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