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 * @(#)su.c 8.3 (Berkeley) 4/2/94 64 * $FreeBSD: src/usr.bin/su/su.c,v 1.88 2008/06/04 19:16:54 dwmalone Exp $ 65 * $DragonFly: src/usr.bin/su/su.c,v 1.9 2006/01/12 13:43:11 corecode Exp $ 66 */ 67 68 #include <sys/param.h> 69 #include <sys/time.h> 70 #include <sys/resource.h> 71 #include <sys/wait.h> 72 73 #ifdef USE_BSM_AUDIT 74 #include <bsm/libbsm.h> 75 #include <bsm/audit_uevents.h> 76 #endif 77 78 #include <err.h> 79 #include <errno.h> 80 #include <grp.h> 81 #include <login_cap.h> 82 #include <paths.h> 83 #include <pwd.h> 84 #include <signal.h> 85 #include <stdio.h> 86 #include <stdlib.h> 87 #include <string.h> 88 #include <syslog.h> 89 #include <unistd.h> 90 #include <stdarg.h> 91 92 #include <security/pam_appl.h> 93 #include <security/openpam.h> 94 95 #define PAM_END() do { \ 96 int local_ret; \ 97 if (pamh != NULL) { \ 98 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 99 if (local_ret != PAM_SUCCESS) \ 100 syslog(LOG_ERR, "pam_setcred: %s", \ 101 pam_strerror(pamh, local_ret)); \ 102 if (asthem) { \ 103 local_ret = pam_close_session(pamh, 0); \ 104 if (local_ret != PAM_SUCCESS) \ 105 syslog(LOG_ERR, "pam_close_session: %s",\ 106 pam_strerror(pamh, local_ret)); \ 107 } \ 108 local_ret = pam_end(pamh, local_ret); \ 109 if (local_ret != PAM_SUCCESS) \ 110 syslog(LOG_ERR, "pam_end: %s", \ 111 pam_strerror(pamh, local_ret)); \ 112 } \ 113 } while (0) 114 115 116 #define PAM_SET_ITEM(what, item) do { \ 117 int local_ret; \ 118 local_ret = pam_set_item(pamh, what, item); \ 119 if (local_ret != PAM_SUCCESS) { \ 120 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 121 pam_strerror(pamh, local_ret)); \ 122 errx(1, "pam_set_item(" #what "): %s", \ 123 pam_strerror(pamh, local_ret)); \ 124 /* NOTREACHED */ \ 125 } \ 126 } while (0) 127 128 enum tristate { UNSET, YES, NO }; 129 130 static pam_handle_t *pamh = NULL; 131 static char **environ_pam; 132 133 static char *ontty(void); 134 static int chshell(const char *); 135 static void usage(void) __dead2; 136 static void export_pam_environment(void); 137 static int ok_to_export(const char *); 138 139 extern char **environ; 140 141 int 142 main(int argc, char **argv) 143 { 144 static char *cleanenv; 145 struct passwd *pwd; 146 struct pam_conv conv = { openpam_ttyconv, NULL }; 147 enum tristate iscsh; 148 login_cap_t *lc; 149 union { 150 const char **a; 151 char * const *b; 152 } np; 153 uid_t ruid; 154 pid_t child_pid, child_pgrp, pid; 155 int asme, ch, asthem, fastlogin, prio, i, retcode, 156 statusp; 157 u_int setwhat; 158 char *username, *class, shellbuf[MAXPATHLEN]; 159 const char *p = p, *user, *shell, *mytty, **nargv; 160 const void *v; 161 struct sigaction sa, sa_int, sa_quit, sa_pipe; 162 int temp, fds[2]; 163 #ifdef USE_BSM_AUDIT 164 const char *aerr; 165 au_id_t auid; 166 #endif 167 168 shell = class = cleanenv = NULL; 169 asme = asthem = fastlogin = statusp = 0; 170 user = "root"; 171 iscsh = UNSET; 172 173 while ((ch = getopt(argc, argv, "-flmc:")) != -1) 174 switch ((char)ch) { 175 case 'f': 176 fastlogin = 1; 177 break; 178 case '-': 179 case 'l': 180 asme = 0; 181 asthem = 1; 182 break; 183 case 'm': 184 asme = 1; 185 asthem = 0; 186 break; 187 case 'c': 188 class = optarg; 189 break; 190 case '?': 191 default: 192 usage(); 193 /* NOTREACHED */ 194 } 195 196 if (optind < argc && strcmp(argv[optind], "-") == 0) { 197 asme = 0; 198 asthem = 1; 199 optind++; 200 } 201 202 if (optind < argc) 203 user = argv[optind++]; 204 205 if (user == NULL) 206 usage(); 207 /* NOTREACHED */ 208 209 /* 210 * Try to provide more helpful debugging output if su(1) is running 211 * non-setuid, or was run from a file system not mounted setuid. 212 */ 213 if (geteuid() != 0) 214 errx(1, "not running setuid"); 215 216 #ifdef USE_BSM_AUDIT 217 if (getauid(&auid) < 0 && errno != ENOSYS) { 218 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno)); 219 errx(1, "Permission denied"); 220 } 221 #endif 222 if (strlen(user) > MAXLOGNAME - 1) { 223 #ifdef USE_BSM_AUDIT 224 if (audit_submit(AUE_su, auid, 225 1, EPERM, "username too long: '%s'", user)) 226 errx(1, "Permission denied"); 227 #endif 228 errx(1, "username too long"); 229 } 230 231 nargv = malloc(sizeof(char *) * (size_t)(argc + 4)); 232 if (nargv == NULL) 233 errx(1, "malloc failure"); 234 235 nargv[argc + 3] = NULL; 236 for (i = argc; i >= optind; i--) 237 nargv[i + 3] = argv[i]; 238 np.a = &nargv[i + 3]; 239 240 argv += optind; 241 242 errno = 0; 243 prio = getpriority(PRIO_PROCESS, 0); 244 if (errno) 245 prio = 0; 246 247 setpriority(PRIO_PROCESS, 0, -2); 248 openlog("su", LOG_CONS, LOG_AUTH); 249 250 /* get current login name, real uid and shell */ 251 ruid = getuid(); 252 username = getlogin(); 253 pwd = getpwnam(username); 254 if (username == NULL || pwd == NULL || pwd->pw_uid != ruid) 255 pwd = getpwuid(ruid); 256 if (pwd == NULL) { 257 #ifdef USE_BSM_AUDIT 258 if (audit_submit(AUE_su, auid, 1, EPERM, 259 "unable to determine invoking subject: '%s'", username)) 260 errx(1, "Permission denied"); 261 #endif 262 errx(1, "who are you?"); 263 } 264 265 username = strdup(pwd->pw_name); 266 if (username == NULL) 267 err(1, "strdup failure"); 268 269 if (asme) { 270 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 271 /* must copy - pwd memory is recycled */ 272 shell = strncpy(shellbuf, pwd->pw_shell, 273 sizeof(shellbuf)); 274 shellbuf[sizeof(shellbuf) - 1] = '\0'; 275 } 276 else { 277 shell = _PATH_BSHELL; 278 iscsh = NO; 279 } 280 } 281 282 /* Do the whole PAM startup thing */ 283 retcode = pam_start("su", user, &conv, &pamh); 284 if (retcode != PAM_SUCCESS) { 285 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 286 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 287 } 288 289 PAM_SET_ITEM(PAM_RUSER, username); 290 291 mytty = ttyname(STDERR_FILENO); 292 if (!mytty) 293 mytty = "tty"; 294 PAM_SET_ITEM(PAM_TTY, mytty); 295 296 retcode = pam_authenticate(pamh, 0); 297 if (retcode != PAM_SUCCESS) { 298 #ifdef USE_BSM_AUDIT 299 if (audit_submit(AUE_su, auid, 1, EPERM, "bad su %s to %s on %s", 300 username, user, mytty)) 301 errx(1, "Permission denied"); 302 #endif 303 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 304 username, user, mytty); 305 errx(1, "Sorry"); 306 } 307 #ifdef USE_BSM_AUDIT 308 if (audit_submit(AUE_su, auid, 0, 0, "successful authentication")) 309 errx(1, "Permission denied"); 310 #endif 311 retcode = pam_get_item(pamh, PAM_USER, &v); 312 if (retcode == PAM_SUCCESS) 313 user = v; 314 else 315 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 316 pam_strerror(pamh, retcode)); 317 pwd = getpwnam(user); 318 if (pwd == NULL) { 319 #ifdef USE_BSM_AUDIT 320 if (audit_submit(AUE_su, auid, 1, EPERM, 321 "unknown subject: %s", user)) 322 errx(1, "Permission denied"); 323 #endif 324 errx(1, "unknown login: %s", user); 325 } 326 327 retcode = pam_acct_mgmt(pamh, 0); 328 if (retcode == PAM_NEW_AUTHTOK_REQD) { 329 retcode = pam_chauthtok(pamh, 330 PAM_CHANGE_EXPIRED_AUTHTOK); 331 if (retcode != PAM_SUCCESS) { 332 #ifdef USE_BSM_AUDIT 333 aerr = pam_strerror(pamh, retcode); 334 if (aerr == NULL) 335 aerr = "Unknown PAM error"; 336 if (audit_submit(AUE_su, auid, 1, EPERM, 337 "pam_chauthtok: %s", aerr)) 338 errx(1, "Permission denied"); 339 #endif 340 syslog(LOG_ERR, "pam_chauthtok: %s", 341 pam_strerror(pamh, retcode)); 342 errx(1, "Sorry"); 343 } 344 } 345 if (retcode != PAM_SUCCESS) { 346 #ifdef USE_BSM_AUDIT 347 if (audit_submit(AUE_su, auid, 1, EPERM, "pam_acct_mgmt: %s", 348 pam_strerror(pamh, retcode))) 349 errx(1, "Permission denied"); 350 #endif 351 syslog(LOG_ERR, "pam_acct_mgmt: %s", 352 pam_strerror(pamh, retcode)); 353 errx(1, "Sorry"); 354 } 355 356 /* get target login information */ 357 if (class == NULL) 358 lc = login_getpwclass(pwd); 359 else { 360 if (ruid != 0) { 361 #ifdef USE_BSM_AUDIT 362 if (audit_submit(AUE_su, auid, 1, EPERM, 363 "only root may use -c")) 364 errx(1, "Permission denied"); 365 #endif 366 errx(1, "only root may use -c"); 367 } 368 lc = login_getclass(class); 369 if (lc == NULL) 370 errx(1, "unknown class: %s", class); 371 } 372 373 /* if asme and non-standard target shell, must be root */ 374 if (asme) { 375 if (ruid != 0 && !chshell(pwd->pw_shell)) 376 errx(1, "permission denied (shell)"); 377 } 378 else if (pwd->pw_shell && *pwd->pw_shell) { 379 shell = pwd->pw_shell; 380 iscsh = UNSET; 381 } 382 else { 383 shell = _PATH_BSHELL; 384 iscsh = NO; 385 } 386 387 /* if we're forking a csh, we want to slightly muck the args */ 388 if (iscsh == UNSET) { 389 p = strrchr(shell, '/'); 390 if (p) 391 ++p; 392 else 393 p = shell; 394 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 395 } 396 setpriority(PRIO_PROCESS, 0, prio); 397 398 /* 399 * PAM modules might add supplementary groups in pam_setcred(), so 400 * initialize them first. 401 */ 402 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 403 err(1, "setusercontext"); 404 405 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 406 if (retcode != PAM_SUCCESS) { 407 syslog(LOG_ERR, "pam_setcred: %s", 408 pam_strerror(pamh, retcode)); 409 errx(1, "failed to establish credentials."); 410 } 411 if (asthem) { 412 retcode = pam_open_session(pamh, 0); 413 if (retcode != PAM_SUCCESS) { 414 syslog(LOG_ERR, "pam_open_session: %s", 415 pam_strerror(pamh, retcode)); 416 errx(1, "failed to open session."); 417 } 418 } 419 420 /* 421 * We must fork() before setuid() because we need to call 422 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 423 */ 424 sa.sa_flags = SA_RESTART; 425 sa.sa_handler = SIG_IGN; 426 sigemptyset(&sa.sa_mask); 427 sigaction(SIGINT, &sa, &sa_int); 428 sigaction(SIGQUIT, &sa, &sa_quit); 429 sigaction(SIGPIPE, &sa, &sa_pipe); 430 sa.sa_handler = SIG_DFL; 431 sigaction(SIGTSTP, &sa, NULL); 432 statusp = 1; 433 if (pipe(fds) == -1) { 434 PAM_END(); 435 err(1, "pipe"); 436 } 437 child_pid = fork(); 438 switch (child_pid) { 439 default: 440 sa.sa_handler = SIG_IGN; 441 sigaction(SIGTTOU, &sa, NULL); 442 close(fds[0]); 443 setpgid(child_pid, child_pid); 444 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) 445 tcsetpgrp(STDERR_FILENO, child_pid); 446 close(fds[1]); 447 sigaction(SIGPIPE, &sa_pipe, NULL); 448 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 449 if (WIFSTOPPED(statusp)) { 450 child_pgrp = getpgid(child_pid); 451 if (tcgetpgrp(STDERR_FILENO) == child_pgrp) 452 tcsetpgrp(STDERR_FILENO, getpgrp()); 453 kill(getpid(), SIGSTOP); 454 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) { 455 child_pgrp = getpgid(child_pid); 456 tcsetpgrp(STDERR_FILENO, child_pgrp); 457 } 458 kill(child_pid, SIGCONT); 459 statusp = 1; 460 continue; 461 } 462 break; 463 } 464 tcsetpgrp(STDERR_FILENO, getpgrp()); 465 if (pid == -1) 466 err(1, "waitpid"); 467 PAM_END(); 468 exit(WEXITSTATUS(statusp)); 469 case -1: 470 PAM_END(); 471 err(1, "fork"); 472 case 0: 473 close(fds[1]); 474 read(fds[0], &temp, 1); 475 close(fds[0]); 476 sigaction(SIGPIPE, &sa_pipe, NULL); 477 sigaction(SIGINT, &sa_int, NULL); 478 sigaction(SIGQUIT, &sa_quit, NULL); 479 480 /* 481 * Set all user context except for: Environmental variables 482 * Umask Login records (wtmp, etc) Path 483 * XXX Missing LOGIN_SETMAC 484 */ 485 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 486 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP); 487 #if 0 488 /* 489 * If -s is present, also set the MAC label. 490 */ 491 if (setmaclabel) 492 setwhat |= LOGIN_SETMAC; 493 #endif 494 /* 495 * Don't touch resource/priority settings if -m has been used 496 * or -l and -c hasn't, and we're not su'ing to root. 497 */ 498 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 499 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 500 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 501 err(1, "setusercontext"); 502 503 if (!asme) { 504 if (asthem) { 505 p = getenv("TERM"); 506 environ = &cleanenv; 507 } 508 509 if (asthem || pwd->pw_uid) { 510 if (setenv("USER", pwd->pw_name, 1) == -1) { 511 err(1, "setenv: cannot set USER=%s", 512 pwd->pw_name); 513 } 514 } 515 if (setenv("HOME", pwd->pw_dir, 1) == -1) { 516 err(1, "setenv: cannot set HOME=%s", 517 pwd->pw_dir); 518 } 519 if (setenv("SHELL", shell, 1) == -1) 520 err(1, "setenv: cannot set SHELL=%s", shell); 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 if (setenv("TERM", p, 1) == -1) { 537 err(1, 538 "setenv: cannot set TERM=%s", 539 p); 540 } 541 } 542 543 p = pam_getenv(pamh, "HOME"); 544 if (chdir(p ? p : pwd->pw_dir) < 0) 545 errx(1, "no directory"); 546 } 547 } 548 login_close(lc); 549 550 if (iscsh == YES) { 551 if (fastlogin) 552 *np.a-- = "-f"; 553 if (asme) 554 *np.a-- = "-m"; 555 } 556 /* csh strips the first character... */ 557 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 558 559 if (ruid != 0) 560 syslog(LOG_NOTICE, "%s to %s%s", username, user, 561 ontty()); 562 563 execv(shell, np.b); 564 err(1, "%s", shell); 565 } 566 } 567 568 static void 569 export_pam_environment(void) 570 { 571 char **pp; 572 char *p; 573 574 for (pp = environ_pam; *pp != NULL; pp++) { 575 if (ok_to_export(*pp)) { 576 p = strchr(*pp, '='); 577 *p = '\0'; 578 if (setenv(*pp, p + 1, 1) == -1) 579 err(1, "setenv: cannot set %s=%s", *pp, p + 1); 580 } 581 free(*pp); 582 } 583 } 584 585 /* 586 * Sanity checks on PAM environmental variables: 587 * - Make sure there is an '=' in the string. 588 * - Make sure the string doesn't run on too long. 589 * - Do not export certain variables. This list was taken from the 590 * Solaris pam_putenv(3) man page. 591 * Note that if the user is chrooted, PAM may have a better idea than we 592 * do of where her home directory is. 593 */ 594 static int 595 ok_to_export(const char *s) 596 { 597 static const char *noexport[] = { 598 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH", 599 "IFS", "PATH", NULL 600 }; 601 const char **pp; 602 size_t n; 603 604 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 605 return 0; 606 if (strncmp(s, "LD_", 3) == 0) 607 return 0; 608 for (pp = noexport; *pp != NULL; pp++) { 609 n = strlen(*pp); 610 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 611 return 0; 612 } 613 return 1; 614 } 615 616 static void 617 usage(void) 618 { 619 620 fprintf(stderr, "usage: su [-] [-flm] [-c class] [login [args]]\n"); 621 exit(1); 622 /* NOTREACHED */ 623 } 624 625 static int 626 chshell(const char *sh) 627 { 628 int r; 629 char *cp; 630 631 r = 0; 632 setusershell(); 633 while ((cp = getusershell()) != NULL && !r) 634 r = (strcmp(cp, sh) == 0); 635 endusershell(); 636 return r; 637 } 638 639 static char * 640 ontty(void) 641 { 642 char *p; 643 static char buf[MAXPATHLEN + 4]; 644 645 buf[0] = 0; 646 p = ttyname(STDERR_FILENO); 647 if (p) 648 snprintf(buf, sizeof(buf), " on %s", p); 649 return buf; 650 } 651