source3/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
  11    This program is free software; you can redistribute it and/or modify
  12    it under the terms of the GNU General Public License as published by
  13    the Free Software Foundation; either version 2 of the License, or
  14    (at your option) any later version.
  15
  16    This program is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19    GNU General Public License for more details.
  20
  21    You should have received a copy of the GNU General Public License
  22    along with this program; if not, write to the Free Software
  23    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  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, krb5_auth_context auth_context,
  41                         const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt,
  42                         krb5_keyblock **keyblock)
  43 {
  44         krb5_error_code ret = 0;
  45         BOOL auth_ok = False;
  46         krb5_keytab keytab = NULL;
  47         krb5_kt_cursor kt_cursor;
  48         krb5_keytab_entry kt_entry;
  49         char *valid_princ_formats[7] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL };
  50         char *entry_princ_s = NULL;
  51         fstring my_name, my_fqdn;
  52         int i;
  53         int number_matched_principals = 0;
  54
  55         /* Generate the list of principal names which we expect
  56          * clients might want to use for authenticating to the file
  57          * service.  We allow name$,{host,cifs}/{name,fqdn,name.REALM}. */
  58
  59         fstrcpy(my_name, global_myname());
  60
  61         my_fqdn[0] = '\0';
  62         name_to_fqdn(my_fqdn, global_myname());
  63
  64         asprintf(&valid_princ_formats[0], "%s$@%s", my_name, lp_realm());
  65         asprintf(&valid_princ_formats[1], "host/%s@%s", my_name, lp_realm());
  66         asprintf(&valid_princ_formats[2], "host/%s@%s", my_fqdn, lp_realm());
  67         asprintf(&valid_princ_formats[3], "host/%s.%s@%s", my_name, lp_realm(), lp_realm());
  68         asprintf(&valid_princ_formats[4], "cifs/%s@%s", my_name, lp_realm());
  69         asprintf(&valid_princ_formats[5], "cifs/%s@%s", my_fqdn, lp_realm());
  70         asprintf(&valid_princ_formats[6], "cifs/%s.%s@%s", my_name, lp_realm(), lp_realm());
  71
  72         ZERO_STRUCT(kt_entry);
  73         ZERO_STRUCT(kt_cursor);
  74
  75         ret = krb5_kt_default(context, &keytab);
  76         if (ret) {
  77                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_default failed (%s)\n", error_message(ret)));
  78                 goto out;
  79         }
  80
  81         /* Iterate through the keytab.  For each key, if the principal
  82          * name case-insensitively matches one of the allowed formats,
  83          * try verifying the ticket using that principal. */
  84
  85         ret = krb5_kt_start_seq_get(context, keytab, &kt_cursor);
  86         if (ret) {
  87                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_start_seq_get failed (%s)\n", error_message(ret)));
  88                 goto out;
  89         }
  90
  91         if (ret != KRB5_KT_END && ret != ENOENT ) {
  92                 while (!auth_ok && (krb5_kt_next_entry(context, keytab, &kt_entry, &kt_cursor) == 0)) {
  93                         ret = smb_krb5_unparse_name(context, kt_entry.principal, &entry_princ_s);
  94                         if (ret) {
  95                                 DEBUG(1, ("ads_keytab_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
  96                                         error_message(ret)));
  97                                 goto out;
  98                         }
  99
 100                         for (i = 0; i < sizeof(valid_princ_formats) / sizeof(valid_princ_formats[0]); i++) {
 101                                 if (strequal(entry_princ_s, valid_princ_formats[i])) {
 102                                         number_matched_principals++;
 103                                         p_packet->length = ticket->length;
 104                                         p_packet->data = (krb5_pointer)ticket->data;
 105                                         *pp_tkt = NULL;
 106
 107                                         ret = krb5_rd_req_return_keyblock_from_keytab(context, &auth_context, p_packet,
 108                                                                                       kt_entry.principal, keytab,
 109                                                                                       NULL, pp_tkt, keyblock);
 110
 111                                         if (ret) {
 112                                                 DEBUG(10,("ads_keytab_verify_ticket: "
 113                                                         "krb5_rd_req_return_keyblock_from_keytab(%s) failed: %s\n",
 114                                                         entry_princ_s, error_message(ret)));
 115
 116                                                 /* workaround for MIT:
 117                                                  * as krb5_ktfile_get_entry will
 118                                                  * explicitly close the
 119                                                  * krb5_keytab as soon as
 120                                                  * krb5_rd_req has sucessfully
 121                                                  * decrypted the ticket but the
 122                                                  * ticket is not valid yet (due
 123                                                  * to clockskew) there is no
 124                                                  * point in querying more
 125                                                  * keytab entries - Guenther */
 126
 127                                                 if (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 128                                                     ret == KRB5KRB_AP_ERR_TKT_EXPIRED) {
 129                                                         break;
 130                                                 }
 131                                         } else {
 132                                                 DEBUG(3,("ads_keytab_verify_ticket: "
 133                                                         "krb5_rd_req_return_keyblock_from_keytab succeeded for principal %s\n",
 134                                                         entry_princ_s));
 135                                                 auth_ok = True;
 136                                                 break;
 137                                         }
 138                                 }
 139                         }
 140
 141                         /* Free the name we parsed. */
 142                         SAFE_FREE(entry_princ_s);
 143
 144                         /* Free the entry we just read. */
 145                         smb_krb5_kt_free_entry(context, &kt_entry);
 146                         ZERO_STRUCT(kt_entry);
 147                 }
 148                 krb5_kt_end_seq_get(context, keytab, &kt_cursor);
 149         }
 150
 151         ZERO_STRUCT(kt_cursor);
 152
 153   out:
 154
 155         for (i = 0; i < sizeof(valid_princ_formats) / sizeof(valid_princ_formats[0]); i++) {
 156                 SAFE_FREE(valid_princ_formats[i]);
 157         }
 158
 159         if (!auth_ok) {
 160                 if (!number_matched_principals) {
 161                         DEBUG(3, ("ads_keytab_verify_ticket: no keytab principals matched expected file service name.\n"));
 162                 } else {
 163                         DEBUG(3, ("ads_keytab_verify_ticket: krb5_rd_req failed for all %d matched keytab principals\n",
 164                                 number_matched_principals));
 165                 }
 166         }
 167
 168         SAFE_FREE(entry_princ_s);
 169
 170         {
 171                 krb5_keytab_entry zero_kt_entry;
 172                 ZERO_STRUCT(zero_kt_entry);
 173                 if (memcmp(&zero_kt_entry, &kt_entry, sizeof(krb5_keytab_entry))) {
 174                         smb_krb5_kt_free_entry(context, &kt_entry);
 175                 }
 176         }
 177
 178         {
 179                 krb5_kt_cursor zero_csr;
 180                 ZERO_STRUCT(zero_csr);
 181                 if ((memcmp(&kt_cursor, &zero_csr, sizeof(krb5_kt_cursor)) != 0) && keytab) {
 182                         krb5_kt_end_seq_get(context, keytab, &kt_cursor);
 183                 }
 184         }
 185
 186         if (keytab) {
 187                 krb5_kt_close(context, keytab);
 188         }
 189         return auth_ok;
 190 }
 191
 192 /**********************************************************************************
 193  Try to verify a ticket using the secrets.tdb.
 194 ***********************************************************************************/
 195
 196 static BOOL ads_secrets_verify_ticket(krb5_context context, krb5_auth_context auth_context,
 197                                       krb5_principal host_princ,
 198                                       const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt,
 199                                       krb5_keyblock **keyblock)
 200 {
 201         krb5_error_code ret = 0;
 202         BOOL auth_ok = False;
 203         char *password_s = NULL;
 204         krb5_data password;
 205         krb5_enctype enctypes[4] = { ENCTYPE_DES_CBC_CRC, ENCTYPE_DES_CBC_MD5, 0, 0 };
 206         int i;
 207
 208 #if defined(ENCTYPE_ARCFOUR_HMAC)
 209         enctypes[2] = ENCTYPE_ARCFOUR_HMAC;
 210 #endif
 211
 212         ZERO_STRUCTP(keyblock);
 213
 214         if (!secrets_init()) {
 215                 DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
 216                 return False;
 217         }
 218
 219         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 220         if (!password_s) {
 221                 DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
 222                 return False;
 223         }
 224
 225         password.data = password_s;
 226         password.length = strlen(password_s);
 227
 228         /* CIFS doesn't use addresses in tickets. This would break NAT. JRA */
 229
 230         p_packet->length = ticket->length;
 231         p_packet->data = (krb5_pointer)ticket->data;
 232
 233         /* We need to setup a auth context with each possible encoding type in turn. */
 234         for (i=0;enctypes[i];i++) {
 235                 krb5_keyblock *key = NULL;
 236
 237                 if (!(key = SMB_MALLOC_P(krb5_keyblock))) {
 238                         goto out;
 239                 }
 240
 241                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
 242                         SAFE_FREE(key);
 243                         continue;
 244                 }
 245
 246                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 247
 248                 if (!(ret = krb5_rd_req(context, &auth_context, p_packet,
 249                                         NULL,
 250                                         NULL, NULL, pp_tkt))) {
 251                         DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
 252                                 (unsigned int)enctypes[i] ));
 253                         auth_ok = True;
 254                         krb5_copy_keyblock(context, key, keyblock);
 255                         krb5_free_keyblock(context, key);
 256                         break;
 257                 }
 258
 259                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 260                                 ("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 261                                 (unsigned int)enctypes[i], error_message(ret)));
 262
 263                 /* successfully decrypted but ticket is just not valid at the moment */
 264                 if (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 265                     ret == KRB5KRB_AP_ERR_TKT_EXPIRED) {
 266                         break;
 267                 }
 268
 269                 krb5_free_keyblock(context, key);
 270
 271         }
 272
 273  out:
 274         SAFE_FREE(password_s);
 275
 276         return auth_ok;
 277 }
 278
 279 /**********************************************************************************
 280  Verify an incoming ticket and parse out the principal name and
 281  authorization_data if available.
 282 ***********************************************************************************/
 283
 284 NTSTATUS ads_verify_ticket(TALLOC_CTX *mem_ctx,
 285                            const char *realm, time_t time_offset,
 286                            const DATA_BLOB *ticket,
 287                            char **principal, PAC_DATA **pac_data,
 288                            DATA_BLOB *ap_rep,
 289                            DATA_BLOB *session_key)
 290 {
 291         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 292         NTSTATUS pac_ret;
 293         DATA_BLOB auth_data;
 294         krb5_context context = NULL;
 295         krb5_auth_context auth_context = NULL;
 296         krb5_data packet;
 297         krb5_ticket *tkt = NULL;
 298         krb5_rcache rcache = NULL;
 299         krb5_keyblock *keyblock = NULL;
 300         time_t authtime;
 301         int ret;
 302
 303         krb5_principal host_princ = NULL;
 304         krb5_const_principal client_principal = NULL;
 305         char *host_princ_s = NULL;
 306         BOOL got_replay_mutex = False;
 307
 308         BOOL auth_ok = False;
 309         BOOL got_auth_data = False;
 310
 311         ZERO_STRUCT(packet);
 312         ZERO_STRUCT(auth_data);
 313         ZERO_STRUCTP(ap_rep);
 314         ZERO_STRUCTP(session_key);
 315
 316         initialize_krb5_error_table();
 317         ret = krb5_init_context(&context);
 318         if (ret) {
 319                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 320                 return NT_STATUS_LOGON_FAILURE;
 321         }
 322
 323         if (time_offset != 0) {
 324                 krb5_set_real_time(context, time(NULL) + time_offset, 0);
 325         }
 326
 327         ret = krb5_set_default_realm(context, realm);
 328         if (ret) {
 329                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 330                 goto out;
 331         }
 332
 333         /* This whole process is far more complex than I would
 334            like. We have to go through all this to allow us to store
 335            the secret internally, instead of using /etc/krb5.keytab */
 336
 337         ret = krb5_auth_con_init(context, &auth_context);
 338         if (ret) {
 339                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 340                 goto out;
 341         }
 342
 343         asprintf(&host_princ_s, "%s$", global_myname());
 344         strlower_m(host_princ_s);
 345         ret = smb_krb5_parse_name(context, host_princ_s, &host_princ);
 346         if (ret) {
 347                 DEBUG(1,("ads_verify_ticket: smb_krb5_parse_name(%s) failed (%s)\n",
 348                                         host_princ_s, error_message(ret)));
 349                 goto out;
 350         }
 351
 352
 353         /* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
 354          * code surrounding the replay cache... */
 355
 356         if (!grab_server_mutex("replay cache mutex")) {
 357                 DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
 358                 goto out;
 359         }
 360
 361         got_replay_mutex = True;
 362
 363         /*
 364          * JRA. We must set the rcache here. This will prevent replay attacks.
 365          */
 366
 367         ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
 368         if (ret) {
 369                 DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
 370                 goto out;
 371         }
 372
 373         ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 374         if (ret) {
 375                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
 376                 goto out;
 377         }
 378
 379         if (lp_use_kerberos_keytab()) {
 380                 auth_ok = ads_keytab_verify_ticket(context, auth_context, ticket, &packet, &tkt, &keyblock);
 381         }
 382         if (!auth_ok) {
 383                 auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
 384                                                     ticket, &packet, &tkt, &keyblock);
 385         }
 386
 387         release_server_mutex();
 388         got_replay_mutex = False;
 389
 390 #if 0
 391         /* Heimdal leaks here, if we fix the leak, MIT crashes */
 392         if (rcache) {
 393                 krb5_rc_close(context, rcache);
 394         }
 395 #endif
 396
 397         if (!auth_ok) {
 398                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 399                          error_message(ret)));
 400                 goto out;
 401         }
 402
 403         authtime = get_authtime_from_tkt(tkt);
 404         client_principal = get_principal_from_tkt(tkt);
 405
 406         ret = krb5_mk_rep(context, auth_context, &packet);
 407         if (ret) {
 408                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 409                         error_message(ret)));
 410                 goto out;
 411         }
 412
 413         *ap_rep = data_blob(packet.data, packet.length);
 414         SAFE_FREE(packet.data);
 415         packet.length = 0;
 416
 417         get_krb5_smb_session_key(context, auth_context, session_key, True);
 418         dump_data_pw("SMB session key (from ticket)\n", session_key->data, session_key->length);
 419
 420 #if 0
 421         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 422 #endif
 423
 424         /* continue when no PAC is retrieved or we couldn't decode the PAC
 425            (like accounts that have the UF_NO_AUTH_DATA_REQUIRED flag set, or
 426            Kerberos tickets encrypted using a DES key) - Guenther */
 427
 428         got_auth_data = get_auth_data_from_tkt(mem_ctx, &auth_data, tkt);
 429         if (!got_auth_data) {
 430                 DEBUG(3,("ads_verify_ticket: did not retrieve auth data. continuing without PAC\n"));
 431         }
 432
 433         if (got_auth_data && pac_data != NULL) {
 434
 435                 pac_ret = decode_pac_data(mem_ctx, &auth_data, context, keyblock, client_principal, authtime, pac_data);
 436                 if (!NT_STATUS_IS_OK(pac_ret)) {
 437                         DEBUG(3,("ads_verify_ticket: failed to decode PAC_DATA: %s\n", nt_errstr(pac_ret)));
 438                         *pac_data = NULL;
 439                 }
 440                 data_blob_free(&auth_data);
 441         }
 442
 443 #if 0
 444 #if defined(HAVE_KRB5_TKT_ENC_PART2)
 445         /* MIT */
 446         if (tkt->enc_part2) {
 447                 file_save("/tmp/authdata.dat",
 448                           tkt->enc_part2->authorization_data[0]->contents,
 449                           tkt->enc_part2->authorization_data[0]->length);
 450         }
 451 #else
 452         /* Heimdal */
 453         if (tkt->ticket.authorization_data) {
 454                 file_save("/tmp/authdata.dat",
 455                           tkt->ticket.authorization_data->val->ad_data.data,
 456                           tkt->ticket.authorization_data->val->ad_data.length);
 457         }
 458 #endif
 459 #endif
 460
 461         if ((ret = smb_krb5_unparse_name(context, client_principal, principal))) {
 462                 DEBUG(3,("ads_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
 463                          error_message(ret)));
 464                 sret = NT_STATUS_LOGON_FAILURE;
 465                 goto out;
 466         }
 467
 468         sret = NT_STATUS_OK;
 469
 470  out:
 471
 472         if (got_replay_mutex) {
 473                 release_server_mutex();
 474         }
 475
 476         if (!NT_STATUS_IS_OK(sret)) {
 477                 data_blob_free(&auth_data);
 478         }
 479
 480         if (!NT_STATUS_IS_OK(sret)) {
 481                 data_blob_free(ap_rep);
 482         }
 483
 484         if (host_princ) {
 485                 krb5_free_principal(context, host_princ);
 486         }
 487
 488         if (keyblock) {
 489                 krb5_free_keyblock(context, keyblock);
 490         }
 491
 492         if (tkt != NULL) {
 493                 krb5_free_ticket(context, tkt);
 494         }
 495
 496         SAFE_FREE(host_princ_s);
 497
 498         if (auth_context) {
 499                 krb5_auth_con_free(context, auth_context);
 500         }
 501
 502         if (context) {
 503                 krb5_free_context(context);
 504         }
 505
 506         return sret;
 507 }
 508
 509 #endif /* HAVE_KRB5 */