su.c revision 330897
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 * 4. 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#ifndef lint 63static const char copyright[] = 64"@(#) Copyright (c) 1988, 1993, 1994\n\ 65 The Regents of the University of California. All rights reserved.\n"; 66#endif /* not lint */ 67 68#if 0 69#ifndef lint 70static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94"; 71#endif /* not lint */ 72#endif 73 74#include <sys/cdefs.h> 75__FBSDID("$FreeBSD: stable/11/usr.bin/su/su.c 330897 2018-03-14 03:19:51Z eadler $"); 76 77#include <sys/param.h> 78#include <sys/time.h> 79#include <sys/resource.h> 80#include <sys/wait.h> 81 82#ifdef USE_BSM_AUDIT 83#include <bsm/libbsm.h> 84#include <bsm/audit_uevents.h> 85#endif 86 87#include <err.h> 88#include <errno.h> 89#include <grp.h> 90#include <login_cap.h> 91#include <paths.h> 92#include <pwd.h> 93#include <signal.h> 94#include <stdio.h> 95#include <stdlib.h> 96#include <string.h> 97#include <syslog.h> 98#include <unistd.h> 99#include <stdarg.h> 100 101#include <security/pam_appl.h> 102#include <security/openpam.h> 103 104#define PAM_END() do { \ 105 int local_ret; \ 106 if (pamh != NULL) { \ 107 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 108 if (local_ret != PAM_SUCCESS) \ 109 syslog(LOG_ERR, "pam_setcred: %s", \ 110 pam_strerror(pamh, local_ret)); \ 111 if (asthem) { \ 112 local_ret = pam_close_session(pamh, 0); \ 113 if (local_ret != PAM_SUCCESS) \ 114 syslog(LOG_ERR, "pam_close_session: %s",\ 115 pam_strerror(pamh, local_ret)); \ 116 } \ 117 local_ret = pam_end(pamh, local_ret); \ 118 if (local_ret != PAM_SUCCESS) \ 119 syslog(LOG_ERR, "pam_end: %s", \ 120 pam_strerror(pamh, local_ret)); \ 121 } \ 122} while (0) 123 124 125#define PAM_SET_ITEM(what, item) do { \ 126 int local_ret; \ 127 local_ret = pam_set_item(pamh, what, item); \ 128 if (local_ret != PAM_SUCCESS) { \ 129 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 130 pam_strerror(pamh, local_ret)); \ 131 errx(1, "pam_set_item(" #what "): %s", \ 132 pam_strerror(pamh, local_ret)); \ 133 /* NOTREACHED */ \ 134 } \ 135} while (0) 136 137enum tristate { UNSET, YES, NO }; 138 139static pam_handle_t *pamh = NULL; 140static char **environ_pam; 141 142static char *ontty(void); 143static int chshell(const char *); 144static void usage(void) __dead2; 145static void export_pam_environment(void); 146static int ok_to_export(const char *); 147 148extern char **environ; 149 150int 151main(int argc, char *argv[]) 152{ 153 static char *cleanenv; 154 struct passwd *pwd = NULL; 155 struct pam_conv conv = { openpam_ttyconv, NULL }; 156 enum tristate iscsh; 157 login_cap_t *lc; 158 union { 159 const char **a; 160 char * const *b; 161 } np; 162 uid_t ruid; 163 pid_t child_pid, child_pgrp, pid; 164 int asme, ch, asthem, fastlogin, prio, i, retcode, 165 statusp, setmaclabel; 166 u_int setwhat; 167 char *username, *class, shellbuf[MAXPATHLEN]; 168 const char *p, *user, *shell, *mytty, **nargv; 169 const void *v; 170 struct sigaction sa, sa_int, sa_quit, sa_pipe; 171 int temp, fds[2]; 172#ifdef USE_BSM_AUDIT 173 const char *aerr; 174 au_id_t auid; 175#endif 176 177 p = shell = class = cleanenv = NULL; 178 asme = asthem = fastlogin = statusp = 0; 179 user = "root"; 180 iscsh = UNSET; 181 setmaclabel = 0; 182 183 while ((ch = getopt(argc, argv, "-flmsc:")) != -1) 184 switch ((char)ch) { 185 case 'f': 186 fastlogin = 1; 187 break; 188 case '-': 189 case 'l': 190 asme = 0; 191 asthem = 1; 192 break; 193 case 'm': 194 asme = 1; 195 asthem = 0; 196 break; 197 case 's': 198 setmaclabel = 1; 199 break; 200 case 'c': 201 class = optarg; 202 break; 203 case '?': 204 default: 205 usage(); 206 /* NOTREACHED */ 207 } 208 209 if (optind < argc) 210 user = argv[optind++]; 211 212 if (user == NULL) 213 usage(); 214 /* NOTREACHED */ 215 216 /* 217 * Try to provide more helpful debugging output if su(1) is running 218 * non-setuid, or was run from a file system not mounted setuid. 219 */ 220 if (geteuid() != 0) 221 errx(1, "not running setuid"); 222 223#ifdef USE_BSM_AUDIT 224 if (getauid(&auid) < 0 && errno != ENOSYS) { 225 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 226 errx(1, "Permission denied"); 227 } 228#endif 229 if (strlen(user) > MAXLOGNAME - 1) { 230#ifdef USE_BSM_AUDIT 231 if (audit_submit(AUE_su, auid, 232 EPERM, 1, "username too long: '%s'", user)) 233 errx(1, "Permission denied"); 234#endif 235 errx(1, "username too long"); 236 } 237 238 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 239 if (nargv == NULL) 240 errx(1, "malloc failure"); 241 242 nargv[argc + 3] = NULL; 243 for (i = argc; i >= optind; i--) 244 nargv[i + 3] = argv[i]; 245 np.a = &nargv[i + 3]; 246 247 argv += optind; 248 249 errno = 0; 250 prio = getpriority(PRIO_PROCESS, 0); 251 if (errno) 252 prio = 0; 253 254 setpriority(PRIO_PROCESS, 0, -2); 255 openlog("su", LOG_CONS, LOG_AUTH); 256 257 /* get current login name, real uid and shell */ 258 ruid = getuid(); 259 username = getlogin(); 260 if (username != NULL) 261 pwd = getpwnam(username); 262 if (pwd == NULL || pwd->pw_uid != ruid) 263 pwd = getpwuid(ruid); 264 if (pwd == NULL) { 265#ifdef USE_BSM_AUDIT 266 if (audit_submit(AUE_su, auid, EPERM, 1, 267 "unable to determine invoking subject: '%s'", username)) 268 errx(1, "Permission denied"); 269#endif 270 errx(1, "who are you?"); 271 } 272 273 username = strdup(pwd->pw_name); 274 if (username == NULL) 275 err(1, "strdup failure"); 276 277 if (asme) { 278 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 279 /* must copy - pwd memory is recycled */ 280 strlcpy(shellbuf, pwd->pw_shell, 281 sizeof(shellbuf)); 282 shell = shellbuf; 283 } 284 else { 285 shell = _PATH_BSHELL; 286 iscsh = NO; 287 } 288 } 289 290 /* Do the whole PAM startup thing */ 291 retcode = pam_start("su", user, &conv, &pamh); 292 if (retcode != PAM_SUCCESS) { 293 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 294 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 295 } 296 297 PAM_SET_ITEM(PAM_RUSER, username); 298 299 mytty = ttyname(STDERR_FILENO); 300 if (!mytty) 301 mytty = "tty"; 302 PAM_SET_ITEM(PAM_TTY, mytty); 303 304 retcode = pam_authenticate(pamh, 0); 305 if (retcode != PAM_SUCCESS) { 306#ifdef USE_BSM_AUDIT 307 if (audit_submit(AUE_su, auid, EPERM, 1, "bad su %s to %s on %s", 308 username, user, mytty)) 309 errx(1, "Permission denied"); 310#endif 311 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 312 username, user, mytty); 313 errx(1, "Sorry"); 314 } 315#ifdef USE_BSM_AUDIT 316 if (audit_submit(AUE_su, auid, 0, 0, "successful authentication")) 317 errx(1, "Permission denied"); 318#endif 319 retcode = pam_get_item(pamh, PAM_USER, &v); 320 if (retcode == PAM_SUCCESS) 321 user = v; 322 else 323 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 324 pam_strerror(pamh, retcode)); 325 pwd = getpwnam(user); 326 if (pwd == NULL) { 327#ifdef USE_BSM_AUDIT 328 if (audit_submit(AUE_su, auid, EPERM, 1, 329 "unknown subject: %s", user)) 330 errx(1, "Permission denied"); 331#endif 332 errx(1, "unknown login: %s", user); 333 } 334 335 retcode = pam_acct_mgmt(pamh, 0); 336 if (retcode == PAM_NEW_AUTHTOK_REQD) { 337 retcode = pam_chauthtok(pamh, 338 PAM_CHANGE_EXPIRED_AUTHTOK); 339 if (retcode != PAM_SUCCESS) { 340#ifdef USE_BSM_AUDIT 341 aerr = pam_strerror(pamh, retcode); 342 if (aerr == NULL) 343 aerr = "Unknown PAM error"; 344 if (audit_submit(AUE_su, auid, EPERM, 1, 345 "pam_chauthtok: %s", aerr)) 346 errx(1, "Permission denied"); 347#endif 348 syslog(LOG_ERR, "pam_chauthtok: %s", 349 pam_strerror(pamh, retcode)); 350 errx(1, "Sorry"); 351 } 352 } 353 if (retcode != PAM_SUCCESS) { 354#ifdef USE_BSM_AUDIT 355 if (audit_submit(AUE_su, auid, EPERM, 1, "pam_acct_mgmt: %s", 356 pam_strerror(pamh, retcode))) 357 errx(1, "Permission denied"); 358#endif 359 syslog(LOG_ERR, "pam_acct_mgmt: %s", 360 pam_strerror(pamh, retcode)); 361 errx(1, "Sorry"); 362 } 363 364 /* get target login information */ 365 if (class == NULL) 366 lc = login_getpwclass(pwd); 367 else { 368 if (ruid != 0) { 369#ifdef USE_BSM_AUDIT 370 if (audit_submit(AUE_su, auid, EPERM, 1, 371 "only root may use -c")) 372 errx(1, "Permission denied"); 373#endif 374 errx(1, "only root may use -c"); 375 } 376 lc = login_getclass(class); 377 if (lc == NULL) 378 err(1, "login_getclass"); 379 if (lc->lc_class == NULL || strcmp(class, lc->lc_class) != 0) 380 errx(1, "unknown class: %s", class); 381 } 382 383 /* if asme and non-standard target shell, must be root */ 384 if (asme) { 385 if (ruid != 0 && !chshell(pwd->pw_shell)) 386 errx(1, "permission denied (shell)"); 387 } 388 else if (pwd->pw_shell && *pwd->pw_shell) { 389 shell = pwd->pw_shell; 390 iscsh = UNSET; 391 } 392 else { 393 shell = _PATH_BSHELL; 394 iscsh = NO; 395 } 396 397 /* if we're forking a csh, we want to slightly muck the args */ 398 if (iscsh == UNSET) { 399 p = strrchr(shell, '/'); 400 if (p) 401 ++p; 402 else 403 p = shell; 404 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 405 } 406 setpriority(PRIO_PROCESS, 0, prio); 407 408 /* 409 * PAM modules might add supplementary groups in pam_setcred(), so 410 * initialize them first. 411 */ 412 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 413 err(1, "setusercontext"); 414 415 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 416 if (retcode != PAM_SUCCESS) { 417 syslog(LOG_ERR, "pam_setcred: %s", 418 pam_strerror(pamh, retcode)); 419 errx(1, "failed to establish credentials."); 420 } 421 if (asthem) { 422 retcode = pam_open_session(pamh, 0); 423 if (retcode != PAM_SUCCESS) { 424 syslog(LOG_ERR, "pam_open_session: %s", 425 pam_strerror(pamh, retcode)); 426 errx(1, "failed to open session."); 427 } 428 } 429 430 /* 431 * We must fork() before setuid() because we need to call 432 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 433 */ 434 sa.sa_flags = SA_RESTART; 435 sa.sa_handler = SIG_IGN; 436 sigemptyset(&sa.sa_mask); 437 sigaction(SIGINT, &sa, &sa_int); 438 sigaction(SIGQUIT, &sa, &sa_quit); 439 sigaction(SIGPIPE, &sa, &sa_pipe); 440 sa.sa_handler = SIG_DFL; 441 sigaction(SIGTSTP, &sa, NULL); 442 statusp = 1; 443 if (pipe(fds) == -1) { 444 PAM_END(); 445 err(1, "pipe"); 446 } 447 child_pid = fork(); 448 switch (child_pid) { 449 default: 450 sa.sa_handler = SIG_IGN; 451 sigaction(SIGTTOU, &sa, NULL); 452 close(fds[0]); 453 setpgid(child_pid, child_pid); 454 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) 455 tcsetpgrp(STDERR_FILENO, child_pid); 456 close(fds[1]); 457 sigaction(SIGPIPE, &sa_pipe, NULL); 458 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 459 if (WIFSTOPPED(statusp)) { 460 child_pgrp = getpgid(child_pid); 461 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 462 tcsetpgrp(STDERR_FILENO, getpgrp()); 463 kill(getpid(), SIGSTOP); 464 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) { 465 child_pgrp = getpgid(child_pid); 466 tcsetpgrp(STDERR_FILENO, child_pgrp); 467 } 468 kill(child_pid, SIGCONT); 469 statusp = 1; 470 continue; 471 } 472 break; 473 } 474 tcsetpgrp(STDERR_FILENO, getpgrp()); 475 if (pid == -1) 476 err(1, "waitpid"); 477 PAM_END(); 478 exit(WEXITSTATUS(statusp)); 479 case -1: 480 PAM_END(); 481 err(1, "fork"); 482 case 0: 483 close(fds[1]); 484 read(fds[0], &temp, 1); 485 close(fds[0]); 486 sigaction(SIGPIPE, &sa_pipe, NULL); 487 sigaction(SIGINT, &sa_int, NULL); 488 sigaction(SIGQUIT, &sa_quit, NULL); 489 490 /* 491 * Set all user context except for: Environmental variables 492 * Umask Login records (wtmp, etc) Path 493 */ 494 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 495 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP | 496 LOGIN_SETMAC); 497 /* 498 * If -s is present, also set the MAC label. 499 */ 500 if (setmaclabel) 501 setwhat |= LOGIN_SETMAC; 502 /* 503 * Don't touch resource/priority settings if -m has been used 504 * or -l and -c hasn't, and we're not su'ing to root. 505 */ 506 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 507 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 508 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 509 err(1, "setusercontext"); 510 511 if (!asme) { 512 if (asthem) { 513 p = getenv("TERM"); 514 environ = &cleanenv; 515 } 516 517 if (asthem || pwd->pw_uid) 518 setenv("USER", pwd->pw_name, 1); 519 setenv("HOME", pwd->pw_dir, 1); 520 setenv("SHELL", shell, 1); 521 522 if (asthem) { 523 /* 524 * Add any environmental variables that the 525 * PAM modules may have set. 526 */ 527 environ_pam = pam_getenvlist(pamh); 528 if (environ_pam) 529 export_pam_environment(); 530 531 /* set the su'd user's environment & umask */ 532 setusercontext(lc, pwd, pwd->pw_uid, 533 LOGIN_SETPATH | LOGIN_SETUMASK | 534 LOGIN_SETENV); 535 if (p) 536 setenv("TERM", p, 1); 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 563static void 564export_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 setenv(*pp, p + 1, 1); 574 } 575 free(*pp); 576 } 577} 578 579/* 580 * Sanity checks on PAM environmental variables: 581 * - Make sure there is an '=' in the string. 582 * - Make sure the string doesn't run on too long. 583 * - Do not export certain variables. This list was taken from the 584 * Solaris pam_putenv(3) man page. 585 * Note that if the user is chrooted, PAM may have a better idea than we 586 * do of where her home directory is. 587 */ 588static int 589ok_to_export(const char *s) 590{ 591 static const char *noexport[] = { 592 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 593 "IFS", "PATH", NULL 594 }; 595 const char **pp; 596 size_t n; 597 598 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 599 return 0; 600 if (strncmp(s, "LD_", 3) == 0) 601 return 0; 602 for (pp = noexport; *pp != NULL; pp++) { 603 n = strlen(*pp); 604 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 605 return 0; 606 } 607 return 1; 608} 609 610static void 611usage(void) 612{ 613 614 fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n"); 615 exit(1); 616 /* NOTREACHED */ 617} 618 619static int 620chshell(const char *sh) 621{ 622 int r; 623 char *cp; 624 625 r = 0; 626 setusershell(); 627 while ((cp = getusershell()) != NULL && !r) 628 r = (strcmp(cp, sh) == 0); 629 endusershell(); 630 return r; 631} 632 633static char * 634ontty(void) 635{ 636 char *p; 637 static char buf[MAXPATHLEN + 4]; 638 639 buf[0] = 0; 640 p = ttyname(STDERR_FILENO); 641 if (p) 642 snprintf(buf, sizeof(buf), " on %s", p); 643 return buf; 644} 645