source/libcli/raw/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    Copyright (C) James J Myers <myersjj@samba.org> 2003
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include "smb.h"
  24 #include "libcli/raw/libcliraw.h"
  25 #include "lib/crypto/crypto.h"
  26 #include "param/param.h"
  27
  28 /***********************************************************
  29  SMB signing - Common code before we set a new signing implementation
  30 ************************************************************/
  31 bool set_smb_signing_common(struct smb_signing_context *sign_info)
  32 {
  33         if (sign_info->doing_signing) {
  34                 DEBUG(5, ("SMB Signing already in progress, so we don't start it again\n"));
  35                 return false;
  36         }
  37
  38         if (!sign_info->allow_smb_signing) {
  39                 DEBUG(5, ("SMB Signing has been locally disabled\n"));
  40                 return false;
  41         }
  42
  43         return true;
  44 }
  45
  46 /***********************************************************
  47  SMB signing - Common code before we set a new signing implementation
  48 ************************************************************/
  49 static bool smbcli_set_smb_signing_common(struct smbcli_transport *transport)
  50 {
  51         if (!set_smb_signing_common(&transport->negotiate.sign_info)) {
  52                 return false;
  53         }
  54
  55         if (!(transport->negotiate.sec_mode &
  56               (NEGOTIATE_SECURITY_SIGNATURES_REQUIRED|NEGOTIATE_SECURITY_SIGNATURES_ENABLED))) {
  57                 DEBUG(5, ("SMB Signing is not negotiated by the peer\n"));
  58                 return false;
  59         }
  60
  61         /* These calls are INCOMPATIBLE with SMB signing */
  62         transport->negotiate.readbraw_supported = false;
  63         transport->negotiate.writebraw_supported = false;
  64
  65         return true;
  66 }
  67
  68 void mark_packet_signed(struct request_buffer *out)
  69 {
  70         uint16_t flags2;
  71         flags2 = SVAL(out->hdr, HDR_FLG2);
  72         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
  73         SSVAL(out->hdr, HDR_FLG2, flags2);
  74 }
  75
  76 bool signing_good(struct smb_signing_context *sign_info,
  77                          unsigned int seq, bool good)
  78 {
  79         if (good) {
  80                 if (!sign_info->doing_signing) {
  81                         DEBUG(5, ("Seen valid packet, so turning signing on\n"));
  82                         sign_info->doing_signing = true;
  83                 }
  84                 if (!sign_info->seen_valid) {
  85                         DEBUG(5, ("Seen valid packet, so marking signing as 'seen valid'\n"));
  86                         sign_info->seen_valid = true;
  87                 }
  88         } else {
  89                 if (!sign_info->seen_valid) {
  90                         /* If we have never seen a good packet, just turn it off */
  91                         DEBUG(5, ("signing_good: signing negotiated but not required and peer\n"
  92                                   "isn't sending correct signatures. Turning off.\n"));
  93                         smbcli_set_signing_off(sign_info);
  94                         return true;
  95                 } else {
  96                         /* bad packet after signing started - fail and disconnect. */
  97                         DEBUG(0, ("signing_good: BAD SIG: seq %u\n", seq));
  98                         return false;
  99                 }
 100         }
 101         return true;
 102 }
 103
 104 void sign_outgoing_message(struct request_buffer *out, DATA_BLOB *mac_key, unsigned int seq_num)
 105 {
 106         uint8_t calc_md5_mac[16];
 107         struct MD5Context md5_ctx;
 108
 109         /*
 110          * Firstly put the sequence number into the first 4 bytes.
 111          * and zero out the next 4 bytes.
 112          */
 113         SIVAL(out->hdr, HDR_SS_FIELD, seq_num);
 114         SIVAL(out->hdr, HDR_SS_FIELD + 4, 0);
 115
 116         /* mark the packet as signed - BEFORE we sign it...*/
 117         mark_packet_signed(out);
 118
 119         /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 120         MD5Init(&md5_ctx);
 121         MD5Update(&md5_ctx, mac_key->data, mac_key->length);
 122         MD5Update(&md5_ctx,
 123                   out->buffer + NBT_HDR_SIZE,
 124                   out->size - NBT_HDR_SIZE);
 125         MD5Final(calc_md5_mac, &md5_ctx);
 126
 127         memcpy(&out->hdr[HDR_SS_FIELD], calc_md5_mac, 8);
 128
 129         DEBUG(5, ("sign_outgoing_message: SENT SIG (seq: %d): sent SMB signature of\n",
 130                   seq_num));
 131         dump_data(5, calc_md5_mac, 8);
 132 /*      req->out.hdr[HDR_SS_FIELD+2]=0;
 133         Uncomment this to test if the remote server actually verifies signitures...*/
 134 }
 135
 136 bool check_signed_incoming_message(struct request_buffer *in, DATA_BLOB *mac_key, uint_t seq_num)
 137 {
 138         bool good;
 139         uint8_t calc_md5_mac[16];
 140         uint8_t *server_sent_mac;
 141         uint8_t sequence_buf[8];
 142         struct MD5Context md5_ctx;
 143         const size_t offset_end_of_sig = (HDR_SS_FIELD + 8);
 144         int i;
 145         const int sign_range = 0;
 146
 147         /* room enough for the signature? */
 148         if (in->size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
 149                 return false;
 150         }
 151
 152         if (!mac_key->length) {
 153                 /* NO key yet */
 154                 return false;
 155         }
 156
 157         /* its quite bogus to be guessing sequence numbers, but very useful
 158            when debugging signing implementations */
 159         for (i = 0-sign_range; i <= 0+sign_range; i++) {
 160                 /*
 161                  * Firstly put the sequence number into the first 4 bytes.
 162                  * and zero out the next 4 bytes.
 163                  */
 164                 SIVAL(sequence_buf, 0, seq_num + i);
 165                 SIVAL(sequence_buf, 4, 0);
 166
 167                 /* get a copy of the server-sent mac */
 168                 server_sent_mac = &in->hdr[HDR_SS_FIELD];
 169
 170                 /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 171                 MD5Init(&md5_ctx);
 172                 MD5Update(&md5_ctx, mac_key->data,
 173                           mac_key->length);
 174                 MD5Update(&md5_ctx, in->hdr, HDR_SS_FIELD);
 175                 MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));
 176
 177                 MD5Update(&md5_ctx, in->hdr + offset_end_of_sig,
 178                           in->size - NBT_HDR_SIZE - (offset_end_of_sig));
 179                 MD5Final(calc_md5_mac, &md5_ctx);
 180
 181                 good = (memcmp(server_sent_mac, calc_md5_mac, 8) == 0);
 182
 183                 if (i == 0) {
 184                         if (!good) {
 185                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): wanted SMB signature of\n", seq_num + i));
 186                                 dump_data(5, calc_md5_mac, 8);
 187
 188                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 189                                 dump_data(5, server_sent_mac, 8);
 190                         } else {
 191                                 DEBUG(15, ("check_signed_incoming_message: GOOD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 192                                 dump_data(5, server_sent_mac, 8);
 193                         }
 194                 }
 195
 196                 if (good) break;
 197         }
 198
 199         if (good && i != 0) {
 200                 DEBUG(0,("SIGNING OFFSET %d (should be %d)\n", i, seq_num));
 201         }
 202
 203         return good;
 204 }
 205
 206 static void smbcli_req_allocate_seq_num(struct smbcli_request *req)
 207 {
 208         req->seq_num = req->transport->negotiate.sign_info.next_seq_num;
 209
 210         /* some requests (eg. NTcancel) are one way, and the sequence number
 211            should be increased by 1 not 2 */
 212         if (req->sign_single_increment) {
 213                 req->transport->negotiate.sign_info.next_seq_num += 1;
 214         } else {
 215                 req->transport->negotiate.sign_info.next_seq_num += 2;
 216         }
 217 }
 218
 219 /***********************************************************
 220  SMB signing - Simple implementation - calculate a MAC to send.
 221 ************************************************************/
 222 void smbcli_request_calculate_sign_mac(struct smbcli_request *req)
 223 {
 224 #if 0
 225         /* enable this when packet signing is preventing you working out why valgrind
 226            says that data is uninitialised */
 227         file_save("pkt.dat", req->out.buffer, req->out.size);
 228 #endif
 229
 230         switch (req->transport->negotiate.sign_info.signing_state) {
 231         case SMB_SIGNING_ENGINE_OFF:
 232                 break;
 233
 234         case SMB_SIGNING_ENGINE_BSRSPYL:
 235                 /* mark the packet as signed - BEFORE we sign it...*/
 236                 mark_packet_signed(&req->out);
 237
 238                 /* I wonder what BSRSPYL stands for - but this is what MS
 239                    actually sends! */
 240                 memcpy((req->out.hdr + HDR_SS_FIELD), "BSRSPYL ", 8);
 241                 break;
 242
 243         case SMB_SIGNING_ENGINE_ON:
 244
 245                 smbcli_req_allocate_seq_num(req);
 246                 sign_outgoing_message(&req->out,
 247                                       &req->transport->negotiate.sign_info.mac_key,
 248                                       req->seq_num);
 249                 break;
 250         }
 251         return;
 252 }
 253
 254
 255 /**
 256  SMB signing - NULL implementation
 257
 258  @note Used as an initialisation only - it will not correctly
 259        shut down a real signing mechanism
 260 */
 261 bool smbcli_set_signing_off(struct smb_signing_context *sign_info)
 262 {
 263         DEBUG(5, ("Shutdown SMB signing\n"));
 264         sign_info->doing_signing = false;
 265         sign_info->next_seq_num = 0;
 266         data_blob_free(&sign_info->mac_key);
 267         sign_info->signing_state = SMB_SIGNING_ENGINE_OFF;
 268         return true;
 269 }
 270
 271 /**
 272  SMB signing - TEMP implementation - setup the MAC key.
 273
 274 */
 275 bool smbcli_temp_set_signing(struct smbcli_transport *transport)
 276 {
 277         if (!smbcli_set_smb_signing_common(transport)) {
 278                 return false;
 279         }
 280         DEBUG(5, ("BSRSPYL SMB signing enabled\n"));
 281         smbcli_set_signing_off(&transport->negotiate.sign_info);
 282
 283         transport->negotiate.sign_info.mac_key = data_blob(NULL, 0);
 284         transport->negotiate.sign_info.signing_state = SMB_SIGNING_ENGINE_BSRSPYL;
 285
 286         return true;
 287 }
 288
 289 /***********************************************************
 290  SMB signing - Simple implementation - check a MAC sent by server.
 291 ************************************************************/
 292 /**
 293  * Check a packet supplied by the server.
 294  * @return false if we had an established signing connection
 295  *         which had a back checksum, true otherwise
 296  */
 297 bool smbcli_request_check_sign_mac(struct smbcli_request *req)
 298 {
 299         bool good;
 300
 301         switch (req->transport->negotiate.sign_info.signing_state)
 302         {
 303         case SMB_SIGNING_ENGINE_OFF:
 304                 return true;
 305         case SMB_SIGNING_ENGINE_BSRSPYL:
 306         case SMB_SIGNING_ENGINE_ON:
 307         {
 308                 if (req->in.size < (HDR_SS_FIELD + 8)) {
 309                         return false;
 310                 } else {
 311                         good = check_signed_incoming_message(&req->in,
 312                                                              &req->transport->negotiate.sign_info.mac_key,
 313                                                              req->seq_num+1);
 314
 315                         return signing_good(&req->transport->negotiate.sign_info,
 316                                             req->seq_num+1, good);
 317                 }
 318         }
 319         }
 320         return false;
 321 }
 322
 323
 324 /***********************************************************
 325  SMB signing - Simple implementation - setup the MAC key.
 326 ************************************************************/
 327 bool smbcli_simple_set_signing(TALLOC_CTX *mem_ctx,
 328                                struct smb_signing_context *sign_info,
 329                                const DATA_BLOB *user_session_key,
 330                                const DATA_BLOB *response)
 331 {
 332         if (sign_info->mandatory_signing) {
 333                 DEBUG(5, ("Mandatory SMB signing enabled!\n"));
 334         }
 335
 336         DEBUG(5, ("SMB signing enabled!\n"));
 337
 338         if (response && response->length) {
 339                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, response->length + user_session_key->length);
 340         } else {
 341                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, user_session_key->length);
 342         }
 343
 344         memcpy(&sign_info->mac_key.data[0], user_session_key->data, user_session_key->length);
 345
 346         if (response && response->length) {
 347                 memcpy(&sign_info->mac_key.data[user_session_key->length],response->data, response->length);
 348         }
 349
 350         dump_data_pw("Started Signing with key:\n", sign_info->mac_key.data, sign_info->mac_key.length);
 351
 352         /* Initialise the sequence number */
 353         sign_info->next_seq_num = 0;
 354
 355         sign_info->signing_state = SMB_SIGNING_ENGINE_ON;
 356
 357         return true;
 358 }
 359
 360
 361 /***********************************************************
 362  SMB signing - Simple implementation - setup the MAC key.
 363 ************************************************************/
 364 bool smbcli_transport_simple_set_signing(struct smbcli_transport *transport,
 365                                          const DATA_BLOB user_session_key,
 366                                          const DATA_BLOB response)
 367 {
 368         if (!smbcli_set_smb_signing_common(transport)) {
 369                 return false;
 370         }
 371
 372         return smbcli_simple_set_signing(transport,
 373                                          &transport->negotiate.sign_info,
 374                                          &user_session_key,
 375                                          &response);
 376 }
 377
 378
 379 bool smbcli_init_signing(struct smbcli_transport *transport)
 380 {
 381         transport->negotiate.sign_info.mac_key = data_blob(NULL, 0);
 382         if (!smbcli_set_signing_off(&transport->negotiate.sign_info)) {
 383                 return false;
 384         }
 385
 386         switch (lp_client_signing(global_loadparm)) {
 387         case SMB_SIGNING_OFF:
 388                 transport->negotiate.sign_info.allow_smb_signing = false;
 389                 break;
 390         case SMB_SIGNING_SUPPORTED:
 391         case SMB_SIGNING_AUTO:
 392                 transport->negotiate.sign_info.allow_smb_signing = true;
 393                 break;
 394         case SMB_SIGNING_REQUIRED:
 395                 transport->negotiate.sign_info.allow_smb_signing = true;
 396                 transport->negotiate.sign_info.mandatory_signing = true;
 397                 break;
 398         }
 399         return true;
 400 }