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. 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  * @(#)login.c  8.4 (Berkeley) 4/2/94
  41  * $FreeBSD: src/usr.bin/login/login.c,v 1.106 2007/07/04 00:00:40 scf Exp $
  42  * $DragonFly: src/usr.bin/login/login.c,v 1.6 2006/01/12 13:43:11 corecode Exp $
  43  */
  44
  45 /*
  46  * login [ name ]
  47  * login -h hostname    (for telnetd, etc.)
  48  * login -f name        (for pre-authenticated login: datakit, xterm, etc.)
  49  */
  50
  51 #include <sys/copyright.h>
  52 #include <sys/param.h>
  53 #include <sys/file.h>
  54 #include <sys/stat.h>
  55 #include <sys/time.h>
  56 #include <sys/resource.h>
  57 #include <sys/wait.h>
  58
  59 #include <err.h>
  60 #include <errno.h>
  61 #include <grp.h>
  62 #include <libutil.h>
  63 #include <login_cap.h>
  64 #include <pwd.h>
  65 #include <setjmp.h>
  66 #include <signal.h>
  67 #include <stdio.h>
  68 #include <stdlib.h>
  69 #include <string.h>
  70 #include <syslog.h>
  71 #include <ttyent.h>
  72 #include <unistd.h>
  73
  74 #include <security/pam_appl.h>
  75 #include <security/openpam.h>
  76
  77 #include "login.h"
  78 #include "pathnames.h"
  79
  80 static int               auth_pam(void);
  81 static void              bail(int, int);
  82 static int               export(const char *);
  83 static void              export_pam_environment(void);
  84 static int               motd(const char *);
  85 static void              badlogin(char *);
  86 static char             *getloginname(void);
  87 static void              pam_syslog(const char *);
  88 static void              pam_cleanup(void);
  89 static void              refused(const char *, const char *, int);
  90 static const char       *stypeof(char *);
  91 static void              sigint(int);
  92 static void              timedout(int);
  93 static void              usage(void);
  94
  95 #define TTYGRPNAME              "tty"                   /* group to own ttys */
  96 #define DEFAULT_BACKOFF         3
  97 #define DEFAULT_RETRIES         10
  98 #define DEFAULT_PROMPT          "login: "
  99 #define DEFAULT_PASSWD_PROMPT   "Password:"
 100 #define TERM_UNKNOWN            "su"
 101 #define DEFAULT_WARN            (2L * 7L * 86400L)      /* Two weeks */
 102 #define NO_SLEEP_EXIT           0
 103 #define SLEEP_EXIT              5
 104
 105 /*
 106  * This bounds the time given to login.  Not a define so it can
 107  * be patched on machines where it's too small.
 108  */
 109 static u_int            timeout = 300;
 110
 111 /* Buffer for signal handling of timeout */
 112 static jmp_buf           timeout_buf;
 113
 114 struct passwd           *pwd;
 115 static int               failures;
 116
 117 static char             *envinit[1];    /* empty environment list */
 118
 119 /*
 120  * Command line flags and arguments
 121  */
 122 static int               fflag;         /* -f: do not perform authentication */
 123 static int               hflag;         /* -h: login from remote host */
 124 static char             *hostname;      /* hostname from command line */
 125 static int               pflag;         /* -p: preserve environment */
 126
 127 /*
 128  * User name
 129  */
 130 static char             *username;      /* user name */
 131 static char             *olduser;       /* previous user name */
 132
 133 /*
 134  * Prompts
 135  */
 136 static char              default_prompt[] = DEFAULT_PROMPT;
 137 static const char       *prompt;
 138 static char              default_passwd_prompt[] = DEFAULT_PASSWD_PROMPT;
 139 static const char       *passwd_prompt;
 140
 141 static char             *tty;
 142
 143 /*
 144  * PAM data
 145  */
 146 static pam_handle_t     *pamh = NULL;
 147 static struct pam_conv   pamc = { openpam_ttyconv, NULL };
 148 static int               pam_err;
 149 static int               pam_silent = PAM_SILENT;
 150 static int               pam_cred_established;
 151 static int               pam_session_established;
 152
 153 int
 154 main(int argc, char **argv)
 155 {
 156         struct group *gr;
 157         struct stat st;
 158         int retries, backoff;
 159         int ask, ch, cnt, quietlog, rootlogin, rval;
 160         uid_t uid, euid;
 161         gid_t egid;
 162         char *term;
 163         char *p, *ttyn;
 164         char tname[sizeof(_PATH_TTY) + 10];
 165         char *arg0;
 166         const char *tp;
 167         const char *shell = NULL;
 168         login_cap_t *lc = NULL;
 169         login_cap_t *lc_user = NULL;
 170         pid_t pid;
 171 #ifdef USE_BSM_AUDIT
 172         char auditsuccess = 1;
 173 #endif
 174
 175         signal(SIGQUIT, SIG_IGN);
 176         signal(SIGINT, SIG_IGN);
 177         signal(SIGHUP, SIG_IGN);
 178         if (setjmp(timeout_buf)) {
 179                 if (failures)
 180                         badlogin(username);
 181                 fprintf(stderr, "Login timed out after %d seconds\n",
 182                     timeout);
 183                 bail(NO_SLEEP_EXIT, 0);
 184         }
 185         signal(SIGALRM, timedout);
 186         alarm(timeout);
 187         setpriority(PRIO_PROCESS, 0, 0);
 188
 189         openlog("login", LOG_ODELAY, LOG_AUTH);
 190
 191         uid = getuid();
 192         euid = geteuid();
 193         egid = getegid();
 194
 195         while ((ch = getopt(argc, argv, "fh:p")) != -1)
 196                 switch (ch) {
 197                 case 'f':
 198                         fflag = 1;
 199                         break;
 200                 case 'h':
 201                         if (uid != 0)
 202                                 errx(1, "-h option: %s", strerror(EPERM));
 203                         if (strlen(optarg) >= MAXHOSTNAMELEN)
 204                                 errx(1, "-h option: %s: exceeds maximum "
 205                                     "hostname size", optarg);
 206                         hflag = 1;
 207                         hostname = optarg;
 208                         break;
 209                 case 'p':
 210                         pflag = 1;
 211                         break;
 212                 case '?':
 213                 default:
 214                         if (uid == 0)
 215                                 syslog(LOG_ERR, "invalid flag %c", ch);
 216                         usage();
 217                 }
 218         argc -= optind;
 219         argv += optind;
 220
 221         if (argc > 0) {
 222                 username = strdup(*argv);
 223                 if (username == NULL)
 224                         err(1, "strdup()");
 225                 ask = 0;
 226         } else {
 227                 ask = 1;
 228         }
 229
 230         setproctitle("-%s", getprogname());
 231
 232         for (cnt = getdtablesize(); cnt > 2; cnt--)
 233                 close(cnt);
 234
 235         /*
 236          * Get current TTY
 237          */
 238         ttyn = ttyname(STDIN_FILENO);
 239         if (ttyn == NULL || *ttyn == '\0') {
 240                 snprintf(tname, sizeof(tname), "%s??", _PATH_TTY);
 241                 ttyn = tname;
 242         }
 243         if ((tty = strrchr(ttyn, '/')) != NULL)
 244                 ++tty;
 245         else
 246                 tty = ttyn;
 247
 248         /*
 249          * Get "login-retries" & "login-backoff" from default class
 250          */
 251         lc = login_getclass(NULL);
 252         prompt = login_getcapstr(lc, "login_prompt",
 253             default_prompt, default_prompt);
 254         passwd_prompt = login_getcapstr(lc, "passwd_prompt",
 255             default_passwd_prompt, default_passwd_prompt);
 256         retries = login_getcapnum(lc, "login-retries",
 257             DEFAULT_RETRIES, DEFAULT_RETRIES);
 258         backoff = login_getcapnum(lc, "login-backoff",
 259             DEFAULT_BACKOFF, DEFAULT_BACKOFF);
 260         login_close(lc);
 261         lc = NULL;
 262
 263         /*
 264          * Try to authenticate the user until we succeed or time out.
 265          */
 266         for (cnt = 0;; ask = 1) {
 267                 if (ask) {
 268                         fflag = 0;
 269                         if (olduser != NULL)
 270                                 free(olduser);
 271                         olduser = username;
 272                         username = getloginname();
 273                 }
 274                 rootlogin = 0;
 275
 276                 /*
 277                  * Note if trying multiple user names; log failures for
 278                  * previous user name, but don't bother logging one failure
 279                  * for nonexistent name (mistyped username).
 280                  */
 281                 if (failures && strcmp(olduser, username) != 0) {
 282                         if (failures > (pwd ? 0 : 1))
 283                                 badlogin(olduser);
 284                 }
 285
 286                 /*
 287                  * Load the PAM policy and set some variables
 288                  */
 289                 pam_err = pam_start("login", username, &pamc, &pamh);
 290                 if (pam_err != PAM_SUCCESS) {
 291                         pam_syslog("pam_start()");
 292 #ifdef USE_BSM_AUDIT
 293                         au_login_fail("PAM Error", 1);
 294 #endif
 295                         bail(NO_SLEEP_EXIT, 1);
 296                 }
 297                 pam_err = pam_set_item(pamh, PAM_TTY, tty);
 298                 if (pam_err != PAM_SUCCESS) {
 299                         pam_syslog("pam_set_item(PAM_TTY)");
 300 #ifdef USE_BSM_AUDIT
 301                         au_login_fail("PAM Error", 1);
 302 #endif
 303                         bail(NO_SLEEP_EXIT, 1);
 304                 }
 305                 pam_err = pam_set_item(pamh, PAM_RHOST, hostname);
 306                 if (pam_err != PAM_SUCCESS) {
 307                         pam_syslog("pam_set_item(PAM_RHOST)");
 308 #ifdef USE_BSM_AUDIT
 309                         au_login_fail("PAM Error", 1);
 310 #endif
 311                         bail(NO_SLEEP_EXIT, 1);
 312                 }
 313
 314                 pwd = getpwnam(username);
 315                 if (pwd != NULL && pwd->pw_uid == 0)
 316                         rootlogin = 1;
 317
 318                 /*
 319                  * If the -f option was specified and the caller is
 320                  * root or the caller isn't changing their uid, don't
 321                  * authenticate.
 322                  */
 323                 if (pwd != NULL && fflag &&
 324                     (uid == (uid_t)0 || uid == (uid_t)pwd->pw_uid)) {
 325                         /* already authenticated */
 326                         rval = 0;
 327 #ifdef USE_BSM_AUDIT
 328                         auditsuccess = 0; /* opened a terminal window only */
 329 #endif
 330                 } else {
 331                         fflag = 0;
 332                         setpriority(PRIO_PROCESS, 0, -4);
 333                         rval = auth_pam();
 334                         setpriority(PRIO_PROCESS, 0, 0);
 335                 }
 336
 337                 if (pwd && rval == 0)
 338                         break;
 339
 340                 pam_cleanup();
 341
 342                 /*
 343                  * We are not exiting here, but this corresponds to a failed
 344                  * login event, so set exitstatus to 1.
 345                  */
 346 #ifdef USE_BSM_AUDIT
 347                 au_login_fail("Login incorrect", 1);
 348 #endif
 349
 350                 printf("Login incorrect\n");
 351                 failures++;
 352
 353                 pwd = NULL;
 354
 355                 /*
 356                  * Allow up to 'retry' (10) attempts, but start
 357                  * backing off after 'backoff' (3) attempts.
 358                  */
 359                 if (++cnt > backoff) {
 360                         if (cnt >= retries) {
 361                                 badlogin(username);
 362                                 bail(SLEEP_EXIT, 1);
 363                         }
 364                         sleep((u_int)((cnt - backoff) * 5));
 365                 }
 366         }
 367
 368         /* committed to login -- turn off timeout */
 369         alarm((u_int)0);
 370         signal(SIGHUP, SIG_DFL);
 371
 372         endpwent();
 373
 374 #ifdef USE_BSM_AUDIT
 375         /* Audit successful login. */
 376         if (auditsuccess)
 377                 au_login_success();
 378 #endif
 379
 380         /*
 381          * Establish the login class.
 382          */
 383         lc = login_getpwclass(pwd);
 384         lc_user = login_getuserclass(pwd);
 385
 386         if (!(quietlog = login_getcapbool(lc_user, "hushlogin", 0)))
 387                 quietlog = login_getcapbool(lc, "hushlogin", 0);
 388
 389         /*
 390          * Switching needed for NFS with root access disabled.
 391          *
 392          * XXX: This change fails to modify the additional groups for the
 393          * process, and as such, may restrict rights normally granted
 394          * through those groups.
 395          */
 396         setegid(pwd->pw_gid);
 397         seteuid(rootlogin ? 0 : pwd->pw_uid);
 398         if (!*pwd->pw_dir || chdir(pwd->pw_dir) < 0) {
 399                 if (login_getcapbool(lc, "requirehome", 0))
 400                         refused("Home directory not available", "HOMEDIR", 1);
 401                 if (chdir("/") < 0)
 402                         refused("Cannot find root directory", "ROOTDIR", 1);
 403                 if (!quietlog || *pwd->pw_dir)
 404                         printf("No home directory.\nLogging in with home = \"/\".\n");
 405                 pwd->pw_dir = strdup("/");
 406                 if (pwd->pw_dir == NULL) {
 407                         syslog(LOG_NOTICE, "strdup(): %m");
 408                         bail(SLEEP_EXIT, 1);
 409                 }
 410         }
 411         seteuid(euid);
 412         setegid(egid);
 413         if (!quietlog) {
 414                 quietlog = access(_PATH_HUSHLOGIN, F_OK) == 0;
 415                 if (!quietlog)
 416                         pam_silent = 0;
 417         }
 418
 419         shell = login_getcapstr(lc, "shell", pwd->pw_shell, pwd->pw_shell);
 420         if (*pwd->pw_shell == '\0')
 421                 pwd->pw_shell = strdup(_PATH_BSHELL);
 422         if (pwd->pw_shell == NULL) {
 423                 syslog(LOG_NOTICE, "strdup(): %m");
 424                 bail(SLEEP_EXIT, 1);
 425         }
 426         if (*shell == '\0')   /* Not overridden */
 427                 shell = pwd->pw_shell;
 428         if ((shell = strdup(shell)) == NULL) {
 429                 syslog(LOG_NOTICE, "strdup(): %m");
 430                 bail(SLEEP_EXIT, 1);
 431         }
 432
 433         /*
 434          * Set device protections, depending on what terminal the
 435          * user is logged in. This feature is used on Suns to give
 436          * console users better privacy.
 437          */
 438         login_fbtab(tty, pwd->pw_uid, pwd->pw_gid);
 439
 440         /*
 441          * Clear flags of the tty.  None should be set, and when the
 442          * user sets them otherwise, this can cause the chown to fail.
 443          * Since it isn't clear that flags are useful on character
 444          * devices, we just clear them.
 445          *
 446          * We don't log in the case of EOPNOTSUPP because dev might be
 447          * on NFS, which doesn't support chflags.
 448          *
 449          * We don't log in the EROFS because that means that /dev is on
 450          * a read only file system and we assume that the permissions there
 451          * are sane.
 452          */
 453         if (ttyn != tname && chflags(ttyn, 0))
 454                 if (errno != EOPNOTSUPP && errno != EROFS)
 455                         syslog(LOG_ERR, "chflags(%s): %m", ttyn);
 456         if (ttyn != tname && chown(ttyn, pwd->pw_uid,
 457             (gr = getgrnam(TTYGRPNAME)) ? gr->gr_gid : pwd->pw_gid))
 458                 if (errno != EROFS)
 459                         syslog(LOG_ERR, "chown(%s): %m", ttyn);
 460
 461         /*
 462          * Exclude cons/vt/ptys only, assume dialup otherwise
 463          * TODO: Make dialup tty determination a library call
 464          * for consistency (finger etc.)
 465          */
 466         if (hflag && isdialuptty(tty))
 467                 syslog(LOG_INFO, "DIALUP %s, %s", tty, pwd->pw_name);
 468
 469 #ifdef LOGALL
 470         /*
 471          * Syslog each successful login, so we don't have to watch
 472          * hundreds of wtmp or lastlogin files.
 473          */
 474         if (hflag)
 475                 syslog(LOG_INFO, "login from %s on %s as %s",
 476                        hostname, tty, pwd->pw_name);
 477         else
 478                 syslog(LOG_INFO, "login on %s as %s",
 479                        tty, pwd->pw_name);
 480 #endif
 481
 482         /*
 483          * If fflag is on, assume caller/authenticator has logged root
 484          * login.
 485          */
 486         if (rootlogin && fflag == 0) {
 487                 if (hflag)
 488                         syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s FROM %s",
 489                             username, tty, hostname);
 490                 else
 491                         syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s",
 492                             username, tty);
 493         }
 494
 495         /*
 496          * Destroy environment unless user has requested its
 497          * preservation - but preserve TERM in all cases
 498          */
 499         term = getenv("TERM");
 500         if (!pflag)
 501                 environ = envinit;
 502         if (term != NULL) {
 503                 if (setenv("TERM", term, 0) == -1)
 504                         err(1, "setenv: cannot set TERM=%s", term);
 505         }
 506
 507         /*
 508          * PAM modules might add supplementary groups during pam_setcred().
 509          */
 510         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
 511                 syslog(LOG_ERR, "setusercontext() failed - exiting");
 512                 bail(NO_SLEEP_EXIT, 1);
 513         }
 514
 515         pam_err = pam_setcred(pamh, pam_silent|PAM_ESTABLISH_CRED);
 516         if (pam_err != PAM_SUCCESS) {
 517                 pam_syslog("pam_setcred()");
 518                 bail(NO_SLEEP_EXIT, 1);
 519         }
 520         pam_cred_established = 1;
 521
 522         pam_err = pam_open_session(pamh, pam_silent);
 523         if (pam_err != PAM_SUCCESS) {
 524                 pam_syslog("pam_open_session()");
 525                 bail(NO_SLEEP_EXIT, 1);
 526         }
 527         pam_session_established = 1;
 528
 529         /*
 530          * We must fork() before setuid() because we need to call
 531          * pam_close_session() as root.
 532          */
 533         pid = fork();
 534         if (pid < 0) {
 535                 err(1, "fork");
 536         } else if (pid != 0) {
 537                 /*
 538                  * Parent: wait for child to finish, then clean up
 539                  * session.
 540                  */
 541                 int status;
 542                 setproctitle("-%s [pam]", getprogname());
 543                 waitpid(pid, &status, 0);
 544                 bail(NO_SLEEP_EXIT, 0);
 545         }
 546
 547         /*
 548          * NOTICE: We are now in the child process!
 549          */
 550
 551         /*
 552          * Add any environment variables the PAM modules may have set.
 553          */
 554         export_pam_environment();
 555
 556         /*
 557          * We're done with PAM now; our parent will deal with the rest.
 558          */
 559         pam_end(pamh, 0);
 560         pamh = NULL;
 561
 562         /*
 563          * We don't need to be root anymore, so set the login name and
 564          * the UID.
 565          */
 566         if (setlogin(username) != 0) {
 567                 syslog(LOG_ERR, "setlogin(%s): %m - exiting", username);
 568                 bail(NO_SLEEP_EXIT, 1);
 569         }
 570         if (setusercontext(lc, pwd, pwd->pw_uid,
 571             LOGIN_SETALL & ~(LOGIN_SETLOGIN|LOGIN_SETGROUP)) != 0) {
 572                 syslog(LOG_ERR, "setusercontext() failed - exiting");
 573                 exit(1);
 574         }
 575
 576         if (setenv("SHELL", pwd->pw_shell, 1) == -1)
 577                 err(1, "setenv: cannot set SHELL=%s", pwd->pw_shell);
 578         if (setenv("HOME", pwd->pw_dir, 1) == -1)
 579                 err(1, "setenv: cannot set HOME=%s", pwd->pw_dir);
 580         /* Overwrite "term" from login.conf(5) for any known TERM */
 581         if (term == NULL && (tp = stypeof(tty)) != NULL) {
 582                 if (setenv("TERM", tp, 1) == -1)
 583                         err(1, "setenv: cannot set TERM=%s", tp);
 584         } else {
 585                 if (setenv("TERM", TERM_UNKNOWN, 0) == -1)
 586                         err(1, "setenv: cannot set TERM=%s", TERM_UNKNOWN);
 587         }
 588
 589         if (setenv("LOGNAME", username, 1) == -1)
 590                 err(1, "setenv: cannot set LOGNAME=%s", username);
 591         if (setenv("USER", username, 1) == -1)
 592                 err(1, "setenv: cannot set USER=%s", username);
 593         if (setenv("PATH",
 594             rootlogin ? _PATH_STDPATH : _PATH_DEFPATH, 0) == -1) {
 595                 err(1, "setenv: cannot set PATH=%s",
 596                     rootlogin ? _PATH_STDPATH : _PATH_DEFPATH);
 597         }
 598
 599         if (!quietlog) {
 600                 const char *cw;
 601
 602                 cw = login_getcapstr(lc, "copyright", NULL, NULL);
 603                 if (cw == NULL || motd(cw) == -1)
 604                         printf("%s", copyright);
 605
 606                 printf("\n");
 607
 608                 cw = login_getcapstr(lc, "welcome", NULL, NULL);
 609                 if (cw != NULL && access(cw, F_OK) == 0)
 610                         motd(cw);
 611                 else
 612                         motd(_PATH_MOTDFILE);
 613
 614                 if (login_getcapbool(lc_user, "nocheckmail", 0) == 0 &&
 615                     login_getcapbool(lc, "nocheckmail", 0) == 0) {
 616                         char *cx;
 617
 618                         /* $MAIL may have been set by class. */
 619                         cx = getenv("MAIL");
 620                         if (cx == NULL) {
 621                                 asprintf(&cx, "%s/%s",
 622                                     _PATH_MAILDIR, pwd->pw_name);
 623                         }
 624                         if (cx && stat(cx, &st) == 0 && st.st_size != 0)
 625                                 printf("You have %smail.\n",
 626                                     (st.st_mtime > st.st_atime) ? "new " : "");
 627                         if (getenv("MAIL") == NULL)
 628                                 free(cx);
 629                 }
 630         }
 631
 632         login_close(lc_user);
 633         login_close(lc);
 634
 635         signal(SIGALRM, SIG_DFL);
 636         signal(SIGQUIT, SIG_DFL);
 637         signal(SIGINT, SIG_DFL);
 638         signal(SIGTSTP, SIG_IGN);
 639
 640         /*
 641          * Login shells have a leading '-' in front of argv[0]
 642          */
 643         p = strrchr(pwd->pw_shell, '/');
 644         if (asprintf(&arg0, "-%s", p ? p + 1 : pwd->pw_shell) >= MAXPATHLEN) {
 645                 syslog(LOG_ERR, "user: %s: shell exceeds maximum pathname size",
 646                     username);
 647                 errx(1, "shell exceeds maximum pathname size");
 648         } else if (arg0 == NULL) {
 649                 err(1, "asprintf()");
 650         }
 651
 652         execlp(shell, arg0, NULL);
 653         err(1, "%s", shell);
 654
 655         /*
 656          * That's it, folks!
 657          */
 658 }
 659
 660 /*
 661  * Attempt to authenticate the user using PAM.  Returns 0 if the user is
 662  * authenticated, or 1 if not authenticated.  If some sort of PAM system
 663  * error occurs (e.g., the "/etc/pam.conf" file is missing) then this
 664  * function returns -1.  This can be used as an indication that we should
 665  * fall back to a different authentication mechanism.
 666  */
 667 static int
 668 auth_pam(void)
 669 {
 670         const char *tmpl_user;
 671         const void *item;
 672         int rval;
 673
 674         pam_err = pam_authenticate(pamh, pam_silent);
 675         switch (pam_err) {
 676
 677         case PAM_SUCCESS:
 678                 /*
 679                  * With PAM we support the concept of a "template"
 680                  * user.  The user enters a login name which is
 681                  * authenticated by PAM, usually via a remote service
 682                  * such as RADIUS or TACACS+.  If authentication
 683                  * succeeds, a different but related "template" name
 684                  * is used for setting the credentials, shell, and
 685                  * home directory.  The name the user enters need only
 686                  * exist on the remote authentication server, but the
 687                  * template name must be present in the local password
 688                  * database.
 689                  *
 690                  * This is supported by two various mechanisms in the
 691                  * individual modules.  However, from the application's
 692                  * point of view, the template user is always passed
 693                  * back as a changed value of the PAM_USER item.
 694                  */
 695                 pam_err = pam_get_item(pamh, PAM_USER, &item);
 696                 if (pam_err == PAM_SUCCESS) {
 697                         tmpl_user = (const char *)item;
 698                         if (strcmp(username, tmpl_user) != 0)
 699                                 pwd = getpwnam(tmpl_user);
 700                 } else {
 701                         pam_syslog("pam_get_item(PAM_USER)");
 702                 }
 703                 rval = 0;
 704                 break;
 705
 706         case PAM_AUTH_ERR:
 707         case PAM_USER_UNKNOWN:
 708         case PAM_MAXTRIES:
 709                 rval = 1;
 710                 break;
 711
 712         default:
 713                 pam_syslog("pam_authenticate()");
 714                 rval = -1;
 715                 break;
 716         }
 717
 718         if (rval == 0) {
 719                 pam_err = pam_acct_mgmt(pamh, pam_silent);
 720                 switch (pam_err) {
 721                 case PAM_SUCCESS:
 722                         break;
 723                 case PAM_NEW_AUTHTOK_REQD:
 724                         pam_err = pam_chauthtok(pamh,
 725                             pam_silent|PAM_CHANGE_EXPIRED_AUTHTOK);
 726                         if (pam_err != PAM_SUCCESS) {
 727                                 pam_syslog("pam_chauthtok()");
 728                                 rval = 1;
 729                         }
 730                         break;
 731                 default:
 732                         pam_syslog("pam_acct_mgmt()");
 733                         rval = 1;
 734                         break;
 735                 }
 736         }
 737
 738         if (rval != 0) {
 739                 pam_end(pamh, pam_err);
 740                 pamh = NULL;
 741         }
 742         return (rval);
 743 }
 744
 745 /*
 746  * Export any environment variables PAM modules may have set
 747  */
 748 static void
 749 export_pam_environment(void)
 750 {
 751         char **pam_env;
 752         char **pp;
 753
 754         pam_env = pam_getenvlist(pamh);
 755         if (pam_env != NULL) {
 756                 for (pp = pam_env; *pp != NULL; pp++) {
 757                         export(*pp);
 758                         free(*pp);
 759                 }
 760         }
 761 }
 762
 763 /*
 764  * Perform sanity checks on an environment variable:
 765  * - Make sure there is an '=' in the string.
 766  * - Make sure the string doesn't run on too long.
 767  * - Do not export certain variables.  This list was taken from the
 768  *   Solaris pam_putenv(3) man page.
 769  * Then export it.
 770  */
 771 static int
 772 export(const char *s)
 773 {
 774         static const char *noexport[] = {
 775                 "SHELL", "HOME", "LOGNAME", "MAIL", "CDPATH",
 776                 "IFS", "PATH", NULL
 777         };
 778         char *p;
 779         const char **pp;
 780         size_t n;
 781
 782         if (strlen(s) > 1024 || (p = strchr(s, '=')) == NULL)
 783                 return (0);
 784         if (strncmp(s, "LD_", 3) == 0)
 785                 return (0);
 786         for (pp = noexport; *pp != NULL; pp++) {
 787                 n = strlen(*pp);
 788                 if (s[n] == '=' && strncmp(s, *pp, n) == 0)
 789                         return (0);
 790         }
 791         *p = '\0';
 792         if (setenv(s, p + 1, 1) == -1)
 793                 err(1, "setenv: cannot set %s=%s", s, p + 1);
 794         *p = '=';
 795         return (1);
 796 }
 797
 798 static void
 799 usage(void)
 800 {
 801
 802         fprintf(stderr, "usage: login [-fp] [-h hostname] [username]\n");
 803         exit(1);
 804 }
 805
 806 /*
 807  * Prompt user and read login name from stdin.
 808  */
 809 static char *
 810 getloginname(void)
 811 {
 812         char *nbuf, *p;
 813         int ch;
 814
 815         nbuf = malloc(MAXLOGNAME);
 816         if (nbuf == NULL)
 817                 err(1, "malloc()");
 818         do {
 819                 printf("%s", prompt);
 820                 for (p = nbuf; (ch = getchar()) != '\n'; ) {
 821                         if (ch == EOF) {
 822                                 badlogin(username);
 823                                 bail(NO_SLEEP_EXIT, 0);
 824                         }
 825                         if (p < nbuf + MAXLOGNAME - 1)
 826                                 *p++ = ch;
 827                 }
 828         } while (p == nbuf);
 829
 830         *p = '\0';
 831         if (nbuf[0] == '-') {
 832                 pam_silent = 0;
 833                 memmove(nbuf, nbuf + 1, strlen(nbuf));
 834         } else {
 835                 pam_silent = PAM_SILENT;
 836         }
 837         return nbuf;
 838 }
 839
 840 /*
 841  * SIGINT handler for motd().
 842  */
 843 static volatile int motdinterrupt;
 844 static void
 845 sigint(int signo __unused)
 846 {
 847         motdinterrupt = 1;
 848 }
 849
 850 /*
 851  * Display the contents of a file (such as /etc/motd).
 852  */
 853 static int
 854 motd(const char *motdfile)
 855 {
 856         sig_t oldint;
 857         FILE *f;
 858         int ch;
 859
 860         if ((f = fopen(motdfile, "r")) == NULL)
 861                 return (-1);
 862         motdinterrupt = 0;
 863         oldint = signal(SIGINT, sigint);
 864         while ((ch = fgetc(f)) != EOF && !motdinterrupt)
 865                 putchar(ch);
 866         signal(SIGINT, oldint);
 867         if (ch != EOF || ferror(f)) {
 868                 fclose(f);
 869                 return (-1);
 870         }
 871         fclose(f);
 872         return (0);
 873 }
 874
 875 /*
 876  * SIGALRM handler, to enforce login prompt timeout.
 877  *
 878  * XXX This can potentially confuse the hell out of PAM.  We should
 879  * XXX instead implement a conversation function that returns
 880  * XXX PAM_CONV_ERR when interrupted by a signal, and have the signal
 881  * XXX handler just set a flag.
 882  */
 883 static void
 884 timedout(int signo __unused)
 885 {
 886
 887         longjmp(timeout_buf, signo);
 888 }
 889
 890 static void
 891 badlogin(char *name)
 892 {
 893
 894         if (failures == 0)
 895                 return;
 896         if (hflag) {
 897                 syslog(LOG_NOTICE, "%d LOGIN FAILURE%s FROM %s",
 898                     failures, failures > 1 ? "S" : "", hostname);
 899                 syslog(LOG_AUTHPRIV|LOG_NOTICE,
 900                     "%d LOGIN FAILURE%s FROM %s, %s",
 901                     failures, failures > 1 ? "S" : "", hostname, name);
 902         } else {
 903                 syslog(LOG_NOTICE, "%d LOGIN FAILURE%s ON %s",
 904                     failures, failures > 1 ? "S" : "", tty);
 905                 syslog(LOG_AUTHPRIV|LOG_NOTICE,
 906                     "%d LOGIN FAILURE%s ON %s, %s",
 907                     failures, failures > 1 ? "S" : "", tty, name);
 908         }
 909         failures = 0;
 910 }
 911
 912 const char *
 913 stypeof(char *ttyid)
 914 {
 915         struct ttyent *t;
 916
 917         if (ttyid != NULL && *ttyid != '\0') {
 918                 t = getttynam(ttyid);
 919                 if (t != NULL && t->ty_type != NULL)
 920                         return (t->ty_type);
 921         }
 922         return (NULL);
 923 }
 924
 925 static void
 926 refused(const char *msg, const char *rtype, int lout)
 927 {
 928
 929         if (msg != NULL)
 930             printf("%s.\n", msg);
 931         if (hflag)
 932                 syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) FROM %s ON TTY %s",
 933                     pwd->pw_name, rtype, hostname, tty);
 934         else
 935                 syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) ON TTY %s",
 936                     pwd->pw_name, rtype, tty);
 937         if (lout)
 938                 bail(SLEEP_EXIT, 1);
 939 }
 940
 941 /*
 942  * Log a PAM error
 943  */
 944 static void
 945 pam_syslog(const char *msg)
 946 {
 947         syslog(LOG_ERR, "%s: %s", msg, pam_strerror(pamh, pam_err));
 948 }
 949
 950 /*
 951  * Shut down PAM
 952  */
 953 static void
 954 pam_cleanup(void)
 955 {
 956
 957         if (pamh != NULL) {
 958                 if (pam_session_established) {
 959                         pam_err = pam_close_session(pamh, 0);
 960                         if (pam_err != PAM_SUCCESS)
 961                                 pam_syslog("pam_close_session()");
 962                 }
 963                 pam_session_established = 0;
 964                 if (pam_cred_established) {
 965                         pam_err = pam_setcred(pamh, pam_silent|PAM_DELETE_CRED);
 966                         if (pam_err != PAM_SUCCESS)
 967                                 pam_syslog("pam_setcred()");
 968                 }
 969                 pam_cred_established = 0;
 970                 pam_end(pamh, pam_err);
 971                 pamh = NULL;
 972         }
 973 }
 974
 975 /*
 976  * Exit, optionally after sleeping a few seconds
 977  */
 978 void
 979 bail(int sec, int eval)
 980 {
 981
 982         pam_cleanup();
 983 #ifdef USE_BSM_AUDIT
 984         if (pwd != NULL)
 985                 audit_logout();
 986 #endif
 987         sleep(sec);
 988         exit(eval);
 989 }