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(broadcast, "%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 1", REQ_KEY, myself->name, to->name);
  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(kx_version > 0) {
 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         char key[ECDH_SIZE * 2 + 1];
 149
 150         ecdh_generate_public(&to->ecdh, key);
 151
 152         bin2hex(key, key, ECDH_SIZE);
 153         key[ECDH_SIZE * 2] = '\0';
 154
 155         return send_request(to->nexthop->connection, "%d %s %s ECDH:%s %d %d %zu %d", ANS_KEY,
 156                                                 myself->name, to->name, key,
 157                                                 cipher_get_nid(&myself->incipher),
 158                                                 digest_get_nid(&myself->indigest),
 159                                                 digest_length(&myself->indigest),
 160                                                 myself->incompression);
 161 }
 162
 163 bool send_ans_key(node_t *to) {
 164         if(to->status.ecdh)
 165                 return send_ans_key_ecdh(to);
 166
 167         size_t keylen = cipher_keylength(&myself->incipher);
 168         char key[keylen * 2 + 1];
 169
 170         cipher_open_by_nid(&to->incipher, cipher_get_nid(&myself->incipher));
 171         digest_open_by_nid(&to->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 172         to->incompression = myself->incompression;
 173
 174         randomize(key, keylen);
 175         cipher_set_key(&to->incipher, key, true);
 176         digest_set_key(&to->indigest, key, keylen);
 177
 178         bin2hex(key, key, keylen);
 179         key[keylen * 2] = '\0';
 180
 181         // Reset sequence number and late packet window
 182         mykeyused = true;
 183         to->received_seqno = 0;
 184         if(replaywin) memset(to->late, 0, replaywin);
 185
 186         return send_request(to->nexthop->connection, "%d %s %s %s %d %d %zu %d", ANS_KEY,
 187                                                 myself->name, to->name, key,
 188                                                 cipher_get_nid(&to->incipher),
 189                                                 digest_get_nid(&to->indigest),
 190                                                 digest_length(&to->indigest),
 191                                                 to->incompression);
 192 }
 193
 194 bool ans_key_h(connection_t *c, char *request) {
 195         char from_name[MAX_STRING_SIZE];
 196         char to_name[MAX_STRING_SIZE];
 197         char key[MAX_STRING_SIZE];
 198         char address[MAX_STRING_SIZE] = "";
 199         char port[MAX_STRING_SIZE] = "";
 200         int cipher, digest, maclength, compression, keylen;
 201         node_t *from, *to;
 202
 203         if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING" %d",
 204                 from_name, to_name, key, &cipher, &digest, &maclength,
 205                 &compression, address, port) < 7) {
 206                 logger(LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
 207                            c->hostname);
 208                 return false;
 209         }
 210
 211         if(!check_id(from_name) || !check_id(to_name)) {
 212                 logger(LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_KEY", c->name, c->hostname, "invalid name");
 213                 return false;
 214         }
 215
 216         from = lookup_node(from_name);
 217
 218         if(!from) {
 219                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 220                            "ANS_KEY", c->name, c->hostname, from_name);
 221                 return true;
 222         }
 223
 224         to = lookup_node(to_name);
 225
 226         if(!to) {
 227                 logger(LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 228                            "ANS_KEY", c->name, c->hostname, to_name);
 229                 return true;
 230         }
 231
 232         /* Forward it if necessary */
 233
 234         if(to != myself) {
 235                 if(tunnelserver)
 236                         return true;
 237
 238                 if(!to->status.reachable) {
 239                         logger(LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 240                                    "ANS_KEY", c->name, c->hostname, to_name);
 241                         return true;
 242                 }
 243
 244                 if(!*address && from->address.sa.sa_family != AF_UNSPEC) {
 245                         char *address, *port;
 246                         ifdebug(PROTOCOL) logger(LOG_DEBUG, "Appending reflexive UDP address to ANS_KEY from %s to %s", from->name, to->name);
 247                         sockaddr2str(&from->address, &address, &port);
 248                         send_request(to->nexthop->connection, "%s %s %s", request, address, port);
 249                         free(address);
 250                         free(port);
 251                         return true;
 252                 }
 253
 254                 return send_request(to->nexthop->connection, "%s", request);
 255         }
 256
 257         /* Check and lookup cipher and digest algorithms */
 258
 259         if(!cipher_open_by_nid(&from->outcipher, cipher)) {
 260                 logger(LOG_ERR, "Node %s (%s) uses unknown cipher!", from->name, from->hostname);
 261                 return false;
 262         }
 263
 264         if(!digest_open_by_nid(&from->outdigest, digest, maclength)) {
 265                 logger(LOG_ERR, "Node %s (%s) uses unknown digest!", from->name, from->hostname);
 266                 return false;
 267         }
 268
 269         if(maclength != digest_length(&from->outdigest)) {
 270                 logger(LOG_ERR, "Node %s (%s) uses bogus MAC length!", from->name, from->hostname);
 271                 return false;
 272         }
 273
 274         if(compression < 0 || compression > 11) {
 275                 logger(LOG_ERR, "Node %s (%s) uses bogus compression level!", from->name, from->hostname);
 276                 return true;
 277         }
 278
 279         from->outcompression = compression;
 280
 281         /* ECDH or old-style key exchange? */
 282
 283         if(!strncmp(key, "ECDH:", 5)) {
 284                 keylen = (strlen(key) - 5) / 2;
 285
 286                 if(keylen != ECDH_SIZE) {
 287                         logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 288                         return false;
 289                 }
 290
 291                 if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
 292                         logger(LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
 293                         return false;
 294                 }
 295
 296                 if(!from->ecdh) {
 297                         from->status.ecdh = true;
 298                         if(!send_ans_key(from))
 299                                 return false;
 300                 }
 301
 302                 char shared[ECDH_SHARED_SIZE * 2 + 1];
 303                 char hex[ECDH_SHARED_SIZE * 2 + 1];
 304                 hex2bin(key + 5, key + 5, keylen);
 305
 306                 if(!ecdh_compute_shared(&from->ecdh, key + 5, shared))
 307                         return false;
 308
 309                 /* Update our crypto end */
 310
 311                 size_t mykeylen = cipher_keylength(&myself->incipher);
 312                 size_t hiskeylen = cipher_keylength(&from->outcipher);
 313
 314                 char *mykey;
 315                 char *hiskey;
 316                 char *seed;
 317
 318                 if(strcmp(myself->name, from->name) < 0) {
 319                         mykey = key;
 320                         hiskey = key + mykeylen * 2;
 321                         xasprintf(&seed, "tinc UDP key expansion %s %s", myself->name, from->name);
 322                 } else {
 323                         mykey = key + hiskeylen * 2;
 324                         hiskey = key;
 325                         xasprintf(&seed, "tinc UDP key expansion %s %s", from->name, myself->name);
 326                 }
 327
 328                 if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
 329                         return false;
 330
 331                 free(seed);
 332
 333                 cipher_open_by_nid(&from->incipher, cipher_get_nid(&myself->incipher));
 334                 digest_open_by_nid(&from->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 335                 from->incompression = myself->incompression;
 336
 337                 cipher_set_key(&from->incipher, mykey, true);
 338                 digest_set_key(&from->indigest, mykey + mykeylen, mykeylen);
 339
 340                 cipher_set_key(&from->outcipher, hiskey, false);
 341                 digest_set_key(&from->outdigest, hiskey + hiskeylen, hiskeylen);
 342
 343                 // Reset sequence number and late packet window
 344                 mykeyused = true;
 345                 from->received_seqno = 0;
 346                 if(replaywin)
 347                         memset(from->late, 0, replaywin);
 348
 349                 if(strcmp(myself->name, from->name) < 0)
 350                         memmove(key, key + mykeylen * 2, hiskeylen * 2);
 351         } else {
 352                 keylen = strlen(key) / 2;
 353                 hex2bin(key, key, keylen);
 354
 355                 if(keylen != cipher_keylength(&from->outcipher)) {
 356                         logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 357                         return false;
 358                 }
 359
 360                 /* Update our copy of the origin's packet key */
 361
 362                 cipher_set_key(&from->outcipher, key, false);
 363                 digest_set_key(&from->outdigest, key, keylen);
 364         }
 365
 366         from->status.validkey = true;
 367         from->sent_seqno = 0;
 368
 369         if(*address && *port) {
 370                 ifdebug(PROTOCOL) logger(LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
 371                 sockaddr_t sa = str2sockaddr(address, port);
 372                 update_node_udp(from, &sa);
 373         }
 374
 375         if(from->options & OPTION_PMTU_DISCOVERY)
 376                 send_mtu_probe(from);
 377
 378         return true;
 379 }