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                   2000-2012 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, const 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(DEBUG_ALWAYS, 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(DEBUG_ALWAYS, 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         if(experimental && OPTION_VERSION(to->options) >= 2) {
  88                 if(!node_read_ecdsa_public_key(to))
  89                         send_request(to->nexthop->connection, "%d %s %s %d", REQ_KEY, myself->name, to->name, REQ_PUBKEY);
  90         }
  91         return send_request(to->nexthop->connection, "%d %s %s", REQ_KEY, myself->name, to->name);
  92 }
  93
  94 /* REQ_KEY is overloaded to allow arbitrary requests to be routed between two nodes. */
  95
  96 static bool req_key_ext_h(connection_t *c, const char *request, node_t *from, int reqno) {
  97         switch(reqno) {
  98                 case REQ_PUBKEY: {
  99                         char *pubkey = ecdsa_get_base64_public_key(&myself->connection->ecdsa);
 100                         send_request(from->nexthop->connection, "%d %s %s %d %s", REQ_KEY, myself->name, from->name, ANS_PUBKEY, pubkey);
 101                         free(pubkey);
 102                         return true;
 103                 }
 104
 105                 case ANS_PUBKEY: {
 106                         if(node_read_ecdsa_public_key(from)) {
 107                                 logger(DEBUG_ALWAYS, LOG_WARNING, "Got ANS_PUBKEY from %s (%s) even though we already have his pubkey", from->name, from->hostname);
 108                                 return true;
 109                         }
 110
 111                         char pubkey[4096];
 112                         if(sscanf(request, "%*d %*s %*s %*d " MAX_STRING, pubkey) != 1 || !ecdsa_set_base64_public_key(&from->ecdsa, pubkey)) {
 113                                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_PUBKEY", from->name, from->hostname, "invalid pubkey");
 114                                 return true;
 115                         }
 116
 117                         logger(DEBUG_ALWAYS, LOG_INFO, "Learned ECDSA public key from %s (%s)", from->name, from->hostname);
 118                         append_config_file(from->name, "ECDSAPublicKey", pubkey);
 119                         return true;
 120                 }
 121
 122                 default:
 123                         logger(DEBUG_ALWAYS, LOG_ERR, "Unknown extended REQ_KEY request from %s (%s): %s", from->name, from->hostname, request);
 124                         return true;
 125         }
 126 }
 127
 128 bool req_key_h(connection_t *c, const char *request) {
 129         char from_name[MAX_STRING_SIZE];
 130         char to_name[MAX_STRING_SIZE];
 131         node_t *from, *to;
 132         int reqno = 0;
 133
 134         if(sscanf(request, "%*d " MAX_STRING " " MAX_STRING " %d", from_name, to_name, &reqno) < 2) {
 135                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "REQ_KEY", c->name,
 136                            c->hostname);
 137                 return false;
 138         }
 139
 140         if(!check_id(from_name) || !check_id(to_name)) {
 141                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_KEY", c->name, c->hostname, "invalid name");
 142                 return false;
 143         }
 144
 145         from = lookup_node(from_name);
 146
 147         if(!from) {
 148                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 149                            "REQ_KEY", c->name, c->hostname, from_name);
 150                 return true;
 151         }
 152
 153         to = lookup_node(to_name);
 154
 155         if(!to) {
 156                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 157                            "REQ_KEY", c->name, c->hostname, to_name);
 158                 return true;
 159         }
 160
 161         /* Check if this key request is for us */
 162
 163         if(to == myself) {                      /* Yes, send our own key back */
 164                 if(experimental && reqno)
 165                         return req_key_ext_h(c, request, from, reqno);
 166
 167                 send_ans_key(from);
 168         } else {
 169                 if(tunnelserver)
 170                         return true;
 171
 172                 if(!to->status.reachable) {
 173                         logger(DEBUG_ALWAYS, LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 174                                 "REQ_KEY", c->name, c->hostname, to_name);
 175                         return true;
 176                 }
 177
 178                 send_request(to->nexthop->connection, "%s", request);
 179         }
 180
 181         return true;
 182 }
 183
 184 bool send_ans_key_ecdh(node_t *to) {
 185         int siglen = ecdsa_size(&myself->connection->ecdsa);
 186         char key[(ECDH_SIZE + siglen) * 2 + 1];
 187
 188         if(!ecdh_generate_public(&to->ecdh, key))
 189                 return false;
 190
 191         if(!ecdsa_sign(&myself->connection->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE))
 192                 return false;
 193
 194         b64encode(key, key, ECDH_SIZE + siglen);
 195
 196         int result = send_request(to->nexthop->connection, "%d %s %s %s %d %d %zu %d", ANS_KEY,
 197                                                 myself->name, to->name, key,
 198                                                 cipher_get_nid(&myself->incipher),
 199                                                 digest_get_nid(&myself->indigest),
 200                                                 digest_length(&myself->indigest),
 201                                                 myself->incompression);
 202
 203         return result;
 204 }
 205
 206 bool send_ans_key(node_t *to) {
 207         if(experimental && OPTION_VERSION(to->options) >= 2)
 208                 return send_ans_key_ecdh(to);
 209
 210         size_t keylen = cipher_keylength(&myself->incipher);
 211         char key[keylen * 2 + 1];
 212
 213         cipher_open_by_nid(&to->incipher, cipher_get_nid(&myself->incipher));
 214         digest_open_by_nid(&to->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 215         to->incompression = myself->incompression;
 216
 217         randomize(key, keylen);
 218         cipher_set_key(&to->incipher, key, false);
 219         digest_set_key(&to->indigest, key, keylen);
 220
 221         bin2hex(key, key, keylen);
 222
 223         // Reset sequence number and late packet window
 224         mykeyused = true;
 225         to->received_seqno = 0;
 226         if(replaywin) memset(to->late, 0, replaywin);
 227
 228         return send_request(to->nexthop->connection, "%d %s %s %s %d %d %zu %d", ANS_KEY,
 229                                                 myself->name, to->name, key,
 230                                                 cipher_get_nid(&to->incipher),
 231                                                 digest_get_nid(&to->indigest),
 232                                                 digest_length(&to->indigest),
 233                                                 to->incompression);
 234 }
 235
 236 bool ans_key_h(connection_t *c, const char *request) {
 237         char from_name[MAX_STRING_SIZE];
 238         char to_name[MAX_STRING_SIZE];
 239         char key[MAX_STRING_SIZE];
 240         char address[MAX_STRING_SIZE] = "";
 241         char port[MAX_STRING_SIZE] = "";
 242         int cipher, digest, maclength, compression, keylen;
 243         node_t *from, *to;
 244
 245         if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING,
 246                 from_name, to_name, key, &cipher, &digest, &maclength,
 247                 &compression, address, port) < 7) {
 248                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
 249                            c->hostname);
 250                 return false;
 251         }
 252
 253         if(!check_id(from_name) || !check_id(to_name)) {
 254                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_KEY", c->name, c->hostname, "invalid name");
 255                 return false;
 256         }
 257
 258         from = lookup_node(from_name);
 259
 260         if(!from) {
 261                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 262                            "ANS_KEY", c->name, c->hostname, from_name);
 263                 return true;
 264         }
 265
 266         to = lookup_node(to_name);
 267
 268         if(!to) {
 269                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 270                            "ANS_KEY", c->name, c->hostname, to_name);
 271                 return true;
 272         }
 273
 274         /* Forward it if necessary */
 275
 276         if(to != myself) {
 277                 if(tunnelserver)
 278                         return true;
 279
 280                 if(!to->status.reachable) {
 281                         logger(DEBUG_ALWAYS, LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 282                                    "ANS_KEY", c->name, c->hostname, to_name);
 283                         return true;
 284                 }
 285
 286                 if(!*address && from->address.sa.sa_family != AF_UNSPEC) {
 287                         char *address, *port;
 288                         logger(DEBUG_PROTOCOL, LOG_DEBUG, "Appending reflexive UDP address to ANS_KEY from %s to %s", from->name, to->name);
 289                         sockaddr2str(&from->address, &address, &port);
 290                         send_request(to->nexthop->connection, "%s %s %s", request, address, port);
 291                         free(address);
 292                         free(port);
 293                         return true;
 294                 }
 295
 296                 return send_request(to->nexthop->connection, "%s", request);
 297         }
 298
 299         /* Check and lookup cipher and digest algorithms */
 300
 301         if(!cipher_open_by_nid(&from->outcipher, cipher)) {
 302                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses unknown cipher!", from->name, from->hostname);
 303                 return false;
 304         }
 305
 306         if(!digest_open_by_nid(&from->outdigest, digest, maclength)) {
 307                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses unknown digest!", from->name, from->hostname);
 308                 return false;
 309         }
 310
 311         if(maclength != digest_length(&from->outdigest)) {
 312                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses bogus MAC length!", from->name, from->hostname);
 313                 return false;
 314         }
 315
 316         if(compression < 0 || compression > 11) {
 317                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses bogus compression level!", from->name, from->hostname);
 318                 return true;
 319         }
 320
 321         from->outcompression = compression;
 322
 323         /* ECDH or old-style key exchange? */
 324
 325         if(experimental && OPTION_VERSION(from->options) >= 2) {
 326                 /* Check if we already have an ECDSA public key for this node. */
 327
 328                 if(!node_read_ecdsa_public_key(from)) {
 329                         logger(DEBUG_ALWAYS, LOG_ERR, "No ECDSA public key known for %s (%s), cannot verify ECDH key exchange!", from->name, from->hostname);
 330                         return true;
 331                 }
 332
 333                 int siglen = ecdsa_size(&from->ecdsa);
 334                 int keylen = b64decode(key, key, sizeof key);
 335
 336                 if(keylen != ECDH_SIZE + siglen) {
 337                         logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses wrong keylength! %d != %d", from->name, from->hostname, keylen, ECDH_SIZE + siglen);
 338                         return true;
 339                 }
 340
 341                 if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
 342                         logger(DEBUG_ALWAYS, LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
 343                         return true;
 344                 }
 345
 346                 if(!ecdsa_verify(&from->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE)) {
 347                         logger(DEBUG_ALWAYS, LOG_ERR, "Possible intruder %s (%s): %s", from->name, from->hostname, "invalid ECDSA signature");
 348                         return true;
 349                 }
 350
 351                 if(!from->ecdh) {
 352                         if(!send_ans_key_ecdh(from))
 353                                 return true;
 354                 }
 355
 356                 char shared[ECDH_SHARED_SIZE * 2 + 1];
 357
 358                 if(!ecdh_compute_shared(&from->ecdh, key, shared))
 359                         return true;
 360
 361                 /* Update our crypto end */
 362
 363                 size_t mykeylen = cipher_keylength(&myself->incipher);
 364                 size_t hiskeylen = cipher_keylength(&from->outcipher);
 365
 366                 char *mykey;
 367                 char *hiskey;
 368                 char *seed;
 369
 370                 if(strcmp(myself->name, from->name) < 0) {
 371                         mykey = key;
 372                         hiskey = key + mykeylen * 2;
 373                         xasprintf(&seed, "tinc UDP key expansion %s %s", myself->name, from->name);
 374                 } else {
 375                         mykey = key + hiskeylen * 2;
 376                         hiskey = key;
 377                         xasprintf(&seed, "tinc UDP key expansion %s %s", from->name, myself->name);
 378                 }
 379
 380                 if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
 381                         return true;
 382
 383                 free(seed);
 384
 385                 cipher_open_by_nid(&from->incipher, cipher_get_nid(&myself->incipher));
 386                 digest_open_by_nid(&from->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 387                 from->incompression = myself->incompression;
 388
 389                 cipher_set_key(&from->incipher, mykey, false);
 390                 digest_set_key(&from->indigest, mykey + mykeylen, mykeylen);
 391
 392                 cipher_set_key(&from->outcipher, hiskey, true);
 393                 digest_set_key(&from->outdigest, hiskey + hiskeylen, hiskeylen);
 394
 395                 // Reset sequence number and late packet window
 396                 mykeyused = true;
 397                 from->received_seqno = 0;
 398                 if(replaywin)
 399                         memset(from->late, 0, replaywin);
 400
 401                 if(strcmp(myself->name, from->name) < 0)
 402                         memmove(key, key + mykeylen * 2, hiskeylen * 2);
 403         } else {
 404                 keylen = hex2bin(key, key, sizeof key);
 405
 406                 if(keylen != cipher_keylength(&from->outcipher)) {
 407                         logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 408                         return true;
 409                 }
 410
 411                 /* Update our copy of the origin's packet key */
 412
 413                 cipher_set_key(&from->outcipher, key, true);
 414                 digest_set_key(&from->outdigest, key, keylen);
 415         }
 416
 417         from->status.validkey = true;
 418         from->sent_seqno = 0;
 419
 420         if(*address && *port) {
 421                 logger(DEBUG_PROTOCOL, LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
 422                 sockaddr_t sa = str2sockaddr(address, port);
 423                 update_node_udp(from, &sa);
 424         }
 425
 426         if(from->options & OPTION_PMTU_DISCOVERY)
 427                 send_mtu_probe(from);
 428
 429         return true;
 430 }