su.c revision 190700
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. All advertising materials mentioning features or use of this software 44 * must display the following acknowledgement: 45 * This product includes software developed by the University of 46 * California, Berkeley and its contributors. 47 * 4. Neither the name of the University nor the names of its contributors 48 * may be used to endorse or promote products derived from this software 49 * without specific prior written permission. 50 * 51 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 52 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 53 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 54 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 55 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 56 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 57 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 58 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 59 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 60 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 61 * SUCH DAMAGE. 62 */ 63 64#ifndef lint 65static const char copyright[] = 66"@(#) Copyright (c) 1988, 1993, 1994\n\ 67 The Regents of the University of California. All rights reserved.\n"; 68#endif /* not lint */ 69 70#if 0 71#ifndef lint 72static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94"; 73#endif /* not lint */ 74#endif 75 76#include <sys/cdefs.h> 77__FBSDID("$FreeBSD: head/usr.bin/su/su.c 190700 2009-04-04 20:58:18Z csjp $"); 78 79#include <sys/param.h> 80#include <sys/time.h> 81#include <sys/resource.h> 82#include <sys/wait.h> 83 84#ifdef USE_BSM_AUDIT 85#include <bsm/libbsm.h> 86#include <bsm/audit_uevents.h> 87#endif 88 89#include <err.h> 90#include <errno.h> 91#include <grp.h> 92#include <login_cap.h> 93#include <paths.h> 94#include <pwd.h> 95#include <signal.h> 96#include <stdio.h> 97#include <stdlib.h> 98#include <string.h> 99#include <syslog.h> 100#include <unistd.h> 101#include <stdarg.h> 102 103#include <security/pam_appl.h> 104#include <security/openpam.h> 105 106#define PAM_END() do { \ 107 int local_ret; \ 108 if (pamh != NULL) { \ 109 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 110 if (local_ret != PAM_SUCCESS) \ 111 syslog(LOG_ERR, "pam_setcred: %s", \ 112 pam_strerror(pamh, local_ret)); \ 113 if (asthem) { \ 114 local_ret = pam_close_session(pamh, 0); \ 115 if (local_ret != PAM_SUCCESS) \ 116 syslog(LOG_ERR, "pam_close_session: %s",\ 117 pam_strerror(pamh, local_ret)); \ 118 } \ 119 local_ret = pam_end(pamh, local_ret); \ 120 if (local_ret != PAM_SUCCESS) \ 121 syslog(LOG_ERR, "pam_end: %s", \ 122 pam_strerror(pamh, local_ret)); \ 123 } \ 124} while (0) 125 126 127#define PAM_SET_ITEM(what, item) do { \ 128 int local_ret; \ 129 local_ret = pam_set_item(pamh, what, item); \ 130 if (local_ret != PAM_SUCCESS) { \ 131 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 132 pam_strerror(pamh, local_ret)); \ 133 errx(1, "pam_set_item(" #what "): %s", \ 134 pam_strerror(pamh, local_ret)); \ 135 /* NOTREACHED */ \ 136 } \ 137} while (0) 138 139enum tristate { UNSET, YES, NO }; 140 141static pam_handle_t *pamh = NULL; 142static char **environ_pam; 143 144static char *ontty(void); 145static int chshell(const char *); 146static void usage(void) __dead2; 147static void export_pam_environment(void); 148static int ok_to_export(const char *); 149 150extern char **environ; 151 152int 153main(int argc, char *argv[]) 154{ 155 static char *cleanenv; 156 struct passwd *pwd; 157 struct pam_conv conv = { openpam_ttyconv, NULL }; 158 enum tristate iscsh; 159 login_cap_t *lc; 160 union { 161 const char **a; 162 char * const *b; 163 } np; 164 uid_t ruid; 165 pid_t child_pid, child_pgrp, pid; 166 int asme, ch, asthem, fastlogin, prio, i, retcode, 167 statusp, setmaclabel; 168 u_int setwhat; 169 char *username, *class, shellbuf[MAXPATHLEN]; 170 const char *p, *user, *shell, *mytty, **nargv; 171 const void *v; 172 struct sigaction sa, sa_int, sa_quit, sa_pipe; 173 int temp, fds[2]; 174#ifdef USE_BSM_AUDIT 175 const char *aerr; 176 au_id_t auid; 177#endif 178 179 shell = class = cleanenv = NULL; 180 asme = asthem = fastlogin = statusp = 0; 181 user = "root"; 182 iscsh = UNSET; 183 setmaclabel = 0; 184 185 while ((ch = getopt(argc, argv, "-flmsc:")) != -1) 186 switch ((char)ch) { 187 case 'f': 188 fastlogin = 1; 189 break; 190 case '-': 191 case 'l': 192 asme = 0; 193 asthem = 1; 194 break; 195 case 'm': 196 asme = 1; 197 asthem = 0; 198 break; 199 case 's': 200 setmaclabel = 1; 201 break; 202 case 'c': 203 class = optarg; 204 break; 205 case '?': 206 default: 207 usage(); 208 /* NOTREACHED */ 209 } 210 211 if (optind < argc) 212 user = argv[optind++]; 213 214 if (user == NULL) 215 usage(); 216 /* NOTREACHED */ 217 218 /* 219 * Try to provide more helpful debugging output if su(1) is running 220 * non-setuid, or was run from a file system not mounted setuid. 221 */ 222 if (geteuid() != 0) 223 errx(1, "not running setuid"); 224 225#ifdef USE_BSM_AUDIT 226 if (getauid(&auid) < 0 && errno != ENOSYS) { 227 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 228 errx(1, "Permission denied"); 229 } 230#endif 231 if (strlen(user) > MAXLOGNAME - 1) { 232#ifdef USE_BSM_AUDIT 233 if (audit_submit(AUE_su, auid, 234 EPERM, 1, "username too long: '%s'", user)) 235 errx(1, "Permission denied"); 236#endif 237 errx(1, "username too long"); 238 } 239 240 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 241 if (nargv == NULL) 242 errx(1, "malloc failure"); 243 244 nargv[argc + 3] = NULL; 245 for (i = argc; i >= optind; i--) 246 nargv[i + 3] = argv[i]; 247 np.a = &nargv[i + 3]; 248 249 argv += optind; 250 251 errno = 0; 252 prio = getpriority(PRIO_PROCESS, 0); 253 if (errno) 254 prio = 0; 255 256 setpriority(PRIO_PROCESS, 0, -2); 257 openlog("su", LOG_CONS, LOG_AUTH); 258 259 /* get current login name, real uid and shell */ 260 ruid = getuid(); 261 username = getlogin(); 262 pwd = getpwnam(username); 263 if (username == NULL || pwd == NULL || pwd->pw_uid != ruid) 264 pwd = getpwuid(ruid); 265 if (pwd == NULL) { 266#ifdef USE_BSM_AUDIT 267 if (audit_submit(AUE_su, auid, EPERM, 1, 268 "unable to determine invoking subject: '%s'", username)) 269 errx(1, "Permission denied"); 270#endif 271 errx(1, "who are you?"); 272 } 273 274 username = strdup(pwd->pw_name); 275 if (username == NULL) 276 err(1, "strdup failure"); 277 278 if (asme) { 279 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 280 /* must copy - pwd memory is recycled */ 281 shell = strncpy(shellbuf, pwd->pw_shell, 282 sizeof(shellbuf)); 283 shellbuf[sizeof(shellbuf) - 1] = '\0'; 284 } 285 else { 286 shell = _PATH_BSHELL; 287 iscsh = NO; 288 } 289 } 290 291 /* Do the whole PAM startup thing */ 292 retcode = pam_start("su", user, &conv, &pamh); 293 if (retcode != PAM_SUCCESS) { 294 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 295 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 296 } 297 298 PAM_SET_ITEM(PAM_RUSER, username); 299 300 mytty = ttyname(STDERR_FILENO); 301 if (!mytty) 302 mytty = "tty"; 303 PAM_SET_ITEM(PAM_TTY, mytty); 304 305 retcode = pam_authenticate(pamh, 0); 306 if (retcode != PAM_SUCCESS) { 307#ifdef USE_BSM_AUDIT 308 if (audit_submit(AUE_su, auid, EPERM, 1, "bad su %s to %s on %s", 309 username, user, mytty)) 310 errx(1, "Permission denied"); 311#endif 312 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 313 username, user, mytty); 314 errx(1, "Sorry"); 315 } 316#ifdef USE_BSM_AUDIT 317 if (audit_submit(AUE_su, auid, 0, 0, "successful authentication")) 318 errx(1, "Permission denied"); 319#endif 320 retcode = pam_get_item(pamh, PAM_USER, &v); 321 if (retcode == PAM_SUCCESS) 322 user = v; 323 else 324 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 325 pam_strerror(pamh, retcode)); 326 pwd = getpwnam(user); 327 if (pwd == NULL) { 328#ifdef USE_BSM_AUDIT 329 if (audit_submit(AUE_su, auid, EPERM, 1, 330 "unknown subject: %s", user)) 331 errx(1, "Permission denied"); 332#endif 333 errx(1, "unknown login: %s", user); 334 } 335 336 retcode = pam_acct_mgmt(pamh, 0); 337 if (retcode == PAM_NEW_AUTHTOK_REQD) { 338 retcode = pam_chauthtok(pamh, 339 PAM_CHANGE_EXPIRED_AUTHTOK); 340 if (retcode != PAM_SUCCESS) { 341#ifdef USE_BSM_AUDIT 342 aerr = pam_strerror(pamh, retcode); 343 if (aerr == NULL) 344 aerr = "Unknown PAM error"; 345 if (audit_submit(AUE_su, auid, EPERM, 1, 346 "pam_chauthtok: %s", aerr)) 347 errx(1, "Permission denied"); 348#endif 349 syslog(LOG_ERR, "pam_chauthtok: %s", 350 pam_strerror(pamh, retcode)); 351 errx(1, "Sorry"); 352 } 353 } 354 if (retcode != PAM_SUCCESS) { 355#ifdef USE_BSM_AUDIT 356 if (audit_submit(AUE_su, auid, EPERM, 1, "pam_acct_mgmt: %s", 357 pam_strerror(pamh, retcode))) 358 errx(1, "Permission denied"); 359#endif 360 syslog(LOG_ERR, "pam_acct_mgmt: %s", 361 pam_strerror(pamh, retcode)); 362 errx(1, "Sorry"); 363 } 364 365 /* get target login information */ 366 if (class == NULL) 367 lc = login_getpwclass(pwd); 368 else { 369 if (ruid != 0) { 370#ifdef USE_BSM_AUDIT 371 if (audit_submit(AUE_su, auid, EPERM, 1, 372 "only root may use -c")) 373 errx(1, "Permission denied"); 374#endif 375 errx(1, "only root may use -c"); 376 } 377 lc = login_getclass(class); 378 if (lc == NULL) 379 errx(1, "unknown class: %s", class); 380 } 381 382 /* if asme and non-standard target shell, must be root */ 383 if (asme) { 384 if (ruid != 0 && !chshell(pwd->pw_shell)) 385 errx(1, "permission denied (shell)"); 386 } 387 else if (pwd->pw_shell && *pwd->pw_shell) { 388 shell = pwd->pw_shell; 389 iscsh = UNSET; 390 } 391 else { 392 shell = _PATH_BSHELL; 393 iscsh = NO; 394 } 395 396 /* if we're forking a csh, we want to slightly muck the args */ 397 if (iscsh == UNSET) { 398 p = strrchr(shell, '/'); 399 if (p) 400 ++p; 401 else 402 p = shell; 403 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 404 } 405 setpriority(PRIO_PROCESS, 0, prio); 406 407 /* 408 * PAM modules might add supplementary groups in pam_setcred(), so 409 * initialize them first. 410 */ 411 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 412 err(1, "setusercontext"); 413 414 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 415 if (retcode != PAM_SUCCESS) { 416 syslog(LOG_ERR, "pam_setcred: %s", 417 pam_strerror(pamh, retcode)); 418 errx(1, "failed to establish credentials."); 419 } 420 if (asthem) { 421 retcode = pam_open_session(pamh, 0); 422 if (retcode != PAM_SUCCESS) { 423 syslog(LOG_ERR, "pam_open_session: %s", 424 pam_strerror(pamh, retcode)); 425 errx(1, "failed to open session."); 426 } 427 } 428 429 /* 430 * We must fork() before setuid() because we need to call 431 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 432 */ 433 sa.sa_flags = SA_RESTART; 434 sa.sa_handler = SIG_IGN; 435 sigemptyset(&sa.sa_mask); 436 sigaction(SIGINT, &sa, &sa_int); 437 sigaction(SIGQUIT, &sa, &sa_quit); 438 sigaction(SIGPIPE, &sa, &sa_pipe); 439 sa.sa_handler = SIG_DFL; 440 sigaction(SIGTSTP, &sa, NULL); 441 statusp = 1; 442 if (pipe(fds) == -1) { 443 PAM_END(); 444 err(1, "pipe"); 445 } 446 child_pid = fork(); 447 switch (child_pid) { 448 default: 449 sa.sa_handler = SIG_IGN; 450 sigaction(SIGTTOU, &sa, NULL); 451 close(fds[0]); 452 setpgid(child_pid, child_pid); 453 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) 454 tcsetpgrp(STDERR_FILENO, child_pid); 455 close(fds[1]); 456 sigaction(SIGPIPE, &sa_pipe, NULL); 457 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 458 if (WIFSTOPPED(statusp)) { 459 child_pgrp = getpgid(child_pid); 460 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 461 tcsetpgrp(STDERR_FILENO, getpgrp()); 462 kill(getpid(), SIGSTOP); 463 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) { 464 child_pgrp = getpgid(child_pid); 465 tcsetpgrp(STDERR_FILENO, child_pgrp); 466 } 467 kill(child_pid, SIGCONT); 468 statusp = 1; 469 continue; 470 } 471 break; 472 } 473 tcsetpgrp(STDERR_FILENO, getpgrp()); 474 if (pid == -1) 475 err(1, "waitpid"); 476 PAM_END(); 477 exit(WEXITSTATUS(statusp)); 478 case -1: 479 PAM_END(); 480 err(1, "fork"); 481 case 0: 482 close(fds[1]); 483 read(fds[0], &temp, 1); 484 close(fds[0]); 485 sigaction(SIGPIPE, &sa_pipe, NULL); 486 sigaction(SIGINT, &sa_int, NULL); 487 sigaction(SIGQUIT, &sa_quit, NULL); 488 489 /* 490 * Set all user context except for: Environmental variables 491 * Umask Login records (wtmp, etc) Path 492 */ 493 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 494 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP | 495 LOGIN_SETMAC); 496 /* 497 * If -s is present, also set the MAC label. 498 */ 499 if (setmaclabel) 500 setwhat |= LOGIN_SETMAC; 501 /* 502 * Don't touch resource/priority settings if -m has been used 503 * or -l and -c hasn't, and we're not su'ing to root. 504 */ 505 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 506 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 507 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 508 err(1, "setusercontext"); 509 510 if (!asme) { 511 if (asthem) { 512 p = getenv("TERM"); 513 environ = &cleanenv; 514 } 515 516 if (asthem || pwd->pw_uid) 517 setenv("USER", pwd->pw_name, 1); 518 setenv("HOME", pwd->pw_dir, 1); 519 setenv("SHELL", shell, 1); 520 521 if (asthem) { 522 /* 523 * Add any environmental variables that the 524 * PAM modules may have set. 525 */ 526 environ_pam = pam_getenvlist(pamh); 527 if (environ_pam) 528 export_pam_environment(); 529 530 /* set the su'd user's environment & umask */ 531 setusercontext(lc, pwd, pwd->pw_uid, 532 LOGIN_SETPATH | LOGIN_SETUMASK | 533 LOGIN_SETENV); 534 if (p) 535 setenv("TERM", p, 1); 536 537 p = pam_getenv(pamh, "HOME"); 538 if (chdir(p ? p : pwd->pw_dir) < 0) 539 errx(1, "no directory"); 540 } 541 } 542 login_close(lc); 543 544 if (iscsh == YES) { 545 if (fastlogin) 546 *np.a-- = "-f"; 547 if (asme) 548 *np.a-- = "-m"; 549 } 550 /* csh strips the first character... */ 551 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 552 553 if (ruid != 0) 554 syslog(LOG_NOTICE, "%s to %s%s", username, user, 555 ontty()); 556 557 execv(shell, np.b); 558 err(1, "%s", shell); 559 } 560} 561 562static void 563export_pam_environment(void) 564{ 565 char **pp; 566 char *p; 567 568 for (pp = environ_pam; *pp != NULL; pp++) { 569 if (ok_to_export(*pp)) { 570 p = strchr(*pp, '='); 571 *p = '\0'; 572 setenv(*pp, p + 1, 1); 573 } 574 free(*pp); 575 } 576} 577 578/* 579 * Sanity checks on PAM environmental variables: 580 * - Make sure there is an '=' in the string. 581 * - Make sure the string doesn't run on too long. 582 * - Do not export certain variables. This list was taken from the 583 * Solaris pam_putenv(3) man page. 584 * Note that if the user is chrooted, PAM may have a better idea than we 585 * do of where her home directory is. 586 */ 587static int 588ok_to_export(const char *s) 589{ 590 static const char *noexport[] = { 591 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 592 "IFS", "PATH", NULL 593 }; 594 const char **pp; 595 size_t n; 596 597 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 598 return 0; 599 if (strncmp(s, "LD_", 3) == 0) 600 return 0; 601 for (pp = noexport; *pp != NULL; pp++) { 602 n = strlen(*pp); 603 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 604 return 0; 605 } 606 return 1; 607} 608 609static void 610usage(void) 611{ 612 613 fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n"); 614 exit(1); 615 /* NOTREACHED */ 616} 617 618static int 619chshell(const char *sh) 620{ 621 int r; 622 char *cp; 623 624 r = 0; 625 setusershell(); 626 while ((cp = getusershell()) != NULL && !r) 627 r = (strcmp(cp, sh) == 0); 628 endusershell(); 629 return r; 630} 631 632static char * 633ontty(void) 634{ 635 char *p; 636 static char buf[MAXPATHLEN + 4]; 637 638 buf[0] = 0; 639 p = ttyname(STDERR_FILENO); 640 if (p) 641 snprintf(buf, sizeof(buf), " on %s", p); 642 return buf; 643} 644