libcli/drsuapi/repl_decrypt.c

   1 /*
   2    Unix SMB/CIFS mplementation.
   3    Helper functions for applying replicated objects
   4
   5    Copyright (C) Stefan Metzmacher <metze@samba.org> 2007
   6    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2009
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20
  21 */
  22
  23 #include "includes.h"
  24 #include "../lib/util/dlinklist.h"
  25 #include "librpc/gen_ndr/ndr_misc.h"
  26 #include "librpc/gen_ndr/ndr_drsuapi.h"
  27 #include "librpc/gen_ndr/ndr_drsblobs.h"
  28 #include "../lib/crypto/crypto.h"
  29 #include "../libcli/drsuapi/drsuapi.h"
  30 #include "libcli/auth/libcli_auth.h"
  31
  32 WERROR drsuapi_decrypt_attribute_value(TALLOC_CTX *mem_ctx,
  33                                        const DATA_BLOB *gensec_skey,
  34                                        bool rid_crypt,
  35                                        uint32_t rid,
  36                                        DATA_BLOB *in,
  37                                        DATA_BLOB *out)
  38 {
  39         DATA_BLOB confounder;
  40         DATA_BLOB enc_buffer;
  41
  42         struct MD5Context md5;
  43         uint8_t _enc_key[16];
  44         DATA_BLOB enc_key;
  45
  46         DATA_BLOB dec_buffer;
  47
  48         uint32_t crc32_given;
  49         uint32_t crc32_calc;
  50         DATA_BLOB checked_buffer;
  51
  52         DATA_BLOB plain_buffer;
  53
  54         /*
  55          * users with rid == 0 should not exist
  56          */
  57         if (rid_crypt && rid == 0) {
  58                 return WERR_DS_DRA_INVALID_PARAMETER;
  59         }
  60
  61         /*
  62          * the first 16 bytes at the beginning are the confounder
  63          * followed by the 4 byte crc32 checksum
  64          */
  65         if (in->length < 20) {
  66                 return WERR_DS_DRA_INVALID_PARAMETER;
  67         }
  68         confounder = data_blob_const(in->data, 16);
  69         enc_buffer = data_blob_const(in->data + 16, in->length - 16);
  70
  71         /*
  72          * build the encryption key md5 over the session key followed
  73          * by the confounder
  74          *
  75          * here the gensec session key is used and
  76          * not the dcerpc ncacn_ip_tcp "SystemLibraryDTC" key!
  77          */
  78         enc_key = data_blob_const(_enc_key, sizeof(_enc_key));
  79         MD5Init(&md5);
  80         MD5Update(&md5, gensec_skey->data, gensec_skey->length);
  81         MD5Update(&md5, confounder.data, confounder.length);
  82         MD5Final(enc_key.data, &md5);
  83
  84         /*
  85          * copy the encrypted buffer part and
  86          * decrypt it using the created encryption key using arcfour
  87          */
  88         dec_buffer = data_blob_const(enc_buffer.data, enc_buffer.length);
  89         arcfour_crypt_blob(dec_buffer.data, dec_buffer.length, &enc_key);
  90
  91         /*
  92          * the first 4 byte are the crc32 checksum
  93          * of the remaining bytes
  94          */
  95         crc32_given = IVAL(dec_buffer.data, 0);
  96         crc32_calc = crc32_calc_buffer(dec_buffer.data + 4 , dec_buffer.length - 4);
  97         checked_buffer = data_blob_const(dec_buffer.data + 4, dec_buffer.length - 4);
  98
  99         plain_buffer = data_blob_talloc(mem_ctx, checked_buffer.data, checked_buffer.length);
 100         W_ERROR_HAVE_NO_MEMORY(plain_buffer.data);
 101
 102         if (crc32_given != crc32_calc) {
 103                 return WERR_SEC_E_DECRYPT_FAILURE;
 104         }
 105         /*
 106          * The following rid_crypt obfuscation isn't session specific
 107          * and not really needed here, because we allways know the rid of the
 108          * user account.
 109          *
 110          * some attributes with this 'additional encryption' include
 111          * dBCSPwd, unicodePwd, ntPwdHistory, lmPwdHistory
 112          *
 113          * But for the rest of samba it's easier when we remove this static
 114          * obfuscation here
 115          */
 116         if (rid_crypt) {
 117                 uint32_t i, num_hashes;
 118
 119                 if ((checked_buffer.length % 16) != 0) {
 120                         return WERR_DS_DRA_INVALID_PARAMETER;
 121                 }
 122
 123                 num_hashes = plain_buffer.length / 16;
 124                 for (i = 0; i < num_hashes; i++) {
 125                         uint32_t offset = i * 16;
 126                         sam_rid_crypt(rid, checked_buffer.data + offset, plain_buffer.data + offset, 0);
 127                 }
 128         }
 129
 130         *out = plain_buffer;
 131         return WERR_OK;
 132 }
 133
 134 WERROR drsuapi_decrypt_attribute(TALLOC_CTX *mem_ctx,
 135                                  const DATA_BLOB *gensec_skey,
 136                                  uint32_t rid,
 137                                  struct drsuapi_DsReplicaAttribute *attr)
 138 {
 139         WERROR status;
 140         DATA_BLOB *enc_data;
 141         DATA_BLOB plain_data;
 142         bool rid_crypt = false;
 143
 144         if (attr->value_ctr.num_values == 0) {
 145                 return WERR_OK;
 146         }
 147
 148         switch (attr->attid) {
 149         case DRSUAPI_ATTRIBUTE_dBCSPwd:
 150         case DRSUAPI_ATTRIBUTE_unicodePwd:
 151         case DRSUAPI_ATTRIBUTE_ntPwdHistory:
 152         case DRSUAPI_ATTRIBUTE_lmPwdHistory:
 153                 rid_crypt = true;
 154                 break;
 155         case DRSUAPI_ATTRIBUTE_supplementalCredentials:
 156         case DRSUAPI_ATTRIBUTE_priorValue:
 157         case DRSUAPI_ATTRIBUTE_currentValue:
 158         case DRSUAPI_ATTRIBUTE_trustAuthOutgoing:
 159         case DRSUAPI_ATTRIBUTE_trustAuthIncoming:
 160         case DRSUAPI_ATTRIBUTE_initialAuthOutgoing:
 161         case DRSUAPI_ATTRIBUTE_initialAuthIncoming:
 162                 break;
 163         default:
 164                 return WERR_OK;
 165         }
 166
 167         if (attr->value_ctr.num_values > 1) {
 168                 return WERR_DS_DRA_INVALID_PARAMETER;
 169         }
 170
 171         if (!attr->value_ctr.values[0].blob) {
 172                 return WERR_DS_DRA_INVALID_PARAMETER;
 173         }
 174
 175         enc_data        = attr->value_ctr.values[0].blob;
 176
 177         status = drsuapi_decrypt_attribute_value(mem_ctx,
 178                                                  gensec_skey,
 179                                                  rid_crypt,
 180                                                  rid,
 181                                                  enc_data,
 182                                                  &plain_data);
 183         W_ERROR_NOT_OK_RETURN(status);
 184
 185         talloc_free(attr->value_ctr.values[0].blob->data);
 186         *attr->value_ctr.values[0].blob = plain_data;
 187
 188         return WERR_OK;
 189 }
 190
 191 static WERROR drsuapi_encrypt_attribute_value(TALLOC_CTX *mem_ctx,
 192                                               const DATA_BLOB *gensec_skey,
 193                                               bool rid_crypt,
 194                                               uint32_t rid,
 195                                               DATA_BLOB *in,
 196                                               DATA_BLOB *out)
 197 {
 198         DATA_BLOB rid_crypt_out = data_blob(NULL, 0);
 199         DATA_BLOB confounder;
 200
 201         struct MD5Context md5;
 202         uint8_t _enc_key[16];
 203         DATA_BLOB enc_key;
 204
 205         DATA_BLOB enc_buffer;
 206
 207         uint32_t crc32_calc;
 208
 209         /*
 210          * users with rid == 0 should not exist
 211          */
 212         if (rid_crypt && rid == 0) {
 213                 return WERR_DS_DRA_INVALID_PARAMETER;
 214         }
 215
 216         /*
 217          * The following rid_crypt obfuscation isn't session specific
 218          * and not really needed here, because we allways know the rid of the
 219          * user account.
 220          *
 221          * some attributes with this 'additional encryption' include
 222          * dBCSPwd, unicodePwd, ntPwdHistory, lmPwdHistory
 223          *
 224          * But for the rest of samba it's easier when we remove this static
 225          * obfuscation here
 226          */
 227         if (rid_crypt) {
 228                 uint32_t i, num_hashes;
 229                 rid_crypt_out = data_blob_talloc(mem_ctx, in->data, in->length);
 230                 W_ERROR_HAVE_NO_MEMORY(rid_crypt_out.data);
 231
 232                 if ((rid_crypt_out.length % 16) != 0) {
 233                         return WERR_DS_DRA_INVALID_PARAMETER;
 234                 }
 235
 236                 num_hashes = rid_crypt_out.length / 16;
 237                 for (i = 0; i < num_hashes; i++) {
 238                         uint32_t offset = i * 16;
 239                         sam_rid_crypt(rid, in->data + offset, rid_crypt_out.data + offset, 1);
 240                 }
 241                 in = &rid_crypt_out;
 242         }
 243
 244         /*
 245          * the first 16 bytes at the beginning are the confounder
 246          * followed by the 4 byte crc32 checksum
 247          */
 248
 249         enc_buffer = data_blob_talloc(mem_ctx, NULL, in->length+20);
 250         if (!enc_buffer.data) {
 251                 talloc_free(rid_crypt_out.data);
 252                 return WERR_NOMEM;
 253         };
 254
 255         confounder = data_blob_const(enc_buffer.data, 16);
 256         generate_random_buffer(confounder.data, confounder.length);
 257
 258         /*
 259          * build the encryption key md5 over the session key followed
 260          * by the confounder
 261          *
 262          * here the gensec session key is used and
 263          * not the dcerpc ncacn_ip_tcp "SystemLibraryDTC" key!
 264          */
 265         enc_key = data_blob_const(_enc_key, sizeof(_enc_key));
 266         MD5Init(&md5);
 267         MD5Update(&md5, gensec_skey->data, gensec_skey->length);
 268         MD5Update(&md5, confounder.data, confounder.length);
 269         MD5Final(enc_key.data, &md5);
 270
 271         /*
 272          * the first 4 byte are the crc32 checksum
 273          * of the remaining bytes
 274          */
 275         crc32_calc = crc32_calc_buffer(in->data, in->length);
 276         SIVAL(enc_buffer.data, 16, crc32_calc);
 277
 278         /*
 279          * copy the plain buffer part and
 280          * encrypt it using the created encryption key using arcfour
 281          */
 282         memcpy(enc_buffer.data+20, in->data, in->length);
 283         talloc_free(rid_crypt_out.data);
 284
 285         arcfour_crypt_blob(enc_buffer.data+16, enc_buffer.length-16, &enc_key);
 286
 287         *out = enc_buffer;
 288
 289         return WERR_OK;
 290 }
 291
 292 /*
 293   encrypt a DRSUAPI attribute ready for sending over the wire
 294   Only some attribute types are encrypted
 295  */
 296 WERROR drsuapi_encrypt_attribute(TALLOC_CTX *mem_ctx,
 297                                  const DATA_BLOB *gensec_skey,
 298                                  uint32_t rid,
 299                                  struct drsuapi_DsReplicaAttribute *attr)
 300 {
 301         WERROR status;
 302         DATA_BLOB *plain_data;
 303         DATA_BLOB enc_data;
 304         bool rid_crypt = false;
 305
 306         if (attr->value_ctr.num_values == 0) {
 307                 return WERR_OK;
 308         }
 309
 310         switch (attr->attid) {
 311         case DRSUAPI_ATTRIBUTE_dBCSPwd:
 312         case DRSUAPI_ATTRIBUTE_unicodePwd:
 313         case DRSUAPI_ATTRIBUTE_ntPwdHistory:
 314         case DRSUAPI_ATTRIBUTE_lmPwdHistory:
 315                 rid_crypt = true;
 316                 break;
 317         case DRSUAPI_ATTRIBUTE_supplementalCredentials:
 318         case DRSUAPI_ATTRIBUTE_priorValue:
 319         case DRSUAPI_ATTRIBUTE_currentValue:
 320         case DRSUAPI_ATTRIBUTE_trustAuthOutgoing:
 321         case DRSUAPI_ATTRIBUTE_trustAuthIncoming:
 322         case DRSUAPI_ATTRIBUTE_initialAuthOutgoing:
 323         case DRSUAPI_ATTRIBUTE_initialAuthIncoming:
 324                 break;
 325         default:
 326                 return WERR_OK;
 327         }
 328
 329         if (attr->value_ctr.num_values > 1) {
 330                 return WERR_DS_DRA_INVALID_PARAMETER;
 331         }
 332
 333         if (!attr->value_ctr.values[0].blob) {
 334                 return WERR_DS_DRA_INVALID_PARAMETER;
 335         }
 336
 337         plain_data      = attr->value_ctr.values[0].blob;
 338
 339         status = drsuapi_encrypt_attribute_value(mem_ctx,
 340                                                  gensec_skey,
 341                                                  rid_crypt,
 342                                                  rid,
 343                                                  plain_data,
 344                                                  &enc_data);
 345         W_ERROR_NOT_OK_RETURN(status);
 346
 347         talloc_free(attr->value_ctr.values[0].blob->data);
 348         *attr->value_ctr.values[0].blob = enc_data;
 349
 350         return WERR_OK;
 351 }
 352