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410c8acf | 1 | /* -*-c-*- |
2 | * | |
410c8acf | 3 | * Key exchange protocol |
4 | * | |
5 | * (c) 2001 Straylight/Edgeware | |
6 | */ | |
7 | ||
e04c2d50 | 8 | /*----- Licensing notice --------------------------------------------------* |
410c8acf | 9 | * |
10 | * This file is part of Trivial IP Encryption (TrIPE). | |
11 | * | |
12 | * TrIPE is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License as published by | |
14 | * the Free Software Foundation; either version 2 of the License, or | |
15 | * (at your option) any later version. | |
e04c2d50 | 16 | * |
410c8acf | 17 | * TrIPE is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU General Public License for more details. | |
e04c2d50 | 21 | * |
410c8acf | 22 | * You should have received a copy of the GNU General Public License |
23 | * along with TrIPE; if not, write to the Free Software Foundation, | |
24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | */ | |
26 | ||
410c8acf | 27 | /*----- Header files ------------------------------------------------------*/ |
28 | ||
29 | #include "tripe.h" | |
30 | ||
737cc271 | 31 | /*----- Brief protocol overview -------------------------------------------* |
32 | * | |
33 | * Let %$G$% be a cyclic group; let %$g$% be a generator of %$G$%, and let | |
34 | * %$q$% be the order of %$G$%; for a key %$K$%, let %$E_K(\cdot)$% denote | |
35 | * application of the symmetric packet protocol to a message; let | |
36 | * %$H(\cdot)$% be the random oracle. Let $\alpha \inr \{0,\ldots,q - 1\}$% | |
37 | * be Alice's private key; let %$a = g^\alpha$% be her public key; let %$b$% | |
38 | * be Bob's public key. | |
39 | * | |
40 | * At the beginning of the session, Alice chooses | |
41 | * | |
42 | * %$\rho_A \inr \{0, \ldots q - 1\}$% | |
43 | * | |
44 | * We also have: | |
45 | * | |
46 | * %$r_A = g^{\rho_A}$% Alice's challenge | |
47 | * %$c_A = H(\cookie{cookie}, r_A)$% Alice's cookie | |
9317aa92 | 48 | * %$v_A = \rho_A \xor H(\cookie{expected-reply}, a, r_A, r_B, b^{\rho_A})$% |
e04c2d50 | 49 | * Alice's challenge check value |
737cc271 | 50 | * %$r_B^\alpha = a^{\rho_B}$% Alice's reply |
51 | * %$K = r_B^{\rho_A} = r_B^{\rho_A} = g^{\rho_A\rho_B}$% | |
e04c2d50 | 52 | * Alice and Bob's shared secret key |
737cc271 | 53 | * %$w_A = H(\cookie{switch-request}, c_A, c_B)$% |
e04c2d50 | 54 | * Alice's switch request value |
737cc271 | 55 | * %$u_A = H(\cookie{switch-confirm}, c_A, c_B)$% |
e04c2d50 | 56 | * Alice's switch confirm value |
737cc271 | 57 | * |
58 | * The messages are then: | |
59 | * | |
60 | * %$\cookie{kx-pre-challenge}, r_A$% | |
61 | * Initial greeting. In state @KXS_CHAL@. | |
62 | * | |
737cc271 | 63 | * %$\cookie{kx-challenge}, r_A, c_B, v_A$% |
64 | * Here's a full challenge for you to answer. | |
65 | * | |
28461f0e | 66 | * %$\cookie{kx-reply}, r_A, c_B, v_A, E_K(r_B^\alpha))$% |
737cc271 | 67 | * Challenge accpeted: here's the answer. Commit to my challenge. Move |
68 | * to @KXS_COMMIT@. | |
69 | * | |
3cdc3f3a | 70 | * %$\cookie{kx-switch-rq}, c_A, c_B, E_K(r_B^\alpha, w_A))$% |
737cc271 | 71 | * Reply received: here's my reply. Committed; send data; move to |
72 | * @KXS_SWITCH@. | |
73 | * | |
74 | * %$\cookie{kx-switch-ok}, E_K(u_A))$% | |
75 | * Switch received. Committed; send data; move to @KXS_SWITCH@. | |
e04c2d50 | 76 | */ |
737cc271 | 77 | |
410c8acf | 78 | /*----- Tunable parameters ------------------------------------------------*/ |
79 | ||
56516aeb | 80 | #define T_VALID SEC(20) /* Challenge validity period */ |
2de0ad0f | 81 | #define T_RETRY SEC(10) /* Challenge retransmit interval */ |
410c8acf | 82 | |
3cdc3f3a | 83 | #define VALIDP(kx, now) ((now) < (kx)->t_valid) |
84 | ||
85 | /*----- Static tables -----------------------------------------------------*/ | |
86 | ||
87 | static const char *const pkname[] = { | |
c3c51798 | 88 | "pre-challenge", "challenge", "reply", "switch-rq", "switch-ok" |
3cdc3f3a | 89 | }; |
0617b6e7 | 90 | |
91 | /*----- Various utilities -------------------------------------------------*/ | |
410c8acf | 92 | |
52c03a2a | 93 | /* --- @hashge@ --- * |
410c8acf | 94 | * |
b5c45da1 | 95 | * Arguments: @ghash *h@ = pointer to hash context |
52c03a2a | 96 | * @ge *x@ = pointer to group element |
410c8acf | 97 | * |
98 | * Returns: --- | |
99 | * | |
52c03a2a | 100 | * Use: Adds the hash of a group element to the context. Corrupts |
101 | * @buf_t@. | |
410c8acf | 102 | */ |
103 | ||
b5c45da1 | 104 | static void hashge(ghash *h, ge *x) |
410c8acf | 105 | { |
106 | buf b; | |
0617b6e7 | 107 | buf_init(&b, buf_t, sizeof(buf_t)); |
52c03a2a | 108 | G_TOBUF(gg, &b, x); |
410c8acf | 109 | assert(BOK(&b)); |
b5c45da1 | 110 | GH_HASH(h, BBASE(&b), BLEN(&b)); |
410c8acf | 111 | } |
112 | ||
de7bd20b | 113 | /* --- @mpmask@ --- * |
5d418e24 | 114 | * |
de7bd20b MW |
115 | * Arguments: @buf *b@ = output buffer |
116 | * @mp *x@ = the plaintext integer | |
117 | * @size_t n@ = the expected size of the plaintext | |
5d418e24 | 118 | * @const octet *k@ = pointer to key material |
de7bd20b | 119 | * @size_t ksz@ = size of the key |
5d418e24 | 120 | * |
de7bd20b | 121 | * Returns: Pointer to the output. |
5d418e24 | 122 | * |
de7bd20b MW |
123 | * Use: Masks a multiprecision integer: returns %$x \xor H(k)$%, so |
124 | * it's a random oracle thing rather than an encryption thing. | |
5d418e24 | 125 | */ |
126 | ||
de7bd20b | 127 | static octet *mpmask(buf *b, mp *x, size_t n, const octet *k, size_t ksz) |
5d418e24 | 128 | { |
b5c45da1 | 129 | gcipher *mgf; |
de7bd20b | 130 | octet *p; |
5d418e24 | 131 | |
de7bd20b MW |
132 | if ((p = buf_get(b, n)) == 0) |
133 | return (0); | |
134 | mgf = GC_INIT(algs.mgf, k, ksz); | |
135 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
136 | trace(T_CRYPTO, "masking index = %s", mpstr(x)); | |
137 | trace_block(T_CRYPTO, "masking key", k, ksz); | |
138 | })) | |
139 | mp_storeb(x, buf_t, n); | |
140 | GC_ENCRYPT(mgf, buf_t, p, n); | |
141 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
142 | trace_block(T_CRYPTO, "index plaintext", buf_t, n); | |
143 | trace_block(T_CRYPTO, "masked ciphertext", p, n); | |
144 | })) | |
b5c45da1 | 145 | GC_DESTROY(mgf); |
de7bd20b | 146 | return (p); |
b5c45da1 | 147 | } |
148 | ||
de7bd20b MW |
149 | /* --- @mpunmask@ --- * |
150 | * | |
151 | * Arguments: @mp *d@ = the output integer | |
152 | * @const octet *p@ = pointer to the ciphertext | |
153 | * @size_t n@ = the size of the ciphertext | |
154 | * @const octet *k@ = pointer to key material | |
155 | * @size_t ksz@ = size of the key | |
156 | * | |
157 | * Returns: The decrypted integer, or null. | |
158 | * | |
159 | * Use: Unmasks a multiprecision integer. | |
160 | */ | |
161 | ||
162 | static mp *mpunmask(mp *d, const octet *p, size_t n, | |
163 | const octet *k, size_t ksz) | |
b5c45da1 | 164 | { |
165 | gcipher *mgf; | |
166 | ||
de7bd20b MW |
167 | mgf = GC_INIT(algs.mgf, k, ksz); |
168 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
169 | trace_block(T_CRYPTO, "unmasking key", k, ksz); | |
170 | trace_block(T_CRYPTO, "masked ciphertext", p, n); | |
171 | })) | |
172 | GC_DECRYPT(mgf, p, buf_t, n); | |
173 | d = mp_loadb(d, buf_t, n); | |
174 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
175 | trace_block(T_CRYPTO, "index plaintext", buf_t, n); | |
176 | trace(T_CRYPTO, "unmasked index = %s", mpstr(d)); | |
177 | })) | |
b5c45da1 | 178 | GC_DESTROY(mgf); |
de7bd20b MW |
179 | return (d); |
180 | } | |
181 | ||
182 | /* --- @hashcheck@ --- * | |
183 | * | |
184 | * Arguments: @ge *kpub@ = sender's public key | |
185 | * @ge *cc@ = receiver's challenge | |
186 | * @ge *c@ = sender's challenge | |
187 | * @ge *y@ = reply to sender's challenge | |
188 | * | |
189 | * Returns: Pointer to the hash value (in @buf_t@) | |
190 | * | |
191 | * Use: Computes the check-value hash, used to mask or unmask | |
192 | * indices to prove the validity of challenges. This computes | |
193 | * the masking key used in challenge check values. This is | |
194 | * really the heart of the whole thing, since it ensures that | |
195 | * the index can be recovered from the history of hashing | |
196 | * queries, which gives us (a) a proof that the authentication | |
197 | * process is zero-knowledge, and (b) a proof that the whole | |
198 | * key-exchange is deniable. | |
199 | */ | |
200 | ||
201 | static const octet *hashcheck(ge *kpub, ge *cc, ge *c, ge *y) | |
202 | { | |
203 | ghash *h = GH_INIT(algs.h); | |
204 | ||
205 | HASH_STRING(h, "tripe-expected-reply"); | |
206 | hashge(h, kpub); | |
207 | hashge(h, cc); | |
208 | hashge(h, c); | |
209 | hashge(h, y); | |
210 | GH_DONE(h, buf_t); | |
211 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
212 | trace(T_CRYPTO, "computing challenge check hash"); | |
213 | trace(T_CRYPTO, "public key = %s", gestr(gg, kpub)); | |
214 | trace(T_CRYPTO, "receiver challenge = %s", gestr(gg, cc)); | |
215 | trace(T_CRYPTO, "sender challenge = %s", gestr(gg, c)); | |
216 | trace(T_CRYPTO, "sender reply = %s", gestr(gg, y)); | |
217 | trace_block(T_CRYPTO, "hash output", buf_t, algs.hashsz); | |
218 | })) | |
219 | GH_DESTROY(h); | |
220 | return (buf_t); | |
221 | } | |
222 | ||
223 | /* --- @sendchallenge@ --- * | |
224 | * | |
225 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
226 | * @buf *b@ = output buffer for challenge | |
227 | * @ge *c@ = peer's actual challenge | |
228 | * @const octet *hc@ = peer's challenge cookie | |
229 | * | |
230 | * Returns: --- | |
231 | * | |
232 | * Use: Writes a full challenge to the message buffer. | |
233 | */ | |
234 | ||
235 | static void sendchallenge(keyexch *kx, buf *b, ge *c, const octet *hc) | |
236 | { | |
237 | G_TOBUF(gg, b, kx->c); | |
238 | buf_put(b, hc, algs.hashsz); | |
239 | mpmask(b, kx->alpha, indexsz, | |
240 | hashcheck(kpub, c, kx->c, kx->rx), algs.hashsz); | |
5d418e24 | 241 | } |
242 | ||
410c8acf | 243 | /* --- @timer@ --- * |
244 | * | |
245 | * Arguments: @struct timeval *tv@ = the current time | |
246 | * @void *v@ = pointer to key exchange context | |
247 | * | |
248 | * Returns: --- | |
249 | * | |
250 | * Use: Acts when the key exchange timer goes off. | |
251 | */ | |
252 | ||
253 | static void timer(struct timeval *tv, void *v) | |
254 | { | |
255 | keyexch *kx = v; | |
256 | kx->f &= ~KXF_TIMER; | |
257 | T( trace(T_KEYEXCH, "keyexch: timer has popped"); ) | |
de014da6 | 258 | kx_start(kx, 0); |
410c8acf | 259 | } |
260 | ||
261 | /* --- @settimer@ --- * | |
262 | * | |
263 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
264 | * @time_t t@ = when to set the timer for | |
265 | * | |
266 | * Returns: --- | |
267 | * | |
268 | * Use: Sets the timer for the next key exchange attempt. | |
269 | */ | |
270 | ||
271 | static void settimer(keyexch *kx, time_t t) | |
272 | { | |
273 | struct timeval tv; | |
274 | if (kx->f & KXF_TIMER) | |
275 | sel_rmtimer(&kx->t); | |
276 | tv.tv_sec = t; | |
277 | tv.tv_usec = 0; | |
278 | sel_addtimer(&sel, &kx->t, &tv, timer, kx); | |
279 | kx->f |= KXF_TIMER; | |
280 | } | |
281 | ||
0617b6e7 | 282 | /*----- Challenge management ----------------------------------------------*/ |
283 | ||
284 | /* --- Notes on challenge management --- * | |
410c8acf | 285 | * |
0617b6e7 | 286 | * We may get multiple different replies to our key exchange; some will be |
287 | * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges | |
288 | * received will be added to the table and given a full response. After | |
289 | * @KX_THRESH@ distinct challenges are received, we return only a `cookie': | |
290 | * our existing challenge, followed by a hash of the sender's challenge. We | |
291 | * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All | |
292 | * properly-formed cookies are assigned a table slot: if none is spare, a | |
293 | * used slot is randomly selected and destroyed. A cookie always receives a | |
294 | * full reply. | |
295 | */ | |
296 | ||
297 | /* --- @kxc_destroy@ --- * | |
298 | * | |
299 | * Arguments: @kxchal *kxc@ = pointer to the challenge block | |
410c8acf | 300 | * |
301 | * Returns: --- | |
302 | * | |
0617b6e7 | 303 | * Use: Disposes of a challenge block. |
410c8acf | 304 | */ |
305 | ||
0617b6e7 | 306 | static void kxc_destroy(kxchal *kxc) |
410c8acf | 307 | { |
0617b6e7 | 308 | if (kxc->f & KXF_TIMER) |
309 | sel_rmtimer(&kxc->t); | |
52c03a2a | 310 | G_DESTROY(gg, kxc->c); |
de7bd20b | 311 | G_DESTROY(gg, kxc->r); |
0617b6e7 | 312 | ks_drop(kxc->ks); |
313 | DESTROY(kxc); | |
314 | } | |
410c8acf | 315 | |
0617b6e7 | 316 | /* --- @kxc_stoptimer@ --- * |
317 | * | |
318 | * Arguments: @kxchal *kxc@ = pointer to the challenge block | |
319 | * | |
320 | * Returns: --- | |
321 | * | |
322 | * Use: Stops the challenge's retry timer from sending messages. | |
323 | * Useful when the state machine is in the endgame of the | |
324 | * exchange. | |
325 | */ | |
410c8acf | 326 | |
0617b6e7 | 327 | static void kxc_stoptimer(kxchal *kxc) |
328 | { | |
329 | if (kxc->f & KXF_TIMER) | |
330 | sel_rmtimer(&kxc->t); | |
2de0ad0f | 331 | kxc->f &= ~KXF_TIMER; |
0617b6e7 | 332 | } |
410c8acf | 333 | |
0617b6e7 | 334 | /* --- @kxc_new@ --- * |
335 | * | |
336 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
0617b6e7 | 337 | * |
338 | * Returns: A pointer to the challenge block. | |
339 | * | |
340 | * Use: Returns a pointer to a new challenge block to fill in. | |
341 | */ | |
410c8acf | 342 | |
0617b6e7 | 343 | static kxchal *kxc_new(keyexch *kx) |
344 | { | |
345 | kxchal *kxc; | |
346 | unsigned i; | |
347 | ||
348 | /* --- If we're over reply threshold, discard one at random --- */ | |
349 | ||
350 | if (kx->nr < KX_NCHAL) | |
351 | i = kx->nr++; | |
352 | else { | |
353 | i = rand_global.ops->range(&rand_global, KX_NCHAL); | |
354 | kxc_destroy(kx->r[i]); | |
410c8acf | 355 | } |
356 | ||
0617b6e7 | 357 | /* --- Fill in the new structure --- */ |
410c8acf | 358 | |
0617b6e7 | 359 | kxc = CREATE(kxchal); |
52c03a2a | 360 | kxc->c = G_CREATE(gg); |
de7bd20b | 361 | kxc->r = G_CREATE(gg); |
0617b6e7 | 362 | kxc->ks = 0; |
363 | kxc->kx = kx; | |
364 | kxc->f = 0; | |
365 | kx->r[i] = kxc; | |
366 | return (kxc); | |
367 | } | |
410c8acf | 368 | |
0617b6e7 | 369 | /* --- @kxc_bychal@ --- * |
370 | * | |
371 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
52c03a2a | 372 | * @ge *c@ = challenge from remote host |
0617b6e7 | 373 | * |
374 | * Returns: Pointer to the challenge block, or null. | |
375 | * | |
376 | * Use: Finds a challenge block, given its challenge. | |
377 | */ | |
378 | ||
52c03a2a | 379 | static kxchal *kxc_bychal(keyexch *kx, ge *c) |
0617b6e7 | 380 | { |
381 | unsigned i; | |
382 | ||
383 | for (i = 0; i < kx->nr; i++) { | |
52c03a2a | 384 | if (G_EQ(gg, c, kx->r[i]->c)) |
0617b6e7 | 385 | return (kx->r[i]); |
386 | } | |
387 | return (0); | |
388 | } | |
389 | ||
390 | /* --- @kxc_byhc@ --- * | |
391 | * | |
392 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
393 | * @const octet *hc@ = challenge hash from remote host | |
394 | * | |
395 | * Returns: Pointer to the challenge block, or null. | |
396 | * | |
397 | * Use: Finds a challenge block, given a hash of its challenge. | |
398 | */ | |
410c8acf | 399 | |
0617b6e7 | 400 | static kxchal *kxc_byhc(keyexch *kx, const octet *hc) |
401 | { | |
402 | unsigned i; | |
403 | ||
404 | for (i = 0; i < kx->nr; i++) { | |
b5c45da1 | 405 | if (memcmp(hc, kx->r[i]->hc, algs.hashsz) == 0) |
0617b6e7 | 406 | return (kx->r[i]); |
410c8acf | 407 | } |
0617b6e7 | 408 | return (0); |
409 | } | |
410 | ||
411 | /* --- @kxc_answer@ --- * | |
412 | * | |
413 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
414 | * @kxchal *kxc@ = pointer to challenge block | |
415 | * | |
416 | * Returns: --- | |
417 | * | |
418 | * Use: Sends a reply to the remote host, according to the data in | |
419 | * this challenge block. | |
420 | */ | |
421 | ||
422 | static void kxc_answer(keyexch *kx, kxchal *kxc); | |
423 | ||
424 | static void kxc_timer(struct timeval *tv, void *v) | |
425 | { | |
426 | kxchal *kxc = v; | |
427 | kxc->f &= ~KXF_TIMER; | |
428 | kxc_answer(kxc->kx, kxc); | |
429 | } | |
430 | ||
431 | static void kxc_answer(keyexch *kx, kxchal *kxc) | |
432 | { | |
433 | stats *st = p_stats(kx->p); | |
de7bd20b | 434 | buf *b = p_txstart(kx->p, MSG_KEYEXCH | KX_REPLY); |
0617b6e7 | 435 | struct timeval tv; |
436 | buf bb; | |
437 | ||
438 | /* --- Build the reply packet --- */ | |
439 | ||
de7bd20b MW |
440 | T( trace(T_KEYEXCH, "keyexch: sending reply to `%s'", p_name(kx->p)); ) |
441 | sendchallenge(kx, b, kxc->c, kxc->hc); | |
442 | buf_init(&bb, buf_i, sizeof(buf_i)); | |
443 | G_TORAW(gg, &bb, kxc->r); | |
444 | buf_flip(&bb); | |
445 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_REPLY, &bb, b); | |
0617b6e7 | 446 | |
447 | /* --- Update the statistics --- */ | |
448 | ||
449 | if (BOK(b)) { | |
450 | st->n_kxout++; | |
451 | st->sz_kxout += BLEN(b); | |
452 | p_txend(kx->p); | |
453 | } | |
454 | ||
455 | /* --- Schedule another resend --- */ | |
456 | ||
457 | if (kxc->f & KXF_TIMER) | |
458 | sel_rmtimer(&kxc->t); | |
459 | gettimeofday(&tv, 0); | |
460 | tv.tv_sec += T_RETRY; | |
461 | sel_addtimer(&sel, &kxc->t, &tv, kxc_timer, kxc); | |
462 | kxc->f |= KXF_TIMER; | |
463 | } | |
464 | ||
465 | /*----- Individual message handlers ---------------------------------------*/ | |
466 | ||
de7bd20b | 467 | /* --- @doprechallenge@ --- * |
0617b6e7 | 468 | * |
de7bd20b MW |
469 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
470 | * @buf *b@ = buffer containing the packet | |
0617b6e7 | 471 | * |
de7bd20b | 472 | * Returns: Zero if OK, nonzero of the packet was rejected. |
0617b6e7 | 473 | * |
de7bd20b | 474 | * Use: Processes a pre-challenge message. |
0617b6e7 | 475 | */ |
476 | ||
de7bd20b | 477 | static int doprechallenge(keyexch *kx, buf *b) |
0617b6e7 | 478 | { |
de7bd20b MW |
479 | stats *st = p_stats(kx->p); |
480 | ge *c = G_CREATE(gg); | |
b5c45da1 | 481 | ghash *h; |
0617b6e7 | 482 | |
de7bd20b MW |
483 | /* --- Ensure that we're in a sensible state --- */ |
484 | ||
485 | if (kx->s != KXS_CHAL) { | |
486 | a_warn("KX", "?PEER", kx->p, "unexpected", "pre-challenge", A_END); | |
487 | goto bad; | |
488 | } | |
489 | ||
490 | /* --- Unpack the packet --- */ | |
491 | ||
492 | if (G_FROMBUF(gg, b, c) || BLEFT(b)) | |
493 | goto bad; | |
b5c45da1 | 494 | |
0617b6e7 | 495 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
de7bd20b | 496 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c)); |
0617b6e7 | 497 | })) |
de7bd20b MW |
498 | |
499 | /* --- Send out a full challenge by return --- */ | |
500 | ||
501 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_CHAL); | |
502 | h = GH_INIT(algs.h); | |
503 | HASH_STRING(h, "tripe-cookie"); | |
504 | hashge(h, c); | |
505 | sendchallenge(kx, b, c, GH_DONE(h, 0)); | |
b5c45da1 | 506 | GH_DESTROY(h); |
de7bd20b MW |
507 | st->n_kxout++; |
508 | st->sz_kxout += BLEN(b); | |
509 | p_txend(kx->p); | |
510 | ||
511 | /* --- Done --- */ | |
512 | ||
513 | G_DESTROY(gg, c); | |
514 | return (0); | |
515 | ||
516 | bad: | |
517 | if (c) G_DESTROY(gg, c); | |
518 | return (-1); | |
0617b6e7 | 519 | } |
520 | ||
de7bd20b | 521 | /* --- @respond@ --- * |
0617b6e7 | 522 | * |
523 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
de7bd20b | 524 | * @unsigned msg@ = message code for this packet |
0617b6e7 | 525 | * @buf *b@ = buffer containing the packet |
526 | * | |
de7bd20b | 527 | * Returns: Key-exchange challenge block, or null. |
0617b6e7 | 528 | * |
de7bd20b MW |
529 | * Use: Computes a response for the given challenge, entering it into |
530 | * a challenge block and so on. | |
0617b6e7 | 531 | */ |
532 | ||
de7bd20b | 533 | static kxchal *respond(keyexch *kx, unsigned msg, buf *b) |
0617b6e7 | 534 | { |
52c03a2a | 535 | ge *c = G_CREATE(gg); |
de7bd20b MW |
536 | ge *r = G_CREATE(gg); |
537 | ge *cc = G_CREATE(gg); | |
538 | const octet *hc, *ck; | |
539 | size_t x, y, z; | |
540 | mp *cv = 0; | |
0617b6e7 | 541 | kxchal *kxc; |
de7bd20b MW |
542 | ghash *h = 0; |
543 | buf bb; | |
544 | int ok; | |
0617b6e7 | 545 | |
546 | /* --- Unpack the packet --- */ | |
547 | ||
52c03a2a | 548 | if (G_FROMBUF(gg, b, c) || |
de7bd20b MW |
549 | (hc = buf_get(b, algs.hashsz)) == 0 || |
550 | (ck = buf_get(b, indexsz)) == 0) { | |
f43df819 | 551 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
0617b6e7 | 552 | goto bad; |
553 | } | |
0617b6e7 | 554 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
52c03a2a | 555 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c)); |
de7bd20b MW |
556 | trace_block(T_CRYPTO, "crypto: cookie", hc, algs.hashsz); |
557 | trace_block(T_CRYPTO, "crypto: check-value", ck, indexsz); | |
0617b6e7 | 558 | })) |
559 | ||
0617b6e7 | 560 | /* --- Discard a packet with an invalid cookie --- */ |
561 | ||
b5c45da1 | 562 | if (hc && memcmp(hc, kx->hc, algs.hashsz) != 0) { |
5ac9463b | 563 | a_warn("KX", "?PEER", kx->p, "incorrect", "cookie", A_END); |
0617b6e7 | 564 | goto bad; |
565 | } | |
566 | ||
de7bd20b MW |
567 | /* --- Recover the check value and verify it --- * |
568 | * | |
569 | * To avoid recomputation on replays, we store a hash of the `right' | |
570 | * value. The `correct' value is unique, so this is right. | |
410c8acf | 571 | * |
de7bd20b | 572 | * This will also find a challenge block and, if necessary, populate it. |
410c8acf | 573 | */ |
574 | ||
de7bd20b MW |
575 | if ((kxc = kxc_bychal(kx, c)) != 0) { |
576 | h = GH_INIT(algs.h); | |
577 | HASH_STRING(h, "tripe-check-hash"); | |
578 | GH_HASH(h, ck, indexsz); | |
579 | ok = !memcmp(kxc->ck, GH_DONE(h, 0), algs.hashsz); | |
580 | GH_DESTROY(h); | |
581 | if (!ok) goto badcheck; | |
582 | } else { | |
583 | ||
584 | /* --- Compute the reply, and check the magic --- */ | |
585 | ||
586 | G_EXP(gg, r, c, kpriv); | |
587 | cv = mpunmask(MP_NEW, ck, indexsz, | |
588 | hashcheck(kx->kpub, kx->c, c, r), algs.hashsz); | |
589 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
590 | trace(T_CRYPTO, "crypto: computed reply = %s", gestr(gg, r)); | |
591 | trace(T_CRYPTO, "crypto: recovered log = %s", mpstr(cv)); | |
592 | })) | |
593 | if (MP_CMP(cv, >, gg->r) || | |
594 | (G_EXP(gg, cc, gg->g, cv), !G_EQ(gg, c, cc))) | |
595 | goto badcheck; | |
596 | ||
597 | /* --- Fill in a new challenge block --- */ | |
e04c2d50 | 598 | |
de7bd20b | 599 | kxc = kxc_new(kx); |
52c03a2a | 600 | G_COPY(gg, kxc->c, c); |
de7bd20b | 601 | G_COPY(gg, kxc->r, r); |
0617b6e7 | 602 | |
de7bd20b MW |
603 | h = GH_INIT(algs.h); |
604 | HASH_STRING(h, "tripe-check-hash"); | |
605 | GH_HASH(h, ck, indexsz); | |
5fb10b44 | 606 | GH_DONE(h, kxc->ck); |
de7bd20b | 607 | GH_DESTROY(h); |
0617b6e7 | 608 | |
b5c45da1 | 609 | h = GH_INIT(algs.h); |
610 | HASH_STRING(h, "tripe-cookie"); | |
611 | hashge(h, kxc->c); | |
612 | GH_DONE(h, kxc->hc); | |
613 | GH_DESTROY(h); | |
614 | ||
615 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
616 | trace_block(T_CRYPTO, "crypto: computed cookie", kxc->hc, algs.hashsz); | |
617 | })) | |
0617b6e7 | 618 | |
0617b6e7 | 619 | /* --- Work out the shared key --- */ |
620 | ||
52c03a2a | 621 | G_EXP(gg, r, c, kx->alpha); |
b5c45da1 | 622 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
623 | trace(T_CRYPTO, "crypto: shared secret = %s", gestr(gg, r)); | |
624 | })) | |
0617b6e7 | 625 | |
626 | /* --- Compute the switch messages --- */ | |
627 | ||
b5c45da1 | 628 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request"); |
629 | hashge(h, kx->c); hashge(h, kxc->c); | |
630 | GH_DONE(h, kxc->hswrq_out); GH_DESTROY(h); | |
631 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm"); | |
632 | hashge(h, kx->c); hashge(h, kxc->c); | |
633 | GH_DONE(h, kxc->hswok_out); GH_DESTROY(h); | |
0617b6e7 | 634 | |
b5c45da1 | 635 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request"); |
636 | hashge(h, kxc->c); hashge(h, kx->c); | |
637 | GH_DONE(h, kxc->hswrq_in); GH_DESTROY(h); | |
638 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm"); | |
639 | hashge(h, kxc->c); hashge(h, kx->c); | |
640 | GH_DONE(h, kxc->hswok_in); GH_DESTROY(h); | |
0617b6e7 | 641 | |
642 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
0617b6e7 | 643 | trace_block(T_CRYPTO, "crypto: outbound switch request", |
b5c45da1 | 644 | kxc->hswrq_out, algs.hashsz); |
0617b6e7 | 645 | trace_block(T_CRYPTO, "crypto: outbound switch confirm", |
b5c45da1 | 646 | kxc->hswok_out, algs.hashsz); |
0617b6e7 | 647 | trace_block(T_CRYPTO, "crypto: inbound switch request", |
b5c45da1 | 648 | kxc->hswrq_in, algs.hashsz); |
0617b6e7 | 649 | trace_block(T_CRYPTO, "crypto: inbound switch confirm", |
b5c45da1 | 650 | kxc->hswok_in, algs.hashsz); |
0617b6e7 | 651 | })) |
652 | ||
653 | /* --- Create a new symmetric keyset --- */ | |
654 | ||
de7bd20b MW |
655 | buf_init(&bb, buf_o, sizeof(buf_o)); |
656 | G_TOBUF(gg, &bb, kx->c); x = BLEN(&bb); | |
657 | G_TOBUF(gg, &bb, kxc->c); y = BLEN(&bb); | |
658 | G_TOBUF(gg, &bb, r); z = BLEN(&bb); | |
659 | assert(BOK(&bb)); | |
0617b6e7 | 660 | |
de7bd20b | 661 | kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p); |
410c8acf | 662 | } |
663 | ||
de7bd20b MW |
664 | G_DESTROY(gg, c); |
665 | G_DESTROY(gg, cc); | |
666 | G_DESTROY(gg, r); | |
667 | mp_drop(cv); | |
668 | return (kxc); | |
410c8acf | 669 | |
de7bd20b MW |
670 | badcheck: |
671 | a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END); | |
672 | goto bad; | |
673 | bad: | |
674 | G_DESTROY(gg, c); | |
675 | G_DESTROY(gg, cc); | |
676 | G_DESTROY(gg, r); | |
677 | mp_drop(cv); | |
e04c2d50 | 678 | return (0); |
de7bd20b | 679 | } |
0617b6e7 | 680 | |
de7bd20b MW |
681 | /* --- @dochallenge@ --- * |
682 | * | |
683 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
684 | * @unsigned msg@ = message code for the packet | |
685 | * @buf *b@ = buffer containing the packet | |
686 | * | |
687 | * Returns: Zero if OK, nonzero if the packet was rejected. | |
688 | * | |
689 | * Use: Processes a packet containing a challenge. | |
690 | */ | |
0617b6e7 | 691 | |
de7bd20b MW |
692 | static int dochallenge(keyexch *kx, buf *b) |
693 | { | |
694 | kxchal *kxc; | |
0617b6e7 | 695 | |
de7bd20b MW |
696 | if (kx->s != KXS_CHAL) { |
697 | a_warn("KX", "?PEER", kx->p, "unexpected", "challenge", A_END); | |
698 | goto bad; | |
699 | } | |
700 | if ((kxc = respond(kx, KX_CHAL, b)) == 0) | |
701 | goto bad; | |
702 | if (BLEFT(b)) { | |
703 | a_warn("KX", "?PEER", kx->p, "invalid", "challenge", A_END); | |
704 | goto bad; | |
705 | } | |
706 | kxc_answer(kx, kxc); | |
0617b6e7 | 707 | return (0); |
708 | ||
709 | bad: | |
0617b6e7 | 710 | return (-1); |
410c8acf | 711 | } |
712 | ||
0617b6e7 | 713 | /* --- @resend@ --- * |
410c8acf | 714 | * |
715 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
410c8acf | 716 | * |
717 | * Returns: --- | |
718 | * | |
0617b6e7 | 719 | * Use: Sends the next message for a key exchange. |
410c8acf | 720 | */ |
721 | ||
0617b6e7 | 722 | static void resend(keyexch *kx) |
410c8acf | 723 | { |
0617b6e7 | 724 | kxchal *kxc; |
725 | buf bb; | |
726 | stats *st = p_stats(kx->p); | |
410c8acf | 727 | buf *b; |
728 | ||
0617b6e7 | 729 | switch (kx->s) { |
730 | case KXS_CHAL: | |
00e64b67 | 731 | T( trace(T_KEYEXCH, "keyexch: sending prechallenge to `%s'", |
732 | p_name(kx->p)); ) | |
0617b6e7 | 733 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL); |
52c03a2a | 734 | G_TOBUF(gg, b, kx->c); |
0617b6e7 | 735 | break; |
736 | case KXS_COMMIT: | |
00e64b67 | 737 | T( trace(T_KEYEXCH, "keyexch: sending switch request to `%s'", |
738 | p_name(kx->p)); ) | |
0617b6e7 | 739 | kxc = kx->r[0]; |
740 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH); | |
b5c45da1 | 741 | buf_put(b, kx->hc, algs.hashsz); |
742 | buf_put(b, kxc->hc, algs.hashsz); | |
0617b6e7 | 743 | buf_init(&bb, buf_i, sizeof(buf_i)); |
de7bd20b | 744 | G_TORAW(gg, &bb, kxc->r); |
b5c45da1 | 745 | buf_put(&bb, kxc->hswrq_out, algs.hashsz); |
0617b6e7 | 746 | buf_flip(&bb); |
7ed14135 | 747 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCH, &bb, b); |
0617b6e7 | 748 | break; |
749 | case KXS_SWITCH: | |
00e64b67 | 750 | T( trace(T_KEYEXCH, "keyexch: sending switch confirmation to `%s'", |
0617b6e7 | 751 | p_name(kx->p)); ) |
752 | kxc = kx->r[0]; | |
753 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK); | |
754 | buf_init(&bb, buf_i, sizeof(buf_i)); | |
b5c45da1 | 755 | buf_put(&bb, kxc->hswok_out, algs.hashsz); |
0617b6e7 | 756 | buf_flip(&bb); |
7ed14135 | 757 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCHOK, &bb, b); |
0617b6e7 | 758 | break; |
759 | default: | |
760 | abort(); | |
410c8acf | 761 | } |
0617b6e7 | 762 | |
763 | if (BOK(b)) { | |
764 | st->n_kxout++; | |
765 | st->sz_kxout += BLEN(b); | |
766 | p_txend(kx->p); | |
767 | } | |
768 | ||
769 | if (kx->s < KXS_SWITCH) | |
770 | settimer(kx, time(0) + T_RETRY); | |
410c8acf | 771 | } |
772 | ||
de7bd20b | 773 | /* --- @decryptrest@ --- * |
0617b6e7 | 774 | * |
775 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
de7bd20b MW |
776 | * @kxchal *kxc@ = pointer to challenge block |
777 | * @unsigned msg@ = type of incoming message | |
0617b6e7 | 778 | * @buf *b@ = encrypted remainder of the packet |
779 | * | |
de7bd20b | 780 | * Returns: Zero if OK, nonzero on some kind of error. |
0617b6e7 | 781 | * |
de7bd20b MW |
782 | * Use: Decrypts the remainder of the packet, and points @b@ at the |
783 | * recovered plaintext. | |
0617b6e7 | 784 | */ |
785 | ||
de7bd20b | 786 | static int decryptrest(keyexch *kx, kxchal *kxc, unsigned msg, buf *b) |
410c8acf | 787 | { |
0617b6e7 | 788 | buf bb; |
0617b6e7 | 789 | |
de7bd20b MW |
790 | buf_init(&bb, buf_o, sizeof(buf_o)); |
791 | if (ks_decrypt(kxc->ks, MSG_KEYEXCH | msg, b, &bb)) { | |
792 | a_warn("KX", "?PEER", kx->p, "decrypt-failed", "%s", pkname[msg], A_END); | |
793 | return (-1); | |
0617b6e7 | 794 | } |
12a26b8b | 795 | if (!BOK(&bb)) return (-1); |
de7bd20b MW |
796 | buf_init(b, BBASE(&bb), BLEN(&bb)); |
797 | return (0); | |
798 | } | |
410c8acf | 799 | |
de7bd20b MW |
800 | /* --- @checkresponse@ --- * |
801 | * | |
802 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
803 | * @unsigned msg@ = type of incoming message | |
804 | * @buf *b@ = decrypted remainder of the packet | |
805 | * | |
806 | * Returns: Zero if OK, nonzero on some kind of error. | |
807 | * | |
808 | * Use: Checks a reply or switch packet, ensuring that its response | |
809 | * is correct. | |
810 | */ | |
0617b6e7 | 811 | |
de7bd20b MW |
812 | static int checkresponse(keyexch *kx, unsigned msg, buf *b) |
813 | { | |
814 | ge *r = G_CREATE(gg); | |
0617b6e7 | 815 | |
5251b2e9 | 816 | if (G_FROMRAW(gg, b, r)) { |
de7bd20b | 817 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
0617b6e7 | 818 | goto bad; |
819 | } | |
820 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { | |
52c03a2a | 821 | trace(T_CRYPTO, "crypto: reply = %s", gestr(gg, r)); |
0617b6e7 | 822 | })) |
52c03a2a | 823 | if (!G_EQ(gg, r, kx->rx)) { |
de7bd20b | 824 | a_warn("KX", "?PEER", kx->p, "incorrect", "response", A_END); |
0617b6e7 | 825 | goto bad; |
826 | } | |
827 | ||
52c03a2a | 828 | G_DESTROY(gg, r); |
de7bd20b | 829 | return (0); |
0617b6e7 | 830 | |
831 | bad: | |
de7bd20b MW |
832 | G_DESTROY(gg, r); |
833 | return (-1); | |
410c8acf | 834 | } |
835 | ||
0617b6e7 | 836 | /* --- @commit@ --- * |
410c8acf | 837 | * |
838 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
0617b6e7 | 839 | * @kxchal *kxc@ = pointer to challenge to commit to |
410c8acf | 840 | * |
841 | * Returns: --- | |
842 | * | |
0617b6e7 | 843 | * Use: Commits to a particular challenge as being the `right' one, |
844 | * since a reply has arrived for it. | |
410c8acf | 845 | */ |
846 | ||
0617b6e7 | 847 | static void commit(keyexch *kx, kxchal *kxc) |
410c8acf | 848 | { |
0617b6e7 | 849 | unsigned i; |
410c8acf | 850 | |
0617b6e7 | 851 | for (i = 0; i < kx->nr; i++) { |
852 | if (kx->r[i] != kxc) | |
853 | kxc_destroy(kx->r[i]); | |
854 | } | |
855 | kx->r[0] = kxc; | |
856 | kx->nr = 1; | |
857 | kxc_stoptimer(kxc); | |
e04c2d50 | 858 | ksl_link(kx->ks, kxc->ks); |
410c8acf | 859 | } |
860 | ||
0617b6e7 | 861 | /* --- @doreply@ --- * |
410c8acf | 862 | * |
863 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
0617b6e7 | 864 | * @buf *b@ = buffer containing packet |
410c8acf | 865 | * |
0617b6e7 | 866 | * Returns: Zero if OK, nonzero if the packet was rejected. |
410c8acf | 867 | * |
0617b6e7 | 868 | * Use: Handles a reply packet. This doesn't handle the various |
869 | * switch packets: they're rather too different. | |
410c8acf | 870 | */ |
871 | ||
0617b6e7 | 872 | static int doreply(keyexch *kx, buf *b) |
410c8acf | 873 | { |
0617b6e7 | 874 | kxchal *kxc; |
875 | ||
876 | if (kx->s != KXS_CHAL && kx->s != KXS_COMMIT) { | |
f43df819 | 877 | a_warn("KX", "?PEER", kx->p, "unexpected", "reply", A_END); |
0617b6e7 | 878 | goto bad; |
879 | } | |
de7bd20b MW |
880 | if ((kxc = respond(kx, KX_REPLY, b)) == 0 || |
881 | decryptrest(kx, kxc, KX_REPLY, b) || | |
882 | checkresponse(kx, KX_REPLY, b)) | |
0617b6e7 | 883 | goto bad; |
884 | if (BLEFT(b)) { | |
f43df819 | 885 | a_warn("KX", "?PEER", kx->p, "invalid", "reply", A_END); |
0617b6e7 | 886 | goto bad; |
e04c2d50 | 887 | } |
0617b6e7 | 888 | if (kx->s == KXS_CHAL) { |
889 | commit(kx, kxc); | |
890 | kx->s = KXS_COMMIT; | |
891 | } | |
892 | resend(kx); | |
893 | return (0); | |
894 | ||
895 | bad: | |
896 | return (-1); | |
410c8acf | 897 | } |
898 | ||
3cdc3f3a | 899 | /* --- @kxfinish@ --- * |
900 | * | |
901 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
902 | * | |
903 | * Returns: --- | |
904 | * | |
905 | * Use: Sets everything up following a successful key exchange. | |
906 | */ | |
907 | ||
908 | static void kxfinish(keyexch *kx) | |
909 | { | |
910 | kxchal *kxc = kx->r[0]; | |
911 | ks_activate(kxc->ks); | |
912 | settimer(kx, ks_tregen(kxc->ks)); | |
913 | kx->s = KXS_SWITCH; | |
f43df819 | 914 | a_notify("KXDONE", "?PEER", kx->p, A_END); |
3cdc3f3a | 915 | p_stats(kx->p)->t_kx = time(0); |
916 | } | |
917 | ||
0617b6e7 | 918 | /* --- @doswitch@ --- * |
410c8acf | 919 | * |
0617b6e7 | 920 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
921 | * @buf *b@ = pointer to buffer containing packet | |
410c8acf | 922 | * |
0617b6e7 | 923 | * Returns: Zero if OK, nonzero if the packet was rejected. |
410c8acf | 924 | * |
0617b6e7 | 925 | * Use: Handles a reply with a switch request bolted onto it. |
410c8acf | 926 | */ |
927 | ||
0617b6e7 | 928 | static int doswitch(keyexch *kx, buf *b) |
410c8acf | 929 | { |
0617b6e7 | 930 | const octet *hc_in, *hc_out, *hswrq; |
931 | kxchal *kxc; | |
410c8acf | 932 | |
b5c45da1 | 933 | if ((hc_in = buf_get(b, algs.hashsz)) == 0 || |
934 | (hc_out = buf_get(b, algs.hashsz)) == 0) { | |
f43df819 | 935 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
0617b6e7 | 936 | goto bad; |
410c8acf | 937 | } |
de7bd20b MW |
938 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
939 | trace_block(T_CRYPTO, "crypto: challenge", hc_in, algs.hashsz); | |
940 | trace_block(T_CRYPTO, "crypto: cookie", hc_out, algs.hashsz); | |
941 | })) | |
942 | if ((kxc = kxc_byhc(kx, hc_in)) == 0 || | |
943 | memcmp(hc_out, kx->hc, algs.hashsz) != 0) { | |
944 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); | |
945 | goto bad; | |
946 | } | |
947 | if (decryptrest(kx, kxc, KX_SWITCH, b) || | |
948 | checkresponse(kx, KX_SWITCH, b)) | |
0617b6e7 | 949 | goto bad; |
b5c45da1 | 950 | if ((hswrq = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) { |
5ac9463b | 951 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
0617b6e7 | 952 | goto bad; |
953 | } | |
954 | IF_TRACING(T_KEYEXCH, { | |
b5c45da1 | 955 | trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, algs.hashsz); |
0617b6e7 | 956 | }) |
b5c45da1 | 957 | if (memcmp(hswrq, kxc->hswrq_in, algs.hashsz) != 0) { |
f43df819 | 958 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); |
0617b6e7 | 959 | goto bad; |
960 | } | |
de7bd20b MW |
961 | if (kx->s == KXS_CHAL) |
962 | commit(kx, kxc); | |
963 | if (kx->s < KXS_SWITCH) | |
964 | kxfinish(kx); | |
0617b6e7 | 965 | resend(kx); |
966 | return (0); | |
967 | ||
968 | bad: | |
969 | return (-1); | |
410c8acf | 970 | } |
971 | ||
0617b6e7 | 972 | /* --- @doswitchok@ --- * |
973 | * | |
974 | * Arguments: @keyexch *kx@ = pointer to key exchange block | |
975 | * @buf *b@ = pointer to buffer containing packet | |
976 | * | |
977 | * Returns: Zero if OK, nonzero if the packet was rejected. | |
978 | * | |
979 | * Use: Handles a reply with a switch request bolted onto it. | |
980 | */ | |
981 | ||
982 | static int doswitchok(keyexch *kx, buf *b) | |
410c8acf | 983 | { |
0617b6e7 | 984 | const octet *hswok; |
985 | kxchal *kxc; | |
986 | buf bb; | |
410c8acf | 987 | |
0617b6e7 | 988 | if (kx->s < KXS_COMMIT) { |
f43df819 | 989 | a_warn("KX", "?PEER", kx->p, "unexpected", "switch-ok", A_END); |
0617b6e7 | 990 | goto bad; |
410c8acf | 991 | } |
0617b6e7 | 992 | kxc = kx->r[0]; |
993 | buf_init(&bb, buf_o, sizeof(buf_o)); | |
de7bd20b | 994 | if (decryptrest(kx, kxc, KX_SWITCHOK, b)) |
0617b6e7 | 995 | goto bad; |
b5c45da1 | 996 | if ((hswok = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) { |
5ac9463b | 997 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-ok", A_END); |
0617b6e7 | 998 | goto bad; |
999 | } | |
1000 | IF_TRACING(T_KEYEXCH, { | |
b5c45da1 | 1001 | trace_block(T_CRYPTO, "crypto: switch confirmation hash", |
1002 | hswok, algs.hashsz); | |
0617b6e7 | 1003 | }) |
b5c45da1 | 1004 | if (memcmp(hswok, kxc->hswok_in, algs.hashsz) != 0) { |
f43df819 | 1005 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-ok", A_END); |
0617b6e7 | 1006 | goto bad; |
1007 | } | |
3cdc3f3a | 1008 | if (kx->s < KXS_SWITCH) |
1009 | kxfinish(kx); | |
0617b6e7 | 1010 | return (0); |
1011 | ||
1012 | bad: | |
e04c2d50 | 1013 | return (-1); |
0617b6e7 | 1014 | } |
1015 | ||
1016 | /*----- Main code ---------------------------------------------------------*/ | |
1017 | ||
1018 | /* --- @stop@ --- * | |
1019 | * | |
1020 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1021 | * | |
1022 | * Returns: --- | |
1023 | * | |
1024 | * Use: Stops a key exchange dead in its tracks. Throws away all of | |
1025 | * the context information. The context is left in an | |
1026 | * inconsistent state. The only functions which understand this | |
1027 | * state are @kx_free@ and @kx_init@ (which cause it internally | |
1028 | * it), and @start@ (which expects it to be the prevailing | |
1029 | * state). | |
1030 | */ | |
1031 | ||
1032 | static void stop(keyexch *kx) | |
1033 | { | |
1034 | unsigned i; | |
1035 | ||
00e64b67 | 1036 | if (kx->f & KXF_DEAD) |
1037 | return; | |
1038 | ||
0617b6e7 | 1039 | if (kx->f & KXF_TIMER) |
1040 | sel_rmtimer(&kx->t); | |
1041 | for (i = 0; i < kx->nr; i++) | |
1042 | kxc_destroy(kx->r[i]); | |
1043 | mp_drop(kx->alpha); | |
52c03a2a | 1044 | G_DESTROY(gg, kx->c); |
1045 | G_DESTROY(gg, kx->rx); | |
00e64b67 | 1046 | kx->t_valid = 0; |
1047 | kx->f |= KXF_DEAD; | |
1048 | kx->f &= ~KXF_TIMER; | |
0617b6e7 | 1049 | } |
1050 | ||
1051 | /* --- @start@ --- * | |
1052 | * | |
1053 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1054 | * @time_t now@ = the current time | |
1055 | * | |
1056 | * Returns: --- | |
1057 | * | |
1058 | * Use: Starts a new key exchange with the peer. The context must be | |
1059 | * in the bizarre state left by @stop@ or @kx_init@. | |
1060 | */ | |
1061 | ||
1062 | static void start(keyexch *kx, time_t now) | |
1063 | { | |
b5c45da1 | 1064 | ghash *h; |
0617b6e7 | 1065 | |
00e64b67 | 1066 | assert(kx->f & KXF_DEAD); |
1067 | ||
010e6f63 | 1068 | kx->f &= ~(KXF_DEAD | KXF_CORK); |
0617b6e7 | 1069 | kx->nr = 0; |
52c03a2a | 1070 | kx->alpha = mprand_range(MP_NEW, gg->r, &rand_global, 0); |
1071 | kx->c = G_CREATE(gg); G_EXP(gg, kx->c, gg->g, kx->alpha); | |
1072 | kx->rx = G_CREATE(gg); G_EXP(gg, kx->rx, kx->kpub, kx->alpha); | |
0617b6e7 | 1073 | kx->s = KXS_CHAL; |
1074 | kx->t_valid = now + T_VALID; | |
1075 | ||
b5c45da1 | 1076 | h = GH_INIT(algs.h); |
1077 | HASH_STRING(h, "tripe-cookie"); | |
1078 | hashge(h, kx->c); | |
1079 | GH_DONE(h, kx->hc); | |
1080 | GH_DESTROY(h); | |
0617b6e7 | 1081 | |
1082 | IF_TRACING(T_KEYEXCH, { | |
1083 | trace(T_KEYEXCH, "keyexch: creating new challenge"); | |
1084 | IF_TRACING(T_CRYPTO, { | |
1085 | trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha)); | |
52c03a2a | 1086 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, kx->c)); |
1087 | trace(T_CRYPTO, "crypto: expected response = %s", gestr(gg, kx->rx)); | |
b5c45da1 | 1088 | trace_block(T_CRYPTO, "crypto: challenge cookie", kx->hc, algs.hashsz); |
0617b6e7 | 1089 | }) |
1090 | }) | |
410c8acf | 1091 | } |
1092 | ||
00e64b67 | 1093 | /* --- @checkpub@ --- * |
1094 | * | |
1095 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1096 | * | |
1097 | * Returns: Zero if OK, nonzero if the peer's public key has expired. | |
1098 | * | |
1099 | * Use: Deactivates the key-exchange until the peer acquires a new | |
1100 | * public key. | |
1101 | */ | |
1102 | ||
1103 | static int checkpub(keyexch *kx) | |
1104 | { | |
1105 | time_t now; | |
1106 | if (kx->f & KXF_DEAD) | |
1107 | return (-1); | |
1108 | now = time(0); | |
1109 | if (KEY_EXPIRED(now, kx->texp_kpub)) { | |
1110 | stop(kx); | |
f43df819 | 1111 | a_warn("KX", "?PEER", kx->p, "public-key-expired", A_END); |
52c03a2a | 1112 | G_COPY(gg, kx->kpub, gg->i); |
00e64b67 | 1113 | kx->f &= ~KXF_PUBKEY; |
1114 | return (-1); | |
1115 | } | |
1116 | return (0); | |
1117 | } | |
1118 | ||
0617b6e7 | 1119 | /* --- @kx_start@ --- * |
410c8acf | 1120 | * |
1121 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
de014da6 | 1122 | * @int forcep@ = nonzero to ignore the quiet timer |
410c8acf | 1123 | * |
1124 | * Returns: --- | |
1125 | * | |
0617b6e7 | 1126 | * Use: Stimulates a key exchange. If a key exchage is in progress, |
1127 | * a new challenge is sent (unless the quiet timer forbids | |
1128 | * this); if no exchange is in progress, one is commenced. | |
410c8acf | 1129 | */ |
1130 | ||
de014da6 | 1131 | void kx_start(keyexch *kx, int forcep) |
410c8acf | 1132 | { |
1133 | time_t now = time(0); | |
410c8acf | 1134 | |
00e64b67 | 1135 | if (checkpub(kx)) |
1136 | return; | |
de014da6 | 1137 | if (forcep || !VALIDP(kx, now)) { |
0617b6e7 | 1138 | stop(kx); |
1139 | start(kx, now); | |
f43df819 | 1140 | a_notify("KXSTART", "?PEER", kx->p, A_END); |
410c8acf | 1141 | } |
0617b6e7 | 1142 | resend(kx); |
1143 | } | |
1144 | ||
1145 | /* --- @kx_message@ --- * | |
1146 | * | |
1147 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1148 | * @unsigned msg@ = the message code | |
1149 | * @buf *b@ = pointer to buffer containing the packet | |
1150 | * | |
1151 | * Returns: --- | |
1152 | * | |
1153 | * Use: Reads a packet containing key exchange messages and handles | |
1154 | * it. | |
1155 | */ | |
1156 | ||
1157 | void kx_message(keyexch *kx, unsigned msg, buf *b) | |
1158 | { | |
1159 | time_t now = time(0); | |
1160 | stats *st = p_stats(kx->p); | |
1161 | size_t sz = BSZ(b); | |
1162 | int rc; | |
1163 | ||
010e6f63 MW |
1164 | if (kx->f & KXF_CORK) { |
1165 | start(kx, now); | |
1166 | settimer(kx, now + T_RETRY); | |
1167 | a_notify("KXSTART", A_END); | |
1168 | } | |
1169 | ||
00e64b67 | 1170 | if (checkpub(kx)) |
1171 | return; | |
1172 | ||
3cdc3f3a | 1173 | if (!VALIDP(kx, now)) { |
0617b6e7 | 1174 | stop(kx); |
1175 | start(kx, now); | |
410c8acf | 1176 | } |
0617b6e7 | 1177 | T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'", |
1178 | msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); ) | |
1179 | ||
1180 | switch (msg) { | |
1181 | case KX_PRECHAL: | |
de7bd20b MW |
1182 | rc = doprechallenge(kx, b); |
1183 | break; | |
0617b6e7 | 1184 | case KX_CHAL: |
de7bd20b | 1185 | rc = dochallenge(kx, b); |
0617b6e7 | 1186 | break; |
1187 | case KX_REPLY: | |
1188 | rc = doreply(kx, b); | |
1189 | break; | |
1190 | case KX_SWITCH: | |
1191 | rc = doswitch(kx, b); | |
1192 | break; | |
1193 | case KX_SWITCHOK: | |
1194 | rc = doswitchok(kx, b); | |
1195 | break; | |
1196 | default: | |
f43df819 | 1197 | a_warn("KX", "?PEER", kx->p, "unknown-message", "0x%02x", msg, A_END); |
0617b6e7 | 1198 | rc = -1; |
1199 | break; | |
410c8acf | 1200 | } |
410c8acf | 1201 | |
0617b6e7 | 1202 | if (rc) |
1203 | st->n_reject++; | |
1204 | else { | |
1205 | st->n_kxin++; | |
1206 | st->sz_kxin += sz; | |
1207 | } | |
410c8acf | 1208 | } |
1209 | ||
1210 | /* --- @kx_free@ --- * | |
1211 | * | |
1212 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1213 | * | |
1214 | * Returns: --- | |
1215 | * | |
1216 | * Use: Frees everything in a key exchange context. | |
1217 | */ | |
1218 | ||
1219 | void kx_free(keyexch *kx) | |
1220 | { | |
0617b6e7 | 1221 | stop(kx); |
52c03a2a | 1222 | G_DESTROY(gg, kx->kpub); |
410c8acf | 1223 | } |
1224 | ||
1225 | /* --- @kx_newkeys@ --- * | |
1226 | * | |
1227 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1228 | * | |
1229 | * Returns: --- | |
1230 | * | |
1231 | * Use: Informs the key exchange module that its keys may have | |
1232 | * changed. If fetching the new keys fails, the peer will be | |
1233 | * destroyed, we log messages and struggle along with the old | |
1234 | * keys. | |
1235 | */ | |
1236 | ||
1237 | void kx_newkeys(keyexch *kx) | |
1238 | { | |
48b84569 | 1239 | if (km_getpubkey(p_tag(kx->p), kx->kpub, &kx->texp_kpub)) |
410c8acf | 1240 | return; |
00e64b67 | 1241 | kx->f |= KXF_PUBKEY; |
1242 | if ((kx->f & KXF_DEAD) || kx->s != KXS_SWITCH) { | |
410c8acf | 1243 | T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'", |
1244 | p_name(kx->p)); ) | |
00e64b67 | 1245 | stop(kx); |
1246 | start(kx, time(0)); | |
1247 | resend(kx); | |
410c8acf | 1248 | } |
1249 | } | |
1250 | ||
1251 | /* --- @kx_init@ --- * | |
1252 | * | |
1253 | * Arguments: @keyexch *kx@ = pointer to key exchange context | |
1254 | * @peer *p@ = pointer to peer context | |
1255 | * @keyset **ks@ = pointer to keyset list | |
010e6f63 | 1256 | * @unsigned f@ = various useful flags |
410c8acf | 1257 | * |
1258 | * Returns: Zero if OK, nonzero if it failed. | |
1259 | * | |
1260 | * Use: Initializes a key exchange module. The module currently | |
1261 | * contains no keys, and will attempt to initiate a key | |
1262 | * exchange. | |
1263 | */ | |
1264 | ||
010e6f63 | 1265 | int kx_init(keyexch *kx, peer *p, keyset **ks, unsigned f) |
410c8acf | 1266 | { |
1267 | kx->ks = ks; | |
1268 | kx->p = p; | |
52c03a2a | 1269 | kx->kpub = G_CREATE(gg); |
48b84569 | 1270 | if (km_getpubkey(p_tag(p), kx->kpub, &kx->texp_kpub)) { |
52c03a2a | 1271 | G_DESTROY(gg, kx->kpub); |
410c8acf | 1272 | return (-1); |
52c03a2a | 1273 | } |
010e6f63 MW |
1274 | kx->f = KXF_DEAD | KXF_PUBKEY | f; |
1275 | if (!(kx->f & KXF_CORK)) { | |
1276 | start(kx, time(0)); | |
1277 | resend(kx); | |
1278 | /* Don't notify here: the ADD message hasn't gone out yet. */ | |
1279 | } | |
410c8acf | 1280 | return (0); |
1281 | } | |
1282 | ||
1283 | /*----- That's all, folks -------------------------------------------------*/ |