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 * @struct timeval *tv@ = when to set the timer for
272 * Use: Sets the timer for the next key exchange attempt.
275 static void settimer(keyexch *kx, struct timeval *tv)
277 if (kx->f & KXF_TIMER) sel_rmtimer(&kx->t);
278 sel_addtimer(&sel, &kx->t, tv, timer, kx);
282 /*----- Challenge management ----------------------------------------------*/
284 /* --- Notes on challenge management --- *
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
297 /* --- @kxc_destroy@ --- *
299 * Arguments: @kxchal *kxc@ = pointer to the challenge block
303 * Use: Disposes of a challenge block.
306 static void kxc_destroy(kxchal *kxc)
308 if (kxc->f & KXF_TIMER)
309 sel_rmtimer(&kxc->t);
310 G_DESTROY(gg, kxc->c);
311 G_DESTROY(gg, kxc->r);
316 /* --- @kxc_stoptimer@ --- *
318 * Arguments: @kxchal *kxc@ = pointer to the challenge block
322 * Use: Stops the challenge's retry timer from sending messages.
323 * Useful when the state machine is in the endgame of the
327 static void kxc_stoptimer(kxchal *kxc)
329 if (kxc->f & KXF_TIMER)
330 sel_rmtimer(&kxc->t);
331 kxc->f &= ~KXF_TIMER;
334 /* --- @kxc_new@ --- *
336 * Arguments: @keyexch *kx@ = pointer to key exchange block
338 * Returns: A pointer to the challenge block.
340 * Use: Returns a pointer to a new challenge block to fill in.
343 static kxchal *kxc_new(keyexch *kx)
348 /* --- If we're over reply threshold, discard one at random --- */
350 if (kx->nr < KX_NCHAL)
353 i = rand_global.ops->range(&rand_global, KX_NCHAL);
354 kxc_destroy(kx->r[i]);
357 /* --- Fill in the new structure --- */
359 kxc = CREATE(kxchal);
360 kxc->c = G_CREATE(gg);
361 kxc->r = G_CREATE(gg);
369 /* --- @kxc_bychal@ --- *
371 * Arguments: @keyexch *kx@ = pointer to key exchange block
372 * @ge *c@ = challenge from remote host
374 * Returns: Pointer to the challenge block, or null.
376 * Use: Finds a challenge block, given its challenge.
379 static kxchal *kxc_bychal(keyexch *kx, ge *c)
383 for (i = 0; i < kx->nr; i++) {
384 if (G_EQ(gg, c, kx->r[i]->c))
390 /* --- @kxc_byhc@ --- *
392 * Arguments: @keyexch *kx@ = pointer to key exchange block
393 * @const octet *hc@ = challenge hash from remote host
395 * Returns: Pointer to the challenge block, or null.
397 * Use: Finds a challenge block, given a hash of its challenge.
400 static kxchal *kxc_byhc(keyexch *kx, const octet *hc)
404 for (i = 0; i < kx->nr; i++) {
405 if (memcmp(hc, kx->r[i]->hc, algs.hashsz) == 0)
411 /* --- @kxc_answer@ --- *
413 * Arguments: @keyexch *kx@ = pointer to key exchange block
414 * @kxchal *kxc@ = pointer to challenge block
418 * Use: Sends a reply to the remote host, according to the data in
419 * this challenge block.
422 static void kxc_answer(keyexch *kx, kxchal *kxc);
424 static void kxc_timer(struct timeval *tv, void *v)
427 kxc->f &= ~KXF_TIMER;
428 kxc_answer(kxc->kx, kxc);
431 static void kxc_answer(keyexch *kx, kxchal *kxc)
433 stats *st = p_stats(kx->p);
434 buf *b = p_txstart(kx->p, MSG_KEYEXCH | KX_REPLY);
438 /* --- Build the reply packet --- */
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);
445 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_REPLY, &bb, b);
447 /* --- Update the statistics --- */
451 st->sz_kxout += BLEN(b);
455 /* --- Schedule another resend --- */
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);
465 /*----- Individual message handlers ---------------------------------------*/
467 /* --- @doprechallenge@ --- *
469 * Arguments: @keyexch *kx@ = pointer to key exchange block
470 * @buf *b@ = buffer containing the packet
472 * Returns: Zero if OK, nonzero of the packet was rejected.
474 * Use: Processes a pre-challenge message.
477 static int doprechallenge(keyexch *kx, buf *b)
479 stats *st = p_stats(kx->p);
480 ge *c = G_CREATE(gg);
483 /* --- Ensure that we're in a sensible state --- */
485 if (kx->s != KXS_CHAL) {
486 a_warn("KX", "?PEER", kx->p, "unexpected", "pre-challenge", A_END);
490 /* --- Unpack the packet --- */
492 if (G_FROMBUF(gg, b, c) || BLEFT(b))
495 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
496 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c));
499 /* --- Send out a full challenge by return --- */
501 b = p_txstart(kx->p, MSG_KEYEXCH | KX_CHAL);
503 HASH_STRING(h, "tripe-cookie");
505 sendchallenge(kx, b, c, GH_DONE(h, 0));
508 st->sz_kxout += BLEN(b);
517 if (c) G_DESTROY(gg, c);
521 /* --- @respond@ --- *
523 * Arguments: @keyexch *kx@ = pointer to key exchange block
524 * @unsigned msg@ = message code for this packet
525 * @buf *b@ = buffer containing the packet
527 * Returns: Key-exchange challenge block, or null.
529 * Use: Computes a response for the given challenge, entering it into
530 * a challenge block and so on.
533 static kxchal *respond(keyexch *kx, unsigned msg, buf *b)
535 ge *c = G_CREATE(gg);
536 ge *r = G_CREATE(gg);
537 ge *cc = G_CREATE(gg);
538 const octet *hc, *ck;
546 /* --- Unpack the packet --- */
548 if (G_FROMBUF(gg, b, c) ||
549 (hc = buf_get(b, algs.hashsz)) == 0 ||
550 (ck = buf_get(b, indexsz)) == 0) {
551 a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END);
554 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
555 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c));
556 trace_block(T_CRYPTO, "crypto: cookie", hc, algs.hashsz);
557 trace_block(T_CRYPTO, "crypto: check-value", ck, indexsz);
560 /* --- Discard a packet with an invalid cookie --- */
562 if (hc && memcmp(hc, kx->hc, algs.hashsz) != 0) {
563 a_warn("KX", "?PEER", kx->p, "incorrect", "cookie", A_END);
567 /* --- Recover the check value and verify it --- *
569 * To avoid recomputation on replays, we store a hash of the `right'
570 * value. The `correct' value is unique, so this is right.
572 * This will also find a challenge block and, if necessary, populate it.
575 if ((kxc = kxc_bychal(kx, c)) != 0) {
577 HASH_STRING(h, "tripe-check-hash");
578 GH_HASH(h, ck, indexsz);
579 ok = !memcmp(kxc->ck, GH_DONE(h, 0), algs.hashsz);
581 if (!ok) goto badcheck;
584 /* --- Compute the reply, and check the magic --- */
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));
593 if (MP_CMP(cv, >, gg->r) ||
594 (G_EXP(gg, cc, gg->g, cv), !G_EQ(gg, c, cc)))
597 /* --- Fill in a new challenge block --- */
600 G_COPY(gg, kxc->c, c);
601 G_COPY(gg, kxc->r, r);
604 HASH_STRING(h, "tripe-check-hash");
605 GH_HASH(h, ck, indexsz);
610 HASH_STRING(h, "tripe-cookie");
615 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
616 trace_block(T_CRYPTO, "crypto: computed cookie", kxc->hc, algs.hashsz);
619 /* --- Work out the shared key --- */
621 G_EXP(gg, r, c, kx->alpha);
622 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
623 trace(T_CRYPTO, "crypto: shared secret = %s", gestr(gg, r));
626 /* --- Compute the switch messages --- */
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);
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);
642 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
643 trace_block(T_CRYPTO, "crypto: outbound switch request",
644 kxc->hswrq_out, algs.hashsz);
645 trace_block(T_CRYPTO, "crypto: outbound switch confirm",
646 kxc->hswok_out, algs.hashsz);
647 trace_block(T_CRYPTO, "crypto: inbound switch request",
648 kxc->hswrq_in, algs.hashsz);
649 trace_block(T_CRYPTO, "crypto: inbound switch confirm",
650 kxc->hswok_in, algs.hashsz);
653 /* --- Create a new symmetric keyset --- */
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);
661 kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p);
671 a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END);
681 /* --- @dochallenge@ --- *
683 * Arguments: @keyexch *kx@ = pointer to key exchange block
684 * @unsigned msg@ = message code for the packet
685 * @buf *b@ = buffer containing the packet
687 * Returns: Zero if OK, nonzero if the packet was rejected.
689 * Use: Processes a packet containing a challenge.
692 static int dochallenge(keyexch *kx, buf *b)
696 if (kx->s != KXS_CHAL) {
697 a_warn("KX", "?PEER", kx->p, "unexpected", "challenge", A_END);
700 if ((kxc = respond(kx, KX_CHAL, b)) == 0)
703 a_warn("KX", "?PEER", kx->p, "invalid", "challenge", A_END);
713 /* --- @resend@ --- *
715 * Arguments: @keyexch *kx@ = pointer to key exchange context
719 * Use: Sends the next message for a key exchange.
722 static void resend(keyexch *kx)
726 stats *st = p_stats(kx->p);
732 T( trace(T_KEYEXCH, "keyexch: sending prechallenge to `%s'",
734 b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL);
735 G_TOBUF(gg, b, kx->c);
738 T( trace(T_KEYEXCH, "keyexch: sending switch request to `%s'",
741 b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH);
742 buf_put(b, kx->hc, algs.hashsz);
743 buf_put(b, kxc->hc, algs.hashsz);
744 buf_init(&bb, buf_i, sizeof(buf_i));
745 G_TORAW(gg, &bb, kxc->r);
746 buf_put(&bb, kxc->hswrq_out, algs.hashsz);
748 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCH, &bb, b);
751 T( trace(T_KEYEXCH, "keyexch: sending switch confirmation to `%s'",
754 b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK);
755 buf_init(&bb, buf_i, sizeof(buf_i));
756 buf_put(&bb, kxc->hswok_out, algs.hashsz);
758 ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCHOK, &bb, b);
766 st->sz_kxout += BLEN(b);
770 if (kx->s < KXS_SWITCH) {
771 gettimeofday(&tv, 0);
772 tv.tv_sec += 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];
917 ks_activate(kxc->ks);
918 gettimeofday(&tv, 0);
919 tv.tv_sec += T_REGEN;
922 a_notify("KXDONE", "?PEER", kx->p, A_END);
923 p_stats(kx->p)->t_kx = time(0);
926 /* --- @doswitch@ --- *
928 * Arguments: @keyexch *kx@ = pointer to key exchange block
929 * @buf *b@ = pointer to buffer containing packet
931 * Returns: Zero if OK, nonzero if the packet was rejected.
933 * Use: Handles a reply with a switch request bolted onto it.
936 static int doswitch(keyexch *kx, buf *b)
938 const octet *hc_in, *hc_out, *hswrq;
941 if ((hc_in = buf_get(b, algs.hashsz)) == 0 ||
942 (hc_out = buf_get(b, algs.hashsz)) == 0) {
943 a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END);
946 IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
947 trace_block(T_CRYPTO, "crypto: challenge", hc_in, algs.hashsz);
948 trace_block(T_CRYPTO, "crypto: cookie", hc_out, algs.hashsz);
950 if ((kxc = kxc_byhc(kx, hc_in)) == 0 ||
951 memcmp(hc_out, kx->hc, algs.hashsz) != 0) {
952 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END);
955 if (decryptrest(kx, kxc, KX_SWITCH, b) ||
956 checkresponse(kx, KX_SWITCH, b))
958 if ((hswrq = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) {
959 a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END);
962 IF_TRACING(T_KEYEXCH, {
963 trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, algs.hashsz);
965 if (memcmp(hswrq, kxc->hswrq_in, algs.hashsz) != 0) {
966 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END);
969 if (kx->s == KXS_CHAL)
971 if (kx->s < KXS_SWITCH)
980 /* --- @doswitchok@ --- *
982 * Arguments: @keyexch *kx@ = pointer to key exchange block
983 * @buf *b@ = pointer to buffer containing packet
985 * Returns: Zero if OK, nonzero if the packet was rejected.
987 * Use: Handles a reply with a switch request bolted onto it.
990 static int doswitchok(keyexch *kx, buf *b)
996 if (kx->s < KXS_COMMIT) {
997 a_warn("KX", "?PEER", kx->p, "unexpected", "switch-ok", A_END);
1001 buf_init(&bb, buf_o, sizeof(buf_o));
1002 if (decryptrest(kx, kxc, KX_SWITCHOK, b))
1004 if ((hswok = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) {
1005 a_warn("KX", "?PEER", kx->p, "invalid", "switch-ok", A_END);
1008 IF_TRACING(T_KEYEXCH, {
1009 trace_block(T_CRYPTO, "crypto: switch confirmation hash",
1010 hswok, algs.hashsz);
1012 if (memcmp(hswok, kxc->hswok_in, algs.hashsz) != 0) {
1013 a_warn("KX", "?PEER", kx->p, "incorrect", "switch-ok", A_END);
1016 if (kx->s < KXS_SWITCH)
1024 /*----- Main code ---------------------------------------------------------*/
1028 * Arguments: @keyexch *kx@ = pointer to key exchange context
1032 * Use: Stops a key exchange dead in its tracks. Throws away all of
1033 * the context information. The context is left in an
1034 * inconsistent state. The only functions which understand this
1035 * state are @kx_free@ and @kx_init@ (which cause it internally
1036 * it), and @start@ (which expects it to be the prevailing
1040 static void stop(keyexch *kx)
1044 if (kx->f & KXF_DEAD)
1047 if (kx->f & KXF_TIMER)
1048 sel_rmtimer(&kx->t);
1049 for (i = 0; i < kx->nr; i++)
1050 kxc_destroy(kx->r[i]);
1052 G_DESTROY(gg, kx->c);
1053 G_DESTROY(gg, kx->rx);
1056 kx->f &= ~KXF_TIMER;
1059 /* --- @start@ --- *
1061 * Arguments: @keyexch *kx@ = pointer to key exchange context
1062 * @time_t now@ = the current time
1066 * Use: Starts a new key exchange with the peer. The context must be
1067 * in the bizarre state left by @stop@ or @kx_init@.
1070 static void start(keyexch *kx, time_t now)
1074 assert(kx->f & KXF_DEAD);
1076 kx->f &= ~(KXF_DEAD | KXF_CORK);
1078 kx->alpha = mprand_range(MP_NEW, gg->r, &rand_global, 0);
1079 kx->c = G_CREATE(gg); G_EXP(gg, kx->c, gg->g, kx->alpha);
1080 kx->rx = G_CREATE(gg); G_EXP(gg, kx->rx, kx->kpub, kx->alpha);
1082 kx->t_valid = now + T_VALID;
1084 h = GH_INIT(algs.h);
1085 HASH_STRING(h, "tripe-cookie");
1090 IF_TRACING(T_KEYEXCH, {
1091 trace(T_KEYEXCH, "keyexch: creating new challenge");
1092 IF_TRACING(T_CRYPTO, {
1093 trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha));
1094 trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, kx->c));
1095 trace(T_CRYPTO, "crypto: expected response = %s", gestr(gg, kx->rx));
1096 trace_block(T_CRYPTO, "crypto: challenge cookie", kx->hc, algs.hashsz);
1101 /* --- @checkpub@ --- *
1103 * Arguments: @keyexch *kx@ = pointer to key exchange context
1105 * Returns: Zero if OK, nonzero if the peer's public key has expired.
1107 * Use: Deactivates the key-exchange until the peer acquires a new
1111 static int checkpub(keyexch *kx)
1114 if (kx->f & KXF_DEAD)
1117 if (KEY_EXPIRED(now, kx->texp_kpub)) {
1119 a_warn("KX", "?PEER", kx->p, "public-key-expired", A_END);
1120 G_COPY(gg, kx->kpub, gg->i);
1121 kx->f &= ~KXF_PUBKEY;
1127 /* --- @kx_start@ --- *
1129 * Arguments: @keyexch *kx@ = pointer to key exchange context
1130 * @int forcep@ = nonzero to ignore the quiet timer
1134 * Use: Stimulates a key exchange. If a key exchage is in progress,
1135 * a new challenge is sent (unless the quiet timer forbids
1136 * this); if no exchange is in progress, one is commenced.
1139 void kx_start(keyexch *kx, int forcep)
1141 time_t now = time(0);
1145 if (forcep || !VALIDP(kx, now)) {
1148 a_notify("KXSTART", "?PEER", kx->p, A_END);
1153 /* --- @kx_message@ --- *
1155 * Arguments: @keyexch *kx@ = pointer to key exchange context
1156 * @unsigned msg@ = the message code
1157 * @buf *b@ = pointer to buffer containing the packet
1161 * Use: Reads a packet containing key exchange messages and handles
1165 void kx_message(keyexch *kx, unsigned msg, buf *b)
1167 struct timeval now, tv;
1168 stats *st = p_stats(kx->p);
1172 gettimeofday(&now, 0);
1173 if (kx->f & KXF_CORK) {
1174 start(kx, now.tv_sec);
1175 TV_ADDL(&tv, &now, T_RETRY, 0);
1177 a_notify("KXSTART", A_END);
1183 if (!VALIDP(kx, now.tv_sec)) {
1185 start(kx, now.tv_sec);
1187 T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'",
1188 msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); )
1192 rc = doprechallenge(kx, b);
1195 rc = dochallenge(kx, b);
1198 rc = doreply(kx, b);
1201 rc = doswitch(kx, b);
1204 rc = doswitchok(kx, b);
1207 a_warn("KX", "?PEER", kx->p, "unknown-message", "0x%02x", msg, A_END);
1220 /* --- @kx_free@ --- *
1222 * Arguments: @keyexch *kx@ = pointer to key exchange context
1226 * Use: Frees everything in a key exchange context.
1229 void kx_free(keyexch *kx)
1232 G_DESTROY(gg, kx->kpub);
1235 /* --- @kx_newkeys@ --- *
1237 * Arguments: @keyexch *kx@ = pointer to key exchange context
1241 * Use: Informs the key exchange module that its keys may have
1242 * changed. If fetching the new keys fails, the peer will be
1243 * destroyed, we log messages and struggle along with the old
1247 void kx_newkeys(keyexch *kx)
1249 if (km_getpubkey(p_tag(kx->p), kx->kpub, &kx->texp_kpub))
1251 kx->f |= KXF_PUBKEY;
1252 if ((kx->f & KXF_DEAD) || kx->s != KXS_SWITCH) {
1253 T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'",
1261 /* --- @kx_init@ --- *
1263 * Arguments: @keyexch *kx@ = pointer to key exchange context
1264 * @peer *p@ = pointer to peer context
1265 * @keyset **ks@ = pointer to keyset list
1266 * @unsigned f@ = various useful flags
1268 * Returns: Zero if OK, nonzero if it failed.
1270 * Use: Initializes a key exchange module. The module currently
1271 * contains no keys, and will attempt to initiate a key
1275 int kx_init(keyexch *kx, peer *p, keyset **ks, unsigned f)
1279 kx->kpub = G_CREATE(gg);
1280 if (km_getpubkey(p_tag(p), kx->kpub, &kx->texp_kpub)) {
1281 G_DESTROY(gg, kx->kpub);
1284 kx->f = KXF_DEAD | KXF_PUBKEY | f;
1285 if (!(kx->f & KXF_CORK)) {
1288 /* Don't notify here: the ADD message hasn't gone out yet. */
1293 /*----- That's all, folks -------------------------------------------------*/