[openssh.git] / kexdh.c

/*
 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: kexdh.c,v 1.12 2001/12/28 14:50:54 markus Exp $");

#include <openssl/crypto.h>
#include <openssl/bn.h>

#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "key.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "dh.h"
#include "ssh2.h"

static u_char *
kex_dh_hash(
    char *client_version_string,
    char *server_version_string,
    char *ckexinit, int ckexinitlen,
    char *skexinit, int skexinitlen,
    u_char *serverhostkeyblob, int sbloblen,
    BIGNUM *client_dh_pub,
    BIGNUM *server_dh_pub,
    BIGNUM *shared_secret)
{
	Buffer b;
	static u_char digest[EVP_MAX_MD_SIZE];
	EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;

	buffer_init(&b);
	buffer_put_cstring(&b, client_version_string);
	buffer_put_cstring(&b, server_version_string);

	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	buffer_put_int(&b, ckexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, ckexinit, ckexinitlen);
	buffer_put_int(&b, skexinitlen+1);
	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	buffer_append(&b, skexinit, skexinitlen);

	buffer_put_string(&b, serverhostkeyblob, sbloblen);
	buffer_put_bignum2(&b, client_dh_pub);
	buffer_put_bignum2(&b, server_dh_pub);
	buffer_put_bignum2(&b, shared_secret);

#ifdef DEBUG_KEX
	buffer_dump(&b);
#endif
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	EVP_DigestFinal(&md, digest, NULL);

	buffer_free(&b);

#ifdef DEBUG_KEX
	dump_digest("hash", digest, evp_md->md_size);
#endif
	return digest;
}

/* client */

static void
kexdh_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	DH *dh;
	Key *server_host_key;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf, *hash;
	u_int klen, kout, slen, sbloblen;

	/* generate and send 'e', client DH public key */
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);
	packet_start(SSH2_MSG_KEXDH_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();

	debug("sending SSH2_MSG_KEXDH_INIT");
#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif

	debug("expecting SSH2_MSG_KEXDH_REPLY");
	packet_read_expect(SSH2_MSG_KEXDH_REPLY);

	/* key, cert */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
		fatal("cannot decode server_host_key_blob");

	if (kex->verify_host_key == NULL)
		fatal("cannot verify server_host_key");
	if (kex->verify_host_key(server_host_key) == -1)
		fatal("server_host_key verification failed");

	/* DH paramter f, server public DH key */
	if ((dh_server_pub = BN_new()) == NULL)
		fatal("dh_server_pub == NULL");
	packet_get_bignum2(dh_server_pub);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_server_pub= ");
	BN_print_fp(stderr, dh_server_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_server_pub));
#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_check_eom();

	if (!dh_pub_is_valid(dh, dh_server_pub))
		packet_disconnect("bad server public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_client: BN_new failed");
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	/* calc and verify H */
	hash = kex_dh_hash(
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    server_host_key_blob, sbloblen,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret
	);
	xfree(server_host_key_blob);
	BN_clear_free(dh_server_pub);
	DH_free(dh);

	if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
		fatal("key_verify failed for server_host_key");
	key_free(server_host_key);
	xfree(signature);

	/* save session id */
	if (kex->session_id == NULL) {
		kex->session_id_len = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);
}

/* server */

static void
kexdh_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	DH *dh;
	Key *server_host_key;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, kout;
	int slen;

	/* generate server DH public key */
	dh = dh_new_group1();
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEXDH_INIT");
	packet_read_expect(SSH2_MSG_KEXDH_INIT);

	if (kex->load_host_key == NULL)
		fatal("Cannot load hostkey");
	server_host_key = kex->load_host_key(kex->hostkey_type);
	if (server_host_key == NULL)
		fatal("Unsupported hostkey type %d", kex->hostkey_type);

	/* key, cert */
	if ((dh_client_pub = BN_new()) == NULL)
		fatal("dh_client_pub == NULL");
	packet_get_bignum2(dh_client_pub);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_client_pub= ");
	BN_print_fp(stderr, dh_client_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_client_pub));
#endif

#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif
	if (!dh_pub_is_valid(dh, dh_client_pub))
		packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_client_pub, dh);
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_server: BN_new failed");
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);

	/* calc H */
	hash = kex_dh_hash(
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    server_host_key_blob, sbloblen,
	    dh_client_pub,
	    dh->pub_key,
	    shared_secret
	);
	BN_clear_free(dh_client_pub);

	/* save session id := H */
	/* XXX hashlen depends on KEX */
	if (kex->session_id == NULL) {
		kex->session_id_len = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	/* sign H */
	/* XXX hashlen depends on KEX */
	key_sign(server_host_key, &signature, &slen, hash, 20);

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and singed H */
	packet_start(SSH2_MSG_KEXDH_REPLY);
	packet_put_string(server_host_key_blob, sbloblen);
	packet_put_bignum2(dh->pub_key);	/* f */
	packet_put_string(signature, slen);
	packet_send();

	xfree(signature);
	xfree(server_host_key_blob);
	/* have keys, free DH */
	DH_free(dh);

	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);
}

void
kexdh(Kex *kex)
{
	if (kex->server)
		kexdh_server(kex);
	else
		kexdh_client(kex);
}
Commit	Line	Data
0bc35151	1	/*
	2	* Copyright (c) 2001 Markus Friedl. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	14	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	15	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	16	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	17	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	18	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	19	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	20	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	21	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	22	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	23	*/
	24
	25	#include "includes.h"
54a5250f	26	RCSID("$OpenBSD: kexdh.c,v 1.12 2001/12/28 14:50:54 markus Exp $");
0bc35151	27
	28	#include <openssl/crypto.h>
	29	#include <openssl/bn.h>
	30
	31	#include "xmalloc.h"
	32	#include "buffer.h"
	33	#include "bufaux.h"
	34	#include "key.h"
	35	#include "kex.h"
	36	#include "log.h"
	37	#include "packet.h"
	38	#include "dh.h"
	39	#include "ssh2.h"
	40
396c147e	41	static u_char *
0bc35151	42	kex_dh_hash(
	43	char *client_version_string,
	44	char *server_version_string,
	45	char *ckexinit, int ckexinitlen,
	46	char *skexinit, int skexinitlen,
cf54363d	47	u_char *serverhostkeyblob, int sbloblen,
0bc35151	48	BIGNUM *client_dh_pub,
	49	BIGNUM *server_dh_pub,
	50	BIGNUM *shared_secret)
	51	{
	52	Buffer b;
	53	static u_char digest[EVP_MAX_MD_SIZE];
	54	EVP_MD *evp_md = EVP_sha1();
	55	EVP_MD_CTX md;
	56
	57	buffer_init(&b);
449c5ba5	58	buffer_put_cstring(&b, client_version_string);
449c5ba5	59	buffer_put_cstring(&b, server_version_string);
0bc35151	60
	61	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
	62	buffer_put_int(&b, ckexinitlen+1);
	63	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	64	buffer_append(&b, ckexinit, ckexinitlen);
	65	buffer_put_int(&b, skexinitlen+1);
	66	buffer_put_char(&b, SSH2_MSG_KEXINIT);
	67	buffer_append(&b, skexinit, skexinitlen);
	68
	69	buffer_put_string(&b, serverhostkeyblob, sbloblen);
	70	buffer_put_bignum2(&b, client_dh_pub);
	71	buffer_put_bignum2(&b, server_dh_pub);
	72	buffer_put_bignum2(&b, shared_secret);
	73
	74	#ifdef DEBUG_KEX
	75	buffer_dump(&b);
	76	#endif
	77	EVP_DigestInit(&md, evp_md);
	78	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
	79	EVP_DigestFinal(&md, digest, NULL);
	80
	81	buffer_free(&b);
	82
	83	#ifdef DEBUG_KEX
	84	dump_digest("hash", digest, evp_md->md_size);
	85	#endif
	86	return digest;
	87	}
	88
	89	/* client */
	90
396c147e	91	static void
0bc35151	92	kexdh_client(Kex *kex)
	93	{
	94	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	95	DH *dh;
	96	Key *server_host_key;
cf54363d	97	u_char server_host_key_blob = NULL, signature = NULL;
0bc35151	98	u_char kbuf, hash;
0bc35151	99	u_int klen, kout, slen, sbloblen;
0bc35151	100
	101	/* generate and send 'e', client DH public key */
	102	dh = dh_new_group1();
	103	dh_gen_key(dh, kex->we_need * 8);
	104	packet_start(SSH2_MSG_KEXDH_INIT);
	105	packet_put_bignum2(dh->pub_key);
	106	packet_send();
	107
	108	debug("sending SSH2_MSG_KEXDH_INIT");
	109	#ifdef DEBUG_KEXDH
	110	DHparams_print_fp(stderr, dh);
	111	fprintf(stderr, "pub= ");
	112	BN_print_fp(stderr, dh->pub_key);
	113	fprintf(stderr, "\n");
	114	#endif
	115
	116	debug("expecting SSH2_MSG_KEXDH_REPLY");
54a5250f	117	packet_read_expect(SSH2_MSG_KEXDH_REPLY);
0bc35151	118
	119	/* key, cert */
	120	server_host_key_blob = packet_get_string(&sbloblen);
	121	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	122	if (server_host_key == NULL)
	123	fatal("cannot decode server_host_key_blob");
	124
f49bc4f7	125	if (kex->verify_host_key == NULL)
	126	fatal("cannot verify server_host_key");
	127	if (kex->verify_host_key(server_host_key) == -1)
	128	fatal("server_host_key verification failed");
0bc35151	129
0bc35151	130	/* DH paramter f, server public DH key */
b775c6f2	131	if ((dh_server_pub = BN_new()) == NULL)
0bc35151	132	fatal("dh_server_pub == NULL");
20b279e6	133	packet_get_bignum2(dh_server_pub);
0bc35151	134
	135	#ifdef DEBUG_KEXDH
	136	fprintf(stderr, "dh_server_pub= ");
	137	BN_print_fp(stderr, dh_server_pub);
	138	fprintf(stderr, "\n");
	139	debug("bits %d", BN_num_bits(dh_server_pub));
	140	#endif
	141
	142	/* signed H */
	143	signature = packet_get_string(&slen);
95500969	144	packet_check_eom();
0bc35151	145
	146	if (!dh_pub_is_valid(dh, dh_server_pub))
	147	packet_disconnect("bad server public DH value");
	148
	149	klen = DH_size(dh);
	150	kbuf = xmalloc(klen);
	151	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	152	#ifdef DEBUG_KEXDH
	153	dump_digest("shared secret", kbuf, kout);
	154	#endif
b775c6f2	155	if ((shared_secret = BN_new()) == NULL)
b775c6f2	156	fatal("kexdh_client: BN_new failed");
0bc35151	157	BN_bin2bn(kbuf, kout, shared_secret);
	158	memset(kbuf, 0, klen);
	159	xfree(kbuf);
	160
	161	/* calc and verify H */
	162	hash = kex_dh_hash(
	163	kex->client_version_string,
	164	kex->server_version_string,
	165	buffer_ptr(&kex->my), buffer_len(&kex->my),
	166	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	167	server_host_key_blob, sbloblen,
	168	dh->pub_key,
	169	dh_server_pub,
	170	shared_secret
	171	);
	172	xfree(server_host_key_blob);
108d362e	173	BN_clear_free(dh_server_pub);
d8ee838b	174	DH_free(dh);
0bc35151	175
cf54363d	176	if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
0bc35151	177	fatal("key_verify failed for server_host_key");
	178	key_free(server_host_key);
	179	xfree(signature);
	180
	181	/* save session id */
	182	if (kex->session_id == NULL) {
	183	kex->session_id_len = 20;
	184	kex->session_id = xmalloc(kex->session_id_len);
	185	memcpy(kex->session_id, hash, kex->session_id_len);
	186	}
	187
	188	kex_derive_keys(kex, hash, shared_secret);
	189	BN_clear_free(shared_secret);
d8ee838b	190	kex_finish(kex);
0bc35151	191	}
	192
	193	/* server */
	194
396c147e	195	static void
0bc35151	196	kexdh_server(Kex *kex)
	197	{
	198	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	199	DH *dh;
	200	Key *server_host_key;
	201	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	202	u_int sbloblen, klen, kout;
54a5250f	203	int slen;
0bc35151	204
	205	/* generate server DH public key */
	206	dh = dh_new_group1();
	207	dh_gen_key(dh, kex->we_need * 8);
	208
	209	debug("expecting SSH2_MSG_KEXDH_INIT");
54a5250f	210	packet_read_expect(SSH2_MSG_KEXDH_INIT);
0bc35151	211
	212	if (kex->load_host_key == NULL)
	213	fatal("Cannot load hostkey");
	214	server_host_key = kex->load_host_key(kex->hostkey_type);
	215	if (server_host_key == NULL)
	216	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	217
	218	/* key, cert */
b775c6f2	219	if ((dh_client_pub = BN_new()) == NULL)
0bc35151	220	fatal("dh_client_pub == NULL");
20b279e6	221	packet_get_bignum2(dh_client_pub);
0bc35151	222
	223	#ifdef DEBUG_KEXDH
	224	fprintf(stderr, "dh_client_pub= ");
	225	BN_print_fp(stderr, dh_client_pub);
	226	fprintf(stderr, "\n");
	227	debug("bits %d", BN_num_bits(dh_client_pub));
	228	#endif
	229
	230	#ifdef DEBUG_KEXDH
	231	DHparams_print_fp(stderr, dh);
	232	fprintf(stderr, "pub= ");
	233	BN_print_fp(stderr, dh->pub_key);
	234	fprintf(stderr, "\n");
	235	#endif
	236	if (!dh_pub_is_valid(dh, dh_client_pub))
	237	packet_disconnect("bad client public DH value");
	238
	239	klen = DH_size(dh);
	240	kbuf = xmalloc(klen);
	241	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	242	#ifdef DEBUG_KEXDH
	243	dump_digest("shared secret", kbuf, kout);
	244	#endif
b775c6f2	245	if ((shared_secret = BN_new()) == NULL)
b775c6f2	246	fatal("kexdh_server: BN_new failed");
0bc35151	247	BN_bin2bn(kbuf, kout, shared_secret);
	248	memset(kbuf, 0, klen);
	249	xfree(kbuf);
	250
	251	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	252
	253	/* calc H */
	254	hash = kex_dh_hash(
	255	kex->client_version_string,
	256	kex->server_version_string,
	257	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	258	buffer_ptr(&kex->my), buffer_len(&kex->my),
cf54363d	259	server_host_key_blob, sbloblen,
0bc35151	260	dh_client_pub,
	261	dh->pub_key,
	262	shared_secret
	263	);
108d362e	264	BN_clear_free(dh_client_pub);
0bc35151	265
	266	/* save session id := H */
	267	/* XXX hashlen depends on KEX */
	268	if (kex->session_id == NULL) {
	269	kex->session_id_len = 20;
	270	kex->session_id = xmalloc(kex->session_id_len);
	271	memcpy(kex->session_id, hash, kex->session_id_len);
	272	}
	273
	274	/* sign H */
	275	/* XXX hashlen depends on KEX */
	276	key_sign(server_host_key, &signature, &slen, hash, 20);
	277
	278	/* destroy_sensitive_data(); */
	279
	280	/* send server hostkey, DH pubkey 'f' and singed H */
	281	packet_start(SSH2_MSG_KEXDH_REPLY);
cf54363d	282	packet_put_string(server_host_key_blob, sbloblen);
0bc35151	283	packet_put_bignum2(dh->pub_key); /* f */
cf54363d	284	packet_put_string(signature, slen);
0bc35151	285	packet_send();
d8ee838b	286
0bc35151	287	xfree(signature);
0bc35151	288	xfree(server_host_key_blob);
d8ee838b	289	/* have keys, free DH */
d8ee838b	290	DH_free(dh);
0bc35151	291
	292	kex_derive_keys(kex, hash, shared_secret);
	293	BN_clear_free(shared_secret);
d8ee838b	294	kex_finish(kex);
0bc35151	295	}
	296
	297	void
	298	kexdh(Kex *kex)
	299	{
	300	if (kex->server)
	301	kexdh_server(kex);
	302	else
	303	kexdh_client(kex);
	304	}