usr.bin/login/login.c

   1 /*-
   2  * Copyright (c) 1980, 1987, 1988, 1991, 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. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)login.c  8.4 (Berkeley) 4/2/94
  37  * $FreeBSD: src/usr.bin/login/login.c,v 1.106 2007/07/04 00:00:40 scf Exp $
  38  * $DragonFly: src/usr.bin/login/login.c,v 1.6 2006/01/12 13:43:11 corecode Exp $
  39  */
  40
  41 /*
  42  * login [ name ]
  43  * login -h hostname    (for telnetd, etc.)
  44  * login -f name        (for pre-authenticated login: datakit, xterm, etc.)
  45  */
  46
  47 #include <sys/copyright.h>
  48 #include <sys/param.h>
  49 #include <sys/file.h>
  50 #include <sys/stat.h>
  51 #include <sys/time.h>
  52 #include <sys/resource.h>
  53 #include <sys/wait.h>
  54
  55 #include <err.h>
  56 #include <errno.h>
  57 #include <grp.h>
  58 #include <libutil.h>
  59 #include <login_cap.h>
  60 #include <pwd.h>
  61 #include <setjmp.h>
  62 #include <signal.h>
  63 #include <stdio.h>
  64 #include <stdlib.h>
  65 #include <string.h>
  66 #include <syslog.h>
  67 #include <ttyent.h>
  68 #include <unistd.h>
  69
  70 #include <security/pam_appl.h>
  71 #include <security/openpam.h>
  72
  73 #include "login.h"
  74 #include "pathnames.h"
  75
  76 static int               auth_pam(void);
  77 static void              bail(int, int);
  78 static int               export(const char *);
  79 static void              export_pam_environment(void);
  80 static int               motd(const char *);
  81 static void              badlogin(char *);
  82 static char             *getloginname(void);
  83 static void              pam_syslog(const char *);
  84 static void              pam_cleanup(void);
  85 static void              refused(const char *, const char *, int);
  86 static const char       *stypeof(char *);
  87 static void              sigint(int);
  88 static void              timedout(int);
  89 static void              usage(void);
  90
  91 #define TTYGRPNAME              "tty"                   /* group to own ttys */
  92 #define DEFAULT_BACKOFF         3
  93 #define DEFAULT_RETRIES         10
  94 #define DEFAULT_PROMPT          "login: "
  95 #define DEFAULT_PASSWD_PROMPT   "Password:"
  96 #define TERM_UNKNOWN            "su"
  97 #define DEFAULT_WARN            (2L * 7L * 86400L)      /* Two weeks */
  98 #define NO_SLEEP_EXIT           0
  99 #define SLEEP_EXIT              5
 100
 101 /*
 102  * This bounds the time given to login.  Not a define so it can
 103  * be patched on machines where it's too small.
 104  */
 105 static u_int            timeout = 300;
 106
 107 /* Buffer for signal handling of timeout */
 108 static jmp_buf           timeout_buf;
 109
 110 struct passwd           *pwd;
 111 static int               failures;
 112
 113 static char             *envinit[1];    /* empty environment list */
 114
 115 /*
 116  * Command line flags and arguments
 117  */
 118 static int               fflag;         /* -f: do not perform authentication */
 119 static int               hflag;         /* -h: login from remote host */
 120 static char             *hostname;      /* hostname from command line */
 121 static int               pflag;         /* -p: preserve environment */
 122
 123 /*
 124  * User name
 125  */
 126 static char             *username;      /* user name */
 127 static char             *olduser;       /* previous user name */
 128
 129 /*
 130  * Prompts
 131  */
 132 static char              default_prompt[] = DEFAULT_PROMPT;
 133 static const char       *prompt;
 134 static char              default_passwd_prompt[] = DEFAULT_PASSWD_PROMPT;
 135 static const char       *passwd_prompt;
 136
 137 static char             *tty;
 138
 139 /*
 140  * PAM data
 141  */
 142 static pam_handle_t     *pamh = NULL;
 143 static struct pam_conv   pamc = { openpam_ttyconv, NULL };
 144 static int               pam_err;
 145 static int               pam_silent = PAM_SILENT;
 146 static int               pam_cred_established;
 147 static int               pam_session_established;
 148
 149 int
 150 main(int argc, char **argv)
 151 {
 152         struct group *gr;
 153         struct stat st;
 154         int retries, backoff;
 155         int ask, ch, cnt, quietlog, rootlogin, rval;
 156         uid_t uid, euid;
 157         gid_t egid;
 158         char *term;
 159         char *p, *ttyn;
 160         char tname[sizeof(_PATH_TTY) + 10];
 161         char *arg0;
 162         const char *tp;
 163         const char *shell = NULL;
 164         login_cap_t *lc = NULL;
 165         login_cap_t *lc_user = NULL;
 166         pid_t pid;
 167 #ifdef USE_BSM_AUDIT
 168         char auditsuccess = 1;
 169 #endif
 170
 171         signal(SIGQUIT, SIG_IGN);
 172         signal(SIGINT, SIG_IGN);
 173         signal(SIGHUP, SIG_IGN);
 174         if (setjmp(timeout_buf)) {
 175                 if (failures)
 176                         badlogin(username);
 177                 fprintf(stderr, "Login timed out after %d seconds\n",
 178                     timeout);
 179                 bail(NO_SLEEP_EXIT, 0);
 180         }
 181         signal(SIGALRM, timedout);
 182         alarm(timeout);
 183         setpriority(PRIO_PROCESS, 0, 0);
 184
 185         openlog("login", LOG_ODELAY, LOG_AUTH);
 186
 187         uid = getuid();
 188         euid = geteuid();
 189         egid = getegid();
 190
 191         while ((ch = getopt(argc, argv, "fh:p")) != -1)
 192                 switch (ch) {
 193                 case 'f':
 194                         fflag = 1;
 195                         break;
 196                 case 'h':
 197                         if (uid != 0)
 198                                 errx(1, "-h option: %s", strerror(EPERM));
 199                         if (strlen(optarg) >= MAXHOSTNAMELEN)
 200                                 errx(1, "-h option: %s: exceeds maximum "
 201                                     "hostname size", optarg);
 202                         hflag = 1;
 203                         hostname = optarg;
 204                         break;
 205                 case 'p':
 206                         pflag = 1;
 207                         break;
 208                 case '?':
 209                 default:
 210                         if (uid == 0)
 211                                 syslog(LOG_ERR, "invalid flag %c", ch);
 212                         usage();
 213                 }
 214         argc -= optind;
 215         argv += optind;
 216
 217         if (argc > 0) {
 218                 username = strdup(*argv);
 219                 if (username == NULL)
 220                         err(1, "strdup()");
 221                 ask = 0;
 222         } else {
 223                 ask = 1;
 224         }
 225
 226         setproctitle("-%s", getprogname());
 227
 228         for (cnt = getdtablesize(); cnt > 2; cnt--)
 229                 close(cnt);
 230
 231         /*
 232          * Get current TTY
 233          */
 234         ttyn = ttyname(STDIN_FILENO);
 235         if (ttyn == NULL || *ttyn == '\0') {
 236                 snprintf(tname, sizeof(tname), "%s??", _PATH_TTY);
 237                 ttyn = tname;
 238         }
 239         if (strncmp(ttyn, _PATH_DEV, sizeof(_PATH_DEV) -1) == 0)
 240                 tty = ttyn + sizeof(_PATH_DEV) -1;
 241         else
 242                 tty = ttyn;
 243
 244         /*
 245          * Get "login-retries" & "login-backoff" from default class
 246          */
 247         lc = login_getclass(NULL);
 248         prompt = login_getcapstr(lc, "login_prompt",
 249             default_prompt, default_prompt);
 250         passwd_prompt = login_getcapstr(lc, "passwd_prompt",
 251             default_passwd_prompt, default_passwd_prompt);
 252         retries = login_getcapnum(lc, "login-retries",
 253             DEFAULT_RETRIES, DEFAULT_RETRIES);
 254         backoff = login_getcapnum(lc, "login-backoff",
 255             DEFAULT_BACKOFF, DEFAULT_BACKOFF);
 256         login_close(lc);
 257         lc = NULL;
 258
 259         /*
 260          * Try to authenticate the user until we succeed or time out.
 261          */
 262         for (cnt = 0;; ask = 1) {
 263                 if (ask) {
 264                         fflag = 0;
 265                         if (olduser != NULL)
 266                                 free(olduser);
 267                         olduser = username;
 268                         username = getloginname();
 269                 }
 270                 rootlogin = 0;
 271
 272                 /*
 273                  * Note if trying multiple user names; log failures for
 274                  * previous user name, but don't bother logging one failure
 275                  * for nonexistent name (mistyped username).
 276                  */
 277                 if (failures && strcmp(olduser, username) != 0) {
 278                         if (failures > (pwd ? 0 : 1))
 279                                 badlogin(olduser);
 280                 }
 281
 282                 /*
 283                  * Load the PAM policy and set some variables
 284                  */
 285                 pam_err = pam_start("login", username, &pamc, &pamh);
 286                 if (pam_err != PAM_SUCCESS) {
 287                         pam_syslog("pam_start()");
 288 #ifdef USE_BSM_AUDIT
 289                         au_login_fail("PAM Error", 1);
 290 #endif
 291                         bail(NO_SLEEP_EXIT, 1);
 292                 }
 293                 pam_err = pam_set_item(pamh, PAM_TTY, tty);
 294                 if (pam_err != PAM_SUCCESS) {
 295                         pam_syslog("pam_set_item(PAM_TTY)");
 296 #ifdef USE_BSM_AUDIT
 297                         au_login_fail("PAM Error", 1);
 298 #endif
 299                         bail(NO_SLEEP_EXIT, 1);
 300                 }
 301                 pam_err = pam_set_item(pamh, PAM_RHOST, hostname);
 302                 if (pam_err != PAM_SUCCESS) {
 303                         pam_syslog("pam_set_item(PAM_RHOST)");
 304 #ifdef USE_BSM_AUDIT
 305                         au_login_fail("PAM Error", 1);
 306 #endif
 307                         bail(NO_SLEEP_EXIT, 1);
 308                 }
 309
 310                 pwd = getpwnam(username);
 311                 if (pwd != NULL && pwd->pw_uid == 0)
 312                         rootlogin = 1;
 313
 314                 /*
 315                  * If the -f option was specified and the caller is
 316                  * root or the caller isn't changing their uid, don't
 317                  * authenticate.
 318                  */
 319                 if (pwd != NULL && fflag &&
 320                     (uid == (uid_t)0 || uid == (uid_t)pwd->pw_uid)) {
 321                         /* already authenticated */
 322                         rval = 0;
 323 #ifdef USE_BSM_AUDIT
 324                         auditsuccess = 0; /* opened a terminal window only */
 325 #endif
 326                 } else {
 327                         fflag = 0;
 328                         setpriority(PRIO_PROCESS, 0, -4);
 329                         rval = auth_pam();
 330                         setpriority(PRIO_PROCESS, 0, 0);
 331                 }
 332
 333                 if (pwd && rval == 0)
 334                         break;
 335
 336                 pam_cleanup();
 337
 338                 /*
 339                  * We are not exiting here, but this corresponds to a failed
 340                  * login event, so set exitstatus to 1.
 341                  */
 342 #ifdef USE_BSM_AUDIT
 343                 au_login_fail("Login incorrect", 1);
 344 #endif
 345
 346                 printf("Login incorrect\n");
 347                 failures++;
 348
 349                 pwd = NULL;
 350
 351                 /*
 352                  * Allow up to 'retry' (10) attempts, but start
 353                  * backing off after 'backoff' (3) attempts.
 354                  */
 355                 if (++cnt > backoff) {
 356                         if (cnt >= retries) {
 357                                 badlogin(username);
 358                                 bail(SLEEP_EXIT, 1);
 359                         }
 360                         sleep((u_int)((cnt - backoff) * 5));
 361                 }
 362         }
 363
 364         /* committed to login -- turn off timeout */
 365         alarm((u_int)0);
 366         signal(SIGHUP, SIG_DFL);
 367
 368         endpwent();
 369
 370 #ifdef USE_BSM_AUDIT
 371         /* Audit successful login. */
 372         if (auditsuccess)
 373                 au_login_success();
 374 #endif
 375
 376         /*
 377          * Establish the login class.
 378          */
 379         lc = login_getpwclass(pwd);
 380         lc_user = login_getuserclass(pwd);
 381
 382         if (!(quietlog = login_getcapbool(lc_user, "hushlogin", 0)))
 383                 quietlog = login_getcapbool(lc, "hushlogin", 0);
 384
 385         /*
 386          * Switching needed for NFS with root access disabled.
 387          *
 388          * XXX: This change fails to modify the additional groups for the
 389          * process, and as such, may restrict rights normally granted
 390          * through those groups.
 391          */
 392         setegid(pwd->pw_gid);
 393         seteuid(rootlogin ? 0 : pwd->pw_uid);
 394         if (!*pwd->pw_dir || chdir(pwd->pw_dir) < 0) {
 395                 if (login_getcapbool(lc, "requirehome", 0))
 396                         refused("Home directory not available", "HOMEDIR", 1);
 397                 if (chdir("/") < 0)
 398                         refused("Cannot find root directory", "ROOTDIR", 1);
 399                 if (!quietlog || *pwd->pw_dir)
 400                         printf("No home directory.\nLogging in with home = \"/\".\n");
 401                 pwd->pw_dir = strdup("/");
 402                 if (pwd->pw_dir == NULL) {
 403                         syslog(LOG_NOTICE, "strdup(): %m");
 404                         bail(SLEEP_EXIT, 1);
 405                 }
 406         }
 407         seteuid(euid);
 408         setegid(egid);
 409         if (!quietlog) {
 410                 quietlog = access(_PATH_HUSHLOGIN, F_OK) == 0;
 411                 if (!quietlog)
 412                         pam_silent = 0;
 413         }
 414
 415         shell = login_getcapstr(lc, "shell", pwd->pw_shell, pwd->pw_shell);
 416         if (*pwd->pw_shell == '\0')
 417                 pwd->pw_shell = strdup(_PATH_BSHELL);
 418         if (pwd->pw_shell == NULL) {
 419                 syslog(LOG_NOTICE, "strdup(): %m");
 420                 bail(SLEEP_EXIT, 1);
 421         }
 422         if (*shell == '\0')   /* Not overridden */
 423                 shell = pwd->pw_shell;
 424         if ((shell = strdup(shell)) == NULL) {
 425                 syslog(LOG_NOTICE, "strdup(): %m");
 426                 bail(SLEEP_EXIT, 1);
 427         }
 428
 429         /*
 430          * Set device protections, depending on what terminal the
 431          * user is logged in. This feature is used on Suns to give
 432          * console users better privacy.
 433          */
 434         login_fbtab(tty, pwd->pw_uid, pwd->pw_gid);
 435
 436         /*
 437          * Clear flags of the tty.  None should be set, and when the
 438          * user sets them otherwise, this can cause the chown to fail.
 439          * Since it isn't clear that flags are useful on character
 440          * devices, we just clear them.
 441          *
 442          * We don't log in the case of EOPNOTSUPP because dev might be
 443          * on NFS, which doesn't support chflags.
 444          *
 445          * We don't log in the EROFS because that means that /dev is on
 446          * a read only file system and we assume that the permissions there
 447          * are sane.
 448          */
 449         if (ttyn != tname && chflags(ttyn, 0))
 450                 if (errno != EOPNOTSUPP && errno != EROFS)
 451                         syslog(LOG_ERR, "chflags(%s): %m", ttyn);
 452         if (ttyn != tname && chown(ttyn, pwd->pw_uid,
 453             (gr = getgrnam(TTYGRPNAME)) ? gr->gr_gid : pwd->pw_gid))
 454                 if (errno != EROFS)
 455                         syslog(LOG_ERR, "chown(%s): %m", ttyn);
 456
 457         /*
 458          * Exclude cons/vt/ptys only, assume dialup otherwise
 459          * TODO: Make dialup tty determination a library call
 460          * for consistency (finger etc.)
 461          */
 462         if (hflag && isdialuptty(tty))
 463                 syslog(LOG_INFO, "DIALUP %s, %s", tty, pwd->pw_name);
 464
 465 #ifdef LOGALL
 466         /*
 467          * Syslog each successful login, so we don't have to watch
 468          * hundreds of wtmp or lastlogin files.
 469          */
 470         if (hflag)
 471                 syslog(LOG_INFO, "login from %s on %s as %s",
 472                        hostname, tty, pwd->pw_name);
 473         else
 474                 syslog(LOG_INFO, "login on %s as %s",
 475                        tty, pwd->pw_name);
 476 #endif
 477
 478         /*
 479          * If fflag is on, assume caller/authenticator has logged root
 480          * login.
 481          */
 482         if (rootlogin && fflag == 0) {
 483                 if (hflag)
 484                         syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s FROM %s",
 485                             username, tty, hostname);
 486                 else
 487                         syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s",
 488                             username, tty);
 489         }
 490
 491         /*
 492          * Destroy environment unless user has requested its
 493          * preservation - but preserve TERM in all cases
 494          */
 495         term = getenv("TERM");
 496         if (!pflag)
 497                 environ = envinit;
 498         if (term != NULL) {
 499                 if (setenv("TERM", term, 0) == -1)
 500                         err(1, "setenv: cannot set TERM=%s", term);
 501         }
 502
 503         /*
 504          * PAM modules might add supplementary groups during pam_setcred().
 505          */
 506         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
 507                 syslog(LOG_ERR, "setusercontext() failed - exiting");
 508                 bail(NO_SLEEP_EXIT, 1);
 509         }
 510
 511         pam_err = pam_setcred(pamh, pam_silent|PAM_ESTABLISH_CRED);
 512         if (pam_err != PAM_SUCCESS) {
 513                 pam_syslog("pam_setcred()");
 514                 bail(NO_SLEEP_EXIT, 1);
 515         }
 516         pam_cred_established = 1;
 517
 518         pam_err = pam_open_session(pamh, pam_silent);
 519         if (pam_err != PAM_SUCCESS) {
 520                 pam_syslog("pam_open_session()");
 521                 bail(NO_SLEEP_EXIT, 1);
 522         }
 523         pam_session_established = 1;
 524
 525         /*
 526          * We must fork() before setuid() because we need to call
 527          * pam_close_session() as root.
 528          */
 529         pid = fork();
 530         if (pid < 0) {
 531                 err(1, "fork");
 532         } else if (pid != 0) {
 533                 /*
 534                  * Parent: wait for child to finish, then clean up
 535                  * session.
 536                  */
 537                 int status;
 538                 setproctitle("-%s [pam]", getprogname());
 539                 waitpid(pid, &status, 0);
 540                 bail(NO_SLEEP_EXIT, 0);
 541         }
 542
 543         /*
 544          * NOTICE: We are now in the child process!
 545          */
 546
 547         /*
 548          * Add any environment variables the PAM modules may have set.
 549          */
 550         export_pam_environment();
 551
 552         /*
 553          * We're done with PAM now; our parent will deal with the rest.
 554          */
 555         pam_end(pamh, 0);
 556         pamh = NULL;
 557
 558         /*
 559          * We don't need to be root anymore, so set the login name and
 560          * the UID.
 561          */
 562         if (setlogin(username) != 0) {
 563                 syslog(LOG_ERR, "setlogin(%s): %m - exiting", username);
 564                 bail(NO_SLEEP_EXIT, 1);
 565         }
 566         if (setusercontext(lc, pwd, pwd->pw_uid,
 567             LOGIN_SETALL & ~(LOGIN_SETLOGIN|LOGIN_SETGROUP)) != 0) {
 568                 syslog(LOG_ERR, "setusercontext() failed - exiting");
 569                 exit(1);
 570         }
 571
 572         if (setenv("SHELL", pwd->pw_shell, 1) == -1)
 573                 err(1, "setenv: cannot set SHELL=%s", pwd->pw_shell);
 574         if (setenv("HOME", pwd->pw_dir, 1) == -1)
 575                 err(1, "setenv: cannot set HOME=%s", pwd->pw_dir);
 576         /* Overwrite "term" from login.conf(5) for any known TERM */
 577         if (term == NULL && (tp = stypeof(tty)) != NULL) {
 578                 if (setenv("TERM", tp, 1) == -1)
 579                         err(1, "setenv: cannot set TERM=%s", tp);
 580         } else {
 581                 if (setenv("TERM", TERM_UNKNOWN, 0) == -1)
 582                         err(1, "setenv: cannot set TERM=%s", TERM_UNKNOWN);
 583         }
 584
 585         if (setenv("LOGNAME", username, 1) == -1)
 586                 err(1, "setenv: cannot set LOGNAME=%s", username);
 587         if (setenv("USER", username, 1) == -1)
 588                 err(1, "setenv: cannot set USER=%s", username);
 589         if (setenv("PATH",
 590             rootlogin ? _PATH_STDPATH : _PATH_DEFPATH, 0) == -1) {
 591                 err(1, "setenv: cannot set PATH=%s",
 592                     rootlogin ? _PATH_STDPATH : _PATH_DEFPATH);
 593         }
 594
 595         if (!quietlog) {
 596                 const char *cw;
 597
 598                 cw = login_getcapstr(lc, "copyright", NULL, NULL);
 599                 if (cw == NULL || motd(cw) == -1)
 600                         printf("%s", copyright);
 601
 602                 printf("\n");
 603
 604                 cw = login_getcapstr(lc, "welcome", NULL, NULL);
 605                 if (cw != NULL && access(cw, F_OK) == 0)
 606                         motd(cw);
 607                 else
 608                         motd(_PATH_MOTDFILE);
 609
 610                 if (login_getcapbool(lc_user, "nocheckmail", 0) == 0 &&
 611                     login_getcapbool(lc, "nocheckmail", 0) == 0) {
 612                         char *cx;
 613
 614                         /* $MAIL may have been set by class. */
 615                         cx = getenv("MAIL");
 616                         if (cx == NULL) {
 617                                 asprintf(&cx, "%s/%s",
 618                                     _PATH_MAILDIR, pwd->pw_name);
 619                         }
 620                         if (cx && stat(cx, &st) == 0 && st.st_size != 0)
 621                                 printf("You have %smail.\n",
 622                                     (st.st_mtime > st.st_atime) ? "new " : "");
 623                         if (getenv("MAIL") == NULL)
 624                                 free(cx);
 625                 }
 626         }
 627
 628         login_close(lc_user);
 629         login_close(lc);
 630
 631         signal(SIGALRM, SIG_DFL);
 632         signal(SIGQUIT, SIG_DFL);
 633         signal(SIGINT, SIG_DFL);
 634         signal(SIGTSTP, SIG_IGN);
 635
 636         /*
 637          * Login shells have a leading '-' in front of argv[0]
 638          */
 639         p = strrchr(pwd->pw_shell, '/');
 640         if (asprintf(&arg0, "-%s", p ? p + 1 : pwd->pw_shell) >= MAXPATHLEN) {
 641                 syslog(LOG_ERR, "user: %s: shell exceeds maximum pathname size",
 642                     username);
 643                 errx(1, "shell exceeds maximum pathname size");
 644         } else if (arg0 == NULL) {
 645                 err(1, "asprintf()");
 646         }
 647
 648         execlp(shell, arg0, NULL);
 649         err(1, "%s", shell);
 650
 651         /*
 652          * That's it, folks!
 653          */
 654 }
 655
 656 /*
 657  * Attempt to authenticate the user using PAM.  Returns 0 if the user is
 658  * authenticated, or 1 if not authenticated.  If some sort of PAM system
 659  * error occurs (e.g., the "/etc/pam.conf" file is missing) then this
 660  * function returns -1.  This can be used as an indication that we should
 661  * fall back to a different authentication mechanism.
 662  */
 663 static int
 664 auth_pam(void)
 665 {
 666         const char *tmpl_user;
 667         const void *item;
 668         int rval;
 669
 670         pam_err = pam_authenticate(pamh, pam_silent);
 671         switch (pam_err) {
 672
 673         case PAM_SUCCESS:
 674                 /*
 675                  * With PAM we support the concept of a "template"
 676                  * user.  The user enters a login name which is
 677                  * authenticated by PAM, usually via a remote service
 678                  * such as RADIUS or TACACS+.  If authentication
 679                  * succeeds, a different but related "template" name
 680                  * is used for setting the credentials, shell, and
 681                  * home directory.  The name the user enters need only
 682                  * exist on the remote authentication server, but the
 683                  * template name must be present in the local password
 684                  * database.
 685                  *
 686                  * This is supported by two various mechanisms in the
 687                  * individual modules.  However, from the application's
 688                  * point of view, the template user is always passed
 689                  * back as a changed value of the PAM_USER item.
 690                  */
 691                 pam_err = pam_get_item(pamh, PAM_USER, &item);
 692                 if (pam_err == PAM_SUCCESS) {
 693                         tmpl_user = (const char *)item;
 694                         if (strcmp(username, tmpl_user) != 0)
 695                                 pwd = getpwnam(tmpl_user);
 696                 } else {
 697                         pam_syslog("pam_get_item(PAM_USER)");
 698                 }
 699                 rval = 0;
 700                 break;
 701
 702         case PAM_AUTH_ERR:
 703         case PAM_USER_UNKNOWN:
 704         case PAM_MAXTRIES:
 705                 rval = 1;
 706                 break;
 707
 708         default:
 709                 pam_syslog("pam_authenticate()");
 710                 rval = -1;
 711                 break;
 712         }
 713
 714         if (rval == 0) {
 715                 pam_err = pam_acct_mgmt(pamh, pam_silent);
 716                 switch (pam_err) {
 717                 case PAM_SUCCESS:
 718                         break;
 719                 case PAM_NEW_AUTHTOK_REQD:
 720                         pam_err = pam_chauthtok(pamh,
 721                             pam_silent|PAM_CHANGE_EXPIRED_AUTHTOK);
 722                         if (pam_err != PAM_SUCCESS) {
 723                                 pam_syslog("pam_chauthtok()");
 724                                 rval = 1;
 725                         }
 726                         break;
 727                 default:
 728                         pam_syslog("pam_acct_mgmt()");
 729                         rval = 1;
 730                         break;
 731                 }
 732         }
 733
 734         if (rval != 0) {
 735                 pam_end(pamh, pam_err);
 736                 pamh = NULL;
 737         }
 738         return (rval);
 739 }
 740
 741 /*
 742  * Export any environment variables PAM modules may have set
 743  */
 744 static void
 745 export_pam_environment(void)
 746 {
 747         char **pam_env;
 748         char **pp;
 749
 750         pam_env = pam_getenvlist(pamh);
 751         if (pam_env != NULL) {
 752                 for (pp = pam_env; *pp != NULL; pp++) {
 753                         export(*pp);
 754                         free(*pp);
 755                 }
 756         }
 757 }
 758
 759 /*
 760  * Perform sanity checks on an environment variable:
 761  * - Make sure there is an '=' in the string.
 762  * - Make sure the string doesn't run on too long.
 763  * - Do not export certain variables.  This list was taken from the
 764  *   Solaris pam_putenv(3) man page.
 765  * Then export it.
 766  */
 767 static int
 768 export(const char *s)
 769 {
 770         static const char *noexport[] = {
 771                 "SHELL", "HOME", "LOGNAME", "MAIL", "CDPATH",
 772                 "IFS", "PATH", NULL
 773         };
 774         char *p;
 775         const char **pp;
 776         size_t n;
 777
 778         if (strlen(s) > 1024 || (p = strchr(s, '=')) == NULL)
 779                 return (0);
 780         if (strncmp(s, "LD_", 3) == 0)
 781                 return (0);
 782         for (pp = noexport; *pp != NULL; pp++) {
 783                 n = strlen(*pp);
 784                 if (s[n] == '=' && strncmp(s, *pp, n) == 0)
 785                         return (0);
 786         }
 787         *p = '\0';
 788         if (setenv(s, p + 1, 1) == -1)
 789                 err(1, "setenv: cannot set %s=%s", s, p + 1);
 790         *p = '=';
 791         return (1);
 792 }
 793
 794 static void
 795 usage(void)
 796 {
 797
 798         fprintf(stderr, "usage: login [-fp] [-h hostname] [username]\n");
 799         exit(1);
 800 }
 801
 802 /*
 803  * Prompt user and read login name from stdin.
 804  */
 805 static char *
 806 getloginname(void)
 807 {
 808         char *nbuf, *p;
 809         int ch;
 810
 811         nbuf = malloc(MAXLOGNAME);
 812         if (nbuf == NULL)
 813                 err(1, "malloc()");
 814         do {
 815                 printf("%s", prompt);
 816                 for (p = nbuf; (ch = getchar()) != '\n'; ) {
 817                         if (ch == EOF) {
 818                                 badlogin(username);
 819                                 bail(NO_SLEEP_EXIT, 0);
 820                         }
 821                         if (p < nbuf + MAXLOGNAME - 1)
 822                                 *p++ = ch;
 823                 }
 824         } while (p == nbuf);
 825
 826         *p = '\0';
 827         if (nbuf[0] == '-') {
 828                 pam_silent = 0;
 829                 memmove(nbuf, nbuf + 1, strlen(nbuf));
 830         } else {
 831                 pam_silent = PAM_SILENT;
 832         }
 833         return nbuf;
 834 }
 835
 836 /*
 837  * SIGINT handler for motd().
 838  */
 839 static volatile int motdinterrupt;
 840 static void
 841 sigint(int signo __unused)
 842 {
 843         motdinterrupt = 1;
 844 }
 845
 846 /*
 847  * Display the contents of a file (such as /etc/motd).
 848  */
 849 static int
 850 motd(const char *motdfile)
 851 {
 852         sig_t oldint;
 853         FILE *f;
 854         int ch;
 855
 856         if ((f = fopen(motdfile, "r")) == NULL)
 857                 return (-1);
 858         motdinterrupt = 0;
 859         oldint = signal(SIGINT, sigint);
 860         while ((ch = fgetc(f)) != EOF && !motdinterrupt)
 861                 putchar(ch);
 862         signal(SIGINT, oldint);
 863         if (ch != EOF || ferror(f)) {
 864                 fclose(f);
 865                 return (-1);
 866         }
 867         fclose(f);
 868         return (0);
 869 }
 870
 871 /*
 872  * SIGALRM handler, to enforce login prompt timeout.
 873  *
 874  * XXX This can potentially confuse the hell out of PAM.  We should
 875  * XXX instead implement a conversation function that returns
 876  * XXX PAM_CONV_ERR when interrupted by a signal, and have the signal
 877  * XXX handler just set a flag.
 878  */
 879 static void
 880 timedout(int signo __unused)
 881 {
 882
 883         longjmp(timeout_buf, signo);
 884 }
 885
 886 static void
 887 badlogin(char *name)
 888 {
 889
 890         if (failures == 0)
 891                 return;
 892         if (hflag) {
 893                 syslog(LOG_NOTICE, "%d LOGIN FAILURE%s FROM %s",
 894                     failures, failures > 1 ? "S" : "", hostname);
 895                 syslog(LOG_AUTHPRIV|LOG_NOTICE,
 896                     "%d LOGIN FAILURE%s FROM %s, %s",
 897                     failures, failures > 1 ? "S" : "", hostname, name);
 898         } else {
 899                 syslog(LOG_NOTICE, "%d LOGIN FAILURE%s ON %s",
 900                     failures, failures > 1 ? "S" : "", tty);
 901                 syslog(LOG_AUTHPRIV|LOG_NOTICE,
 902                     "%d LOGIN FAILURE%s ON %s, %s",
 903                     failures, failures > 1 ? "S" : "", tty, name);
 904         }
 905         failures = 0;
 906 }
 907
 908 const char *
 909 stypeof(char *ttyid)
 910 {
 911         struct ttyent *t;
 912
 913         if (ttyid != NULL && *ttyid != '\0') {
 914                 t = getttynam(ttyid);
 915                 if (t != NULL && t->ty_type != NULL)
 916                         return (t->ty_type);
 917         }
 918         return (NULL);
 919 }
 920
 921 static void
 922 refused(const char *msg, const char *rtype, int lout)
 923 {
 924
 925         if (msg != NULL)
 926             printf("%s.\n", msg);
 927         if (hflag)
 928                 syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) FROM %s ON TTY %s",
 929                     pwd->pw_name, rtype, hostname, tty);
 930         else
 931                 syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) ON TTY %s",
 932                     pwd->pw_name, rtype, tty);
 933         if (lout)
 934                 bail(SLEEP_EXIT, 1);
 935 }
 936
 937 /*
 938  * Log a PAM error
 939  */
 940 static void
 941 pam_syslog(const char *msg)
 942 {
 943         syslog(LOG_ERR, "%s: %s", msg, pam_strerror(pamh, pam_err));
 944 }
 945
 946 /*
 947  * Shut down PAM
 948  */
 949 static void
 950 pam_cleanup(void)
 951 {
 952
 953         if (pamh != NULL) {
 954                 if (pam_session_established) {
 955                         pam_err = pam_close_session(pamh, 0);
 956                         if (pam_err != PAM_SUCCESS)
 957                                 pam_syslog("pam_close_session()");
 958                 }
 959                 pam_session_established = 0;
 960                 if (pam_cred_established) {
 961                         pam_err = pam_setcred(pamh, pam_silent|PAM_DELETE_CRED);
 962                         if (pam_err != PAM_SUCCESS)
 963                                 pam_syslog("pam_setcred()");
 964                 }
 965                 pam_cred_established = 0;
 966                 pam_end(pamh, pam_err);
 967                 pamh = NULL;
 968         }
 969 }
 970
 971 /*
 972  * Exit, optionally after sleeping a few seconds
 973  */
 974 void
 975 bail(int sec, int eval)
 976 {
 977
 978         pam_cleanup();
 979 #ifdef USE_BSM_AUDIT
 980         if (pwd != NULL)
 981                 audit_logout();
 982 #endif
 983         sleep(sec);
 984         exit(eval);
 985 }