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 "libcli/auth/krb5_wrap.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
  40         smb_krb5_checksum_from_pac_sig(&cksum, sig);
  41
  42 #ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
  43         usage = KRB5_KU_OTHER_CKSUM;
  44 #elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
  45         usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
  46 #else
  47 #error UNKNOWN_KRB5_KEYUSAGE
  48 #endif
  49
  50         ret = smb_krb5_verify_checksum(context,
  51                                        keyblock,
  52                                        usage,
  53                                        &cksum,
  54                                        pac_data.data,
  55                                        pac_data.length);
  56
  57         if (ret) {
  58                 DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
  59                         error_message(ret), ret));
  60                 return ret;
  61         }
  62
  63         return ret;
  64 }
  65
  66 /**
  67 * @brief Decode a blob containing a NDR envoded PAC structure
  68 *
  69 * @param mem_ctx          - The memory context
  70 * @param pac_data_blob    - The data blob containing the NDR encoded data
  71 * @param context          - The Kerberos Context
  72 * @param service_keyblock - The Service Key used to verify the checksum
  73 * @param client_principal - The client principal
  74 * @param tgs_authtime     - The ticket timestamp
  75 * @param pac_data_out     - [out] The decoded PAC
  76 *
  77 * @return - A NTSTATUS error code
  78 */
  79 NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
  80                              DATA_BLOB pac_data_blob,
  81                              krb5_context context,
  82                              const krb5_keyblock *krbtgt_keyblock,
  83                              const krb5_keyblock *service_keyblock,
  84                              krb5_const_principal client_principal,
  85                              time_t tgs_authtime,
  86                              struct PAC_DATA **pac_data_out)
  87 {
  88         NTSTATUS status;
  89         enum ndr_err_code ndr_err;
  90         krb5_error_code ret;
  91         DATA_BLOB modified_pac_blob;
  92
  93         NTTIME tgs_authtime_nttime;
  94         krb5_principal client_principal_pac = NULL;
  95         int i;
  96
  97         struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
  98         struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
  99         struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
 100         struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
 101         struct PAC_LOGON_NAME *logon_name = NULL;
 102         struct PAC_LOGON_INFO *logon_info = NULL;
 103         struct PAC_DATA *pac_data = NULL;
 104         struct PAC_DATA_RAW *pac_data_raw = NULL;
 105
 106         DATA_BLOB *srv_sig_blob = NULL;
 107         DATA_BLOB *kdc_sig_blob = NULL;
 108
 109         bool bool_ret;
 110
 111         TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
 112         if (!tmp_ctx) {
 113                 return NT_STATUS_NO_MEMORY;
 114         }
 115
 116         if (pac_data_out) {
 117                 *pac_data_out = NULL;
 118         }
 119
 120         pac_data = talloc(tmp_ctx, struct PAC_DATA);
 121         pac_data_raw = talloc(tmp_ctx, struct PAC_DATA_RAW);
 122         kdc_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 123         srv_sig_wipe = talloc(tmp_ctx, struct PAC_SIGNATURE_DATA);
 124         if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
 125                 talloc_free(tmp_ctx);
 126                 return NT_STATUS_NO_MEMORY;
 127         }
 128
 129         ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
 130                        (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
 131         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 132                 status = ndr_map_error2ntstatus(ndr_err);
 133                 DEBUG(0,("can't parse the PAC: %s\n",
 134                         nt_errstr(status)));
 135                 talloc_free(tmp_ctx);
 136                 return status;
 137         }
 138
 139         if (pac_data->num_buffers < 4) {
 140                 /* we need logon_ingo, service_key and kdc_key */
 141                 DEBUG(0,("less than 4 PAC buffers\n"));
 142                 talloc_free(tmp_ctx);
 143                 return NT_STATUS_INVALID_PARAMETER;
 144         }
 145
 146         ndr_err = ndr_pull_struct_blob(
 147                                 &pac_data_blob, pac_data_raw, pac_data_raw,
 148                                 (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
 149         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 150                 status = ndr_map_error2ntstatus(ndr_err);
 151                 DEBUG(0,("can't parse the PAC: %s\n",
 152                         nt_errstr(status)));
 153                 talloc_free(tmp_ctx);
 154                 return status;
 155         }
 156
 157         if (pac_data_raw->num_buffers < 4) {
 158                 /* we need logon_ingo, service_key and kdc_key */
 159                 DEBUG(0,("less than 4 PAC buffers\n"));
 160                 talloc_free(tmp_ctx);
 161                 return NT_STATUS_INVALID_PARAMETER;
 162         }
 163
 164         if (pac_data->num_buffers != pac_data_raw->num_buffers) {
 165                 /* we need logon_ingo, service_key and kdc_key */
 166                 DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
 167                           "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
 168                           pac_data_raw->num_buffers));
 169                 talloc_free(tmp_ctx);
 170                 return NT_STATUS_INVALID_PARAMETER;
 171         }
 172
 173         for (i=0; i < pac_data->num_buffers; i++) {
 174                 struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
 175                 struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
 176
 177                 if (data_buf->type != raw_buf->type) {
 178                         DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
 179                                   "%d while PAC_DATA_RAW has %d\n", i,
 180                                   data_buf->type, raw_buf->type));
 181                         talloc_free(tmp_ctx);
 182                         return NT_STATUS_INVALID_PARAMETER;
 183                 }
 184                 switch (data_buf->type) {
 185                 case PAC_TYPE_LOGON_INFO:
 186                         if (!data_buf->info) {
 187                                 break;
 188                         }
 189                         logon_info = data_buf->info->logon_info.info;
 190                         break;
 191                 case PAC_TYPE_SRV_CHECKSUM:
 192                         if (!data_buf->info) {
 193                                 break;
 194                         }
 195                         srv_sig_ptr = &data_buf->info->srv_cksum;
 196                         srv_sig_blob = &raw_buf->info->remaining;
 197                         break;
 198                 case PAC_TYPE_KDC_CHECKSUM:
 199                         if (!data_buf->info) {
 200                                 break;
 201                         }
 202                         kdc_sig_ptr = &data_buf->info->kdc_cksum;
 203                         kdc_sig_blob = &raw_buf->info->remaining;
 204                         break;
 205                 case PAC_TYPE_LOGON_NAME:
 206                         logon_name = &data_buf->info->logon_name;
 207                         break;
 208                 default:
 209                         break;
 210                 }
 211         }
 212
 213         if (!logon_info) {
 214                 DEBUG(0,("PAC no logon_info\n"));
 215                 talloc_free(tmp_ctx);
 216                 return NT_STATUS_INVALID_PARAMETER;
 217         }
 218
 219         if (!logon_name) {
 220                 DEBUG(0,("PAC no logon_name\n"));
 221                 talloc_free(tmp_ctx);
 222                 return NT_STATUS_INVALID_PARAMETER;
 223         }
 224
 225         if (!srv_sig_ptr || !srv_sig_blob) {
 226                 DEBUG(0,("PAC no srv_key\n"));
 227                 talloc_free(tmp_ctx);
 228                 return NT_STATUS_INVALID_PARAMETER;
 229         }
 230
 231         if (!kdc_sig_ptr || !kdc_sig_blob) {
 232                 DEBUG(0,("PAC no kdc_key\n"));
 233                 talloc_free(tmp_ctx);
 234                 return NT_STATUS_INVALID_PARAMETER;
 235         }
 236
 237         /* Find and zero out the signatures,
 238          * as required by the signing algorithm */
 239
 240         /* We find the data blobs above,
 241          * now we parse them to get at the exact portion we should zero */
 242         ndr_err = ndr_pull_struct_blob(
 243                         kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
 244                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 245         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 246                 status = ndr_map_error2ntstatus(ndr_err);
 247                 DEBUG(0,("can't parse the KDC signature: %s\n",
 248                         nt_errstr(status)));
 249                 talloc_free(tmp_ctx);
 250                 return status;
 251         }
 252
 253         ndr_err = ndr_pull_struct_blob(
 254                         srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
 255                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 256         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 257                 status = ndr_map_error2ntstatus(ndr_err);
 258                 DEBUG(0,("can't parse the SRV signature: %s\n",
 259                         nt_errstr(status)));
 260                 talloc_free(tmp_ctx);
 261                 return status;
 262         }
 263
 264         /* Now zero the decoded structure */
 265         memset(kdc_sig_wipe->signature.data,
 266                 '\0', kdc_sig_wipe->signature.length);
 267         memset(srv_sig_wipe->signature.data,
 268                 '\0', srv_sig_wipe->signature.length);
 269
 270         /* and reencode, back into the same place it came from */
 271         ndr_err = ndr_push_struct_blob(
 272                         kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
 273                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 274         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 275                 status = ndr_map_error2ntstatus(ndr_err);
 276                 DEBUG(0,("can't repack the KDC signature: %s\n",
 277                         nt_errstr(status)));
 278                 talloc_free(tmp_ctx);
 279                 return status;
 280         }
 281         ndr_err = ndr_push_struct_blob(
 282                         srv_sig_blob, pac_data_raw, srv_sig_wipe,
 283                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 284         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 285                 status = ndr_map_error2ntstatus(ndr_err);
 286                 DEBUG(0,("can't repack the SRV signature: %s\n",
 287                         nt_errstr(status)));
 288                 talloc_free(tmp_ctx);
 289                 return status;
 290         }
 291
 292         /* push out the whole structure, but now with zero'ed signatures */
 293         ndr_err = ndr_push_struct_blob(
 294                         &modified_pac_blob, pac_data_raw, pac_data_raw,
 295                         (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
 296         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 297                 status = ndr_map_error2ntstatus(ndr_err);
 298                 DEBUG(0,("can't repack the RAW PAC: %s\n",
 299                         nt_errstr(status)));
 300                 talloc_free(tmp_ctx);
 301                 return status;
 302         }
 303
 304         if (service_keyblock) {
 305                 /* verify by service_key */
 306                 ret = check_pac_checksum(modified_pac_blob, srv_sig_ptr,
 307                                          context,
 308                                          service_keyblock);
 309                 if (ret) {
 310                         DEBUG(1, ("PAC Decode: Failed to verify the service "
 311                                   "signature: %s\n", error_message(ret)));
 312                         return NT_STATUS_ACCESS_DENIED;
 313                 }
 314
 315                 if (krbtgt_keyblock) {
 316                         /* verify the service key checksum by krbtgt_key */
 317                         ret = check_pac_checksum(srv_sig_ptr->signature, kdc_sig_ptr,
 318                                                  context, krbtgt_keyblock);
 319                         if (ret) {
 320                                 DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
 321                                           smb_get_krb5_error_message(context, ret, tmp_ctx)));
 322                                 talloc_free(tmp_ctx);
 323                                 return NT_STATUS_ACCESS_DENIED;
 324                         }
 325                 }
 326         }
 327
 328         if (tgs_authtime) {
 329                 /* Convert to NT time, so as not to loose accuracy in comparison */
 330                 unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
 331
 332                 if (tgs_authtime_nttime != logon_name->logon_time) {
 333                         DEBUG(2, ("PAC Decode: "
 334                                   "Logon time mismatch between ticket and PAC!\n"));
 335                         DEBUG(2, ("PAC Decode: PAC: %s\n",
 336                                   nt_time_string(tmp_ctx, logon_name->logon_time)));
 337                         DEBUG(2, ("PAC Decode: Ticket: %s\n",
 338                                   nt_time_string(tmp_ctx, tgs_authtime_nttime)));
 339                         talloc_free(tmp_ctx);
 340                         return NT_STATUS_ACCESS_DENIED;
 341                 }
 342         }
 343
 344         if (client_principal) {
 345                 ret = smb_krb5_parse_name_norealm(context,
 346                                                   logon_name->account_name,
 347                                                   &client_principal_pac);
 348                 if (ret) {
 349                         DEBUG(2, ("Could not parse name from PAC: [%s]:%s\n",
 350                                   logon_name->account_name, error_message(ret)));
 351                         talloc_free(tmp_ctx);
 352                         return NT_STATUS_INVALID_PARAMETER;
 353                 }
 354
 355                 bool_ret = smb_krb5_principal_compare_any_realm(context,
 356                                                                 client_principal,
 357                                                                 client_principal_pac);
 358
 359                 krb5_free_principal(context, client_principal_pac);
 360
 361                 if (!bool_ret) {
 362                         DEBUG(2, ("Name in PAC [%s] does not match principal name "
 363                                   "in ticket\n", logon_name->account_name));
 364                         talloc_free(tmp_ctx);
 365                         return NT_STATUS_ACCESS_DENIED;
 366                 }
 367         }
 368
 369         DEBUG(3,("Found account name from PAC: %s [%s]\n",
 370                  logon_info->info3.base.account_name.string,
 371                  logon_info->info3.base.full_name.string));
 372
 373         DEBUG(10,("Successfully validated Kerberos PAC\n"));
 374
 375         if (DEBUGLEVEL >= 10) {
 376                 const char *s;
 377                 s = NDR_PRINT_STRUCT_STRING(tmp_ctx, PAC_DATA, pac_data);
 378                 if (s) {
 379                         DEBUGADD(10,("%s\n", s));
 380                 }
 381         }
 382
 383         if (pac_data_out) {
 384                 *pac_data_out = talloc_steal(mem_ctx, pac_data);
 385         }
 386
 387         return NT_STATUS_OK;
 388 }
 389
 390 #endif