3 * $Id: keyexch.c,v 1.10 2003/10/15 09:29:38 mdw Exp $
5 * Key exchange protocol
7 * (c) 2001 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Trivial IP Encryption (TrIPE).
14 * TrIPE is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
19 * TrIPE is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
24 * You should have received a copy of the GNU General Public License
25 * along with TrIPE; if not, write to the Free Software Foundation,
26 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
29 /*----- Revision history --------------------------------------------------*
32 * Revision 1.10 2003/10/15 09:29:38 mdw
33 * Cosmetic fix to changelog comment.
35 * Revision 1.9 2003/07/13 11:53:14 mdw
36 * Add protocol commentary.
38 * Revision 1.8 2003/07/13 11:19:49 mdw
39 * Incompatible protocol fix! Include message type code under MAC tag to
40 * prevent cut-and-paste from key-exchange messages to general packet
43 * Revision 1.7 2003/05/17 11:01:28 mdw
44 * Handle flags on challenge timers correctly to prevent confusing the event
47 * Revision 1.6 2003/04/06 10:26:35 mdw
48 * Report peer name on decrypt errors.
50 * Revision 1.5 2002/01/13 14:54:40 mdw
51 * Patch up zero-knowledge property by passing an encrypted log with a
52 * challenge, so that the prover can verify that the challenge is good.
54 * Revision 1.4 2001/06/22 19:40:36 mdw
55 * Support expiry of other peers' public keys.
57 * Revision 1.3 2001/06/19 22:07:09 mdw
60 * Revision 1.2 2001/02/16 21:24:27 mdw
61 * Rewrite for new key exchange protocol.
63 * Revision 1.1 2001/02/03 20:26:37 mdw
68 /*----- Header files ------------------------------------------------------*/
72 /*----- Brief protocol overview -------------------------------------------*
74 * Let %$G$% be a cyclic group; let %$g$% be a generator of %$G$%, and let
75 * %$q$% be the order of %$G$%; for a key %$K$%, let %$E_K(\cdot)$% denote
76 * application of the symmetric packet protocol to a message; let
77 * %$H(\cdot)$% be the random oracle. Let $\alpha \inr \{0,\ldots,q - 1\}$%
78 * be Alice's private key; let %$a = g^\alpha$% be her public key; let %$b$%
79 * be Bob's public key.
81 * At the beginning of the session, Alice chooses
83 * %$\rho_A \inr \{0, \ldots q - 1\}$%
87 * %$r_A = g^{\rho_A}$% Alice's challenge
88 * %$c_A = H(\cookie{cookie}, r_A)$% Alice's cookie
89 * %$v_A = \rho_A \xor H(\cookie{expected-reply}, r_A, r_B, b^{\rho_A})$%
90 * Alice's challenge check value
91 * %$r_B^\alpha = a^{\rho_B}$% Alice's reply
92 * %$K = r_B^{\rho_A} = r_B^{\rho_A} = g^{\rho_A\rho_B}$%
93 * Alice and Bob's shared secret key
94 * %$w_A = H(\cookie{switch-request}, c_A, c_B)$%
95 * Alice's switch request value
96 * %$u_A = H(\cookie{switch-confirm}, c_A, c_B)$%
97 * Alice's switch confirm value
99 * The messages are then:
101 * %$\cookie{kx-pre-challenge}, r_A$%
102 * Initial greeting. In state @KXS_CHAL@.
104 * %$\cookie{kx-cookie}, r_A, c_B$%
105 * My table is full but I got your message.
107 * %$\cookie{kx-challenge}, r_A, c_B, v_A$%
108 * Here's a full challenge for you to answer.
110 * %$\cookie{kx-reply}, c_A, c_B, v_A, E_K(r_B^\alpha))$%
111 * Challenge accpeted: here's the answer. Commit to my challenge. Move
114 * %$\cookie{kx-switch}, c_A, c_B, E_K(r_B^\alpha, w_A))$%
115 * Reply received: here's my reply. Committed; send data; move to
118 * %$\cookie{kx-switch-ok}, E_K(u_A))$%
119 * Switch received. Committed; send data; move to @KXS_SWITCH@.
122 /*----- Tunable parameters ------------------------------------------------*/
124 #define T_VALID MIN(2) /* Challenge validity period */
125 #define T_RETRY SEC(10) /* Challenge retransmit interval */
127 #define ISVALID(kx, now) ((now) < (kx)->t_valid)
129 /*----- Various utilities -------------------------------------------------*/
131 /* --- @hashmp@ --- *
133 * Arguments: @HASH_CTX *r@ = pointer to hash context
134 * @mp *m@ = pointer to multiprecision integer
138 * Use: Adds the hash of a multiprecision integer to the context.
142 static void hashmp(HASH_CTX
*r
, mp
*m
)
145 buf_init(&b
, buf_t
, sizeof(buf_t
));
148 HASH(r
, BBASE(&b
), BLEN(&b
));
151 /* --- @mpcrypt@ --- *
153 * Arguments: @mp *d@ = the destination integer
154 * @mp *x@ = the plaintext/ciphertext integer
155 * @size_t sz@ = the expected size of the plaintext
156 * @const octet *k@ = pointer to key material
157 * @size_t ksz@ = size of the key
159 * Returns: The encrypted/decrypted integer.
161 * Use: Encrypts (or decrypts) a multiprecision integer using another
162 * multiprecision integer as the key. This is a slightly grotty
163 * way to do this, but it's easier than the alternatives.
166 static mp
*mpcrypt(mp
*d
, mp
*x
, size_t sz
, const octet
*k
, size_t ksz
)
170 MGF_INIT(&m
, k
, ksz
, 0);
171 mp_storeb(x
, buf_t
, sz
);
172 MGF_CRYPT(&m
, buf_t
, buf_t
, sz
);
173 return (mp_loadb(d
, buf_t
, sz
));
178 * Arguments: @struct timeval *tv@ = the current time
179 * @void *v@ = pointer to key exchange context
183 * Use: Acts when the key exchange timer goes off.
186 static void timer(struct timeval
*tv
, void *v
)
190 T( trace(T_KEYEXCH
, "keyexch: timer has popped"); )
194 /* --- @settimer@ --- *
196 * Arguments: @keyexch *kx@ = pointer to key exchange context
197 * @time_t t@ = when to set the timer for
201 * Use: Sets the timer for the next key exchange attempt.
204 static void settimer(keyexch
*kx
, time_t t
)
207 if (kx
->f
& KXF_TIMER
)
211 sel_addtimer(&sel
, &kx
->t
, &tv
, timer
, kx
);
215 /*----- Challenge management ----------------------------------------------*/
217 /* --- Notes on challenge management --- *
219 * We may get multiple different replies to our key exchange; some will be
220 * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges
221 * received will be added to the table and given a full response. After
222 * @KX_THRESH@ distinct challenges are received, we return only a `cookie':
223 * our existing challenge, followed by a hash of the sender's challenge. We
224 * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All
225 * properly-formed cookies are assigned a table slot: if none is spare, a
226 * used slot is randomly selected and destroyed. A cookie always receives a
230 /* --- @kxc_destroy@ --- *
232 * Arguments: @kxchal *kxc@ = pointer to the challenge block
236 * Use: Disposes of a challenge block.
239 static void kxc_destroy(kxchal
*kxc
)
241 if (kxc
->f
& KXF_TIMER
)
242 sel_rmtimer(&kxc
->t
);
250 /* --- @kxc_stoptimer@ --- *
252 * Arguments: @kxchal *kxc@ = pointer to the challenge block
256 * Use: Stops the challenge's retry timer from sending messages.
257 * Useful when the state machine is in the endgame of the
261 static void kxc_stoptimer(kxchal
*kxc
)
263 if (kxc
->f
& KXF_TIMER
)
264 sel_rmtimer(&kxc
->t
);
265 kxc
->f
&= ~KXF_TIMER
;
268 /* --- @kxc_new@ --- *
270 * Arguments: @keyexch *kx@ = pointer to key exchange block
272 * Returns: A pointer to the challenge block.
274 * Use: Returns a pointer to a new challenge block to fill in.
277 static kxchal
*kxc_new(keyexch
*kx
)
282 /* --- If we're over reply threshold, discard one at random --- */
284 if (kx
->nr
< KX_NCHAL
)
287 i
= rand_global
.ops
->range(&rand_global
, KX_NCHAL
);
288 kxc_destroy(kx
->r
[i
]);
291 /* --- Fill in the new structure --- */
293 kxc
= CREATE(kxchal
);
304 /* --- @kxc_bychal@ --- *
306 * Arguments: @keyexch *kx@ = pointer to key exchange block
307 * @mp *c@ = challenge from remote host
309 * Returns: Pointer to the challenge block, or null.
311 * Use: Finds a challenge block, given its challenge.
314 static kxchal
*kxc_bychal(keyexch
*kx
, mp
*c
)
318 for (i
= 0; i
< kx
->nr
; i
++) {
319 if (MP_EQ(c
, kx
->r
[i
]->c
))
325 /* --- @kxc_byhc@ --- *
327 * Arguments: @keyexch *kx@ = pointer to key exchange block
328 * @const octet *hc@ = challenge hash from remote host
330 * Returns: Pointer to the challenge block, or null.
332 * Use: Finds a challenge block, given a hash of its challenge.
335 static kxchal
*kxc_byhc(keyexch
*kx
, const octet
*hc
)
339 for (i
= 0; i
< kx
->nr
; i
++) {
340 if (memcmp(hc
, kx
->r
[i
]->hc
, HASHSZ
) == 0)
346 /* --- @kxc_answer@ --- *
348 * Arguments: @keyexch *kx@ = pointer to key exchange block
349 * @kxchal *kxc@ = pointer to challenge block
353 * Use: Sends a reply to the remote host, according to the data in
354 * this challenge block.
357 static void kxc_answer(keyexch
*kx
, kxchal
*kxc
);
359 static void kxc_timer(struct timeval
*tv
, void *v
)
362 kxc
->f
&= ~KXF_TIMER
;
363 kxc_answer(kxc
->kx
, kxc
);
366 static void kxc_answer(keyexch
*kx
, kxchal
*kxc
)
368 stats
*st
= p_stats(kx
->p
);
369 buf
*b
= p_txstart(kx
->p
, MSG_KEYEXCH
| (kxc
->r ? KX_REPLY
: KX_CHAL
));
373 /* --- Build the reply packet --- */
378 buf_put(b
, kx
->hc
, HASHSZ
);
379 buf_put(b
, kxc
->hc
, HASHSZ
);
380 buf_putmp(b
, kxc
->ck
);
382 /* --- Maybe send an actual reply, if we have one --- */
385 T( trace(T_KEYEXCH
, "keyexch: resending challenge to `%s'",
388 T( trace(T_KEYEXCH
, "keyexch: sending reply to `%s'", p_name(kx
->p
)); )
389 buf_init(&bb
, buf_i
, sizeof(buf_i
));
390 buf_putmp(&bb
, kxc
->r
);
392 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_REPLY
, &bb
, b
);
395 /* --- Update the statistics --- */
399 st
->sz_kxout
+= BLEN(b
);
403 /* --- Schedule another resend --- */
405 if (kxc
->f
& KXF_TIMER
)
406 sel_rmtimer(&kxc
->t
);
407 gettimeofday(&tv
, 0);
408 tv
.tv_sec
+= T_RETRY
;
409 sel_addtimer(&sel
, &kxc
->t
, &tv
, kxc_timer
, kxc
);
413 /*----- Individual message handlers ---------------------------------------*/
415 /* --- @getreply@ --- *
417 * Arguments: @keyexch *kx@ = pointer to key exchange context
418 * @mp *c@ = a challenge
419 * @mp *ck@ = the supplied expected-reply check value
421 * Returns: A pointer to the reply, or null if the reply-hash was wrong.
423 * Use: Computes replies to challenges.
426 static mp
*getreply(keyexch
*kx
, mp
*c
, mp
*ck
)
428 mp
*r
= mpmont_exp(&mg
, MP_NEW
, c
, kpriv
.x
);
435 HASH_STRING(&h
, "tripe-expected-reply");
441 a
= mpcrypt(MP_NEW
, ck
, mp_octets(kpriv
.dp
.q
), buf
, sizeof(buf
));
442 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
443 trace(T_CRYPTO
, "crypto: computed reply = %s", mpstr(r
));
444 trace_block(T_CRYPTO
, "crypto: computed reply hash", buf
, HASHSZ
);
445 trace(T_CRYPTO
, "crypto: recovered log = %s", mpstr(a
));
447 a
= mpmont_exp(&mg
, a
, kpriv
.dp
.g
, a
);
450 a_warn("invalid expected-reply check from `%s'", p_name(kx
->p
));
451 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
452 trace(T_CRYPTO
, "crypto: computed challenge = %s", mpstr(a
));
460 /* --- @dochallenge@ --- *
462 * Arguments: @keyexch *kx@ = pointer to key exchange block
463 * @unsigned msg@ = message code for the packet
464 * @buf *b@ = buffer containing the packet
466 * Returns: Zero if OK, nonzero if the packet was rejected.
468 * Use: Processes a packet containing a challenge.
471 static int dochallenge(keyexch
*kx
, unsigned msg
, buf
*b
)
479 /* --- Ensure that we're in a sensible state --- */
481 if (kx
->s
!= KXS_CHAL
) {
482 a_warn("unexpected challenge from `%s'", p_name(kx
->p
));
486 /* --- Unpack the packet --- */
488 if ((c
= buf_getmp(b
)) == 0 ||
489 (msg
>= KX_COOKIE
&& (hc
= buf_get(b
, HASHSZ
)) == 0) ||
490 (msg
>= KX_CHAL
&& (ck
= buf_getmp(b
)) == 0) ||
492 a_warn("malformed packet from `%s'", p_name(kx
->p
));
496 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
497 trace(T_CRYPTO
, "crypto: challenge = %s", mpstr(c
));
498 if (hc
) trace_block(T_CRYPTO
, "crypto: cookie", hc
, HASHSZ
);
499 if (ck
) trace(T_CRYPTO
, "crypto: check value = %s", mpstr(ck
));
502 /* --- First, handle a bare challenge --- *
504 * If the table is heavily loaded, just emit a cookie and return.
507 if (!hc
&& kx
->nr
>= KX_THRESH
) {
508 T( trace(T_KEYEXCH
, "keyexch: too many challenges -- sending cookie"); )
509 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_COOKIE
);
512 HASH_STRING(&h
, "tripe-cookie");
514 HASH_DONE(&h
, buf_get(b
, HASHSZ
));
519 /* --- Discard a packet with an invalid cookie --- */
521 if (hc
&& memcmp(hc
, kx
->hc
, HASHSZ
) != 0) {
522 a_warn("incorrect cookie from `%s'", p_name(kx
->p
));
526 /* --- Find a challenge block for this packet --- *
528 * If there isn't one already, create a new one.
531 if ((kxc
= kxc_bychal(kx
, c
)) == 0) {
535 /* --- Be careful here --- *
537 * If this is a full challenge, and it's the first time I've seen it, I
538 * want to be able to throw it away before committing a table entry to
545 if ((r
= getreply(kx
, c
, ck
)) == 0)
552 /* --- Work out the cookie for this challenge --- */
555 HASH_STRING(&h
, "tripe-cookie");
557 HASH_DONE(&h
, kxc
->hc
);
559 /* --- Compute the expected-reply hash --- */
562 HASH_STRING(&h
, "tripe-expected-reply");
567 kxc
->ck
= mpcrypt(MP_NEW
, kx
->alpha
, mp_octets(kpriv
.dp
.q
),
570 /* --- Work out the shared key --- */
572 trace(T_CRYPTO
, "debug: c = %s", mpstr(c
));
573 trace(T_CRYPTO
, "debug: alpha = %s", mpstr(kx
->alpha
));
574 r
= mpmont_exp(&mg
, MP_NEW
, c
, kx
->alpha
);
575 trace(T_CRYPTO
, "debug: r = %s", mpstr(r
));
577 /* --- Compute the switch messages --- */
579 HASH_INIT(&h
); HASH_STRING(&h
, "tripe-switch-request");
580 hashmp(&h
, kx
->c
); hashmp(&h
, kxc
->c
);
581 HASH_DONE(&h
, kxc
->hswrq_out
);
582 HASH_INIT(&h
); HASH_STRING(&h
, "tripe-switch-confirm");
583 hashmp(&h
, kx
->c
); hashmp(&h
, kxc
->c
);
584 HASH_DONE(&h
, kxc
->hswok_out
);
586 HASH_INIT(&h
); HASH_STRING(&h
, "tripe-switch-request");
587 hashmp(&h
, kxc
->c
); hashmp(&h
, kx
->c
);
588 HASH_DONE(&h
, kxc
->hswrq_in
);
589 HASH_INIT(&h
); HASH_STRING(&h
, "tripe-switch-confirm");
590 hashmp(&h
, kxc
->c
); hashmp(&h
, kx
->c
);
591 HASH_DONE(&h
, kxc
->hswok_in
);
593 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
594 trace_block(T_CRYPTO
, "crypto: computed cookie", kxc
->hc
, HASHSZ
);
595 trace_block(T_CRYPTO
, "crypto: expected-reply hash",
597 trace(T_CRYPTO
, "crypto: my reply check = %s", mpstr(kxc
->ck
));
598 trace(T_CRYPTO
, "crypto: shared secret = %s", mpstr(r
));
599 trace_block(T_CRYPTO
, "crypto: outbound switch request",
600 kxc
->hswrq_out
, HASHSZ
);
601 trace_block(T_CRYPTO
, "crypto: outbound switch confirm",
602 kxc
->hswok_out
, HASHSZ
);
603 trace_block(T_CRYPTO
, "crypto: inbound switch request",
604 kxc
->hswrq_in
, HASHSZ
);
605 trace_block(T_CRYPTO
, "crypto: inbound switch confirm",
606 kxc
->hswok_in
, HASHSZ
);
609 /* --- Create a new symmetric keyset --- */
611 buf_init(b
, buf_o
, sizeof(buf_o
));
612 buf_putmp(b
, kx
->c
); x
= BLEN(b
);
613 buf_putmp(b
, kxc
->c
); y
= BLEN(b
);
614 buf_putmp(b
, r
); z
= BLEN(b
);
617 kxc
->ks
= ks_gen(BBASE(b
), x
, y
, z
, kx
->p
);
621 /* --- Answer the challenge if we need to --- */
625 if ((r
= getreply(kx
, c
, ck
)) == 0)
632 /* --- Tidy up and go home --- */
645 /* --- @resend@ --- *
647 * Arguments: @keyexch *kx@ = pointer to key exchange context
651 * Use: Sends the next message for a key exchange.
654 static void resend(keyexch
*kx
)
658 stats
*st
= p_stats(kx
->p
);
663 T( trace(T_KEYEXCH
, "keyexch: sending prechallenge to `%s'",
665 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_PRECHAL
);
669 T( trace(T_KEYEXCH
, "keyexch: sending switch request to `%s'",
672 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCH
);
673 buf_put(b
, kx
->hc
, HASHSZ
);
674 buf_put(b
, kxc
->hc
, HASHSZ
);
675 buf_init(&bb
, buf_i
, sizeof(buf_i
));
676 buf_putmp(&bb
, kxc
->r
);
677 buf_put(&bb
, kxc
->hswrq_out
, HASHSZ
);
679 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCH
, &bb
, b
);
682 T( trace(T_KEYEXCH
, "keyexch: sending switch confirmation to `%s'",
685 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCHOK
);
686 buf_init(&bb
, buf_i
, sizeof(buf_i
));
687 buf_put(&bb
, kxc
->hswok_out
, HASHSZ
);
689 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCHOK
, &bb
, b
);
697 st
->sz_kxout
+= BLEN(b
);
701 if (kx
->s
< KXS_SWITCH
)
702 settimer(kx
, time(0) + T_RETRY
);
705 /* --- @matchreply@ --- *
707 * Arguments: @keyexch *kx@ = pointer to key exchange context
708 * @unsigned ty@ = type of incoming message
709 * @const octet *hc_in@ = a hash of his challenge
710 * @const octet *hc_out@ = a hash of my challenge (cookie)
711 * @mp *ck@ = his expected-reply hash (optional)
712 * @buf *b@ = encrypted remainder of the packet
714 * Returns: A pointer to the challenge block if OK, or null on failure.
716 * Use: Checks a reply or switch packet, ensuring that its contents
717 * are sensible and correct. If they are, @*b@ is set to point
718 * to the remainder of the encrypted data, and the correct
719 * challenge is returned.
722 static kxchal
*matchreply(keyexch
*kx
, unsigned ty
, const octet
*hc_in
,
723 const octet
*hc_out
, mp
*ck
, buf
*b
)
729 /* --- Check the plaintext portions of the data --- */
731 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
732 trace_block(T_CRYPTO
, "crypto: challenge", hc_in
, HASHSZ
);
733 trace_block(T_CRYPTO
, "crypto: cookie", hc_out
, HASHSZ
);
734 if (ck
) trace(T_CRYPTO
, "crypto: check value = %s", mpstr(ck
));
736 if (memcmp(hc_out
, kx
->hc
, HASHSZ
) != 0) {
737 a_warn("incorrect cookie from `%s'", p_name(kx
->p
));
740 if ((kxc
= kxc_byhc(kx
, hc_in
)) == 0) {
741 a_warn("received reply for unknown challenge from `%s'", p_name(kx
->p
));
745 /* --- Maybe compute a reply for the challenge --- */
749 a_warn("unexpected switch request from `%s'", p_name(kx
->p
));
752 if ((r
= getreply(kx
, kxc
->c
, ck
)) == 0)
758 /* --- Decrypt the rest of the packet --- */
760 buf_init(&bb
, buf_o
, sizeof(buf_o
));
761 if (ks_decrypt(kxc
->ks
, ty
, b
, &bb
)) {
762 a_warn("failed to decrypt reply from `%s'", p_name(kx
->p
));
765 buf_init(b
, BBASE(&bb
), BLEN(&bb
));
766 if ((r
= buf_getmp(b
)) == 0) {
767 a_warn("invalid reply packet from `%s'", p_name(kx
->p
));
770 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
771 trace(T_CRYPTO
, "crypto: reply = %s", mpstr(r
));
773 if (!mp_eq(r
, kx
->rx
)) {
774 a_warn("incorrect reply from `%s'", p_name(kx
->p
));
788 /* --- @commit@ --- *
790 * Arguments: @keyexch *kx@ = pointer to key exchange context
791 * @kxchal *kxc@ = pointer to challenge to commit to
795 * Use: Commits to a particular challenge as being the `right' one,
796 * since a reply has arrived for it.
799 static void commit(keyexch
*kx
, kxchal
*kxc
)
803 for (i
= 0; i
< kx
->nr
; i
++) {
805 kxc_destroy(kx
->r
[i
]);
810 ksl_link(kx
->ks
, kxc
->ks
);
813 /* --- @doreply@ --- *
815 * Arguments: @keyexch *kx@ = pointer to key exchange context
816 * @buf *b@ = buffer containing packet
818 * Returns: Zero if OK, nonzero if the packet was rejected.
820 * Use: Handles a reply packet. This doesn't handle the various
821 * switch packets: they're rather too different.
824 static int doreply(keyexch
*kx
, buf
*b
)
826 const octet
*hc_in
, *hc_out
;
830 if (kx
->s
!= KXS_CHAL
&& kx
->s
!= KXS_COMMIT
) {
831 a_warn("unexpected reply from `%s'", p_name(kx
->p
));
834 if ((hc_in
= buf_get(b
, HASHSZ
)) == 0 ||
835 (hc_out
= buf_get(b
, HASHSZ
)) == 0 ||
836 (ck
= buf_getmp(b
)) == 0) {
837 a_warn("invalid reply packet from `%s'", p_name(kx
->p
));
840 if ((kxc
= matchreply(kx
, MSG_KEYEXCH
| KX_REPLY
,
841 hc_in
, hc_out
, ck
, b
)) == 0)
844 a_warn("invalid reply packet from `%s'", p_name(kx
->p
));
847 if (kx
->s
== KXS_CHAL
) {
859 /* --- @doswitch@ --- *
861 * Arguments: @keyexch *kx@ = pointer to key exchange block
862 * @buf *b@ = pointer to buffer containing packet
864 * Returns: Zero if OK, nonzero if the packet was rejected.
866 * Use: Handles a reply with a switch request bolted onto it.
869 static int doswitch(keyexch
*kx
, buf
*b
)
871 const octet
*hc_in
, *hc_out
, *hswrq
;
874 if ((hc_in
= buf_get(b
, HASHSZ
)) == 0 ||
875 (hc_out
= buf_get(b
, HASHSZ
)) == 0) {
876 a_warn("invalid switch request from `%s'", p_name(kx
->p
));
879 if ((kxc
= matchreply(kx
, MSG_KEYEXCH
| KX_SWITCH
,
880 hc_in
, hc_out
, 0, b
)) == 0)
882 if ((hswrq
= buf_get(b
, HASHSZ
)) == 0 || BLEFT(b
)) {
883 a_warn("invalid switch request from `%s'", p_name(kx
->p
));
886 IF_TRACING(T_KEYEXCH
, {
887 trace_block(T_CRYPTO
, "crypto: switch request hash", hswrq
, HASHSZ
);
889 if (memcmp(hswrq
, kxc
->hswrq_in
, HASHSZ
) != 0) {
890 a_warn("incorrect switch request hash from `%s'", p_name(kx
->p
));
897 ks_activate(kxc
->ks
);
898 settimer(kx
, ks_tregen(kxc
->ks
));
909 /* --- @doswitchok@ --- *
911 * Arguments: @keyexch *kx@ = pointer to key exchange block
912 * @buf *b@ = pointer to buffer containing packet
914 * Returns: Zero if OK, nonzero if the packet was rejected.
916 * Use: Handles a reply with a switch request bolted onto it.
919 static int doswitchok(keyexch
*kx
, buf
*b
)
925 if (kx
->s
< KXS_COMMIT
) {
926 a_warn("unexpected switch confirmation from `%s'", p_name(kx
->p
));
930 buf_init(&bb
, buf_o
, sizeof(buf_o
));
931 if (ks_decrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCHOK
, b
, &bb
)) {
932 a_warn("failed to decrypt switch confirmation from `%s'", p_name(kx
->p
));
935 buf_init(b
, BBASE(&bb
), BLEN(&bb
));
936 if ((hswok
= buf_get(b
, HASHSZ
)) == 0 || BLEFT(b
)) {
937 a_warn("invalid switch confirmation from `%s'", p_name(kx
->p
));
940 IF_TRACING(T_KEYEXCH
, {
941 trace_block(T_CRYPTO
, "crypto: switch confirmation hash", hswok
, HASHSZ
);
943 if (memcmp(hswok
, kxc
->hswok_in
, HASHSZ
) != 0) {
944 a_warn("incorrect switch confirmation hash from `%s'", p_name(kx
->p
));
947 if (kx
->s
< KXS_SWITCH
) {
948 ks_activate(kxc
->ks
);
949 settimer(kx
, ks_tregen(kxc
->ks
));
958 /*----- Main code ---------------------------------------------------------*/
962 * Arguments: @keyexch *kx@ = pointer to key exchange context
966 * Use: Stops a key exchange dead in its tracks. Throws away all of
967 * the context information. The context is left in an
968 * inconsistent state. The only functions which understand this
969 * state are @kx_free@ and @kx_init@ (which cause it internally
970 * it), and @start@ (which expects it to be the prevailing
974 static void stop(keyexch
*kx
)
978 if (kx
->f
& KXF_DEAD
)
981 if (kx
->f
& KXF_TIMER
)
983 for (i
= 0; i
< kx
->nr
; i
++)
984 kxc_destroy(kx
->r
[i
]);
995 * Arguments: @keyexch *kx@ = pointer to key exchange context
996 * @time_t now@ = the current time
1000 * Use: Starts a new key exchange with the peer. The context must be
1001 * in the bizarre state left by @stop@ or @kx_init@.
1004 static void start(keyexch
*kx
, time_t now
)
1008 assert(kx
->f
& KXF_DEAD
);
1012 kx
->alpha
= mprand_range(MP_NEW
, kpriv
.dp
.q
, &rand_global
, 0);
1013 kx
->c
= mpmont_exp(&mg
, MP_NEW
, kpriv
.dp
.g
, kx
->alpha
);
1014 kx
->rx
= mpmont_exp(&mg
, MP_NEW
, kx
->kpub
.y
, kx
->alpha
);
1016 kx
->t_valid
= now
+ T_VALID
;
1019 HASH_STRING(&h
, "tripe-cookie");
1021 HASH_DONE(&h
, kx
->hc
);
1023 IF_TRACING(T_KEYEXCH
, {
1024 trace(T_KEYEXCH
, "keyexch: creating new challenge");
1025 IF_TRACING(T_CRYPTO
, {
1026 trace(T_CRYPTO
, "crypto: secret = %s", mpstr(kx
->alpha
));
1027 trace(T_CRYPTO
, "crypto: challenge = %s", mpstr(kx
->c
));
1028 trace(T_CRYPTO
, "crypto: expected response = %s", mpstr(kx
->rx
));
1029 trace_block(T_CRYPTO
, "crypto: challenge cookie", kx
->hc
, HASHSZ
);
1034 /* --- @checkpub@ --- *
1036 * Arguments: @keyexch *kx@ = pointer to key exchange context
1038 * Returns: Zero if OK, nonzero if the peer's public key has expired.
1040 * Use: Deactivates the key-exchange until the peer acquires a new
1044 static int checkpub(keyexch
*kx
)
1047 if (kx
->f
& KXF_DEAD
)
1050 if (KEY_EXPIRED(now
, kx
->texp_kpub
)) {
1052 a_warn("public key for `%s' has expired", p_name(kx
->p
));
1053 dh_pubfree(&kx
->kpub
);
1054 kx
->f
&= ~KXF_PUBKEY
;
1060 /* --- @kx_start@ --- *
1062 * Arguments: @keyexch *kx@ = pointer to key exchange context
1066 * Use: Stimulates a key exchange. If a key exchage is in progress,
1067 * a new challenge is sent (unless the quiet timer forbids
1068 * this); if no exchange is in progress, one is commenced.
1071 void kx_start(keyexch
*kx
)
1073 time_t now
= time(0);
1077 if (!ISVALID(kx
, now
)) {
1084 /* --- @kx_message@ --- *
1086 * Arguments: @keyexch *kx@ = pointer to key exchange context
1087 * @unsigned msg@ = the message code
1088 * @buf *b@ = pointer to buffer containing the packet
1092 * Use: Reads a packet containing key exchange messages and handles
1096 void kx_message(keyexch
*kx
, unsigned msg
, buf
*b
)
1098 time_t now
= time(0);
1099 stats
*st
= p_stats(kx
->p
);
1104 static const char *const pkname
[] = {
1105 "prechallenge", "cookie", "challenge",
1106 "reply", "switch request", "switch confirmation"
1113 if (!ISVALID(kx
, now
)) {
1118 T( trace(T_KEYEXCH
, "keyexch: processing %s packet from `%s'",
1119 msg
< KX_NMSG ? pkname
[msg
] : "unknown", p_name(kx
->p
)); )
1125 rc
= dochallenge(kx
, msg
, b
);
1128 rc
= doreply(kx
, b
);
1131 rc
= doswitch(kx
, b
);
1134 rc
= doswitchok(kx
, b
);
1137 a_warn("unexpected key exchange message type %u from `%p'",
1151 /* --- @kx_free@ --- *
1153 * Arguments: @keyexch *kx@ = pointer to key exchange context
1157 * Use: Frees everything in a key exchange context.
1160 void kx_free(keyexch
*kx
)
1163 if (kx
->f
& KXF_PUBKEY
)
1164 dh_pubfree(&kx
->kpub
);
1167 /* --- @kx_newkeys@ --- *
1169 * Arguments: @keyexch *kx@ = pointer to key exchange context
1173 * Use: Informs the key exchange module that its keys may have
1174 * changed. If fetching the new keys fails, the peer will be
1175 * destroyed, we log messages and struggle along with the old
1179 void kx_newkeys(keyexch
*kx
)
1183 if (km_getpubkey(p_name(kx
->p
), &dp
, &kx
->texp_kpub
))
1185 if (kx
->f
& KXF_PUBKEY
)
1186 dh_pubfree(&kx
->kpub
);
1188 kx
->f
|= KXF_PUBKEY
;
1189 if ((kx
->f
& KXF_DEAD
) || kx
->s
!= KXS_SWITCH
) {
1190 T( trace(T_KEYEXCH
, "keyexch: restarting key negotiation with `%s'",
1198 /* --- @kx_init@ --- *
1200 * Arguments: @keyexch *kx@ = pointer to key exchange context
1201 * @peer *p@ = pointer to peer context
1202 * @keyset **ks@ = pointer to keyset list
1204 * Returns: Zero if OK, nonzero if it failed.
1206 * Use: Initializes a key exchange module. The module currently
1207 * contains no keys, and will attempt to initiate a key
1211 int kx_init(keyexch
*kx
, peer
*p
, keyset
**ks
)
1215 if (km_getpubkey(p_name(p
), &kx
->kpub
, &kx
->texp_kpub
))
1217 kx
->f
= KXF_DEAD
| KXF_PUBKEY
;
1223 /*----- That's all, folks -------------------------------------------------*/