[openssh.git] / kexgexc.c

/* $OpenBSD: kexgexc.c,v 1.7 2006/07/22 20:48:23 stevesk Exp $ */
/*
 * Copyright (c) 2000 Niels Provos.  All rights reserved.
 * 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 <string.h>

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

void
kexgex_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	BIGNUM *p = NULL, *g = NULL;
	Key *server_host_key;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int klen, kout, slen, sbloblen, hashlen;
	int min, max, nbits;
	DH *dh;

	nbits = dh_estimate(kex->we_need * 8);

	if (datafellows & SSH_OLD_DHGEX) {
		/* Old GEX request */
		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
		packet_put_int(nbits);
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;

		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
	} else {
		/* New GEX request */
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;
		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
		packet_put_int(min);
		packet_put_int(nbits);
		packet_put_int(max);

		debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
		    min, nbits, max);
	}
#ifdef DEBUG_KEXDH
	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	    min, nbits, max);
#endif
	packet_send();

	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);

	if ((p = BN_new()) == NULL)
		fatal("BN_new");
	packet_get_bignum2(p);
	if ((g = BN_new()) == NULL)
		fatal("BN_new");
	packet_get_bignum2(g);
	packet_check_eom();

	if (BN_num_bits(p) < min || BN_num_bits(p) > max)
		fatal("DH_GEX group out of range: %d !< %d !< %d",
		    min, BN_num_bits(p), max);

	dh = dh_new_group(g, p);
	dh_gen_key(dh, kex->we_need * 8);

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

	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	/* generate and send 'e', client DH public key */
	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();

	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_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("kexgex_client: BN_new failed");
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	if (datafellows & SSH_OLD_DHGEX)
		min = max = -1;

	/* calc and verify H */
	kexgex_hash(
	    kex->evp_md,
	    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,
	    min, nbits, max,
	    dh->p, dh->g,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret,
	    &hash, &hashlen
	);

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

	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
00146caa	1	/* $OpenBSD: kexgexc.c,v 1.7 2006/07/22 20:48:23 stevesk Exp $ */
98a58eda	2	/*
	3	* Copyright (c) 2000 Niels Provos. All rights reserved.
	4	* Copyright (c) 2001 Markus Friedl. All rights reserved.
	5	*
	6	* Redistribution and use in source and binary forms, with or without
	7	* modification, are permitted provided that the following conditions
	8	* are met:
	9	* 1. Redistributions of source code must retain the above copyright
	10	* notice, this list of conditions and the following disclaimer.
	11	* 2. Redistributions in binary form must reproduce the above copyright
	12	* notice, this list of conditions and the following disclaimer in the
	13	* documentation and/or other materials provided with the distribution.
	14	*
	15	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	16	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	17	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	18	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	19	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	20	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	21	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	22	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	23	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	24	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	25	*/
	26
	27	#include "includes.h"
98a58eda	28
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	#include "compat.h"
	39
	40	void
	41	kexgex_client(Kex *kex)
	42	{
	43	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	44	BIGNUM p = NULL, g = NULL;
	45	Key *server_host_key;
	46	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	47	u_int klen, kout, slen, sbloblen, hashlen;
98a58eda	48	int min, max, nbits;
	49	DH *dh;
	50
	51	nbits = dh_estimate(kex->we_need * 8);
	52
	53	if (datafellows & SSH_OLD_DHGEX) {
98a58eda	54	/* Old GEX request */
	55	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
	56	packet_put_int(nbits);
	57	min = DH_GRP_MIN;
	58	max = DH_GRP_MAX;
98a58eda	59
5acd7dc1	60	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
5acd7dc1	61	} else {
98a58eda	62	/* New GEX request */
	63	min = DH_GRP_MIN;
	64	max = DH_GRP_MAX;
	65	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
	66	packet_put_int(min);
	67	packet_put_int(nbits);
	68	packet_put_int(max);
5acd7dc1	69
	70	debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
	71	min, nbits, max);
98a58eda	72	}
	73	#ifdef DEBUG_KEXDH
	74	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	75	min, nbits, max);
	76	#endif
	77	packet_send();
	78
	79	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
	80	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
	81
	82	if ((p = BN_new()) == NULL)
	83	fatal("BN_new");
	84	packet_get_bignum2(p);
	85	if ((g = BN_new()) == NULL)
	86	fatal("BN_new");
	87	packet_get_bignum2(g);
	88	packet_check_eom();
	89
	90	if (BN_num_bits(p) < min \|\| BN_num_bits(p) > max)
	91	fatal("DH_GEX group out of range: %d !< %d !< %d",
	92	min, BN_num_bits(p), max);
	93
	94	dh = dh_new_group(g, p);
	95	dh_gen_key(dh, kex->we_need * 8);
	96
	97	#ifdef DEBUG_KEXDH
	98	DHparams_print_fp(stderr, dh);
	99	fprintf(stderr, "pub= ");
	100	BN_print_fp(stderr, dh->pub_key);
	101	fprintf(stderr, "\n");
	102	#endif
	103
	104	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	105	/* generate and send 'e', client DH public key */
	106	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	107	packet_put_bignum2(dh->pub_key);
	108	packet_send();
	109
	110	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
	111	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
	112
	113	/* key, cert */
	114	server_host_key_blob = packet_get_string(&sbloblen);
	115	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	116	if (server_host_key == NULL)
	117	fatal("cannot decode server_host_key_blob");
	118	if (server_host_key->type != kex->hostkey_type)
	119	fatal("type mismatch for decoded server_host_key_blob");
	120	if (kex->verify_host_key == NULL)
	121	fatal("cannot verify server_host_key");
	122	if (kex->verify_host_key(server_host_key) == -1)
	123	fatal("server_host_key verification failed");
	124
18c60a0b	125	/* DH parameter f, server public DH key */
98a58eda	126	if ((dh_server_pub = BN_new()) == NULL)
	127	fatal("dh_server_pub == NULL");
	128	packet_get_bignum2(dh_server_pub);
	129
	130	#ifdef DEBUG_KEXDH
	131	fprintf(stderr, "dh_server_pub= ");
	132	BN_print_fp(stderr, dh_server_pub);
	133	fprintf(stderr, "\n");
	134	debug("bits %d", BN_num_bits(dh_server_pub));
	135	#endif
	136
	137	/* signed H */
	138	signature = packet_get_string(&slen);
	139	packet_check_eom();
	140
	141	if (!dh_pub_is_valid(dh, dh_server_pub))
	142	packet_disconnect("bad server public DH value");
	143
	144	klen = DH_size(dh);
	145	kbuf = xmalloc(klen);
	146	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	147	#ifdef DEBUG_KEXDH
	148	dump_digest("shared secret", kbuf, kout);
	149	#endif
	150	if ((shared_secret = BN_new()) == NULL)
	151	fatal("kexgex_client: BN_new failed");
	152	BN_bin2bn(kbuf, kout, shared_secret);
	153	memset(kbuf, 0, klen);
	154	xfree(kbuf);
	155
	156	if (datafellows & SSH_OLD_DHGEX)
	157	min = max = -1;
	158
	159	/* calc and verify H */
47e5dc72	160	kexgex_hash(
47e5dc72	161	kex->evp_md,
98a58eda	162	kex->client_version_string,
	163	kex->server_version_string,
	164	buffer_ptr(&kex->my), buffer_len(&kex->my),
	165	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	166	server_host_key_blob, sbloblen,
	167	min, nbits, max,
	168	dh->p, dh->g,
	169	dh->pub_key,
	170	dh_server_pub,
47e5dc72	171	shared_secret,
47e5dc72	172	&hash, &hashlen
98a58eda	173	);
47e5dc72	174
98a58eda	175	/* have keys, free DH */
	176	DH_free(dh);
	177	xfree(server_host_key_blob);
	178	BN_clear_free(dh_server_pub);
	179
47e5dc72	180	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	181	fatal("key_verify failed for server_host_key");
	182	key_free(server_host_key);
	183	xfree(signature);
	184
	185	/* save session id */
	186	if (kex->session_id == NULL) {
47e5dc72	187	kex->session_id_len = hashlen;
98a58eda	188	kex->session_id = xmalloc(kex->session_id_len);
	189	memcpy(kex->session_id, hash, kex->session_id_len);
	190	}
47e5dc72	191	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	192	BN_clear_free(shared_secret);
	193
	194	kex_finish(kex);
	195	}