libcli/auth/schannel_sign.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    schannel library code
   5
   6    Copyright (C) Andrew Tridgell 2004
   7    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21 */
  22
  23 #include "includes.h"
  24 #include "../libcli/auth/schannel.h"
  25 #include "../lib/crypto/crypto.h"
  26
  27 static void netsec_offset_and_sizes(struct schannel_state *state,
  28                                     bool do_seal,
  29                                     uint32_t *_min_sig_size,
  30                                     uint32_t *_used_sig_size,
  31                                     uint32_t *_checksum_length,
  32                                     uint32_t *_confounder_ofs)
  33 {
  34         uint32_t min_sig_size = 24;
  35         uint32_t used_sig_size = 32;
  36         uint32_t checksum_length = 8;
  37         uint32_t confounder_ofs = 24;
  38
  39         if (do_seal) {
  40                 min_sig_size += 8;
  41         }
  42
  43         if (_min_sig_size) {
  44                 *_min_sig_size = min_sig_size;
  45         }
  46
  47         if (_used_sig_size) {
  48                 *_used_sig_size = used_sig_size;
  49         }
  50
  51         if (_checksum_length) {
  52                 *_checksum_length = checksum_length;
  53         }
  54
  55         if (_confounder_ofs) {
  56                 *_confounder_ofs = confounder_ofs;
  57         }
  58 }
  59
  60 /*******************************************************************
  61  Encode or Decode the sequence number (which is symmetric)
  62  ********************************************************************/
  63 static void netsec_do_seq_num(struct schannel_state *state,
  64                               const uint8_t *checksum,
  65                               uint32_t checksum_length,
  66                               uint8_t seq_num[8])
  67 {
  68         static const uint8_t zeros[4];
  69         uint8_t sequence_key[16];
  70         uint8_t digest1[16];
  71
  72         hmac_md5(state->creds->session_key, zeros, sizeof(zeros), digest1);
  73         hmac_md5(digest1, checksum, checksum_length, sequence_key);
  74         arcfour_crypt(seq_num, sequence_key, 8);
  75
  76         state->seq_num++;
  77 }
  78
  79 static void netsec_do_seal(struct schannel_state *state,
  80                            const uint8_t seq_num[8],
  81                            uint8_t confounder[8],
  82                            uint8_t *data, uint32_t length)
  83 {
  84         uint8_t sealing_key[16];
  85         static const uint8_t zeros[4];
  86         uint8_t digest2[16];
  87         uint8_t sess_kf0[16];
  88         int i;
  89
  90         for (i = 0; i < 16; i++) {
  91                 sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
  92         }
  93
  94         hmac_md5(sess_kf0, zeros, 4, digest2);
  95         hmac_md5(digest2, seq_num, 8, sealing_key);
  96
  97         arcfour_crypt(confounder, sealing_key, 8);
  98         arcfour_crypt(data, sealing_key, length);
  99 }
 100
 101 /*******************************************************************
 102  Create a digest over the entire packet (including the data), and
 103  MD5 it with the session key.
 104  ********************************************************************/
 105 static void netsec_do_sign(struct schannel_state *state,
 106                            const uint8_t *confounder,
 107                            const uint8_t *data, size_t data_len,
 108                            uint8_t header[8],
 109                            uint8_t *checksum)
 110 {
 111         uint8_t packet_digest[16];
 112         static const uint8_t zeros[4];
 113         struct MD5Context ctx;
 114
 115         MD5Init(&ctx);
 116         MD5Update(&ctx, zeros, 4);
 117         if (confounder) {
 118                 SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 119                 SSVAL(header, 2, NL_SEAL_RC4);
 120                 SSVAL(header, 4, 0xFFFF);
 121                 SSVAL(header, 6, 0x0000);
 122
 123                 MD5Update(&ctx, header, 8);
 124                 MD5Update(&ctx, confounder, 8);
 125         } else {
 126                 SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 127                 SSVAL(header, 2, NL_SEAL_NONE);
 128                 SSVAL(header, 4, 0xFFFF);
 129                 SSVAL(header, 6, 0x0000);
 130
 131                 MD5Update(&ctx, header, 8);
 132         }
 133         MD5Update(&ctx, data, data_len);
 134         MD5Final(packet_digest, &ctx);
 135
 136         hmac_md5(state->creds->session_key,
 137                  packet_digest, sizeof(packet_digest),
 138                  checksum);
 139 }
 140
 141 NTSTATUS netsec_incoming_packet(struct schannel_state *state,
 142                                 TALLOC_CTX *mem_ctx,
 143                                 bool do_unseal,
 144                                 uint8_t *data, size_t length,
 145                                 const DATA_BLOB *sig)
 146 {
 147         uint32_t min_sig_size = 0;
 148         uint8_t header[8];
 149         uint8_t checksum[32];
 150         uint32_t checksum_length = sizeof(checksum_length);
 151         uint8_t _confounder[8];
 152         uint8_t *confounder = NULL;
 153         uint32_t confounder_ofs = 0;
 154         uint8_t seq_num[8];
 155         int ret;
 156
 157         netsec_offset_and_sizes(state,
 158                                 do_unseal,
 159                                 &min_sig_size,
 160                                 NULL,
 161                                 &checksum_length,
 162                                 &confounder_ofs);
 163
 164         if (sig->length < min_sig_size) {
 165                 return NT_STATUS_ACCESS_DENIED;
 166         }
 167
 168         if (do_unseal) {
 169                 confounder = _confounder;
 170                 memcpy(confounder, sig->data+confounder_ofs, 8);
 171         } else {
 172                 confounder = NULL;
 173         }
 174
 175         RSIVAL(seq_num, 0, state->seq_num);
 176         SIVAL(seq_num, 4, state->initiator?0:0x80);
 177
 178         if (do_unseal) {
 179                 netsec_do_seal(state, seq_num,
 180                                confounder,
 181                                data, length);
 182         }
 183
 184         netsec_do_sign(state, confounder,
 185                        data, length,
 186                        header, checksum);
 187
 188         ret = memcmp(checksum, sig->data+16, checksum_length);
 189         if (ret != 0) {
 190                 dump_data_pw("calc digest:", checksum, checksum_length);
 191                 dump_data_pw("wire digest:", sig->data+16, checksum_length);
 192                 return NT_STATUS_ACCESS_DENIED;
 193         }
 194
 195         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 196
 197         ret = memcmp(seq_num, sig->data+8, 8);
 198         if (ret != 0) {
 199                 dump_data_pw("calc seq num:", seq_num, 8);
 200                 dump_data_pw("wire seq num:", sig->data+8, 8);
 201                 return NT_STATUS_ACCESS_DENIED;
 202         }
 203
 204         return NT_STATUS_OK;
 205 }
 206
 207 NTSTATUS netsec_outgoing_packet(struct schannel_state *state,
 208                                 TALLOC_CTX *mem_ctx,
 209                                 bool do_seal,
 210                                 uint8_t *data, size_t length,
 211                                 DATA_BLOB *sig)
 212 {
 213         uint32_t min_sig_size = 0;
 214         uint32_t used_sig_size = 0;
 215         uint8_t header[8];
 216         uint8_t checksum[32];
 217         uint32_t checksum_length = sizeof(checksum_length);
 218         uint8_t _confounder[8];
 219         uint8_t *confounder = NULL;
 220         uint32_t confounder_ofs = 0;
 221         uint8_t seq_num[8];
 222
 223         netsec_offset_and_sizes(state,
 224                                 do_seal,
 225                                 &min_sig_size,
 226                                 &used_sig_size,
 227                                 &checksum_length,
 228                                 &confounder_ofs);
 229
 230         RSIVAL(seq_num, 0, state->seq_num);
 231         SIVAL(seq_num, 4, state->initiator?0x80:0);
 232
 233         if (do_seal) {
 234                 confounder = _confounder;
 235                 generate_random_buffer(confounder, 8);
 236         } else {
 237                 confounder = NULL;
 238         }
 239
 240         netsec_do_sign(state, confounder,
 241                        data, length,
 242                        header, checksum);
 243
 244         if (do_seal) {
 245                 netsec_do_seal(state, seq_num,
 246                                confounder,
 247                                data, length);
 248         }
 249
 250         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 251
 252         (*sig) = data_blob_talloc_zero(mem_ctx, used_sig_size);
 253
 254         memcpy(sig->data, header, 8);
 255         memcpy(sig->data+8, seq_num, 8);
 256         memcpy(sig->data+16, checksum, checksum_length);
 257
 258         if (confounder) {
 259                 memcpy(sig->data+confounder_ofs, confounder, 8);
 260         }
 261
 262         dump_data_pw("signature:", sig->data+ 0, 8);
 263         dump_data_pw("seq_num  :", sig->data+ 8, 8);
 264         dump_data_pw("digest   :", sig->data+16, checksum_length);
 265         dump_data_pw("confound :", sig->data+confounder_ofs, 8);
 266
 267         return NT_STATUS_OK;
 268 }