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 struct schannel_state {
  28         uint64_t seq_num;
  29         bool initiator;
  30         struct netlogon_creds_CredentialState *creds;
  31 };
  32
  33 #define SETUP_SEQNUM(state, buf, initiator) do { \
  34         uint8_t *_buf = buf; \
  35         uint32_t _seq_num_low = (state)->seq_num & UINT32_MAX; \
  36         uint32_t _seq_num_high = (state)->seq_num >> 32; \
  37         if (initiator) { \
  38                 _seq_num_high |= 0x80000000; \
  39         } \
  40         RSIVAL(_buf, 0, _seq_num_low); \
  41         RSIVAL(_buf, 4, _seq_num_high); \
  42 } while(0)
  43
  44 struct schannel_state *netsec_create_state(TALLOC_CTX *mem_ctx,
  45                                 struct netlogon_creds_CredentialState *creds,
  46                                 bool initiator)
  47 {
  48         struct schannel_state *state;
  49
  50         state = talloc(mem_ctx, struct schannel_state);
  51         if (state == NULL) {
  52                 return NULL;
  53         }
  54
  55         state->initiator = initiator;
  56         state->seq_num = 0;
  57         state->creds = netlogon_creds_copy(state, creds);
  58         if (state->creds == NULL) {
  59                 talloc_free(state);
  60                 return NULL;
  61         }
  62
  63         return state;
  64 }
  65
  66 static void netsec_offset_and_sizes(struct schannel_state *state,
  67                                     bool do_seal,
  68                                     uint32_t *_min_sig_size,
  69                                     uint32_t *_used_sig_size,
  70                                     uint32_t *_checksum_length,
  71                                     uint32_t *_confounder_ofs)
  72 {
  73         uint32_t min_sig_size;
  74         uint32_t used_sig_size;
  75         uint32_t checksum_length;
  76         uint32_t confounder_ofs;
  77
  78         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
  79                 min_sig_size = 48;
  80                 used_sig_size = 56;
  81                 /*
  82                  * Note: windows has a bug here and uses the old values...
  83                  *
  84                  * checksum_length = 32;
  85                  * confounder_ofs = 48;
  86                  */
  87                 checksum_length = 8;
  88                 confounder_ofs = 24;
  89         } else {
  90                 min_sig_size = 24;
  91                 used_sig_size = 32;
  92                 checksum_length = 8;
  93                 confounder_ofs = 24;
  94         }
  95
  96         if (do_seal) {
  97                 min_sig_size += 8;
  98         }
  99
 100         if (_min_sig_size) {
 101                 *_min_sig_size = min_sig_size;
 102         }
 103
 104         if (_used_sig_size) {
 105                 *_used_sig_size = used_sig_size;
 106         }
 107
 108         if (_checksum_length) {
 109                 *_checksum_length = checksum_length;
 110         }
 111
 112         if (_confounder_ofs) {
 113                 *_confounder_ofs = confounder_ofs;
 114         }
 115 }
 116
 117 /*******************************************************************
 118  Encode or Decode the sequence number (which is symmetric)
 119  ********************************************************************/
 120 static void netsec_do_seq_num(struct schannel_state *state,
 121                               const uint8_t *checksum,
 122                               uint32_t checksum_length,
 123                               uint8_t seq_num[8])
 124 {
 125         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
 126                 AES_KEY key;
 127                 uint8_t iv[AES_BLOCK_SIZE];
 128
 129                 AES_set_encrypt_key(state->creds->session_key, 128, &key);
 130                 ZERO_STRUCT(iv);
 131                 memcpy(iv+0, checksum, 8);
 132                 memcpy(iv+8, checksum, 8);
 133
 134                 aes_cfb8_encrypt(seq_num, seq_num, 8, &key, iv, AES_ENCRYPT);
 135         } else {
 136                 static const uint8_t zeros[4];
 137                 uint8_t sequence_key[16];
 138                 uint8_t digest1[16];
 139
 140                 hmac_md5(state->creds->session_key, zeros, sizeof(zeros), digest1);
 141                 hmac_md5(digest1, checksum, checksum_length, sequence_key);
 142                 arcfour_crypt(seq_num, sequence_key, 8);
 143         }
 144
 145         state->seq_num++;
 146 }
 147
 148 static void netsec_do_seal(struct schannel_state *state,
 149                            const uint8_t seq_num[8],
 150                            uint8_t confounder[8],
 151                            uint8_t *data, uint32_t length,
 152                            bool forward)
 153 {
 154         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
 155                 AES_KEY key;
 156                 uint8_t iv[AES_BLOCK_SIZE];
 157                 uint8_t sess_kf0[16];
 158                 int i;
 159
 160                 for (i = 0; i < 16; i++) {
 161                         sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
 162                 }
 163
 164                 AES_set_encrypt_key(sess_kf0, 128, &key);
 165                 ZERO_STRUCT(iv);
 166                 memcpy(iv+0, seq_num, 8);
 167                 memcpy(iv+8, seq_num, 8);
 168
 169                 if (forward) {
 170                         aes_cfb8_encrypt(confounder, confounder, 8, &key, iv, AES_ENCRYPT);
 171                         aes_cfb8_encrypt(data, data, length, &key, iv, AES_ENCRYPT);
 172                 } else {
 173                         aes_cfb8_encrypt(confounder, confounder, 8, &key, iv, AES_DECRYPT);
 174                         aes_cfb8_encrypt(data, data, length, &key, iv, AES_DECRYPT);
 175                 }
 176         } else {
 177                 uint8_t sealing_key[16];
 178                 static const uint8_t zeros[4];
 179                 uint8_t digest2[16];
 180                 uint8_t sess_kf0[16];
 181                 int i;
 182
 183                 for (i = 0; i < 16; i++) {
 184                         sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
 185                 }
 186
 187                 hmac_md5(sess_kf0, zeros, 4, digest2);
 188                 hmac_md5(digest2, seq_num, 8, sealing_key);
 189
 190                 arcfour_crypt(confounder, sealing_key, 8);
 191                 arcfour_crypt(data, sealing_key, length);
 192         }
 193 }
 194
 195 /*******************************************************************
 196  Create a digest over the entire packet (including the data), and
 197  MD5 it with the session key.
 198  ********************************************************************/
 199 static void netsec_do_sign(struct schannel_state *state,
 200                            const uint8_t *confounder,
 201                            const uint8_t *data, size_t length,
 202                            uint8_t header[8],
 203                            uint8_t *checksum)
 204 {
 205         if (state->creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
 206                 struct HMACSHA256Context ctx;
 207
 208                 hmac_sha256_init(state->creds->session_key,
 209                                  sizeof(state->creds->session_key),
 210                                  &ctx);
 211
 212                 if (confounder) {
 213                         SSVAL(header, 0, NL_SIGN_HMAC_SHA256);
 214                         SSVAL(header, 2, NL_SEAL_AES128);
 215                         SSVAL(header, 4, 0xFFFF);
 216                         SSVAL(header, 6, 0x0000);
 217
 218                         hmac_sha256_update(header, 8, &ctx);
 219                         hmac_sha256_update(confounder, 8, &ctx);
 220                 } else {
 221                         SSVAL(header, 0, NL_SIGN_HMAC_SHA256);
 222                         SSVAL(header, 2, NL_SEAL_NONE);
 223                         SSVAL(header, 4, 0xFFFF);
 224                         SSVAL(header, 6, 0x0000);
 225
 226                         hmac_sha256_update(header, 8, &ctx);
 227                 }
 228
 229                 hmac_sha256_update(data, length, &ctx);
 230
 231                 hmac_sha256_final(checksum, &ctx);
 232         } else {
 233                 uint8_t packet_digest[16];
 234                 static const uint8_t zeros[4];
 235                 MD5_CTX ctx;
 236
 237                 MD5Init(&ctx);
 238                 MD5Update(&ctx, zeros, 4);
 239                 if (confounder) {
 240                         SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 241                         SSVAL(header, 2, NL_SEAL_RC4);
 242                         SSVAL(header, 4, 0xFFFF);
 243                         SSVAL(header, 6, 0x0000);
 244
 245                         MD5Update(&ctx, header, 8);
 246                         MD5Update(&ctx, confounder, 8);
 247                 } else {
 248                         SSVAL(header, 0, NL_SIGN_HMAC_MD5);
 249                         SSVAL(header, 2, NL_SEAL_NONE);
 250                         SSVAL(header, 4, 0xFFFF);
 251                         SSVAL(header, 6, 0x0000);
 252
 253                         MD5Update(&ctx, header, 8);
 254                 }
 255                 MD5Update(&ctx, data, length);
 256                 MD5Final(packet_digest, &ctx);
 257
 258                 hmac_md5(state->creds->session_key,
 259                          packet_digest, sizeof(packet_digest),
 260                          checksum);
 261         }
 262 }
 263
 264 NTSTATUS netsec_incoming_packet(struct schannel_state *state,
 265                                 bool do_unseal,
 266                                 uint8_t *data, size_t length,
 267                                 const DATA_BLOB *sig)
 268 {
 269         uint32_t min_sig_size = 0;
 270         uint8_t header[8];
 271         uint8_t checksum[32];
 272         uint32_t checksum_length = sizeof(checksum_length);
 273         uint8_t _confounder[8];
 274         uint8_t *confounder = NULL;
 275         uint32_t confounder_ofs = 0;
 276         uint8_t seq_num[8];
 277         int ret;
 278
 279         netsec_offset_and_sizes(state,
 280                                 do_unseal,
 281                                 &min_sig_size,
 282                                 NULL,
 283                                 &checksum_length,
 284                                 &confounder_ofs);
 285
 286         if (sig->length < min_sig_size) {
 287                 return NT_STATUS_ACCESS_DENIED;
 288         }
 289
 290         if (do_unseal) {
 291                 confounder = _confounder;
 292                 memcpy(confounder, sig->data+confounder_ofs, 8);
 293         } else {
 294                 confounder = NULL;
 295         }
 296
 297         SETUP_SEQNUM(state, seq_num, !state->initiator);
 298
 299         if (do_unseal) {
 300                 netsec_do_seal(state, seq_num,
 301                                confounder,
 302                                data, length,
 303                                false);
 304         }
 305
 306         netsec_do_sign(state, confounder,
 307                        data, length,
 308                        header, checksum);
 309
 310         ret = memcmp(checksum, sig->data+16, checksum_length);
 311         if (ret != 0) {
 312                 dump_data_pw("calc digest:", checksum, checksum_length);
 313                 dump_data_pw("wire digest:", sig->data+16, checksum_length);
 314                 return NT_STATUS_ACCESS_DENIED;
 315         }
 316
 317         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 318
 319         ret = memcmp(seq_num, sig->data+8, 8);
 320         if (ret != 0) {
 321                 dump_data_pw("calc seq num:", seq_num, 8);
 322                 dump_data_pw("wire seq num:", sig->data+8, 8);
 323                 return NT_STATUS_ACCESS_DENIED;
 324         }
 325
 326         return NT_STATUS_OK;
 327 }
 328
 329 uint32_t netsec_outgoing_sig_size(struct schannel_state *state)
 330 {
 331         uint32_t sig_size = 0;
 332
 333         netsec_offset_and_sizes(state,
 334                                 true,
 335                                 NULL,
 336                                 &sig_size,
 337                                 NULL,
 338                                 NULL);
 339
 340         return sig_size;
 341 }
 342
 343 NTSTATUS netsec_outgoing_packet(struct schannel_state *state,
 344                                 TALLOC_CTX *mem_ctx,
 345                                 bool do_seal,
 346                                 uint8_t *data, size_t length,
 347                                 DATA_BLOB *sig)
 348 {
 349         uint32_t min_sig_size = 0;
 350         uint32_t used_sig_size = 0;
 351         uint8_t header[8];
 352         uint8_t checksum[32];
 353         uint32_t checksum_length = sizeof(checksum_length);
 354         uint8_t _confounder[8];
 355         uint8_t *confounder = NULL;
 356         uint32_t confounder_ofs = 0;
 357         uint8_t seq_num[8];
 358
 359         netsec_offset_and_sizes(state,
 360                                 do_seal,
 361                                 &min_sig_size,
 362                                 &used_sig_size,
 363                                 &checksum_length,
 364                                 &confounder_ofs);
 365
 366         SETUP_SEQNUM(state, seq_num, state->initiator);
 367
 368         if (do_seal) {
 369                 confounder = _confounder;
 370                 generate_random_buffer(confounder, 8);
 371         } else {
 372                 confounder = NULL;
 373         }
 374
 375         netsec_do_sign(state, confounder,
 376                        data, length,
 377                        header, checksum);
 378
 379         if (do_seal) {
 380                 netsec_do_seal(state, seq_num,
 381                                confounder,
 382                                data, length,
 383                                true);
 384         }
 385
 386         netsec_do_seq_num(state, checksum, checksum_length, seq_num);
 387
 388         (*sig) = data_blob_talloc_zero(mem_ctx, used_sig_size);
 389
 390         memcpy(sig->data, header, 8);
 391         memcpy(sig->data+8, seq_num, 8);
 392         memcpy(sig->data+16, checksum, checksum_length);
 393
 394         if (confounder) {
 395                 memcpy(sig->data+confounder_ofs, confounder, 8);
 396         }
 397
 398         dump_data_pw("signature:", sig->data+ 0, 8);
 399         dump_data_pw("seq_num  :", sig->data+ 8, 8);
 400         dump_data_pw("digest   :", sig->data+16, checksum_length);
 401         dump_data_pw("confound :", sig->data+confounder_ofs, 8);
 402
 403         return NT_STATUS_OK;
 404 }