3 * Key exchange protocol
5 * (c) 2001 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Trivial IP Encryption (TrIPE).
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.
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.
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.
27 /*----- Header files ------------------------------------------------------*/
31 /*----- Brief protocol overview -------------------------------------------*
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.
40 * At the beginning of the session, Alice chooses
42 * %$\rho_A \inr \{0, \ldots q - 1\}$%
46 * %$r_A = g^{\rho_A}$% Alice's challenge
47 * %$c_A = H(\cookie{cookie}, r_A)$% Alice's cookie
48 * %$v_A = \rho_A \xor H(\cookie{expected-reply}, a, r_A, r_B, b^{\rho_A})$%
49 * Alice's challenge check value
50 * %$r_B^\alpha = a^{\rho_B}$% Alice's reply
51 * %$K = r_B^{\rho_A} = r_B^{\rho_A} = g^{\rho_A\rho_B}$%
52 * Alice and Bob's shared secret key
53 * %$w_A = H(\cookie{switch-request}, c_A, c_B)$%
54 * Alice's switch request value
55 * %$u_A = H(\cookie{switch-confirm}, c_A, c_B)$%
56 * Alice's switch confirm value
58 * The messages are then:
60 * %$\cookie{kx-pre-challenge}, r_A$%
61 * Initial greeting. In state @KXS_CHAL@.
63 * %$\cookie{kx-challenge}, r_A, c_B, v_A$%
64 * Here's a full challenge for you to answer.
66 * %$\cookie{kx-reply}, r_A, c_B, v_A, E_K(r_B^\alpha))$%
67 * Challenge accpeted: here's the answer. Commit to my challenge. Move
70 * %$\cookie{kx-switch-rq}, c_A, c_B, E_K(r_B^\alpha, w_A))$%
71 * Reply received: here's my reply. Committed; send data; move to
74 * %$\cookie{kx-switch-ok}, E_K(u_A))$%
75 * Switch received. Committed; send data; move to @KXS_SWITCH@.
78 /*----- Static tables -----------------------------------------------------*/
80 static const char *const pkname[] = {
81 "pre-challenge", "challenge", "reply", "switch-rq", "switch-ok"
84 /*----- Various utilities -------------------------------------------------*/
88 * Arguments: @const keyexch *kx@ = key exchange state
89 * @time_t now@ = current time in seconds
91 * Returns: Whether the challenge in the key-exchange state is still
92 * valid or should be regenerated.
95 #define VALIDP(kx, now) ((now) < (kx)->t_valid)
99 * Arguments: @ghash *h@ = pointer to hash context
100 * @ge *x@ = pointer to group element
104 * Use: Adds the hash of a group element to the context. Corrupts
108 static void hashge(ghash *h, ge *x)
111 buf_init(&b, buf_t, sizeof(buf_t));
114 GH_HASH(h, BBASE(&b), BLEN(&b));
117 /* --- @mpmask@ --- *
119 * Arguments: @buf *b@ = output buffer
120 * @mp *x@ = the plaintext integer
121 * @size_t n@ = the expected size of the plaintext
122 * @const octet *k@ = pointer to key material
123 * @size_t ksz@ = size of the key
125 * Returns: Pointer to the output.
127 * Use: Masks a multiprecision integer: returns %$x \xor H(k)$%, so
128 * it's a random oracle thing rather than an encryption thing.
131 static octet *mpmask(buf *b, mp *x, size_t n, const octet *k, size_t ksz)
136 if ((p = buf_get(b, n)) == 0)
138 mgf = GC_INIT(algs.mgf, k, ksz);
139 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
140 trace(T_CRYPTO, "masking index = %s", mpstr(x));
141 trace_block(T_CRYPTO, "masking key", k, ksz);
143 mp_storeb(x, buf_t, n);
144 GC_ENCRYPT(mgf, buf_t, p, n);
145 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
146 trace_block(T_CRYPTO, "index plaintext", buf_t, n);
147 trace_block(T_CRYPTO, "masked ciphertext", p, n);
153 /* --- @mpunmask@ --- *
155 * Arguments: @mp *d@ = the output integer
156 * @const octet *p@ = pointer to the ciphertext
157 * @size_t n@ = the size of the ciphertext
158 * @const octet *k@ = pointer to key material
159 * @size_t ksz@ = size of the key
161 * Returns: The decrypted integer, or null.
163 * Use: Unmasks a multiprecision integer.
166 static mp *mpunmask(mp *d, const octet *p, size_t n,
167 const octet *k, size_t ksz)
171 mgf = GC_INIT(algs.mgf, k, ksz);
172 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
173 trace_block(T_CRYPTO, "unmasking key", k, ksz);
174 trace_block(T_CRYPTO, "masked ciphertext", p, n);
176 GC_DECRYPT(mgf, p, buf_t, n);
177 d = mp_loadb(d, buf_t, n);
178 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
179 trace_block(T_CRYPTO, "index plaintext", buf_t, n);
180 trace(T_CRYPTO, "unmasked index = %s", mpstr(d));
186 /* --- @hashcheck@ --- *
188 * Arguments: @ge *kpub@ = sender's public key
189 * @ge *cc@ = receiver's challenge
190 * @ge *c@ = sender's challenge
191 * @ge *y@ = reply to sender's challenge
193 * Returns: Pointer to the hash value (in @buf_t@)
195 * Use: Computes the check-value hash, used to mask or unmask
196 * indices to prove the validity of challenges. This computes
197 * the masking key used in challenge check values. This is
198 * really the heart of the whole thing, since it ensures that
199 * the index can be recovered from the history of hashing
200 * queries, which gives us (a) a proof that the authentication
201 * process is zero-knowledge, and (b) a proof that the whole
202 * key-exchange is deniable.
205 static const octet *hashcheck(ge *kpub, ge *cc, ge *c, ge *y)
207 ghash *h = GH_INIT(algs.h);
209 HASH_STRING(h, "tripe-expected-reply");
215 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
216 trace(T_CRYPTO, "computing challenge check hash");
217 trace(T_CRYPTO, "public key = %s", gestr(gg, kpub));
218 trace(T_CRYPTO, "receiver challenge = %s", gestr(gg, cc));
219 trace(T_CRYPTO, "sender challenge = %s", gestr(gg, c));
220 trace(T_CRYPTO, "sender reply = %s", gestr(gg, y));
221 trace_block(T_CRYPTO, "hash output", buf_t, algs.hashsz);
227 /* --- @sendchallenge@ --- *
229 * Arguments: @keyexch *kx@ = pointer to key exchange block
230 * @buf *b@ = output buffer for challenge
231 * @ge *c@ = peer's actual challenge
232 * @const octet *hc@ = peer's challenge cookie
236 * Use: Writes a full challenge to the message buffer.
239 static void sendchallenge(keyexch *kx, buf *b, ge *c, const octet *hc)
241 G_TOBUF(gg, b, kx->c);
242 buf_put(b, hc, algs.hashsz);
243 mpmask(b, kx->alpha, indexsz,
244 hashcheck(kpub, c, kx->c, kx->rx), algs.hashsz);
249 * Arguments: @struct timeval *tv@ = the current time
250 * @void *v@ = pointer to key exchange context
254 * Use: Acts when the key exchange timer goes off.
257 static void timer(struct timeval *tv, void *v)
261 T( trace(T_KEYEXCH, "keyexch: timer has popped"); )
265 /* --- @settimer@ --- *
267 * Arguments: @keyexch *kx@ = pointer to key exchange context
268 * @time_t t@ = when to set the timer for
272 * Use: Sets the timer for the next key exchange attempt.
275 static void settimer(keyexch *kx, time_t t)
278 if (kx->f & KXF_TIMER)
282 sel_addtimer(&sel, &kx->t, &tv, timer, kx);
286 /*----- Challenge management ----------------------------------------------*/
288 /* --- Notes on challenge management --- *
290 * We may get multiple different replies to our key exchange; some will be
291 * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges
292 * received will be added to the table and given a full response. After
293 * @KX_THRESH@ distinct challenges are received, we return only a `cookie':
294 * our existing challenge, followed by a hash of the sender's challenge. We
295 * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All
296 * properly-formed cookies are assigned a table slot: if none is spare, a
297 * used slot is randomly selected and destroyed. A cookie always receives a
301 /* --- @kxc_destroy@ --- *
303 * Arguments: @kxchal *kxc@ = pointer to the challenge block
307 * Use: Disposes of a challenge block.
310 static void kxc_destroy(kxchal *kxc)
312 if (kxc->f & KXF_TIMER)
313 sel_rmtimer(&kxc->t);
314 G_DESTROY(gg, kxc->c);
315 G_DESTROY(gg, kxc->r);
320 /* --- @kxc_stoptimer@ --- *
322 * Arguments: @kxchal *kxc@ = pointer to the challenge block
326 * Use: Stops the challenge's retry timer from sending messages.
327 * Useful when the state machine is in the endgame of the
331 static void kxc_stoptimer(kxchal *kxc)
333 if (kxc->f & KXF_TIMER)
334 sel_rmtimer(&kxc->t);
335 kxc->f &= ~KXF_TIMER;
338 /* --- @kxc_new@ --- *
340 * Arguments: @keyexch *kx@ = pointer to key exchange block
342 * Returns: A pointer to the challenge block.
344 * Use: Returns a pointer to a new challenge block to fill in.
347 static kxchal *kxc_new(keyexch *kx)
352 /* --- If we're over reply threshold, discard one at random --- */
354 if (kx->nr < KX_NCHAL)
357 i = rand_global.ops->range(&rand_global, KX_NCHAL);
358 kxc_destroy(kx->r[i]);
361 /* --- Fill in the new structure --- */
363 kxc = CREATE(kxchal);
364 kxc->c = G_CREATE(gg);
365 kxc->r = G_CREATE(gg);
373 /* --- @kxc_bychal@ --- *
375 * Arguments: @keyexch *kx@ = pointer to key exchange block
376 * @ge *c@ = challenge from remote host
378 * Returns: Pointer to the challenge block, or null.
380 * Use: Finds a challenge block, given its challenge.
383 static kxchal *kxc_bychal(keyexch *kx, ge *c)
387 for (i = 0; i < kx->nr; i++) {
388 if (G_EQ(gg, c, kx->r[i]->c))
394 /* --- @kxc_byhc@ --- *
396 * Arguments: @keyexch *kx@ = pointer to key exchange block
397 * @const octet *hc@ = challenge hash from remote host
399 * Returns: Pointer to the challenge block, or null.
401 * Use: Finds a challenge block, given a hash of its challenge.
404 static kxchal *kxc_byhc(keyexch *kx, const octet *hc)
408 for (i = 0; i < kx->nr; i++) {
409 if (memcmp(hc, kx->r[i]->hc, algs.hashsz) == 0)
415 /* --- @kxc_answer@ --- *
417 * Arguments: @keyexch *kx@ = pointer to key exchange block
418 * @kxchal *kxc@ = pointer to challenge block
422 * Use: Sends a reply to the remote host, according to the data in
423 * this challenge block.
426 static void kxc_answer(keyexch *kx, kxchal *kxc);
428 static void kxc_timer(struct timeval *tv, void *v)
431 kxc->f &= ~KXF_TIMER;
432 kxc_answer(kxc->kx, kxc);
435 static void kxc_answer(keyexch *kx, kxchal *kxc)
437 stats *st = p_stats(kx->p);
438 buf *b = p_txstart(kx->p, MSG_KEYEXCH | KX_REPLY);
442 /* --- Build the reply packet --- */
444 T( trace(T_KEYEXCH, "keyexch: sending reply to `%s'", p_name(kx->p)); )
445 sendchallenge(kx, b, kxc->c, kxc->hc);
446 buf_init(&bb, buf_i, sizeof(buf_i));
447 G_TORAW(gg, &bb, kxc->r);
449 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_REPLY, &bb, b);
451 /* --- Update the statistics --- */
455 st->sz_kxout += BLEN(b);
459 /* --- Schedule another resend --- */
461 if (kxc->f & KXF_TIMER)
462 sel_rmtimer(&kxc->t);
463 gettimeofday(&tv, 0);
464 tv.tv_sec += T_RETRY;
465 sel_addtimer(&sel, &kxc->t, &tv, kxc_timer, kxc);
469 /*----- Individual message handlers ---------------------------------------*/
471 /* --- @doprechallenge@ --- *
473 * Arguments: @keyexch *kx@ = pointer to key exchange block
474 * @buf *b@ = buffer containing the packet
476 * Returns: Zero if OK, nonzero of the packet was rejected.
478 * Use: Processes a pre-challenge message.
481 static int doprechallenge(keyexch *kx, buf *b)
483 stats *st = p_stats(kx->p);
484 ge *c = G_CREATE(gg);
487 /* --- Ensure that we're in a sensible state --- */
489 if (kx->s != KXS_CHAL) {
490 a_warn("KX", "?PEER", kx->p, "unexpected", "pre-challenge", A_END);
494 /* --- Unpack the packet --- */
496 if (G_FROMBUF(gg, b, c) || BLEFT(b))
499 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
500 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c));
503 /* --- Send out a full challenge by return --- */
505 b = p_txstart(kx->p, MSG_KEYEXCH | KX_CHAL);
507 HASH_STRING(h, "tripe-cookie");
509 sendchallenge(kx, b, c, GH_DONE(h, 0));
512 st->sz_kxout += BLEN(b);
521 if (c) G_DESTROY(gg, c);
525 /* --- @respond@ --- *
527 * Arguments: @keyexch *kx@ = pointer to key exchange block
528 * @unsigned msg@ = message code for this packet
529 * @buf *b@ = buffer containing the packet
531 * Returns: Key-exchange challenge block, or null.
533 * Use: Computes a response for the given challenge, entering it into
534 * a challenge block and so on.
537 static kxchal *respond(keyexch *kx, unsigned msg, buf *b)
539 ge *c = G_CREATE(gg);
540 ge *r = G_CREATE(gg);
541 ge *cc = G_CREATE(gg);
542 const octet *hc, *ck;
550 /* --- Unpack the packet --- */
552 if (G_FROMBUF(gg, b, c) ||
553 (hc = buf_get(b, algs.hashsz)) == 0 ||
554 (ck = buf_get(b, indexsz)) == 0) {
555 a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END);
558 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
559 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c));
560 trace_block(T_CRYPTO, "crypto: cookie", hc, algs.hashsz);
561 trace_block(T_CRYPTO, "crypto: check-value", ck, indexsz);
564 /* --- Discard a packet with an invalid cookie --- */
566 if (hc && memcmp(hc, kx->hc, algs.hashsz) != 0) {
567 a_warn("KX", "?PEER", kx->p, "incorrect", "cookie", A_END);
571 /* --- Recover the check value and verify it --- *
573 * To avoid recomputation on replays, we store a hash of the `right'
574 * value. The `correct' value is unique, so this is right.
576 * This will also find a challenge block and, if necessary, populate it.
579 if ((kxc = kxc_bychal(kx, c)) != 0) {
581 HASH_STRING(h, "tripe-check-hash");
582 GH_HASH(h, ck, indexsz);
583 ok = !memcmp(kxc->ck, GH_DONE(h, 0), algs.hashsz);
585 if (!ok) goto badcheck;
588 /* --- Compute the reply, and check the magic --- */
590 G_EXP(gg, r, c, kpriv);
591 cv = mpunmask(MP_NEW, ck, indexsz,
592 hashcheck(kx->kpub, kx->c, c, r), algs.hashsz);
593 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
594 trace(T_CRYPTO, "crypto: computed reply = %s", gestr(gg, r));
595 trace(T_CRYPTO, "crypto: recovered log = %s", mpstr(cv));
597 if (MP_CMP(cv, >, gg->r) ||
598 (G_EXP(gg, cc, gg->g, cv), !G_EQ(gg, c, cc)))
601 /* --- Fill in a new challenge block --- */
604 G_COPY(gg, kxc->c, c);
605 G_COPY(gg, kxc->r, r);
608 HASH_STRING(h, "tripe-check-hash");
609 GH_HASH(h, ck, indexsz);
614 HASH_STRING(h, "tripe-cookie");
619 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
620 trace_block(T_CRYPTO, "crypto: computed cookie", kxc->hc, algs.hashsz);
623 /* --- Work out the shared key --- */
625 G_EXP(gg, r, c, kx->alpha);
626 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
627 trace(T_CRYPTO, "crypto: shared secret = %s", gestr(gg, r));
630 /* --- Compute the switch messages --- */
632 h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request");
633 hashge(h, kx->c); hashge(h, kxc->c);
634 GH_DONE(h, kxc->hswrq_out); GH_DESTROY(h);
635 h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm");
636 hashge(h, kx->c); hashge(h, kxc->c);
637 GH_DONE(h, kxc->hswok_out); GH_DESTROY(h);
639 h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request");
640 hashge(h, kxc->c); hashge(h, kx->c);
641 GH_DONE(h, kxc->hswrq_in); GH_DESTROY(h);
642 h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm");
643 hashge(h, kxc->c); hashge(h, kx->c);
644 GH_DONE(h, kxc->hswok_in); GH_DESTROY(h);
646 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
647 trace_block(T_CRYPTO, "crypto: outbound switch request",
648 kxc->hswrq_out, algs.hashsz);
649 trace_block(T_CRYPTO, "crypto: outbound switch confirm",
650 kxc->hswok_out, algs.hashsz);
651 trace_block(T_CRYPTO, "crypto: inbound switch request",
652 kxc->hswrq_in, algs.hashsz);
653 trace_block(T_CRYPTO, "crypto: inbound switch confirm",
654 kxc->hswok_in, algs.hashsz);
657 /* --- Create a new symmetric keyset --- */
659 buf_init(&bb, buf_o, sizeof(buf_o));
660 G_TOBUF(gg, &bb, kx->c); x = BLEN(&bb);
661 G_TOBUF(gg, &bb, kxc->c); y = BLEN(&bb);
662 G_TOBUF(gg, &bb, r); z = BLEN(&bb);
665 kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p);
675 a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END);
685 /* --- @dochallenge@ --- *
687 * Arguments: @keyexch *kx@ = pointer to key exchange block
688 * @unsigned msg@ = message code for the packet
689 * @buf *b@ = buffer containing the packet
691 * Returns: Zero if OK, nonzero if the packet was rejected.
693 * Use: Processes a packet containing a challenge.
696 static int dochallenge(keyexch *kx, buf *b)
700 if (kx->s != KXS_CHAL) {
701 a_warn("KX", "?PEER", kx->p, "unexpected", "challenge", A_END);
704 if ((kxc = respond(kx, KX_CHAL, b)) == 0)
707 a_warn("KX", "?PEER", kx->p, "invalid", "challenge", A_END);
717 /* --- @resend@ --- *
719 * Arguments: @keyexch *kx@ = pointer to key exchange context
723 * Use: Sends the next message for a key exchange.
726 static void resend(keyexch *kx)
730 stats *st = p_stats(kx->p);
735 T( trace(T_KEYEXCH, "keyexch: sending prechallenge to `%s'",
737 b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL);
738 G_TOBUF(gg, b, kx->c);
741 T( trace(T_KEYEXCH, "keyexch: sending switch request to `%s'",
744 b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH);
745 buf_put(b, kx->hc, algs.hashsz);
746 buf_put(b, kxc->hc, algs.hashsz);
747 buf_init(&bb, buf_i, sizeof(buf_i));
748 G_TORAW(gg, &bb, kxc->r);
749 buf_put(&bb, kxc->hswrq_out, algs.hashsz);
751 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCH, &bb, b);
754 T( trace(T_KEYEXCH, "keyexch: sending switch confirmation to `%s'",
757 b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK);
758 buf_init(&bb, buf_i, sizeof(buf_i));
759 buf_put(&bb, kxc->hswok_out, algs.hashsz);
761 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCHOK, &bb, b);
769 st->sz_kxout += BLEN(b);
773 if (kx->s < KXS_SWITCH)
774 settimer(kx, time(0) + T_RETRY);
777 /* --- @decryptrest@ --- *
779 * Arguments: @keyexch *kx@ = pointer to key exchange context
780 * @kxchal *kxc@ = pointer to challenge block
781 * @unsigned msg@ = type of incoming message
782 * @buf *b@ = encrypted remainder of the packet
784 * Returns: Zero if OK, nonzero on some kind of error.
786 * Use: Decrypts the remainder of the packet, and points @b@ at the
787 * recovered plaintext.
790 static int decryptrest(keyexch *kx, kxchal *kxc, unsigned msg, buf *b)
794 buf_init(&bb, buf_o, sizeof(buf_o));
795 if (ks_decrypt(kxc->ks, MSG_KEYEXCH | msg, b, &bb)) {
796 a_warn("KX", "?PEER", kx->p, "decrypt-failed", "%s", pkname[msg], A_END);
799 if (!BOK(&bb)) return (-1);
800 buf_init(b, BBASE(&bb), BLEN(&bb));
804 /* --- @checkresponse@ --- *
806 * Arguments: @keyexch *kx@ = pointer to key exchange context
807 * @unsigned msg@ = type of incoming message
808 * @buf *b@ = decrypted remainder of the packet
810 * Returns: Zero if OK, nonzero on some kind of error.
812 * Use: Checks a reply or switch packet, ensuring that its response
816 static int checkresponse(keyexch *kx, unsigned msg, buf *b)
818 ge *r = G_CREATE(gg);
820 if (G_FROMRAW(gg, b, r)) {
821 a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END);
824 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
825 trace(T_CRYPTO, "crypto: reply = %s", gestr(gg, r));
827 if (!G_EQ(gg, r, kx->rx)) {
828 a_warn("KX", "?PEER", kx->p, "incorrect", "response", A_END);
840 /* --- @commit@ --- *
842 * Arguments: @keyexch *kx@ = pointer to key exchange context
843 * @kxchal *kxc@ = pointer to challenge to commit to
847 * Use: Commits to a particular challenge as being the `right' one,
848 * since a reply has arrived for it.
851 static void commit(keyexch *kx, kxchal *kxc)
855 for (i = 0; i < kx->nr; i++) {
857 kxc_destroy(kx->r[i]);
862 ksl_link(kx->ks, kxc->ks);
865 /* --- @doreply@ --- *
867 * Arguments: @keyexch *kx@ = pointer to key exchange context
868 * @buf *b@ = buffer containing packet
870 * Returns: Zero if OK, nonzero if the packet was rejected.
872 * Use: Handles a reply packet. This doesn't handle the various
873 * switch packets: they're rather too different.
876 static int doreply(keyexch *kx, buf *b)
880 if (kx->s != KXS_CHAL && kx->s != KXS_COMMIT) {
881 a_warn("KX", "?PEER", kx->p, "unexpected", "reply", A_END);
884 if ((kxc = respond(kx, KX_REPLY, b)) == 0 ||
885 decryptrest(kx, kxc, KX_REPLY, b) ||
886 checkresponse(kx, KX_REPLY, b))
889 a_warn("KX", "?PEER", kx->p, "invalid", "reply", A_END);
892 if (kx->s == KXS_CHAL) {
903 /* --- @kxfinish@ --- *
905 * Arguments: @keyexch *kx@ = pointer to key exchange block
909 * Use: Sets everything up following a successful key exchange.
912 static void kxfinish(keyexch *kx)
914 kxchal *kxc = kx->r[0];
915 ks_activate(kxc->ks);
916 settimer(kx, ks_tregen(kxc->ks));
918 a_notify("KXDONE", "?PEER", kx->p, A_END);
919 p_stats(kx->p)->t_kx = time(0);
922 /* --- @doswitch@ --- *
924 * Arguments: @keyexch *kx@ = pointer to key exchange block
925 * @buf *b@ = pointer to buffer containing packet
927 * Returns: Zero if OK, nonzero if the packet was rejected.
929 * Use: Handles a reply with a switch request bolted onto it.
932 static int doswitch(keyexch *kx, buf *b)
934 const octet *hc_in, *hc_out, *hswrq;
937 if ((hc_in = buf_get(b, algs.hashsz)) == 0 ||
938 (hc_out = buf_get(b, algs.hashsz)) == 0) {
939 a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END);
942 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
943 trace_block(T_CRYPTO, "crypto: challenge", hc_in, algs.hashsz);
944 trace_block(T_CRYPTO, "crypto: cookie", hc_out, algs.hashsz);
946 if ((kxc = kxc_byhc(kx, hc_in)) == 0 ||
947 memcmp(hc_out, kx->hc, algs.hashsz) != 0) {
948 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END);
951 if (decryptrest(kx, kxc, KX_SWITCH, b) ||
952 checkresponse(kx, KX_SWITCH, b))
954 if ((hswrq = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) {
955 a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END);
958 IF_TRACING(T_KEYEXCH, {
959 trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, algs.hashsz);
961 if (memcmp(hswrq, kxc->hswrq_in, algs.hashsz) != 0) {
962 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END);
965 if (kx->s == KXS_CHAL)
967 if (kx->s < KXS_SWITCH)
976 /* --- @doswitchok@ --- *
978 * Arguments: @keyexch *kx@ = pointer to key exchange block
979 * @buf *b@ = pointer to buffer containing packet
981 * Returns: Zero if OK, nonzero if the packet was rejected.
983 * Use: Handles a reply with a switch request bolted onto it.
986 static int doswitchok(keyexch *kx, buf *b)
992 if (kx->s < KXS_COMMIT) {
993 a_warn("KX", "?PEER", kx->p, "unexpected", "switch-ok", A_END);
997 buf_init(&bb, buf_o, sizeof(buf_o));
998 if (decryptrest(kx, kxc, KX_SWITCHOK, b))
1000 if ((hswok = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) {
1001 a_warn("KX", "?PEER", kx->p, "invalid", "switch-ok", A_END);
1004 IF_TRACING(T_KEYEXCH, {
1005 trace_block(T_CRYPTO, "crypto: switch confirmation hash",
1006 hswok, algs.hashsz);
1008 if (memcmp(hswok, kxc->hswok_in, algs.hashsz) != 0) {
1009 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-ok", A_END);
1012 if (kx->s < KXS_SWITCH)
1020 /*----- Main code ---------------------------------------------------------*/
1024 * Arguments: @keyexch *kx@ = pointer to key exchange context
1028 * Use: Stops a key exchange dead in its tracks. Throws away all of
1029 * the context information. The context is left in an
1030 * inconsistent state. The only functions which understand this
1031 * state are @kx_free@ and @kx_init@ (which cause it internally
1032 * it), and @start@ (which expects it to be the prevailing
1036 static void stop(keyexch *kx)
1040 if (kx->f & KXF_DEAD)
1043 if (kx->f & KXF_TIMER)
1044 sel_rmtimer(&kx->t);
1045 for (i = 0; i < kx->nr; i++)
1046 kxc_destroy(kx->r[i]);
1048 G_DESTROY(gg, kx->c);
1049 G_DESTROY(gg, kx->rx);
1052 kx->f &= ~KXF_TIMER;
1055 /* --- @start@ --- *
1057 * Arguments: @keyexch *kx@ = pointer to key exchange context
1058 * @time_t now@ = the current time
1062 * Use: Starts a new key exchange with the peer. The context must be
1063 * in the bizarre state left by @stop@ or @kx_init@.
1066 static void start(keyexch *kx, time_t now)
1070 assert(kx->f & KXF_DEAD);
1072 kx->f &= ~(KXF_DEAD | KXF_CORK);
1074 kx->alpha = mprand_range(MP_NEW, gg->r, &rand_global, 0);
1075 kx->c = G_CREATE(gg); G_EXP(gg, kx->c, gg->g, kx->alpha);
1076 kx->rx = G_CREATE(gg); G_EXP(gg, kx->rx, kx->kpub, kx->alpha);
1078 kx->t_valid = now + T_VALID;
1080 h = GH_INIT(algs.h);
1081 HASH_STRING(h, "tripe-cookie");
1086 IF_TRACING(T_KEYEXCH, {
1087 trace(T_KEYEXCH, "keyexch: creating new challenge");
1088 IF_TRACING(T_CRYPTO, {
1089 trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha));
1090 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, kx->c));
1091 trace(T_CRYPTO, "crypto: expected response = %s", gestr(gg, kx->rx));
1092 trace_block(T_CRYPTO, "crypto: challenge cookie", kx->hc, algs.hashsz);
1097 /* --- @checkpub@ --- *
1099 * Arguments: @keyexch *kx@ = pointer to key exchange context
1101 * Returns: Zero if OK, nonzero if the peer's public key has expired.
1103 * Use: Deactivates the key-exchange until the peer acquires a new
1107 static int checkpub(keyexch *kx)
1110 if (kx->f & KXF_DEAD)
1113 if (KEY_EXPIRED(now, kx->texp_kpub)) {
1115 a_warn("KX", "?PEER", kx->p, "public-key-expired", A_END);
1116 G_COPY(gg, kx->kpub, gg->i);
1117 kx->f &= ~KXF_PUBKEY;
1123 /* --- @kx_start@ --- *
1125 * Arguments: @keyexch *kx@ = pointer to key exchange context
1126 * @int forcep@ = nonzero to ignore the quiet timer
1130 * Use: Stimulates a key exchange. If a key exchage is in progress,
1131 * a new challenge is sent (unless the quiet timer forbids
1132 * this); if no exchange is in progress, one is commenced.
1135 void kx_start(keyexch *kx, int forcep)
1137 time_t now = time(0);
1141 if (forcep || !VALIDP(kx, now)) {
1144 a_notify("KXSTART", "?PEER", kx->p, A_END);
1149 /* --- @kx_message@ --- *
1151 * Arguments: @keyexch *kx@ = pointer to key exchange context
1152 * @unsigned msg@ = the message code
1153 * @buf *b@ = pointer to buffer containing the packet
1157 * Use: Reads a packet containing key exchange messages and handles
1161 void kx_message(keyexch *kx, unsigned msg, buf *b)
1163 time_t now = time(0);
1164 stats *st = p_stats(kx->p);
1168 if (kx->f & KXF_CORK) {
1170 settimer(kx, now + T_RETRY);
1171 a_notify("KXSTART", A_END);
1177 if (!VALIDP(kx, now)) {
1181 T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'",
1182 msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); )
1186 rc = doprechallenge(kx, b);
1189 rc = dochallenge(kx, b);
1192 rc = doreply(kx, b);
1195 rc = doswitch(kx, b);
1198 rc = doswitchok(kx, b);
1201 a_warn("KX", "?PEER", kx->p, "unknown-message", "0x%02x", msg, A_END);
1214 /* --- @kx_free@ --- *
1216 * Arguments: @keyexch *kx@ = pointer to key exchange context
1220 * Use: Frees everything in a key exchange context.
1223 void kx_free(keyexch *kx)
1226 G_DESTROY(gg, kx->kpub);
1229 /* --- @kx_newkeys@ --- *
1231 * Arguments: @keyexch *kx@ = pointer to key exchange context
1235 * Use: Informs the key exchange module that its keys may have
1236 * changed. If fetching the new keys fails, the peer will be
1237 * destroyed, we log messages and struggle along with the old
1241 void kx_newkeys(keyexch *kx)
1243 if (km_getpubkey(p_tag(kx->p), kx->kpub, &kx->texp_kpub))
1245 kx->f |= KXF_PUBKEY;
1246 if ((kx->f & KXF_DEAD) || kx->s != KXS_SWITCH) {
1247 T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'",
1255 /* --- @kx_init@ --- *
1257 * Arguments: @keyexch *kx@ = pointer to key exchange context
1258 * @peer *p@ = pointer to peer context
1259 * @keyset **ks@ = pointer to keyset list
1260 * @unsigned f@ = various useful flags
1262 * Returns: Zero if OK, nonzero if it failed.
1264 * Use: Initializes a key exchange module. The module currently
1265 * contains no keys, and will attempt to initiate a key
1269 int kx_init(keyexch *kx, peer *p, keyset **ks, unsigned f)
1273 kx->kpub = G_CREATE(gg);
1274 if (km_getpubkey(p_tag(p), kx->kpub, &kx->texp_kpub)) {
1275 G_DESTROY(gg, kx->kpub);
1278 kx->f = KXF_DEAD | KXF_PUBKEY | f;
1279 if (!(kx->f & KXF_CORK)) {
1282 /* Don't notify here: the ADD message hasn't gone out yet. */
1287 /*----- That's all, folks -------------------------------------------------*/