crypto/external/bsd/openssh/dist/auth.c

   1 /*      $NetBSD$        */
   2 /* $OpenBSD: auth.c,v 1.80 2008/11/04 07:58:09 djm Exp $ */
   3 /*
   4  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28 __RCSID("$NetBSD: auth.c,v 1.28 2009/02/16 20:53:54 christos Exp $");
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <sys/param.h>
  32
  33 #include <errno.h>
  34 #include <fcntl.h>
  35 #include <libgen.h>
  36 #include <login_cap.h>
  37 #include <paths.h>
  38 #include <pwd.h>
  39 #include <stdarg.h>
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43
  44 #include "xmalloc.h"
  45 #include "match.h"
  46 #include "groupaccess.h"
  47 #include "log.h"
  48 #include "buffer.h"
  49 #include "servconf.h"
  50 #include "key.h"
  51 #include "hostfile.h"
  52 #include "auth.h"
  53 #include "auth-options.h"
  54 #include "canohost.h"
  55 #include "uidswap.h"
  56 #include "misc.h"
  57 #include "packet.h"
  58 #ifdef GSSAPI
  59 #include "ssh-gss.h"
  60 #endif
  61 #include "monitor_wrap.h"
  62
  63 #ifdef HAVE_LOGIN_CAP
  64 #include <login_cap.h>
  65 #endif
  66
  67 /* import */
  68 extern ServerOptions options;
  69 extern int use_privsep;
  70
  71 /* Debugging messages */
  72 Buffer auth_debug;
  73 int auth_debug_init;
  74
  75 /*
  76  * Check if the user is allowed to log in via ssh. If user is listed
  77  * in DenyUsers or one of user's groups is listed in DenyGroups, false
  78  * will be returned. If AllowUsers isn't empty and user isn't listed
  79  * there, or if AllowGroups isn't empty and one of user's groups isn't
  80  * listed there, false will be returned.
  81  * If the user's shell is not executable, false will be returned.
  82  * Otherwise true is returned.
  83  */
  84 int
  85 allowed_user(struct passwd * pw)
  86 {
  87 #ifdef HAVE_LOGIN_CAP
  88         extern login_cap_t *lc;
  89         int match_name, match_ip;
  90         char *cap_hlist, *hp;
  91 #endif
  92         struct stat st;
  93         const char *hostname = NULL, *ipaddr = NULL;
  94         char *shell;
  95         u_int i;
  96
  97         /* Shouldn't be called if pw is NULL, but better safe than sorry... */
  98         if (!pw || !pw->pw_name)
  99                 return 0;
 100
 101 #ifdef HAVE_LOGIN_CAP
 102         hostname = get_canonical_hostname(1);
 103         ipaddr = get_remote_ipaddr();
 104
 105         lc = login_getclass(pw->pw_class);
 106
 107         /*
 108          * Check the deny list.
 109          */
 110         cap_hlist = login_getcapstr(lc, "host.deny", NULL, NULL);
 111         if (cap_hlist != NULL) {
 112                 hp = strtok(cap_hlist, ",");
 113                 while (hp != NULL) {
 114                         match_name = match_hostname(hostname,
 115                             hp, strlen(hp));
 116                         match_ip = match_hostname(ipaddr,
 117                             hp, strlen(hp));
 118                         /*
 119                          * Only a positive match here causes a "deny".
 120                          */
 121                         if (match_name > 0 || match_ip > 0) {
 122                                 free(cap_hlist);
 123                                 login_close(lc);
 124                                 return 0;
 125                         }
 126                         hp = strtok(NULL, ",");
 127                 }
 128                 free(cap_hlist);
 129         }
 130
 131         /*
 132          * Check the allow list.  If the allow list exists, and the
 133          * remote host is not in it, the user is implicitly denied.
 134          */
 135         cap_hlist = login_getcapstr(lc, "host.allow", NULL, NULL);
 136         if (cap_hlist != NULL) {
 137                 hp = strtok(cap_hlist, ",");
 138                 if (hp == NULL) {
 139                         /* Just in case there's an empty string... */
 140                         free(cap_hlist);
 141                         login_close(lc);
 142                         return 0;
 143                 }
 144                 while (hp != NULL) {
 145                         match_name = match_hostname(hostname,
 146                             hp, strlen(hp));
 147                         match_ip = match_hostname(ipaddr,
 148                             hp, strlen(hp));
 149                         /*
 150                          * Negative match causes an immediate "deny".
 151                          * Positive match causes us to break out
 152                          * of the loop (allowing a fallthrough).
 153                          */
 154                         if (match_name < 0 || match_ip < 0) {
 155                                 free(cap_hlist);
 156                                 login_close(lc);
 157                                 return 0;
 158                         }
 159                         if (match_name > 0 || match_ip > 0)
 160                                 break;
 161                         hp = strtok(NULL, ",");
 162                 }
 163                 free(cap_hlist);
 164                 if (hp == NULL) {
 165                         login_close(lc);
 166                         return 0;
 167                 }
 168         }
 169
 170         login_close(lc);
 171 #endif
 172
 173 #ifdef USE_PAM
 174         if (!options.use_pam) {
 175 #endif
 176         /*
 177          * password/account expiration.
 178          */
 179         if (pw->pw_change || pw->pw_expire) {
 180                 struct timeval tv;
 181
 182                 (void)gettimeofday(&tv, (struct timezone *)NULL);
 183                 if (pw->pw_expire) {
 184                         if (tv.tv_sec >= pw->pw_expire) {
 185                                 logit("User %.100s not allowed because account has expired",
 186                                     pw->pw_name);
 187                                 return 0;       /* expired */
 188                         }
 189                 }
 190 #ifdef _PASSWORD_CHGNOW
 191                 if (pw->pw_change == _PASSWORD_CHGNOW) {
 192                         logit("User %.100s not allowed because password needs to be changed",
 193                             pw->pw_name);
 194
 195                         return 0;       /* can't force password change (yet) */
 196                 }
 197 #endif
 198                 if (pw->pw_change) {
 199                         if (tv.tv_sec >= pw->pw_change) {
 200                                 logit("User %.100s not allowed because password has expired",
 201                                     pw->pw_name);
 202                                 return 0;       /* expired */
 203                         }
 204                 }
 205         }
 206 #ifdef USE_PAM
 207         }
 208 #endif
 209
 210         /*
 211          * Get the shell from the password data.  An empty shell field is
 212          * legal, and means /bin/sh.
 213          */
 214         shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
 215
 216         /* deny if shell does not exists or is not executable */
 217         /*
 218          * XXX Should check to see if it is executable by the
 219          * XXX requesting user.  --thorpej
 220          */
 221         if (stat(shell, &st) != 0) {
 222                 logit("User %.100s not allowed because shell %.100s does not exist",
 223                     pw->pw_name, shell);
 224                 return 0;
 225         }
 226         if (S_ISREG(st.st_mode) == 0 ||
 227             (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
 228                 logit("User %.100s not allowed because shell %.100s is not executable",
 229                     pw->pw_name, shell);
 230                 return 0;
 231         }
 232         /*
 233          * XXX Consider nuking {Allow,Deny}{Users,Groups}.  We have the
 234          * XXX login_cap(3) mechanism which covers all other types of
 235          * XXX logins, too.
 236          */
 237
 238         if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
 239             options.num_deny_groups > 0 || options.num_allow_groups > 0) {
 240                 hostname = get_canonical_hostname(options.use_dns);
 241                 ipaddr = get_remote_ipaddr();
 242         }
 243
 244         /* Return false if user is listed in DenyUsers */
 245         if (options.num_deny_users > 0) {
 246                 for (i = 0; i < options.num_deny_users; i++)
 247                         if (match_user(pw->pw_name, hostname, ipaddr,
 248                             options.deny_users[i])) {
 249                                 logit("User %.100s from %.100s not allowed "
 250                                     "because listed in DenyUsers",
 251                                     pw->pw_name, hostname);
 252                                 return 0;
 253                         }
 254         }
 255         /* Return false if AllowUsers isn't empty and user isn't listed there */
 256         if (options.num_allow_users > 0) {
 257                 for (i = 0; i < options.num_allow_users; i++)
 258                         if (match_user(pw->pw_name, hostname, ipaddr,
 259                             options.allow_users[i]))
 260                                 break;
 261                 /* i < options.num_allow_users iff we break for loop */
 262                 if (i >= options.num_allow_users) {
 263                         logit("User %.100s from %.100s not allowed because "
 264                             "not listed in AllowUsers", pw->pw_name, hostname);
 265                         return 0;
 266                 }
 267         }
 268         if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
 269                 /* Get the user's group access list (primary and supplementary) */
 270                 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
 271                         logit("User %.100s from %.100s not allowed because "
 272                             "not in any group", pw->pw_name, hostname);
 273                         return 0;
 274                 }
 275
 276                 /* Return false if one of user's groups is listed in DenyGroups */
 277                 if (options.num_deny_groups > 0)
 278                         if (ga_match(options.deny_groups,
 279                             options.num_deny_groups)) {
 280                                 ga_free();
 281                                 logit("User %.100s from %.100s not allowed "
 282                                     "because a group is listed in DenyGroups",
 283                                     pw->pw_name, hostname);
 284                                 return 0;
 285                         }
 286                 /*
 287                  * Return false if AllowGroups isn't empty and one of user's groups
 288                  * isn't listed there
 289                  */
 290                 if (options.num_allow_groups > 0)
 291                         if (!ga_match(options.allow_groups,
 292                             options.num_allow_groups)) {
 293                                 ga_free();
 294                                 logit("User %.100s from %.100s not allowed "
 295                                     "because none of user's groups are listed "
 296                                     "in AllowGroups", pw->pw_name, hostname);
 297                                 return 0;
 298                         }
 299                 ga_free();
 300         }
 301         /* We found no reason not to let this user try to log on... */
 302         return 1;
 303 }
 304
 305 void
 306 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
 307 {
 308         void (*authlog) (const char *fmt,...) = verbose;
 309         char *authmsg;
 310
 311         if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
 312                 return;
 313
 314         /* Raise logging level */
 315         if (authenticated == 1 ||
 316             !authctxt->valid ||
 317             authctxt->failures >= options.max_authtries / 2 ||
 318             strcmp(method, "password") == 0)
 319                 authlog = logit;
 320
 321         if (authctxt->postponed)
 322                 authmsg = "Postponed";
 323         else
 324                 authmsg = authenticated ? "Accepted" : "Failed";
 325
 326         authlog("%s %s for %s%.100s from %.200s port %d%s",
 327             authmsg,
 328             method,
 329             authctxt->valid ? "" : "invalid user ",
 330             authctxt->user,
 331             get_remote_ipaddr(),
 332             get_remote_port(),
 333             info);
 334 }
 335
 336 /*
 337  * Check whether root logins are disallowed.
 338  */
 339 int
 340 auth_root_allowed(char *method)
 341 {
 342         switch (options.permit_root_login) {
 343         case PERMIT_YES:
 344                 return 1;
 345         case PERMIT_NO_PASSWD:
 346                 if (strcmp(method, "password") != 0)
 347                         return 1;
 348                 break;
 349         case PERMIT_FORCED_ONLY:
 350                 if (forced_command) {
 351                         logit("Root login accepted for forced command.");
 352                         return 1;
 353                 }
 354                 break;
 355         }
 356         logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
 357         return 0;
 358 }
 359
 360
 361 /*
 362  * Given a template and a passwd structure, build a filename
 363  * by substituting % tokenised options. Currently, %% becomes '%',
 364  * %h becomes the home directory and %u the username.
 365  *
 366  * This returns a buffer allocated by xmalloc.
 367  */
 368 static char *
 369 expand_authorized_keys(const char *filename, struct passwd *pw)
 370 {
 371         char *file, ret[MAXPATHLEN];
 372         int i;
 373
 374         file = percent_expand(filename, "h", pw->pw_dir,
 375             "u", pw->pw_name, (char *)NULL);
 376
 377         /*
 378          * Ensure that filename starts anchored. If not, be backward
 379          * compatible and prepend the '%h/'
 380          */
 381         if (*file == '/')
 382                 return (file);
 383
 384         i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
 385         if (i < 0 || (size_t)i >= sizeof(ret))
 386                 fatal("expand_authorized_keys: path too long");
 387         xfree(file);
 388         return (xstrdup(ret));
 389 }
 390
 391 char *
 392 authorized_keys_file(struct passwd *pw)
 393 {
 394         return expand_authorized_keys(options.authorized_keys_file, pw);
 395 }
 396
 397 char *
 398 authorized_keys_file2(struct passwd *pw)
 399 {
 400         return expand_authorized_keys(options.authorized_keys_file2, pw);
 401 }
 402
 403 /* return ok if key exists in sysfile or userfile */
 404 HostStatus
 405 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
 406     const char *sysfile, const char *userfile)
 407 {
 408         Key *found;
 409         char *user_hostfile;
 410         struct stat st;
 411         HostStatus host_status;
 412
 413         /* Check if we know the host and its host key. */
 414         found = key_new(key->type);
 415         host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
 416
 417         if (host_status != HOST_OK && userfile != NULL) {
 418                 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
 419                 if (options.strict_modes &&
 420                     (stat(user_hostfile, &st) == 0) &&
 421                     ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
 422                     (st.st_mode & 022) != 0)) {
 423                         logit("Authentication refused for %.100s: "
 424                             "bad owner or modes for %.200s",
 425                             pw->pw_name, user_hostfile);
 426                 } else {
 427                         temporarily_use_uid(pw);
 428                         host_status = check_host_in_hostfile(user_hostfile,
 429                             host, key, found, NULL);
 430                         restore_uid();
 431                 }
 432                 xfree(user_hostfile);
 433         }
 434         key_free(found);
 435
 436         debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
 437             "ok" : "not found", host);
 438         return host_status;
 439 }
 440
 441
 442 /*
 443  * Check a given file for security. This is defined as all components
 444  * of the path to the file must be owned by either the owner of
 445  * of the file or root and no directories must be group or world writable.
 446  *
 447  * XXX Should any specific check be done for sym links ?
 448  *
 449  * Takes an open file descriptor, the file name, a uid and and
 450  * error buffer plus max size as arguments.
 451  *
 452  * Returns 0 on success and -1 on failure
 453  */
 454 static int
 455 secure_filename(FILE *f, const char *file, struct passwd *pw,
 456     char *err, size_t errlen)
 457 {
 458         uid_t uid = pw->pw_uid;
 459         char buf[MAXPATHLEN], homedir[MAXPATHLEN];
 460         char *cp;
 461         int comparehome = 0;
 462         struct stat st;
 463
 464         if (realpath(file, buf) == NULL) {
 465                 snprintf(err, errlen, "realpath %s failed: %s", file,
 466                     strerror(errno));
 467                 return -1;
 468         }
 469         if (realpath(pw->pw_dir, homedir) != NULL)
 470                 comparehome = 1;
 471
 472         /* check the open file to avoid races */
 473         if (fstat(fileno(f), &st) < 0 ||
 474             (st.st_uid != 0 && st.st_uid != uid) ||
 475             (st.st_mode & 022) != 0) {
 476                 snprintf(err, errlen, "bad ownership or modes for file %s",
 477                     buf);
 478                 return -1;
 479         }
 480
 481         /* for each component of the canonical path, walking upwards */
 482         for (;;) {
 483                 if ((cp = dirname(buf)) == NULL) {
 484                         snprintf(err, errlen, "dirname() failed");
 485                         return -1;
 486                 }
 487                 strlcpy(buf, cp, sizeof(buf));
 488
 489                 debug3("secure_filename: checking '%s'", buf);
 490                 if (stat(buf, &st) < 0 ||
 491                     (st.st_uid != 0 && st.st_uid != uid) ||
 492                     (st.st_mode & 022) != 0) {
 493                         snprintf(err, errlen,
 494                             "bad ownership or modes for directory %s", buf);
 495                         return -1;
 496                 }
 497
 498                 /* If are passed the homedir then we can stop */
 499                 if (comparehome && strcmp(homedir, buf) == 0) {
 500                         debug3("secure_filename: terminating check at '%s'",
 501                             buf);
 502                         break;
 503                 }
 504                 /*
 505                  * dirname should always complete with a "/" path,
 506                  * but we can be paranoid and check for "." too
 507                  */
 508                 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
 509                         break;
 510         }
 511         return 0;
 512 }
 513
 514 FILE *
 515 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
 516 {
 517         char line[1024];
 518         struct stat st;
 519         int fd;
 520         FILE *f;
 521
 522         /*
 523          * Open the file containing the authorized keys
 524          * Fail quietly if file does not exist
 525          */
 526         if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1)
 527                 return NULL;
 528
 529         if (fstat(fd, &st) < 0) {
 530                 close(fd);
 531                 return NULL;
 532         }
 533         if (!S_ISREG(st.st_mode)) {
 534                 logit("User %s authorized keys %s is not a regular file",
 535                     pw->pw_name, file);
 536                 close(fd);
 537                 return NULL;
 538         }
 539         unset_nonblock(fd);
 540         if ((f = fdopen(fd, "r")) == NULL) {
 541                 close(fd);
 542                 return NULL;
 543         }
 544         if (options.strict_modes &&
 545             secure_filename(f, file, pw, line, sizeof(line)) != 0) {
 546                 fclose(f);
 547                 logit("Authentication refused: %s", line);
 548                 return NULL;
 549         }
 550
 551         return f;
 552 }
 553
 554 struct passwd *
 555 getpwnamallow(const char *user)
 556 {
 557 #ifdef HAVE_LOGIN_CAP
 558         extern login_cap_t *lc;
 559 #ifdef BSD_AUTH
 560         auth_session_t *as;
 561 #endif
 562 #endif
 563         struct passwd *pw;
 564
 565         parse_server_match_config(&options, user,
 566             get_canonical_hostname(options.use_dns), get_remote_ipaddr());
 567
 568         pw = getpwnam(user);
 569         if (pw == NULL) {
 570                 logit("Invalid user %.100s from %.100s",
 571                     user, get_remote_ipaddr());
 572                 return (NULL);
 573         }
 574         if (!allowed_user(pw))
 575                 return (NULL);
 576 #ifdef HAVE_LOGIN_CAP
 577         if ((lc = login_getclass(pw->pw_class)) == NULL) {
 578                 debug("unable to get login class: %s", user);
 579                 return (NULL);
 580         }
 581 #ifdef BSD_AUTH
 582         if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
 583             auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
 584                 debug("Approval failure for %s", user);
 585                 pw = NULL;
 586         }
 587         if (as != NULL)
 588                 auth_close(as);
 589 #endif
 590 #endif
 591         if (pw != NULL)
 592                 return (pwcopy(pw));
 593         return (NULL);
 594 }
 595
 596 void
 597 auth_debug_add(const char *fmt,...)
 598 {
 599         char buf[1024];
 600         va_list args;
 601
 602         if (!auth_debug_init)
 603                 return;
 604
 605         va_start(args, fmt);
 606         vsnprintf(buf, sizeof(buf), fmt, args);
 607         va_end(args);
 608         buffer_put_cstring(&auth_debug, buf);
 609 }
 610
 611 void
 612 auth_debug_send(void)
 613 {
 614         char *msg;
 615
 616         if (!auth_debug_init)
 617                 return;
 618         while (buffer_len(&auth_debug)) {
 619                 msg = buffer_get_string(&auth_debug, NULL);
 620                 packet_send_debug("%s", msg);
 621                 xfree(msg);
 622         }
 623 }
 624
 625 void
 626 auth_debug_reset(void)
 627 {
 628         if (auth_debug_init)
 629                 buffer_clear(&auth_debug);
 630         else {
 631                 buffer_init(&auth_debug);
 632                 auth_debug_init = 1;
 633         }
 634 }
 635
 636 struct passwd *
 637 fakepw(void)
 638 {
 639         static struct passwd fake;
 640
 641         memset(&fake, 0, sizeof(fake));
 642         fake.pw_name = "NOUSER";
 643         fake.pw_passwd =
 644             "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
 645         fake.pw_gecos = "NOUSER";
 646         fake.pw_uid = (uid_t)-1;
 647         fake.pw_gid = (gid_t)-1;
 648         fake.pw_class = "";
 649         fake.pw_dir = "/nonexist";
 650         fake.pw_shell = "/nonexist";
 651
 652         return (&fake);
 653 }