su.c revision 169177
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 169177 2007-05-01 16:02:44Z ache $"); 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 struct sigaction sa, sa_int, sa_quit, sa_pipe; 172 int temp, fds[2]; 173#ifdef USE_BSM_AUDIT 174 const char *aerr; 175 au_id_t auid; 176#endif 177 178 shell = class = cleanenv = NULL; 179 asme = asthem = fastlogin = statusp = 0; 180 user = "root"; 181 iscsh = UNSET; 182 setmaclabel = 0; 183 184 while ((ch = getopt(argc, argv, "-flmsc:")) != -1) 185 switch ((char)ch) { 186 case 'f': 187 fastlogin = 1; 188 break; 189 case '-': 190 case 'l': 191 asme = 0; 192 asthem = 1; 193 break; 194 case 'm': 195 asme = 1; 196 asthem = 0; 197 break; 198 case 's': 199 setmaclabel = 1; 200 break; 201 case 'c': 202 class = optarg; 203 break; 204 case '?': 205 default: 206 usage(); 207 /* NOTREACHED */ 208 } 209 210 if (optind < argc) 211 user = argv[optind++]; 212 213 if (user == NULL) 214 usage(); 215 /* NOTREACHED */ 216 217 /* 218 * Try to provide more helpful debugging output if su(1) is running 219 * non-setuid, or was run from a file system not mounted setuid. 220 */ 221 if (geteuid() != 0) 222 errx(1, "not running setuid"); 223 224#ifdef USE_BSM_AUDIT 225 if (getauid(&auid) < 0 && errno != ENOSYS) { 226 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 227 errx(1, "Permission denied"); 228 } 229#endif 230 if (strlen(user) > MAXLOGNAME - 1) { 231#ifdef USE_BSM_AUDIT 232 if (audit_submit(AUE_su, auid, 233 1, EPERM, "username too long: '%s'", user)) 234 errx(1, "Permission denied"); 235#endif 236 errx(1, "username too long"); 237 } 238 239 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 240 if (nargv == NULL) 241 errx(1, "malloc failure"); 242 243 nargv[argc + 3] = NULL; 244 for (i = argc; i >= optind; i--) 245 nargv[i + 3] = argv[i]; 246 np.a = &nargv[i + 3]; 247 248 argv += optind; 249 250 errno = 0; 251 prio = getpriority(PRIO_PROCESS, 0); 252 if (errno) 253 prio = 0; 254 255 setpriority(PRIO_PROCESS, 0, -2); 256 openlog("su", LOG_CONS, LOG_AUTH); 257 258 /* get current login name, real uid and shell */ 259 ruid = getuid(); 260 username = getlogin(); 261 pwd = getpwnam(username); 262 if (username == NULL || 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, 1, EPERM, 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 shell = strncpy(shellbuf, pwd->pw_shell, 281 sizeof(shellbuf)); 282 shellbuf[sizeof(shellbuf) - 1] = '\0'; 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, 1, EPERM, "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, (const void **)&p); 320 if (retcode == PAM_SUCCESS) 321 user = p; 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, 1, EPERM, 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, 1, EPERM, 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, 1, EPERM, "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, 1, EPERM, 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 errx(1, "unknown class: %s", class); 379 } 380 381 /* if asme and non-standard target shell, must be root */ 382 if (asme) { 383 if (ruid != 0 && !chshell(pwd->pw_shell)) 384 errx(1, "permission denied (shell)"); 385 } 386 else if (pwd->pw_shell && *pwd->pw_shell) { 387 shell = pwd->pw_shell; 388 iscsh = UNSET; 389 } 390 else { 391 shell = _PATH_BSHELL; 392 iscsh = NO; 393 } 394 395 /* if we're forking a csh, we want to slightly muck the args */ 396 if (iscsh == UNSET) { 397 p = strrchr(shell, '/'); 398 if (p) 399 ++p; 400 else 401 p = shell; 402 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 403 } 404 setpriority(PRIO_PROCESS, 0, prio); 405 406 /* 407 * PAM modules might add supplementary groups in pam_setcred(), so 408 * initialize them first. 409 */ 410 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 411 err(1, "setusercontext"); 412 413 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 414 if (retcode != PAM_SUCCESS) { 415 syslog(LOG_ERR, "pam_setcred: %s", 416 pam_strerror(pamh, retcode)); 417 errx(1, "failed to establish credentials."); 418 } 419 if (asthem) { 420 retcode = pam_open_session(pamh, 0); 421 if (retcode != PAM_SUCCESS) { 422 syslog(LOG_ERR, "pam_open_session: %s", 423 pam_strerror(pamh, retcode)); 424 errx(1, "failed to open session."); 425 } 426 } 427 428 /* 429 * We must fork() before setuid() because we need to call 430 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 431 */ 432 sa.sa_flags = SA_RESTART; 433 sa.sa_handler = SIG_IGN; 434 sigemptyset(&sa.sa_mask); 435 sigaction(SIGINT, &sa, &sa_int); 436 sigaction(SIGQUIT, &sa, &sa_quit); 437 sigaction(SIGPIPE, &sa, &sa_pipe); 438 sa.sa_handler = SIG_DFL; 439 sigaction(SIGTSTP, &sa, NULL); 440 statusp = 1; 441 if (pipe(fds) == -1) { 442 PAM_END(); 443 err(1, "pipe"); 444 } 445 child_pid = fork(); 446 switch (child_pid) { 447 default: 448 sa.sa_handler = SIG_IGN; 449 sigaction(SIGTTOU, &sa, NULL); 450 close(fds[0]); 451 setpgid(child_pid, child_pid); 452 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) 453 tcsetpgrp(STDERR_FILENO, child_pid); 454 close(fds[1]); 455 sigaction(SIGPIPE, &sa_pipe, NULL); 456 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 457 if (WIFSTOPPED(statusp)) { 458 child_pgrp = getpgid(child_pid); 459 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 460 tcsetpgrp(STDERR_FILENO, getpgrp()); 461 kill(getpid(), SIGSTOP); 462 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) { 463 child_pgrp = getpgid(child_pid); 464 tcsetpgrp(STDERR_FILENO, child_pgrp); 465 } 466 kill(child_pid, SIGCONT); 467 statusp = 1; 468 continue; 469 } 470 break; 471 } 472 child_pgrp = getpgid(child_pid); 473 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 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; 567 568 for (pp = environ_pam; *pp != NULL; pp++) { 569 if (ok_to_export(*pp)) 570 putenv(*pp); 571 free(*pp); 572 } 573} 574 575/* 576 * Sanity checks on PAM environmental variables: 577 * - Make sure there is an '=' in the string. 578 * - Make sure the string doesn't run on too long. 579 * - Do not export certain variables. This list was taken from the 580 * Solaris pam_putenv(3) man page. 581 * Note that if the user is chrooted, PAM may have a better idea than we 582 * do of where her home directory is. 583 */ 584static int 585ok_to_export(const char *s) 586{ 587 static const char *noexport[] = { 588 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 589 "IFS", "PATH", NULL 590 }; 591 const char **pp; 592 size_t n; 593 594 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 595 return 0; 596 if (strncmp(s, "LD_", 3) == 0) 597 return 0; 598 for (pp = noexport; *pp != NULL; pp++) { 599 n = strlen(*pp); 600 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 601 return 0; 602 } 603 return 1; 604} 605 606static void 607usage(void) 608{ 609 610 fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n"); 611 exit(1); 612 /* NOTREACHED */ 613} 614 615static int 616chshell(const char *sh) 617{ 618 int r; 619 char *cp; 620 621 r = 0; 622 setusershell(); 623 while ((cp = getusershell()) != NULL && !r) 624 r = (strcmp(cp, sh) == 0); 625 endusershell(); 626 return r; 627} 628 629static char * 630ontty(void) 631{ 632 char *p; 633 static char buf[MAXPATHLEN + 4]; 634 635 buf[0] = 0; 636 p = ttyname(STDERR_FILENO); 637 if (p) 638 snprintf(buf, sizeof(buf), " on %s", p); 639 return buf; 640} 641