[openssh.git] / kexdhc.c

/* $OpenBSD: kexdhc.c,v 1.5 2006/03/25 13:17:02 djm Exp $ */
/*
 * 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"

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

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, hashlen;

	/* generate and send 'e', client DH public key */
	switch (kex->kex_type) {
	case KEX_DH_GRP1_SHA1:
		dh = dh_new_group1();
		break;
	case KEX_DH_GRP14_SHA1:
		dh = dh_new_group14();
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}
	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 (server_host_key->type != kex->hostkey_type)
		fatal("type mismatch for decoded 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 */
	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,
	    &hash, &hashlen
	);
	xfree(server_host_key_blob);
	BN_clear_free(dh_server_pub);
	DH_free(dh);

	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 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 = hashlen;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);
	kex_finish(kex);
}
Commit	Line	Data
c1cb7bae	1	/* $OpenBSD: kexdhc.c,v 1.5 2006/03/25 13:17:02 djm Exp $ */
98a58eda	2	/*
	3	* Copyright (c) 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"
98a58eda	27
	28	#include "xmalloc.h"
	29	#include "key.h"
	30	#include "kex.h"
	31	#include "log.h"
	32	#include "packet.h"
	33	#include "dh.h"
	34	#include "ssh2.h"
	35
	36	void
	37	kexdh_client(Kex *kex)
	38	{
	39	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	40	DH *dh;
	41	Key *server_host_key;
	42	u_char server_host_key_blob = NULL, signature = NULL;
	43	u_char kbuf, hash;
47e5dc72	44	u_int klen, kout, slen, sbloblen, hashlen;
98a58eda	45
98a58eda	46	/* generate and send 'e', client DH public key */
41e5bd9a	47	switch (kex->kex_type) {
	48	case KEX_DH_GRP1_SHA1:
	49	dh = dh_new_group1();
	50	break;
	51	case KEX_DH_GRP14_SHA1:
	52	dh = dh_new_group14();
	53	break;
	54	default:
	55	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	56	}
98a58eda	57	dh_gen_key(dh, kex->we_need * 8);
	58	packet_start(SSH2_MSG_KEXDH_INIT);
	59	packet_put_bignum2(dh->pub_key);
	60	packet_send();
	61
	62	debug("sending SSH2_MSG_KEXDH_INIT");
	63	#ifdef DEBUG_KEXDH
	64	DHparams_print_fp(stderr, dh);
	65	fprintf(stderr, "pub= ");
	66	BN_print_fp(stderr, dh->pub_key);
	67	fprintf(stderr, "\n");
	68	#endif
	69
	70	debug("expecting SSH2_MSG_KEXDH_REPLY");
	71	packet_read_expect(SSH2_MSG_KEXDH_REPLY);
	72
	73	/* key, cert */
	74	server_host_key_blob = packet_get_string(&sbloblen);
	75	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	76	if (server_host_key == NULL)
	77	fatal("cannot decode server_host_key_blob");
	78	if (server_host_key->type != kex->hostkey_type)
	79	fatal("type mismatch for decoded server_host_key_blob");
	80	if (kex->verify_host_key == NULL)
	81	fatal("cannot verify server_host_key");
	82	if (kex->verify_host_key(server_host_key) == -1)
	83	fatal("server_host_key verification failed");
	84
	85	/* DH paramter f, server public DH key */
	86	if ((dh_server_pub = BN_new()) == NULL)
	87	fatal("dh_server_pub == NULL");
	88	packet_get_bignum2(dh_server_pub);
	89
	90	#ifdef DEBUG_KEXDH
	91	fprintf(stderr, "dh_server_pub= ");
	92	BN_print_fp(stderr, dh_server_pub);
	93	fprintf(stderr, "\n");
	94	debug("bits %d", BN_num_bits(dh_server_pub));
	95	#endif
	96
	97	/* signed H */
	98	signature = packet_get_string(&slen);
	99	packet_check_eom();
	100
	101	if (!dh_pub_is_valid(dh, dh_server_pub))
	102	packet_disconnect("bad server public DH value");
	103
	104	klen = DH_size(dh);
	105	kbuf = xmalloc(klen);
	106	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	107	#ifdef DEBUG_KEXDH
	108	dump_digest("shared secret", kbuf, kout);
	109	#endif
	110	if ((shared_secret = BN_new()) == NULL)
	111	fatal("kexdh_client: BN_new failed");
	112	BN_bin2bn(kbuf, kout, shared_secret);
	113	memset(kbuf, 0, klen);
	114	xfree(kbuf);
	115
	116	/* calc and verify H */
47e5dc72	117	kex_dh_hash(
98a58eda	118	kex->client_version_string,
	119	kex->server_version_string,
	120	buffer_ptr(&kex->my), buffer_len(&kex->my),
	121	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	122	server_host_key_blob, sbloblen,
	123	dh->pub_key,
	124	dh_server_pub,
47e5dc72	125	shared_secret,
47e5dc72	126	&hash, &hashlen
98a58eda	127	);
	128	xfree(server_host_key_blob);
	129	BN_clear_free(dh_server_pub);
	130	DH_free(dh);
	131
47e5dc72	132	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	133	fatal("key_verify failed for server_host_key");
	134	key_free(server_host_key);
	135	xfree(signature);
	136
	137	/* save session id */
	138	if (kex->session_id == NULL) {
47e5dc72	139	kex->session_id_len = hashlen;
98a58eda	140	kex->session_id = xmalloc(kex->session_id_len);
	141	memcpy(kex->session_id, hash, kex->session_id_len);
	142	}
	143
47e5dc72	144	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	145	BN_clear_free(shared_secret);
	146	kex_finish(kex);
	147	}