tinc-vpn.org Git - tinc/blob - src/protocol_key.c

   1 /*
   2     protocol_key.c -- handle the meta-protocol, key exchange
   3     Copyright (C) 1999-2005 Ivo Timmermans,
   4                   2000-2011 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "splay_tree.h"
  24 #include "cipher.h"
  25 #include "connection.h"
  26 #include "crypto.h"
  27 #include "ecdh.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "netutl.h"
  31 #include "node.h"
  32 #include "prf.h"
  33 #include "protocol.h"
  34 #include "utils.h"
  35 #include "xalloc.h"
  36
  37 static bool mykeyused = false;
  38
  39 void send_key_changed(void) {
  40         splay_node_t *node;
  41         connection_t *c;
  42
  43         send_request(everyone, "%d %x %s", KEY_CHANGED, rand(), myself->name);
  44
  45         /* Immediately send new keys to directly connected nodes to keep UDP mappings alive */
  46
  47         for(node = connection_tree->head; node; node = node->next) {
  48                 c = node->data;
  49                 if(c->status.active && c->node && c->node->status.reachable)
  50                         send_ans_key(c->node);
  51         }
  52 }
  53
  54 bool key_changed_h(connection_t *c, char *request) {
  55         char name[MAX_STRING_SIZE];
  56         node_t *n;
  57
  58         if(sscanf(request, "%*d %*x " MAX_STRING, name) != 1) {
  59                 logger(LOG_ERR, "Got bad %s from %s (%s)", "KEY_CHANGED",
  60                            c->name, c->hostname);
  61                 return false;
  62         }
  63
  64         if(seen_request(request))
  65                 return true;
  66
  67         n = lookup_node(name);
  68
  69         if(!n) {
  70                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist",
  71                            "KEY_CHANGED", c->name, c->hostname, name);
  72                 return true;
  73         }
  74
  75         n->status.validkey = false;
  76         n->last_req_key = 0;
  77
  78         /* Tell the others */
  79
  80         if(!tunnelserver)
  81                 forward_request(c, request);
  82
  83         return true;
  84 }
  85
  86 bool send_req_key(node_t *to) {
  87         return send_request(to->nexthop->connection, "%d %s %s %d", REQ_KEY, myself->name, to->name, experimental ? 1 : 0);
  88 }
  89
  90 bool req_key_h(connection_t *c, char *request) {
  91         char from_name[MAX_STRING_SIZE];
  92         char to_name[MAX_STRING_SIZE];
  93         node_t *from, *to;
  94         int kx_version = 0;
  95
  96         if(sscanf(request, "%*d " MAX_STRING " " MAX_STRING " %d", from_name, to_name, &kx_version) < 2) {
  97                 logger(LOG_ERR, "Got bad %s from %s (%s)", "REQ_KEY", c->name,
  98                            c->hostname);
  99                 return false;
 100         }
 101
 102         if(!check_id(from_name) || !check_id(to_name)) {
 103                 logger(LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_KEY", c->name, c->hostname, "invalid name");
 104                 return false;
 105         }
 106
 107         from = lookup_node(from_name);
 108
 109         if(!from) {
 110                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 111                            "REQ_KEY", c->name, c->hostname, from_name);
 112                 return true;
 113         }
 114
 115         to = lookup_node(to_name);
 116
 117         if(!to) {
 118                 logger(LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 119                            "REQ_KEY", c->name, c->hostname, to_name);
 120                 return true;
 121         }
 122
 123         /* Check if this key request is for us */
 124
 125         if(to == myself) {                      /* Yes, send our own key back */
 126                 if(experimental && kx_version >= 1) {
 127                         logger(LOG_DEBUG, "Got ECDH key request from %s", from->name);
 128                         from->status.ecdh = true;
 129                 }
 130                 send_ans_key(from);
 131         } else {
 132                 if(tunnelserver)
 133                         return true;
 134
 135                 if(!to->status.reachable) {
 136                         logger(LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 137                                 "REQ_KEY", c->name, c->hostname, to_name);
 138                         return true;
 139                 }
 140
 141                 send_request(to->nexthop->connection, "%s", request);
 142         }
 143
 144         return true;
 145 }
 146
 147 bool send_ans_key_ecdh(node_t *to) {
 148         int siglen = ecdsa_size(&myself->connection->ecdsa);
 149         char key[(ECDH_SIZE + siglen) * 2 + 1];
 150
 151         if(!ecdh_generate_public(&to->ecdh, key))
 152                 return false;
 153
 154         if(!ecdsa_sign(&myself->connection->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE))
 155                 return false;
 156
 157         b64encode(key, key, ECDH_SIZE + siglen);
 158
 159         char *pubkey = ecdsa_get_base64_public_key(&myself->connection->ecdsa);
 160
 161         if(!pubkey)
 162                 return false;
 163
 164         int result = send_request(to->nexthop->connection, "%d %s %s ECDH:%s:%s %d %d %zu %d", ANS_KEY,
 165                                                 myself->name, to->name, key, pubkey,
 166                                                 cipher_get_nid(&myself->incipher),
 167                                                 digest_get_nid(&myself->indigest),
 168                                                 digest_length(&myself->indigest),
 169                                                 myself->incompression);
 170
 171         free(pubkey);
 172         return result;
 173 }
 174
 175 bool send_ans_key(node_t *to) {
 176         if(experimental && to->status.ecdh)
 177                 return send_ans_key_ecdh(to);
 178
 179         size_t keylen = cipher_keylength(&myself->incipher);
 180         char key[keylen * 2 + 1];
 181
 182         cipher_open_by_nid(&to->incipher, cipher_get_nid(&myself->incipher));
 183         digest_open_by_nid(&to->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 184         to->incompression = myself->incompression;
 185
 186         randomize(key, keylen);
 187         cipher_set_key(&to->incipher, key, false);
 188         digest_set_key(&to->indigest, key, keylen);
 189
 190         bin2hex(key, key, keylen);
 191
 192         // Reset sequence number and late packet window
 193         mykeyused = true;
 194         to->received_seqno = 0;
 195         if(replaywin) memset(to->late, 0, replaywin);
 196
 197         return send_request(to->nexthop->connection, "%d %s %s %s %d %d %zu %d", ANS_KEY,
 198                                                 myself->name, to->name, key,
 199                                                 cipher_get_nid(&to->incipher),
 200                                                 digest_get_nid(&to->indigest),
 201                                                 digest_length(&to->indigest),
 202                                                 to->incompression);
 203 }
 204
 205 bool ans_key_h(connection_t *c, char *request) {
 206         char from_name[MAX_STRING_SIZE];
 207         char to_name[MAX_STRING_SIZE];
 208         char key[MAX_STRING_SIZE];
 209         char address[MAX_STRING_SIZE] = "";
 210         char port[MAX_STRING_SIZE] = "";
 211         int cipher, digest, maclength, compression, keylen;
 212         node_t *from, *to;
 213
 214         if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING,
 215                 from_name, to_name, key, &cipher, &digest, &maclength,
 216                 &compression, address, port) < 7) {
 217                 logger(LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
 218                            c->hostname);
 219                 return false;
 220         }
 221
 222         if(!check_id(from_name) || !check_id(to_name)) {
 223                 logger(LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_KEY", c->name, c->hostname, "invalid name");
 224                 return false;
 225         }
 226
 227         from = lookup_node(from_name);
 228
 229         if(!from) {
 230                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 231                            "ANS_KEY", c->name, c->hostname, from_name);
 232                 return true;
 233         }
 234
 235         to = lookup_node(to_name);
 236
 237         if(!to) {
 238                 logger(LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 239                            "ANS_KEY", c->name, c->hostname, to_name);
 240                 return true;
 241         }
 242
 243         /* Forward it if necessary */
 244
 245         if(to != myself) {
 246                 if(tunnelserver)
 247                         return true;
 248
 249                 if(!to->status.reachable) {
 250                         logger(LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 251                                    "ANS_KEY", c->name, c->hostname, to_name);
 252                         return true;
 253                 }
 254
 255                 if(!*address && from->address.sa.sa_family != AF_UNSPEC) {
 256                         char *address, *port;
 257                         ifdebug(PROTOCOL) logger(LOG_DEBUG, "Appending reflexive UDP address to ANS_KEY from %s to %s", from->name, to->name);
 258                         sockaddr2str(&from->address, &address, &port);
 259                         send_request(to->nexthop->connection, "%s %s %s", request, address, port);
 260                         free(address);
 261                         free(port);
 262                         return true;
 263                 }
 264
 265                 return send_request(to->nexthop->connection, "%s", request);
 266         }
 267
 268         /* Check and lookup cipher and digest algorithms */
 269
 270         if(!cipher_open_by_nid(&from->outcipher, cipher)) {
 271                 logger(LOG_ERR, "Node %s (%s) uses unknown cipher!", from->name, from->hostname);
 272                 return false;
 273         }
 274
 275         if(!digest_open_by_nid(&from->outdigest, digest, maclength)) {
 276                 logger(LOG_ERR, "Node %s (%s) uses unknown digest!", from->name, from->hostname);
 277                 return false;
 278         }
 279
 280         if(maclength != digest_length(&from->outdigest)) {
 281                 logger(LOG_ERR, "Node %s (%s) uses bogus MAC length!", from->name, from->hostname);
 282                 return false;
 283         }
 284
 285         if(compression < 0 || compression > 11) {
 286                 logger(LOG_ERR, "Node %s (%s) uses bogus compression level!", from->name, from->hostname);
 287                 return true;
 288         }
 289
 290         from->outcompression = compression;
 291
 292         /* ECDH or old-style key exchange? */
 293
 294         if(experimental && !strncmp(key, "ECDH:", 5)) {
 295                 char *pubkey = strchr(key + 5, ':');
 296                 if(pubkey)
 297                         *pubkey++ = 0;
 298
 299                 /* Check if we already have an ECDSA public key for this node.
 300                  * If not, use the one from the key exchange, and store it. */
 301
 302                 if(!node_read_ecdsa_public_key(from)) {
 303                         if(!pubkey) {
 304                                 logger(LOG_ERR, "No ECDSA public key known for %s (%s), cannot verify ECDH key exchange!", from->name, from->hostname);
 305                                 return true;
 306                         }
 307
 308                         if(!ecdsa_set_base64_public_key(&from->ecdsa, pubkey))
 309                                 return true;
 310
 311                         append_config_file(from->name, "ECDSAPublicKey", pubkey);
 312                 }
 313
 314                 int siglen = ecdsa_size(&from->ecdsa);
 315                 int keylen = b64decode(key + 5, key + 5, sizeof key - 5);
 316
 317                 if(keylen != ECDH_SIZE + siglen) {
 318                         logger(LOG_ERR, "Node %s (%s) uses wrong keylength! %d != %d", from->name, from->hostname, keylen, ECDH_SIZE + siglen);
 319                         return true;
 320                 }
 321
 322                 if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
 323                         logger(LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
 324                         return true;
 325                 }
 326
 327                 if(!ecdsa_verify(&from->ecdsa, key + 5, ECDH_SIZE, key + 5 + ECDH_SIZE)) {
 328                         logger(LOG_ERR, "Possible intruder %s (%s): %s", from->name, from->hostname, "invalid ECDSA signature");
 329                         return true;
 330                 }
 331
 332                 if(!from->ecdh) {
 333                         from->status.ecdh = true;
 334                         if(!send_ans_key(from))
 335                                 return true;
 336                 }
 337
 338                 char shared[ECDH_SHARED_SIZE * 2 + 1];
 339
 340                 if(!ecdh_compute_shared(&from->ecdh, key + 5, shared))
 341                         return true;
 342
 343                 /* Update our crypto end */
 344
 345                 size_t mykeylen = cipher_keylength(&myself->incipher);
 346                 size_t hiskeylen = cipher_keylength(&from->outcipher);
 347
 348                 char *mykey;
 349                 char *hiskey;
 350                 char *seed;
 351
 352                 if(strcmp(myself->name, from->name) < 0) {
 353                         mykey = key;
 354                         hiskey = key + mykeylen * 2;
 355                         xasprintf(&seed, "tinc UDP key expansion %s %s", myself->name, from->name);
 356                 } else {
 357                         mykey = key + hiskeylen * 2;
 358                         hiskey = key;
 359                         xasprintf(&seed, "tinc UDP key expansion %s %s", from->name, myself->name);
 360                 }
 361
 362                 if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
 363                         return true;
 364
 365                 free(seed);
 366
 367                 cipher_open_by_nid(&from->incipher, cipher_get_nid(&myself->incipher));
 368                 digest_open_by_nid(&from->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 369                 from->incompression = myself->incompression;
 370
 371                 cipher_set_key(&from->incipher, mykey, false);
 372                 digest_set_key(&from->indigest, mykey + mykeylen, mykeylen);
 373
 374                 cipher_set_key(&from->outcipher, hiskey, true);
 375                 digest_set_key(&from->outdigest, hiskey + hiskeylen, hiskeylen);
 376
 377                 // Reset sequence number and late packet window
 378                 mykeyused = true;
 379                 from->received_seqno = 0;
 380                 if(replaywin)
 381                         memset(from->late, 0, replaywin);
 382
 383                 if(strcmp(myself->name, from->name) < 0)
 384                         memmove(key, key + mykeylen * 2, hiskeylen * 2);
 385         } else {
 386                 keylen = hex2bin(key, key, sizeof key);
 387
 388                 if(keylen != cipher_keylength(&from->outcipher)) {
 389                         logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 390                         return true;
 391                 }
 392
 393                 /* Update our copy of the origin's packet key */
 394
 395                 cipher_set_key(&from->outcipher, key, true);
 396                 digest_set_key(&from->outdigest, key, keylen);
 397         }
 398
 399         from->status.validkey = true;
 400         from->sent_seqno = 0;
 401
 402         if(*address && *port) {
 403                 ifdebug(PROTOCOL) logger(LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
 404                 sockaddr_t sa = str2sockaddr(address, port);
 405                 update_node_udp(from, &sa);
 406         }
 407
 408         if(from->options & OPTION_PMTU_DISCOVERY)
 409                 send_mtu_probe(from);
 410
 411         return true;
 412 }