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
  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 = NULL;
 206         int i;
 207
 208         ZERO_STRUCTP(keyblock);
 209
 210         if (!secrets_init()) {
 211                 DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
 212                 return False;
 213         }
 214
 215         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 216         if (!password_s) {
 217                 DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
 218                 return False;
 219         }
 220
 221         password.data = password_s;
 222         password.length = strlen(password_s);
 223
 224         /* CIFS doesn't use addresses in tickets. This would break NAT. JRA */
 225
 226         if ((ret = get_kerberos_allowed_etypes(context, &enctypes))) {
 227                 DEBUG(1,("ads_secrets_verify_ticket: krb5_get_permitted_enctypes failed (%s)\n",
 228                          error_message(ret)));
 229                 goto out;
 230         }
 231
 232         p_packet->length = ticket->length;
 233         p_packet->data = (krb5_pointer)ticket->data;
 234
 235         /* We need to setup a auth context with each possible encoding type in turn. */
 236         for (i=0;enctypes[i];i++) {
 237                 krb5_keyblock *key = NULL;
 238
 239                 if (!(key = SMB_MALLOC_P(krb5_keyblock))) {
 240                         goto out;
 241                 }
 242
 243                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
 244                         SAFE_FREE(key);
 245                         continue;
 246                 }
 247
 248                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 249
 250                 if (!(ret = krb5_rd_req(context, &auth_context, p_packet,
 251                                         NULL,
 252                                         NULL, NULL, pp_tkt))) {
 253                         DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
 254                                 (unsigned int)enctypes[i] ));
 255                         auth_ok = True;
 256                         krb5_copy_keyblock(context, key, keyblock);
 257                         krb5_free_keyblock(context, key);
 258                         break;
 259                 }
 260
 261                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 262                                 ("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 263                                 (unsigned int)enctypes[i], error_message(ret)));
 264
 265                 /* successfully decrypted but ticket is just not valid at the moment */
 266                 if (ret == KRB5KRB_AP_ERR_TKT_NYV ||
 267                     ret == KRB5KRB_AP_ERR_TKT_EXPIRED) {
 268                         break;
 269                 }
 270
 271                 krb5_free_keyblock(context, key);
 272
 273         }
 274
 275  out:
 276
 277         free_kerberos_etypes(context, enctypes);
 278         SAFE_FREE(password_s);
 279
 280         return auth_ok;
 281 }
 282
 283 /**********************************************************************************
 284  Verify an incoming ticket and parse out the principal name and
 285  authorization_data if available.
 286 ***********************************************************************************/
 287
 288 NTSTATUS ads_verify_ticket(TALLOC_CTX *mem_ctx,
 289                            const char *realm, const DATA_BLOB *ticket,
 290                            char **principal, PAC_DATA **pac_data,
 291                            DATA_BLOB *ap_rep,
 292                            DATA_BLOB *session_key)
 293 {
 294         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 295         NTSTATUS pac_ret;
 296         DATA_BLOB auth_data;
 297         krb5_context context = NULL;
 298         krb5_auth_context auth_context = NULL;
 299         krb5_data packet;
 300         krb5_ticket *tkt = NULL;
 301         krb5_rcache rcache = NULL;
 302         krb5_keyblock *keyblock = NULL;
 303         time_t authtime;
 304         int ret;
 305
 306         krb5_principal host_princ = NULL;
 307         krb5_const_principal client_principal = NULL;
 308         char *host_princ_s = NULL;
 309         BOOL got_replay_mutex = False;
 310
 311         BOOL auth_ok = False;
 312         BOOL got_auth_data = False;
 313
 314         ZERO_STRUCT(packet);
 315         ZERO_STRUCT(auth_data);
 316         ZERO_STRUCTP(ap_rep);
 317         ZERO_STRUCTP(session_key);
 318
 319         initialize_krb5_error_table();
 320         ret = krb5_init_context(&context);
 321         if (ret) {
 322                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 323                 return NT_STATUS_LOGON_FAILURE;
 324         }
 325
 326         ret = krb5_set_default_realm(context, realm);
 327         if (ret) {
 328                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 329                 goto out;
 330         }
 331
 332         /* This whole process is far more complex than I would
 333            like. We have to go through all this to allow us to store
 334            the secret internally, instead of using /etc/krb5.keytab */
 335
 336         ret = krb5_auth_con_init(context, &auth_context);
 337         if (ret) {
 338                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 339                 goto out;
 340         }
 341
 342         asprintf(&host_princ_s, "%s$", global_myname());
 343         strlower_m(host_princ_s);
 344         ret = smb_krb5_parse_name(context, host_princ_s, &host_princ);
 345         if (ret) {
 346                 DEBUG(1,("ads_verify_ticket: smb_krb5_parse_name(%s) failed (%s)\n",
 347                                         host_princ_s, error_message(ret)));
 348                 goto out;
 349         }
 350
 351
 352         /* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
 353          * code surrounding the replay cache... */
 354
 355         if (!grab_server_mutex("replay cache mutex")) {
 356                 DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
 357                 goto out;
 358         }
 359
 360         got_replay_mutex = True;
 361
 362         /*
 363          * JRA. We must set the rcache here. This will prevent replay attacks.
 364          */
 365
 366         ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
 367         if (ret) {
 368                 DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
 369                 goto out;
 370         }
 371
 372         ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 373         if (ret) {
 374                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
 375                 goto out;
 376         }
 377
 378         if (lp_use_kerberos_keytab()) {
 379                 auth_ok = ads_keytab_verify_ticket(context, auth_context, ticket, &packet, &tkt, &keyblock);
 380         }
 381         if (!auth_ok) {
 382                 auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
 383                                                     ticket, &packet, &tkt, &keyblock);
 384         }
 385
 386         release_server_mutex();
 387         got_replay_mutex = False;
 388
 389 #if 0
 390         /* Heimdal leaks here, if we fix the leak, MIT crashes */
 391         if (rcache) {
 392                 krb5_rc_close(context, rcache);
 393         }
 394 #endif
 395
 396         if (!auth_ok) {
 397                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 398                          error_message(ret)));
 399                 goto out;
 400         }
 401
 402         authtime = get_authtime_from_tkt(tkt);
 403         client_principal = get_principal_from_tkt(tkt);
 404
 405         ret = krb5_mk_rep(context, auth_context, &packet);
 406         if (ret) {
 407                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 408                         error_message(ret)));
 409                 goto out;
 410         }
 411
 412         *ap_rep = data_blob(packet.data, packet.length);
 413         SAFE_FREE(packet.data);
 414         packet.length = 0;
 415
 416         get_krb5_smb_session_key(context, auth_context, session_key, True);
 417         dump_data_pw("SMB session key (from ticket)\n", session_key->data, session_key->length);
 418
 419 #if 0
 420         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 421 #endif
 422
 423         /* continue when no PAC is retrieved or we couldn't decode the PAC
 424            (like accounts that have the UF_NO_AUTH_DATA_REQUIRED flag set, or
 425            Kerberos tickets encrypted using a DES key) - Guenther */
 426
 427         got_auth_data = get_auth_data_from_tkt(mem_ctx, &auth_data, tkt);
 428         if (!got_auth_data) {
 429                 DEBUG(3,("ads_verify_ticket: did not retrieve auth data. continuing without PAC\n"));
 430         }
 431
 432         if (got_auth_data && pac_data != NULL) {
 433
 434                 pac_ret = decode_pac_data(mem_ctx, &auth_data, context, keyblock, client_principal, authtime, pac_data);
 435                 if (!NT_STATUS_IS_OK(pac_ret)) {
 436                         DEBUG(3,("ads_verify_ticket: failed to decode PAC_DATA: %s\n", nt_errstr(pac_ret)));
 437                         *pac_data = NULL;
 438                 }
 439                 data_blob_free(&auth_data);
 440         }
 441
 442 #if 0
 443 #if defined(HAVE_KRB5_TKT_ENC_PART2)
 444         /* MIT */
 445         if (tkt->enc_part2) {
 446                 file_save("/tmp/authdata.dat",
 447                           tkt->enc_part2->authorization_data[0]->contents,
 448                           tkt->enc_part2->authorization_data[0]->length);
 449         }
 450 #else
 451         /* Heimdal */
 452         if (tkt->ticket.authorization_data) {
 453                 file_save("/tmp/authdata.dat",
 454                           tkt->ticket.authorization_data->val->ad_data.data,
 455                           tkt->ticket.authorization_data->val->ad_data.length);
 456         }
 457 #endif
 458 #endif
 459
 460         if ((ret = smb_krb5_unparse_name(context, client_principal, principal))) {
 461                 DEBUG(3,("ads_verify_ticket: smb_krb5_unparse_name failed (%s)\n",
 462                          error_message(ret)));
 463                 sret = NT_STATUS_LOGON_FAILURE;
 464                 goto out;
 465         }
 466
 467         sret = NT_STATUS_OK;
 468
 469  out:
 470
 471         if (got_replay_mutex) {
 472                 release_server_mutex();
 473         }
 474
 475         if (!NT_STATUS_IS_OK(sret)) {
 476                 data_blob_free(&auth_data);
 477         }
 478
 479         if (!NT_STATUS_IS_OK(sret)) {
 480                 data_blob_free(ap_rep);
 481         }
 482
 483         if (host_princ) {
 484                 krb5_free_principal(context, host_princ);
 485         }
 486
 487         if (keyblock) {
 488                 krb5_free_keyblock(context, keyblock);
 489         }
 490
 491         if (tkt != NULL) {
 492                 krb5_free_ticket(context, tkt);
 493         }
 494
 495         SAFE_FREE(host_princ_s);
 496
 497         if (auth_context) {
 498                 krb5_auth_con_free(context, auth_context);
 499         }
 500
 501         if (context) {
 502                 krb5_free_context(context);
 503         }
 504
 505         return sret;
 506 }
 507
 508 #endif /* HAVE_KRB5 */