xref: /freebsd/crypto/openssh/kex.c (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
1 /* $OpenBSD: kex.c,v 1.91 2013/05/17 00:13:13 djm Exp $ */
2 /* $FreeBSD$ */
3 /*
4  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include "includes.h"
28 
29 #include <sys/param.h>
30 
31 #include <signal.h>
32 #include <stdarg.h>
33 #include <stdio.h>
34 #include <stdlib.h>
35 #include <string.h>
36 
37 #include <openssl/crypto.h>
38 
39 #include "xmalloc.h"
40 #include "ssh2.h"
41 #include "buffer.h"
42 #include "packet.h"
43 #include "compat.h"
44 #include "cipher.h"
45 #include "key.h"
46 #include "kex.h"
47 #include "log.h"
48 #include "mac.h"
49 #include "match.h"
50 #include "dispatch.h"
51 #include "monitor.h"
52 #include "roaming.h"
53 
54 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
55 # if defined(HAVE_EVP_SHA256)
56 # define evp_ssh_sha256 EVP_sha256
57 # else
58 extern const EVP_MD *evp_ssh_sha256(void);
59 # endif
60 #endif
61 
62 /* prototype */
63 static void kex_kexinit_finish(Kex *);
64 static void kex_choose_conf(Kex *);
65 
66 struct kexalg {
67 	char *name;
68 	int type;
69 	int ec_nid;
70 	const EVP_MD *(*mdfunc)(void);
71 };
72 static const struct kexalg kexalgs[] = {
73 	{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, EVP_sha1 },
74 	{ KEX_DH14, KEX_DH_GRP14_SHA1, 0, EVP_sha1 },
75 	{ KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, EVP_sha1 },
76 #ifdef HAVE_EVP_SHA256
77 	{ KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, EVP_sha256 },
78 #endif
79 #ifdef OPENSSL_HAS_ECC
80 	{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, NID_X9_62_prime256v1, EVP_sha256 },
81 	{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, EVP_sha384 },
82 	{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, EVP_sha512 },
83 #endif
84 	{ NULL, -1, -1, NULL},
85 };
86 
87 char *
88 kex_alg_list(void)
89 {
90 	char *ret = NULL;
91 	size_t nlen, rlen = 0;
92 	const struct kexalg *k;
93 
94 	for (k = kexalgs; k->name != NULL; k++) {
95 		if (ret != NULL)
96 			ret[rlen++] = '\n';
97 		nlen = strlen(k->name);
98 		ret = xrealloc(ret, 1, rlen + nlen + 2);
99 		memcpy(ret + rlen, k->name, nlen + 1);
100 		rlen += nlen;
101 	}
102 	return ret;
103 }
104 
105 static const struct kexalg *
106 kex_alg_by_name(const char *name)
107 {
108 	const struct kexalg *k;
109 
110 	for (k = kexalgs; k->name != NULL; k++) {
111 		if (strcmp(k->name, name) == 0)
112 			return k;
113 	}
114 	return NULL;
115 }
116 
117 /* Validate KEX method name list */
118 int
119 kex_names_valid(const char *names)
120 {
121 	char *s, *cp, *p;
122 
123 	if (names == NULL || strcmp(names, "") == 0)
124 		return 0;
125 	s = cp = xstrdup(names);
126 	for ((p = strsep(&cp, ",")); p && *p != '\0';
127 	    (p = strsep(&cp, ","))) {
128 		if (kex_alg_by_name(p) == NULL) {
129 			error("Unsupported KEX algorithm \"%.100s\"", p);
130 			free(s);
131 			return 0;
132 		}
133 	}
134 	debug3("kex names ok: [%s]", names);
135 	free(s);
136 	return 1;
137 }
138 
139 /* put algorithm proposal into buffer. */
140 #ifndef NONE_CIPHER_ENABLED
141 static void
142 #else
143 /* Also used in sshconnect2.c. */
144 void
145 #endif
146 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
147 {
148 	u_int i;
149 
150 	buffer_clear(b);
151 	/*
152 	 * add a dummy cookie, the cookie will be overwritten by
153 	 * kex_send_kexinit(), each time a kexinit is set
154 	 */
155 	for (i = 0; i < KEX_COOKIE_LEN; i++)
156 		buffer_put_char(b, 0);
157 	for (i = 0; i < PROPOSAL_MAX; i++)
158 		buffer_put_cstring(b, proposal[i]);
159 	buffer_put_char(b, 0);			/* first_kex_packet_follows */
160 	buffer_put_int(b, 0);			/* uint32 reserved */
161 }
162 
163 /* parse buffer and return algorithm proposal */
164 static char **
165 kex_buf2prop(Buffer *raw, int *first_kex_follows)
166 {
167 	Buffer b;
168 	u_int i;
169 	char **proposal;
170 
171 	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
172 
173 	buffer_init(&b);
174 	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
175 	/* skip cookie */
176 	for (i = 0; i < KEX_COOKIE_LEN; i++)
177 		buffer_get_char(&b);
178 	/* extract kex init proposal strings */
179 	for (i = 0; i < PROPOSAL_MAX; i++) {
180 		proposal[i] = buffer_get_cstring(&b,NULL);
181 		debug2("kex_parse_kexinit: %s", proposal[i]);
182 	}
183 	/* first kex follows / reserved */
184 	i = buffer_get_char(&b);
185 	if (first_kex_follows != NULL)
186 		*first_kex_follows = i;
187 	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
188 	i = buffer_get_int(&b);
189 	debug2("kex_parse_kexinit: reserved %u ", i);
190 	buffer_free(&b);
191 	return proposal;
192 }
193 
194 static void
195 kex_prop_free(char **proposal)
196 {
197 	u_int i;
198 
199 	for (i = 0; i < PROPOSAL_MAX; i++)
200 		free(proposal[i]);
201 	free(proposal);
202 }
203 
204 /* ARGSUSED */
205 static void
206 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
207 {
208 	error("Hm, kex protocol error: type %d seq %u", type, seq);
209 }
210 
211 static void
212 kex_reset_dispatch(void)
213 {
214 	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
215 	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
216 	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
217 }
218 
219 void
220 kex_finish(Kex *kex)
221 {
222 	kex_reset_dispatch();
223 
224 	packet_start(SSH2_MSG_NEWKEYS);
225 	packet_send();
226 	/* packet_write_wait(); */
227 	debug("SSH2_MSG_NEWKEYS sent");
228 
229 	debug("expecting SSH2_MSG_NEWKEYS");
230 	packet_read_expect(SSH2_MSG_NEWKEYS);
231 	packet_check_eom();
232 	debug("SSH2_MSG_NEWKEYS received");
233 
234 	kex->done = 1;
235 	buffer_clear(&kex->peer);
236 	/* buffer_clear(&kex->my); */
237 	kex->flags &= ~KEX_INIT_SENT;
238 	free(kex->name);
239 	kex->name = NULL;
240 }
241 
242 void
243 kex_send_kexinit(Kex *kex)
244 {
245 	u_int32_t rnd = 0;
246 	u_char *cookie;
247 	u_int i;
248 
249 	if (kex == NULL) {
250 		error("kex_send_kexinit: no kex, cannot rekey");
251 		return;
252 	}
253 	if (kex->flags & KEX_INIT_SENT) {
254 		debug("KEX_INIT_SENT");
255 		return;
256 	}
257 	kex->done = 0;
258 
259 	/* generate a random cookie */
260 	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
261 		fatal("kex_send_kexinit: kex proposal too short");
262 	cookie = buffer_ptr(&kex->my);
263 	for (i = 0; i < KEX_COOKIE_LEN; i++) {
264 		if (i % 4 == 0)
265 			rnd = arc4random();
266 		cookie[i] = rnd;
267 		rnd >>= 8;
268 	}
269 	packet_start(SSH2_MSG_KEXINIT);
270 	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
271 	packet_send();
272 	debug("SSH2_MSG_KEXINIT sent");
273 	kex->flags |= KEX_INIT_SENT;
274 }
275 
276 /* ARGSUSED */
277 void
278 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
279 {
280 	char *ptr;
281 	u_int i, dlen;
282 	Kex *kex = (Kex *)ctxt;
283 
284 	debug("SSH2_MSG_KEXINIT received");
285 	if (kex == NULL)
286 		fatal("kex_input_kexinit: no kex, cannot rekey");
287 
288 	ptr = packet_get_raw(&dlen);
289 	buffer_append(&kex->peer, ptr, dlen);
290 
291 	/* discard packet */
292 	for (i = 0; i < KEX_COOKIE_LEN; i++)
293 		packet_get_char();
294 	for (i = 0; i < PROPOSAL_MAX; i++)
295 		free(packet_get_string(NULL));
296 	/*
297 	 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
298 	 * KEX method has the server move first, but a server might be using
299 	 * a custom method or one that we otherwise don't support. We should
300 	 * be prepared to remember first_kex_follows here so we can eat a
301 	 * packet later.
302 	 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
303 	 * for cases where the server *doesn't* go first. I guess we should
304 	 * ignore it when it is set for these cases, which is what we do now.
305 	 */
306 	(void) packet_get_char();	/* first_kex_follows */
307 	(void) packet_get_int();	/* reserved */
308 	packet_check_eom();
309 
310 	kex_kexinit_finish(kex);
311 }
312 
313 Kex *
314 kex_setup(char *proposal[PROPOSAL_MAX])
315 {
316 	Kex *kex;
317 
318 	kex = xcalloc(1, sizeof(*kex));
319 	buffer_init(&kex->peer);
320 	buffer_init(&kex->my);
321 	kex_prop2buf(&kex->my, proposal);
322 	kex->done = 0;
323 
324 	kex_send_kexinit(kex);					/* we start */
325 	kex_reset_dispatch();
326 
327 	return kex;
328 }
329 
330 static void
331 kex_kexinit_finish(Kex *kex)
332 {
333 	if (!(kex->flags & KEX_INIT_SENT))
334 		kex_send_kexinit(kex);
335 
336 	kex_choose_conf(kex);
337 
338 	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
339 	    kex->kex[kex->kex_type] != NULL) {
340 		(kex->kex[kex->kex_type])(kex);
341 	} else {
342 		fatal("Unsupported key exchange %d", kex->kex_type);
343 	}
344 }
345 
346 static void
347 choose_enc(Enc *enc, char *client, char *server)
348 {
349 	char *name = match_list(client, server, NULL);
350 	if (name == NULL)
351 		fatal("no matching cipher found: client %s server %s",
352 		    client, server);
353 	if ((enc->cipher = cipher_by_name(name)) == NULL)
354 		fatal("matching cipher is not supported: %s", name);
355 	enc->name = name;
356 	enc->enabled = 0;
357 	enc->iv = NULL;
358 	enc->iv_len = cipher_ivlen(enc->cipher);
359 	enc->key = NULL;
360 	enc->key_len = cipher_keylen(enc->cipher);
361 	enc->block_size = cipher_blocksize(enc->cipher);
362 }
363 
364 static void
365 choose_mac(Mac *mac, char *client, char *server)
366 {
367 	char *name = match_list(client, server, NULL);
368 	if (name == NULL)
369 		fatal("no matching mac found: client %s server %s",
370 		    client, server);
371 	if (mac_setup(mac, name) < 0)
372 		fatal("unsupported mac %s", name);
373 	/* truncate the key */
374 	if (datafellows & SSH_BUG_HMAC)
375 		mac->key_len = 16;
376 	mac->name = name;
377 	mac->key = NULL;
378 	mac->enabled = 0;
379 }
380 
381 static void
382 choose_comp(Comp *comp, char *client, char *server)
383 {
384 	char *name = match_list(client, server, NULL);
385 	if (name == NULL)
386 		fatal("no matching comp found: client %s server %s", client, server);
387 	if (strcmp(name, "zlib@openssh.com") == 0) {
388 		comp->type = COMP_DELAYED;
389 	} else if (strcmp(name, "zlib") == 0) {
390 		comp->type = COMP_ZLIB;
391 	} else if (strcmp(name, "none") == 0) {
392 		comp->type = COMP_NONE;
393 	} else {
394 		fatal("unsupported comp %s", name);
395 	}
396 	comp->name = name;
397 }
398 
399 static void
400 choose_kex(Kex *k, char *client, char *server)
401 {
402 	const struct kexalg *kexalg;
403 
404 	k->name = match_list(client, server, NULL);
405 	if (k->name == NULL)
406 		fatal("Unable to negotiate a key exchange method");
407 	if ((kexalg = kex_alg_by_name(k->name)) == NULL)
408 		fatal("unsupported kex alg %s", k->name);
409 	k->kex_type = kexalg->type;
410 	k->evp_md = kexalg->mdfunc();
411 	k->ec_nid = kexalg->ec_nid;
412 }
413 
414 static void
415 choose_hostkeyalg(Kex *k, char *client, char *server)
416 {
417 	char *hostkeyalg = match_list(client, server, NULL);
418 	if (hostkeyalg == NULL)
419 		fatal("no hostkey alg");
420 	k->hostkey_type = key_type_from_name(hostkeyalg);
421 	if (k->hostkey_type == KEY_UNSPEC)
422 		fatal("bad hostkey alg '%s'", hostkeyalg);
423 	free(hostkeyalg);
424 }
425 
426 static int
427 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
428 {
429 	static int check[] = {
430 		PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
431 	};
432 	int *idx;
433 	char *p;
434 
435 	for (idx = &check[0]; *idx != -1; idx++) {
436 		if ((p = strchr(my[*idx], ',')) != NULL)
437 			*p = '\0';
438 		if ((p = strchr(peer[*idx], ',')) != NULL)
439 			*p = '\0';
440 		if (strcmp(my[*idx], peer[*idx]) != 0) {
441 			debug2("proposal mismatch: my %s peer %s",
442 			    my[*idx], peer[*idx]);
443 			return (0);
444 		}
445 	}
446 	debug2("proposals match");
447 	return (1);
448 }
449 
450 static void
451 kex_choose_conf(Kex *kex)
452 {
453 	Newkeys *newkeys;
454 	char **my, **peer;
455 	char **cprop, **sprop;
456 	int nenc, nmac, ncomp;
457 	u_int mode, ctos, need, authlen;
458 	int first_kex_follows, type;
459 #ifdef	NONE_CIPHER_ENABLED
460 	int auth_flag;
461 #endif
462 
463 	my   = kex_buf2prop(&kex->my, NULL);
464 	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
465 
466 	if (kex->server) {
467 		cprop=peer;
468 		sprop=my;
469 	} else {
470 		cprop=my;
471 		sprop=peer;
472 	}
473 
474 	/* Check whether server offers roaming */
475 	if (!kex->server) {
476 		char *roaming;
477 		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
478 		if (roaming) {
479 			kex->roaming = 1;
480 			free(roaming);
481 		}
482 	}
483 
484 	/* Algorithm Negotiation */
485 #ifdef	NONE_CIPHER_ENABLED
486 	auth_flag = packet_get_authentication_state();
487 	debug ("AUTH STATE is %d", auth_flag);
488 #endif
489 	for (mode = 0; mode < MODE_MAX; mode++) {
490 		newkeys = xcalloc(1, sizeof(*newkeys));
491 		kex->newkeys[mode] = newkeys;
492 		ctos = (!kex->server && mode == MODE_OUT) ||
493 		    (kex->server && mode == MODE_IN);
494 		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
495 		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
496 		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
497 		choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc]);
498 		/* ignore mac for authenticated encryption */
499 		authlen = cipher_authlen(newkeys->enc.cipher);
500 		if (authlen == 0)
501 			choose_mac(&newkeys->mac, cprop[nmac], sprop[nmac]);
502 		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
503 #ifdef	NONE_CIPHER_ENABLED
504 		debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
505 		if (strcmp(newkeys->enc.name, "none") == 0) {
506 			debug("Requesting NONE. Authflag is %d", auth_flag);
507 			if (auth_flag == 1)
508 				debug("None requested post authentication.");
509 			else
510 				fatal("Pre-authentication none cipher requests "
511 				    "are not allowed.");
512 		}
513 #endif
514 		debug("kex: %s %s %s %s",
515 		    ctos ? "client->server" : "server->client",
516 		    newkeys->enc.name,
517 		    authlen == 0 ? newkeys->mac.name : "<implicit>",
518 		    newkeys->comp.name);
519 	}
520 	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
521 	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
522 	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
523 	need = 0;
524 	for (mode = 0; mode < MODE_MAX; mode++) {
525 		newkeys = kex->newkeys[mode];
526 		if (need < newkeys->enc.key_len)
527 			need = newkeys->enc.key_len;
528 		if (need < newkeys->enc.block_size)
529 			need = newkeys->enc.block_size;
530 		if (need < newkeys->enc.iv_len)
531 			need = newkeys->enc.iv_len;
532 		if (need < newkeys->mac.key_len)
533 			need = newkeys->mac.key_len;
534 	}
535 	/* XXX need runden? */
536 	kex->we_need = need;
537 
538 	/* ignore the next message if the proposals do not match */
539 	if (first_kex_follows && !proposals_match(my, peer) &&
540 	    !(datafellows & SSH_BUG_FIRSTKEX)) {
541 		type = packet_read();
542 		debug2("skipping next packet (type %u)", type);
543 	}
544 
545 	kex_prop_free(my);
546 	kex_prop_free(peer);
547 }
548 
549 static u_char *
550 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
551     BIGNUM *shared_secret)
552 {
553 	Buffer b;
554 	EVP_MD_CTX md;
555 	char c = id;
556 	u_int have;
557 	int mdsz;
558 	u_char *digest;
559 
560 	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
561 		fatal("bad kex md size %d", mdsz);
562 	digest = xmalloc(roundup(need, mdsz));
563 
564 	buffer_init(&b);
565 	buffer_put_bignum2(&b, shared_secret);
566 
567 	/* K1 = HASH(K || H || "A" || session_id) */
568 	EVP_DigestInit(&md, kex->evp_md);
569 	if (!(datafellows & SSH_BUG_DERIVEKEY))
570 		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
571 	EVP_DigestUpdate(&md, hash, hashlen);
572 	EVP_DigestUpdate(&md, &c, 1);
573 	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
574 	EVP_DigestFinal(&md, digest, NULL);
575 
576 	/*
577 	 * expand key:
578 	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
579 	 * Key = K1 || K2 || ... || Kn
580 	 */
581 	for (have = mdsz; need > have; have += mdsz) {
582 		EVP_DigestInit(&md, kex->evp_md);
583 		if (!(datafellows & SSH_BUG_DERIVEKEY))
584 			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
585 		EVP_DigestUpdate(&md, hash, hashlen);
586 		EVP_DigestUpdate(&md, digest, have);
587 		EVP_DigestFinal(&md, digest + have, NULL);
588 	}
589 	buffer_free(&b);
590 #ifdef DEBUG_KEX
591 	fprintf(stderr, "key '%c'== ", c);
592 	dump_digest("key", digest, need);
593 #endif
594 	return digest;
595 }
596 
597 Newkeys *current_keys[MODE_MAX];
598 
599 #define NKEYS	6
600 void
601 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
602 {
603 	u_char *keys[NKEYS];
604 	u_int i, mode, ctos;
605 
606 	for (i = 0; i < NKEYS; i++) {
607 		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
608 		    shared_secret);
609 	}
610 
611 	debug2("kex_derive_keys");
612 	for (mode = 0; mode < MODE_MAX; mode++) {
613 		current_keys[mode] = kex->newkeys[mode];
614 		kex->newkeys[mode] = NULL;
615 		ctos = (!kex->server && mode == MODE_OUT) ||
616 		    (kex->server && mode == MODE_IN);
617 		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
618 		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
619 		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
620 	}
621 }
622 
623 Newkeys *
624 kex_get_newkeys(int mode)
625 {
626 	Newkeys *ret;
627 
628 	ret = current_keys[mode];
629 	current_keys[mode] = NULL;
630 	return ret;
631 }
632 
633 void
634 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
635     u_int8_t cookie[8], u_int8_t id[16])
636 {
637 	const EVP_MD *evp_md = EVP_md5();
638 	EVP_MD_CTX md;
639 	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
640 	int len;
641 
642 	EVP_DigestInit(&md, evp_md);
643 
644 	len = BN_num_bytes(host_modulus);
645 	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
646 		fatal("%s: bad host modulus (len %d)", __func__, len);
647 	BN_bn2bin(host_modulus, nbuf);
648 	EVP_DigestUpdate(&md, nbuf, len);
649 
650 	len = BN_num_bytes(server_modulus);
651 	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
652 		fatal("%s: bad server modulus (len %d)", __func__, len);
653 	BN_bn2bin(server_modulus, nbuf);
654 	EVP_DigestUpdate(&md, nbuf, len);
655 
656 	EVP_DigestUpdate(&md, cookie, 8);
657 
658 	EVP_DigestFinal(&md, obuf, NULL);
659 	memcpy(id, obuf, 16);
660 
661 	memset(nbuf, 0, sizeof(nbuf));
662 	memset(obuf, 0, sizeof(obuf));
663 	memset(&md, 0, sizeof(md));
664 }
665 
666 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
667 void
668 dump_digest(char *msg, u_char *digest, int len)
669 {
670 	int i;
671 
672 	fprintf(stderr, "%s\n", msg);
673 	for (i = 0; i < len; i++) {
674 		fprintf(stderr, "%02x", digest[i]);
675 		if (i%32 == 31)
676 			fprintf(stderr, "\n");
677 		else if (i%8 == 7)
678 			fprintf(stderr, " ");
679 	}
680 	fprintf(stderr, "\n");
681 }
682 #endif
683