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
  27 #undef DBGC_CLASS
  28 #define DBGC_CLASS DBGC_AUTH
  29
  30 #ifdef HAVE_KRB5
  31
  32 #include "librpc/gen_ndr/ndr_krb5pac.h"
  33 #include "auth/kerberos/pac_utils.h"
  34
  35 krb5_error_code check_pac_checksum(DATA_BLOB pac_data,
  36                                           struct PAC_SIGNATURE_DATA *sig,
  37                                           krb5_context context,
  38                                           const krb5_keyblock *keyblock)
  39 {
  40         krb5_error_code ret;
  41         krb5_checksum cksum;
  42         krb5_keyusage usage = 0;
  43         krb5_boolean checksum_valid = false;
  44         krb5_data input;
  45
  46         switch (sig->type) {
  47         case CKSUMTYPE_HMAC_MD5:
  48                 /* ignores the key type */
  49                 break;
  50         case CKSUMTYPE_HMAC_SHA1_96_AES_256:
  51                 if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES256_CTS_HMAC_SHA1_96) {
  52                         return EINVAL;
  53                 }
  54                 /* ok */
  55                 break;
  56         case CKSUMTYPE_HMAC_SHA1_96_AES_128:
  57                 if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES128_CTS_HMAC_SHA1_96) {
  58                         return EINVAL;
  59                 }
  60                 /* ok */
  61                 break;
  62         default:
  63                 DEBUG(2,("check_pac_checksum: Checksum Type %d is not supported\n",
  64                         (int)sig->type));
  65                 return EINVAL;
  66         }
  67
  68 #ifdef HAVE_CHECKSUM_IN_KRB5_CHECKSUM /* Heimdal */
  69         cksum.cksumtype = (krb5_cksumtype)sig->type;
  70         cksum.checksum.length   = sig->signature.length;
  71         cksum.checksum.data     = sig->signature.data;
  72 #else /* MIT */
  73         cksum.checksum_type     = (krb5_cksumtype)sig->type;
  74         cksum.length            = sig->signature.length;
  75         cksum.contents          = sig->signature.data;
  76 #endif
  77
  78 #ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
  79         usage = KRB5_KU_OTHER_CKSUM;
  80 #elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
  81         usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
  82 #else
  83 #error UNKNOWN_KRB5_KEYUSAGE
  84 #endif
  85
  86         input.data = (char *)pac_data.data;
  87         input.length = pac_data.length;
  88
  89         ret = krb5_c_verify_checksum(context,
  90                                      keyblock,
  91                                      usage,
  92                                      &input,
  93                                      &cksum,
  94                                      &checksum_valid);
  95         if (!checksum_valid) {
  96                 ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
  97         }
  98         if (ret){
  99                 DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
 100                         error_message(ret), ret));
 101                 return ret;
 102         }
 103
 104         return ret;
 105 }
 106
 107 /**
 108 * @brief Decode a blob containing a NDR encoded PAC structure
 109 *
 110 * @param mem_ctx          - The memory context
 111 * @param pac_data_blob    - The data blob containing the NDR encoded data
 112 * @param context          - The Kerberos Context
 113 * @param service_keyblock - The Service Key used to verify the checksum
 114 * @param client_principal - The client principal
 115 * @param tgs_authtime     - The ticket timestamp
 116 * @param pac_data_out     - [out] The decoded PAC
 117 *
 118 * @return - A NTSTATUS error code
 119 */
 120 NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
 121                              DATA_BLOB pac_data_blob,
 122                              krb5_context context,
 123                              const krb5_keyblock *krbtgt_keyblock,
 124                              const krb5_keyblock *service_keyblock,
 125                              krb5_const_principal client_principal,
 126                              time_t tgs_authtime,
 127                              struct PAC_DATA **pac_data_out)
 128 {
 129         NTSTATUS status;
 130         enum ndr_err_code ndr_err;
 131         krb5_error_code ret;
 132         DATA_BLOB modified_pac_blob;
 133
 134         NTTIME tgs_authtime_nttime;
 135         int i;
 136
 137         struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
 138         struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
 139         struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
 140         struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
 141         struct PAC_LOGON_NAME *logon_name = NULL;
 142         struct PAC_LOGON_INFO *logon_info = NULL;
 143         struct PAC_DATA *pac_data = NULL;
 144         struct PAC_DATA_RAW *pac_data_raw = NULL;
 145
 146         DATA_BLOB *srv_sig_blob = NULL;
 147         DATA_BLOB *kdc_sig_blob = NULL;
 148
 149         bool bool_ret;
 150
 151         TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
 152         if (!tmp_ctx) {
 153                 return NT_STATUS_NO_MEMORY;
 154         }
 155
 156         if (pac_data_out) {
 157                 *pac_data_out = NULL;
 158         }
 159
 160         pac_data = talloc(tmp_ctx, struct PAC_DATA);
 161         pac_data_raw = talloc(tmp_ctx, struct PAC_DATA_RAW);
 162         kdc_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 163         srv_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 164         if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
 165                 talloc_free(tmp_ctx);
 166                 return NT_STATUS_NO_MEMORY;
 167         }
 168
 169         ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
 170                        (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
 171         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 172                 status = ndr_map_error2ntstatus(ndr_err);
 173                 DEBUG(0,("can't parse the PAC: %s\n",
 174                         nt_errstr(status)));
 175                 talloc_free(tmp_ctx);
 176                 return status;
 177         }
 178
 179         if (pac_data->num_buffers < 4) {
 180                 /* we need logon_ingo, service_key and kdc_key */
 181                 DEBUG(0,("less than 4 PAC buffers\n"));
 182                 talloc_free(tmp_ctx);
 183                 return NT_STATUS_INVALID_PARAMETER;
 184         }
 185
 186         ndr_err = ndr_pull_struct_blob(
 187                                 &pac_data_blob, pac_data_raw, pac_data_raw,
 188                                 (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
 189         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 190                 status = ndr_map_error2ntstatus(ndr_err);
 191                 DEBUG(0,("can't parse the PAC: %s\n",
 192                         nt_errstr(status)));
 193                 talloc_free(tmp_ctx);
 194                 return status;
 195         }
 196
 197         if (pac_data_raw->num_buffers < 4) {
 198                 /* we need logon_ingo, service_key and kdc_key */
 199                 DEBUG(0,("less than 4 PAC buffers\n"));
 200                 talloc_free(tmp_ctx);
 201                 return NT_STATUS_INVALID_PARAMETER;
 202         }
 203
 204         if (pac_data->num_buffers != pac_data_raw->num_buffers) {
 205                 /* we need logon_ingo, service_key and kdc_key */
 206                 DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
 207                           "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
 208                           pac_data_raw->num_buffers));
 209                 talloc_free(tmp_ctx);
 210                 return NT_STATUS_INVALID_PARAMETER;
 211         }
 212
 213         for (i=0; i < pac_data->num_buffers; i++) {
 214                 struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
 215                 struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
 216
 217                 if (data_buf->type != raw_buf->type) {
 218                         DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
 219                                   "%d while PAC_DATA_RAW has %d\n", i,
 220                                   data_buf->type, raw_buf->type));
 221                         talloc_free(tmp_ctx);
 222                         return NT_STATUS_INVALID_PARAMETER;
 223                 }
 224                 switch (data_buf->type) {
 225                 case PAC_TYPE_LOGON_INFO:
 226                         if (!data_buf->info) {
 227                                 break;
 228                         }
 229                         logon_info = data_buf->info->logon_info.info;
 230                         break;
 231                 case PAC_TYPE_SRV_CHECKSUM:
 232                         if (!data_buf->info) {
 233                                 break;
 234                         }
 235                         srv_sig_ptr = &data_buf->info->srv_cksum;
 236                         srv_sig_blob = &raw_buf->info->remaining;
 237                         break;
 238                 case PAC_TYPE_KDC_CHECKSUM:
 239                         if (!data_buf->info) {
 240                                 break;
 241                         }
 242                         kdc_sig_ptr = &data_buf->info->kdc_cksum;
 243                         kdc_sig_blob = &raw_buf->info->remaining;
 244                         break;
 245                 case PAC_TYPE_LOGON_NAME:
 246                         logon_name = &data_buf->info->logon_name;
 247                         break;
 248                 default:
 249                         break;
 250                 }
 251         }
 252
 253         if (!logon_info) {
 254                 DEBUG(0,("PAC no logon_info\n"));
 255                 talloc_free(tmp_ctx);
 256                 return NT_STATUS_INVALID_PARAMETER;
 257         }
 258
 259         if (!logon_name) {
 260                 DEBUG(0,("PAC no logon_name\n"));
 261                 talloc_free(tmp_ctx);
 262                 return NT_STATUS_INVALID_PARAMETER;
 263         }
 264
 265         if (!srv_sig_ptr || !srv_sig_blob) {
 266                 DEBUG(0,("PAC no srv_key\n"));
 267                 talloc_free(tmp_ctx);
 268                 return NT_STATUS_INVALID_PARAMETER;
 269         }
 270
 271         if (!kdc_sig_ptr || !kdc_sig_blob) {
 272                 DEBUG(0,("PAC no kdc_key\n"));
 273                 talloc_free(tmp_ctx);
 274                 return NT_STATUS_INVALID_PARAMETER;
 275         }
 276
 277         /* Find and zero out the signatures,
 278          * as required by the signing algorithm */
 279
 280         /* We find the data blobs above,
 281          * now we parse them to get at the exact portion we should zero */
 282         ndr_err = ndr_pull_struct_blob(
 283                         kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
 284                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 285         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 286                 status = ndr_map_error2ntstatus(ndr_err);
 287                 DEBUG(0,("can't parse the KDC signature: %s\n",
 288                         nt_errstr(status)));
 289                 talloc_free(tmp_ctx);
 290                 return status;
 291         }
 292
 293         ndr_err = ndr_pull_struct_blob(
 294                         srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
 295                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 296         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 297                 status = ndr_map_error2ntstatus(ndr_err);
 298                 DEBUG(0,("can't parse the SRV signature: %s\n",
 299                         nt_errstr(status)));
 300                 talloc_free(tmp_ctx);
 301                 return status;
 302         }
 303
 304         /* Now zero the decoded structure */
 305         memset(kdc_sig_wipe->signature.data,
 306                 '\0', kdc_sig_wipe->signature.length);
 307         memset(srv_sig_wipe->signature.data,
 308                 '\0', srv_sig_wipe->signature.length);
 309
 310         /* and reencode, back into the same place it came from */
 311         ndr_err = ndr_push_struct_blob(
 312                         kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
 313                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 314         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 315                 status = ndr_map_error2ntstatus(ndr_err);
 316                 DEBUG(0,("can't repack the KDC signature: %s\n",
 317                         nt_errstr(status)));
 318                 talloc_free(tmp_ctx);
 319                 return status;
 320         }
 321         ndr_err = ndr_push_struct_blob(
 322                         srv_sig_blob, pac_data_raw, srv_sig_wipe,
 323                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 324         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 325                 status = ndr_map_error2ntstatus(ndr_err);
 326                 DEBUG(0,("can't repack the SRV signature: %s\n",
 327                         nt_errstr(status)));
 328                 talloc_free(tmp_ctx);
 329                 return status;
 330         }
 331
 332         /* push out the whole structure, but now with zero'ed signatures */
 333         ndr_err = ndr_push_struct_blob(
 334                         &modified_pac_blob, pac_data_raw, pac_data_raw,
 335                         (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
 336         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 337                 status = ndr_map_error2ntstatus(ndr_err);
 338                 DEBUG(0,("can't repack the RAW PAC: %s\n",
 339                         nt_errstr(status)));
 340                 talloc_free(tmp_ctx);
 341                 return status;
 342         }
 343
 344         if (service_keyblock) {
 345                 /* verify by service_key */
 346                 ret = check_pac_checksum(modified_pac_blob, srv_sig_ptr,
 347                                          context,
 348                                          service_keyblock);
 349                 if (ret) {
 350                         DEBUG(5, ("PAC Decode: Failed to verify the service "
 351                                   "signature: %s\n", error_message(ret)));
 352                         return NT_STATUS_ACCESS_DENIED;
 353                 }
 354
 355                 if (krbtgt_keyblock) {
 356                         /* verify the service key checksum by krbtgt_key */
 357                         ret = check_pac_checksum(srv_sig_ptr->signature, kdc_sig_ptr,
 358                                                  context, krbtgt_keyblock);
 359                         if (ret) {
 360                                 DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
 361                                           smb_get_krb5_error_message(context, ret, tmp_ctx)));
 362                                 talloc_free(tmp_ctx);
 363                                 return NT_STATUS_ACCESS_DENIED;
 364                         }
 365                 }
 366         }
 367
 368         if (tgs_authtime) {
 369                 /* Convert to NT time, so as not to loose accuracy in comparison */
 370                 unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
 371
 372                 if (tgs_authtime_nttime != logon_name->logon_time) {
 373                         DEBUG(2, ("PAC Decode: "
 374                                   "Logon time mismatch between ticket and PAC!\n"));
 375                         DEBUG(2, ("PAC Decode: PAC: %s\n",
 376                                   nt_time_string(tmp_ctx, logon_name->logon_time)));
 377                         DEBUG(2, ("PAC Decode: Ticket: %s\n",
 378                                   nt_time_string(tmp_ctx, tgs_authtime_nttime)));
 379                         talloc_free(tmp_ctx);
 380                         return NT_STATUS_ACCESS_DENIED;
 381                 }
 382         }
 383
 384         if (client_principal) {
 385                 char *client_principal_string;
 386                 ret = krb5_unparse_name_flags(context, client_principal,
 387                                               KRB5_PRINCIPAL_UNPARSE_NO_REALM|KRB5_PRINCIPAL_UNPARSE_DISPLAY,
 388                                               &client_principal_string);
 389                 if (ret) {
 390                         DEBUG(2, ("Could not unparse name from ticket to match with name from PAC: [%s]:%s\n",
 391                                   logon_name->account_name, error_message(ret)));
 392                         talloc_free(tmp_ctx);
 393                         return NT_STATUS_INVALID_PARAMETER;
 394                 }
 395
 396                 bool_ret = strcmp(client_principal_string, logon_name->account_name) == 0;
 397
 398                 if (!bool_ret) {
 399                         DEBUG(2, ("Name in PAC [%s] does not match principal name "
 400                                   "in ticket [%s]\n",
 401                                   logon_name->account_name,
 402                                   client_principal_string));
 403                         SAFE_FREE(client_principal_string);
 404                         talloc_free(tmp_ctx);
 405                         return NT_STATUS_ACCESS_DENIED;
 406                 }
 407                 SAFE_FREE(client_principal_string);
 408
 409         }
 410
 411         DEBUG(3,("Found account name from PAC: %s [%s]\n",
 412                  logon_info->info3.base.account_name.string,
 413                  logon_info->info3.base.full_name.string));
 414
 415         DEBUG(10,("Successfully validated Kerberos PAC\n"));
 416
 417         if (DEBUGLEVEL >= 10) {
 418                 const char *s;
 419                 s = NDR_PRINT_STRUCT_STRING(tmp_ctx, PAC_DATA, pac_data);
 420                 if (s) {
 421                         DEBUGADD(10,("%s\n", s));
 422                 }
 423         }
 424
 425         if (pac_data_out) {
 426                 *pac_data_out = talloc_steal(mem_ctx, pac_data);
 427         }
 428
 429         return NT_STATUS_OK;
 430 }
 431
 432 NTSTATUS kerberos_pac_logon_info(TALLOC_CTX *mem_ctx,
 433                                  DATA_BLOB blob,
 434                                  krb5_context context,
 435                                  const krb5_keyblock *krbtgt_keyblock,
 436                                  const krb5_keyblock *service_keyblock,
 437                                  krb5_const_principal client_principal,
 438                                  time_t tgs_authtime,
 439                                  struct PAC_LOGON_INFO **logon_info)
 440 {
 441         NTSTATUS nt_status;
 442         struct PAC_DATA *pac_data;
 443         int i;
 444         nt_status = kerberos_decode_pac(mem_ctx,
 445                                         blob,
 446                                         context,
 447                                         krbtgt_keyblock,
 448                                         service_keyblock,
 449                                         client_principal,
 450                                         tgs_authtime,
 451                                         &pac_data);
 452         if (!NT_STATUS_IS_OK(nt_status)) {
 453                 return nt_status;
 454         }
 455
 456         *logon_info = NULL;
 457         for (i=0; i < pac_data->num_buffers; i++) {
 458                 if (pac_data->buffers[i].type != PAC_TYPE_LOGON_INFO) {
 459                         continue;
 460                 }
 461                 *logon_info = pac_data->buffers[i].info->logon_info.info;
 462         }
 463         if (!*logon_info) {
 464                 return NT_STATUS_INVALID_PARAMETER;
 465         }
 466         return NT_STATUS_OK;
 467 }
 468
 469 #endif