source/libsmb/smb_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Signing Code
   4    Copyright (C) Jeremy Allison 2002.
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
   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 2 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, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 struct smb_basic_signing_context {
  25         DATA_BLOB mac_key;
  26         uint32 send_seq_num;
  27         uint32 reply_seq_num;
  28 };
  29
  30 /***********************************************************
  31  SMB signing - Common code before we set a new signing implementation
  32 ************************************************************/
  33
  34 static BOOL set_smb_signing_common(struct cli_state *cli)
  35 {
  36         if (!cli->sign_info.negotiated_smb_signing
  37             && !cli->sign_info.mandetory_signing) {
  38                 return False;
  39         }
  40
  41         if (cli->sign_info.doing_signing) {
  42                 return False;
  43         }
  44
  45         if (cli->sign_info.free_signing_context)
  46                 cli->sign_info.free_signing_context(cli);
  47
  48         /* These calls are INCOMPATIBLE with SMB signing */
  49         cli->readbraw_supported = False;
  50         cli->writebraw_supported = False;
  51
  52         return True;
  53 }
  54
  55 /***********************************************************
  56  SMB signing - Common code for 'real' implementations
  57 ************************************************************/
  58
  59 static BOOL set_smb_signing_real_common(struct cli_state *cli)
  60 {
  61         if (cli->sign_info.mandetory_signing) {
  62                 DEBUG(5, ("Mandatory SMB signing enabled!\n"));
  63                 cli->sign_info.doing_signing = True;
  64         }
  65
  66         DEBUG(5, ("SMB signing enabled!\n"));
  67
  68         return True;
  69 }
  70
  71 static void mark_packet_signed(struct cli_state *cli)
  72 {
  73         uint16 flags2;
  74         flags2 = SVAL(cli->outbuf,smb_flg2);
  75         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
  76         SSVAL(cli->outbuf,smb_flg2, flags2);
  77 }
  78
  79 static BOOL signing_good(struct cli_state *cli, BOOL good)
  80 {
  81         DEBUG(10, ("got SMB signature of\n"));
  82         dump_data(10,&cli->inbuf[smb_ss_field] , 8);
  83
  84         if (good && !cli->sign_info.doing_signing) {
  85                 cli->sign_info.doing_signing = True;
  86         }
  87
  88         if (!good) {
  89                 if (cli->sign_info.doing_signing) {
  90                         DEBUG(1, ("SMB signature check failed!\n"));
  91                         return False;
  92                 } else {
  93                         DEBUG(3, ("Server did not sign reply correctly\n"));
  94                         cli_free_signing_context(cli);
  95                         return False;
  96                 }
  97         }
  98         return True;
  99 }
 100
 101 /***********************************************************
 102  SMB signing - Simple implementation - calculate a MAC to send.
 103 ************************************************************/
 104
 105 static void cli_simple_sign_outgoing_message(struct cli_state *cli)
 106 {
 107         unsigned char calc_md5_mac[16];
 108         struct MD5Context md5_ctx;
 109         struct smb_basic_signing_context *data = cli->sign_info.signing_context;
 110
 111         /*
 112          * Firstly put the sequence number into the first 4 bytes.
 113          * and zero out the next 4 bytes.
 114          */
 115         SIVAL(cli->outbuf, smb_ss_field,
 116               data->send_seq_num);
 117         SIVAL(cli->outbuf, smb_ss_field + 4, 0);
 118
 119         /* mark the packet as signed - BEFORE we sign it...*/
 120         mark_packet_signed(cli);
 121
 122         /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 123         MD5Init(&md5_ctx);
 124         MD5Update(&md5_ctx, data->mac_key.data,
 125                   data->mac_key.length);
 126         MD5Update(&md5_ctx, cli->outbuf + 4, smb_len(cli->outbuf));
 127         MD5Final(calc_md5_mac, &md5_ctx);
 128
 129         DEBUG(10, ("sent SMB signature of\n"));
 130         dump_data(10, calc_md5_mac, 8);
 131
 132         memcpy(&cli->outbuf[smb_ss_field], calc_md5_mac, 8);
 133
 134 /*      cli->outbuf[smb_ss_field+2]=0;
 135         Uncomment this to test if the remote server actually verifies signitures...*/
 136         data->send_seq_num++;
 137         data->reply_seq_num = data->send_seq_num;
 138         data->send_seq_num++;
 139 }
 140
 141 /***********************************************************
 142  SMB signing - Simple implementation - check a MAC sent by server.
 143 ************************************************************/
 144
 145 static BOOL cli_simple_check_incoming_message(struct cli_state *cli)
 146 {
 147         BOOL good;
 148         unsigned char calc_md5_mac[16];
 149         unsigned char server_sent_mac[8];
 150         unsigned char sequence_buf[8];
 151         struct MD5Context md5_ctx;
 152         struct smb_basic_signing_context *data = cli->sign_info.signing_context;
 153         const size_t offset_end_of_sig = (smb_ss_field + 8);
 154
 155         /*
 156          * Firstly put the sequence number into the first 4 bytes.
 157          * and zero out the next 4 bytes.
 158          */
 159
 160         SIVAL(sequence_buf, 0, data->reply_seq_num);
 161         SIVAL(sequence_buf, 4, 0);
 162
 163         if (smb_len(cli->inbuf) < (offset_end_of_sig - 4)) {
 164                 DEBUG(1, ("Can't check signature on short packet! smb_len = %u\n", smb_len(cli->inbuf)));
 165                 return False;
 166         }
 167
 168         /* get a copy of the server-sent mac */
 169         memcpy(server_sent_mac, &cli->inbuf[smb_ss_field], sizeof(server_sent_mac));
 170
 171         /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 172         MD5Init(&md5_ctx);
 173         MD5Update(&md5_ctx, data->mac_key.data,
 174                   data->mac_key.length);
 175         MD5Update(&md5_ctx, cli->inbuf + 4, smb_ss_field - 4);
 176         MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));
 177
 178         MD5Update(&md5_ctx, cli->inbuf + offset_end_of_sig,
 179                   smb_len(cli->inbuf) - (offset_end_of_sig - 4));
 180         MD5Final(calc_md5_mac, &md5_ctx);
 181
 182         good = (memcmp(server_sent_mac, calc_md5_mac, 8) == 0);
 183
 184         if (!good) {
 185                 DEBUG(5, ("BAD SIG: wanted SMB signature of\n"));
 186                 dump_data(5, calc_md5_mac, 8);
 187
 188                 DEBUG(5, ("BAD SIG: got SMB signature of\n"));
 189                 dump_data(5, server_sent_mac, 8);
 190         }
 191         return signing_good(cli, good);
 192 }
 193
 194 /***********************************************************
 195  SMB signing - Simple implementation - free signing context
 196 ************************************************************/
 197
 198 static void cli_simple_free_signing_context(struct cli_state *cli)
 199 {
 200         struct smb_basic_signing_context *data = cli->sign_info.signing_context;
 201
 202         data_blob_free(&data->mac_key);
 203         SAFE_FREE(cli->sign_info.signing_context);
 204
 205         return;
 206 }
 207
 208 /***********************************************************
 209  SMB signing - Simple implementation - setup the MAC key.
 210 ************************************************************/
 211
 212 BOOL cli_simple_set_signing(struct cli_state *cli, const uchar user_session_key[16], const DATA_BLOB response)
 213 {
 214         struct smb_basic_signing_context *data;
 215
 216         if (!set_smb_signing_common(cli)) {
 217                 return False;
 218         }
 219
 220         if (!set_smb_signing_real_common(cli)) {
 221                 return False;
 222         }
 223
 224         data = smb_xmalloc(sizeof(*data));
 225         cli->sign_info.signing_context = data;
 226
 227         data->mac_key = data_blob(NULL, MIN(response.length + 16, 40));
 228
 229         memcpy(&data->mac_key.data[0], user_session_key, 16);
 230         memcpy(&data->mac_key.data[16],response.data, MIN(response.length, 40 - 16));
 231
 232         /* Initialise the sequence number */
 233         data->send_seq_num = 0;
 234
 235         cli->sign_info.sign_outgoing_message = cli_simple_sign_outgoing_message;
 236         cli->sign_info.check_incoming_message = cli_simple_check_incoming_message;
 237         cli->sign_info.free_signing_context = cli_simple_free_signing_context;
 238
 239         return True;
 240 }
 241
 242 /***********************************************************
 243  SMB signing - NTLMSSP implementation - calculate a MAC to send.
 244 ************************************************************/
 245
 246 static void cli_ntlmssp_sign_outgoing_message(struct cli_state *cli)
 247 {
 248         NTSTATUS nt_status;
 249         DATA_BLOB sig;
 250         NTLMSSP_CLIENT_STATE *ntlmssp_state = cli->sign_info.signing_context;
 251
 252         /* mark the packet as signed - BEFORE we sign it...*/
 253         mark_packet_signed(cli);
 254
 255         nt_status = ntlmssp_client_sign_packet(ntlmssp_state, cli->outbuf + 4,
 256                                                smb_len(cli->outbuf), &sig);
 257
 258         if (!NT_STATUS_IS_OK(nt_status)) {
 259                 DEBUG(0, ("NTLMSSP signing failed with %s\n", nt_errstr(nt_status)));
 260                 return;
 261         }
 262
 263         DEBUG(10, ("sent SMB signature of\n"));
 264         dump_data(10, sig.data, MIN(sig.length, 8));
 265         memcpy(&cli->outbuf[smb_ss_field], sig.data, MIN(sig.length, 8));
 266
 267         data_blob_free(&sig);
 268 }
 269
 270 /***********************************************************
 271  SMB signing - NTLMSSP implementation - check a MAC sent by server.
 272 ************************************************************/
 273
 274 static BOOL cli_ntlmssp_check_incoming_message(struct cli_state *cli)
 275 {
 276         BOOL good;
 277         NTSTATUS nt_status;
 278         DATA_BLOB sig = data_blob(&cli->inbuf[smb_ss_field], 8);
 279
 280         NTLMSSP_CLIENT_STATE *ntlmssp_state = cli->sign_info.signing_context;
 281
 282         nt_status = ntlmssp_client_check_packet(ntlmssp_state, cli->outbuf + 4,
 283                                                 smb_len(cli->outbuf), &sig);
 284
 285         data_blob_free(&sig);
 286
 287         good = NT_STATUS_IS_OK(nt_status);
 288         if (!NT_STATUS_IS_OK(nt_status)) {
 289                 DEBUG(5, ("NTLMSSP signing failed with %s\n", nt_errstr(nt_status)));
 290         }
 291
 292         return signing_good(cli, good);
 293 }
 294
 295 /***********************************************************
 296  SMB signing - NTLMSSP implementation - free signing context
 297 ************************************************************/
 298
 299 static void cli_ntlmssp_free_signing_context(struct cli_state *cli)
 300 {
 301         ntlmssp_client_end((NTLMSSP_CLIENT_STATE **)&cli->sign_info.signing_context);
 302 }
 303
 304 /***********************************************************
 305  SMB signing - NTLMSSP implementation - setup the MAC key.
 306 ************************************************************/
 307
 308 BOOL cli_ntlmssp_set_signing(struct cli_state *cli,
 309                              NTLMSSP_CLIENT_STATE *ntlmssp_state)
 310 {
 311         if (!set_smb_signing_common(cli)) {
 312                 return False;
 313         }
 314
 315         if (!NT_STATUS_IS_OK(ntlmssp_client_sign_init(ntlmssp_state))) {
 316                 return False;
 317         }
 318
 319         if (!set_smb_signing_real_common(cli)) {
 320                 return False;
 321         }
 322
 323         cli->sign_info.signing_context = ntlmssp_state;
 324         ntlmssp_state->ref_count++;
 325
 326         cli->sign_info.sign_outgoing_message = cli_ntlmssp_sign_outgoing_message;
 327         cli->sign_info.check_incoming_message = cli_ntlmssp_check_incoming_message;
 328         cli->sign_info.free_signing_context = cli_ntlmssp_free_signing_context;
 329
 330         return True;
 331 }
 332
 333 /***********************************************************
 334  SMB signing - NULL implementation - calculate a MAC to send.
 335 ************************************************************/
 336
 337 static void cli_null_sign_outgoing_message(struct cli_state *cli)
 338 {
 339         /* we can't zero out the sig, as we might be trying to send a
 340            session request - which is NBT-level, not SMB level and doesn't
 341            have the field */
 342         return;
 343 }
 344
 345 /***********************************************************
 346  SMB signing - NULL implementation - check a MAC sent by server.
 347 ************************************************************/
 348
 349 static BOOL cli_null_check_incoming_message(struct cli_state *cli)
 350 {
 351         return True;
 352 }
 353
 354 /***********************************************************
 355  SMB signing - NULL implementation - free signing context
 356 ************************************************************/
 357
 358 static void cli_null_free_signing_context(struct cli_state *cli)
 359 {
 360         return;
 361 }
 362
 363 /**
 364  SMB signing - NULL implementation - setup the MAC key.
 365
 366  @note Used as an initialisation only - it will not correctly
 367        shut down a real signing mechanism
 368 */
 369
 370 BOOL cli_null_set_signing(struct cli_state *cli)
 371 {
 372         cli->sign_info.signing_context = NULL;
 373
 374         cli->sign_info.sign_outgoing_message = cli_null_sign_outgoing_message;
 375         cli->sign_info.check_incoming_message = cli_null_check_incoming_message;
 376         cli->sign_info.free_signing_context = cli_null_free_signing_context;
 377
 378         return True;
 379 }
 380
 381 /***********************************************************
 382  SMB signing - TEMP implementation - calculate a MAC to send.
 383 ************************************************************/
 384
 385 static void cli_temp_sign_outgoing_message(struct cli_state *cli)
 386 {
 387         /* mark the packet as signed - BEFORE we sign it...*/
 388         mark_packet_signed(cli);
 389
 390         /* I wonder what BSRSPYL stands for - but this is what MS
 391            actually sends! */
 392         memcpy(&cli->outbuf[smb_ss_field], "BSRSPYL ", 8);
 393         return;
 394 }
 395
 396 /***********************************************************
 397  SMB signing - TEMP implementation - check a MAC sent by server.
 398 ************************************************************/
 399
 400 static BOOL cli_temp_check_incoming_message(struct cli_state *cli)
 401 {
 402         return True;
 403 }
 404
 405 /***********************************************************
 406  SMB signing - TEMP implementation - free signing context
 407 ************************************************************/
 408
 409 static void cli_temp_free_signing_context(struct cli_state *cli)
 410 {
 411         return;
 412 }
 413
 414 /***********************************************************
 415  SMB signing - NULL implementation - setup the MAC key.
 416 ************************************************************/
 417
 418 BOOL cli_temp_set_signing(struct cli_state *cli)
 419 {
 420         if (!set_smb_signing_common(cli)) {
 421                 return False;
 422         }
 423
 424         cli->sign_info.signing_context = NULL;
 425
 426         cli->sign_info.sign_outgoing_message = cli_temp_sign_outgoing_message;
 427         cli->sign_info.check_incoming_message = cli_temp_check_incoming_message;
 428         cli->sign_info.free_signing_context = cli_temp_free_signing_context;
 429
 430         return True;
 431 }
 432
 433 /**
 434  * Free the signing context
 435  */
 436
 437 void cli_free_signing_context(struct cli_state *cli)
 438 {
 439         if (cli->sign_info.free_signing_context)
 440                 cli->sign_info.free_signing_context(cli);
 441
 442         cli_null_set_signing(cli);
 443 }
 444
 445 /**
 446  * Sign a packet with the current mechanism
 447  */
 448
 449 void cli_caclulate_sign_mac(struct cli_state *cli)
 450 {
 451         cli->sign_info.sign_outgoing_message(cli);
 452 }
 453
 454 /**
 455  * Check a packet with the current mechanism
 456  * @return False if we had an established signing connection
 457  *         which had a back checksum, True otherwise
 458  */
 459
 460 BOOL cli_check_sign_mac(struct cli_state *cli)
 461 {
 462         BOOL good;
 463         good = cli->sign_info.check_incoming_message(cli);
 464
 465         if (!good) {
 466                 if (cli->sign_info.doing_signing) {
 467                         return False;
 468                 } else {
 469                         cli_free_signing_context(cli);
 470                 }
 471         }
 472
 473         return True;
 474 }
 475