kex.c revision 294328 
1/* $OpenBSD: kex.c,v 1.99 2014/04/29 18:01:49 markus Exp $ */
2/*
3 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "includes.h"
27
28#include <sys/param.h>
29
30#include <signal.h>
31#include <stdarg.h>
32#include <stdio.h>
33#include <stdlib.h>
34#include <string.h>
35
36#ifdef WITH_OPENSSL
37#include <openssl/crypto.h>
38#endif
39
40#include "xmalloc.h"
41#include "ssh2.h"
42#include "buffer.h"
43#include "packet.h"
44#include "compat.h"
45#include "cipher.h"
46#include "key.h"
47#include "kex.h"
48#include "log.h"
49#include "mac.h"
50#include "match.h"
51#include "dispatch.h"
52#include "monitor.h"
53#include "roaming.h"
54#include "digest.h"
55
56#if OPENSSL_VERSION_NUMBER >= 0x00907000L
57# if defined(HAVE_EVP_SHA256)
58# define evp_ssh_sha256 EVP_sha256
59# else
60extern const EVP_MD *evp_ssh_sha256(void);
61# endif
62#endif
63
64/* prototype */
65static void kex_kexinit_finish(Kex *);
66static void kex_choose_conf(Kex *);
67
68struct kexalg {
69	char *name;
70	int type;
71	int ec_nid;
72	int hash_alg;
73};
74static const struct kexalg kexalgs[] = {
75#ifdef WITH_OPENSSL
76	{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
77	{ KEX_DH14, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
78	{ KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
79#ifdef HAVE_EVP_SHA256
80	{ KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
81#endif /* HAVE_EVP_SHA256 */
82#ifdef OPENSSL_HAS_ECC
83	{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
84	    NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
85	{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
86	    SSH_DIGEST_SHA384 },
87# ifdef OPENSSL_HAS_NISTP521
88	{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
89	    SSH_DIGEST_SHA512 },
90# endif /* OPENSSL_HAS_NISTP521 */
91#endif /* OPENSSL_HAS_ECC */
92	{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
93#endif /* WITH_OPENSSL */
94#ifdef HAVE_EVP_SHA256
95	{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
96#endif /* HAVE_EVP_SHA256 */
97	{ NULL, -1, -1, -1},
98};
99
100char *
101kex_alg_list(char sep)
102{
103	char *ret = NULL;
104	size_t nlen, rlen = 0;
105	const struct kexalg *k;
106
107	for (k = kexalgs; k->name != NULL; k++) {
108		if (ret != NULL)
109			ret[rlen++] = sep;
110		nlen = strlen(k->name);
111		ret = xrealloc(ret, 1, rlen + nlen + 2);
112		memcpy(ret + rlen, k->name, nlen + 1);
113		rlen += nlen;
114	}
115	return ret;
116}
117
118static const struct kexalg *
119kex_alg_by_name(const char *name)
120{
121	const struct kexalg *k;
122
123	for (k = kexalgs; k->name != NULL; k++) {
124		if (strcmp(k->name, name) == 0)
125			return k;
126	}
127	return NULL;
128}
129
130/* Validate KEX method name list */
131int
132kex_names_valid(const char *names)
133{
134	char *s, *cp, *p;
135
136	if (names == NULL || strcmp(names, "") == 0)
137		return 0;
138	s = cp = xstrdup(names);
139	for ((p = strsep(&cp, ",")); p && *p != '\0';
140	    (p = strsep(&cp, ","))) {
141		if (kex_alg_by_name(p) == NULL) {
142			error("Unsupported KEX algorithm \"%.100s\"", p);
143			free(s);
144			return 0;
145		}
146	}
147	debug3("kex names ok: [%s]", names);
148	free(s);
149	return 1;
150}
151
152/* put algorithm proposal into buffer */
153static void
154kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
155{
156	u_int i;
157
158	buffer_clear(b);
159	/*
160	 * add a dummy cookie, the cookie will be overwritten by
161	 * kex_send_kexinit(), each time a kexinit is set
162	 */
163	for (i = 0; i < KEX_COOKIE_LEN; i++)
164		buffer_put_char(b, 0);
165	for (i = 0; i < PROPOSAL_MAX; i++)
166		buffer_put_cstring(b, proposal[i]);
167	buffer_put_char(b, 0);			/* first_kex_packet_follows */
168	buffer_put_int(b, 0);			/* uint32 reserved */
169}
170
171/* parse buffer and return algorithm proposal */
172static char **
173kex_buf2prop(Buffer *raw, int *first_kex_follows)
174{
175	Buffer b;
176	u_int i;
177	char **proposal;
178
179	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
180
181	buffer_init(&b);
182	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
183	/* skip cookie */
184	for (i = 0; i < KEX_COOKIE_LEN; i++)
185		buffer_get_char(&b);
186	/* extract kex init proposal strings */
187	for (i = 0; i < PROPOSAL_MAX; i++) {
188		proposal[i] = buffer_get_cstring(&b,NULL);
189		debug2("kex_parse_kexinit: %s", proposal[i]);
190	}
191	/* first kex follows / reserved */
192	i = buffer_get_char(&b);
193	if (first_kex_follows != NULL)
194		*first_kex_follows = i;
195	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
196	i = buffer_get_int(&b);
197	debug2("kex_parse_kexinit: reserved %u ", i);
198	buffer_free(&b);
199	return proposal;
200}
201
202static void
203kex_prop_free(char **proposal)
204{
205	u_int i;
206
207	for (i = 0; i < PROPOSAL_MAX; i++)
208		free(proposal[i]);
209	free(proposal);
210}
211
212/* ARGSUSED */
213static void
214kex_protocol_error(int type, u_int32_t seq, void *ctxt)
215{
216	error("Hm, kex protocol error: type %d seq %u", type, seq);
217}
218
219static void
220kex_reset_dispatch(void)
221{
222	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
223	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
224	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
225}
226
227void
228kex_finish(Kex *kex)
229{
230	kex_reset_dispatch();
231
232	packet_start(SSH2_MSG_NEWKEYS);
233	packet_send();
234	/* packet_write_wait(); */
235	debug("SSH2_MSG_NEWKEYS sent");
236
237	debug("expecting SSH2_MSG_NEWKEYS");
238	packet_read_expect(SSH2_MSG_NEWKEYS);
239	packet_check_eom();
240	debug("SSH2_MSG_NEWKEYS received");
241
242	kex->done = 1;
243	buffer_clear(&kex->peer);
244	/* buffer_clear(&kex->my); */
245	kex->flags &= ~KEX_INIT_SENT;
246	free(kex->name);
247	kex->name = NULL;
248}
249
250void
251kex_send_kexinit(Kex *kex)
252{
253	u_int32_t rnd = 0;
254	u_char *cookie;
255	u_int i;
256
257	if (kex == NULL) {
258		error("kex_send_kexinit: no kex, cannot rekey");
259		return;
260	}
261	if (kex->flags & KEX_INIT_SENT) {
262		debug("KEX_INIT_SENT");
263		return;
264	}
265	kex->done = 0;
266
267	/* generate a random cookie */
268	if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
269		fatal("kex_send_kexinit: kex proposal too short");
270	cookie = buffer_ptr(&kex->my);
271	for (i = 0; i < KEX_COOKIE_LEN; i++) {
272		if (i % 4 == 0)
273			rnd = arc4random();
274		cookie[i] = rnd;
275		rnd >>= 8;
276	}
277	packet_start(SSH2_MSG_KEXINIT);
278	packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
279	packet_send();
280	debug("SSH2_MSG_KEXINIT sent");
281	kex->flags |= KEX_INIT_SENT;
282}
283
284/* ARGSUSED */
285void
286kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
287{
288	char *ptr;
289	u_int i, dlen;
290	Kex *kex = (Kex *)ctxt;
291
292	debug("SSH2_MSG_KEXINIT received");
293	if (kex == NULL)
294		fatal("kex_input_kexinit: no kex, cannot rekey");
295
296	ptr = packet_get_raw(&dlen);
297	buffer_append(&kex->peer, ptr, dlen);
298
299	/* discard packet */
300	for (i = 0; i < KEX_COOKIE_LEN; i++)
301		packet_get_char();
302	for (i = 0; i < PROPOSAL_MAX; i++)
303		free(packet_get_string(NULL));
304	/*
305	 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
306	 * KEX method has the server move first, but a server might be using
307	 * a custom method or one that we otherwise don't support. We should
308	 * be prepared to remember first_kex_follows here so we can eat a
309	 * packet later.
310	 * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means
311	 * for cases where the server *doesn't* go first. I guess we should
312	 * ignore it when it is set for these cases, which is what we do now.
313	 */
314	(void) packet_get_char();	/* first_kex_follows */
315	(void) packet_get_int();	/* reserved */
316	packet_check_eom();
317
318	kex_kexinit_finish(kex);
319}
320
321Kex *
322kex_setup(char *proposal[PROPOSAL_MAX])
323{
324	Kex *kex;
325
326	kex = xcalloc(1, sizeof(*kex));
327	buffer_init(&kex->peer);
328	buffer_init(&kex->my);
329	kex_prop2buf(&kex->my, proposal);
330	kex->done = 0;
331
332	kex_send_kexinit(kex);					/* we start */
333	kex_reset_dispatch();
334
335	return kex;
336}
337
338static void
339kex_kexinit_finish(Kex *kex)
340{
341	if (!(kex->flags & KEX_INIT_SENT))
342		kex_send_kexinit(kex);
343
344	kex_choose_conf(kex);
345
346	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
347	    kex->kex[kex->kex_type] != NULL) {
348		(kex->kex[kex->kex_type])(kex);
349	} else {
350		fatal("Unsupported key exchange %d", kex->kex_type);
351	}
352}
353
354static void
355choose_enc(Enc *enc, char *client, char *server)
356{
357	char *name = match_list(client, server, NULL);
358	if (name == NULL)
359		fatal("no matching cipher found: client %s server %s",
360		    client, server);
361	if ((enc->cipher = cipher_by_name(name)) == NULL)
362		fatal("matching cipher is not supported: %s", name);
363	enc->name = name;
364	enc->enabled = 0;
365	enc->iv = NULL;
366	enc->iv_len = cipher_ivlen(enc->cipher);
367	enc->key = NULL;
368	enc->key_len = cipher_keylen(enc->cipher);
369	enc->block_size = cipher_blocksize(enc->cipher);
370}
371
372static void
373choose_mac(Mac *mac, char *client, char *server)
374{
375	char *name = match_list(client, server, NULL);
376	if (name == NULL)
377		fatal("no matching mac found: client %s server %s",
378		    client, server);
379	if (mac_setup(mac, name) < 0)
380		fatal("unsupported mac %s", name);
381	/* truncate the key */
382	if (datafellows & SSH_BUG_HMAC)
383		mac->key_len = 16;
384	mac->name = name;
385	mac->key = NULL;
386	mac->enabled = 0;
387}
388
389static void
390choose_comp(Comp *comp, char *client, char *server)
391{
392	char *name = match_list(client, server, NULL);
393	if (name == NULL)
394		fatal("no matching comp found: client %s server %s", client, server);
395	if (strcmp(name, "zlib@openssh.com") == 0) {
396		comp->type = COMP_DELAYED;
397	} else if (strcmp(name, "zlib") == 0) {
398		comp->type = COMP_ZLIB;
399	} else if (strcmp(name, "none") == 0) {
400		comp->type = COMP_NONE;
401	} else {
402		fatal("unsupported comp %s", name);
403	}
404	comp->name = name;
405}
406
407static void
408choose_kex(Kex *k, char *client, char *server)
409{
410	const struct kexalg *kexalg;
411
412	k->name = match_list(client, server, NULL);
413	if (k->name == NULL)
414		fatal("Unable to negotiate a key exchange method");
415	if ((kexalg = kex_alg_by_name(k->name)) == NULL)
416		fatal("unsupported kex alg %s", k->name);
417	k->kex_type = kexalg->type;
418	k->hash_alg = kexalg->hash_alg;
419	k->ec_nid = kexalg->ec_nid;
420}
421
422static void
423choose_hostkeyalg(Kex *k, char *client, char *server)
424{
425	char *hostkeyalg = match_list(client, server, NULL);
426	if (hostkeyalg == NULL)
427		fatal("no hostkey alg");
428	k->hostkey_type = key_type_from_name(hostkeyalg);
429	if (k->hostkey_type == KEY_UNSPEC)
430		fatal("bad hostkey alg '%s'", hostkeyalg);
431	free(hostkeyalg);
432}
433
434static int
435proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
436{
437	static int check[] = {
438		PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
439	};
440	int *idx;
441	char *p;
442
443	for (idx = &check[0]; *idx != -1; idx++) {
444		if ((p = strchr(my[*idx], ',')) != NULL)
445			*p = '\0';
446		if ((p = strchr(peer[*idx], ',')) != NULL)
447			*p = '\0';
448		if (strcmp(my[*idx], peer[*idx]) != 0) {
449			debug2("proposal mismatch: my %s peer %s",
450			    my[*idx], peer[*idx]);
451			return (0);
452		}
453	}
454	debug2("proposals match");
455	return (1);
456}
457
458static void
459kex_choose_conf(Kex *kex)
460{
461	Newkeys *newkeys;
462	char **my, **peer;
463	char **cprop, **sprop;
464	int nenc, nmac, ncomp;
465	u_int mode, ctos, need, dh_need, authlen;
466	int first_kex_follows, type;
467
468	my   = kex_buf2prop(&kex->my, NULL);
469	peer = kex_buf2prop(&kex->peer, &first_kex_follows);
470
471	if (kex->server) {
472		cprop=peer;
473		sprop=my;
474	} else {
475		cprop=my;
476		sprop=peer;
477	}
478
479	/* Check whether server offers roaming */
480	if (!kex->server) {
481		char *roaming;
482		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
483		if (roaming) {
484			kex->roaming = 1;
485			free(roaming);
486		}
487	}
488
489	/* Algorithm Negotiation */
490	for (mode = 0; mode < MODE_MAX; mode++) {
491		newkeys = xcalloc(1, sizeof(*newkeys));
492		kex->newkeys[mode] = newkeys;
493		ctos = (!kex->server && mode == MODE_OUT) ||
494		    (kex->server && mode == MODE_IN);
495		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
496		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
497		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
498		choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc]);
499		/* ignore mac for authenticated encryption */
500		authlen = cipher_authlen(newkeys->enc.cipher);
501		if (authlen == 0)
502			choose_mac(&newkeys->mac, cprop[nmac], sprop[nmac]);
503		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
504		debug("kex: %s %s %s %s",
505		    ctos ? "client->server" : "server->client",
506		    newkeys->enc.name,
507		    authlen == 0 ? newkeys->mac.name : "<implicit>",
508		    newkeys->comp.name);
509	}
510	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
511	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
512	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
513	need = dh_need = 0;
514	for (mode = 0; mode < MODE_MAX; mode++) {
515		newkeys = kex->newkeys[mode];
516		need = MAX(need, newkeys->enc.key_len);
517		need = MAX(need, newkeys->enc.block_size);
518		need = MAX(need, newkeys->enc.iv_len);
519		need = MAX(need, newkeys->mac.key_len);
520		dh_need = MAX(dh_need, cipher_seclen(newkeys->enc.cipher));
521		dh_need = MAX(dh_need, newkeys->enc.block_size);
522		dh_need = MAX(dh_need, newkeys->enc.iv_len);
523		dh_need = MAX(dh_need, newkeys->mac.key_len);
524	}
525	/* XXX need runden? */
526	kex->we_need = need;
527	kex->dh_need = dh_need;
528
529	/* ignore the next message if the proposals do not match */
530	if (first_kex_follows && !proposals_match(my, peer) &&
531	    !(datafellows & SSH_BUG_FIRSTKEX)) {
532		type = packet_read();
533		debug2("skipping next packet (type %u)", type);
534	}
535
536	kex_prop_free(my);
537	kex_prop_free(peer);
538}
539
540static u_char *
541derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
542    const u_char *shared_secret, u_int slen)
543{
544	Buffer b;
545	struct ssh_digest_ctx *hashctx;
546	char c = id;
547	u_int have;
548	size_t mdsz;
549	u_char *digest;
550
551	if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
552		fatal("bad kex md size %zu", mdsz);
553	digest = xmalloc(roundup(need, mdsz));
554
555	buffer_init(&b);
556	buffer_append(&b, shared_secret, slen);
557
558	/* K1 = HASH(K || H || "A" || session_id) */
559	if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
560		fatal("%s: ssh_digest_start failed", __func__);
561	if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
562	    ssh_digest_update(hashctx, hash, hashlen) != 0 ||
563	    ssh_digest_update(hashctx, &c, 1) != 0 ||
564	    ssh_digest_update(hashctx, kex->session_id,
565	    kex->session_id_len) != 0)
566		fatal("%s: ssh_digest_update failed", __func__);
567	if (ssh_digest_final(hashctx, digest, mdsz) != 0)
568		fatal("%s: ssh_digest_final failed", __func__);
569	ssh_digest_free(hashctx);
570
571	/*
572	 * expand key:
573	 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
574	 * Key = K1 || K2 || ... || Kn
575	 */
576	for (have = mdsz; need > have; have += mdsz) {
577		if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
578			fatal("%s: ssh_digest_start failed", __func__);
579		if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
580		    ssh_digest_update(hashctx, hash, hashlen) != 0 ||
581		    ssh_digest_update(hashctx, digest, have) != 0)
582			fatal("%s: ssh_digest_update failed", __func__);
583		if (ssh_digest_final(hashctx, digest + have, mdsz) != 0)
584			fatal("%s: ssh_digest_final failed", __func__);
585		ssh_digest_free(hashctx);
586	}
587	buffer_free(&b);
588#ifdef DEBUG_KEX
589	fprintf(stderr, "key '%c'== ", c);
590	dump_digest("key", digest, need);
591#endif
592	return digest;
593}
594
595Newkeys *current_keys[MODE_MAX];
596
597#define NKEYS	6
598void
599kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen,
600    const u_char *shared_secret, u_int slen)
601{
602	u_char *keys[NKEYS];
603	u_int i, mode, ctos;
604
605	for (i = 0; i < NKEYS; i++) {
606		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
607		    shared_secret, slen);
608	}
609
610	debug2("kex_derive_keys");
611	for (mode = 0; mode < MODE_MAX; mode++) {
612		current_keys[mode] = kex->newkeys[mode];
613		kex->newkeys[mode] = NULL;
614		ctos = (!kex->server && mode == MODE_OUT) ||
615		    (kex->server && mode == MODE_IN);
616		current_keys[mode]->enc.iv  = keys[ctos ? 0 : 1];
617		current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
618		current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
619	}
620}
621
622#ifdef WITH_OPENSSL
623void
624kex_derive_keys_bn(Kex *kex, u_char *hash, u_int hashlen, const BIGNUM *secret)
625{
626	Buffer shared_secret;
627
628	buffer_init(&shared_secret);
629	buffer_put_bignum2(&shared_secret, secret);
630	kex_derive_keys(kex, hash, hashlen,
631	    buffer_ptr(&shared_secret), buffer_len(&shared_secret));
632	buffer_free(&shared_secret);
633}
634#endif
635
636Newkeys *
637kex_get_newkeys(int mode)
638{
639	Newkeys *ret;
640
641	ret = current_keys[mode];
642	current_keys[mode] = NULL;
643	return ret;
644}
645
646#ifdef WITH_SSH1
647void
648derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
649    u_int8_t cookie[8], u_int8_t id[16])
650{
651	u_int8_t nbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
652	int len;
653	struct ssh_digest_ctx *hashctx;
654
655	if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL)
656		fatal("%s: ssh_digest_start", __func__);
657
658	len = BN_num_bytes(host_modulus);
659	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
660		fatal("%s: bad host modulus (len %d)", __func__, len);
661	BN_bn2bin(host_modulus, nbuf);
662	if (ssh_digest_update(hashctx, nbuf, len) != 0)
663		fatal("%s: ssh_digest_update failed", __func__);
664
665	len = BN_num_bytes(server_modulus);
666	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
667		fatal("%s: bad server modulus (len %d)", __func__, len);
668	BN_bn2bin(server_modulus, nbuf);
669	if (ssh_digest_update(hashctx, nbuf, len) != 0 ||
670	    ssh_digest_update(hashctx, cookie, 8) != 0)
671		fatal("%s: ssh_digest_update failed", __func__);
672	if (ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0)
673		fatal("%s: ssh_digest_final failed", __func__);
674	memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
675
676	explicit_bzero(nbuf, sizeof(nbuf));
677	explicit_bzero(obuf, sizeof(obuf));
678}
679#endif
680
681#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
682void
683dump_digest(char *msg, u_char *digest, int len)
684{
685	int i;
686
687	fprintf(stderr, "%s\n", msg);
688	for (i = 0; i < len; i++) {
689		fprintf(stderr, "%02x", digest[i]);
690		if (i%32 == 31)
691			fprintf(stderr, "\n");
692		else if (i%8 == 7)
693			fprintf(stderr, " ");
694	}
695	fprintf(stderr, "\n");
696}
697#endif
698