auth/kerberos/kerberos_pac.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    kerberos authorization data (PAC) utility library
   4    Copyright (C) Jim McDonough <jmcd@us.ibm.com> 2003
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
   6    Copyright (C) Andrew Tridgell 2001
   7    Copyright (C) Luke Howard 2002-2003
   8    Copyright (C) Stefan Metzmacher 2004-2005
   9    Copyright (C) Guenther Deschner 2005,2007,2008
  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 3 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, see <http://www.gnu.org/licenses/>.
  23 */
  24
  25 #include "includes.h"
  26 #ifdef HAVE_KRB5
  27
  28 #include "librpc/gen_ndr/ndr_krb5pac.h"
  29 #include "auth/kerberos/pac_utils.h"
  30
  31 krb5_error_code check_pac_checksum(DATA_BLOB pac_data,
  32                                           struct PAC_SIGNATURE_DATA *sig,
  33                                           krb5_context context,
  34                                           const krb5_keyblock *keyblock)
  35 {
  36         krb5_error_code ret;
  37         krb5_checksum cksum;
  38         krb5_keyusage usage = 0;
  39         krb5_boolean checksum_valid = false;
  40         krb5_data input;
  41
  42         switch (sig->type) {
  43         case CKSUMTYPE_HMAC_MD5:
  44                 /* ignores the key type */
  45                 break;
  46         case CKSUMTYPE_HMAC_SHA1_96_AES_256:
  47                 if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES256_CTS_HMAC_SHA1_96) {
  48                         return EINVAL;
  49                 }
  50                 /* ok */
  51                 break;
  52         case CKSUMTYPE_HMAC_SHA1_96_AES_128:
  53                 if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES128_CTS_HMAC_SHA1_96) {
  54                         return EINVAL;
  55                 }
  56                 /* ok */
  57                 break;
  58         default:
  59                 DEBUG(2,("check_pac_checksum: Checksum Type %d is not supported\n",
  60                         (int)sig->type));
  61                 return EINVAL;
  62         }
  63
  64 #ifdef HAVE_CHECKSUM_IN_KRB5_CHECKSUM /* Heimdal */
  65         cksum.cksumtype = (krb5_cksumtype)sig->type;
  66         cksum.checksum.length   = sig->signature.length;
  67         cksum.checksum.data     = sig->signature.data;
  68 #else /* MIT */
  69         cksum.checksum_type     = (krb5_cksumtype)sig->type;
  70         cksum.length            = sig->signature.length;
  71         cksum.contents          = sig->signature.data;
  72 #endif
  73
  74 #ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
  75         usage = KRB5_KU_OTHER_CKSUM;
  76 #elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
  77         usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
  78 #else
  79 #error UNKNOWN_KRB5_KEYUSAGE
  80 #endif
  81
  82         input.data = (char *)pac_data.data;
  83         input.length = pac_data.length;
  84
  85         ret = krb5_c_verify_checksum(context,
  86                                      keyblock,
  87                                      usage,
  88                                      &input,
  89                                      &cksum,
  90                                      &checksum_valid);
  91         if (!checksum_valid) {
  92                 ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
  93         }
  94         if (ret){
  95                 DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
  96                         error_message(ret), ret));
  97                 return ret;
  98         }
  99
 100         return ret;
 101 }
 102
 103 /**
 104 * @brief Decode a blob containing a NDR encoded PAC structure
 105 *
 106 * @param mem_ctx          - The memory context
 107 * @param pac_data_blob    - The data blob containing the NDR encoded data
 108 * @param context          - The Kerberos Context
 109 * @param service_keyblock - The Service Key used to verify the checksum
 110 * @param client_principal - The client principal
 111 * @param tgs_authtime     - The ticket timestamp
 112 * @param pac_data_out     - [out] The decoded PAC
 113 *
 114 * @return - A NTSTATUS error code
 115 */
 116 NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
 117                              DATA_BLOB pac_data_blob,
 118                              krb5_context context,
 119                              const krb5_keyblock *krbtgt_keyblock,
 120                              const krb5_keyblock *service_keyblock,
 121                              krb5_const_principal client_principal,
 122                              time_t tgs_authtime,
 123                              struct PAC_DATA **pac_data_out)
 124 {
 125         NTSTATUS status;
 126         enum ndr_err_code ndr_err;
 127         krb5_error_code ret;
 128         DATA_BLOB modified_pac_blob;
 129
 130         NTTIME tgs_authtime_nttime;
 131         int i;
 132
 133         struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
 134         struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
 135         struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
 136         struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
 137         struct PAC_LOGON_NAME *logon_name = NULL;
 138         struct PAC_LOGON_INFO *logon_info = NULL;
 139         struct PAC_DATA *pac_data = NULL;
 140         struct PAC_DATA_RAW *pac_data_raw = NULL;
 141
 142         DATA_BLOB *srv_sig_blob = NULL;
 143         DATA_BLOB *kdc_sig_blob = NULL;
 144
 145         bool bool_ret;
 146
 147         TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
 148         if (!tmp_ctx) {
 149                 return NT_STATUS_NO_MEMORY;
 150         }
 151
 152         if (pac_data_out) {
 153                 *pac_data_out = NULL;
 154         }
 155
 156         pac_data = talloc(tmp_ctx, struct PAC_DATA);
 157         pac_data_raw = talloc(tmp_ctx, struct PAC_DATA_RAW);
 158         kdc_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 159         srv_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 160         if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
 161                 talloc_free(tmp_ctx);
 162                 return NT_STATUS_NO_MEMORY;
 163         }
 164
 165         ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
 166                        (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
 167         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 168                 status = ndr_map_error2ntstatus(ndr_err);
 169                 DEBUG(0,("can't parse the PAC: %s\n",
 170                         nt_errstr(status)));
 171                 talloc_free(tmp_ctx);
 172                 return status;
 173         }
 174
 175         if (pac_data->num_buffers < 4) {
 176                 /* we need logon_ingo, service_key and kdc_key */
 177                 DEBUG(0,("less than 4 PAC buffers\n"));
 178                 talloc_free(tmp_ctx);
 179                 return NT_STATUS_INVALID_PARAMETER;
 180         }
 181
 182         ndr_err = ndr_pull_struct_blob(
 183                                 &pac_data_blob, pac_data_raw, pac_data_raw,
 184                                 (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
 185         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 186                 status = ndr_map_error2ntstatus(ndr_err);
 187                 DEBUG(0,("can't parse the PAC: %s\n",
 188                         nt_errstr(status)));
 189                 talloc_free(tmp_ctx);
 190                 return status;
 191         }
 192
 193         if (pac_data_raw->num_buffers < 4) {
 194                 /* we need logon_ingo, service_key and kdc_key */
 195                 DEBUG(0,("less than 4 PAC buffers\n"));
 196                 talloc_free(tmp_ctx);
 197                 return NT_STATUS_INVALID_PARAMETER;
 198         }
 199
 200         if (pac_data->num_buffers != pac_data_raw->num_buffers) {
 201                 /* we need logon_ingo, service_key and kdc_key */
 202                 DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
 203                           "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
 204                           pac_data_raw->num_buffers));
 205                 talloc_free(tmp_ctx);
 206                 return NT_STATUS_INVALID_PARAMETER;
 207         }
 208
 209         for (i=0; i < pac_data->num_buffers; i++) {
 210                 struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
 211                 struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
 212
 213                 if (data_buf->type != raw_buf->type) {
 214                         DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
 215                                   "%d while PAC_DATA_RAW has %d\n", i,
 216                                   data_buf->type, raw_buf->type));
 217                         talloc_free(tmp_ctx);
 218                         return NT_STATUS_INVALID_PARAMETER;
 219                 }
 220                 switch (data_buf->type) {
 221                 case PAC_TYPE_LOGON_INFO:
 222                         if (!data_buf->info) {
 223                                 break;
 224                         }
 225                         logon_info = data_buf->info->logon_info.info;
 226                         break;
 227                 case PAC_TYPE_SRV_CHECKSUM:
 228                         if (!data_buf->info) {
 229                                 break;
 230                         }
 231                         srv_sig_ptr = &data_buf->info->srv_cksum;
 232                         srv_sig_blob = &raw_buf->info->remaining;
 233                         break;
 234                 case PAC_TYPE_KDC_CHECKSUM:
 235                         if (!data_buf->info) {
 236                                 break;
 237                         }
 238                         kdc_sig_ptr = &data_buf->info->kdc_cksum;
 239                         kdc_sig_blob = &raw_buf->info->remaining;
 240                         break;
 241                 case PAC_TYPE_LOGON_NAME:
 242                         logon_name = &data_buf->info->logon_name;
 243                         break;
 244                 default:
 245                         break;
 246                 }
 247         }
 248
 249         if (!logon_info) {
 250                 DEBUG(0,("PAC no logon_info\n"));
 251                 talloc_free(tmp_ctx);
 252                 return NT_STATUS_INVALID_PARAMETER;
 253         }
 254
 255         if (!logon_name) {
 256                 DEBUG(0,("PAC no logon_name\n"));
 257                 talloc_free(tmp_ctx);
 258                 return NT_STATUS_INVALID_PARAMETER;
 259         }
 260
 261         if (!srv_sig_ptr || !srv_sig_blob) {
 262                 DEBUG(0,("PAC no srv_key\n"));
 263                 talloc_free(tmp_ctx);
 264                 return NT_STATUS_INVALID_PARAMETER;
 265         }
 266
 267         if (!kdc_sig_ptr || !kdc_sig_blob) {
 268                 DEBUG(0,("PAC no kdc_key\n"));
 269                 talloc_free(tmp_ctx);
 270                 return NT_STATUS_INVALID_PARAMETER;
 271         }
 272
 273         /* Find and zero out the signatures,
 274          * as required by the signing algorithm */
 275
 276         /* We find the data blobs above,
 277          * now we parse them to get at the exact portion we should zero */
 278         ndr_err = ndr_pull_struct_blob(
 279                         kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
 280                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 281         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 282                 status = ndr_map_error2ntstatus(ndr_err);
 283                 DEBUG(0,("can't parse the KDC signature: %s\n",
 284                         nt_errstr(status)));
 285                 talloc_free(tmp_ctx);
 286                 return status;
 287         }
 288
 289         ndr_err = ndr_pull_struct_blob(
 290                         srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
 291                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 292         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 293                 status = ndr_map_error2ntstatus(ndr_err);
 294                 DEBUG(0,("can't parse the SRV signature: %s\n",
 295                         nt_errstr(status)));
 296                 talloc_free(tmp_ctx);
 297                 return status;
 298         }
 299
 300         /* Now zero the decoded structure */
 301         memset(kdc_sig_wipe->signature.data,
 302                 '\0', kdc_sig_wipe->signature.length);
 303         memset(srv_sig_wipe->signature.data,
 304                 '\0', srv_sig_wipe->signature.length);
 305
 306         /* and reencode, back into the same place it came from */
 307         ndr_err = ndr_push_struct_blob(
 308                         kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
 309                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 310         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 311                 status = ndr_map_error2ntstatus(ndr_err);
 312                 DEBUG(0,("can't repack the KDC signature: %s\n",
 313                         nt_errstr(status)));
 314                 talloc_free(tmp_ctx);
 315                 return status;
 316         }
 317         ndr_err = ndr_push_struct_blob(
 318                         srv_sig_blob, pac_data_raw, srv_sig_wipe,
 319                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 320         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 321                 status = ndr_map_error2ntstatus(ndr_err);
 322                 DEBUG(0,("can't repack the SRV signature: %s\n",
 323                         nt_errstr(status)));
 324                 talloc_free(tmp_ctx);
 325                 return status;
 326         }
 327
 328         /* push out the whole structure, but now with zero'ed signatures */
 329         ndr_err = ndr_push_struct_blob(
 330                         &modified_pac_blob, pac_data_raw, pac_data_raw,
 331                         (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
 332         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 333                 status = ndr_map_error2ntstatus(ndr_err);
 334                 DEBUG(0,("can't repack the RAW PAC: %s\n",
 335                         nt_errstr(status)));
 336                 talloc_free(tmp_ctx);
 337                 return status;
 338         }
 339
 340         if (service_keyblock) {
 341                 /* verify by service_key */
 342                 ret = check_pac_checksum(modified_pac_blob, srv_sig_ptr,
 343                                          context,
 344                                          service_keyblock);
 345                 if (ret) {
 346                         DEBUG(5, ("PAC Decode: Failed to verify the service "
 347                                   "signature: %s\n", error_message(ret)));
 348                         return NT_STATUS_ACCESS_DENIED;
 349                 }
 350
 351                 if (krbtgt_keyblock) {
 352                         /* verify the service key checksum by krbtgt_key */
 353                         ret = check_pac_checksum(srv_sig_ptr->signature, kdc_sig_ptr,
 354                                                  context, krbtgt_keyblock);
 355                         if (ret) {
 356                                 DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
 357                                           smb_get_krb5_error_message(context, ret, tmp_ctx)));
 358                                 talloc_free(tmp_ctx);
 359                                 return NT_STATUS_ACCESS_DENIED;
 360                         }
 361                 }
 362         }
 363
 364         if (tgs_authtime) {
 365                 /* Convert to NT time, so as not to loose accuracy in comparison */
 366                 unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
 367
 368                 if (tgs_authtime_nttime != logon_name->logon_time) {
 369                         DEBUG(2, ("PAC Decode: "
 370                                   "Logon time mismatch between ticket and PAC!\n"));
 371                         DEBUG(2, ("PAC Decode: PAC: %s\n",
 372                                   nt_time_string(tmp_ctx, logon_name->logon_time)));
 373                         DEBUG(2, ("PAC Decode: Ticket: %s\n",
 374                                   nt_time_string(tmp_ctx, tgs_authtime_nttime)));
 375                         talloc_free(tmp_ctx);
 376                         return NT_STATUS_ACCESS_DENIED;
 377                 }
 378         }
 379
 380         if (client_principal) {
 381                 char *client_principal_string;
 382                 ret = krb5_unparse_name_flags(context, client_principal,
 383                                               KRB5_PRINCIPAL_UNPARSE_NO_REALM|KRB5_PRINCIPAL_UNPARSE_DISPLAY,
 384                                               &client_principal_string);
 385                 if (ret) {
 386                         DEBUG(2, ("Could not unparse name from ticket to match with name from PAC: [%s]:%s\n",
 387                                   logon_name->account_name, error_message(ret)));
 388                         talloc_free(tmp_ctx);
 389                         return NT_STATUS_INVALID_PARAMETER;
 390                 }
 391
 392                 bool_ret = strcmp(client_principal_string, logon_name->account_name) == 0;
 393
 394                 if (!bool_ret) {
 395                         DEBUG(2, ("Name in PAC [%s] does not match principal name "
 396                                   "in ticket [%s]\n",
 397                                   logon_name->account_name,
 398                                   client_principal_string));
 399                         SAFE_FREE(client_principal_string);
 400                         talloc_free(tmp_ctx);
 401                         return NT_STATUS_ACCESS_DENIED;
 402                 }
 403                 SAFE_FREE(client_principal_string);
 404
 405         }
 406
 407         DEBUG(3,("Found account name from PAC: %s [%s]\n",
 408                  logon_info->info3.base.account_name.string,
 409                  logon_info->info3.base.full_name.string));
 410
 411         DEBUG(10,("Successfully validated Kerberos PAC\n"));
 412
 413         if (DEBUGLEVEL >= 10) {
 414                 const char *s;
 415                 s = NDR_PRINT_STRUCT_STRING(tmp_ctx, PAC_DATA, pac_data);
 416                 if (s) {
 417                         DEBUGADD(10,("%s\n", s));
 418                 }
 419         }
 420
 421         if (pac_data_out) {
 422                 *pac_data_out = talloc_steal(mem_ctx, pac_data);
 423         }
 424
 425         return NT_STATUS_OK;
 426 }
 427
 428 NTSTATUS kerberos_pac_logon_info(TALLOC_CTX *mem_ctx,
 429                                  DATA_BLOB blob,
 430                                  krb5_context context,
 431                                  const krb5_keyblock *krbtgt_keyblock,
 432                                  const krb5_keyblock *service_keyblock,
 433                                  krb5_const_principal client_principal,
 434                                  time_t tgs_authtime,
 435                                  struct PAC_LOGON_INFO **logon_info)
 436 {
 437         NTSTATUS nt_status;
 438         struct PAC_DATA *pac_data;
 439         int i;
 440         nt_status = kerberos_decode_pac(mem_ctx,
 441                                         blob,
 442                                         context,
 443                                         krbtgt_keyblock,
 444                                         service_keyblock,
 445                                         client_principal,
 446                                         tgs_authtime,
 447                                         &pac_data);
 448         if (!NT_STATUS_IS_OK(nt_status)) {
 449                 return nt_status;
 450         }
 451
 452         *logon_info = NULL;
 453         for (i=0; i < pac_data->num_buffers; i++) {
 454                 if (pac_data->buffers[i].type != PAC_TYPE_LOGON_INFO) {
 455                         continue;
 456                 }
 457                 *logon_info = pac_data->buffers[i].info->logon_info.info;
 458         }
 459         if (!*logon_info) {
 460                 return NT_STATUS_INVALID_PARAMETER;
 461         }
 462         return NT_STATUS_OK;
 463 }
 464
 465 #endif