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 /*----- Tunable parameters ------------------------------------------------*/
80 #define T_VALID SEC(20) /* Challenge validity period */
81 #define T_RETRY SEC(10) /* Challenge retransmit interval */
83 #define VALIDP(kx, now) ((now) < (kx)->t_valid)
85 /*----- Static tables -----------------------------------------------------*/
87 static const char *const pkname
[] = {
88 "pre-challenge", "challenge", "reply", "switch-rq", "switch-ok"
91 /*----- Various utilities -------------------------------------------------*/
95 * Arguments: @ghash *h@ = pointer to hash context
96 * @ge *x@ = pointer to group element
100 * Use: Adds the hash of a group element to the context. Corrupts
104 static void hashge(ghash
*h
, ge
*x
)
107 buf_init(&b
, buf_t
, sizeof(buf_t
));
110 GH_HASH(h
, BBASE(&b
), BLEN(&b
));
113 /* --- @mpmask@ --- *
115 * Arguments: @buf *b@ = output buffer
116 * @mp *x@ = the plaintext integer
117 * @size_t n@ = the expected size of the plaintext
118 * @const octet *k@ = pointer to key material
119 * @size_t ksz@ = size of the key
121 * Returns: Pointer to the output.
123 * Use: Masks a multiprecision integer: returns %$x \xor H(k)$%, so
124 * it's a random oracle thing rather than an encryption thing.
127 static octet
*mpmask(buf
*b
, mp
*x
, size_t n
, const octet
*k
, size_t ksz
)
132 if ((p
= buf_get(b
, n
)) == 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
);
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
);
149 /* --- @mpunmask@ --- *
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
157 * Returns: The decrypted integer, or null.
159 * Use: Unmasks a multiprecision integer.
162 static mp
*mpunmask(mp
*d
, const octet
*p
, size_t n
,
163 const octet
*k
, size_t ksz
)
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
);
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
));
182 /* --- @hashcheck@ --- *
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
189 * Returns: Pointer to the hash value (in @buf_t@)
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.
201 static const octet
*hashcheck(ge
*kpub
, ge
*cc
, ge
*c
, ge
*y
)
203 ghash
*h
= GH_INIT(algs
.h
);
205 HASH_STRING(h
, "tripe-expected-reply");
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
);
223 /* --- @sendchallenge@ --- *
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
232 * Use: Writes a full challenge to the message buffer.
235 static void sendchallenge(keyexch
*kx
, buf
*b
, ge
*c
, const octet
*hc
)
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
);
245 * Arguments: @struct timeval *tv@ = the current time
246 * @void *v@ = pointer to key exchange context
250 * Use: Acts when the key exchange timer goes off.
253 static void timer(struct timeval
*tv
, void *v
)
257 T( trace(T_KEYEXCH
, "keyexch: timer has popped"); )
261 /* --- @settimer@ --- *
263 * Arguments: @keyexch *kx@ = pointer to key exchange context
264 * @time_t t@ = when to set the timer for
268 * Use: Sets the timer for the next key exchange attempt.
271 static void settimer(keyexch
*kx
, time_t t
)
274 if (kx
->f
& KXF_TIMER
)
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
);
731 T( trace(T_KEYEXCH
, "keyexch: sending prechallenge to `%s'",
733 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_PRECHAL
);
734 G_TOBUF(gg
, b
, kx
->c
);
737 T( trace(T_KEYEXCH
, "keyexch: sending switch request to `%s'",
740 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCH
);
741 buf_put(b
, kx
->hc
, algs
.hashsz
);
742 buf_put(b
, kxc
->hc
, algs
.hashsz
);
743 buf_init(&bb
, buf_i
, sizeof(buf_i
));
744 G_TORAW(gg
, &bb
, kxc
->r
);
745 buf_put(&bb
, kxc
->hswrq_out
, algs
.hashsz
);
747 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCH
, &bb
, b
);
750 T( trace(T_KEYEXCH
, "keyexch: sending switch confirmation to `%s'",
753 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCHOK
);
754 buf_init(&bb
, buf_i
, sizeof(buf_i
));
755 buf_put(&bb
, kxc
->hswok_out
, algs
.hashsz
);
757 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCHOK
, &bb
, b
);
765 st
->sz_kxout
+= BLEN(b
);
769 if (kx
->s
< KXS_SWITCH
)
770 settimer(kx
, time(0) + T_RETRY
);
773 /* --- @decryptrest@ --- *
775 * Arguments: @keyexch *kx@ = pointer to key exchange context
776 * @kxchal *kxc@ = pointer to challenge block
777 * @unsigned msg@ = type of incoming message
778 * @buf *b@ = encrypted remainder of the packet
780 * Returns: Zero if OK, nonzero on some kind of error.
782 * Use: Decrypts the remainder of the packet, and points @b@ at the
783 * recovered plaintext.
786 static int decryptrest(keyexch
*kx
, kxchal
*kxc
, unsigned msg
, buf
*b
)
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
);
795 if (!BOK(&bb
)) return (-1);
796 buf_init(b
, BBASE(&bb
), BLEN(&bb
));
800 /* --- @checkresponse@ --- *
802 * Arguments: @keyexch *kx@ = pointer to key exchange context
803 * @unsigned msg@ = type of incoming message
804 * @buf *b@ = decrypted remainder of the packet
806 * Returns: Zero if OK, nonzero on some kind of error.
808 * Use: Checks a reply or switch packet, ensuring that its response
812 static int checkresponse(keyexch
*kx
, unsigned msg
, buf
*b
)
814 ge
*r
= G_CREATE(gg
);
816 if (G_FROMRAW(gg
, b
, r
)) {
817 a_warn("KX", "?PEER", kx
->p
, "invalid", "%s", pkname
[msg
], A_END
);
820 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
821 trace(T_CRYPTO
, "crypto: reply = %s", gestr(gg
, r
));
823 if (!G_EQ(gg
, r
, kx
->rx
)) {
824 a_warn("KX", "?PEER", kx
->p
, "incorrect", "response", A_END
);
836 /* --- @commit@ --- *
838 * Arguments: @keyexch *kx@ = pointer to key exchange context
839 * @kxchal *kxc@ = pointer to challenge to commit to
843 * Use: Commits to a particular challenge as being the `right' one,
844 * since a reply has arrived for it.
847 static void commit(keyexch
*kx
, kxchal
*kxc
)
851 for (i
= 0; i
< kx
->nr
; i
++) {
853 kxc_destroy(kx
->r
[i
]);
858 ksl_link(kx
->ks
, kxc
->ks
);
861 /* --- @doreply@ --- *
863 * Arguments: @keyexch *kx@ = pointer to key exchange context
864 * @buf *b@ = buffer containing packet
866 * Returns: Zero if OK, nonzero if the packet was rejected.
868 * Use: Handles a reply packet. This doesn't handle the various
869 * switch packets: they're rather too different.
872 static int doreply(keyexch
*kx
, buf
*b
)
876 if (kx
->s
!= KXS_CHAL
&& kx
->s
!= KXS_COMMIT
) {
877 a_warn("KX", "?PEER", kx
->p
, "unexpected", "reply", A_END
);
880 if ((kxc
= respond(kx
, KX_REPLY
, b
)) == 0 ||
881 decryptrest(kx
, kxc
, KX_REPLY
, b
) ||
882 checkresponse(kx
, KX_REPLY
, b
))
885 a_warn("KX", "?PEER", kx
->p
, "invalid", "reply", A_END
);
888 if (kx
->s
== KXS_CHAL
) {
899 /* --- @kxfinish@ --- *
901 * Arguments: @keyexch *kx@ = pointer to key exchange block
905 * Use: Sets everything up following a successful key exchange.
908 static void kxfinish(keyexch
*kx
)
910 kxchal
*kxc
= kx
->r
[0];
911 ks_activate(kxc
->ks
);
912 settimer(kx
, ks_tregen(kxc
->ks
));
914 a_notify("KXDONE", "?PEER", kx
->p
, A_END
);
915 p_stats(kx
->p
)->t_kx
= time(0);
918 /* --- @doswitch@ --- *
920 * Arguments: @keyexch *kx@ = pointer to key exchange block
921 * @buf *b@ = pointer to buffer containing packet
923 * Returns: Zero if OK, nonzero if the packet was rejected.
925 * Use: Handles a reply with a switch request bolted onto it.
928 static int doswitch(keyexch
*kx
, buf
*b
)
930 const octet
*hc_in
, *hc_out
, *hswrq
;
933 if ((hc_in
= buf_get(b
, algs
.hashsz
)) == 0 ||
934 (hc_out
= buf_get(b
, algs
.hashsz
)) == 0) {
935 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-rq", A_END
);
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
);
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
);
947 if (decryptrest(kx
, kxc
, KX_SWITCH
, b
) ||
948 checkresponse(kx
, KX_SWITCH
, b
))
950 if ((hswrq
= buf_get(b
, algs
.hashsz
)) == 0 || BLEFT(b
)) {
951 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-rq", A_END
);
954 IF_TRACING(T_KEYEXCH
, {
955 trace_block(T_CRYPTO
, "crypto: switch request hash", hswrq
, algs
.hashsz
);
957 if (memcmp(hswrq
, kxc
->hswrq_in
, algs
.hashsz
) != 0) {
958 a_warn("KX", "?PEER", kx
->p
, "incorrect", "switch-rq", A_END
);
961 if (kx
->s
== KXS_CHAL
)
963 if (kx
->s
< KXS_SWITCH
)
972 /* --- @doswitchok@ --- *
974 * Arguments: @keyexch *kx@ = pointer to key exchange block
975 * @buf *b@ = pointer to buffer containing packet
977 * Returns: Zero if OK, nonzero if the packet was rejected.
979 * Use: Handles a reply with a switch request bolted onto it.
982 static int doswitchok(keyexch
*kx
, buf
*b
)
988 if (kx
->s
< KXS_COMMIT
) {
989 a_warn("KX", "?PEER", kx
->p
, "unexpected", "switch-ok", A_END
);
993 buf_init(&bb
, buf_o
, sizeof(buf_o
));
994 if (decryptrest(kx
, kxc
, KX_SWITCHOK
, b
))
996 if ((hswok
= buf_get(b
, algs
.hashsz
)) == 0 || BLEFT(b
)) {
997 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-ok", A_END
);
1000 IF_TRACING(T_KEYEXCH
, {
1001 trace_block(T_CRYPTO
, "crypto: switch confirmation hash",
1002 hswok
, algs
.hashsz
);
1004 if (memcmp(hswok
, kxc
->hswok_in
, algs
.hashsz
) != 0) {
1005 a_warn("KX", "?PEER", kx
->p
, "incorrect", "switch-ok", A_END
);
1008 if (kx
->s
< KXS_SWITCH
)
1016 /*----- Main code ---------------------------------------------------------*/
1020 * Arguments: @keyexch *kx@ = pointer to key exchange context
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
1032 static void stop(keyexch
*kx
)
1036 if (kx
->f
& KXF_DEAD
)
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
]);
1044 G_DESTROY(gg
, kx
->c
);
1045 G_DESTROY(gg
, kx
->rx
);
1048 kx
->f
&= ~KXF_TIMER
;
1051 /* --- @start@ --- *
1053 * Arguments: @keyexch *kx@ = pointer to key exchange context
1054 * @time_t now@ = the current time
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@.
1062 static void start(keyexch
*kx
, time_t now
)
1066 assert(kx
->f
& KXF_DEAD
);
1068 kx
->f
&= ~(KXF_DEAD
| KXF_CORK
);
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
);
1074 kx
->t_valid
= now
+ T_VALID
;
1076 h
= GH_INIT(algs
.h
);
1077 HASH_STRING(h
, "tripe-cookie");
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
));
1086 trace(T_CRYPTO
, "crypto: challenge = %s", gestr(gg
, kx
->c
));
1087 trace(T_CRYPTO
, "crypto: expected response = %s", gestr(gg
, kx
->rx
));
1088 trace_block(T_CRYPTO
, "crypto: challenge cookie", kx
->hc
, algs
.hashsz
);
1093 /* --- @checkpub@ --- *
1095 * Arguments: @keyexch *kx@ = pointer to key exchange context
1097 * Returns: Zero if OK, nonzero if the peer's public key has expired.
1099 * Use: Deactivates the key-exchange until the peer acquires a new
1103 static int checkpub(keyexch
*kx
)
1106 if (kx
->f
& KXF_DEAD
)
1109 if (KEY_EXPIRED(now
, kx
->texp_kpub
)) {
1111 a_warn("KX", "?PEER", kx
->p
, "public-key-expired", A_END
);
1112 G_COPY(gg
, kx
->kpub
, gg
->i
);
1113 kx
->f
&= ~KXF_PUBKEY
;
1119 /* --- @kx_start@ --- *
1121 * Arguments: @keyexch *kx@ = pointer to key exchange context
1122 * @int forcep@ = nonzero to ignore the quiet timer
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.
1131 void kx_start(keyexch
*kx
, int forcep
)
1133 time_t now
= time(0);
1137 if (forcep
|| !VALIDP(kx
, now
)) {
1140 a_notify("KXSTART", "?PEER", kx
->p
, A_END
);
1145 /* --- @kx_message@ --- *
1147 * Arguments: @keyexch *kx@ = pointer to key exchange context
1148 * @unsigned msg@ = the message code
1149 * @buf *b@ = pointer to buffer containing the packet
1153 * Use: Reads a packet containing key exchange messages and handles
1157 void kx_message(keyexch
*kx
, unsigned msg
, buf
*b
)
1159 time_t now
= time(0);
1160 stats
*st
= p_stats(kx
->p
);
1164 if (kx
->f
& KXF_CORK
) {
1166 settimer(kx
, now
+ T_RETRY
);
1167 a_notify("KXSTART", A_END
);
1173 if (!VALIDP(kx
, now
)) {
1177 T( trace(T_KEYEXCH
, "keyexch: processing %s packet from `%s'",
1178 msg
< KX_NMSG ? pkname
[msg
] : "unknown", p_name(kx
->p
)); )
1182 rc
= doprechallenge(kx
, b
);
1185 rc
= dochallenge(kx
, b
);
1188 rc
= doreply(kx
, b
);
1191 rc
= doswitch(kx
, b
);
1194 rc
= doswitchok(kx
, b
);
1197 a_warn("KX", "?PEER", kx
->p
, "unknown-message", "0x%02x", msg
, A_END
);
1210 /* --- @kx_free@ --- *
1212 * Arguments: @keyexch *kx@ = pointer to key exchange context
1216 * Use: Frees everything in a key exchange context.
1219 void kx_free(keyexch
*kx
)
1222 G_DESTROY(gg
, kx
->kpub
);
1225 /* --- @kx_newkeys@ --- *
1227 * Arguments: @keyexch *kx@ = pointer to key exchange context
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
1237 void kx_newkeys(keyexch
*kx
)
1239 if (km_getpubkey(p_tag(kx
->p
), kx
->kpub
, &kx
->texp_kpub
))
1241 kx
->f
|= KXF_PUBKEY
;
1242 if ((kx
->f
& KXF_DEAD
) || kx
->s
!= KXS_SWITCH
) {
1243 T( trace(T_KEYEXCH
, "keyexch: restarting key negotiation with `%s'",
1251 /* --- @kx_init@ --- *
1253 * Arguments: @keyexch *kx@ = pointer to key exchange context
1254 * @peer *p@ = pointer to peer context
1255 * @keyset **ks@ = pointer to keyset list
1256 * @unsigned f@ = various useful flags
1258 * Returns: Zero if OK, nonzero if it failed.
1260 * Use: Initializes a key exchange module. The module currently
1261 * contains no keys, and will attempt to initiate a key
1265 int kx_init(keyexch
*kx
, peer
*p
, keyset
**ks
, unsigned f
)
1269 kx
->kpub
= G_CREATE(gg
);
1270 if (km_getpubkey(p_tag(p
), kx
->kpub
, &kx
->texp_kpub
)) {
1271 G_DESTROY(gg
, kx
->kpub
);
1274 kx
->f
= KXF_DEAD
| KXF_PUBKEY
| f
;
1275 if (!(kx
->f
& KXF_CORK
)) {
1278 /* Don't notify here: the ADD message hasn't gone out yet. */
1283 /*----- That's all, folks -------------------------------------------------*/