source/libads/kerberos_verify.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    kerberos utility library
   4    Copyright (C) Andrew Tridgell 2001
   5    Copyright (C) Remus Koos 2001
   6    Copyright (C) Luke Howard 2003
   7    Copyright (C) Guenther Deschner 2003, 2005
   8    Copyright (C) Jim McDonough (jmcd@us.ibm.com) 2003
   9    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
  10    Copyright (C) Jeremy Allison 2007
  11
  12    This program is free software; you can redistribute it and/or modify
  13    it under the terms of the GNU General Public License as published by
  14    the Free Software Foundation; either version 3 of the License, or
  15    (at your option) any later version.
  16
  17    This program is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20    GNU General Public License for more details.
  21
  22    You should have received a copy of the GNU General Public License
  23    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  24 */
  25
  26 #include "includes.h"
  27
  28 #ifdef HAVE_KRB5
  29
  30 #if !defined(HAVE_KRB5_PRINC_COMPONENT)
  31 const krb5_data *krb5_princ_component(krb5_context, krb5_principal, int );
  32 #endif
  33
  34 /**********************************************************************************
  35  Try to verify a ticket using the system keytab... the system keytab has kvno -1 entries, so
  36  it's more like what microsoft does... see comment in utils/net_ads.c in the
  37  ads_keytab_add_entry function for details.
  38 ***********************************************************************************/
  39
  40 static bool ads_keytab_verify_ticket(krb5_context context,
  41                                         krb5_auth_context auth_context,
  42                                         const DATA_BLOB *ticket,
  43                                         krb5_ticket **pp_tkt,
  44                                         krb5_keyblock **keyblock,
  45                                         krb5_error_code *perr)
  46 {
  47         krb5_error_code ret = 0;
  48         bool auth_ok = False;
  49         krb5_keytab keytab = NULL;
  50         krb5_kt_cursor kt_cursor;
  51         krb5_keytab_entry kt_entry;
  52         char *valid_princ_formats[7] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL };
  53         char *entry_princ_s = NULL;
  54         fstring my_name, my_fqdn;
  55         int i;
  56         int number_matched_principals = 0;
  57         krb5_data packet;
  58
  59         *pp_tkt = NULL;
  60         *keyblock = NULL;
  61         *perr = 0;
  62
  63         /* Generate the list of principal names which we expect
  64          * clients might want to use for authenticating to the file
  65          * service.  We allow name$,{host,cifs}/{name,fqdn,name.REALM}. */
  66
  67         fstrcpy(my_name, global_myname());
  68
  69         my_fqdn[0] = '\0';
  70         name_to_fqdn(my_fqdn, global_myname());
  71
  72         if (asprintf(&valid_princ_formats[0], "%s$@%s", my_name, lp_realm()) == -1) {
  73                 goto out;
  74         }
  75         if (asprintf(&valid_princ_formats[1], "host/%s@%s", my_name, lp_realm()) == -1) {
  76                 goto out;
  77         }
  78         if (asprintf(&valid_princ_formats[2], "host/%s@%s", my_fqdn, lp_realm()) == -1) {
  79                 goto out;
  80         }
  81         if (asprintf(&valid_princ_formats[3], "host/%s.%s@%s", my_name, lp_realm(), lp_realm()) == -1) {
  82                 goto out;
  83         }
  84         if (asprintf(&valid_princ_formats[4], "cifs/%s@%s", my_name, lp_realm()) == -1) {
  85                 goto out;
  86         }
  87         if (asprintf(&valid_princ_formats[5], "cifs/%s@%s", my_fqdn, lp_realm()) == -1) {
  88                 goto out;
  89         }
  90         if (asprintf(&valid_princ_formats[6], "cifs/%s.%s@%s", my_name, lp_realm(), lp_realm()) == -1) {
  91                 goto out;
  92         }
  93
  94         ZERO_STRUCT(kt_entry);
  95         ZERO_STRUCT(kt_cursor);
  96
  97         ret = smb_krb5_open_keytab(context, NULL, False, &keytab);
  98         if (ret) {
  99                 DEBUG(1, ("ads_keytab_verify_ticket: smb_krb5_open_keytab failed (%s)\n", error_message(ret)));
 100                 goto out;
 101         }
 102
 103         /* Iterate through the keytab.  For each key, if the principal
 104          * name case-insensitively matches one of the allowed formats,
 105          * try verifying the ticket using that principal. */
 106
 107         ret = krb5_kt_start_seq_get(context, keytab, &kt_cursor);
 108         if (ret) {
 109                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_start_seq_get failed (%s)\n", error_message(ret)));
 110                 goto out;
 111         }
 112
 113         while (!auth_ok && (krb5_kt_next_entry(context, keytab, &kt_entry, &kt_cursor) == 0)) {
 114                 ret = smb_krb5_unparse_name(context, kt_entry.principal, &entry_princ_s);
 115                 if (ret) {
 116                         DEBUG(1, ("ads_keytab_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
 117                                 error_message(ret)));
 118                         goto out;
 119                 }
 120
 121                 for (i = 0; i < ARRAY_SIZE(valid_princ_formats); i++) {
 122
 123                         if (!strequal(entry_princ_s, valid_princ_formats[i])) {
 124                                 continue;
 125                         }
 126
 127                         number_matched_principals++;
 128                         packet.length = ticket->length;
 129                         packet.data = (char *)ticket->data;
 130                         *pp_tkt = NULL;
 131
 132                         ret = krb5_rd_req_return_keyblock_from_keytab(context, &auth_context, &packet,
 133                                                                       kt_entry.principal, keytab,
 134                                                                       NULL, pp_tkt, keyblock);
 135
 136                         if (ret) {
 137                                 DEBUG(10,("ads_keytab_verify_ticket: "
 138                                         "krb5_rd_req_return_keyblock_from_keytab(%s) failed: %s\n",
 139                                         entry_princ_s, error_message(ret)));
 140
 141                                 /* workaround for MIT:
 142                                 * as krb5_ktfile_get_entry will explicitly
 143                                 * close the krb5_keytab as soon as krb5_rd_req
 144                                 * has successfully decrypted the ticket but the
 145                                 * ticket is not valid yet (due to clockskew)
 146                                 * there is no point in querying more keytab
 147                                 * entries - Guenther */
 148
 149                                 if (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 150                                     ret == KRB5KRB_AP_ERR_TKT_EXPIRED ||
 151                                     ret == KRB5KRB_AP_ERR_SKEW) {
 152                                         break;
 153                                 }
 154                         } else {
 155                                 DEBUG(3,("ads_keytab_verify_ticket: "
 156                                         "krb5_rd_req_return_keyblock_from_keytab succeeded for principal %s\n",
 157                                         entry_princ_s));
 158                                 auth_ok = True;
 159                                 break;
 160                         }
 161                 }
 162
 163                 /* Free the name we parsed. */
 164                 SAFE_FREE(entry_princ_s);
 165
 166                 /* Free the entry we just read. */
 167                 smb_krb5_kt_free_entry(context, &kt_entry);
 168                 ZERO_STRUCT(kt_entry);
 169         }
 170         krb5_kt_end_seq_get(context, keytab, &kt_cursor);
 171
 172         ZERO_STRUCT(kt_cursor);
 173
 174   out:
 175
 176         for (i = 0; i < ARRAY_SIZE(valid_princ_formats); i++) {
 177                 SAFE_FREE(valid_princ_formats[i]);
 178         }
 179
 180         if (!auth_ok) {
 181                 if (!number_matched_principals) {
 182                         DEBUG(3, ("ads_keytab_verify_ticket: no keytab principals matched expected file service name.\n"));
 183                 } else {
 184                         DEBUG(3, ("ads_keytab_verify_ticket: krb5_rd_req failed for all %d matched keytab principals\n",
 185                                 number_matched_principals));
 186                 }
 187         }
 188
 189         SAFE_FREE(entry_princ_s);
 190
 191         {
 192                 krb5_keytab_entry zero_kt_entry;
 193                 ZERO_STRUCT(zero_kt_entry);
 194                 if (memcmp(&zero_kt_entry, &kt_entry, sizeof(krb5_keytab_entry))) {
 195                         smb_krb5_kt_free_entry(context, &kt_entry);
 196                 }
 197         }
 198
 199         {
 200                 krb5_kt_cursor zero_csr;
 201                 ZERO_STRUCT(zero_csr);
 202                 if ((memcmp(&kt_cursor, &zero_csr, sizeof(krb5_kt_cursor)) != 0) && keytab) {
 203                         krb5_kt_end_seq_get(context, keytab, &kt_cursor);
 204                 }
 205         }
 206
 207         if (keytab) {
 208                 krb5_kt_close(context, keytab);
 209         }
 210         *perr = ret;
 211         return auth_ok;
 212 }
 213
 214 /**********************************************************************************
 215  Try to verify a ticket using the secrets.tdb.
 216 ***********************************************************************************/
 217
 218 static krb5_error_code ads_secrets_verify_ticket(krb5_context context,
 219                                                 krb5_auth_context auth_context,
 220                                                 krb5_principal host_princ,
 221                                                 const DATA_BLOB *ticket,
 222                                                 krb5_ticket **pp_tkt,
 223                                                 krb5_keyblock **keyblock,
 224                                                 krb5_error_code *perr)
 225 {
 226         krb5_error_code ret = 0;
 227         bool auth_ok = False;
 228         char *password_s = NULL;
 229         krb5_data password;
 230         krb5_enctype enctypes[] = {
 231 #if defined(ENCTYPE_ARCFOUR_HMAC)
 232                 ENCTYPE_ARCFOUR_HMAC,
 233 #endif
 234                 ENCTYPE_DES_CBC_CRC,
 235                 ENCTYPE_DES_CBC_MD5,
 236                 ENCTYPE_NULL
 237         };
 238         krb5_data packet;
 239         int i;
 240
 241         *pp_tkt = NULL;
 242         *keyblock = NULL;
 243         *perr = 0;
 244
 245
 246         if (!secrets_init()) {
 247                 DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
 248                 *perr = KRB5_CONFIG_CANTOPEN;
 249                 return False;
 250         }
 251
 252         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 253         if (!password_s) {
 254                 DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
 255                 *perr = KRB5_LIBOS_CANTREADPWD;
 256                 return False;
 257         }
 258
 259         password.data = password_s;
 260         password.length = strlen(password_s);
 261
 262         /* CIFS doesn't use addresses in tickets. This would break NAT. JRA */
 263
 264         packet.length = ticket->length;
 265         packet.data = (char *)ticket->data;
 266
 267         /* We need to setup a auth context with each possible encoding type in turn. */
 268         for (i=0;enctypes[i];i++) {
 269                 krb5_keyblock *key = NULL;
 270
 271                 if (!(key = SMB_MALLOC_P(krb5_keyblock))) {
 272                         ret = ENOMEM;
 273                         goto out;
 274                 }
 275
 276                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i], false)) {
 277                         SAFE_FREE(key);
 278                         continue;
 279                 }
 280
 281                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 282
 283                 if (!(ret = krb5_rd_req(context, &auth_context, &packet,
 284                                         NULL,
 285                                         NULL, NULL, pp_tkt))) {
 286                         DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
 287                                 (unsigned int)enctypes[i] ));
 288                         auth_ok = True;
 289                         krb5_copy_keyblock(context, key, keyblock);
 290                         krb5_free_keyblock(context, key);
 291                         break;
 292                 }
 293
 294                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 295                                 ("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 296                                 (unsigned int)enctypes[i], error_message(ret)));
 297
 298                 /* successfully decrypted but ticket is just not valid at the moment */
 299                 if (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 300                     ret == KRB5KRB_AP_ERR_TKT_EXPIRED ||
 301                     ret == KRB5KRB_AP_ERR_SKEW) {
 302                         krb5_free_keyblock(context, key);
 303                         break;
 304                 }
 305
 306                 krb5_free_keyblock(context, key);
 307
 308         }
 309
 310  out:
 311         SAFE_FREE(password_s);
 312         *perr = ret;
 313         return auth_ok;
 314 }
 315
 316 /**********************************************************************************
 317  Verify an incoming ticket and parse out the principal name and
 318  authorization_data if available.
 319 ***********************************************************************************/
 320
 321 NTSTATUS ads_verify_ticket(TALLOC_CTX *mem_ctx,
 322                            const char *realm,
 323                            time_t time_offset,
 324                            const DATA_BLOB *ticket,
 325                            char **principal,
 326                            struct PAC_DATA **pac_data,
 327                            DATA_BLOB *ap_rep,
 328                            DATA_BLOB *session_key,
 329                            bool use_replay_cache)
 330 {
 331         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 332         NTSTATUS pac_ret;
 333         DATA_BLOB auth_data;
 334         krb5_context context = NULL;
 335         krb5_auth_context auth_context = NULL;
 336         krb5_data packet;
 337         krb5_ticket *tkt = NULL;
 338         krb5_rcache rcache = NULL;
 339         krb5_keyblock *keyblock = NULL;
 340         time_t authtime;
 341         krb5_error_code ret = 0;
 342         int flags = 0;
 343         krb5_principal host_princ = NULL;
 344         krb5_const_principal client_principal = NULL;
 345         char *host_princ_s = NULL;
 346         bool auth_ok = False;
 347         bool got_auth_data = False;
 348         struct named_mutex *mutex = NULL;
 349
 350         ZERO_STRUCT(packet);
 351         ZERO_STRUCT(auth_data);
 352
 353         *principal = NULL;
 354         *pac_data = NULL;
 355         *ap_rep = data_blob_null;
 356         *session_key = data_blob_null;
 357
 358         initialize_krb5_error_table();
 359         ret = krb5_init_context(&context);
 360         if (ret) {
 361                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 362                 return NT_STATUS_LOGON_FAILURE;
 363         }
 364
 365         if (time_offset != 0) {
 366                 krb5_set_real_time(context, time(NULL) + time_offset, 0);
 367         }
 368
 369         ret = krb5_set_default_realm(context, realm);
 370         if (ret) {
 371                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 372                 goto out;
 373         }
 374
 375         /* This whole process is far more complex than I would
 376            like. We have to go through all this to allow us to store
 377            the secret internally, instead of using /etc/krb5.keytab */
 378
 379         ret = krb5_auth_con_init(context, &auth_context);
 380         if (ret) {
 381                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 382                 goto out;
 383         }
 384
 385         krb5_auth_con_getflags( context, auth_context, &flags );
 386         if ( !use_replay_cache ) {
 387                 /* Disable default use of a replay cache */
 388                 flags &= ~KRB5_AUTH_CONTEXT_DO_TIME;
 389                 krb5_auth_con_setflags( context, auth_context, flags );
 390         }
 391
 392         if (asprintf(&host_princ_s, "%s$", global_myname()) == -1) {
 393                 goto out;
 394         }
 395
 396         strlower_m(host_princ_s);
 397         ret = smb_krb5_parse_name(context, host_princ_s, &host_princ);
 398         if (ret) {
 399                 DEBUG(1,("ads_verify_ticket: smb_krb5_parse_name(%s) failed (%s)\n",
 400                                         host_princ_s, error_message(ret)));
 401                 goto out;
 402         }
 403
 404
 405         if ( use_replay_cache ) {
 406
 407                 /* Lock a mutex surrounding the replay as there is no
 408                    locking in the MIT krb5 code surrounding the replay
 409                    cache... */
 410
 411                 mutex = grab_named_mutex(talloc_tos(), "replay cache mutex",
 412                                          10);
 413                 if (mutex == NULL) {
 414                         DEBUG(1,("ads_verify_ticket: unable to protect "
 415                                  "replay cache with mutex.\n"));
 416                         ret = KRB5_CC_IO;
 417                         goto out;
 418                 }
 419
 420                 /* JRA. We must set the rcache here. This will prevent
 421                    replay attacks. */
 422
 423                 ret = krb5_get_server_rcache(context,
 424                                              krb5_princ_component(context, host_princ, 0),
 425                                              &rcache);
 426                 if (ret) {
 427                         DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache "
 428                                  "failed (%s)\n", error_message(ret)));
 429                         goto out;
 430                 }
 431
 432                 ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 433                 if (ret) {
 434                         DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache "
 435                                  "failed (%s)\n", error_message(ret)));
 436                         goto out;
 437                 }
 438         }
 439
 440         /* Try secrets.tdb first and fallback to the krb5.keytab if
 441            necessary */
 442
 443         auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
 444                                             ticket, &tkt, &keyblock, &ret);
 445
 446         if (!auth_ok &&
 447             (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 448              ret == KRB5KRB_AP_ERR_TKT_EXPIRED ||
 449              ret == KRB5KRB_AP_ERR_SKEW)) {
 450                 goto auth_failed;
 451         }
 452
 453         if (!auth_ok && lp_use_kerberos_keytab()) {
 454                 auth_ok = ads_keytab_verify_ticket(context, auth_context,
 455                                                    ticket, &tkt, &keyblock, &ret);
 456         }
 457
 458         if ( use_replay_cache ) {
 459                 TALLOC_FREE(mutex);
 460 #if 0
 461                 /* Heimdal leaks here, if we fix the leak, MIT crashes */
 462                 if (rcache) {
 463                         krb5_rc_close(context, rcache);
 464                 }
 465 #endif
 466         }
 467
 468  auth_failed:
 469         if (!auth_ok) {
 470                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 471                          error_message(ret)));
 472                 /* Try map the error return in case it's something like
 473                  * a clock skew error.
 474                  */
 475                 sret = krb5_to_nt_status(ret);
 476                 if (NT_STATUS_IS_OK(sret) || NT_STATUS_EQUAL(sret,NT_STATUS_UNSUCCESSFUL)) {
 477                         sret = NT_STATUS_LOGON_FAILURE;
 478                 }
 479                 DEBUG(10,("ads_verify_ticket: returning error %s\n",
 480                         nt_errstr(sret) ));
 481                 goto out;
 482         }
 483
 484         authtime = get_authtime_from_tkt(tkt);
 485         client_principal = get_principal_from_tkt(tkt);
 486
 487         ret = krb5_mk_rep(context, auth_context, &packet);
 488         if (ret) {
 489                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 490                         error_message(ret)));
 491                 goto out;
 492         }
 493
 494         *ap_rep = data_blob(packet.data, packet.length);
 495         if (packet.data) {
 496                 kerberos_free_data_contents(context, &packet);
 497                 ZERO_STRUCT(packet);
 498         }
 499
 500         get_krb5_smb_session_key(context, auth_context, session_key, True);
 501         dump_data_pw("SMB session key (from ticket)\n", session_key->data, session_key->length);
 502
 503 #if 0
 504         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 505 #endif
 506
 507         /* continue when no PAC is retrieved or we couldn't decode the PAC
 508            (like accounts that have the UF_NO_AUTH_DATA_REQUIRED flag set, or
 509            Kerberos tickets encrypted using a DES key) - Guenther */
 510
 511         got_auth_data = get_auth_data_from_tkt(mem_ctx, &auth_data, tkt);
 512         if (!got_auth_data) {
 513                 DEBUG(3,("ads_verify_ticket: did not retrieve auth data. continuing without PAC\n"));
 514         }
 515
 516         if (got_auth_data) {
 517                 pac_ret = decode_pac_data(mem_ctx, &auth_data, context, keyblock, client_principal, authtime, pac_data);
 518                 if (!NT_STATUS_IS_OK(pac_ret)) {
 519                         DEBUG(3,("ads_verify_ticket: failed to decode PAC_DATA: %s\n", nt_errstr(pac_ret)));
 520                         *pac_data = NULL;
 521                 }
 522                 data_blob_free(&auth_data);
 523         }
 524
 525 #if 0
 526 #if defined(HAVE_KRB5_TKT_ENC_PART2)
 527         /* MIT */
 528         if (tkt->enc_part2) {
 529                 file_save("/tmp/authdata.dat",
 530                           tkt->enc_part2->authorization_data[0]->contents,
 531                           tkt->enc_part2->authorization_data[0]->length);
 532         }
 533 #else
 534         /* Heimdal */
 535         if (tkt->ticket.authorization_data) {
 536                 file_save("/tmp/authdata.dat",
 537                           tkt->ticket.authorization_data->val->ad_data.data,
 538                           tkt->ticket.authorization_data->val->ad_data.length);
 539         }
 540 #endif
 541 #endif
 542
 543         if ((ret = smb_krb5_unparse_name(context, client_principal, principal))) {
 544                 DEBUG(3,("ads_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
 545                          error_message(ret)));
 546                 sret = NT_STATUS_LOGON_FAILURE;
 547                 goto out;
 548         }
 549
 550         sret = NT_STATUS_OK;
 551
 552  out:
 553
 554         TALLOC_FREE(mutex);
 555
 556         if (!NT_STATUS_IS_OK(sret)) {
 557                 data_blob_free(&auth_data);
 558         }
 559
 560         if (!NT_STATUS_IS_OK(sret)) {
 561                 data_blob_free(ap_rep);
 562         }
 563
 564         if (host_princ) {
 565                 krb5_free_principal(context, host_princ);
 566         }
 567
 568         if (keyblock) {
 569                 krb5_free_keyblock(context, keyblock);
 570         }
 571
 572         if (tkt != NULL) {
 573                 krb5_free_ticket(context, tkt);
 574         }
 575
 576         SAFE_FREE(host_princ_s);
 577
 578         if (auth_context) {
 579                 krb5_auth_con_free(context, auth_context);
 580         }
 581
 582         if (context) {
 583                 krb5_free_context(context);
 584         }
 585
 586         return sret;
 587 }
 588
 589 #endif /* HAVE_KRB5 */