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
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19
  20 */
  21
  22 #include "includes.h"
  23 #include "../lib/util/dlinklist.h"
  24 #include "librpc/gen_ndr/ndr_misc.h"
  25 #include "librpc/gen_ndr/ndr_drsuapi.h"
  26 #include "librpc/gen_ndr/ndr_drsblobs.h"
  27 #include "../lib/crypto/crypto.h"
  28 #include "../libcli/drsuapi/drsuapi.h"
  29 #include "libcli/auth/libcli_auth.h"
  30
  31 WERROR drsuapi_decrypt_attribute_value(TALLOC_CTX *mem_ctx,
  32                                        const DATA_BLOB *gensec_skey,
  33                                        bool rid_crypt,
  34                                        uint32_t rid,
  35                                        DATA_BLOB *in,
  36                                        DATA_BLOB *out)
  37 {
  38         DATA_BLOB confounder;
  39         DATA_BLOB enc_buffer;
  40
  41         struct MD5Context md5;
  42         uint8_t _enc_key[16];
  43         DATA_BLOB enc_key;
  44
  45         DATA_BLOB dec_buffer;
  46
  47         uint32_t crc32_given;
  48         uint32_t crc32_calc;
  49         DATA_BLOB checked_buffer;
  50
  51         DATA_BLOB plain_buffer;
  52
  53         /*
  54          * users with rid == 0 should not exist
  55          */
  56         if (rid_crypt && rid == 0) {
  57                 return WERR_DS_DRA_INVALID_PARAMETER;
  58         }
  59
  60         /*
  61          * the first 16 bytes at the beginning are the confounder
  62          * followed by the 4 byte crc32 checksum
  63          */
  64         if (in->length < 20) {
  65                 return WERR_DS_DRA_INVALID_PARAMETER;
  66         }
  67         confounder = data_blob_const(in->data, 16);
  68         enc_buffer = data_blob_const(in->data + 16, in->length - 16);
  69
  70         /*
  71          * build the encryption key md5 over the session key followed
  72          * by the confounder
  73          *
  74          * here the gensec session key is used and
  75          * not the dcerpc ncacn_ip_tcp "SystemLibraryDTC" key!
  76          */
  77         enc_key = data_blob_const(_enc_key, sizeof(_enc_key));
  78         MD5Init(&md5);
  79         MD5Update(&md5, gensec_skey->data, gensec_skey->length);
  80         MD5Update(&md5, confounder.data, confounder.length);
  81         MD5Final(enc_key.data, &md5);
  82
  83         /*
  84          * copy the encrypted buffer part and
  85          * decrypt it using the created encryption key using arcfour
  86          */
  87         dec_buffer = data_blob_const(enc_buffer.data, enc_buffer.length);
  88         arcfour_crypt_blob(dec_buffer.data, dec_buffer.length, &enc_key);
  89
  90         /*
  91          * the first 4 byte are the crc32 checksum
  92          * of the remaining bytes
  93          */
  94         crc32_given = IVAL(dec_buffer.data, 0);
  95         crc32_calc = crc32_calc_buffer(dec_buffer.data + 4 , dec_buffer.length - 4);
  96         if (crc32_given != crc32_calc) {
  97                 return WERR_SEC_E_DECRYPT_FAILURE;
  98         }
  99         checked_buffer = data_blob_const(dec_buffer.data + 4, dec_buffer.length - 4);
 100
 101         plain_buffer = data_blob_talloc(mem_ctx, checked_buffer.data, checked_buffer.length);
 102         W_ERROR_HAVE_NO_MEMORY(plain_buffer.data);
 103
 104         /*
 105          * The following rid_crypt obfuscation isn't session specific
 106          * and not really needed here, because we allways know the rid of the
 107          * user account.
 108          *
 109          * some attributes with this 'additional encryption' include
 110          * dBCSPwd, unicodePwd, ntPwdHistory, lmPwdHistory
 111          *
 112          * But for the rest of samba it's easier when we remove this static
 113          * obfuscation here
 114          */
 115         if (rid_crypt) {
 116                 uint32_t i, num_hashes;
 117
 118                 if ((checked_buffer.length % 16) != 0) {
 119                         return WERR_DS_DRA_INVALID_PARAMETER;
 120                 }
 121
 122                 num_hashes = plain_buffer.length / 16;
 123                 for (i = 0; i < num_hashes; i++) {
 124                         uint32_t offset = i * 16;
 125                         sam_rid_crypt(rid, checked_buffer.data + offset, plain_buffer.data + offset, 0);
 126                 }
 127         }
 128
 129         *out = plain_buffer;
 130         return WERR_OK;
 131 }
 132
 133 WERROR drsuapi_decrypt_attribute(TALLOC_CTX *mem_ctx,
 134                                  const DATA_BLOB *gensec_skey,
 135                                  uint32_t rid,
 136                                  struct drsuapi_DsReplicaAttribute *attr)
 137 {
 138         WERROR status;
 139         DATA_BLOB *enc_data;
 140         DATA_BLOB plain_data;
 141         bool rid_crypt = false;
 142
 143         if (attr->value_ctr.num_values == 0) {
 144                 return WERR_OK;
 145         }
 146
 147         switch (attr->attid) {
 148         case DRSUAPI_ATTRIBUTE_dBCSPwd:
 149         case DRSUAPI_ATTRIBUTE_unicodePwd:
 150         case DRSUAPI_ATTRIBUTE_ntPwdHistory:
 151         case DRSUAPI_ATTRIBUTE_lmPwdHistory:
 152                 rid_crypt = true;
 153                 break;
 154         case DRSUAPI_ATTRIBUTE_supplementalCredentials:
 155         case DRSUAPI_ATTRIBUTE_priorValue:
 156         case DRSUAPI_ATTRIBUTE_currentValue:
 157         case DRSUAPI_ATTRIBUTE_trustAuthOutgoing:
 158         case DRSUAPI_ATTRIBUTE_trustAuthIncoming:
 159         case DRSUAPI_ATTRIBUTE_initialAuthOutgoing:
 160         case DRSUAPI_ATTRIBUTE_initialAuthIncoming:
 161                 break;
 162         default:
 163                 return WERR_OK;
 164         }
 165
 166         if (attr->value_ctr.num_values > 1) {
 167                 return WERR_DS_DRA_INVALID_PARAMETER;
 168         }
 169
 170         if (!attr->value_ctr.values[0].blob) {
 171                 return WERR_DS_DRA_INVALID_PARAMETER;
 172         }
 173
 174         enc_data        = attr->value_ctr.values[0].blob;
 175
 176         status = drsuapi_decrypt_attribute_value(mem_ctx,
 177                                                  gensec_skey,
 178                                                  rid_crypt,
 179                                                  rid,
 180                                                  enc_data,
 181                                                  &plain_data);
 182         W_ERROR_NOT_OK_RETURN(status);
 183
 184         talloc_free(attr->value_ctr.values[0].blob->data);
 185         *attr->value_ctr.values[0].blob = plain_data;
 186
 187         return WERR_OK;
 188 }