Introduce lightweight PMTU probe replies.
[tinc] / src / protocol_key.c
1 /*
2     protocol_key.c -- handle the meta-protocol, key exchange
3     Copyright (C) 1999-2005 Ivo Timmermans,
4                   2000-2013 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 "cipher.h"
24 #include "connection.h"
25 #include "crypto.h"
26 #include "logger.h"
27 #include "net.h"
28 #include "netutl.h"
29 #include "node.h"
30 #include "prf.h"
31 #include "protocol.h"
32 #include "sptps.h"
33 #include "utils.h"
34 #include "xalloc.h"
35
36 static bool mykeyused = false;
37
38 void send_key_changed(void) {
39         send_request(everyone, "%d %x %s", KEY_CHANGED, rand(), myself->name);
40
41         /* Immediately send new keys to directly connected nodes to keep UDP mappings alive */
42
43         for list_each(connection_t, c, connection_list)
44                 if(c->status.active && c->node && c->node->status.reachable && !c->node->status.sptps)
45                         send_ans_key(c->node);
46
47         /* Force key exchange for connections using SPTPS */
48
49         if(experimental) {
50                 for splay_each(node_t, n, node_tree)
51                         if(n->status.reachable && n->status.validkey && n->status.sptps)
52                                 sptps_force_kex(&n->sptps);
53         }
54 }
55
56 bool key_changed_h(connection_t *c, const char *request) {
57         char name[MAX_STRING_SIZE];
58         node_t *n;
59
60         if(sscanf(request, "%*d %*x " MAX_STRING, name) != 1) {
61                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "KEY_CHANGED",
62                            c->name, c->hostname);
63                 return false;
64         }
65
66         if(seen_request(request))
67                 return true;
68
69         n = lookup_node(name);
70
71         if(!n) {
72                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) origin %s which does not exist",
73                            "KEY_CHANGED", c->name, c->hostname, name);
74                 return true;
75         }
76
77         if(!n->status.sptps) {
78                 n->status.validkey = false;
79                 n->last_req_key = 0;
80         }
81
82         /* Tell the others */
83
84         if(!tunnelserver)
85                 forward_request(c, request);
86
87         return true;
88 }
89
90 static bool send_initial_sptps_data(void *handle, uint8_t type, const char *data, size_t len) {
91         node_t *to = handle;
92         to->sptps.send_data = send_sptps_data;
93         char buf[len * 4 / 3 + 5];
94         b64encode(data, buf, len);
95         return send_request(to->nexthop->connection, "%d %s %s %d %s", REQ_KEY, myself->name, to->name, REQ_KEY, buf);
96 }
97
98 bool send_req_key(node_t *to) {
99         if(to->status.sptps) {
100                 if(!node_read_ecdsa_public_key(to)) {
101                         logger(DEBUG_PROTOCOL, LOG_DEBUG, "No ECDSA key known for %s (%s)", to->name, to->hostname);
102                         send_request(to->nexthop->connection, "%d %s %s %d", REQ_KEY, myself->name, to->name, REQ_PUBKEY);
103                         return true;
104                 }
105
106                 if(to->sptps.label)
107                         logger(DEBUG_ALWAYS, LOG_DEBUG, "send_req_key(%s) called while sptps->label != NULL!", to->name);
108
109                 char label[25 + strlen(myself->name) + strlen(to->name)];
110                 snprintf(label, sizeof label, "tinc UDP key expansion %s %s", myself->name, to->name);
111                 sptps_stop(&to->sptps);
112                 to->status.validkey = false;
113                 to->status.waitingforkey = true;
114                 to->last_req_key = now.tv_sec;
115                 to->incompression = myself->incompression;
116                 return sptps_start(&to->sptps, to, true, true, myself->connection->ecdsa, to->ecdsa, label, sizeof label, send_initial_sptps_data, receive_sptps_record);
117         }
118
119         return send_request(to->nexthop->connection, "%d %s %s", REQ_KEY, myself->name, to->name);
120 }
121
122 /* REQ_KEY is overloaded to allow arbitrary requests to be routed between two nodes. */
123
124 static bool req_key_ext_h(connection_t *c, const char *request, node_t *from, int reqno) {
125         switch(reqno) {
126                 case REQ_PUBKEY: {
127                         char *pubkey = ecdsa_get_base64_public_key(myself->connection->ecdsa);
128                         send_request(from->nexthop->connection, "%d %s %s %d %s", REQ_KEY, myself->name, from->name, ANS_PUBKEY, pubkey);
129                         free(pubkey);
130                         return true;
131                 }
132
133                 case ANS_PUBKEY: {
134                         if(node_read_ecdsa_public_key(from)) {
135                                 logger(DEBUG_PROTOCOL, LOG_WARNING, "Got ANS_PUBKEY from %s (%s) even though we already have his pubkey", from->name, from->hostname);
136                                 return true;
137                         }
138
139                         char pubkey[MAX_STRING_SIZE];
140                         if(sscanf(request, "%*d %*s %*s %*d " MAX_STRING, pubkey) != 1 || !(from->ecdsa = ecdsa_set_base64_public_key(pubkey))) {
141                                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_PUBKEY", from->name, from->hostname, "invalid pubkey");
142                                 return true;
143                         }
144
145                         logger(DEBUG_PROTOCOL, LOG_INFO, "Learned ECDSA public key from %s (%s)", from->name, from->hostname);
146                         append_config_file(from->name, "ECDSAPublicKey", pubkey);
147                         return true;
148                 }
149
150                 case REQ_KEY: {
151                         if(!node_read_ecdsa_public_key(from)) {
152                                 logger(DEBUG_PROTOCOL, LOG_DEBUG, "No ECDSA key known for %s (%s)", from->name, from->hostname);
153                                 send_request(from->nexthop->connection, "%d %s %s %d", REQ_KEY, myself->name, from->name, REQ_PUBKEY);
154                                 return true;
155                         }
156
157                         if(from->sptps.label)
158                                 logger(DEBUG_ALWAYS, LOG_DEBUG, "Got REQ_KEY from %s while we already started a SPTPS session!", from->name);
159
160                         char buf[MAX_STRING_SIZE];
161                         int len;
162
163                         if(sscanf(request, "%*d %*s %*s %*d " MAX_STRING, buf) != 1 || !(len = b64decode(buf, buf, strlen(buf)))) {
164                                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_SPTPS_START", from->name, from->hostname, "invalid SPTPS data");
165                                 return true;
166                         }
167
168                         char label[25 + strlen(from->name) + strlen(myself->name)];
169                         snprintf(label, sizeof label, "tinc UDP key expansion %s %s", from->name, myself->name);
170                         sptps_stop(&from->sptps);
171                         from->status.validkey = false;
172                         from->status.waitingforkey = true;
173                         from->last_req_key = now.tv_sec;
174                         sptps_start(&from->sptps, from, false, true, myself->connection->ecdsa, from->ecdsa, label, sizeof label, send_sptps_data, receive_sptps_record);
175                         sptps_receive_data(&from->sptps, buf, len);
176                         return true;
177                 }
178
179                 case REQ_SPTPS: {
180                         if(!from->status.validkey) {
181                                 logger(DEBUG_PROTOCOL, LOG_ERR, "Got REQ_SPTPS from %s (%s) but we don't have a valid key yet", from->name, from->hostname);
182                                 return true;
183                         }
184
185                         char buf[MAX_STRING_SIZE];
186                         int len;
187                         if(sscanf(request, "%*d %*s %*s %*d " MAX_STRING, buf) != 1 || !(len = b64decode(buf, buf, strlen(buf)))) {
188                                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_SPTPS", from->name, from->hostname, "invalid SPTPS data");
189                                 return true;
190                         }
191                         sptps_receive_data(&from->sptps, buf, len);
192                         return true;
193                 }
194
195                 default:
196                         logger(DEBUG_ALWAYS, LOG_ERR, "Unknown extended REQ_KEY request from %s (%s): %s", from->name, from->hostname, request);
197                         return true;
198         }
199 }
200
201 bool req_key_h(connection_t *c, const char *request) {
202         char from_name[MAX_STRING_SIZE];
203         char to_name[MAX_STRING_SIZE];
204         node_t *from, *to;
205         int reqno = 0;
206
207         if(sscanf(request, "%*d " MAX_STRING " " MAX_STRING " %d", from_name, to_name, &reqno) < 2) {
208                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "REQ_KEY", c->name,
209                            c->hostname);
210                 return false;
211         }
212
213         if(!check_id(from_name) || !check_id(to_name)) {
214                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "REQ_KEY", c->name, c->hostname, "invalid name");
215                 return false;
216         }
217
218         from = lookup_node(from_name);
219
220         if(!from) {
221                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
222                            "REQ_KEY", c->name, c->hostname, from_name);
223                 return true;
224         }
225
226         to = lookup_node(to_name);
227
228         if(!to) {
229                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
230                            "REQ_KEY", c->name, c->hostname, to_name);
231                 return true;
232         }
233
234         /* Check if this key request is for us */
235
236         if(to == myself) {                      /* Yes */
237                 /* Is this an extended REQ_KEY message? */
238                 if(experimental && reqno)
239                         return req_key_ext_h(c, request, from, reqno);
240
241                 /* No, just send our key back */
242                 send_ans_key(from);
243         } else {
244                 if(tunnelserver)
245                         return true;
246
247                 if(!to->status.reachable) {
248                         logger(DEBUG_PROTOCOL, LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
249                                 "REQ_KEY", c->name, c->hostname, to_name);
250                         return true;
251                 }
252
253                 send_request(to->nexthop->connection, "%s", request);
254         }
255
256         return true;
257 }
258
259 bool send_ans_key(node_t *to) {
260         if(to->status.sptps)
261                 abort();
262
263         size_t keylen = cipher_keylength(myself->incipher);
264         char key[keylen * 2 + 1];
265
266         cipher_close(to->incipher);
267         digest_close(to->indigest);
268
269         to->incipher = cipher_open_by_nid(cipher_get_nid(myself->incipher));
270         to->indigest = digest_open_by_nid(digest_get_nid(myself->indigest), digest_length(myself->indigest));
271         to->incompression = myself->incompression;
272
273         if(!to->incipher || !to->indigest)
274                 abort();
275
276         randomize(key, keylen);
277         if(!cipher_set_key(to->incipher, key, false))
278                 abort();
279         if(!digest_set_key(to->indigest, key, keylen))
280                 abort();
281
282         bin2hex(key, key, keylen);
283
284         // Reset sequence number and late packet window
285         mykeyused = true;
286         to->received_seqno = 0;
287         to->received = 0;
288         if(replaywin) memset(to->late, 0, replaywin);
289
290         return send_request(to->nexthop->connection, "%d %s %s %s %d %d %d %d", ANS_KEY,
291                                                 myself->name, to->name, key,
292                                                 cipher_get_nid(to->incipher),
293                                                 digest_get_nid(to->indigest),
294                                                 (int)digest_length(to->indigest),
295                                                 to->incompression);
296 }
297
298 bool ans_key_h(connection_t *c, const char *request) {
299         char from_name[MAX_STRING_SIZE];
300         char to_name[MAX_STRING_SIZE];
301         char key[MAX_STRING_SIZE];
302         char address[MAX_STRING_SIZE] = "";
303         char port[MAX_STRING_SIZE] = "";
304         int cipher, digest, maclength, compression, keylen;
305         node_t *from, *to;
306
307         if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING,
308                 from_name, to_name, key, &cipher, &digest, &maclength,
309                 &compression, address, port) < 7) {
310                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
311                            c->hostname);
312                 return false;
313         }
314
315         if(!check_id(from_name) || !check_id(to_name)) {
316                 logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "ANS_KEY", c->name, c->hostname, "invalid name");
317                 return false;
318         }
319
320         from = lookup_node(from_name);
321
322         if(!from) {
323                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) origin %s which does not exist in our connection list",
324                            "ANS_KEY", c->name, c->hostname, from_name);
325                 return true;
326         }
327
328         to = lookup_node(to_name);
329
330         if(!to) {
331                 logger(DEBUG_ALWAYS, LOG_ERR, "Got %s from %s (%s) destination %s which does not exist in our connection list",
332                            "ANS_KEY", c->name, c->hostname, to_name);
333                 return true;
334         }
335
336         /* Forward it if necessary */
337
338         if(to != myself) {
339                 if(tunnelserver)
340                         return true;
341
342                 if(!to->status.reachable) {
343                         logger(DEBUG_ALWAYS, LOG_WARNING, "Got %s from %s (%s) destination %s which is not reachable",
344                                    "ANS_KEY", c->name, c->hostname, to_name);
345                         return true;
346                 }
347
348                 if(!*address && from->address.sa.sa_family != AF_UNSPEC) {
349                         char *address, *port;
350                         logger(DEBUG_PROTOCOL, LOG_DEBUG, "Appending reflexive UDP address to ANS_KEY from %s to %s", from->name, to->name);
351                         sockaddr2str(&from->address, &address, &port);
352                         send_request(to->nexthop->connection, "%s %s %s", request, address, port);
353                         free(address);
354                         free(port);
355                         return true;
356                 }
357
358                 return send_request(to->nexthop->connection, "%s", request);
359         }
360
361         /* Don't use key material until every check has passed. */
362         cipher_close(from->outcipher);
363         digest_close(from->outdigest);
364         from->status.validkey = false;
365
366         if(compression < 0 || compression > 11) {
367                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses bogus compression level!", from->name, from->hostname);
368                 return true;
369         }
370
371         from->outcompression = compression;
372
373         /* SPTPS or old-style key exchange? */
374
375         if(from->status.sptps) {
376                 char buf[strlen(key)];
377                 int len = b64decode(key, buf, strlen(key));
378
379                 if(!len || !sptps_receive_data(&from->sptps, buf, len))
380                         logger(DEBUG_ALWAYS, LOG_ERR, "Error processing SPTPS data from %s (%s)", from->name, from->hostname);
381
382                 if(from->status.validkey) {
383                         if(*address && *port) {
384                                 logger(DEBUG_PROTOCOL, LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
385                                 sockaddr_t sa = str2sockaddr(address, port);
386                                 update_node_udp(from, &sa);
387                         }
388
389                         if(from->options & OPTION_PMTU_DISCOVERY && !(from->options & OPTION_TCPONLY))
390                                 send_mtu_probe(from);
391                 }
392
393                 return true;
394         }
395
396         /* Check and lookup cipher and digest algorithms */
397
398         if(!(from->outcipher = cipher_open_by_nid(cipher))) {
399                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses unknown cipher!", from->name, from->hostname);
400                 return false;
401         }
402
403         if(!(from->outdigest = digest_open_by_nid(digest, maclength))) {
404                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses unknown digest!", from->name, from->hostname);
405                 return false;
406         }
407
408         if(maclength != digest_length(from->outdigest)) {
409                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses bogus MAC length!", from->name, from->hostname);
410                 return false;
411         }
412
413         /* Process key */
414
415         keylen = hex2bin(key, key, sizeof key);
416
417         if(keylen != cipher_keylength(from->outcipher)) {
418                 logger(DEBUG_ALWAYS, LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
419                 return true;
420         }
421
422         /* Update our copy of the origin's packet key */
423
424         if(!cipher_set_key(from->outcipher, key, true))
425                 return false;
426         if(!digest_set_key(from->outdigest, key, keylen))
427                 return false;
428
429         from->status.validkey = true;
430         from->sent_seqno = 0;
431
432         if(*address && *port) {
433                 logger(DEBUG_PROTOCOL, LOG_DEBUG, "Using reflexive UDP address from %s: %s port %s", from->name, address, port);
434                 sockaddr_t sa = str2sockaddr(address, port);
435                 update_node_udp(from, &sa);
436         }
437
438         if(from->options & OPTION_PMTU_DISCOVERY && !(from->options & OPTION_TCPONLY))
439                 send_mtu_probe(from);
440
441         return true;
442 }