libcli/smb/smb_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Signing Code
   4    Copyright (C) Jeremy Allison 2003.
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
   6    Copyright (C) Stefan Metzmacher 2009
   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 "../lib/crypto/crypto.h"
  24 #include "smb_common.h"
  25 #include "smb_signing.h"
  26
  27 /* Used by the SMB signing functions. */
  28
  29 struct smb_signing_state {
  30         /* is signing localy allowed */
  31         bool allowed;
  32
  33         /* is signing localy desired */
  34         bool desired;
  35
  36         /* is signing localy mandatory */
  37         bool mandatory;
  38
  39         /* is signing negotiated by the peer */
  40         bool negotiated;
  41
  42         bool active; /* Have I ever seen a validly signed packet? */
  43
  44         /* mac_key.length > 0 means signing is started */
  45         DATA_BLOB mac_key;
  46
  47         /* the next expected seqnum */
  48         uint32_t seqnum;
  49
  50         TALLOC_CTX *mem_ctx;
  51         void *(*alloc_fn)(TALLOC_CTX *mem_ctx, size_t len);
  52         void (*free_fn)(TALLOC_CTX *mem_ctx, void *ptr);
  53 };
  54
  55 static void smb_signing_reset_info(struct smb_signing_state *si)
  56 {
  57         si->active = false;
  58         si->seqnum = 0;
  59
  60         if (si->free_fn) {
  61                 si->free_fn(si->mem_ctx, si->mac_key.data);
  62         } else {
  63                 talloc_free(si->mac_key.data);
  64         }
  65         si->mac_key.data = NULL;
  66         si->mac_key.length = 0;
  67 }
  68
  69 struct smb_signing_state *smb_signing_init_ex(TALLOC_CTX *mem_ctx,
  70                                               bool allowed,
  71                                               bool desired,
  72                                               bool mandatory,
  73                                               void *(*alloc_fn)(TALLOC_CTX *, size_t),
  74                                               void (*free_fn)(TALLOC_CTX *, void *))
  75 {
  76         struct smb_signing_state *si;
  77
  78         if (alloc_fn) {
  79                 void *p = alloc_fn(mem_ctx, sizeof(struct smb_signing_state));
  80                 if (p == NULL) {
  81                         return NULL;
  82                 }
  83                 memset(p, 0, sizeof(struct smb_signing_state));
  84                 si = (struct smb_signing_state *)p;
  85                 si->mem_ctx = mem_ctx;
  86                 si->alloc_fn = alloc_fn;
  87                 si->free_fn = free_fn;
  88         } else {
  89                 si = talloc_zero(mem_ctx, struct smb_signing_state);
  90                 if (si == NULL) {
  91                         return NULL;
  92                 }
  93         }
  94
  95         if (mandatory) {
  96                 desired = true;
  97         }
  98
  99         if (desired) {
 100                 allowed = true;
 101         }
 102
 103         si->allowed = allowed;
 104         si->desired = desired;
 105         si->mandatory = mandatory;
 106
 107         return si;
 108 }
 109
 110 struct smb_signing_state *smb_signing_init(TALLOC_CTX *mem_ctx,
 111                                            bool allowed,
 112                                            bool desired,
 113                                            bool mandatory)
 114 {
 115         return smb_signing_init_ex(mem_ctx, allowed, desired, mandatory,
 116                                    NULL, NULL);
 117 }
 118
 119 static bool smb_signing_good(struct smb_signing_state *si,
 120                              bool good, uint32_t seq)
 121 {
 122         if (good) {
 123                 if (!si->active) {
 124                         si->active = true;
 125                 }
 126                 return true;
 127         }
 128
 129         if (!si->mandatory && !si->active) {
 130                 /* Non-mandatory signing - just turn off if this is the first bad packet.. */
 131                 DEBUG(5, ("smb_signing_good: signing negotiated but not required and peer\n"
 132                           "isn't sending correct signatures. Turning off.\n"));
 133                 smb_signing_reset_info(si);
 134                 return true;
 135         }
 136
 137         /* Mandatory signing or bad packet after signing started - fail and disconnect. */
 138         DEBUG(0, ("smb_signing_good: BAD SIG: seq %u\n", (unsigned int)seq));
 139         return false;
 140 }
 141
 142 static void smb_signing_md5(const DATA_BLOB *mac_key,
 143                             const uint8_t *hdr, size_t len,
 144                             uint32_t seq_number,
 145                             uint8_t calc_md5_mac[16])
 146 {
 147         const size_t offset_end_of_sig = (HDR_SS_FIELD + 8);
 148         uint8_t sequence_buf[8];
 149         MD5_CTX md5_ctx;
 150
 151         /*
 152          * Firstly put the sequence number into the first 4 bytes.
 153          * and zero out the next 4 bytes.
 154          *
 155          * We do this here, to avoid modifying the packet.
 156          */
 157
 158         DEBUG(10,("smb_signing_md5: sequence number %u\n", seq_number ));
 159
 160         SIVAL(sequence_buf, 0, seq_number);
 161         SIVAL(sequence_buf, 4, 0);
 162
 163         /* Calculate the 16 byte MAC - but don't alter the data in the
 164            incoming packet.
 165
 166            This makes for a bit of fussing about, but it's not too bad.
 167         */
 168         MD5Init(&md5_ctx);
 169
 170         /* intialise with the key */
 171         MD5Update(&md5_ctx, mac_key->data, mac_key->length);
 172
 173         /* copy in the first bit of the SMB header */
 174         MD5Update(&md5_ctx, hdr, HDR_SS_FIELD);
 175
 176         /* copy in the sequence number, instead of the signature */
 177         MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));
 178
 179         /* copy in the rest of the packet in, skipping the signature */
 180         MD5Update(&md5_ctx, hdr + offset_end_of_sig,
 181                   len - (offset_end_of_sig));
 182
 183         /* calculate the MD5 sig */
 184         MD5Final(calc_md5_mac, &md5_ctx);
 185 }
 186
 187 uint32_t smb_signing_next_seqnum(struct smb_signing_state *si, bool oneway)
 188 {
 189         uint32_t seqnum;
 190
 191         if (si->mac_key.length == 0) {
 192                 return 0;
 193         }
 194
 195         seqnum = si->seqnum;
 196         if (oneway) {
 197                 si->seqnum += 1;
 198         } else {
 199                 si->seqnum += 2;
 200         }
 201
 202         return seqnum;
 203 }
 204
 205 void smb_signing_cancel_reply(struct smb_signing_state *si, bool oneway)
 206 {
 207         if (si->mac_key.length == 0) {
 208                 return;
 209         }
 210
 211         if (oneway) {
 212                 si->seqnum -= 1;
 213         } else {
 214                 si->seqnum -= 2;
 215         }
 216 }
 217
 218 void smb_signing_sign_pdu(struct smb_signing_state *si,
 219                           uint8_t *outhdr, size_t len,
 220                           uint32_t seqnum)
 221 {
 222         uint8_t calc_md5_mac[16];
 223         uint8_t com;
 224         uint8_t flags;
 225
 226         if (si->mac_key.length == 0) {
 227                 if (!si->negotiated) {
 228                         return;
 229                 }
 230         }
 231
 232         /* JRA Paranioa test - we should be able to get rid of this... */
 233         if (len < (HDR_SS_FIELD + 8)) {
 234                 DEBUG(1,("smb_signing_sign_pdu: Logic error. "
 235                          "Can't check signature on short packet! smb_len = %u\n",
 236                          (unsigned)len));
 237                 abort();
 238         }
 239
 240         com = SVAL(outhdr, HDR_COM);
 241         flags = SVAL(outhdr, HDR_FLG);
 242
 243         if (!(flags & FLAG_REPLY)) {
 244                 uint16_t flags2 = SVAL(outhdr, HDR_FLG2);
 245                 /*
 246                  * If this is a request, specify what is
 247                  * supported or required by the client
 248                  */
 249                 if (si->negotiated && si->desired) {
 250                         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
 251                 }
 252                 if (si->negotiated && si->mandatory) {
 253                         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES_REQUIRED;
 254                 }
 255                 SSVAL(outhdr, HDR_FLG2, flags2);
 256         }
 257
 258         if (si->mac_key.length == 0) {
 259                 /* I wonder what BSRSPYL stands for - but this is what MS
 260                    actually sends! */
 261                 if (com == SMBsesssetupX) {
 262                         memcpy(calc_md5_mac, "BSRSPYL ", 8);
 263                 } else {
 264                         memset(calc_md5_mac, 0, 8);
 265                 }
 266         } else {
 267                 smb_signing_md5(&si->mac_key, outhdr, len,
 268                                 seqnum, calc_md5_mac);
 269         }
 270
 271         DEBUG(10, ("smb_signing_sign_pdu: sent SMB signature of\n"));
 272         dump_data(10, calc_md5_mac, 8);
 273
 274         memcpy(&outhdr[HDR_SS_FIELD], calc_md5_mac, 8);
 275
 276 /*      outhdr[HDR_SS_FIELD+2]=0;
 277         Uncomment this to test if the remote server actually verifies signatures...*/
 278 }
 279
 280 bool smb_signing_check_pdu(struct smb_signing_state *si,
 281                            const uint8_t *inhdr, size_t len,
 282                            uint32_t seqnum)
 283 {
 284         bool good;
 285         uint8_t calc_md5_mac[16];
 286         const uint8_t *reply_sent_mac;
 287
 288         if (si->mac_key.length == 0) {
 289                 return true;
 290         }
 291
 292         if (len < (HDR_SS_FIELD + 8)) {
 293                 DEBUG(1,("smb_signing_check_pdu: Can't check signature "
 294                          "on short packet! smb_len = %u\n",
 295                          (unsigned)len));
 296                 return false;
 297         }
 298
 299         smb_signing_md5(&si->mac_key, inhdr, len,
 300                         seqnum, calc_md5_mac);
 301
 302         reply_sent_mac = &inhdr[HDR_SS_FIELD];
 303         good = (memcmp(reply_sent_mac, calc_md5_mac, 8) == 0);
 304
 305         if (!good) {
 306                 int i;
 307                 const int sign_range = 5;
 308
 309                 DEBUG(5, ("smb_signing_check_pdu: BAD SIG: wanted SMB signature of\n"));
 310                 dump_data(5, calc_md5_mac, 8);
 311
 312                 DEBUG(5, ("smb_signing_check_pdu: BAD SIG: got SMB signature of\n"));
 313                 dump_data(5, reply_sent_mac, 8);
 314
 315                 for (i = -sign_range; i < sign_range; i++) {
 316                         smb_signing_md5(&si->mac_key, inhdr, len,
 317                                         seqnum+i, calc_md5_mac);
 318                         if (memcmp(reply_sent_mac, calc_md5_mac, 8) == 0) {
 319                                 DEBUG(0,("smb_signing_check_pdu: "
 320                                          "out of seq. seq num %u matches. "
 321                                          "We were expecting seq %u\n",
 322                                          (unsigned int)seqnum+i,
 323                                          (unsigned int)seqnum));
 324                                 break;
 325                         }
 326                 }
 327         } else {
 328                 DEBUG(10, ("smb_signing_check_pdu: seq %u: "
 329                            "got good SMB signature of\n",
 330                            (unsigned int)seqnum));
 331                 dump_data(10, reply_sent_mac, 8);
 332         }
 333
 334         return smb_signing_good(si, good, seqnum);
 335 }
 336
 337 bool smb_signing_activate(struct smb_signing_state *si,
 338                           const DATA_BLOB user_session_key,
 339                           const DATA_BLOB response)
 340 {
 341         size_t len;
 342         off_t ofs;
 343
 344         if (!user_session_key.length) {
 345                 return false;
 346         }
 347
 348         if (!si->negotiated) {
 349                 return false;
 350         }
 351
 352         if (si->active) {
 353                 return false;
 354         }
 355
 356         if (si->mac_key.length > 0) {
 357                 return false;
 358         }
 359
 360         smb_signing_reset_info(si);
 361
 362         len = response.length + user_session_key.length;
 363         if (si->alloc_fn) {
 364                 si->mac_key.data = (uint8_t *)si->alloc_fn(si->mem_ctx, len);
 365                 if (si->mac_key.data == NULL) {
 366                         return false;
 367                 }
 368         } else {
 369                 si->mac_key.data = (uint8_t *)talloc_size(si, len);
 370                 if (si->mac_key.data == NULL) {
 371                         return false;
 372                 }
 373         }
 374         si->mac_key.length = len;
 375
 376         ofs = 0;
 377         memcpy(&si->mac_key.data[ofs], user_session_key.data, user_session_key.length);
 378
 379         DEBUG(10, ("smb_signing_activate: user_session_key\n"));
 380         dump_data(10, user_session_key.data, user_session_key.length);
 381
 382         if (response.length) {
 383                 ofs = user_session_key.length;
 384                 memcpy(&si->mac_key.data[ofs], response.data, response.length);
 385                 DEBUG(10, ("smb_signing_activate: response_data\n"));
 386                 dump_data(10, response.data, response.length);
 387         } else {
 388                 DEBUG(10, ("smb_signing_activate: NULL response_data\n"));
 389         }
 390
 391         dump_data_pw("smb_signing_activate: mac key is:\n",
 392                      si->mac_key.data, si->mac_key.length);
 393
 394         /* Initialise the sequence number */
 395         si->seqnum = 2;
 396
 397         return true;
 398 }
 399
 400 bool smb_signing_is_active(struct smb_signing_state *si)
 401 {
 402         return si->active;
 403 }
 404
 405 bool smb_signing_is_allowed(struct smb_signing_state *si)
 406 {
 407         return si->allowed;
 408 }
 409
 410 bool smb_signing_is_desired(struct smb_signing_state *si)
 411 {
 412         return si->desired;
 413 }
 414
 415 bool smb_signing_is_mandatory(struct smb_signing_state *si)
 416 {
 417         return si->mandatory;
 418 }
 419
 420 bool smb_signing_set_negotiated(struct smb_signing_state *si,
 421                                 bool allowed, bool mandatory)
 422 {
 423         if (si->active) {
 424                 return true;
 425         }
 426
 427         if (!si->allowed && mandatory) {
 428                 return false;
 429         }
 430
 431         if (si->mandatory && !allowed) {
 432                 return false;
 433         }
 434
 435         if (si->mandatory) {
 436                 si->negotiated = true;
 437                 return true;
 438         }
 439
 440         if (mandatory) {
 441                 si->negotiated = true;
 442                 return true;
 443         }
 444
 445         if (!si->desired) {
 446                 si->negotiated = false;
 447                 return true;
 448         }
 449
 450         if (si->desired && allowed) {
 451                 si->negotiated = true;
 452                 return true;
 453         }
 454
 455         si->negotiated = false;
 456         return true;
 457 }
 458
 459 bool smb_signing_is_negotiated(struct smb_signing_state *si)
 460 {
 461         return si->negotiated;
 462 }
 463
 464 void smb_key_derivation(const uint8_t *KI, size_t KI_len,
 465                         uint8_t KO[16])
 466 {
 467         static const uint8_t SSKeyHash[256] = {
 468                 0x53, 0x65, 0x63, 0x75, 0x72, 0x69, 0x74, 0x79,
 469                 0x20, 0x53, 0x69, 0x67, 0x6e, 0x61, 0x74, 0x75,
 470                 0x72, 0x65, 0x20, 0x4b, 0x65, 0x79, 0x20, 0x55,
 471                 0x70, 0x67, 0x72, 0x61, 0x64, 0x65, 0x79, 0x07,
 472                 0x6e, 0x28, 0x2e, 0x69, 0x88, 0x10, 0xb3, 0xdb,
 473                 0x01, 0x55, 0x72, 0xfb, 0x74, 0x14, 0xfb, 0xc4,
 474                 0xc5, 0xaf, 0x3b, 0x41, 0x65, 0x32, 0x17, 0xba,
 475                 0xa3, 0x29, 0x08, 0xc1, 0xde, 0x16, 0x61, 0x7e,
 476                 0x66, 0x98, 0xa4, 0x0b, 0xfe, 0x06, 0x83, 0x53,
 477                 0x4d, 0x05, 0xdf, 0x6d, 0xa7, 0x51, 0x10, 0x73,
 478                 0xc5, 0x50, 0xdc, 0x5e, 0xf8, 0x21, 0x46, 0xaa,
 479                 0x96, 0x14, 0x33, 0xd7, 0x52, 0xeb, 0xaf, 0x1f,
 480                 0xbf, 0x36, 0x6c, 0xfc, 0xb7, 0x1d, 0x21, 0x19,
 481                 0x81, 0xd0, 0x6b, 0xfa, 0x77, 0xad, 0xbe, 0x18,
 482                 0x78, 0xcf, 0x10, 0xbd, 0xd8, 0x78, 0xf7, 0xd3,
 483                 0xc6, 0xdf, 0x43, 0x32, 0x19, 0xd3, 0x9b, 0xa8,
 484                 0x4d, 0x9e, 0xaa, 0x41, 0xaf, 0xcb, 0xc6, 0xb9,
 485                 0x34, 0xe7, 0x48, 0x25, 0xd4, 0x88, 0xc4, 0x51,
 486                 0x60, 0x38, 0xd9, 0x62, 0xe8, 0x8d, 0x5b, 0x83,
 487                 0x92, 0x7f, 0xb5, 0x0e, 0x1c, 0x2d, 0x06, 0x91,
 488                 0xc3, 0x75, 0xb3, 0xcc, 0xf8, 0xf7, 0x92, 0x91,
 489                 0x0b, 0x3d, 0xa1, 0x10, 0x5b, 0xd5, 0x0f, 0xa8,
 490                 0x3f, 0x5d, 0x13, 0x83, 0x0a, 0x6b, 0x72, 0x93,
 491                 0x14, 0x59, 0xd5, 0xab, 0xde, 0x26, 0x15, 0x6d,
 492                 0x60, 0x67, 0x71, 0x06, 0x6e, 0x3d, 0x0d, 0xa7,
 493                 0xcb, 0x70, 0xe9, 0x08, 0x5c, 0x99, 0xfa, 0x0a,
 494                 0x5f, 0x3d, 0x44, 0xa3, 0x8b, 0xc0, 0x8d, 0xda,
 495                 0xe2, 0x68, 0xd0, 0x0d, 0xcd, 0x7f, 0x3d, 0xf8,
 496                 0x73, 0x7e, 0x35, 0x7f, 0x07, 0x02, 0x0a, 0xb5,
 497                 0xe9, 0xb7, 0x87, 0xfb, 0xa1, 0xbf, 0xcb, 0x32,
 498                 0x31, 0x66, 0x09, 0x48, 0x88, 0xcc, 0x18, 0xa3,
 499                 0xb2, 0x1f, 0x1f, 0x1b, 0x90, 0x4e, 0xd7, 0xe1
 500         };
 501         HMACMD5Context ctx;
 502
 503         hmac_md5_init_limK_to_64(KI, KI_len, &ctx);
 504         hmac_md5_update(SSKeyHash, sizeof(SSKeyHash), &ctx);
 505         hmac_md5_final(KO, &ctx);
 506
 507         ZERO_STRUCT(ctx);
 508 }