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 #ifdef HAVE_CHECKSUM_IN_KRB5_CHECKSUM /* Heimdal */
  43         cksum.cksumtype = (krb5_cksumtype)sig->type;
  44         cksum.checksum.length   = sig->signature.length;
  45         cksum.checksum.data     = sig->signature.data;
  46 #else /* MIT */
  47         cksum.checksum_type     = (krb5_cksumtype)sig->type;
  48         cksum.length            = sig->signature.length;
  49         cksum.contents          = sig->signature.data;
  50 #endif
  51
  52 #ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
  53         usage = KRB5_KU_OTHER_CKSUM;
  54 #elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
  55         usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
  56 #else
  57 #error UNKNOWN_KRB5_KEYUSAGE
  58 #endif
  59
  60         input.data = (char *)pac_data.data;
  61         input.length = pac_data.length;
  62
  63         ret = krb5_c_verify_checksum(context,
  64                                      keyblock,
  65                                      usage,
  66                                      &input,
  67                                      &cksum,
  68                                      &checksum_valid);
  69         if (!checksum_valid) {
  70                 ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
  71         }
  72         if (ret){
  73                 DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
  74                         error_message(ret), ret));
  75                 return ret;
  76         }
  77
  78         return ret;
  79 }
  80
  81 /**
  82 * @brief Decode a blob containing a NDR envoded PAC structure
  83 *
  84 * @param mem_ctx          - The memory context
  85 * @param pac_data_blob    - The data blob containing the NDR encoded data
  86 * @param context          - The Kerberos Context
  87 * @param service_keyblock - The Service Key used to verify the checksum
  88 * @param client_principal - The client principal
  89 * @param tgs_authtime     - The ticket timestamp
  90 * @param pac_data_out     - [out] The decoded PAC
  91 *
  92 * @return - A NTSTATUS error code
  93 */
  94 NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
  95                              DATA_BLOB pac_data_blob,
  96                              krb5_context context,
  97                              const krb5_keyblock *krbtgt_keyblock,
  98                              const krb5_keyblock *service_keyblock,
  99                              krb5_const_principal client_principal,
 100                              time_t tgs_authtime,
 101                              struct PAC_DATA **pac_data_out)
 102 {
 103         NTSTATUS status;
 104         enum ndr_err_code ndr_err;
 105         krb5_error_code ret;
 106         DATA_BLOB modified_pac_blob;
 107
 108         NTTIME tgs_authtime_nttime;
 109         krb5_principal client_principal_pac = NULL;
 110         int i;
 111
 112         struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
 113         struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
 114         struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
 115         struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
 116         struct PAC_LOGON_NAME *logon_name = NULL;
 117         struct PAC_LOGON_INFO *logon_info = NULL;
 118         struct PAC_DATA *pac_data = NULL;
 119         struct PAC_DATA_RAW *pac_data_raw = NULL;
 120
 121         DATA_BLOB *srv_sig_blob = NULL;
 122         DATA_BLOB *kdc_sig_blob = NULL;
 123
 124         bool bool_ret;
 125
 126         TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
 127         if (!tmp_ctx) {
 128                 return NT_STATUS_NO_MEMORY;
 129         }
 130
 131         if (pac_data_out) {
 132                 *pac_data_out = NULL;
 133         }
 134
 135         pac_data = talloc(tmp_ctx, struct PAC_DATA);
 136         pac_data_raw = talloc(tmp_ctx, struct PAC_DATA_RAW);
 137         kdc_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 138         srv_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 139         if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
 140                 talloc_free(tmp_ctx);
 141                 return NT_STATUS_NO_MEMORY;
 142         }
 143
 144         ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
 145                        (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
 146         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 147                 status = ndr_map_error2ntstatus(ndr_err);
 148                 DEBUG(0,("can't parse the PAC: %s\n",
 149                         nt_errstr(status)));
 150                 talloc_free(tmp_ctx);
 151                 return status;
 152         }
 153
 154         if (pac_data->num_buffers < 4) {
 155                 /* we need logon_ingo, service_key and kdc_key */
 156                 DEBUG(0,("less than 4 PAC buffers\n"));
 157                 talloc_free(tmp_ctx);
 158                 return NT_STATUS_INVALID_PARAMETER;
 159         }
 160
 161         ndr_err = ndr_pull_struct_blob(
 162                                 &pac_data_blob, pac_data_raw, pac_data_raw,
 163                                 (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
 164         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 165                 status = ndr_map_error2ntstatus(ndr_err);
 166                 DEBUG(0,("can't parse the PAC: %s\n",
 167                         nt_errstr(status)));
 168                 talloc_free(tmp_ctx);
 169                 return status;
 170         }
 171
 172         if (pac_data_raw->num_buffers < 4) {
 173                 /* we need logon_ingo, service_key and kdc_key */
 174                 DEBUG(0,("less than 4 PAC buffers\n"));
 175                 talloc_free(tmp_ctx);
 176                 return NT_STATUS_INVALID_PARAMETER;
 177         }
 178
 179         if (pac_data->num_buffers != pac_data_raw->num_buffers) {
 180                 /* we need logon_ingo, service_key and kdc_key */
 181                 DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
 182                           "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
 183                           pac_data_raw->num_buffers));
 184                 talloc_free(tmp_ctx);
 185                 return NT_STATUS_INVALID_PARAMETER;
 186         }
 187
 188         for (i=0; i < pac_data->num_buffers; i++) {
 189                 struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
 190                 struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
 191
 192                 if (data_buf->type != raw_buf->type) {
 193                         DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
 194                                   "%d while PAC_DATA_RAW has %d\n", i,
 195                                   data_buf->type, raw_buf->type));
 196                         talloc_free(tmp_ctx);
 197                         return NT_STATUS_INVALID_PARAMETER;
 198                 }
 199                 switch (data_buf->type) {
 200                 case PAC_TYPE_LOGON_INFO:
 201                         if (!data_buf->info) {
 202                                 break;
 203                         }
 204                         logon_info = data_buf->info->logon_info.info;
 205                         break;
 206                 case PAC_TYPE_SRV_CHECKSUM:
 207                         if (!data_buf->info) {
 208                                 break;
 209                         }
 210                         srv_sig_ptr = &data_buf->info->srv_cksum;
 211                         srv_sig_blob = &raw_buf->info->remaining;
 212                         break;
 213                 case PAC_TYPE_KDC_CHECKSUM:
 214                         if (!data_buf->info) {
 215                                 break;
 216                         }
 217                         kdc_sig_ptr = &data_buf->info->kdc_cksum;
 218                         kdc_sig_blob = &raw_buf->info->remaining;
 219                         break;
 220                 case PAC_TYPE_LOGON_NAME:
 221                         logon_name = &data_buf->info->logon_name;
 222                         break;
 223                 default:
 224                         break;
 225                 }
 226         }
 227
 228         if (!logon_info) {
 229                 DEBUG(0,("PAC no logon_info\n"));
 230                 talloc_free(tmp_ctx);
 231                 return NT_STATUS_INVALID_PARAMETER;
 232         }
 233
 234         if (!logon_name) {
 235                 DEBUG(0,("PAC no logon_name\n"));
 236                 talloc_free(tmp_ctx);
 237                 return NT_STATUS_INVALID_PARAMETER;
 238         }
 239
 240         if (!srv_sig_ptr || !srv_sig_blob) {
 241                 DEBUG(0,("PAC no srv_key\n"));
 242                 talloc_free(tmp_ctx);
 243                 return NT_STATUS_INVALID_PARAMETER;
 244         }
 245
 246         if (!kdc_sig_ptr || !kdc_sig_blob) {
 247                 DEBUG(0,("PAC no kdc_key\n"));
 248                 talloc_free(tmp_ctx);
 249                 return NT_STATUS_INVALID_PARAMETER;
 250         }
 251
 252         /* Find and zero out the signatures,
 253          * as required by the signing algorithm */
 254
 255         /* We find the data blobs above,
 256          * now we parse them to get at the exact portion we should zero */
 257         ndr_err = ndr_pull_struct_blob(
 258                         kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
 259                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 260         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 261                 status = ndr_map_error2ntstatus(ndr_err);
 262                 DEBUG(0,("can't parse the KDC signature: %s\n",
 263                         nt_errstr(status)));
 264                 talloc_free(tmp_ctx);
 265                 return status;
 266         }
 267
 268         ndr_err = ndr_pull_struct_blob(
 269                         srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
 270                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 271         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 272                 status = ndr_map_error2ntstatus(ndr_err);
 273                 DEBUG(0,("can't parse the SRV signature: %s\n",
 274                         nt_errstr(status)));
 275                 talloc_free(tmp_ctx);
 276                 return status;
 277         }
 278
 279         /* Now zero the decoded structure */
 280         memset(kdc_sig_wipe->signature.data,
 281                 '\0', kdc_sig_wipe->signature.length);
 282         memset(srv_sig_wipe->signature.data,
 283                 '\0', srv_sig_wipe->signature.length);
 284
 285         /* and reencode, back into the same place it came from */
 286         ndr_err = ndr_push_struct_blob(
 287                         kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
 288                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 289         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 290                 status = ndr_map_error2ntstatus(ndr_err);
 291                 DEBUG(0,("can't repack the KDC signature: %s\n",
 292                         nt_errstr(status)));
 293                 talloc_free(tmp_ctx);
 294                 return status;
 295         }
 296         ndr_err = ndr_push_struct_blob(
 297                         srv_sig_blob, pac_data_raw, srv_sig_wipe,
 298                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 299         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 300                 status = ndr_map_error2ntstatus(ndr_err);
 301                 DEBUG(0,("can't repack the SRV signature: %s\n",
 302                         nt_errstr(status)));
 303                 talloc_free(tmp_ctx);
 304                 return status;
 305         }
 306
 307         /* push out the whole structure, but now with zero'ed signatures */
 308         ndr_err = ndr_push_struct_blob(
 309                         &modified_pac_blob, pac_data_raw, pac_data_raw,
 310                         (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
 311         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 312                 status = ndr_map_error2ntstatus(ndr_err);
 313                 DEBUG(0,("can't repack the RAW PAC: %s\n",
 314                         nt_errstr(status)));
 315                 talloc_free(tmp_ctx);
 316                 return status;
 317         }
 318
 319         if (service_keyblock) {
 320                 /* verify by service_key */
 321                 ret = check_pac_checksum(modified_pac_blob, srv_sig_ptr,
 322                                          context,
 323                                          service_keyblock);
 324                 if (ret) {
 325                         DEBUG(1, ("PAC Decode: Failed to verify the service "
 326                                   "signature: %s\n", error_message(ret)));
 327                         return NT_STATUS_ACCESS_DENIED;
 328                 }
 329
 330                 if (krbtgt_keyblock) {
 331                         /* verify the service key checksum by krbtgt_key */
 332                         ret = check_pac_checksum(srv_sig_ptr->signature, kdc_sig_ptr,
 333                                                  context, krbtgt_keyblock);
 334                         if (ret) {
 335                                 DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
 336                                           smb_get_krb5_error_message(context, ret, tmp_ctx)));
 337                                 talloc_free(tmp_ctx);
 338                                 return NT_STATUS_ACCESS_DENIED;
 339                         }
 340                 }
 341         }
 342
 343         if (tgs_authtime) {
 344                 /* Convert to NT time, so as not to loose accuracy in comparison */
 345                 unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
 346
 347                 if (tgs_authtime_nttime != logon_name->logon_time) {
 348                         DEBUG(2, ("PAC Decode: "
 349                                   "Logon time mismatch between ticket and PAC!\n"));
 350                         DEBUG(2, ("PAC Decode: PAC: %s\n",
 351                                   nt_time_string(tmp_ctx, logon_name->logon_time)));
 352                         DEBUG(2, ("PAC Decode: Ticket: %s\n",
 353                                   nt_time_string(tmp_ctx, tgs_authtime_nttime)));
 354                         talloc_free(tmp_ctx);
 355                         return NT_STATUS_ACCESS_DENIED;
 356                 }
 357         }
 358
 359         if (client_principal) {
 360                 ret = smb_krb5_parse_name_norealm(context,
 361                                                   logon_name->account_name,
 362                                                   &client_principal_pac);
 363                 if (ret) {
 364                         DEBUG(2, ("Could not parse name from PAC: [%s]:%s\n",
 365                                   logon_name->account_name, error_message(ret)));
 366                         talloc_free(tmp_ctx);
 367                         return NT_STATUS_INVALID_PARAMETER;
 368                 }
 369
 370                 bool_ret = smb_krb5_principal_compare_any_realm(context,
 371                                                                 client_principal,
 372                                                                 client_principal_pac);
 373
 374                 krb5_free_principal(context, client_principal_pac);
 375
 376                 if (!bool_ret) {
 377                         DEBUG(2, ("Name in PAC [%s] does not match principal name "
 378                                   "in ticket\n", logon_name->account_name));
 379                         talloc_free(tmp_ctx);
 380                         return NT_STATUS_ACCESS_DENIED;
 381                 }
 382         }
 383
 384         DEBUG(3,("Found account name from PAC: %s [%s]\n",
 385                  logon_info->info3.base.account_name.string,
 386                  logon_info->info3.base.full_name.string));
 387
 388         DEBUG(10,("Successfully validated Kerberos PAC\n"));
 389
 390         if (DEBUGLEVEL >= 10) {
 391                 const char *s;
 392                 s = NDR_PRINT_STRUCT_STRING(tmp_ctx, PAC_DATA, pac_data);
 393                 if (s) {
 394                         DEBUGADD(10,("%s\n", s));
 395                 }
 396         }
 397
 398         if (pac_data_out) {
 399                 *pac_data_out = talloc_steal(mem_ctx, pac_data);
 400         }
 401
 402         return NT_STATUS_OK;
 403 }
 404
 405 #endif