410c8acf |
1 | /* -*-c-*- |
2 | * |
56814747 |
3 | * $Id: keyexch.c,v 1.3 2001/06/19 22:07:09 mdw Exp $ |
410c8acf |
4 | * |
5 | * Key exchange protocol |
6 | * |
7 | * (c) 2001 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Trivial IP Encryption (TrIPE). |
13 | * |
14 | * TrIPE is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * TrIPE is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
25 | * along with TrIPE; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | */ |
28 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: keyexch.c,v $ |
56814747 |
32 | * Revision 1.3 2001/06/19 22:07:09 mdw |
33 | * Cosmetic fixes. |
34 | * |
0617b6e7 |
35 | * Revision 1.2 2001/02/16 21:24:27 mdw |
36 | * Rewrite for new key exchange protocol. |
37 | * |
410c8acf |
38 | * Revision 1.1 2001/02/03 20:26:37 mdw |
39 | * Initial checkin. |
40 | * |
41 | */ |
42 | |
43 | /*----- Header files ------------------------------------------------------*/ |
44 | |
45 | #include "tripe.h" |
46 | |
47 | /*----- Tunable parameters ------------------------------------------------*/ |
48 | |
49 | #define T_VALID MIN(2) |
410c8acf |
50 | #define T_RETRY SEC(10) |
410c8acf |
51 | |
0617b6e7 |
52 | #define ISVALID(kx, now) ((now) < (kx)->t_valid) |
53 | |
54 | /*----- Various utilities -------------------------------------------------*/ |
410c8acf |
55 | |
56 | /* --- @hashmp@ --- * |
57 | * |
0617b6e7 |
58 | * Arguments: @HASH_CTX *r@ = pointer to hash context |
410c8acf |
59 | * @mp *m@ = pointer to multiprecision integer |
60 | * |
61 | * Returns: --- |
62 | * |
63 | * Use: Adds the hash of a multiprecision integer to the context. |
0617b6e7 |
64 | * Corrupts @buf_t@. |
410c8acf |
65 | */ |
66 | |
0617b6e7 |
67 | static void hashmp(HASH_CTX *r, mp *m) |
410c8acf |
68 | { |
69 | buf b; |
0617b6e7 |
70 | buf_init(&b, buf_t, sizeof(buf_t)); |
410c8acf |
71 | buf_putmp(&b, m); |
72 | assert(BOK(&b)); |
0617b6e7 |
73 | HASH(r, BBASE(&b), BLEN(&b)); |
410c8acf |
74 | } |
75 | |
76 | /* --- @timer@ --- * |
77 | * |
78 | * Arguments: @struct timeval *tv@ = the current time |
79 | * @void *v@ = pointer to key exchange context |
80 | * |
81 | * Returns: --- |
82 | * |
83 | * Use: Acts when the key exchange timer goes off. |
84 | */ |
85 | |
86 | static void timer(struct timeval *tv, void *v) |
87 | { |
88 | keyexch *kx = v; |
89 | kx->f &= ~KXF_TIMER; |
90 | T( trace(T_KEYEXCH, "keyexch: timer has popped"); ) |
91 | kx_start(kx); |
92 | } |
93 | |
94 | /* --- @settimer@ --- * |
95 | * |
96 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
97 | * @time_t t@ = when to set the timer for |
98 | * |
99 | * Returns: --- |
100 | * |
101 | * Use: Sets the timer for the next key exchange attempt. |
102 | */ |
103 | |
104 | static void settimer(keyexch *kx, time_t t) |
105 | { |
106 | struct timeval tv; |
107 | if (kx->f & KXF_TIMER) |
108 | sel_rmtimer(&kx->t); |
109 | tv.tv_sec = t; |
110 | tv.tv_usec = 0; |
111 | sel_addtimer(&sel, &kx->t, &tv, timer, kx); |
112 | kx->f |= KXF_TIMER; |
113 | } |
114 | |
0617b6e7 |
115 | /*----- Challenge management ----------------------------------------------*/ |
116 | |
117 | /* --- Notes on challenge management --- * |
410c8acf |
118 | * |
0617b6e7 |
119 | * We may get multiple different replies to our key exchange; some will be |
120 | * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges |
121 | * received will be added to the table and given a full response. After |
122 | * @KX_THRESH@ distinct challenges are received, we return only a `cookie': |
123 | * our existing challenge, followed by a hash of the sender's challenge. We |
124 | * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All |
125 | * properly-formed cookies are assigned a table slot: if none is spare, a |
126 | * used slot is randomly selected and destroyed. A cookie always receives a |
127 | * full reply. |
128 | */ |
129 | |
130 | /* --- @kxc_destroy@ --- * |
131 | * |
132 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
410c8acf |
133 | * |
134 | * Returns: --- |
135 | * |
0617b6e7 |
136 | * Use: Disposes of a challenge block. |
410c8acf |
137 | */ |
138 | |
0617b6e7 |
139 | static void kxc_destroy(kxchal *kxc) |
410c8acf |
140 | { |
0617b6e7 |
141 | if (kxc->f & KXF_TIMER) |
142 | sel_rmtimer(&kxc->t); |
143 | mp_drop(kxc->c); |
144 | mp_drop(kxc->r); |
145 | ks_drop(kxc->ks); |
146 | DESTROY(kxc); |
147 | } |
410c8acf |
148 | |
0617b6e7 |
149 | /* --- @kxc_stoptimer@ --- * |
150 | * |
151 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
152 | * |
153 | * Returns: --- |
154 | * |
155 | * Use: Stops the challenge's retry timer from sending messages. |
156 | * Useful when the state machine is in the endgame of the |
157 | * exchange. |
158 | */ |
410c8acf |
159 | |
0617b6e7 |
160 | static void kxc_stoptimer(kxchal *kxc) |
161 | { |
162 | if (kxc->f & KXF_TIMER) |
163 | sel_rmtimer(&kxc->t); |
164 | } |
410c8acf |
165 | |
0617b6e7 |
166 | /* --- @kxc_new@ --- * |
167 | * |
168 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
0617b6e7 |
169 | * |
170 | * Returns: A pointer to the challenge block. |
171 | * |
172 | * Use: Returns a pointer to a new challenge block to fill in. |
173 | */ |
410c8acf |
174 | |
0617b6e7 |
175 | static kxchal *kxc_new(keyexch *kx) |
176 | { |
177 | kxchal *kxc; |
178 | unsigned i; |
179 | |
180 | /* --- If we're over reply threshold, discard one at random --- */ |
181 | |
182 | if (kx->nr < KX_NCHAL) |
183 | i = kx->nr++; |
184 | else { |
185 | i = rand_global.ops->range(&rand_global, KX_NCHAL); |
186 | kxc_destroy(kx->r[i]); |
410c8acf |
187 | } |
188 | |
0617b6e7 |
189 | /* --- Fill in the new structure --- */ |
410c8acf |
190 | |
0617b6e7 |
191 | kxc = CREATE(kxchal); |
192 | kxc->c = 0; |
193 | kxc->r = 0; |
194 | kxc->ks = 0; |
195 | kxc->kx = kx; |
196 | kxc->f = 0; |
197 | kx->r[i] = kxc; |
198 | return (kxc); |
199 | } |
410c8acf |
200 | |
0617b6e7 |
201 | /* --- @kxc_bychal@ --- * |
202 | * |
203 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
204 | * @mp *c@ = challenge from remote host |
205 | * |
206 | * Returns: Pointer to the challenge block, or null. |
207 | * |
208 | * Use: Finds a challenge block, given its challenge. |
209 | */ |
210 | |
211 | static kxchal *kxc_bychal(keyexch *kx, mp *c) |
212 | { |
213 | unsigned i; |
214 | |
215 | for (i = 0; i < kx->nr; i++) { |
216 | if (MP_EQ(c, kx->r[i]->c)) |
217 | return (kx->r[i]); |
218 | } |
219 | return (0); |
220 | } |
221 | |
222 | /* --- @kxc_byhc@ --- * |
223 | * |
224 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
225 | * @const octet *hc@ = challenge hash from remote host |
226 | * |
227 | * Returns: Pointer to the challenge block, or null. |
228 | * |
229 | * Use: Finds a challenge block, given a hash of its challenge. |
230 | */ |
410c8acf |
231 | |
0617b6e7 |
232 | static kxchal *kxc_byhc(keyexch *kx, const octet *hc) |
233 | { |
234 | unsigned i; |
235 | |
236 | for (i = 0; i < kx->nr; i++) { |
237 | if (memcmp(hc, kx->r[i]->hc, HASHSZ) == 0) |
238 | return (kx->r[i]); |
410c8acf |
239 | } |
0617b6e7 |
240 | return (0); |
241 | } |
242 | |
243 | /* --- @kxc_answer@ --- * |
244 | * |
245 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
246 | * @kxchal *kxc@ = pointer to challenge block |
247 | * |
248 | * Returns: --- |
249 | * |
250 | * Use: Sends a reply to the remote host, according to the data in |
251 | * this challenge block. |
252 | */ |
253 | |
254 | static void kxc_answer(keyexch *kx, kxchal *kxc); |
255 | |
256 | static void kxc_timer(struct timeval *tv, void *v) |
257 | { |
258 | kxchal *kxc = v; |
259 | kxc->f &= ~KXF_TIMER; |
260 | kxc_answer(kxc->kx, kxc); |
261 | } |
262 | |
263 | static void kxc_answer(keyexch *kx, kxchal *kxc) |
264 | { |
265 | stats *st = p_stats(kx->p); |
266 | buf *b = p_txstart(kx->p, MSG_KEYEXCH | (kxc->r ? KX_REPLY : KX_CHAL)); |
267 | struct timeval tv; |
268 | buf bb; |
269 | |
270 | /* --- Build the reply packet --- */ |
271 | |
272 | if (!kxc->r) |
273 | buf_putmp(b, kx->c); |
274 | else |
275 | buf_put(b, kx->hc, HASHSZ); |
276 | buf_put(b, kxc->hc, HASHSZ); |
277 | buf_put(b, kxc->hrx, HASHSZ); |
278 | |
279 | /* --- Maybe send an actual reply, if we have one --- */ |
410c8acf |
280 | |
0617b6e7 |
281 | if (!kxc->r) { |
282 | T( trace(T_KEYEXCH, "keyexch: resending challenge to `%s'", |
283 | p_name(kx->p)); ) |
284 | } else { |
285 | T( trace(T_KEYEXCH, "keyexch: sending reply to `%s'", p_name(kx->p)); ) |
286 | buf_init(&bb, buf_i, sizeof(buf_i)); |
287 | buf_putmp(&bb, kxc->r); |
288 | buf_flip(&bb); |
289 | ks_encrypt(kxc->ks, &bb, b); |
290 | } |
291 | |
292 | /* --- Update the statistics --- */ |
293 | |
294 | if (BOK(b)) { |
295 | st->n_kxout++; |
296 | st->sz_kxout += BLEN(b); |
297 | p_txend(kx->p); |
298 | } |
299 | |
300 | /* --- Schedule another resend --- */ |
301 | |
302 | if (kxc->f & KXF_TIMER) |
303 | sel_rmtimer(&kxc->t); |
304 | gettimeofday(&tv, 0); |
305 | tv.tv_sec += T_RETRY; |
306 | sel_addtimer(&sel, &kxc->t, &tv, kxc_timer, kxc); |
307 | kxc->f |= KXF_TIMER; |
308 | } |
309 | |
310 | /*----- Individual message handlers ---------------------------------------*/ |
311 | |
312 | /* --- @getreply@ --- * |
313 | * |
314 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
315 | * @mp *c@ = a challenge |
316 | * @const octet *hrx@ = the supplied expected-reply hash |
317 | * |
318 | * Returns: A pointer to the reply, or null if the reply-hash was wrong. |
319 | * |
320 | * Use: Computes replies to challenges. |
321 | */ |
322 | |
323 | static mp *getreply(keyexch *kx, mp *c, const octet *hrx) |
324 | { |
325 | mp *r = mpmont_exp(&mg, MP_NEW, c, kpriv.x); |
326 | HASH_CTX h; |
327 | octet buf[HASHSZ]; |
328 | |
329 | HASH_INIT(&h); |
330 | HASH_STRING(&h, "tripe-expected-reply"); |
331 | hashmp(&h, c); |
332 | hashmp(&h, kx->c); |
333 | hashmp(&h, r); |
334 | HASH_DONE(&h, buf); |
335 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
336 | trace(T_CRYPTO, "crypto: computed reply = %s", mpstr(r)); |
337 | trace_block(T_CRYPTO, "crypto: computed reply hash", buf, HASHSZ); |
338 | })) |
339 | if (memcmp(buf, hrx, HASHSZ) != 0) { |
340 | a_warn("invalid expected-reply hash from `%s'", p_name(kx->p)); |
341 | mp_drop(r); |
342 | return (0); |
343 | } |
344 | return (r); |
345 | } |
346 | |
347 | /* --- @dochallenge@ --- * |
348 | * |
349 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
350 | * @unsigned msg@ = message code for the packet |
351 | * @buf *b@ = buffer containing the packet |
352 | * |
353 | * Returns: Zero if OK, nonzero if the packet was rejected. |
354 | * |
355 | * Use: Processes a packet containing a challenge. |
356 | */ |
357 | |
358 | static int dochallenge(keyexch *kx, unsigned msg, buf *b) |
359 | { |
360 | mp *c = 0; |
361 | const octet *hc = 0, *hrx = 0; |
362 | kxchal *kxc; |
363 | HASH_CTX h; |
364 | |
365 | /* --- Ensure that we're in a sensible state --- */ |
366 | |
367 | if (kx->s != KXS_CHAL) { |
368 | a_warn("unexpected challenge from `%s'", p_name(kx->p)); |
369 | goto bad; |
370 | } |
371 | |
372 | /* --- Unpack the packet --- */ |
373 | |
374 | if ((c = buf_getmp(b)) == 0 || |
375 | (msg >= KX_COOKIE && (hc = buf_get(b, HASHSZ)) == 0) || |
376 | (msg >= KX_CHAL && (hrx = buf_get(b, HASHSZ)) == 0) || |
377 | BLEFT(b)) { |
378 | a_warn("malformed packet from `%s'", p_name(kx->p)); |
379 | goto bad; |
380 | } |
381 | |
382 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
383 | trace(T_CRYPTO, "crypto: challenge = %s", mpstr(c)); |
384 | if (hc) trace_block(T_CRYPTO, "crypto: cookie", hc, HASHSZ); |
385 | if (hrx) trace_block(T_CRYPTO, "crypto: response hash", hrx, HASHSZ); |
386 | })) |
387 | |
388 | /* --- First, handle a bare challenge --- * |
389 | * |
390 | * If the table is heavily loaded, just emit a cookie and return. |
391 | */ |
392 | |
393 | if (!hc && kx->nr >= KX_THRESH) { |
394 | T( trace(T_KEYEXCH, "keyexch: too many challenges -- sending cookie"); ) |
395 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_COOKIE); |
396 | buf_putmp(b, kx->c); |
397 | HASH_INIT(&h); |
398 | HASH_STRING(&h, "tripe-cookie"); |
399 | hashmp(&h, c); |
400 | HASH_DONE(&h, buf_get(b, HASHSZ)); |
401 | p_txend(kx->p); |
402 | goto tidy; |
403 | } |
404 | |
405 | /* --- Discard a packet with an invalid cookie --- */ |
406 | |
407 | if (hc && memcmp(hc, kx->hc, HASHSZ) != 0) { |
408 | a_warn("incorrect cookie from `%s'", p_name(kx->p)); |
409 | goto bad; |
410 | } |
411 | |
412 | /* --- Find a challenge block for this packet --- * |
410c8acf |
413 | * |
0617b6e7 |
414 | * If there isn't one already, create a new one. |
410c8acf |
415 | */ |
416 | |
0617b6e7 |
417 | if ((kxc = kxc_bychal(kx, c)) == 0) { |
418 | size_t x, y, z; |
419 | mp *r; |
420 | |
421 | /* --- Be careful here --- * |
422 | * |
423 | * If this is a full challenge, and it's the first time I've seen it, I |
424 | * want to be able to throw it away before committing a table entry to |
425 | * it. |
426 | */ |
427 | |
428 | if (!hrx) |
429 | kxc = kxc_new(kx); |
430 | else { |
431 | if ((r = getreply(kx, c, hrx)) == 0) |
432 | goto bad; |
433 | kxc = kxc_new(kx); |
434 | kxc->r = r; |
410c8acf |
435 | } |
0617b6e7 |
436 | kxc->c = mp_copy(c); |
437 | |
438 | /* --- Work out the cookie for this challenge --- */ |
439 | |
440 | HASH_INIT(&h); |
441 | HASH_STRING(&h, "tripe-cookie"); |
442 | hashmp(&h, kxc->c); |
443 | HASH_DONE(&h, kxc->hc); |
444 | |
445 | /* --- Compute the expected-reply hash --- */ |
446 | |
447 | HASH_INIT(&h); |
448 | HASH_STRING(&h, "tripe-expected-reply"); |
449 | hashmp(&h, kx->c); |
450 | hashmp(&h, kxc->c); |
451 | hashmp(&h, kx->rx); |
452 | HASH_DONE(&h, kxc->hrx); |
453 | |
454 | /* --- Work out the shared key --- */ |
455 | |
456 | r = mpmont_exp(&mg, MP_NEW, c, kx->alpha); |
457 | |
458 | /* --- Compute the switch messages --- */ |
459 | |
460 | HASH_INIT(&h); HASH_STRING(&h, "tripe-switch-request"); |
461 | hashmp(&h, kx->c); hashmp(&h, kxc->c); |
462 | HASH_DONE(&h, kxc->hswrq_out); |
463 | HASH_INIT(&h); HASH_STRING(&h, "tripe-switch-confirm"); |
464 | hashmp(&h, kx->c); hashmp(&h, kxc->c); |
465 | HASH_DONE(&h, kxc->hswok_out); |
466 | |
467 | HASH_INIT(&h); HASH_STRING(&h, "tripe-switch-request"); |
468 | hashmp(&h, kxc->c); hashmp(&h, kx->c); |
469 | HASH_DONE(&h, kxc->hswrq_in); |
470 | HASH_INIT(&h); HASH_STRING(&h, "tripe-switch-confirm"); |
471 | hashmp(&h, kxc->c); hashmp(&h, kx->c); |
472 | HASH_DONE(&h, kxc->hswok_in); |
473 | |
474 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
475 | trace_block(T_CRYPTO, "crypto: computed cookie", kxc->hc, HASHSZ); |
476 | trace_block(T_CRYPTO, "crypto: my reply hash", kxc->hrx, HASHSZ); |
477 | trace(T_CRYPTO, "crypto: shared secret = %s", mpstr(r)); |
478 | trace_block(T_CRYPTO, "crypto: outbound switch request", |
479 | kxc->hswrq_out, HASHSZ); |
480 | trace_block(T_CRYPTO, "crypto: outbound switch confirm", |
481 | kxc->hswok_out, HASHSZ); |
482 | trace_block(T_CRYPTO, "crypto: inbound switch request", |
483 | kxc->hswrq_in, HASHSZ); |
484 | trace_block(T_CRYPTO, "crypto: inbound switch confirm", |
485 | kxc->hswok_in, HASHSZ); |
486 | })) |
487 | |
488 | /* --- Create a new symmetric keyset --- */ |
489 | |
490 | buf_init(b, buf_o, sizeof(buf_o)); |
491 | buf_putmp(b, kx->c); x = BLEN(b); |
492 | buf_putmp(b, kxc->c); y = BLEN(b); |
493 | buf_putmp(b, r); z = BLEN(b); |
494 | assert(BOK(b)); |
495 | |
496 | kxc->ks = ks_gen(BBASE(b), x, y, z); |
497 | mp_drop(r); |
410c8acf |
498 | } |
499 | |
0617b6e7 |
500 | /* --- Answer the challenge if we need to --- */ |
410c8acf |
501 | |
0617b6e7 |
502 | if (hrx && !kxc->r) { |
503 | mp *r; |
504 | if ((r = getreply(kx, c, hrx)) == 0) |
505 | goto bad; |
506 | kxc->r = r; |
410c8acf |
507 | } |
0617b6e7 |
508 | |
509 | kxc_answer(kx, kxc); |
510 | |
511 | /* --- Tidy up and go home --- */ |
512 | |
513 | tidy: |
514 | mp_drop(c); |
515 | return (0); |
516 | |
517 | bad: |
518 | mp_drop(c); |
519 | return (-1); |
410c8acf |
520 | } |
521 | |
0617b6e7 |
522 | /* --- @resend@ --- * |
410c8acf |
523 | * |
524 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
410c8acf |
525 | * |
526 | * Returns: --- |
527 | * |
0617b6e7 |
528 | * Use: Sends the next message for a key exchange. |
410c8acf |
529 | */ |
530 | |
0617b6e7 |
531 | static void resend(keyexch *kx) |
410c8acf |
532 | { |
0617b6e7 |
533 | kxchal *kxc; |
534 | buf bb; |
535 | stats *st = p_stats(kx->p); |
410c8acf |
536 | buf *b; |
537 | |
0617b6e7 |
538 | switch (kx->s) { |
539 | case KXS_CHAL: |
540 | T( trace(T_KEYEXCH, "sending prechallenge to `%s'", p_name(kx->p)); ) |
541 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL); |
542 | buf_putmp(b, kx->c); |
543 | break; |
544 | case KXS_COMMIT: |
545 | T( trace(T_KEYEXCH, "sending switch request to `%s'", p_name(kx->p)); ) |
546 | kxc = kx->r[0]; |
547 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH); |
548 | buf_put(b, kx->hc, HASHSZ); |
549 | buf_put(b, kxc->hc, HASHSZ); |
550 | buf_init(&bb, buf_i, sizeof(buf_i)); |
551 | buf_putmp(&bb, kxc->r); |
552 | buf_put(&bb, kxc->hswrq_out, HASHSZ); |
553 | buf_flip(&bb); |
554 | ks_encrypt(kxc->ks, &bb, b); |
555 | break; |
556 | case KXS_SWITCH: |
557 | T( trace(T_KEYEXCH, "sending switch confirmation to `%s'", |
558 | p_name(kx->p)); ) |
559 | kxc = kx->r[0]; |
560 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK); |
561 | buf_init(&bb, buf_i, sizeof(buf_i)); |
562 | buf_put(&bb, kxc->hswok_out, HASHSZ); |
563 | buf_flip(&bb); |
564 | ks_encrypt(kxc->ks, &bb, b); |
565 | break; |
566 | default: |
567 | abort(); |
410c8acf |
568 | } |
0617b6e7 |
569 | |
570 | if (BOK(b)) { |
571 | st->n_kxout++; |
572 | st->sz_kxout += BLEN(b); |
573 | p_txend(kx->p); |
574 | } |
575 | |
576 | if (kx->s < KXS_SWITCH) |
577 | settimer(kx, time(0) + T_RETRY); |
410c8acf |
578 | } |
579 | |
0617b6e7 |
580 | /* --- @matchreply@ --- * |
581 | * |
582 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
583 | * @const octet *hc_in@ = a hash of his challenge |
584 | * @const octet *hc_out@ = a hash of my challenge (cookie) |
585 | * @const octet *krx@ = his expected-reply hash (optional) |
586 | * @buf *b@ = encrypted remainder of the packet |
587 | * |
588 | * Returns: A pointer to the challenge block if OK, or null on failure. |
589 | * |
590 | * Use: Checks a reply or switch packet, ensuring that its contents |
591 | * are sensible and correct. If they are, @*b@ is set to point |
592 | * to the remainder of the encrypted data, and the correct |
593 | * challenge is returned. |
594 | */ |
595 | |
596 | static kxchal *matchreply(keyexch *kx, const octet *hc_in, |
597 | const octet *hc_out, const octet *hrx, buf *b) |
410c8acf |
598 | { |
0617b6e7 |
599 | kxchal *kxc; |
600 | buf bb; |
601 | mp *r = 0; |
602 | |
603 | /* --- Check the plaintext portions of the data --- */ |
604 | |
605 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
606 | trace_block(T_CRYPTO, "crypto: challenge", hc_in, HASHSZ); |
607 | trace_block(T_CRYPTO, "crypto: cookie", hc_out, HASHSZ); |
608 | if (hrx) trace_block(T_CRYPTO, "crypto: response hash", hrx, HASHSZ); |
609 | })) |
610 | if (memcmp(hc_out, kx->hc, HASHSZ) != 0) { |
611 | a_warn("incorrect cookie from `%s'", p_name(kx->p)); |
612 | goto bad; |
613 | } |
614 | if ((kxc = kxc_byhc(kx, hc_in)) == 0) { |
615 | a_warn("received reply for unknown challenge from `%s'", p_name(kx->p)); |
616 | goto bad; |
617 | } |
410c8acf |
618 | |
0617b6e7 |
619 | /* --- Maybe compute a reply for the challenge --- */ |
620 | |
621 | if (!kxc->r) { |
622 | if (!hrx) { |
623 | a_warn("unexpected switch request from `%s'", p_name(kx->p)); |
624 | goto bad; |
625 | } |
626 | if ((r = getreply(kx, kxc->c, hrx)) == 0) |
627 | goto bad; |
628 | kxc->r = r; |
629 | r = 0; |
630 | } |
631 | |
632 | /* --- Decrypt the rest of the packet --- */ |
633 | |
634 | buf_init(&bb, buf_o, sizeof(buf_o)); |
635 | if (ks_decrypt(kxc->ks, b, &bb)) { |
636 | a_warn("failed to decrypt reply from `%s'", p_name(kx->p)); |
637 | goto bad; |
410c8acf |
638 | } |
0617b6e7 |
639 | buf_init(b, BBASE(&bb), BLEN(&bb)); |
640 | if ((r = buf_getmp(b)) == 0) { |
641 | a_warn("invalid reply packet from `%s'", p_name(kx->p)); |
642 | goto bad; |
643 | } |
644 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
645 | trace(T_CRYPTO, "crypto: reply = %s", mpstr(r)); |
646 | })) |
647 | if (!mp_eq(r, kx->rx)) { |
648 | a_warn("incorrect reply from `%s'", p_name(kx->p)); |
649 | goto bad; |
650 | } |
651 | |
652 | /* --- Done --- */ |
653 | |
654 | mp_drop(r); |
655 | return (kxc); |
656 | |
657 | bad: |
658 | mp_drop(r); |
659 | return (0); |
410c8acf |
660 | } |
661 | |
0617b6e7 |
662 | /* --- @commit@ --- * |
410c8acf |
663 | * |
664 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
0617b6e7 |
665 | * @kxchal *kxc@ = pointer to challenge to commit to |
410c8acf |
666 | * |
667 | * Returns: --- |
668 | * |
0617b6e7 |
669 | * Use: Commits to a particular challenge as being the `right' one, |
670 | * since a reply has arrived for it. |
410c8acf |
671 | */ |
672 | |
0617b6e7 |
673 | static void commit(keyexch *kx, kxchal *kxc) |
410c8acf |
674 | { |
0617b6e7 |
675 | unsigned i; |
410c8acf |
676 | |
0617b6e7 |
677 | for (i = 0; i < kx->nr; i++) { |
678 | if (kx->r[i] != kxc) |
679 | kxc_destroy(kx->r[i]); |
680 | } |
681 | kx->r[0] = kxc; |
682 | kx->nr = 1; |
683 | kxc_stoptimer(kxc); |
684 | ksl_link(kx->ks, kxc->ks); |
410c8acf |
685 | } |
686 | |
0617b6e7 |
687 | /* --- @doreply@ --- * |
410c8acf |
688 | * |
689 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
0617b6e7 |
690 | * @buf *b@ = buffer containing packet |
410c8acf |
691 | * |
0617b6e7 |
692 | * Returns: Zero if OK, nonzero if the packet was rejected. |
410c8acf |
693 | * |
0617b6e7 |
694 | * Use: Handles a reply packet. This doesn't handle the various |
695 | * switch packets: they're rather too different. |
410c8acf |
696 | */ |
697 | |
0617b6e7 |
698 | static int doreply(keyexch *kx, buf *b) |
410c8acf |
699 | { |
0617b6e7 |
700 | const octet *hc_in, *hc_out, *hrx; |
701 | kxchal *kxc; |
702 | |
703 | if (kx->s != KXS_CHAL && kx->s != KXS_COMMIT) { |
704 | a_warn("unexpected reply from `%s'", p_name(kx->p)); |
705 | goto bad; |
706 | } |
707 | if ((hc_in = buf_get(b, HASHSZ)) == 0 || |
708 | (hc_out = buf_get(b, HASHSZ)) == 0 || |
709 | (hrx = buf_get(b, HASHSZ)) == 0) { |
710 | a_warn("invalid reply packet from `%s'", p_name(kx->p)); |
711 | goto bad; |
712 | } |
713 | if ((kxc = matchreply(kx, hc_in, hc_out, hrx, b)) == 0) |
714 | goto bad; |
715 | if (BLEFT(b)) { |
716 | a_warn("invalid reply packet from `%s'", p_name(kx->p)); |
717 | goto bad; |
718 | } |
719 | if (kx->s == KXS_CHAL) { |
720 | commit(kx, kxc); |
721 | kx->s = KXS_COMMIT; |
722 | } |
723 | resend(kx); |
724 | return (0); |
725 | |
726 | bad: |
727 | return (-1); |
410c8acf |
728 | } |
729 | |
0617b6e7 |
730 | /* --- @doswitch@ --- * |
410c8acf |
731 | * |
0617b6e7 |
732 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
733 | * @buf *b@ = pointer to buffer containing packet |
410c8acf |
734 | * |
0617b6e7 |
735 | * Returns: Zero if OK, nonzero if the packet was rejected. |
410c8acf |
736 | * |
0617b6e7 |
737 | * Use: Handles a reply with a switch request bolted onto it. |
410c8acf |
738 | */ |
739 | |
0617b6e7 |
740 | static int doswitch(keyexch *kx, buf *b) |
410c8acf |
741 | { |
0617b6e7 |
742 | const octet *hc_in, *hc_out, *hswrq; |
743 | kxchal *kxc; |
410c8acf |
744 | |
0617b6e7 |
745 | if ((hc_in = buf_get(b, HASHSZ)) == 0 || |
746 | (hc_out = buf_get(b, HASHSZ)) == 0) { |
747 | a_warn("invalid switch request from `%s'", p_name(kx->p)); |
748 | goto bad; |
410c8acf |
749 | } |
0617b6e7 |
750 | if ((kxc = matchreply(kx, hc_in, hc_out, 0, b)) == 0) |
751 | goto bad; |
752 | if ((hswrq = buf_get(b, HASHSZ)) == 0 || BLEFT(b)) { |
753 | a_warn("invalid switch request from `%s'", p_name(kx->p)); |
754 | goto bad; |
755 | } |
756 | IF_TRACING(T_KEYEXCH, { |
757 | trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, HASHSZ); |
758 | }) |
759 | if (memcmp(hswrq, kxc->hswrq_in, HASHSZ) != 0) { |
760 | a_warn("incorrect switch request hash from `%s'", p_name(kx->p)); |
761 | goto bad; |
762 | } |
763 | switch (kx->s) { |
764 | case KXS_CHAL: |
765 | commit(kx, kxc); |
766 | case KXS_COMMIT: |
767 | ks_activate(kxc->ks); |
768 | settimer(kx, ks_tregen(kxc->ks)); |
769 | kx->s = KXS_SWITCH; |
770 | break; |
771 | } |
772 | resend(kx); |
773 | return (0); |
774 | |
775 | bad: |
776 | return (-1); |
410c8acf |
777 | } |
778 | |
0617b6e7 |
779 | /* --- @doswitchok@ --- * |
780 | * |
781 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
782 | * @buf *b@ = pointer to buffer containing packet |
783 | * |
784 | * Returns: Zero if OK, nonzero if the packet was rejected. |
785 | * |
786 | * Use: Handles a reply with a switch request bolted onto it. |
787 | */ |
788 | |
789 | static int doswitchok(keyexch *kx, buf *b) |
410c8acf |
790 | { |
0617b6e7 |
791 | const octet *hswok; |
792 | kxchal *kxc; |
793 | buf bb; |
410c8acf |
794 | |
0617b6e7 |
795 | if (kx->s < KXS_COMMIT) { |
796 | a_warn("unexpected switch confirmation from `%s'", p_name(kx->p)); |
797 | goto bad; |
410c8acf |
798 | } |
0617b6e7 |
799 | kxc = kx->r[0]; |
800 | buf_init(&bb, buf_o, sizeof(buf_o)); |
801 | if (ks_decrypt(kxc->ks, b, &bb)) { |
802 | a_warn("failed to decrypt switch confirmation from `%s'", p_name(kx->p)); |
803 | goto bad; |
804 | } |
805 | buf_init(b, BBASE(&bb), BLEN(&bb)); |
806 | if ((hswok = buf_get(b, HASHSZ)) == 0 || BLEFT(b)) { |
807 | a_warn("invalid switch confirmation from `%s'", p_name(kx->p)); |
808 | goto bad; |
809 | } |
810 | IF_TRACING(T_KEYEXCH, { |
811 | trace_block(T_CRYPTO, "crypto: switch confirmation hash", hswok, HASHSZ); |
812 | }) |
813 | if (memcmp(hswok, kxc->hswok_in, HASHSZ) != 0) { |
814 | a_warn("incorrect switch confirmation hash from `%s'", p_name(kx->p)); |
815 | goto bad; |
816 | } |
817 | if (kx->s < KXS_SWITCH) { |
818 | ks_activate(kxc->ks); |
819 | settimer(kx, ks_tregen(kxc->ks)); |
820 | kx->s = KXS_SWITCH; |
821 | } |
822 | return (0); |
823 | |
824 | bad: |
825 | return (-1); |
826 | } |
827 | |
828 | /*----- Main code ---------------------------------------------------------*/ |
829 | |
830 | /* --- @stop@ --- * |
831 | * |
832 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
833 | * |
834 | * Returns: --- |
835 | * |
836 | * Use: Stops a key exchange dead in its tracks. Throws away all of |
837 | * the context information. The context is left in an |
838 | * inconsistent state. The only functions which understand this |
839 | * state are @kx_free@ and @kx_init@ (which cause it internally |
840 | * it), and @start@ (which expects it to be the prevailing |
841 | * state). |
842 | */ |
843 | |
844 | static void stop(keyexch *kx) |
845 | { |
846 | unsigned i; |
847 | |
848 | if (kx->f & KXF_TIMER) |
849 | sel_rmtimer(&kx->t); |
850 | for (i = 0; i < kx->nr; i++) |
851 | kxc_destroy(kx->r[i]); |
852 | mp_drop(kx->alpha); |
853 | mp_drop(kx->c); |
854 | mp_drop(kx->rx); |
855 | } |
856 | |
857 | /* --- @start@ --- * |
858 | * |
859 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
860 | * @time_t now@ = the current time |
861 | * |
862 | * Returns: --- |
863 | * |
864 | * Use: Starts a new key exchange with the peer. The context must be |
865 | * in the bizarre state left by @stop@ or @kx_init@. |
866 | */ |
867 | |
868 | static void start(keyexch *kx, time_t now) |
869 | { |
870 | HASH_CTX h; |
871 | |
872 | kx->nr = 0; |
873 | kx->f = 0; |
874 | kx->alpha = mprand_range(MP_NEW, kpriv.dp.q, &rand_global, 0); |
875 | kx->c = mpmont_exp(&mg, MP_NEW, kpriv.dp.g, kx->alpha); |
876 | kx->rx = mpmont_exp(&mg, MP_NEW, kx->kpub.y, kx->alpha); |
877 | kx->s = KXS_CHAL; |
878 | kx->t_valid = now + T_VALID; |
879 | |
880 | HASH_INIT(&h); |
881 | HASH_STRING(&h, "tripe-cookie"); |
882 | hashmp(&h, kx->c); |
883 | HASH_DONE(&h, kx->hc); |
884 | |
885 | IF_TRACING(T_KEYEXCH, { |
886 | trace(T_KEYEXCH, "keyexch: creating new challenge"); |
887 | IF_TRACING(T_CRYPTO, { |
888 | trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha)); |
889 | trace(T_CRYPTO, "crypto: challenge = %s", mpstr(kx->c)); |
890 | trace(T_CRYPTO, "crypto: expected response = %s", mpstr(kx->rx)); |
891 | trace_block(T_CRYPTO, "crypto: challenge cookie", kx->hc, HASHSZ); |
892 | }) |
893 | }) |
410c8acf |
894 | } |
895 | |
0617b6e7 |
896 | /* --- @kx_start@ --- * |
410c8acf |
897 | * |
898 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
410c8acf |
899 | * |
900 | * Returns: --- |
901 | * |
0617b6e7 |
902 | * Use: Stimulates a key exchange. If a key exchage is in progress, |
903 | * a new challenge is sent (unless the quiet timer forbids |
904 | * this); if no exchange is in progress, one is commenced. |
410c8acf |
905 | */ |
906 | |
0617b6e7 |
907 | void kx_start(keyexch *kx) |
410c8acf |
908 | { |
909 | time_t now = time(0); |
410c8acf |
910 | |
0617b6e7 |
911 | if (!ISVALID(kx, now)) { |
912 | stop(kx); |
913 | start(kx, now); |
410c8acf |
914 | } |
0617b6e7 |
915 | resend(kx); |
916 | } |
917 | |
918 | /* --- @kx_message@ --- * |
919 | * |
920 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
921 | * @unsigned msg@ = the message code |
922 | * @buf *b@ = pointer to buffer containing the packet |
923 | * |
924 | * Returns: --- |
925 | * |
926 | * Use: Reads a packet containing key exchange messages and handles |
927 | * it. |
928 | */ |
929 | |
930 | void kx_message(keyexch *kx, unsigned msg, buf *b) |
931 | { |
932 | time_t now = time(0); |
933 | stats *st = p_stats(kx->p); |
934 | size_t sz = BSZ(b); |
935 | int rc; |
936 | |
937 | #ifndef NTRACE |
938 | static const char *const pkname[] = { |
939 | "prechallenge", "cookie", "challenge", |
940 | "reply", "switch request", "switch confirmation" |
941 | }; |
942 | #endif |
943 | |
944 | if (!ISVALID(kx, now)) { |
945 | stop(kx); |
946 | start(kx, now); |
410c8acf |
947 | } |
0617b6e7 |
948 | |
949 | T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'", |
950 | msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); ) |
951 | |
952 | switch (msg) { |
953 | case KX_PRECHAL: |
954 | case KX_COOKIE: |
955 | case KX_CHAL: |
956 | rc = dochallenge(kx, msg, b); |
957 | break; |
958 | case KX_REPLY: |
959 | rc = doreply(kx, b); |
960 | break; |
961 | case KX_SWITCH: |
962 | rc = doswitch(kx, b); |
963 | break; |
964 | case KX_SWITCHOK: |
965 | rc = doswitchok(kx, b); |
966 | break; |
967 | default: |
968 | a_warn("unexpected key exchange message type %u from `%p'", |
969 | p_name(kx->p)); |
970 | rc = -1; |
971 | break; |
410c8acf |
972 | } |
410c8acf |
973 | |
0617b6e7 |
974 | if (rc) |
975 | st->n_reject++; |
976 | else { |
977 | st->n_kxin++; |
978 | st->sz_kxin += sz; |
979 | } |
410c8acf |
980 | } |
981 | |
982 | /* --- @kx_free@ --- * |
983 | * |
984 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
985 | * |
986 | * Returns: --- |
987 | * |
988 | * Use: Frees everything in a key exchange context. |
989 | */ |
990 | |
991 | void kx_free(keyexch *kx) |
992 | { |
0617b6e7 |
993 | stop(kx); |
410c8acf |
994 | dh_pubfree(&kx->kpub); |
995 | } |
996 | |
997 | /* --- @kx_newkeys@ --- * |
998 | * |
999 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
1000 | * |
1001 | * Returns: --- |
1002 | * |
1003 | * Use: Informs the key exchange module that its keys may have |
1004 | * changed. If fetching the new keys fails, the peer will be |
1005 | * destroyed, we log messages and struggle along with the old |
1006 | * keys. |
1007 | */ |
1008 | |
1009 | void kx_newkeys(keyexch *kx) |
1010 | { |
1011 | dh_pub dp; |
1012 | |
1013 | if (km_getpubkey(p_name(kx->p), &dp)) |
1014 | return; |
1015 | dh_pubfree(&kx->kpub); |
1016 | kx->kpub = dp; |
0617b6e7 |
1017 | if (kx->s != KXS_SWITCH) { |
410c8acf |
1018 | T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'", |
1019 | p_name(kx->p)); ) |
0617b6e7 |
1020 | kx->t_valid = 0; |
1021 | kx_start(kx); |
410c8acf |
1022 | } |
1023 | } |
1024 | |
1025 | /* --- @kx_init@ --- * |
1026 | * |
1027 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
1028 | * @peer *p@ = pointer to peer context |
1029 | * @keyset **ks@ = pointer to keyset list |
1030 | * |
1031 | * Returns: Zero if OK, nonzero if it failed. |
1032 | * |
1033 | * Use: Initializes a key exchange module. The module currently |
1034 | * contains no keys, and will attempt to initiate a key |
1035 | * exchange. |
1036 | */ |
1037 | |
1038 | int kx_init(keyexch *kx, peer *p, keyset **ks) |
1039 | { |
1040 | kx->ks = ks; |
1041 | kx->p = p; |
410c8acf |
1042 | if (km_getpubkey(p_name(p), &kx->kpub)) |
1043 | return (-1); |
0617b6e7 |
1044 | start(kx, time(0)); |
1045 | resend(kx); |
410c8acf |
1046 | return (0); |
1047 | } |
1048 | |
1049 | /*----- That's all, folks -------------------------------------------------*/ |