1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2002, 2005 Networks Associates Technologies, Inc. 5 * All rights reserved. 6 * 7 * Portions of this software were developed for the FreeBSD Project by 8 * ThinkSec AS and NAI Labs, the Security Research Division of Network 9 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 10 * ("CBOSS"), as part of the DARPA CHATS research program. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 * Copyright (c) 1988, 1993, 1994 35 * The Regents of the University of California. All rights reserved. 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. Neither the name of the University nor the names of its contributors 46 * may be used to endorse or promote products derived from this software 47 * without specific prior written permission. 48 * 49 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 50 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 51 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 52 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 53 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 54 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 55 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 56 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 57 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 58 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 59 * SUCH DAMAGE. 60 */ 61 62 #include <sys/param.h> 63 #include <sys/time.h> 64 #include <sys/resource.h> 65 #include <sys/wait.h> 66 67 #ifdef USE_BSM_AUDIT 68 #include <bsm/libbsm.h> 69 #include <bsm/audit_uevents.h> 70 #endif 71 72 #include <err.h> 73 #include <errno.h> 74 #include <grp.h> 75 #include <login_cap.h> 76 #include <paths.h> 77 #include <pwd.h> 78 #include <signal.h> 79 #include <stdio.h> 80 #include <stdlib.h> 81 #include <string.h> 82 #include <syslog.h> 83 #include <unistd.h> 84 #include <stdarg.h> 85 86 #include <security/pam_appl.h> 87 #include <security/openpam.h> 88 89 #define PAM_END() do { \ 90 int local_ret; \ 91 if (pamh != NULL) { \ 92 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 93 if (local_ret != PAM_SUCCESS) \ 94 syslog(LOG_ERR, "pam_setcred: %s", \ 95 pam_strerror(pamh, local_ret)); \ 96 if (asthem) { \ 97 local_ret = pam_close_session(pamh, 0); \ 98 if (local_ret != PAM_SUCCESS) \ 99 syslog(LOG_ERR, "pam_close_session: %s",\ 100 pam_strerror(pamh, local_ret)); \ 101 } \ 102 local_ret = pam_end(pamh, local_ret); \ 103 if (local_ret != PAM_SUCCESS) \ 104 syslog(LOG_ERR, "pam_end: %s", \ 105 pam_strerror(pamh, local_ret)); \ 106 } \ 107 } while (0) 108 109 110 #define PAM_SET_ITEM(what, item) do { \ 111 int local_ret; \ 112 local_ret = pam_set_item(pamh, what, item); \ 113 if (local_ret != PAM_SUCCESS) { \ 114 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 115 pam_strerror(pamh, local_ret)); \ 116 errx(1, "pam_set_item(" #what "): %s", \ 117 pam_strerror(pamh, local_ret)); \ 118 /* NOTREACHED */ \ 119 } \ 120 } while (0) 121 122 enum tristate { UNSET, YES, NO }; 123 124 static pam_handle_t *pamh = NULL; 125 static char **environ_pam; 126 127 static char *ontty(void); 128 static int chshell(const char *); 129 static void usage(void) __dead2; 130 static void export_pam_environment(void); 131 static int ok_to_export(const char *); 132 133 extern char **environ; 134 135 int 136 main(int argc, char *argv[]) 137 { 138 static char *cleanenv; 139 struct passwd *pwd = NULL; 140 struct pam_conv conv = { openpam_ttyconv, NULL }; 141 enum tristate iscsh; 142 login_cap_t *lc; 143 union { 144 const char **a; 145 char * const *b; 146 } np; 147 uid_t ruid; 148 pid_t child_pid, child_pgrp, pid; 149 int asme, ch, asthem, fastlogin, prio, i, retcode, 150 statusp, setmaclabel; 151 u_int setwhat; 152 char *username, *class, shellbuf[MAXPATHLEN]; 153 const char *p, *user, *shell, *mytty, **nargv; 154 const void *v; 155 struct sigaction sa, sa_int, sa_quit, sa_pipe; 156 int temp, fds[2]; 157 #ifdef USE_BSM_AUDIT 158 const char *aerr; 159 au_id_t auid; 160 #endif 161 162 p = shell = class = cleanenv = NULL; 163 asme = asthem = fastlogin = statusp = 0; 164 user = "root"; 165 iscsh = UNSET; 166 setmaclabel = 0; 167 168 while ((ch = getopt(argc, argv, "-flmsc:")) != -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 's': 183 setmaclabel = 1; 184 break; 185 case 'c': 186 class = optarg; 187 break; 188 case '?': 189 default: 190 usage(); 191 /* NOTREACHED */ 192 } 193 194 if (optind < argc) 195 user = argv[optind++]; 196 197 if (user == NULL) 198 usage(); 199 /* NOTREACHED */ 200 201 /* 202 * Try to provide more helpful debugging output if su(1) is running 203 * non-setuid, or was run from a file system not mounted setuid. 204 */ 205 if (geteuid() != 0) 206 errx(1, "not running setuid"); 207 208 #ifdef USE_BSM_AUDIT 209 if (getauid(&auid) < 0 && errno != ENOSYS) { 210 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 211 errx(1, "Permission denied"); 212 } 213 #endif 214 if (strlen(user) > MAXLOGNAME - 1) { 215 #ifdef USE_BSM_AUDIT 216 if (audit_submit(AUE_su, auid, 217 EPERM, 1, "username too long: '%s'", user)) 218 errx(1, "Permission denied"); 219 #endif 220 errx(1, "username too long"); 221 } 222 223 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 224 if (nargv == NULL) 225 errx(1, "malloc failure"); 226 227 nargv[argc + 3] = NULL; 228 for (i = argc; i >= optind; i--) 229 nargv[i + 3] = argv[i]; 230 np.a = &nargv[i + 3]; 231 232 argv += optind; 233 234 errno = 0; 235 prio = getpriority(PRIO_PROCESS, 0); 236 if (errno) 237 prio = 0; 238 239 setpriority(PRIO_PROCESS, 0, -2); 240 openlog("su", LOG_CONS, LOG_AUTH); 241 242 /* get current login name, real uid and shell */ 243 ruid = getuid(); 244 username = getlogin(); 245 if (username != NULL) 246 pwd = getpwnam(username); 247 if (pwd == NULL || pwd->pw_uid != ruid) 248 pwd = getpwuid(ruid); 249 if (pwd == NULL) { 250 #ifdef USE_BSM_AUDIT 251 if (audit_submit(AUE_su, auid, EPERM, 1, 252 "unable to determine invoking subject: '%s'", username)) 253 errx(1, "Permission denied"); 254 #endif 255 errx(1, "who are you?"); 256 } 257 258 username = strdup(pwd->pw_name); 259 if (username == NULL) 260 err(1, "strdup failure"); 261 262 if (asme) { 263 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 264 /* must copy - pwd memory is recycled */ 265 strlcpy(shellbuf, pwd->pw_shell, 266 sizeof(shellbuf)); 267 shell = shellbuf; 268 } 269 else { 270 shell = _PATH_BSHELL; 271 iscsh = NO; 272 } 273 } 274 275 /* Do the whole PAM startup thing */ 276 retcode = pam_start("su", user, &conv, &pamh); 277 if (retcode != PAM_SUCCESS) { 278 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 279 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 280 } 281 282 PAM_SET_ITEM(PAM_RUSER, username); 283 284 mytty = ttyname(STDERR_FILENO); 285 if (!mytty) 286 mytty = "tty"; 287 PAM_SET_ITEM(PAM_TTY, mytty); 288 289 retcode = pam_authenticate(pamh, 0); 290 if (retcode != PAM_SUCCESS) { 291 #ifdef USE_BSM_AUDIT 292 if (audit_submit(AUE_su, auid, EPERM, 1, "bad su %s to %s on %s", 293 username, user, mytty)) 294 errx(1, "Permission denied"); 295 #endif 296 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 297 username, user, mytty); 298 errx(1, "Sorry"); 299 } 300 #ifdef USE_BSM_AUDIT 301 if (audit_submit(AUE_su, auid, 0, 0, "successful authentication")) 302 errx(1, "Permission denied"); 303 #endif 304 retcode = pam_get_item(pamh, PAM_USER, &v); 305 if (retcode == PAM_SUCCESS) 306 user = v; 307 else 308 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 309 pam_strerror(pamh, retcode)); 310 pwd = getpwnam(user); 311 if (pwd == NULL) { 312 #ifdef USE_BSM_AUDIT 313 if (audit_submit(AUE_su, auid, EPERM, 1, 314 "unknown subject: %s", user)) 315 errx(1, "Permission denied"); 316 #endif 317 errx(1, "unknown login: %s", user); 318 } 319 320 retcode = pam_acct_mgmt(pamh, 0); 321 if (retcode == PAM_NEW_AUTHTOK_REQD) { 322 retcode = pam_chauthtok(pamh, 323 PAM_CHANGE_EXPIRED_AUTHTOK); 324 if (retcode != PAM_SUCCESS) { 325 #ifdef USE_BSM_AUDIT 326 aerr = pam_strerror(pamh, retcode); 327 if (aerr == NULL) 328 aerr = "Unknown PAM error"; 329 if (audit_submit(AUE_su, auid, EPERM, 1, 330 "pam_chauthtok: %s", aerr)) 331 errx(1, "Permission denied"); 332 #endif 333 syslog(LOG_ERR, "pam_chauthtok: %s", 334 pam_strerror(pamh, retcode)); 335 errx(1, "Sorry"); 336 } 337 } 338 if (retcode != PAM_SUCCESS) { 339 #ifdef USE_BSM_AUDIT 340 if (audit_submit(AUE_su, auid, EPERM, 1, "pam_acct_mgmt: %s", 341 pam_strerror(pamh, retcode))) 342 errx(1, "Permission denied"); 343 #endif 344 syslog(LOG_ERR, "pam_acct_mgmt: %s", 345 pam_strerror(pamh, retcode)); 346 errx(1, "Sorry"); 347 } 348 349 /* get target login information */ 350 if (class == NULL) 351 lc = login_getpwclass(pwd); 352 else { 353 if (ruid != 0) { 354 #ifdef USE_BSM_AUDIT 355 if (audit_submit(AUE_su, auid, EPERM, 1, 356 "only root may use -c")) 357 errx(1, "Permission denied"); 358 #endif 359 errx(1, "only root may use -c"); 360 } 361 lc = login_getclass(class); 362 if (lc == NULL) 363 err(1, "login_getclass"); 364 if (lc->lc_class == NULL || strcmp(class, lc->lc_class) != 0) 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 */ 479 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 480 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP | 481 LOGIN_SETMAC); 482 /* 483 * If -s is present, also set the MAC label. 484 */ 485 if (setmaclabel) 486 setwhat |= LOGIN_SETMAC; 487 /* 488 * Don't touch resource/priority settings if -m has been used 489 * or -l and -c hasn't, and we're not su'ing to root. 490 */ 491 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 492 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 493 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 494 err(1, "setusercontext"); 495 496 if (!asme) { 497 if (asthem) { 498 p = getenv("TERM"); 499 environ = &cleanenv; 500 } 501 502 if (asthem || pwd->pw_uid) 503 setenv("USER", pwd->pw_name, 1); 504 setenv("HOME", pwd->pw_dir, 1); 505 setenv("SHELL", shell, 1); 506 507 if (asthem) { 508 /* 509 * Add any environmental variables that the 510 * PAM modules may have set. 511 */ 512 environ_pam = pam_getenvlist(pamh); 513 if (environ_pam) 514 export_pam_environment(); 515 516 /* set the su'd user's environment & umask */ 517 setusercontext(lc, pwd, pwd->pw_uid, 518 LOGIN_SETPATH | LOGIN_SETUMASK | 519 LOGIN_SETENV); 520 if (p) 521 setenv("TERM", p, 1); 522 523 p = pam_getenv(pamh, "HOME"); 524 if (chdir(p ? p : pwd->pw_dir) < 0) 525 errx(1, "no directory"); 526 } 527 } 528 login_close(lc); 529 530 if (iscsh == YES) { 531 if (fastlogin) 532 *np.a-- = "-f"; 533 if (asme) 534 *np.a-- = "-m"; 535 } 536 /* csh strips the first character... */ 537 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 538 539 if (ruid != 0) 540 syslog(LOG_NOTICE, "%s to %s%s", username, user, 541 ontty()); 542 543 execv(shell, np.b); 544 err(1, "%s", shell); 545 } 546 } 547 548 static void 549 export_pam_environment(void) 550 { 551 char **pp; 552 char *p; 553 554 for (pp = environ_pam; *pp != NULL; pp++) { 555 if (ok_to_export(*pp)) { 556 p = strchr(*pp, '='); 557 *p = '\0'; 558 setenv(*pp, p + 1, 1); 559 } 560 free(*pp); 561 } 562 } 563 564 /* 565 * Sanity checks on PAM environmental variables: 566 * - Make sure there is an '=' in the string. 567 * - Make sure the string doesn't run on too long. 568 * - Do not export certain variables. This list was taken from the 569 * Solaris pam_putenv(3) man page. 570 * Note that if the user is chrooted, PAM may have a better idea than we 571 * do of where her home directory is. 572 */ 573 static int 574 ok_to_export(const char *s) 575 { 576 static const char *noexport[] = { 577 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 578 "IFS", "PATH", NULL 579 }; 580 const char **pp; 581 size_t n; 582 583 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 584 return 0; 585 if (strncmp(s, "LD_", 3) == 0) 586 return 0; 587 for (pp = noexport; *pp != NULL; pp++) { 588 n = strlen(*pp); 589 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 590 return 0; 591 } 592 return 1; 593 } 594 595 static void 596 usage(void) 597 { 598 599 fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n"); 600 exit(1); 601 /* NOTREACHED */ 602 } 603 604 static int 605 chshell(const char *sh) 606 { 607 int r; 608 char *cp; 609 610 r = 0; 611 setusershell(); 612 while ((cp = getusershell()) != NULL && !r) 613 r = (strcmp(cp, sh) == 0); 614 endusershell(); 615 return r; 616 } 617 618 static char * 619 ontty(void) 620 { 621 char *p; 622 static char buf[MAXPATHLEN + 4]; 623 624 buf[0] = 0; 625 p = ttyname(STDERR_FILENO); 626 if (p) 627 snprintf(buf, sizeof(buf), " on %s", p); 628 return buf; 629 } 630