[openssh.git] / kexdhc.c

/* $OpenBSD: kexdhc.c,v 1.8 2006/08/01 23:22:47 stevesk 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 <stdio.h>
#include <string.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 parameter 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
cf851879	1	/* $OpenBSD: kexdhc.c,v 1.8 2006/08/01 23:22:47 stevesk 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
cf851879	28	#include <stdio.h>
00146caa	29	#include <string.h>
00146caa	30
98a58eda	31	#include "xmalloc.h"
	32	#include "key.h"
	33	#include "kex.h"
	34	#include "log.h"
	35	#include "packet.h"
	36	#include "dh.h"
	37	#include "ssh2.h"
	38
	39	void
	40	kexdh_client(Kex *kex)
	41	{
	42	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	43	DH *dh;
	44	Key *server_host_key;
	45	u_char server_host_key_blob = NULL, signature = NULL;
	46	u_char kbuf, hash;
47e5dc72	47	u_int klen, kout, slen, sbloblen, hashlen;
98a58eda	48
98a58eda	49	/* generate and send 'e', client DH public key */
41e5bd9a	50	switch (kex->kex_type) {
	51	case KEX_DH_GRP1_SHA1:
	52	dh = dh_new_group1();
	53	break;
	54	case KEX_DH_GRP14_SHA1:
	55	dh = dh_new_group14();
	56	break;
	57	default:
	58	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	59	}
98a58eda	60	dh_gen_key(dh, kex->we_need * 8);
	61	packet_start(SSH2_MSG_KEXDH_INIT);
	62	packet_put_bignum2(dh->pub_key);
	63	packet_send();
	64
	65	debug("sending SSH2_MSG_KEXDH_INIT");
	66	#ifdef DEBUG_KEXDH
	67	DHparams_print_fp(stderr, dh);
	68	fprintf(stderr, "pub= ");
	69	BN_print_fp(stderr, dh->pub_key);
	70	fprintf(stderr, "\n");
	71	#endif
	72
	73	debug("expecting SSH2_MSG_KEXDH_REPLY");
	74	packet_read_expect(SSH2_MSG_KEXDH_REPLY);
	75
	76	/* key, cert */
	77	server_host_key_blob = packet_get_string(&sbloblen);
	78	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	79	if (server_host_key == NULL)
	80	fatal("cannot decode server_host_key_blob");
	81	if (server_host_key->type != kex->hostkey_type)
	82	fatal("type mismatch for decoded server_host_key_blob");
	83	if (kex->verify_host_key == NULL)
	84	fatal("cannot verify server_host_key");
	85	if (kex->verify_host_key(server_host_key) == -1)
	86	fatal("server_host_key verification failed");
	87
18c60a0b	88	/* DH parameter f, server public DH key */
98a58eda	89	if ((dh_server_pub = BN_new()) == NULL)
	90	fatal("dh_server_pub == NULL");
	91	packet_get_bignum2(dh_server_pub);
	92
	93	#ifdef DEBUG_KEXDH
	94	fprintf(stderr, "dh_server_pub= ");
	95	BN_print_fp(stderr, dh_server_pub);
	96	fprintf(stderr, "\n");
	97	debug("bits %d", BN_num_bits(dh_server_pub));
	98	#endif
	99
	100	/* signed H */
	101	signature = packet_get_string(&slen);
	102	packet_check_eom();
	103
	104	if (!dh_pub_is_valid(dh, dh_server_pub))
	105	packet_disconnect("bad server public DH value");
	106
	107	klen = DH_size(dh);
	108	kbuf = xmalloc(klen);
	109	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	110	#ifdef DEBUG_KEXDH
	111	dump_digest("shared secret", kbuf, kout);
	112	#endif
	113	if ((shared_secret = BN_new()) == NULL)
	114	fatal("kexdh_client: BN_new failed");
	115	BN_bin2bn(kbuf, kout, shared_secret);
	116	memset(kbuf, 0, klen);
	117	xfree(kbuf);
	118
	119	/* calc and verify H */
47e5dc72	120	kex_dh_hash(
98a58eda	121	kex->client_version_string,
	122	kex->server_version_string,
	123	buffer_ptr(&kex->my), buffer_len(&kex->my),
	124	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	125	server_host_key_blob, sbloblen,
	126	dh->pub_key,
	127	dh_server_pub,
47e5dc72	128	shared_secret,
47e5dc72	129	&hash, &hashlen
98a58eda	130	);
	131	xfree(server_host_key_blob);
	132	BN_clear_free(dh_server_pub);
	133	DH_free(dh);
	134
47e5dc72	135	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	136	fatal("key_verify failed for server_host_key");
	137	key_free(server_host_key);
	138	xfree(signature);
	139
	140	/* save session id */
	141	if (kex->session_id == NULL) {
47e5dc72	142	kex->session_id_len = hashlen;
98a58eda	143	kex->session_id = xmalloc(kex->session_id_len);
	144	memcpy(kex->session_id, hash, kex->session_id_len);
	145	}
	146
47e5dc72	147	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	148	BN_clear_free(shared_secret);
	149	kex_finish(kex);
	150	}