su.c revision 153966
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 153966 2006-01-02 09:46:38Z brian $"); 78 79#include <sys/param.h> 80#include <sys/time.h> 81#include <sys/resource.h> 82#include <sys/wait.h> 83 84#include <err.h> 85#include <errno.h> 86#include <grp.h> 87#include <login_cap.h> 88#include <paths.h> 89#include <pwd.h> 90#include <signal.h> 91#include <stdio.h> 92#include <stdlib.h> 93#include <string.h> 94#include <syslog.h> 95#include <unistd.h> 96 97#include <security/pam_appl.h> 98#include <security/openpam.h> 99 100#define PAM_END() do { \ 101 int local_ret; \ 102 if (pamh != NULL) { \ 103 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 104 if (local_ret != PAM_SUCCESS) \ 105 syslog(LOG_ERR, "pam_setcred: %s", \ 106 pam_strerror(pamh, local_ret)); \ 107 if (asthem) { \ 108 local_ret = pam_close_session(pamh, 0); \ 109 if (local_ret != PAM_SUCCESS) \ 110 syslog(LOG_ERR, "pam_close_session: %s",\ 111 pam_strerror(pamh, local_ret)); \ 112 } \ 113 local_ret = pam_end(pamh, local_ret); \ 114 if (local_ret != PAM_SUCCESS) \ 115 syslog(LOG_ERR, "pam_end: %s", \ 116 pam_strerror(pamh, local_ret)); \ 117 } \ 118} while (0) 119 120 121#define PAM_SET_ITEM(what, item) do { \ 122 int local_ret; \ 123 local_ret = pam_set_item(pamh, what, item); \ 124 if (local_ret != PAM_SUCCESS) { \ 125 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 126 pam_strerror(pamh, local_ret)); \ 127 errx(1, "pam_set_item(" #what "): %s", \ 128 pam_strerror(pamh, local_ret)); \ 129 /* NOTREACHED */ \ 130 } \ 131} while (0) 132 133enum tristate { UNSET, YES, NO }; 134 135static pam_handle_t *pamh = NULL; 136static char **environ_pam; 137 138static char *ontty(void); 139static int chshell(const char *); 140static void usage(void) __dead2; 141static void export_pam_environment(void); 142static int ok_to_export(const char *); 143 144extern char **environ; 145 146int 147main(int argc, char *argv[]) 148{ 149 static char *cleanenv; 150 struct passwd *pwd; 151 struct pam_conv conv = { openpam_ttyconv, NULL }; 152 enum tristate iscsh; 153 login_cap_t *lc; 154 union { 155 const char **a; 156 char * const *b; 157 } np; 158 uid_t ruid; 159 pid_t child_pid, pid; 160 int asme, ch, asthem, fastlogin, prio, i, retcode, 161 statusp, setmaclabel; 162 u_int setwhat; 163 char *username, *class, shellbuf[MAXPATHLEN]; 164 const char *p, *user, *shell, *mytty, **nargv; 165 struct sigaction sa, sa_int, sa_quit, sa_pipe; 166 int temp, fds[2]; 167 168 shell = class = cleanenv = NULL; 169 asme = asthem = fastlogin = statusp = 0; 170 user = "root"; 171 iscsh = UNSET; 172 setmaclabel = 0; 173 174 while ((ch = getopt(argc, argv, "-flmsc:")) != -1) 175 switch ((char)ch) { 176 case 'f': 177 fastlogin = 1; 178 break; 179 case '-': 180 case 'l': 181 asme = 0; 182 asthem = 1; 183 break; 184 case 'm': 185 asme = 1; 186 asthem = 0; 187 break; 188 case 's': 189 setmaclabel = 1; 190 break; 191 case 'c': 192 class = optarg; 193 break; 194 case '?': 195 default: 196 usage(); 197 /* NOTREACHED */ 198 } 199 200 if (optind < argc) 201 user = argv[optind++]; 202 203 if (user == NULL) 204 usage(); 205 /* NOTREACHED */ 206 207 if (strlen(user) > MAXLOGNAME - 1) 208 errx(1, "username too long"); 209 210 /* 211 * Try to provide more helpful debugging output if su(1) is running 212 * non-setuid, or was run from a file system not mounted setuid. 213 */ 214 if (geteuid() != 0) 215 errx(1, "not running setuid"); 216 217 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 218 if (nargv == NULL) 219 errx(1, "malloc failure"); 220 221 nargv[argc + 3] = NULL; 222 for (i = argc; i >= optind; i--) 223 nargv[i + 3] = argv[i]; 224 np.a = &nargv[i + 3]; 225 226 argv += optind; 227 228 errno = 0; 229 prio = getpriority(PRIO_PROCESS, 0); 230 if (errno) 231 prio = 0; 232 233 setpriority(PRIO_PROCESS, 0, -2); 234 openlog("su", LOG_CONS, LOG_AUTH); 235 236 /* get current login name, real uid and shell */ 237 ruid = getuid(); 238 username = getlogin(); 239 pwd = getpwnam(username); 240 if (username == NULL || pwd == NULL || pwd->pw_uid != ruid) 241 pwd = getpwuid(ruid); 242 if (pwd == NULL) 243 errx(1, "who are you?"); 244 245 username = strdup(pwd->pw_name); 246 if (username == NULL) 247 err(1, "strdup failure"); 248 249 if (asme) { 250 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 251 /* must copy - pwd memory is recycled */ 252 shell = strncpy(shellbuf, pwd->pw_shell, 253 sizeof(shellbuf)); 254 shellbuf[sizeof(shellbuf) - 1] = '\0'; 255 } 256 else { 257 shell = _PATH_BSHELL; 258 iscsh = NO; 259 } 260 } 261 262 /* Do the whole PAM startup thing */ 263 retcode = pam_start("su", user, &conv, &pamh); 264 if (retcode != PAM_SUCCESS) { 265 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 266 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 267 } 268 269 PAM_SET_ITEM(PAM_RUSER, username); 270 271 mytty = ttyname(STDERR_FILENO); 272 if (!mytty) 273 mytty = "tty"; 274 PAM_SET_ITEM(PAM_TTY, mytty); 275 276 retcode = pam_authenticate(pamh, 0); 277 if (retcode != PAM_SUCCESS) { 278 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 279 username, user, mytty); 280 errx(1, "Sorry"); 281 } 282 retcode = pam_get_item(pamh, PAM_USER, (const void **)&p); 283 if (retcode == PAM_SUCCESS) 284 user = p; 285 else 286 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 287 pam_strerror(pamh, retcode)); 288 pwd = getpwnam(user); 289 if (pwd == NULL) 290 errx(1, "unknown login: %s", user); 291 292 retcode = pam_acct_mgmt(pamh, 0); 293 if (retcode == PAM_NEW_AUTHTOK_REQD) { 294 retcode = pam_chauthtok(pamh, 295 PAM_CHANGE_EXPIRED_AUTHTOK); 296 if (retcode != PAM_SUCCESS) { 297 syslog(LOG_ERR, "pam_chauthtok: %s", 298 pam_strerror(pamh, retcode)); 299 errx(1, "Sorry"); 300 } 301 } 302 if (retcode != PAM_SUCCESS) { 303 syslog(LOG_ERR, "pam_acct_mgmt: %s", 304 pam_strerror(pamh, retcode)); 305 errx(1, "Sorry"); 306 } 307 308 /* get target login information */ 309 if (class == NULL) 310 lc = login_getpwclass(pwd); 311 else { 312 if (ruid != 0) 313 errx(1, "only root may use -c"); 314 lc = login_getclass(class); 315 if (lc == NULL) 316 errx(1, "unknown class: %s", class); 317 } 318 319 /* if asme and non-standard target shell, must be root */ 320 if (asme) { 321 if (ruid != 0 && !chshell(pwd->pw_shell)) 322 errx(1, "permission denied (shell)"); 323 } 324 else if (pwd->pw_shell && *pwd->pw_shell) { 325 shell = pwd->pw_shell; 326 iscsh = UNSET; 327 } 328 else { 329 shell = _PATH_BSHELL; 330 iscsh = NO; 331 } 332 333 /* if we're forking a csh, we want to slightly muck the args */ 334 if (iscsh == UNSET) { 335 p = strrchr(shell, '/'); 336 if (p) 337 ++p; 338 else 339 p = shell; 340 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 341 } 342 setpriority(PRIO_PROCESS, 0, prio); 343 344 /* Switch to home directory */ 345 if (asthem) { 346 if (chdir(pwd->pw_dir) < 0) 347 errx(1, "no directory"); 348 } 349 350 /* 351 * PAM modules might add supplementary groups in pam_setcred(), so 352 * initialize them first. 353 */ 354 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 355 err(1, "setusercontext"); 356 357 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 358 if (retcode != PAM_SUCCESS) { 359 syslog(LOG_ERR, "pam_setcred: %s", 360 pam_strerror(pamh, retcode)); 361 errx(1, "failed to establish credentials."); 362 } 363 if (asthem) { 364 retcode = pam_open_session(pamh, 0); 365 if (retcode != PAM_SUCCESS) { 366 syslog(LOG_ERR, "pam_open_session: %s", 367 pam_strerror(pamh, retcode)); 368 errx(1, "failed to open session."); 369 } 370 } 371 372 /* 373 * We must fork() before setuid() because we need to call 374 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 375 */ 376 sa.sa_flags = SA_RESTART; 377 sa.sa_handler = SIG_IGN; 378 sigemptyset(&sa.sa_mask); 379 sigaction(SIGINT, &sa, &sa_int); 380 sigaction(SIGQUIT, &sa, &sa_quit); 381 sigaction(SIGPIPE, &sa, &sa_pipe); 382 sa.sa_handler = SIG_DFL; 383 sigaction(SIGTSTP, &sa, NULL); 384 statusp = 1; 385 if (pipe(fds) == -1) { 386 PAM_END(); 387 err(1, "pipe"); 388 } 389 child_pid = fork(); 390 switch (child_pid) { 391 default: 392 sa.sa_handler = SIG_IGN; 393 sigaction(SIGTTOU, &sa, NULL); 394 close(fds[0]); 395 close(fds[1]); 396 sigaction(SIGPIPE, &sa_pipe, NULL); 397 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 398 if (WIFSTOPPED(statusp)) { 399 kill(getpid(), SIGSTOP); 400 kill(child_pid, SIGCONT); 401 statusp = 1; 402 continue; 403 } 404 break; 405 } 406 if (pid == -1) 407 err(1, "waitpid"); 408 PAM_END(); 409 exit(WEXITSTATUS(statusp)); 410 case -1: 411 PAM_END(); 412 err(1, "fork"); 413 case 0: 414 close(fds[1]); 415 read(fds[0], &temp, 1); 416 close(fds[0]); 417 sigaction(SIGPIPE, &sa_pipe, NULL); 418 sigaction(SIGINT, &sa_int, NULL); 419 sigaction(SIGQUIT, &sa_quit, NULL); 420 421 /* 422 * Set all user context except for: Environmental variables 423 * Umask Login records (wtmp, etc) Path 424 */ 425 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 426 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP | 427 LOGIN_SETMAC); 428 /* 429 * If -s is present, also set the MAC label. 430 */ 431 if (setmaclabel) 432 setwhat |= LOGIN_SETMAC; 433 /* 434 * Don't touch resource/priority settings if -m has been used 435 * or -l and -c hasn't, and we're not su'ing to root. 436 */ 437 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 438 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 439 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 440 err(1, "setusercontext"); 441 442 if (!asme) { 443 if (asthem) { 444 p = getenv("TERM"); 445 environ = &cleanenv; 446 } 447 448 if (asthem || pwd->pw_uid) 449 setenv("USER", pwd->pw_name, 1); 450 setenv("HOME", pwd->pw_dir, 1); 451 setenv("SHELL", shell, 1); 452 453 if (asthem) { 454 /* 455 * Add any environmental variables that the 456 * PAM modules may have set. 457 */ 458 environ_pam = pam_getenvlist(pamh); 459 if (environ_pam) 460 export_pam_environment(); 461 462 /* set the su'd user's environment & umask */ 463 setusercontext(lc, pwd, pwd->pw_uid, 464 LOGIN_SETPATH | LOGIN_SETUMASK | 465 LOGIN_SETENV); 466 if (p) 467 setenv("TERM", p, 1); 468 } 469 } 470 login_close(lc); 471 472 if (iscsh == YES) { 473 if (fastlogin) 474 *np.a-- = "-f"; 475 if (asme) 476 *np.a-- = "-m"; 477 } 478 /* csh strips the first character... */ 479 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 480 481 if (ruid != 0) 482 syslog(LOG_NOTICE, "%s to %s%s", username, user, 483 ontty()); 484 485 execv(shell, np.b); 486 err(1, "%s", shell); 487 } 488} 489 490static void 491export_pam_environment(void) 492{ 493 char **pp; 494 495 for (pp = environ_pam; *pp != NULL; pp++) { 496 if (ok_to_export(*pp)) 497 putenv(*pp); 498 free(*pp); 499 } 500} 501 502/* 503 * Sanity checks on PAM environmental variables: 504 * - Make sure there is an '=' in the string. 505 * - Make sure the string doesn't run on too long. 506 * - Do not export certain variables. This list was taken from the 507 * Solaris pam_putenv(3) man page. 508 * Note that if the user is chrooted, PAM may have a better idea than we 509 * do of where her home directory is. 510 */ 511static int 512ok_to_export(const char *s) 513{ 514 static const char *noexport[] = { 515 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 516 "IFS", "PATH", NULL 517 }; 518 const char **pp; 519 size_t n; 520 521 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 522 return 0; 523 if (strncmp(s, "LD_", 3) == 0) 524 return 0; 525 for (pp = noexport; *pp != NULL; pp++) { 526 n = strlen(*pp); 527 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 528 return 0; 529 } 530 return 1; 531} 532 533static void 534usage(void) 535{ 536 537 fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n"); 538 exit(1); 539 /* NOTREACHED */ 540} 541 542static int 543chshell(const char *sh) 544{ 545 int r; 546 char *cp; 547 548 r = 0; 549 setusershell(); 550 while ((cp = getusershell()) != NULL && !r) 551 r = (strcmp(cp, sh) == 0); 552 endusershell(); 553 return r; 554} 555 556static char * 557ontty(void) 558{ 559 char *p; 560 static char buf[MAXPATHLEN + 4]; 561 562 buf[0] = 0; 563 p = ttyname(STDERR_FILENO); 564 if (p) 565 snprintf(buf, sizeof(buf), " on %s", p); 566 return buf; 567} 568