[openssh.git] / kexgexc.c

/* $OpenBSD: kexgexc.c,v 1.11 2006/11/06 21:25:28 markus 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 <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"
#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, slen, sbloblen, hashlen;
	int kout;
	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);
	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("kexgex_client: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexgex_client: BN_bin2bn failed");
	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
e516451d	1	/* $OpenBSD: kexgexc.c,v 1.11 2006/11/06 21:25:28 markus 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
31652869	29	#include <sys/types.h>
31652869	30
24436b92	31	#include <stdarg.h>
cf851879	32	#include <stdio.h>
00146caa	33	#include <string.h>
31652869	34	#include <signal.h>
00146caa	35
98a58eda	36	#include "xmalloc.h"
31652869	37	#include "buffer.h"
98a58eda	38	#include "key.h"
31652869	39	#include "cipher.h"
98a58eda	40	#include "kex.h"
	41	#include "log.h"
	42	#include "packet.h"
	43	#include "dh.h"
	44	#include "ssh2.h"
	45	#include "compat.h"
	46
	47	void
	48	kexgex_client(Kex *kex)
	49	{
	50	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	51	BIGNUM p = NULL, g = NULL;
	52	Key *server_host_key;
	53	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
8e8b473c	54	u_int klen, slen, sbloblen, hashlen;
8e8b473c	55	int kout;
98a58eda	56	int min, max, nbits;
	57	DH *dh;
	58
	59	nbits = dh_estimate(kex->we_need * 8);
	60
	61	if (datafellows & SSH_OLD_DHGEX) {
98a58eda	62	/* Old GEX request */
	63	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
	64	packet_put_int(nbits);
	65	min = DH_GRP_MIN;
	66	max = DH_GRP_MAX;
98a58eda	67
5acd7dc1	68	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
5acd7dc1	69	} else {
98a58eda	70	/* New GEX request */
	71	min = DH_GRP_MIN;
	72	max = DH_GRP_MAX;
	73	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
	74	packet_put_int(min);
	75	packet_put_int(nbits);
	76	packet_put_int(max);
5acd7dc1	77
	78	debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
	79	min, nbits, max);
98a58eda	80	}
	81	#ifdef DEBUG_KEXDH
	82	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	83	min, nbits, max);
	84	#endif
	85	packet_send();
	86
	87	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
	88	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
	89
	90	if ((p = BN_new()) == NULL)
	91	fatal("BN_new");
	92	packet_get_bignum2(p);
	93	if ((g = BN_new()) == NULL)
	94	fatal("BN_new");
	95	packet_get_bignum2(g);
	96	packet_check_eom();
	97
	98	if (BN_num_bits(p) < min \|\| BN_num_bits(p) > max)
	99	fatal("DH_GEX group out of range: %d !< %d !< %d",
	100	min, BN_num_bits(p), max);
	101
	102	dh = dh_new_group(g, p);
	103	dh_gen_key(dh, kex->we_need * 8);
	104
	105	#ifdef DEBUG_KEXDH
	106	DHparams_print_fp(stderr, dh);
	107	fprintf(stderr, "pub= ");
	108	BN_print_fp(stderr, dh->pub_key);
	109	fprintf(stderr, "\n");
	110	#endif
	111
	112	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	113	/* generate and send 'e', client DH public key */
	114	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	115	packet_put_bignum2(dh->pub_key);
	116	packet_send();
	117
	118	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
	119	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
	120
	121	/* key, cert */
	122	server_host_key_blob = packet_get_string(&sbloblen);
	123	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	124	if (server_host_key == NULL)
	125	fatal("cannot decode server_host_key_blob");
	126	if (server_host_key->type != kex->hostkey_type)
	127	fatal("type mismatch for decoded server_host_key_blob");
	128	if (kex->verify_host_key == NULL)
	129	fatal("cannot verify server_host_key");
	130	if (kex->verify_host_key(server_host_key) == -1)
	131	fatal("server_host_key verification failed");
	132
18c60a0b	133	/* DH parameter f, server public DH key */
98a58eda	134	if ((dh_server_pub = BN_new()) == NULL)
	135	fatal("dh_server_pub == NULL");
	136	packet_get_bignum2(dh_server_pub);
	137
	138	#ifdef DEBUG_KEXDH
	139	fprintf(stderr, "dh_server_pub= ");
	140	BN_print_fp(stderr, dh_server_pub);
	141	fprintf(stderr, "\n");
	142	debug("bits %d", BN_num_bits(dh_server_pub));
	143	#endif
	144
	145	/* signed H */
	146	signature = packet_get_string(&slen);
	147	packet_check_eom();
	148
	149	if (!dh_pub_is_valid(dh, dh_server_pub))
	150	packet_disconnect("bad server public DH value");
	151
	152	klen = DH_size(dh);
	153	kbuf = xmalloc(klen);
8e8b473c	154	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
8e8b473c	155	fatal("DH_compute_key: failed");
98a58eda	156	#ifdef DEBUG_KEXDH
	157	dump_digest("shared secret", kbuf, kout);
	158	#endif
	159	if ((shared_secret = BN_new()) == NULL)
	160	fatal("kexgex_client: BN_new failed");
e516451d	161	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
e516451d	162	fatal("kexgex_client: BN_bin2bn failed");
98a58eda	163	memset(kbuf, 0, klen);
	164	xfree(kbuf);
	165
	166	if (datafellows & SSH_OLD_DHGEX)
	167	min = max = -1;
	168
	169	/* calc and verify H */
47e5dc72	170	kexgex_hash(
47e5dc72	171	kex->evp_md,
98a58eda	172	kex->client_version_string,
	173	kex->server_version_string,
	174	buffer_ptr(&kex->my), buffer_len(&kex->my),
	175	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	176	server_host_key_blob, sbloblen,
	177	min, nbits, max,
	178	dh->p, dh->g,
	179	dh->pub_key,
	180	dh_server_pub,
47e5dc72	181	shared_secret,
47e5dc72	182	&hash, &hashlen
98a58eda	183	);
47e5dc72	184
98a58eda	185	/* have keys, free DH */
	186	DH_free(dh);
	187	xfree(server_host_key_blob);
	188	BN_clear_free(dh_server_pub);
	189
47e5dc72	190	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	191	fatal("key_verify failed for server_host_key");
	192	key_free(server_host_key);
	193	xfree(signature);
	194
	195	/* save session id */
	196	if (kex->session_id == NULL) {
47e5dc72	197	kex->session_id_len = hashlen;
98a58eda	198	kex->session_id = xmalloc(kex->session_id_len);
	199	memcpy(kex->session_id, hash, kex->session_id_len);
	200	}
47e5dc72	201	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	202	BN_clear_free(shared_secret);
	203
	204	kex_finish(kex);
	205	}