git.meshlink.io Git - meshlink/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 "protocol.h"
  33 #include "utils.h"
  34 #include "xalloc.h"
  35
  36 static bool mykeyused = false;
  37
  38 void send_key_changed(void) {
  39         splay_node_t *node;
  40         connection_t *c;
  41
  42         send_request(broadcast, "%d %x %s", KEY_CHANGED, rand(), myself->name);
  43
  44         /* Immediately send new keys to directly connected nodes to keep UDP mappings alive */
  45
  46         for(node = connection_tree->head; node; node = node->next) {
  47                 c = node->data;
  48                 if(c->status.active && c->node && c->node->status.reachable)
  49                         send_ans_key(c->node);
  50         }
  51 }
  52
  53 bool key_changed_h(connection_t *c, char *request) {
  54         char name[MAX_STRING_SIZE];
  55         node_t *n;
  56
  57         if(sscanf(request, "%*d %*x " MAX_STRING, name) != 1) {
  58                 logger(LOG_ERR, "Got bad %s from %s (%s)", "KEY_CHANGED",
  59                            c->name, c->hostname);
  60                 return false;
  61         }
  62
  63         if(seen_request(request))
  64                 return true;
  65
  66         n = lookup_node(name);
  67
  68         if(!n) {
  69                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist",
  70                            "KEY_CHANGED", c->name, c->hostname, name);
  71                 return true;
  72         }
  73
  74         n->status.validkey = false;
  75         n->last_req_key = 0;
  76
  77         /* Tell the others */
  78
  79         if(!tunnelserver)
  80                 forward_request(c, request);
  81
  82         return true;
  83 }
  84
  85 bool send_req_key(node_t *to) {
  86         return send_request(to->nexthop->connection, "%d %s %s 1", REQ_KEY, myself->name, to->name);
  87 }
  88
  89 bool req_key_h(connection_t *c, char *request) {
  90         char from_name[MAX_STRING_SIZE];
  91         char to_name[MAX_STRING_SIZE];
  92         node_t *from, *to;
  93         int kx_version = 0;
  94
  95         if(sscanf(request, "%*d " MAX_STRING " " MAX_STRING " %d", from_name, to_name, &kx_version) < 2) {
  96                 logger(LOG_ERR, "Got bad %s from %s (%s)", "REQ_KEY", c->name,
  97                            c->hostname);
  98                 return false;
  99         }
 100
 101         if(!check_id(from_name) || !check_id(to_name)) {
 102                 logger(LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_KEY", c->name, c->hostname, "invalid name");
 103                 return false;
 104         }
 105
 106         from = lookup_node(from_name);
 107
 108         if(!from) {
 109                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 110                            "REQ_KEY", c->name, c->hostname, from_name);
 111                 return true;
 112         }
 113
 114         to = lookup_node(to_name);
 115
 116         if(!to) {
 117                 logger(LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 118                            "REQ_KEY", c->name, c->hostname, to_name);
 119                 return true;
 120         }
 121
 122         /* Check if this key request is for us */
 123
 124         if(to == myself) {                      /* Yes, send our own key back */
 125                 if(kx_version > 0) {
 126                         logger(LOG_DEBUG, "Got ECDH key request from %s", from->name);
 127                         from->status.ecdh = true;
 128                 }
 129                 send_ans_key(from);
 130         } else {
 131                 if(tunnelserver)
 132                         return true;
 133
 134                 if(!to->status.reachable) {
 135                         logger(LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 136                                 "REQ_KEY", c->name, c->hostname, to_name);
 137                         return true;
 138                 }
 139
 140                 send_request(to->nexthop->connection, "%s", request);
 141         }
 142
 143         return true;
 144 }
 145
 146 bool send_ans_key_ecdh(node_t *to) {
 147         char key[ECDH_SIZE * 2 + 1];
 148
 149         ecdh_generate_public(&to->ecdh, key);
 150
 151         bin2hex(key, key, ECDH_SIZE);
 152         key[ECDH_SIZE * 2] = '\0';
 153
 154         return send_request(to->nexthop->connection, "%d %s %s ECDH:%s %d %d %zu %d", ANS_KEY,
 155                                                 myself->name, to->name, key,
 156                                                 cipher_get_nid(&myself->incipher),
 157                                                 digest_get_nid(&myself->indigest),
 158                                                 digest_length(&myself->indigest),
 159                                                 myself->incompression);
 160 }
 161
 162 bool send_ans_key(node_t *to) {
 163         if(to->status.ecdh)
 164                 return send_ans_key_ecdh(to);
 165
 166         size_t keylen = cipher_keylength(&myself->incipher);
 167         char key[keylen * 2 + 1];
 168
 169         cipher_open_by_nid(&to->incipher, cipher_get_nid(&myself->incipher));
 170         digest_open_by_nid(&to->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 171         to->incompression = myself->incompression;
 172
 173         randomize(key, keylen);
 174         cipher_set_key(&to->incipher, key, true);
 175         digest_set_key(&to->indigest, key, keylen);
 176
 177         bin2hex(key, key, keylen);
 178         key[keylen * 2] = '\0';
 179
 180         // Reset sequence number and late packet window
 181         mykeyused = true;
 182         to->received_seqno = 0;
 183         if(replaywin) memset(to->late, 0, replaywin);
 184
 185         return send_request(to->nexthop->connection, "%d %s %s %s %d %d %zu %d", ANS_KEY,
 186                                                 myself->name, to->name, key,
 187                                                 cipher_get_nid(&to->incipher),
 188                                                 digest_get_nid(&to->indigest),
 189                                                 digest_length(&to->indigest),
 190                                                 to->incompression);
 191 }
 192
 193 bool ans_key_h(connection_t *c, char *request) {
 194         char from_name[MAX_STRING_SIZE];
 195         char to_name[MAX_STRING_SIZE];
 196         char key[MAX_STRING_SIZE];
 197         char address[MAX_STRING_SIZE] = "";
 198         char port[MAX_STRING_SIZE] = "";
 199         int cipher, digest, maclength, compression, keylen;
 200         node_t *from, *to;
 201
 202         if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING" %d",
 203                 from_name, to_name, key, &cipher, &digest, &maclength,
 204                 &compression, address, port) < 7) {
 205                 logger(LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
 206                            c->hostname);
 207                 return false;
 208         }
 209
 210         if(!check_id(from_name) || !check_id(to_name)) {
 211                 logger(LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_KEY", c->name, c->hostname, "invalid name");
 212                 return false;
 213         }
 214
 215         from = lookup_node(from_name);
 216
 217         if(!from) {
 218                 logger(LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
 219                            "ANS_KEY", c->name, c->hostname, from_name);
 220                 return true;
 221         }
 222
 223         to = lookup_node(to_name);
 224
 225         if(!to) {
 226                 logger(LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
 227                            "ANS_KEY", c->name, c->hostname, to_name);
 228                 return true;
 229         }
 230
 231         /* Forward it if necessary */
 232
 233         if(to != myself) {
 234                 if(tunnelserver)
 235                         return true;
 236
 237                 if(!to->status.reachable) {
 238                         logger(LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
 239                                    "ANS_KEY", c->name, c->hostname, to_name);
 240                         return true;
 241                 }
 242
 243                 if(!*address && from->address.sa.sa_family != AF_UNSPEC) {
 244                         char *address, *port;
 245                         ifdebug(PROTOCOL) logger(LOG_DEBUG, "Appending reflexive UDP address to ANS_KEY from %s to %s", from->name, to->name);
 246                         sockaddr2str(&from->address, &address, &port);
 247                         send_request(to->nexthop->connection, "%s %s %s", request, address, port);
 248                         free(address);
 249                         free(port);
 250                         return true;
 251                 }
 252
 253                 return send_request(to->nexthop->connection, "%s", request);
 254         }
 255
 256         /* Check and lookup cipher and digest algorithms */
 257
 258         if(!cipher_open_by_nid(&from->outcipher, cipher)) {
 259                 logger(LOG_ERR, "Node %s (%s) uses unknown cipher!", from->name, from->hostname);
 260                 return false;
 261         }
 262
 263         if(!digest_open_by_nid(&from->outdigest, digest, maclength)) {
 264                 logger(LOG_ERR, "Node %s (%s) uses unknown digest!", from->name, from->hostname);
 265                 return false;
 266         }
 267
 268         if(maclength != digest_length(&from->outdigest)) {
 269                 logger(LOG_ERR, "Node %s (%s) uses bogus MAC length!", from->name, from->hostname);
 270                 return false;
 271         }
 272
 273         if(compression < 0 || compression > 11) {
 274                 logger(LOG_ERR, "Node %s (%s) uses bogus compression level!", from->name, from->hostname);
 275                 return true;
 276         }
 277
 278         from->outcompression = compression;
 279
 280         /* ECDH or old-style key exchange? */
 281         /* TODO: look at SSH and TLS to see how they derive cipher and HMAC keys from shared secret properly */
 282
 283         if(!strncmp(key, "ECDH:", 5)) {
 284                 logger(LOG_DEBUG, "Got ECDH key from %s", from->name);
 285
 286                 keylen = (strlen(key) - 5) / 2;
 287
 288                 if(keylen != ECDH_SIZE) {
 289                         logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 290                         return false;
 291                 }
 292
 293                 if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
 294                         logger(LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
 295                         return false;
 296                 }
 297
 298                 if(!from->ecdh) {
 299                         logger(LOG_DEBUG, "Woops, we didn't generate our public key yet");
 300                         from->status.ecdh = true;
 301                         if(!send_ans_key(from))
 302                                 return false;
 303                 }
 304
 305                 char shared[ECDH_SHARED_SIZE * 2 + 1];
 306                 char hex[ECDH_SHARED_SIZE * 2 + 1];
 307                 hex2bin(key + 5, key + 5, keylen);
 308
 309                 if(!ecdh_compute_shared(&from->ecdh, key + 5, shared))
 310                         return false;
 311
 312                 /* Update our crypto end */
 313
 314                 char *mykey;
 315                 size_t mykeylen = cipher_keylength(&myself->incipher);
 316                 keylen = cipher_keylength(&from->outcipher);
 317
 318                 if(ECDH_SHARED_SIZE < mykeylen) {
 319                         logger(LOG_ERR, "ECDH key too short for cipher of MYSELF!");
 320                         return false;
 321                 }
 322
 323                 if(strcmp(myself->name, from->name) < 0) {
 324                         logger(LOG_DEBUG, "Using left half of shared secret");
 325                         mykey = shared;
 326                         memcpy(key, shared + ECDH_SHARED_SIZE - keylen, keylen);
 327                 } else {
 328                         logger(LOG_DEBUG, "Using right half of shared secret");
 329                         mykey = shared + ECDH_SHARED_SIZE - mykeylen;
 330                         memcpy(key, shared, keylen);
 331                 }
 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);
 339
 340                 // Reset sequence number and late packet window
 341                 mykeyused = true;
 342                 from->received_seqno = 0;
 343                 if(replaywin)
 344                         memset(from->late, 0, replaywin);
 345
 346                 bin2hex(shared, hex, ECDH_SHARED_SIZE);
 347                 hex[ECDH_SHARED_SIZE * 2] = 0;
 348                 logger(LOG_DEBUG, "Shared secret was %s", hex);
 349
 350                 bin2hex(mykey, hex, mykeylen);
 351                 hex[mykeylen * 2] = 0;
 352                 logger(LOG_DEBUG, "My part is: %s (%d)", hex, mykeylen);
 353
 354                 bin2hex(key, hex, keylen);
 355                 hex[keylen * 2] = 0;
 356                 logger(LOG_DEBUG, "His part is: %s (%d)", hex, keylen);
 357         } else {
 358                 keylen = strlen(key) / 2;
 359                 hex2bin(key, key, keylen);
 360         }
 361
 362         /* Update our copy of the origin's packet key */
 363
 364         if(keylen != cipher_keylength(&from->outcipher)) {
 365                 logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 366                 return false;
 367         }
 368
 369         cipher_set_key(&from->outcipher, key, false);
 370         digest_set_key(&from->outdigest, key, keylen);
 371
 372         from->status.validkey = true;
 373         from->sent_seqno = 0;
 374
 375         if(*address && *port) {
 376                 ifdebug(PROTOCOL) logger(LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
 377                 sockaddr_t sa = str2sockaddr(address, port);
 378                 update_node_udp(from, &sa);
 379         }
 380
 381         if(from->options & OPTION_PMTU_DISCOVERY)
 382                 send_mtu_probe(from);
 383
 384         return true;
 385 }