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