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;
  35         uint32_t used_sig_size;
  36         uint32_t checksum_length;
  37         uint32_t confounder_ofs;
  38
  39         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
  40                 min_sig_size = 48;
  41                 used_sig_size = 56;
  42                 /*
  43                  * Note: windows has a bug here and uses the old values...
  44                  *
  45                  * checksum_length = 32;
  46                  * confounder_ofs = 48;
  47                  */
  48                 checksum_length = 8;
  49                 confounder_ofs = 24;
  50         } else {
  51                 min_sig_size = 24;
  52                 used_sig_size = 32;
  53                 checksum_length = 8;
  54                 confounder_ofs = 24;
  55         }
  56
  57         if (do_seal) {
  58                 min_sig_size += 8;
  59         }
  60
  61         if (_min_sig_size) {
  62                 *_min_sig_size = min_sig_size;
  63         }
  64
  65         if (_used_sig_size) {
  66                 *_used_sig_size = used_sig_size;
  67         }
  68
  69         if (_checksum_length) {
  70                 *_checksum_length = checksum_length;
  71         }
  72
  73         if (_confounder_ofs) {
  74                 *_confounder_ofs = confounder_ofs;
  75         }
  76 }
  77
  78 /*******************************************************************
  79  Encode or Decode the sequence number (which is symmetric)
  80  ********************************************************************/
  81 static void netsec_do_seq_num(struct schannel_state *state,
  82                               const uint8_t *checksum,
  83                               uint32_t checksum_length,
  84                               uint8_t seq_num[8])
  85 {
  86         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
  87                 AES_KEY key;
  88                 uint8_t iv[AES_BLOCK_SIZE];
  89
  90                 AES_set_encrypt_key(state->creds->session_key, 128, &key);
  91                 ZERO_STRUCT(iv);
  92                 memcpy(iv+0, checksum, 8);
  93                 memcpy(iv+8, checksum, 8);
  94
  95                 aes_cfb8_encrypt(seq_num, seq_num, 8, &key, iv, AES_ENCRYPT);
  96         } else {
  97                 static const uint8_t zeros[4];
  98                 uint8_t sequence_key[16];
  99                 uint8_t digest1[16];
 100
 101                 hmac_md5(state->creds->session_key, zeros, sizeof(zeros), digest1);
 102                 hmac_md5(digest1, checksum, checksum_length, sequence_key);
 103                 arcfour_crypt(seq_num, sequence_key, 8);
 104         }
 105
 106         state->seq_num++;
 107 }
 108
 109 static void netsec_do_seal(struct schannel_state *state,
 110                            const uint8_t seq_num[8],
 111                            uint8_t confounder[8],
 112                            uint8_t *data, uint32_t length,
 113                            bool forward)
 114 {
 115         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
 116                 AES_KEY key;
 117                 uint8_t iv[AES_BLOCK_SIZE];
 118                 uint8_t sess_kf0[16];
 119                 int i;
 120
 121                 for (i = 0; i < 16; i++) {
 122                         sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
 123                 }
 124
 125                 AES_set_encrypt_key(sess_kf0, 128, &key);
 126                 ZERO_STRUCT(iv);
 127                 memcpy(iv+0, seq_num, 8);
 128                 memcpy(iv+8, seq_num, 8);
 129
 130                 if (forward) {
 131                         aes_cfb8_encrypt(confounder, confounder, 8, &key, iv, AES_ENCRYPT);
 132                         aes_cfb8_encrypt(data, data, length, &key, iv, AES_ENCRYPT);
 133                 } else {
 134                         aes_cfb8_encrypt(confounder, confounder, 8, &key, iv, AES_DECRYPT);
 135                         aes_cfb8_encrypt(data, data, length, &key, iv, AES_DECRYPT);
 136                 }
 137         } else {
 138                 uint8_t sealing_key[16];
 139                 static const uint8_t zeros[4];
 140                 uint8_t digest2[16];
 141                 uint8_t sess_kf0[16];
 142                 int i;
 143
 144                 for (i = 0; i < 16; i++) {
 145                         sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
 146                 }
 147
 148                 hmac_md5(sess_kf0, zeros, 4, digest2);
 149                 hmac_md5(digest2, seq_num, 8, sealing_key);
 150
 151                 arcfour_crypt(confounder, sealing_key, 8);
 152                 arcfour_crypt(data, sealing_key, length);
 153         }
 154 }
 155
 156 /*******************************************************************
 157  Create a digest over the entire packet (including the data), and
 158  MD5 it with the session key.
 159  ********************************************************************/
 160 static void netsec_do_sign(struct schannel_state *state,
 161                            const uint8_t *confounder,
 162                            const uint8_t *data, size_t length,
 163                            uint8_t header[8],
 164                            uint8_t *checksum)
 165 {
 166         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
 167                 struct HMACSHA256Context ctx;
 168
 169                 hmac_sha256_init(state->creds->session_key,
 170                                  sizeof(state->creds->session_key),
 171                                  &ctx);
 172
 173                 if (confounder) {
 174                         SSVAL(header, 0, NL_SIGN_HMAC_SHA256);
 175                         SSVAL(header, 2, NL_SEAL_AES128);
 176                         SSVAL(header, 4, 0xFFFF);
 177                         SSVAL(header, 6, 0x0000);
 178
 179                         hmac_sha256_update(header, 8, &ctx);
 180                         hmac_sha256_update(confounder, 8, &ctx);
 181                 } else {
 182                         SSVAL(header, 0, NL_SIGN_HMAC_SHA256);
 183                         SSVAL(header, 2, NL_SEAL_NONE);
 184                         SSVAL(header, 4, 0xFFFF);
 185                         SSVAL(header, 6, 0x0000);
 186
 187                         hmac_sha256_update(header, 8, &ctx);
 188                 }
 189
 190                 hmac_sha256_update(data, length, &ctx);
 191
 192                 hmac_sha256_final(checksum, &ctx);
 193         } else {
 194                 uint8_t packet_digest[16];
 195                 static const uint8_t zeros[4];
 196                 MD5_CTX ctx;
 197
 198                 MD5Init(&ctx);
 199                 MD5Update(&ctx, zeros, 4);
 200                 if (confounder) {
 201                         SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 202                         SSVAL(header, 2, NL_SEAL_RC4);
 203                         SSVAL(header, 4, 0xFFFF);
 204                         SSVAL(header, 6, 0x0000);
 205
 206                         MD5Update(&ctx, header, 8);
 207                         MD5Update(&ctx, confounder, 8);
 208                 } else {
 209                         SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 210                         SSVAL(header, 2, NL_SEAL_NONE);
 211                         SSVAL(header, 4, 0xFFFF);
 212                         SSVAL(header, 6, 0x0000);
 213
 214                         MD5Update(&ctx, header, 8);
 215                 }
 216                 MD5Update(&ctx, data, length);
 217                 MD5Final(packet_digest, &ctx);
 218
 219                 hmac_md5(state->creds->session_key,
 220                          packet_digest, sizeof(packet_digest),
 221                          checksum);
 222         }
 223 }
 224
 225 NTSTATUS netsec_incoming_packet(struct schannel_state *state,
 226                                 bool do_unseal,
 227                                 uint8_t *data, size_t length,
 228                                 const DATA_BLOB *sig)
 229 {
 230         uint32_t min_sig_size = 0;
 231         uint8_t header[8];
 232         uint8_t checksum[32];
 233         uint32_t checksum_length = sizeof(checksum_length);
 234         uint8_t _confounder[8];
 235         uint8_t *confounder = NULL;
 236         uint32_t confounder_ofs = 0;
 237         uint8_t seq_num[8];
 238         int ret;
 239
 240         netsec_offset_and_sizes(state,
 241                                 do_unseal,
 242                                 &min_sig_size,
 243                                 NULL,
 244                                 &checksum_length,
 245                                 &confounder_ofs);
 246
 247         if (sig->length < min_sig_size) {
 248                 return NT_STATUS_ACCESS_DENIED;
 249         }
 250
 251         if (do_unseal) {
 252                 confounder = _confounder;
 253                 memcpy(confounder, sig->data+confounder_ofs, 8);
 254         } else {
 255                 confounder = NULL;
 256         }
 257
 258         RSIVAL(seq_num, 0, state->seq_num);
 259         SIVAL(seq_num, 4, state->initiator?0:0x80);
 260
 261         if (do_unseal) {
 262                 netsec_do_seal(state, seq_num,
 263                                confounder,
 264                                data, length,
 265                                false);
 266         }
 267
 268         netsec_do_sign(state, confounder,
 269                        data, length,
 270                        header, checksum);
 271
 272         ret = memcmp(checksum, sig->data+16, checksum_length);
 273         if (ret != 0) {
 274                 dump_data_pw("calc digest:", checksum, checksum_length);
 275                 dump_data_pw("wire digest:", sig->data+16, checksum_length);
 276                 return NT_STATUS_ACCESS_DENIED;
 277         }
 278
 279         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 280
 281         ret = memcmp(seq_num, sig->data+8, 8);
 282         if (ret != 0) {
 283                 dump_data_pw("calc seq num:", seq_num, 8);
 284                 dump_data_pw("wire seq num:", sig->data+8, 8);
 285                 return NT_STATUS_ACCESS_DENIED;
 286         }
 287
 288         return NT_STATUS_OK;
 289 }
 290
 291 uint32_t netsec_outgoing_sig_size(struct schannel_state *state)
 292 {
 293         uint32_t sig_size = 0;
 294
 295         netsec_offset_and_sizes(state,
 296                                 true,
 297                                 NULL,
 298                                 &sig_size,
 299                                 NULL,
 300                                 NULL);
 301
 302         return sig_size;
 303 }
 304
 305 NTSTATUS netsec_outgoing_packet(struct schannel_state *state,
 306                                 TALLOC_CTX *mem_ctx,
 307                                 bool do_seal,
 308                                 uint8_t *data, size_t length,
 309                                 DATA_BLOB *sig)
 310 {
 311         uint32_t min_sig_size = 0;
 312         uint32_t used_sig_size = 0;
 313         uint8_t header[8];
 314         uint8_t checksum[32];
 315         uint32_t checksum_length = sizeof(checksum_length);
 316         uint8_t _confounder[8];
 317         uint8_t *confounder = NULL;
 318         uint32_t confounder_ofs = 0;
 319         uint8_t seq_num[8];
 320
 321         netsec_offset_and_sizes(state,
 322                                 do_seal,
 323                                 &min_sig_size,
 324                                 &used_sig_size,
 325                                 &checksum_length,
 326                                 &confounder_ofs);
 327
 328         RSIVAL(seq_num, 0, state->seq_num);
 329         SIVAL(seq_num, 4, state->initiator?0x80:0);
 330
 331         if (do_seal) {
 332                 confounder = _confounder;
 333                 generate_random_buffer(confounder, 8);
 334         } else {
 335                 confounder = NULL;
 336         }
 337
 338         netsec_do_sign(state, confounder,
 339                        data, length,
 340                        header, checksum);
 341
 342         if (do_seal) {
 343                 netsec_do_seal(state, seq_num,
 344                                confounder,
 345                                data, length,
 346                                true);
 347         }
 348
 349         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 350
 351         (*sig) = data_blob_talloc_zero(mem_ctx, used_sig_size);
 352
 353         memcpy(sig->data, header, 8);
 354         memcpy(sig->data+8, seq_num, 8);
 355         memcpy(sig->data+16, checksum, checksum_length);
 356
 357         if (confounder) {
 358                 memcpy(sig->data+confounder_ofs, confounder, 8);
 359         }
 360
 361         dump_data_pw("signature:", sig->data+ 0, 8);
 362         dump_data_pw("seq_num  :", sig->data+ 8, 8);
 363         dump_data_pw("digest   :", sig->data+16, checksum_length);
 364         dump_data_pw("confound :", sig->data+confounder_ofs, 8);
 365
 366         return NT_STATUS_OK;
 367 }