xref: /freebsd/crypto/openssh/kex.c (revision f5f7c05209ca2c3748fd8b27c5e80ffad49120eb)
1 /* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 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 /* Validate KEX method name list */
67 int
68 kex_names_valid(const char *names)
69 {
70 	char *s, *cp, *p;
71 
72 	if (names == NULL || strcmp(names, "") == 0)
73 		return 0;
74 	s = cp = xstrdup(names);
75 	for ((p = strsep(&cp, ",")); p && *p != '\0';
76 	    (p = strsep(&cp, ","))) {
77 	    	if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
78 		    strcmp(p, KEX_DHGEX_SHA1) != 0 &&
79 		    strcmp(p, KEX_DH14) != 0 &&
80 		    strcmp(p, KEX_DH1) != 0 &&
81 		    (strncmp(p, KEX_ECDH_SHA2_STEM,
82 		    sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
83 		    kex_ecdh_name_to_nid(p) == -1)) {
84 			error("Unsupported KEX algorithm \"%.100s\"", p);
85 			xfree(s);
86 			return 0;
87 		}
88 	}
89 	debug3("kex names ok: [%s]", names);
90 	xfree(s);
91 	return 1;
92 }
93 
94 /* put algorithm proposal into buffer. */
95 #ifndef NONE_CIPHER_ENABLED
96 static void
97 #else
98 /* Also used in sshconnect2.c. */
99 void
100 #endif
101 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
102 {
103 	u_int i;
104 
105 	buffer_clear(b);
106 	/*
107 	 * add a dummy cookie, the cookie will be overwritten by
108 	 * kex_send_kexinit(), each time a kexinit is set
109 	 */
110 	for (i = 0; i < KEX_COOKIE_LEN; i++)
111 		buffer_put_char(b, 0);
112 	for (i = 0; i < PROPOSAL_MAX; i++)
113 		buffer_put_cstring(b, proposal[i]);
114 	buffer_put_char(b, 0);			/* first_kex_packet_follows */
115 	buffer_put_int(b, 0);			/* uint32 reserved */
116 }
117 
118 /* parse buffer and return algorithm proposal */
119 static char **
120 kex_buf2prop(Buffer *raw, int *first_kex_follows)
121 {
122 	Buffer b;
123 	u_int i;
124 	char **proposal;
125 
126 	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
127 
128 	buffer_init(&b);
129 	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
130 	/* skip cookie */
131 	for (i = 0; i < KEX_COOKIE_LEN; i++)
132 		buffer_get_char(&b);
133 	/* extract kex init proposal strings */
134 	for (i = 0; i < PROPOSAL_MAX; i++) {
135 		proposal[i] = buffer_get_cstring(&b,NULL);
136 		debug2("kex_parse_kexinit: %s", proposal[i]);
137 	}
138 	/* first kex follows / reserved */
139 	i = buffer_get_char(&b);
140 	if (first_kex_follows != NULL)
141 		*first_kex_follows = i;
142 	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
143 	i = buffer_get_int(&b);
144 	debug2("kex_parse_kexinit: reserved %u ", i);
145 	buffer_free(&b);
146 	return proposal;
147 }
148 
149 static void
150 kex_prop_free(char **proposal)
151 {
152 	u_int i;
153 
154 	for (i = 0; i < PROPOSAL_MAX; i++)
155 		xfree(proposal[i]);
156 	xfree(proposal);
157 }
158 
159 /* ARGSUSED */
160 static void
161 kex_protocol_error(int type, u_int32_t seq, void *ctxt)
162 {
163 	error("Hm, kex protocol error: type %d seq %u", type, seq);
164 }
165 
166 static void
167 kex_reset_dispatch(void)
168 {
169 	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
170 	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
171 	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
172 }
173 
174 void
175 kex_finish(Kex *kex)
176 {
177 	kex_reset_dispatch();
178 
179 	packet_start(SSH2_MSG_NEWKEYS);
180 	packet_send();
181 	/* packet_write_wait(); */
182 	debug("SSH2_MSG_NEWKEYS sent");
183 
184 	debug("expecting SSH2_MSG_NEWKEYS");
185 	packet_read_expect(SSH2_MSG_NEWKEYS);
186 	packet_check_eom();
187 	debug("SSH2_MSG_NEWKEYS received");
188 
189 	kex->done = 1;
190 	buffer_clear(&kex->peer);
191 	/* buffer_clear(&kex->my); */
192 	kex->flags &= ~KEX_INIT_SENT;
193 	xfree(kex->name);
194 	kex->name = NULL;
195 }
196 
197 void
198 kex_send_kexinit(Kex *kex)
199 {
200 	u_int32_t rnd = 0;
201 	u_char *cookie;
202 	u_int i;
203 
204 	if (kex == NULL) {
205 		error("kex_send_kexinit: no kex, cannot rekey");
206 		return;
207 	}
208 	if (kex->flags & KEX_INIT_SENT) {
209 		debug("KEX_INIT_SENT");
210 		return;
211 	}
212 	kex->done = 0;
213 
214 	/* generate a random cookie */
215 	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
216 		fatal("kex_send_kexinit: kex proposal too short");
217 	cookie = buffer_ptr(&kex->my);
218 	for (i = 0; i < KEX_COOKIE_LEN; i++) {
219 		if (i % 4 == 0)
220 			rnd = arc4random();
221 		cookie[i] = rnd;
222 		rnd >>= 8;
223 	}
224 	packet_start(SSH2_MSG_KEXINIT);
225 	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
226 	packet_send();
227 	debug("SSH2_MSG_KEXINIT sent");
228 	kex->flags |= KEX_INIT_SENT;
229 }
230 
231 /* ARGSUSED */
232 void
233 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
234 {
235 	char *ptr;
236 	u_int i, dlen;
237 	Kex *kex = (Kex *)ctxt;
238 
239 	debug("SSH2_MSG_KEXINIT received");
240 	if (kex == NULL)
241 		fatal("kex_input_kexinit: no kex, cannot rekey");
242 
243 	ptr = packet_get_raw(&dlen);
244 	buffer_append(&kex->peer, ptr, dlen);
245 
246 	/* discard packet */
247 	for (i = 0; i < KEX_COOKIE_LEN; i++)
248 		packet_get_char();
249 	for (i = 0; i < PROPOSAL_MAX; i++)
250 		xfree(packet_get_string(NULL));
251 	(void) packet_get_char();
252 	(void) packet_get_int();
253 	packet_check_eom();
254 
255 	kex_kexinit_finish(kex);
256 }
257 
258 Kex *
259 kex_setup(char *proposal[PROPOSAL_MAX])
260 {
261 	Kex *kex;
262 
263 	kex = xcalloc(1, sizeof(*kex));
264 	buffer_init(&kex->peer);
265 	buffer_init(&kex->my);
266 	kex_prop2buf(&kex->my, proposal);
267 	kex->done = 0;
268 
269 	kex_send_kexinit(kex);					/* we start */
270 	kex_reset_dispatch();
271 
272 	return kex;
273 }
274 
275 static void
276 kex_kexinit_finish(Kex *kex)
277 {
278 	if (!(kex->flags & KEX_INIT_SENT))
279 		kex_send_kexinit(kex);
280 
281 	kex_choose_conf(kex);
282 
283 	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
284 	    kex->kex[kex->kex_type] != NULL) {
285 		(kex->kex[kex->kex_type])(kex);
286 	} else {
287 		fatal("Unsupported key exchange %d", kex->kex_type);
288 	}
289 }
290 
291 static void
292 choose_enc(Enc *enc, char *client, char *server)
293 {
294 	char *name = match_list(client, server, NULL);
295 	if (name == NULL)
296 		fatal("no matching cipher found: client %s server %s",
297 		    client, server);
298 	if ((enc->cipher = cipher_by_name(name)) == NULL)
299 		fatal("matching cipher is not supported: %s", name);
300 	enc->name = name;
301 	enc->enabled = 0;
302 	enc->iv = NULL;
303 	enc->key = NULL;
304 	enc->key_len = cipher_keylen(enc->cipher);
305 	enc->block_size = cipher_blocksize(enc->cipher);
306 }
307 
308 static void
309 choose_mac(Mac *mac, char *client, char *server)
310 {
311 	char *name = match_list(client, server, NULL);
312 	if (name == NULL)
313 		fatal("no matching mac found: client %s server %s",
314 		    client, server);
315 	if (mac_setup(mac, name) < 0)
316 		fatal("unsupported mac %s", name);
317 	/* truncate the key */
318 	if (datafellows & SSH_BUG_HMAC)
319 		mac->key_len = 16;
320 	mac->name = name;
321 	mac->key = NULL;
322 	mac->enabled = 0;
323 }
324 
325 static void
326 choose_comp(Comp *comp, char *client, char *server)
327 {
328 	char *name = match_list(client, server, NULL);
329 	if (name == NULL)
330 		fatal("no matching comp found: client %s server %s", client, server);
331 	if (strcmp(name, "zlib@openssh.com") == 0) {
332 		comp->type = COMP_DELAYED;
333 	} else if (strcmp(name, "zlib") == 0) {
334 		comp->type = COMP_ZLIB;
335 	} else if (strcmp(name, "none") == 0) {
336 		comp->type = COMP_NONE;
337 	} else {
338 		fatal("unsupported comp %s", name);
339 	}
340 	comp->name = name;
341 }
342 
343 static void
344 choose_kex(Kex *k, char *client, char *server)
345 {
346 	k->name = match_list(client, server, NULL);
347 	if (k->name == NULL)
348 		fatal("Unable to negotiate a key exchange method");
349 	if (strcmp(k->name, KEX_DH1) == 0) {
350 		k->kex_type = KEX_DH_GRP1_SHA1;
351 		k->evp_md = EVP_sha1();
352 	} else if (strcmp(k->name, KEX_DH14) == 0) {
353 		k->kex_type = KEX_DH_GRP14_SHA1;
354 		k->evp_md = EVP_sha1();
355 	} else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
356 		k->kex_type = KEX_DH_GEX_SHA1;
357 		k->evp_md = EVP_sha1();
358 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
359 	} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
360 		k->kex_type = KEX_DH_GEX_SHA256;
361 		k->evp_md = evp_ssh_sha256();
362 	} else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
363 	    sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
364  		k->kex_type = KEX_ECDH_SHA2;
365 		k->evp_md = kex_ecdh_name_to_evpmd(k->name);
366 #endif
367 	} else
368 		fatal("bad kex alg %s", k->name);
369 }
370 
371 static void
372 choose_hostkeyalg(Kex *k, char *client, char *server)
373 {
374 	char *hostkeyalg = match_list(client, server, NULL);
375 	if (hostkeyalg == NULL)
376 		fatal("no hostkey alg");
377 	k->hostkey_type = key_type_from_name(hostkeyalg);
378 	if (k->hostkey_type == KEY_UNSPEC)
379 		fatal("bad hostkey alg '%s'", hostkeyalg);
380 	xfree(hostkeyalg);
381 }
382 
383 static int
384 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
385 {
386 	static int check[] = {
387 		PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
388 	};
389 	int *idx;
390 	char *p;
391 
392 	for (idx = &check[0]; *idx != -1; idx++) {
393 		if ((p = strchr(my[*idx], ',')) != NULL)
394 			*p = '\0';
395 		if ((p = strchr(peer[*idx], ',')) != NULL)
396 			*p = '\0';
397 		if (strcmp(my[*idx], peer[*idx]) != 0) {
398 			debug2("proposal mismatch: my %s peer %s",
399 			    my[*idx], peer[*idx]);
400 			return (0);
401 		}
402 	}
403 	debug2("proposals match");
404 	return (1);
405 }
406 
407 static void
408 kex_choose_conf(Kex *kex)
409 {
410 	Newkeys *newkeys;
411 	char **my, **peer;
412 	char **cprop, **sprop;
413 	int nenc, nmac, ncomp;
414 	u_int mode, ctos, need;
415 	int first_kex_follows, type;
416 #ifdef	NONE_CIPHER_ENABLED
417 	int auth_flag;
418 #endif
419 
420 	my   = kex_buf2prop(&kex->my, NULL);
421 	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
422 
423 	if (kex->server) {
424 		cprop=peer;
425 		sprop=my;
426 	} else {
427 		cprop=my;
428 		sprop=peer;
429 	}
430 
431 	/* Check whether server offers roaming */
432 	if (!kex->server) {
433 		char *roaming;
434 		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
435 		if (roaming) {
436 			kex->roaming = 1;
437 			xfree(roaming);
438 		}
439 	}
440 
441 	/* Algorithm Negotiation */
442 #ifdef	NONE_CIPHER_ENABLED
443 	auth_flag = packet_get_authentication_state();
444 	debug ("AUTH STATE is %d", auth_flag);
445 #endif
446 	for (mode = 0; mode < MODE_MAX; mode++) {
447 		newkeys = xcalloc(1, sizeof(*newkeys));
448 		kex->newkeys[mode] = newkeys;
449 		ctos = (!kex->server && mode == MODE_OUT) ||
450 		    (kex->server && mode == MODE_IN);
451 		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
452 		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
453 		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
454 		choose_enc (&newkeys->enc,  cprop[nenc],  sprop[nenc]);
455 		choose_mac (&newkeys->mac,  cprop[nmac],  sprop[nmac]);
456 		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
457 #ifdef	NONE_CIPHER_ENABLED
458 		debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name);
459 		if (strcmp(newkeys->enc.name, "none") == 0) {
460 			debug("Requesting NONE. Authflag is %d", auth_flag);
461 			if (auth_flag == 1)
462 				debug("None requested post authentication.");
463 			else
464 				fatal("Pre-authentication none cipher requests "
465 				    "are not allowed.");
466 		}
467 #endif
468 		debug("kex: %s %s %s %s",
469 		    ctos ? "client->server" : "server->client",
470 		    newkeys->enc.name,
471 		    newkeys->mac.name,
472 		    newkeys->comp.name);
473 	}
474 	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
475 	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
476 	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
477 	need = 0;
478 	for (mode = 0; mode < MODE_MAX; mode++) {
479 		newkeys = kex->newkeys[mode];
480 		if (need < newkeys->enc.key_len)
481 			need = newkeys->enc.key_len;
482 		if (need < newkeys->enc.block_size)
483 			need = newkeys->enc.block_size;
484 		if (need < newkeys->mac.key_len)
485 			need = newkeys->mac.key_len;
486 	}
487 	/* XXX need runden? */
488 	kex->we_need = need;
489 
490 	/* ignore the next message if the proposals do not match */
491 	if (first_kex_follows && !proposals_match(my, peer) &&
492 	    !(datafellows & SSH_BUG_FIRSTKEX)) {
493 		type = packet_read();
494 		debug2("skipping next packet (type %u)", type);
495 	}
496 
497 	kex_prop_free(my);
498 	kex_prop_free(peer);
499 }
500 
501 static u_char *
502 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
503     BIGNUM *shared_secret)
504 {
505 	Buffer b;
506 	EVP_MD_CTX md;
507 	char c = id;
508 	u_int have;
509 	int mdsz;
510 	u_char *digest;
511 
512 	if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
513 		fatal("bad kex md size %d", mdsz);
514 	digest = xmalloc(roundup(need, mdsz));
515 
516 	buffer_init(&b);
517 	buffer_put_bignum2(&b, shared_secret);
518 
519 	/* K1 = HASH(K || H || "A" || session_id) */
520 	EVP_DigestInit(&md, kex->evp_md);
521 	if (!(datafellows & SSH_BUG_DERIVEKEY))
522 		EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
523 	EVP_DigestUpdate(&md, hash, hashlen);
524 	EVP_DigestUpdate(&md, &c, 1);
525 	EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
526 	EVP_DigestFinal(&md, digest, NULL);
527 
528 	/*
529 	 * expand key:
530 	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
531 	 * Key = K1 || K2 || ... || Kn
532 	 */
533 	for (have = mdsz; need > have; have += mdsz) {
534 		EVP_DigestInit(&md, kex->evp_md);
535 		if (!(datafellows & SSH_BUG_DERIVEKEY))
536 			EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
537 		EVP_DigestUpdate(&md, hash, hashlen);
538 		EVP_DigestUpdate(&md, digest, have);
539 		EVP_DigestFinal(&md, digest + have, NULL);
540 	}
541 	buffer_free(&b);
542 #ifdef DEBUG_KEX
543 	fprintf(stderr, "key '%c'== ", c);
544 	dump_digest("key", digest, need);
545 #endif
546 	return digest;
547 }
548 
549 Newkeys *current_keys[MODE_MAX];
550 
551 #define NKEYS	6
552 void
553 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
554 {
555 	u_char *keys[NKEYS];
556 	u_int i, mode, ctos;
557 
558 	for (i = 0; i < NKEYS; i++) {
559 		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
560 		    shared_secret);
561 	}
562 
563 	debug2("kex_derive_keys");
564 	for (mode = 0; mode < MODE_MAX; mode++) {
565 		current_keys[mode] = kex->newkeys[mode];
566 		kex->newkeys[mode] = NULL;
567 		ctos = (!kex->server && mode == MODE_OUT) ||
568 		    (kex->server && mode == MODE_IN);
569 		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
570 		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
571 		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
572 	}
573 }
574 
575 Newkeys *
576 kex_get_newkeys(int mode)
577 {
578 	Newkeys *ret;
579 
580 	ret = current_keys[mode];
581 	current_keys[mode] = NULL;
582 	return ret;
583 }
584 
585 void
586 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
587     u_int8_t cookie[8], u_int8_t id[16])
588 {
589 	const EVP_MD *evp_md = EVP_md5();
590 	EVP_MD_CTX md;
591 	u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
592 	int len;
593 
594 	EVP_DigestInit(&md, evp_md);
595 
596 	len = BN_num_bytes(host_modulus);
597 	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
598 		fatal("%s: bad host modulus (len %d)", __func__, len);
599 	BN_bn2bin(host_modulus, nbuf);
600 	EVP_DigestUpdate(&md, nbuf, len);
601 
602 	len = BN_num_bytes(server_modulus);
603 	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
604 		fatal("%s: bad server modulus (len %d)", __func__, len);
605 	BN_bn2bin(server_modulus, nbuf);
606 	EVP_DigestUpdate(&md, nbuf, len);
607 
608 	EVP_DigestUpdate(&md, cookie, 8);
609 
610 	EVP_DigestFinal(&md, obuf, NULL);
611 	memcpy(id, obuf, 16);
612 
613 	memset(nbuf, 0, sizeof(nbuf));
614 	memset(obuf, 0, sizeof(obuf));
615 	memset(&md, 0, sizeof(md));
616 }
617 
618 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
619 void
620 dump_digest(char *msg, u_char *digest, int len)
621 {
622 	int i;
623 
624 	fprintf(stderr, "%s\n", msg);
625 	for (i = 0; i < len; i++) {
626 		fprintf(stderr, "%02x", digest[i]);
627 		if (i%32 == 31)
628 			fprintf(stderr, "\n");
629 		else if (i%8 == 7)
630 			fprintf(stderr, " ");
631 	}
632 	fprintf(stderr, "\n");
633 }
634 #endif
635