (aerr == NULL) 330 aerr = "Unknown PAM error"; 331 if (audit_submit(AUE_su, auid, 1, EPERM, 332 "pam_chauthtok: %s", aerr)) 333 errx(1, "Permission denied"); 334 #endif 335 syslog(LOG_ERR, "pam_chauthtok: %s", 336 pam_strerror(pamh, retcode)); 337 errx(1, "Sorry"); 338 } 339 } 340 if (retcode != PAM_SUCCESS) { 341 #ifdef USE_BSM_AUDIT 342 if (audit_submit(AUE_su, auid, 1, EPERM, "pam_acct_mgmt: %s", 343 pam_strerror(pamh, retcode))) 344 errx(1, "Permission denied"); 345 #endif 346 syslog(LOG_ERR, "pam_acct_mgmt: %s", 347 pam_strerror(pamh, retcode)); 348 errx(1, "Sorry"); 349 } 350 351 /* get target login information */ 352 if (class == NULL) 353 lc = login_getpwclass(pwd); 354 else { 355 if (ruid != 0) { 356 #ifdef USE_BSM_AUDIT 357 if (audit_submit(AUE_su, auid, 1, EPERM, 358 "only root may use -c")) 359 errx(1, "Permission denied"); 360 #endif 361 errx(1, "only root may use -c"); 362 } 363 lc = login_getclass(class); 364 if (lc == NULL) 365 errx(1, "unknown class: %s", class); 366 } 367 368 /* if asme and non-standard target shell, must be root */ 369 if (asme) { 370 if (ruid != 0 && !chshell(pwd->pw_shell)) 371 errx(1, "permission denied (shell)"); 372 } 373 else if (pwd->pw_shell && *pwd->pw_shell) { 374 shell = pwd->pw_shell; 375 iscsh = UNSET; 376 } 377 else { 378 shell = _PATH_BSHELL; 379 iscsh = NO; 380 } 381 382 /* if we're forking a csh, we want to slightly muck the args */ 383 if (iscsh == UNSET) { 384 p = strrchr(shell, '/'); 385 if (p) 386 ++p; 387 else 388 p = shell; 389 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 390 } 391 setpriority(PRIO_PROCESS, 0, prio); 392 393 /* 394 * PAM modules might add supplementary groups in pam_setcred(), so 395 * initialize them first. 396 */ 397 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 398 err(1, "setusercontext"); 399 400 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 401 if (retcode != PAM_SUCCESS) { 402 syslog(LOG_ERR, "pam_setcred: %s", 403 pam_strerror(pamh, retcode)); 404 errx(1, "failed to establish credentials."); 405 } 406 if (asthem) { 407 retcode = pam_open_session(pamh, 0); 408 if (retcode != PAM_SUCCESS) { 409 syslog(LOG_ERR, "pam_open_session: %s", 410 pam_strerror(pamh, retcode)); 411 errx(1, "failed to open session."); 412 } 413 } 414 415 /* 416 * We must fork() before setuid() because we need to call 417 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 418 */ 419 sa.sa_flags = SA_RESTART; 420 sa.sa_handler = SIG_IGN; 421 sigemptyset(&sa.sa_mask); 422 sigaction(SIGINT, &sa, &sa_int); 423 sigaction(SIGQUIT, &sa, &sa_quit); 424 sigaction(SIGPIPE, &sa, &sa_pipe); 425 sa.sa_handler = SIG_DFL; 426 sigaction(SIGTSTP, &sa, NULL); 427 statusp = 1; 428 if (pipe(fds) == -1) { 429 PAM_END(); 430 err(1, "pipe"); 431 } 432 child_pid = fork(); 433 switch (child_pid) { 434 default: 435 sa.sa_handler = SIG_IGN; 436 sigaction(SIGTTOU, &sa, NULL); 437 close(fds[0]); 438 setpgid(child_pid, child_pid); 439 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) 440 tcsetpgrp(STDERR_FILENO, child_pid); 441 close(fds[1]); 442 sigaction(SIGPIPE, &sa_pipe, NULL); 443 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 444 if (WIFSTOPPED(statusp)) { 445 child_pgrp = getpgid(child_pid); 446 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 447 tcsetpgrp(STDERR_FILENO, getpgrp()); 448 kill(getpid(), SIGSTOP); 449 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) { 450 child_pgrp = getpgid(child_pid); 451 tcsetpgrp(STDERR_FILENO, child_pgrp); 452 } 453 kill(child_pid, SIGCONT); 454 statusp = 1; 455 continue; 456 } 457 break; 458 } 459 tcsetpgrp(STDERR_FILENO, getpgrp()); 460 if (pid == -1) 461 err(1, "waitpid"); 462 PAM_END(); 463 exit(WEXITSTATUS(statusp)); 464 case -1: 465 PAM_END(); 466 err(1, "fork"); 467 case 0: 468 close(fds[1]); 469 read(fds[0], &temp, 1); 470 close(fds[0]); 471 sigaction(SIGPIPE, &sa_pipe, NULL); 472 sigaction(SIGINT, &sa_int, NULL); 473 sigaction(SIGQUIT, &sa_quit, NULL); 474 475 /* 476 * Set all user context except for: Environmental variables 477 * Umask Login records (wtmp, etc) Path 478 * XXX Missing LOGIN_SETMAC 479 */ 480 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 481 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP); 482 #if 0 483 /* 484 * If -s is present, also set the MAC label. 485 */ 486 if (setmaclabel) 487 setwhat |= LOGIN_SETMAC; 488 #endif 489 /* 490 * Don't touch resource/priority settings if -m has been used 491 * or -l and -c hasn't, and we're not su'ing to root. 492 */ 493 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 494 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 495 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 496 err(1, "setusercontext"); 497 498 if (!asme) { 499 if (asthem) { 500 p = getenv("TERM"); 501 environ = &cleanenv; 502 } 503 504 if (asthem || pwd->pw_uid) { 505 if (setenv("USER", pwd->pw_name, 1) == -1) { 506 err(1, "setenv: cannot set USER=%s", 507 pwd->pw_name); 508 } 509 } 510 if (setenv("HOME", pwd->pw_dir, 1) == -1) { 511 err(1, "setenv: cannot set HOME=%s", 512 pwd->pw_dir); 513 } 514 if (setenv("SHELL", shell, 1) == -1) 515 err(1, "setenv: cannot set SHELL=%s", shell); 516 517 if (asthem) { 518 /* 519 * Add any environmental variables that the 520 * PAM modules may have set. 521 */ 522 environ_pam = pam_getenvlist(pamh); 523 if (environ_pam) 524 export_pam_environment(); 525 526 /* set the su'd user's environment & umask */ 527 setusercontext(lc, pwd, pwd->pw_uid, 528 LOGIN_SETPATH | LOGIN_SETUMASK | 529 LOGIN_SETENV); 530 if (p) { 531 if (setenv("TERM", p, 1) == -1) { 532 err(1, 533 "setenv: cannot set TERM=%s", 534 p); 535 } 536 } 537 538 p = pam_getenv(pamh, "HOME"); 539 if (chdir(p ? p : pwd->pw_dir) < 0) 540 errx(1, "no directory"); 541 } 542 } 543 login_close(lc); 544 545 if (iscsh == YES) { 546 if (fastlogin) 547 *np.a-- = "-f"; 548 if (asme) 549 *np.a-- = "-m"; 550 } 551 /* csh strips the first character... */ 552 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 553 554 if (ruid != 0) 555 syslog(LOG_NOTICE, "%s to %s%s", username, user, 556 ontty()); 557 558 execv(shell, np.b); 559 err(1, "%s", shell); 560 } 561 } 562 563 static void 564 export_pam_environment(void) 565 { 566 char **pp; 567 char *p; 568 569 for (pp = environ_pam; *pp != NULL; pp++) { 570 if (ok_to_export(*pp)) { 571 p = strchr(*pp, '='); 572 *p = '\0'; 573 if (setenv(*pp, p + 1, 1) == -1) 574 err(1, "setenv: cannot set %s=%s", *pp, p + 1); 575 } 576 free(*pp); 577 } 578 } 579 580 /* 581 * Sanity checks on PAM environmental variables: 582 * - Make sure there is an '=' in the string. 583 * - Make sure the string doesn't run on too long. 584 * - Do not export certain variables. This list was taken from the 585 * Solaris pam_putenv(3) man page. 586 * Note that if the user is chrooted, PAM may have a better idea than we 587 * do of where her home directory is. 588 */ 589 static int 590 ok_to_export(const char *s) 591 { 592 static const char *noexport[] = { 593 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 594 "IFS", "PATH", NULL 595 }; 596 const char **pp; 597 size_t n; 598 599 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 600 return 0; 601 if (strncmp(s, "LD_", 3) == 0) 602 return 0; 603 for (pp = noexport; *pp != NULL; pp++) { 604 n = strlen(*pp); 605 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 606 return 0; 607 } 608 return 1; 609 } 610 611 static void 612 usage(void) 613 { 614 615 fprintf(stderr, "usage: su [-] [-flm] [-c class] [login [args]]\n"); 616 exit(1); 617 /* NOTREACHED */ 618 } 619 620 static int 621 chshell(const char *sh) 622 { 623 int r; 624 char *cp; 625 626 r = 0; 627 setusershell(); 628 while ((cp = getusershell()) != NULL && !r) 629 r = (strcmp(cp, sh) == 0); 630 endusershell(); 631 return r; 632 } 633 634 static char * 635 ontty(void) 636 { 637 char *p; 638 static char buf[MAXPATHLEN + 4]; 639 640 buf[0] = 0; 641 p = ttyname(STDERR_FILENO); 642 if (p) 643 snprintf(buf, sizeof(buf), " on %s", p); 644 return buf; 645 } 646