[openssh.git] / kexdhc.c

/* $OpenBSD: kexdhc.c,v 1.11 2006/11/06 21:25:28 markus 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 <sys/types.h>

#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>

#include "xmalloc.h"
#include "buffer.h"
#include "key.h"
#include "cipher.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, slen, sbloblen, hashlen;
	int kout;

	/* 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);
	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
		fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_client: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexdh_client: BN_bin2bn failed");
	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
e516451d	1	/* $OpenBSD: kexdhc.c,v 1.11 2006/11/06 21:25:28 markus 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
31652869	28	#include <sys/types.h>
31652869	29
24436b92	30	#include <stdarg.h>
cf851879	31	#include <stdio.h>
00146caa	32	#include <string.h>
31652869	33	#include <signal.h>
00146caa	34
98a58eda	35	#include "xmalloc.h"
31652869	36	#include "buffer.h"
98a58eda	37	#include "key.h"
31652869	38	#include "cipher.h"
98a58eda	39	#include "kex.h"
	40	#include "log.h"
	41	#include "packet.h"
	42	#include "dh.h"
	43	#include "ssh2.h"
	44
	45	void
	46	kexdh_client(Kex *kex)
	47	{
	48	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	49	DH *dh;
	50	Key *server_host_key;
	51	u_char server_host_key_blob = NULL, signature = NULL;
	52	u_char kbuf, hash;
8e8b473c	53	u_int klen, slen, sbloblen, hashlen;
8e8b473c	54	int kout;
98a58eda	55
98a58eda	56	/* generate and send 'e', client DH public key */
41e5bd9a	57	switch (kex->kex_type) {
	58	case KEX_DH_GRP1_SHA1:
	59	dh = dh_new_group1();
	60	break;
	61	case KEX_DH_GRP14_SHA1:
	62	dh = dh_new_group14();
	63	break;
	64	default:
	65	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	66	}
98a58eda	67	dh_gen_key(dh, kex->we_need * 8);
	68	packet_start(SSH2_MSG_KEXDH_INIT);
	69	packet_put_bignum2(dh->pub_key);
	70	packet_send();
	71
	72	debug("sending SSH2_MSG_KEXDH_INIT");
	73	#ifdef DEBUG_KEXDH
	74	DHparams_print_fp(stderr, dh);
	75	fprintf(stderr, "pub= ");
	76	BN_print_fp(stderr, dh->pub_key);
	77	fprintf(stderr, "\n");
	78	#endif
	79
	80	debug("expecting SSH2_MSG_KEXDH_REPLY");
	81	packet_read_expect(SSH2_MSG_KEXDH_REPLY);
	82
	83	/* key, cert */
	84	server_host_key_blob = packet_get_string(&sbloblen);
	85	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	86	if (server_host_key == NULL)
	87	fatal("cannot decode server_host_key_blob");
	88	if (server_host_key->type != kex->hostkey_type)
	89	fatal("type mismatch for decoded server_host_key_blob");
	90	if (kex->verify_host_key == NULL)
	91	fatal("cannot verify server_host_key");
	92	if (kex->verify_host_key(server_host_key) == -1)
	93	fatal("server_host_key verification failed");
	94
18c60a0b	95	/* DH parameter f, server public DH key */
98a58eda	96	if ((dh_server_pub = BN_new()) == NULL)
	97	fatal("dh_server_pub == NULL");
	98	packet_get_bignum2(dh_server_pub);
	99
	100	#ifdef DEBUG_KEXDH
	101	fprintf(stderr, "dh_server_pub= ");
	102	BN_print_fp(stderr, dh_server_pub);
	103	fprintf(stderr, "\n");
	104	debug("bits %d", BN_num_bits(dh_server_pub));
	105	#endif
	106
	107	/* signed H */
	108	signature = packet_get_string(&slen);
	109	packet_check_eom();
	110
	111	if (!dh_pub_is_valid(dh, dh_server_pub))
	112	packet_disconnect("bad server public DH value");
	113
	114	klen = DH_size(dh);
	115	kbuf = xmalloc(klen);
8e8b473c	116	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
8e8b473c	117	fatal("DH_compute_key: failed");
98a58eda	118	#ifdef DEBUG_KEXDH
	119	dump_digest("shared secret", kbuf, kout);
	120	#endif
	121	if ((shared_secret = BN_new()) == NULL)
	122	fatal("kexdh_client: BN_new failed");
e516451d	123	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
e516451d	124	fatal("kexdh_client: BN_bin2bn failed");
98a58eda	125	memset(kbuf, 0, klen);
	126	xfree(kbuf);
	127
	128	/* calc and verify H */
47e5dc72	129	kex_dh_hash(
98a58eda	130	kex->client_version_string,
	131	kex->server_version_string,
	132	buffer_ptr(&kex->my), buffer_len(&kex->my),
	133	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	134	server_host_key_blob, sbloblen,
	135	dh->pub_key,
	136	dh_server_pub,
47e5dc72	137	shared_secret,
47e5dc72	138	&hash, &hashlen
98a58eda	139	);
	140	xfree(server_host_key_blob);
	141	BN_clear_free(dh_server_pub);
	142	DH_free(dh);
	143
47e5dc72	144	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	145	fatal("key_verify failed for server_host_key");
	146	key_free(server_host_key);
	147	xfree(signature);
	148
	149	/* save session id */
	150	if (kex->session_id == NULL) {
47e5dc72	151	kex->session_id_len = hashlen;
98a58eda	152	kex->session_id = xmalloc(kex->session_id_len);
	153	memcpy(kex->session_id, hash, kex->session_id_len);
	154	}
	155
47e5dc72	156	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	157	BN_clear_free(shared_secret);
	158	kex_finish(kex);
	159	}