usr.bin/su/su.c

   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. Neither the name of the University nor the names of its contributors
  44  *    may be used to endorse or promote products derived from this software
  45  *    without specific prior written permission.
  46  *
  47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  57  * SUCH DAMAGE.
  58  *
  59  * @(#)su.c     8.3 (Berkeley) 4/2/94
  60  * $FreeBSD: src/usr.bin/su/su.c,v 1.88 2008/06/04 19:16:54 dwmalone Exp $
  61  */
  62
  63 #include <sys/param.h>
  64 #include <sys/time.h>
  65 #include <sys/resource.h>
  66 #include <sys/wait.h>
  67
  68 #ifdef USE_BSM_AUDIT
  69 #include <bsm/libbsm.h>
  70 #include <bsm/audit_uevents.h>
  71 #endif
  72
  73 #include <err.h>
  74 #include <errno.h>
  75 #include <grp.h>
  76 #include <login_cap.h>
  77 #include <paths.h>
  78 #include <pwd.h>
  79 #include <signal.h>
  80 #include <stdio.h>
  81 #include <stdlib.h>
  82 #include <string.h>
  83 #include <syslog.h>
  84 #include <unistd.h>
  85 #include <stdarg.h>
  86
  87 #include <security/pam_appl.h>
  88 #include <security/openpam.h>
  89
  90 #define PAM_END() do {                                                  \
  91         int local_ret;                                                  \
  92         if (pamh != NULL) {                                             \
  93                 local_ret = pam_setcred(pamh, PAM_DELETE_CRED);         \
  94                 if (local_ret != PAM_SUCCESS)                           \
  95                         syslog(LOG_ERR, "pam_setcred: %s",              \
  96                                 pam_strerror(pamh, local_ret));         \
  97                 if (asthem) {                                           \
  98                         local_ret = pam_close_session(pamh, 0);         \
  99                         if (local_ret != PAM_SUCCESS)                   \
 100                                 syslog(LOG_ERR, "pam_close_session: %s",\
 101                                         pam_strerror(pamh, local_ret)); \
 102                 }                                                       \
 103                 local_ret = pam_end(pamh, local_ret);                   \
 104                 if (local_ret != PAM_SUCCESS)                           \
 105                         syslog(LOG_ERR, "pam_end: %s",                  \
 106                                 pam_strerror(pamh, local_ret));         \
 107         }                                                               \
 108 } while (0)
 109
 110
 111 #define PAM_SET_ITEM(what, item) do {                                   \
 112         int local_ret;                                                  \
 113         local_ret = pam_set_item(pamh, what, item);                     \
 114         if (local_ret != PAM_SUCCESS) {                                 \
 115                 syslog(LOG_ERR, "pam_set_item(" #what "): %s",          \
 116                         pam_strerror(pamh, local_ret));                 \
 117                 errx(1, "pam_set_item(" #what "): %s",                  \
 118                         pam_strerror(pamh, local_ret));                 \
 119                 /* NOTREACHED */                                        \
 120         }                                                               \
 121 } while (0)
 122
 123 enum tristate { UNSET, YES, NO };
 124
 125 static pam_handle_t *pamh = NULL;
 126 static char     **environ_pam;
 127
 128 static char     *ontty(void);
 129 static int      chshell(const char *);
 130 static void     usage(void) __dead2;
 131 static void     export_pam_environment(void);
 132 static int      ok_to_export(const char *);
 133
 134 extern char     **environ;
 135
 136 int
 137 main(int argc, char **argv)
 138 {
 139         static char     *cleanenv;
 140         struct passwd   *pwd;
 141         struct pam_conv conv = { openpam_ttyconv, NULL };
 142         enum tristate   iscsh;
 143         login_cap_t     *lc;
 144         union {
 145                 const char      **a;
 146                 char            * const *b;
 147         }               np;
 148         uid_t           ruid;
 149         pid_t           child_pid, child_pgrp, pid;
 150         int             asme, ch, asthem, fastlogin, prio, i, retcode,
 151                         statusp;
 152         u_int           setwhat;
 153         char            *username, *class, shellbuf[MAXPATHLEN];
 154         const char      *p = NULL, *user, *shell, *mytty, **nargv;
 155         const void      *v;
 156         struct sigaction sa, sa_int, sa_quit, sa_pipe;
 157         int temp, fds[2];
 158 #ifdef USE_BSM_AUDIT
 159         const char      *aerr;
 160         au_id_t          auid;
 161 #endif
 162
 163         shell = class = cleanenv = NULL;
 164         asme = asthem = fastlogin = statusp = 0;
 165         user = "root";
 166         iscsh = UNSET;
 167
 168         while ((ch = getopt(argc, argv, "-flmc:")) != -1)
 169                 switch ((char)ch) {
 170                 case 'f':
 171                         fastlogin = 1;
 172                         break;
 173                 case '-':
 174                 case 'l':
 175                         asme = 0;
 176                         asthem = 1;
 177                         break;
 178                 case 'm':
 179                         asme = 1;
 180                         asthem = 0;
 181                         break;
 182                 case 'c':
 183                         class = optarg;
 184                         break;
 185                 case '?':
 186                 default:
 187                         usage();
 188                 /* NOTREACHED */
 189                 }
 190
 191         if (optind < argc && strcmp(argv[optind], "-") == 0) {
 192                 asme = 0;
 193                 asthem = 1;
 194                 optind++;
 195         }
 196
 197         if (optind < argc)
 198                 user = argv[optind++];
 199
 200         if (user == NULL)
 201                 usage();
 202         /* NOTREACHED */
 203
 204         /*
 205          * Try to provide more helpful debugging output if su(1) is running
 206          * non-setuid, or was run from a file system not mounted setuid.
 207          */
 208         if (geteuid() != 0)
 209                 errx(1, "not running setuid");
 210
 211 #ifdef USE_BSM_AUDIT
 212         if (getauid(&auid) < 0 && errno != ENOSYS) {
 213                 syslog(LOG_AUTH | LOG_ERR, "getauid: %s", strerror(errno));
 214                 errx(1, "Permission denied");
 215         }
 216 #endif
 217         if (strlen(user) > MAXLOGNAME - 1) {
 218 #ifdef USE_BSM_AUDIT
 219                 if (audit_submit(AUE_su, auid,
 220                     1, EPERM, "username too long: '%s'", user))
 221                         errx(1, "Permission denied");
 222 #endif
 223                 errx(1, "username too long");
 224         }
 225
 226         nargv = malloc(sizeof(char *) * (size_t)(argc + 4));
 227         if (nargv == NULL)
 228                 errx(1, "malloc failure");
 229
 230         nargv[argc + 3] = NULL;
 231         for (i = argc; i >= optind; i--)
 232                 nargv[i + 3] = argv[i];
 233         np.a = &nargv[i + 3];
 234
 235         argv += optind;
 236
 237         errno = 0;
 238         prio = getpriority(PRIO_PROCESS, 0);
 239         if (errno)
 240                 prio = 0;
 241
 242         setpriority(PRIO_PROCESS, 0, -2);
 243         openlog("su", LOG_CONS, LOG_AUTH);
 244
 245         /* get current login name, real uid and shell */
 246         ruid = getuid();
 247         username = getlogin();
 248         pwd = getpwnam(username);
 249         if (username == NULL || pwd == NULL || pwd->pw_uid != ruid)
 250                 pwd = getpwuid(ruid);
 251         if (pwd == NULL) {
 252 #ifdef USE_BSM_AUDIT
 253                 if (audit_submit(AUE_su, auid, 1, EPERM,
 254                     "unable to determine invoking subject: '%s'", username))
 255                         errx(1, "Permission denied");
 256 #endif
 257                 errx(1, "who are you?");
 258         }
 259
 260         username = strdup(pwd->pw_name);
 261         if (username == NULL)
 262                 err(1, "strdup failure");
 263
 264         if (asme) {
 265                 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
 266                         /* must copy - pwd memory is recycled */
 267                         shell = strncpy(shellbuf, pwd->pw_shell,
 268                             sizeof(shellbuf));
 269                         shellbuf[sizeof(shellbuf) - 1] = '\0';
 270                 }
 271                 else {
 272                         shell = _PATH_BSHELL;
 273                         iscsh = NO;
 274                 }
 275         }
 276
 277         /* Do the whole PAM startup thing */
 278         retcode = pam_start("su", user, &conv, &pamh);
 279         if (retcode != PAM_SUCCESS) {
 280                 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode));
 281                 errx(1, "pam_start: %s", pam_strerror(pamh, retcode));
 282         }
 283
 284         PAM_SET_ITEM(PAM_RUSER, username);
 285
 286         mytty = ttyname(STDERR_FILENO);
 287         if (!mytty)
 288                 mytty = "tty";
 289         PAM_SET_ITEM(PAM_TTY, mytty);
 290
 291         retcode = pam_authenticate(pamh, 0);
 292         if (retcode != PAM_SUCCESS) {
 293 #ifdef USE_BSM_AUDIT
 294                 if (audit_submit(AUE_su, auid, 1, EPERM, "bad su %s to %s on %s",
 295                     username, user, mytty))
 296                         errx(1, "Permission denied");
 297 #endif
 298                 syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s",
 299                     username, user, mytty);
 300                 errx(1, "Sorry");
 301         }
 302 #ifdef USE_BSM_AUDIT
 303         if (audit_submit(AUE_su, auid, 0, 0, "successful authentication"))
 304                 errx(1, "Permission denied");
 305 #endif
 306         retcode = pam_get_item(pamh, PAM_USER, &v);
 307         if (retcode == PAM_SUCCESS)
 308                 user = v;
 309         else
 310                 syslog(LOG_ERR, "pam_get_item(PAM_USER): %s",
 311                     pam_strerror(pamh, retcode));
 312         pwd = getpwnam(user);
 313         if (pwd == NULL) {
 314 #ifdef USE_BSM_AUDIT
 315                 if (audit_submit(AUE_su, auid, 1, EPERM,
 316                     "unknown subject: %s", user))
 317                         errx(1, "Permission denied");
 318 #endif
 319                 errx(1, "unknown login: %s", user);
 320         }
 321
 322         retcode = pam_acct_mgmt(pamh, 0);
 323         if (retcode == PAM_NEW_AUTHTOK_REQD) {
 324                 retcode = pam_chauthtok(pamh,
 325                         PAM_CHANGE_EXPIRED_AUTHTOK);
 326                 if (retcode != PAM_SUCCESS) {
 327 #ifdef USE_BSM_AUDIT
 328                         aerr = pam_strerror(pamh, retcode);
 329                         if (aerr == NULL)
 330                                 aerr = "Unknown PAM error";
 331                         if (audit_submit(AUE_su, auid, 1, EPERM,
 332                             "pam_chauthtok: %s", aerr))
 333                                 errx(1, "Permission denied");
 334 #endif
 335                         syslog(LOG_ERR, "pam_chauthtok: %s",
 336                             pam_strerror(pamh, retcode));
 337                         errx(1, "Sorry");
 338                 }
 339         }
 340         if (retcode != PAM_SUCCESS) {
 341 #ifdef USE_BSM_AUDIT
 342                 if (audit_submit(AUE_su, auid, 1, EPERM, "pam_acct_mgmt: %s",
 343                     pam_strerror(pamh, retcode)))
 344                         errx(1, "Permission denied");
 345 #endif
 346                 syslog(LOG_ERR, "pam_acct_mgmt: %s",
 347                         pam_strerror(pamh, retcode));
 348                 errx(1, "Sorry");
 349         }
 350
 351         /* get target login information */
 352         if (class == NULL)
 353                 lc = login_getpwclass(pwd);
 354         else {
 355                 if (ruid != 0) {
 356 #ifdef USE_BSM_AUDIT
 357                         if (audit_submit(AUE_su, auid, 1, EPERM,
 358                             "only root may use -c"))
 359                                 errx(1, "Permission denied");
 360 #endif
 361                         errx(1, "only root may use -c");
 362                 }
 363                 lc = login_getclass(class);
 364                 if (lc == NULL)
 365                         errx(1, "unknown class: %s", class);
 366         }
 367
 368         /* if asme and non-standard target shell, must be root */
 369         if (asme) {
 370                 if (ruid != 0 && !chshell(pwd->pw_shell))
 371                         errx(1, "permission denied (shell)");
 372         }
 373         else if (pwd->pw_shell && *pwd->pw_shell) {
 374                 shell = pwd->pw_shell;
 375                 iscsh = UNSET;
 376         }
 377         else {
 378                 shell = _PATH_BSHELL;
 379                 iscsh = NO;
 380         }
 381
 382         /* if we're forking a csh, we want to slightly muck the args */
 383         if (iscsh == UNSET) {
 384                 p = strrchr(shell, '/');
 385                 if (p)
 386                         ++p;
 387                 else
 388                         p = shell;
 389                 iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES;
 390         }
 391         setpriority(PRIO_PROCESS, 0, prio);
 392
 393         /*
 394          * PAM modules might add supplementary groups in pam_setcred(), so
 395          * initialize them first.
 396          */
 397         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0)
 398                 err(1, "setusercontext");
 399
 400         retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
 401         if (retcode != PAM_SUCCESS) {
 402                 syslog(LOG_ERR, "pam_setcred: %s",
 403                     pam_strerror(pamh, retcode));
 404                 errx(1, "failed to establish credentials.");
 405         }
 406         if (asthem) {
 407                 retcode = pam_open_session(pamh, 0);
 408                 if (retcode != PAM_SUCCESS) {
 409                         syslog(LOG_ERR, "pam_open_session: %s",
 410                             pam_strerror(pamh, retcode));
 411                         errx(1, "failed to open session.");
 412                 }
 413         }
 414
 415         /*
 416          * We must fork() before setuid() because we need to call
 417          * pam_setcred(pamh, PAM_DELETE_CRED) as root.
 418          */
 419         sa.sa_flags = SA_RESTART;
 420         sa.sa_handler = SIG_IGN;
 421         sigemptyset(&sa.sa_mask);
 422         sigaction(SIGINT, &sa, &sa_int);
 423         sigaction(SIGQUIT, &sa, &sa_quit);
 424         sigaction(SIGPIPE, &sa, &sa_pipe);
 425         sa.sa_handler = SIG_DFL;
 426         sigaction(SIGTSTP, &sa, NULL);
 427         statusp = 1;
 428         if (pipe(fds) == -1) {
 429                 PAM_END();
 430                 err(1, "pipe");
 431         }
 432         child_pid = fork();
 433         switch (child_pid) {
 434         default:
 435                 sa.sa_handler = SIG_IGN;
 436                 sigaction(SIGTTOU, &sa, NULL);
 437                 close(fds[0]);
 438                 setpgid(child_pid, child_pid);
 439                 if (tcgetpgrp(STDERR_FILENO) == getpgrp())
 440                         tcsetpgrp(STDERR_FILENO, child_pid);
 441                 close(fds[1]);
 442                 sigaction(SIGPIPE, &sa_pipe, NULL);
 443                 while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) {
 444                         if (WIFSTOPPED(statusp)) {
 445                                 child_pgrp = getpgid(child_pid);
 446                                 if (tcgetpgrp(STDERR_FILENO) == child_pgrp)
 447                                         tcsetpgrp(STDERR_FILENO, getpgrp());
 448                                 kill(getpid(), SIGSTOP);
 449                                 if (tcgetpgrp(STDERR_FILENO) == getpgrp()) {
 450                                         child_pgrp = getpgid(child_pid);
 451                                         tcsetpgrp(STDERR_FILENO, child_pgrp);
 452                                 }
 453                                 kill(child_pid, SIGCONT);
 454                                 statusp = 1;
 455                                 continue;
 456                         }
 457                         break;
 458                 }
 459                 tcsetpgrp(STDERR_FILENO, getpgrp());
 460                 if (pid == -1)
 461                         err(1, "waitpid");
 462                 PAM_END();
 463                 exit(WEXITSTATUS(statusp));
 464         case -1:
 465                 PAM_END();
 466                 err(1, "fork");
 467         case 0:
 468                 close(fds[1]);
 469                 read(fds[0], &temp, 1);
 470                 close(fds[0]);
 471                 sigaction(SIGPIPE, &sa_pipe, NULL);
 472                 sigaction(SIGINT, &sa_int, NULL);
 473                 sigaction(SIGQUIT, &sa_quit, NULL);
 474
 475                 /*
 476                  * Set all user context except for: Environmental variables
 477                  * Umask Login records (wtmpx, etc) Path
 478                  * XXX Missing LOGIN_SETMAC
 479                  */
 480                 setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK |
 481                            LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP);
 482 #if 0
 483                 /*
 484                  * If -s is present, also set the MAC label.
 485                  */
 486                 if (setmaclabel)
 487                         setwhat |= LOGIN_SETMAC;
 488 #endif
 489                 /*
 490                  * Don't touch resource/priority settings if -m has been used
 491                  * or -l and -c hasn't, and we're not su'ing to root.
 492                  */
 493                 if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
 494                         setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES);
 495                 if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
 496                         err(1, "setusercontext");
 497
 498                 if (!asme) {
 499                         if (asthem) {
 500                                 p = getenv("TERM");
 501                                 environ = &cleanenv;
 502                         }
 503
 504                         if (asthem || pwd->pw_uid) {
 505                                 if (setenv("USER", pwd->pw_name, 1) == -1) {
 506                                         err(1, "setenv: cannot set USER=%s",
 507                                             pwd->pw_name);
 508                                 }
 509                         }
 510                         if (setenv("HOME", pwd->pw_dir, 1) == -1) {
 511                                 err(1, "setenv: cannot set HOME=%s",
 512                                     pwd->pw_dir);
 513                         }
 514                         if (setenv("SHELL", shell, 1) == -1)
 515                                 err(1, "setenv: cannot set SHELL=%s", shell);
 516
 517                         if (asthem) {
 518                                 /*
 519                                  * Add any environmental variables that the
 520                                  * PAM modules may have set.
 521                                  */
 522                                 environ_pam = pam_getenvlist(pamh);
 523                                 if (environ_pam)
 524                                         export_pam_environment();
 525
 526                                 /* set the su'd user's environment & umask */
 527                                 setusercontext(lc, pwd, pwd->pw_uid,
 528                                         LOGIN_SETPATH | LOGIN_SETUMASK |
 529                                         LOGIN_SETENV);
 530                                 if (p) {
 531                                         if (setenv("TERM", p, 1) == -1) {
 532                                                 err(1,
 533                                                     "setenv: cannot set TERM=%s",
 534                                                     p);
 535                                         }
 536                                 }
 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
 563 static void
 564 export_pam_environment(void)
 565 {
 566         char    **pp;
 567         char    *p;
 568
 569         for (pp = environ_pam; *pp != NULL; pp++) {
 570                 if (ok_to_export(*pp)) {
 571                         p = strchr(*pp, '=');
 572                         *p = '\0';
 573                         if (setenv(*pp, p + 1, 1) == -1)
 574                                 err(1, "setenv: cannot set %s=%s", *pp, p + 1);
 575                 }
 576                 free(*pp);
 577         }
 578 }
 579
 580 /*
 581  * Sanity checks on PAM environmental variables:
 582  * - Make sure there is an '=' in the string.
 583  * - Make sure the string doesn't run on too long.
 584  * - Do not export certain variables.  This list was taken from the
 585  *   Solaris pam_putenv(3) man page.
 586  * Note that if the user is chrooted, PAM may have a better idea than we
 587  * do of where her home directory is.
 588  */
 589 static int
 590 ok_to_export(const char *s)
 591 {
 592         static const char *noexport[] = {
 593                 "SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH",
 594                 "IFS", "PATH", NULL
 595         };
 596         const char **pp;
 597         size_t n;
 598
 599         if (strlen(s) > 1024 || strchr(s, '=') == NULL)
 600                 return 0;
 601         if (strncmp(s, "LD_", 3) == 0)
 602                 return 0;
 603         for (pp = noexport; *pp != NULL; pp++) {
 604                 n = strlen(*pp);
 605                 if (s[n] == '=' && strncmp(s, *pp, n) == 0)
 606                         return 0;
 607         }
 608         return 1;
 609 }
 610
 611 static void
 612 usage(void)
 613 {
 614
 615         fprintf(stderr, "usage: su [-] [-flm] [-c class] [login [args]]\n");
 616         exit(1);
 617         /* NOTREACHED */
 618 }
 619
 620 static int
 621 chshell(const char *sh)
 622 {
 623         int r;
 624         char *cp;
 625
 626         r = 0;
 627         setusershell();
 628         while ((cp = getusershell()) != NULL && !r)
 629             r = (strcmp(cp, sh) == 0);
 630         endusershell();
 631         return r;
 632 }
 633
 634 static char *
 635 ontty(void)
 636 {
 637         char *p;
 638         static char buf[MAXPATHLEN + 4];
 639
 640         buf[0] = 0;
 641         p = ttyname(STDERR_FILENO);
 642         if (p)
 643                 snprintf(buf, sizeof(buf), " on %s", p);
 644         return buf;
 645 }