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(TALLOC_CTX *mem_ctx,
  32                                           DATA_BLOB pac_data,
  33                                           struct PAC_SIGNATURE_DATA *sig,
  34                                           krb5_context context,
  35                                           const krb5_keyblock *keyblock)
  36 {
  37         krb5_error_code ret;
  38         krb5_checksum cksum;
  39         krb5_keyusage usage = 0;
  40
  41         smb_krb5_checksum_from_pac_sig(&cksum, sig);
  42
  43 #ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
  44         usage = KRB5_KU_OTHER_CKSUM;
  45 #elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
  46         usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
  47 #else
  48 #error UNKNOWN_KRB5_KEYUSAGE
  49 #endif
  50
  51         ret = smb_krb5_verify_checksum(context,
  52                                        keyblock,
  53                                        usage,
  54                                        &cksum,
  55                                        pac_data.data,
  56                                        pac_data.length);
  57
  58         if (ret) {
  59                 DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
  60                         error_message(ret), ret));
  61                 return ret;
  62         }
  63
  64         return ret;
  65 }
  66
  67 /**
  68 * @brief Decode a blob containing a NDR envoded PAC structure
  69 *
  70 * @param mem_ctx          - The memory context
  71 * @param pac_data_blob    - The data blob containing the NDR encoded data
  72 * @param context          - The Kerberos Context
  73 * @param service_keyblock - The Service Key used to verify the checksum
  74 * @param client_principal - The client principal
  75 * @param tgs_authtime     - The ticket timestamp
  76 * @param pac_data_out     - [out] The decoded PAC
  77 *
  78 * @return - A NTSTATUS error code
  79 */
  80 NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx_out,
  81                              DATA_BLOB pac_data_blob,
  82                              krb5_context context,
  83                              const krb5_keyblock *krbtgt_keyblock,
  84                              const krb5_keyblock *service_keyblock,
  85                              krb5_const_principal client_principal,
  86                              time_t tgs_authtime,
  87                              struct PAC_DATA **pac_data_out)
  88 {
  89         NTSTATUS status;
  90         enum ndr_err_code ndr_err;
  91         krb5_error_code ret;
  92         DATA_BLOB modified_pac_blob;
  93
  94         NTTIME tgs_authtime_nttime;
  95         krb5_principal client_principal_pac = NULL;
  96         int i;
  97
  98         struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
  99         struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
 100         struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
 101         struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
 102         struct PAC_LOGON_NAME *logon_name = NULL;
 103         struct PAC_LOGON_INFO *logon_info = NULL;
 104         struct PAC_DATA *pac_data = NULL;
 105         struct PAC_DATA_RAW *pac_data_raw = NULL;
 106
 107         DATA_BLOB *srv_sig_blob = NULL;
 108         DATA_BLOB *kdc_sig_blob = NULL;
 109
 110         bool bool_ret;
 111
 112         TALLOC_CTX *mem_ctx = talloc_new(mem_ctx_out);
 113         if (!mem_ctx) {
 114                 return NT_STATUS_NO_MEMORY;
 115         }
 116
 117         if (pac_data_out) {
 118                 *pac_data_out = NULL;
 119         }
 120
 121         pac_data = talloc(mem_ctx, struct PAC_DATA);
 122         pac_data_raw = talloc(mem_ctx, struct PAC_DATA_RAW);
 123         kdc_sig_wipe = talloc(mem_ctx, struct PAC_SIGNATURE_DATA);
 124         srv_sig_wipe = talloc(mem_ctx, struct PAC_SIGNATURE_DATA);
 125         if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
 126                 talloc_free(mem_ctx);
 127                 return NT_STATUS_NO_MEMORY;
 128         }
 129
 130         ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
 131                        (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
 132         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 133                 status = ndr_map_error2ntstatus(ndr_err);
 134                 DEBUG(0,("can't parse the PAC: %s\n",
 135                         nt_errstr(status)));
 136                 talloc_free(mem_ctx);
 137                 return status;
 138         }
 139
 140         if (pac_data->num_buffers < 4) {
 141                 /* we need logon_ingo, service_key and kdc_key */
 142                 DEBUG(0,("less than 4 PAC buffers\n"));
 143                 talloc_free(mem_ctx);
 144                 return NT_STATUS_INVALID_PARAMETER;
 145         }
 146
 147         ndr_err = ndr_pull_struct_blob(
 148                                 &pac_data_blob, pac_data_raw, pac_data_raw,
 149                                 (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
 150         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 151                 status = ndr_map_error2ntstatus(ndr_err);
 152                 DEBUG(0,("can't parse the PAC: %s\n",
 153                         nt_errstr(status)));
 154                 talloc_free(mem_ctx);
 155                 return status;
 156         }
 157
 158         if (pac_data_raw->num_buffers < 4) {
 159                 /* we need logon_ingo, service_key and kdc_key */
 160                 DEBUG(0,("less than 4 PAC buffers\n"));
 161                 talloc_free(mem_ctx);
 162                 return NT_STATUS_INVALID_PARAMETER;
 163         }
 164
 165         if (pac_data->num_buffers != pac_data_raw->num_buffers) {
 166                 /* we need logon_ingo, service_key and kdc_key */
 167                 DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
 168                           "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
 169                           pac_data_raw->num_buffers));
 170                 talloc_free(mem_ctx);
 171                 return NT_STATUS_INVALID_PARAMETER;
 172         }
 173
 174         for (i=0; i < pac_data->num_buffers; i++) {
 175                 struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
 176                 struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
 177
 178                 if (data_buf->type != raw_buf->type) {
 179                         DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
 180                                   "%d while PAC_DATA_RAW has %d\n", i,
 181                                   data_buf->type, raw_buf->type));
 182                         talloc_free(mem_ctx);
 183                         return NT_STATUS_INVALID_PARAMETER;
 184                 }
 185                 switch (data_buf->type) {
 186                 case PAC_TYPE_LOGON_INFO:
 187                         if (!data_buf->info) {
 188                                 break;
 189                         }
 190                         logon_info = data_buf->info->logon_info.info;
 191                         break;
 192                 case PAC_TYPE_SRV_CHECKSUM:
 193                         if (!data_buf->info) {
 194                                 break;
 195                         }
 196                         srv_sig_ptr = &data_buf->info->srv_cksum;
 197                         srv_sig_blob = &raw_buf->info->remaining;
 198                         break;
 199                 case PAC_TYPE_KDC_CHECKSUM:
 200                         if (!data_buf->info) {
 201                                 break;
 202                         }
 203                         kdc_sig_ptr = &data_buf->info->kdc_cksum;
 204                         kdc_sig_blob = &raw_buf->info->remaining;
 205                         break;
 206                 case PAC_TYPE_LOGON_NAME:
 207                         logon_name = &data_buf->info->logon_name;
 208                         break;
 209                 default:
 210                         break;
 211                 }
 212         }
 213
 214         if (!logon_info) {
 215                 DEBUG(0,("PAC no logon_info\n"));
 216                 talloc_free(mem_ctx);
 217                 return NT_STATUS_INVALID_PARAMETER;
 218         }
 219
 220         if (!logon_name) {
 221                 DEBUG(0,("PAC no logon_name\n"));
 222                 talloc_free(mem_ctx);
 223                 return NT_STATUS_INVALID_PARAMETER;
 224         }
 225
 226         if (!srv_sig_ptr || !srv_sig_blob) {
 227                 DEBUG(0,("PAC no srv_key\n"));
 228                 talloc_free(mem_ctx);
 229                 return NT_STATUS_INVALID_PARAMETER;
 230         }
 231
 232         if (!kdc_sig_ptr || !kdc_sig_blob) {
 233                 DEBUG(0,("PAC no kdc_key\n"));
 234                 talloc_free(mem_ctx);
 235                 return NT_STATUS_INVALID_PARAMETER;
 236         }
 237
 238         /* Find and zero out the signatures,
 239          * as required by the signing algorithm */
 240
 241         /* We find the data blobs above,
 242          * now we parse them to get at the exact portion we should zero */
 243         ndr_err = ndr_pull_struct_blob(
 244                         kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
 245                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 246         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 247                 status = ndr_map_error2ntstatus(ndr_err);
 248                 DEBUG(0,("can't parse the KDC signature: %s\n",
 249                         nt_errstr(status)));
 250                 talloc_free(mem_ctx);
 251                 return status;
 252         }
 253
 254         ndr_err = ndr_pull_struct_blob(
 255                         srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
 256                         (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
 257         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 258                 status = ndr_map_error2ntstatus(ndr_err);
 259                 DEBUG(0,("can't parse the SRV signature: %s\n",
 260                         nt_errstr(status)));
 261                 talloc_free(mem_ctx);
 262                 return status;
 263         }
 264
 265         /* Now zero the decoded structure */
 266         memset(kdc_sig_wipe->signature.data,
 267                 '\0', kdc_sig_wipe->signature.length);
 268         memset(srv_sig_wipe->signature.data,
 269                 '\0', srv_sig_wipe->signature.length);
 270
 271         /* and reencode, back into the same place it came from */
 272         ndr_err = ndr_push_struct_blob(
 273                         kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
 274                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 275         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 276                 status = ndr_map_error2ntstatus(ndr_err);
 277                 DEBUG(0,("can't repack the KDC signature: %s\n",
 278                         nt_errstr(status)));
 279                 talloc_free(mem_ctx);
 280                 return status;
 281         }
 282         ndr_err = ndr_push_struct_blob(
 283                         srv_sig_blob, pac_data_raw, srv_sig_wipe,
 284                         (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
 285         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 286                 status = ndr_map_error2ntstatus(ndr_err);
 287                 DEBUG(0,("can't repack the SRV signature: %s\n",
 288                         nt_errstr(status)));
 289                 talloc_free(mem_ctx);
 290                 return status;
 291         }
 292
 293         /* push out the whole structure, but now with zero'ed signatures */
 294         ndr_err = ndr_push_struct_blob(
 295                         &modified_pac_blob, pac_data_raw, pac_data_raw,
 296                         (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
 297         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 298                 status = ndr_map_error2ntstatus(ndr_err);
 299                 DEBUG(0,("can't repack the RAW PAC: %s\n",
 300                         nt_errstr(status)));
 301                 talloc_free(mem_ctx);
 302                 return status;
 303         }
 304
 305         if (service_keyblock) {
 306                 /* verify by service_key */
 307                 ret = check_pac_checksum(mem_ctx,
 308                                          modified_pac_blob, srv_sig_ptr,
 309                                          context,
 310                                          service_keyblock);
 311                 if (ret) {
 312                         DEBUG(1, ("PAC Decode: Failed to verify the service "
 313                                   "signature: %s\n", error_message(ret)));
 314                         return NT_STATUS_ACCESS_DENIED;
 315                 }
 316
 317                 if (krbtgt_keyblock) {
 318                         /* verify the service key checksum by krbtgt_key */
 319                         ret = check_pac_checksum(mem_ctx,
 320                                                  srv_sig_ptr->signature, kdc_sig_ptr,
 321                                                  context, krbtgt_keyblock);
 322                         if (ret) {
 323                                 DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
 324                                           smb_get_krb5_error_message(context, ret, mem_ctx)));
 325                                 talloc_free(mem_ctx);
 326                                 return NT_STATUS_ACCESS_DENIED;
 327                         }
 328                 }
 329         }
 330
 331         if (tgs_authtime) {
 332                 /* Convert to NT time, so as not to loose accuracy in comparison */
 333                 unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
 334
 335                 if (tgs_authtime_nttime != logon_name->logon_time) {
 336                         DEBUG(2, ("PAC Decode: "
 337                                   "Logon time mismatch between ticket and PAC!\n"));
 338                         DEBUG(2, ("PAC Decode: PAC: %s\n",
 339                                   nt_time_string(mem_ctx, logon_name->logon_time)));
 340                         DEBUG(2, ("PAC Decode: Ticket: %s\n",
 341                                   nt_time_string(mem_ctx, tgs_authtime_nttime)));
 342                         talloc_free(mem_ctx);
 343                         return NT_STATUS_ACCESS_DENIED;
 344                 }
 345         }
 346
 347         if (client_principal) {
 348                 ret = smb_krb5_parse_name_norealm(context,
 349                                                   logon_name->account_name,
 350                                                   &client_principal_pac);
 351                 if (ret) {
 352                         DEBUG(2, ("Could not parse name from PAC: [%s]:%s\n",
 353                                   logon_name->account_name, error_message(ret)));
 354                         talloc_free(mem_ctx);
 355                         return NT_STATUS_INVALID_PARAMETER;
 356                 }
 357
 358                 bool_ret = smb_krb5_principal_compare_any_realm(context,
 359                                                                 client_principal,
 360                                                                 client_principal_pac);
 361
 362                 krb5_free_principal(context, client_principal_pac);
 363
 364                 if (!bool_ret) {
 365                         DEBUG(2, ("Name in PAC [%s] does not match principal name "
 366                                   "in ticket\n", logon_name->account_name));
 367                         talloc_free(mem_ctx);
 368                         return NT_STATUS_ACCESS_DENIED;
 369                 }
 370         }
 371
 372         DEBUG(3,("Found account name from PAC: %s [%s]\n",
 373                  logon_info->info3.base.account_name.string,
 374                  logon_info->info3.base.full_name.string));
 375
 376         DEBUG(10,("Successfully validated Kerberos PAC\n"));
 377
 378         if (DEBUGLEVEL >= 10) {
 379                 const char *s;
 380                 s = NDR_PRINT_STRUCT_STRING(mem_ctx, PAC_DATA, pac_data);
 381                 if (s) {
 382                         DEBUGADD(10,("%s\n", s));
 383                 }
 384         }
 385
 386         if (pac_data_out) {
 387                 *pac_data_out = talloc_steal(mem_ctx_out, pac_data);
 388         }
 389
 390         return NT_STATUS_OK;
 391 }
 392
 393 #endif