1 /* 2 * Copyright (c) 1988, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2002 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 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 */ 40 41 #ifndef lint 42 static const char copyright[] = 43 "@(#) Copyright (c) 1988, 1993, 1994\n\ 44 The Regents of the University of California. All rights reserved.\n"; 45 #endif /* not lint */ 46 47 #ifndef lint 48 #if 0 49 static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94"; 50 #endif 51 static const char rcsid[] = 52 "$FreeBSD$"; 53 #endif /* not lint */ 54 55 #include <sys/param.h> 56 #include <sys/time.h> 57 #include <sys/resource.h> 58 #include <sys/wait.h> 59 60 #include <err.h> 61 #include <errno.h> 62 #include <grp.h> 63 #include <libutil.h> 64 #include <login_cap.h> 65 #include <paths.h> 66 #include <pwd.h> 67 #include <signal.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 #include <string.h> 71 #include <syslog.h> 72 #include <unistd.h> 73 74 #include <security/pam_appl.h> 75 #include <security/openpam.h> 76 77 #define PAM_END() do { \ 78 int local_ret; \ 79 if (pamh != NULL && creds_set) { \ 80 local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \ 81 if (local_ret != PAM_SUCCESS) \ 82 syslog(LOG_ERR, "pam_setcred: %s", \ 83 pam_strerror(pamh, local_ret)); \ 84 local_ret = pam_end(pamh, local_ret); \ 85 if (local_ret != PAM_SUCCESS) \ 86 syslog(LOG_ERR, "pam_end: %s", \ 87 pam_strerror(pamh, local_ret)); \ 88 } \ 89 } while (0) 90 91 92 #define PAM_SET_ITEM(what, item) do { \ 93 int local_ret; \ 94 local_ret = pam_set_item(pamh, what, item); \ 95 if (local_ret != PAM_SUCCESS) { \ 96 syslog(LOG_ERR, "pam_set_item(" #what "): %s", \ 97 pam_strerror(pamh, local_ret)); \ 98 errx(1, "pam_set_item(" #what "): %s", \ 99 pam_strerror(pamh, local_ret)); \ 100 } \ 101 } while (0) 102 103 enum tristate { UNSET, YES, NO }; 104 105 static pam_handle_t *pamh = NULL; 106 static int creds_set = 0; 107 static char **environ_pam; 108 109 static char *ontty(void); 110 static int chshell(char *); 111 static void usage(void); 112 static int export_pam_environment(void); 113 static int ok_to_export(const char *); 114 115 extern char **environ; 116 117 int 118 main(int argc, char *argv[]) 119 { 120 struct passwd *pwd; 121 struct pam_conv conv = { openpam_ttyconv, NULL }; 122 enum tristate iscsh; 123 login_cap_t *lc; 124 union { 125 const char **a; 126 char * const *b; 127 } np; 128 uid_t ruid; 129 int asme, ch, asthem, fastlogin, prio, i, setwhat, retcode, 130 statusp, child_pid, child_pgrp, ret_pid; 131 char *username, *cleanenv, *class, shellbuf[MAXPATHLEN]; 132 const char *p, *user, *shell, *mytty, **nargv; 133 134 struct sigaction sa, sa_int, sa_quit, sa_tstp; 135 136 shell = class = cleanenv = NULL; 137 asme = asthem = fastlogin = statusp = 0; 138 user = "root"; 139 iscsh = UNSET; 140 141 while ((ch = getopt(argc, argv, "-flmc:")) != -1) 142 switch ((char)ch) { 143 case 'f': 144 fastlogin = 1; 145 break; 146 case '-': 147 case 'l': 148 asme = 0; 149 asthem = 1; 150 break; 151 case 'm': 152 asme = 1; 153 asthem = 0; 154 break; 155 case 'c': 156 class = optarg; 157 break; 158 case '?': 159 default: 160 usage(); 161 } 162 163 if (optind < argc) 164 user = argv[optind++]; 165 166 if (user == NULL) 167 usage(); 168 169 if (strlen(user) > MAXLOGNAME - 1) 170 errx(1, "username too long"); 171 172 nargv = malloc(sizeof(char *) * (argc + 4)); 173 if (nargv == NULL) 174 errx(1, "malloc failure"); 175 176 nargv[argc + 3] = NULL; 177 for (i = argc; i >= optind; i--) 178 nargv[i + 3] = argv[i]; 179 np.a = &nargv[i + 3]; 180 181 argv += optind; 182 183 errno = 0; 184 prio = getpriority(PRIO_PROCESS, 0); 185 if (errno) 186 prio = 0; 187 188 setpriority(PRIO_PROCESS, 0, -2); 189 openlog("su", LOG_CONS, LOG_AUTH); 190 191 /* get current login name, real uid and shell */ 192 ruid = getuid(); 193 username = getlogin(); 194 pwd = getpwnam(username); 195 if (username == NULL || pwd == NULL || pwd->pw_uid != ruid) 196 pwd = getpwuid(ruid); 197 if (pwd == NULL) 198 errx(1, "who are you?"); 199 200 username = strdup(pwd->pw_name); 201 if (username == NULL) 202 err(1, "strdup failure"); 203 204 if (asme) { 205 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') { 206 /* must copy - pwd memory is recycled */ 207 shell = strncpy(shellbuf, pwd->pw_shell, 208 sizeof(shellbuf)); 209 shellbuf[sizeof(shellbuf) - 1] = '\0'; 210 } 211 else { 212 shell = _PATH_BSHELL; 213 iscsh = NO; 214 } 215 } 216 217 /* Do the whole PAM startup thing */ 218 retcode = pam_start("su", user, &conv, &pamh); 219 if (retcode != PAM_SUCCESS) { 220 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode)); 221 errx(1, "pam_start: %s", pam_strerror(pamh, retcode)); 222 } 223 224 PAM_SET_ITEM(PAM_RUSER, getlogin()); 225 226 mytty = ttyname(STDERR_FILENO); 227 if (!mytty) 228 mytty = "tty"; 229 PAM_SET_ITEM(PAM_TTY, mytty); 230 231 retcode = pam_authenticate(pamh, 0); 232 if (retcode != PAM_SUCCESS) { 233 #if 0 234 syslog(LOG_ERR, "pam_authenticate: %s", 235 pam_strerror(pamh, retcode)); 236 #endif 237 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s", 238 username, user, mytty); 239 errx(1, "Sorry"); 240 } 241 retcode = pam_get_item(pamh, PAM_USER, (const void **)&p); 242 if (retcode == PAM_SUCCESS) 243 user = p; 244 else 245 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s", 246 pam_strerror(pamh, retcode)); 247 248 retcode = pam_acct_mgmt(pamh, 0); 249 if (retcode == PAM_NEW_AUTHTOK_REQD) { 250 retcode = pam_chauthtok(pamh, 251 PAM_CHANGE_EXPIRED_AUTHTOK); 252 if (retcode != PAM_SUCCESS) { 253 syslog(LOG_ERR, "pam_chauthtok: %s", 254 pam_strerror(pamh, retcode)); 255 errx(1, "Sorry"); 256 } 257 } 258 if (retcode != PAM_SUCCESS) { 259 syslog(LOG_ERR, "pam_acct_mgmt: %s", 260 pam_strerror(pamh, retcode)); 261 errx(1, "Sorry"); 262 } 263 264 /* get target login information, default to root */ 265 pwd = getpwnam(user); 266 if (pwd == NULL) 267 errx(1, "unknown login: %s", user); 268 if (class == NULL) 269 lc = login_getpwclass(pwd); 270 else { 271 if (ruid != 0) 272 errx(1, "only root may use -c"); 273 lc = login_getclass(class); 274 if (lc == NULL) 275 errx(1, "unknown class: %s", class); 276 } 277 278 /* if asme and non-standard target shell, must be root */ 279 if (asme) { 280 if (ruid != 0 && !chshell(pwd->pw_shell)) 281 errx(1, "permission denied (shell)."); 282 } 283 else if (pwd->pw_shell && *pwd->pw_shell) { 284 shell = pwd->pw_shell; 285 iscsh = UNSET; 286 } 287 else { 288 shell = _PATH_BSHELL; 289 iscsh = NO; 290 } 291 292 /* if we're forking a csh, we want to slightly muck the args */ 293 if (iscsh == UNSET) { 294 p = strrchr(shell, '/'); 295 if (p) 296 ++p; 297 else 298 p = shell; 299 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES; 300 } 301 setpriority(PRIO_PROCESS, 0, prio); 302 303 /* 304 * PAM modules might add supplementary groups in pam_setcred(), so 305 * initialize them first. 306 */ 307 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0) 308 err(1, "setusercontext"); 309 310 retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED); 311 if (retcode != PAM_SUCCESS) 312 syslog(LOG_ERR, "pam_setcred(pamh, PAM_ESTABLISH_CRED): %s", 313 pam_strerror(pamh, retcode)); 314 else 315 creds_set = 1; 316 317 /* 318 * We must fork() before setuid() because we need to call 319 * pam_setcred(pamh, PAM_DELETE_CRED) as root. 320 */ 321 sa.sa_flags = SA_RESTART; 322 sa.sa_handler = SIG_IGN; 323 sigemptyset(&sa.sa_mask); 324 sigaction(SIGINT, &sa, &sa_int); 325 sigaction(SIGQUIT, &sa, &sa_quit); 326 sigaction(SIGTSTP, &sa, &sa_tstp); 327 328 statusp = 1; 329 child_pid = fork(); 330 switch (child_pid) { 331 default: 332 while ((ret_pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) { 333 if (WIFSTOPPED(statusp)) { 334 kill(getpid(), SIGSTOP); 335 child_pgrp = getpgid(child_pid); 336 if (tcgetpgrp(1) == getpgrp()) { 337 tcsetpgrp(1, child_pgrp); 338 kill(child_pid, SIGCONT); 339 } 340 statusp = 1; 341 continue; 342 } 343 break; 344 } 345 if (ret_pid == -1) 346 err(1, "waitpid"); 347 PAM_END(); 348 exit(statusp); 349 case -1: 350 err(1, "fork"); 351 PAM_END(); 352 exit(1); 353 case 0: 354 sigaction(SIGINT, &sa_int, NULL); 355 sigaction(SIGQUIT, &sa_quit, NULL); 356 sigaction(SIGTSTP, &sa_tstp, NULL); 357 /* 358 * Set all user context except for: Environmental variables 359 * Umask Login records (wtmp, etc) Path 360 */ 361 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK | 362 LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP); 363 /* 364 * Don't touch resource/priority settings if -m has been used 365 * or -l and -c hasn't, and we're not su'ing to root. 366 */ 367 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid) 368 setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES); 369 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0) 370 err(1, "setusercontext"); 371 372 if (!asme) { 373 if (asthem) { 374 p = getenv("TERM"); 375 environ = &cleanenv; 376 377 /* 378 * Add any environmental variables that the 379 * PAM modules may have set. 380 */ 381 environ_pam = pam_getenvlist(pamh); 382 if (environ_pam) 383 export_pam_environment(); 384 385 /* set the su'd user's environment & umask */ 386 setusercontext(lc, pwd, pwd->pw_uid, 387 LOGIN_SETPATH | LOGIN_SETUMASK | 388 LOGIN_SETENV); 389 if (p) 390 setenv("TERM", p, 1); 391 if (chdir(pwd->pw_dir) < 0) 392 errx(1, "no directory"); 393 } 394 if (asthem || pwd->pw_uid) 395 setenv("USER", pwd->pw_name, 1); 396 setenv("HOME", pwd->pw_dir, 1); 397 setenv("SHELL", shell, 1); 398 } 399 login_close(lc); 400 401 if (iscsh == YES) { 402 if (fastlogin) 403 *np.a-- = "-f"; 404 if (asme) 405 *np.a-- = "-m"; 406 } 407 /* csh strips the first character... */ 408 *np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su"; 409 410 if (ruid != 0) 411 syslog(LOG_NOTICE, "%s to %s%s", username, user, 412 ontty()); 413 414 execv(shell, np.b); 415 err(1, "%s", shell); 416 } 417 } 418 419 static int 420 export_pam_environment(void) 421 { 422 char **pp; 423 424 for (pp = environ_pam; *pp != NULL; pp++) { 425 if (ok_to_export(*pp)) 426 putenv(*pp); 427 free(*pp); 428 } 429 return PAM_SUCCESS; 430 } 431 432 /* 433 * Sanity checks on PAM environmental variables: 434 * - Make sure there is an '=' in the string. 435 * - Make sure the string doesn't run on too long. 436 * - Do not export certain variables. This list was taken from the 437 * Solaris pam_putenv(3) man page. 438 */ 439 static int 440 ok_to_export(const char *s) 441 { 442 static const char *noexport[] = { 443 "SHELL", "HOME", "LOGNAME", "MAIL", "CDPATH", 444 "IFS", "PATH", NULL 445 }; 446 const char **pp; 447 size_t n; 448 449 if (strlen(s) > 1024 || strchr(s, '=') == NULL) 450 return 0; 451 if (strncmp(s, "LD_", 3) == 0) 452 return 0; 453 for (pp = noexport; *pp != NULL; pp++) { 454 n = strlen(*pp); 455 if (s[n] == '=' && strncmp(s, *pp, n) == 0) 456 return 0; 457 } 458 return 1; 459 } 460 461 static void 462 usage(void) 463 { 464 465 fprintf(stderr, "usage: su [-] [-flm] [-c class] [login [args]]\n"); 466 exit(1); 467 } 468 469 static int 470 chshell(char *sh) 471 { 472 int r; 473 char *cp; 474 475 r = 0; 476 setusershell(); 477 do { 478 cp = getusershell(); 479 r = strcmp(cp, sh); 480 } while (!r && cp != NULL); 481 endusershell(); 482 return r; 483 } 484 485 static char * 486 ontty(void) 487 { 488 char *p; 489 static char buf[MAXPATHLEN + 4]; 490 491 buf[0] = 0; 492 p = ttyname(STDERR_FILENO); 493 if (p) 494 snprintf(buf, sizeof(buf), " on %s", p); 495 return buf; 496 } 497