[openssh.git] / kexgexc.c

/* $OpenBSD: kexgexc.c,v 1.9 2006/08/03 03:34:42 deraadt 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 <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, 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
31652869	1	/* $OpenBSD: kexgexc.c,v 1.9 2006/08/03 03:34:42 deraadt 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
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	#include "compat.h"
	45
	46	void
	47	kexgex_client(Kex *kex)
	48	{
	49	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	50	BIGNUM p = NULL, g = NULL;
	51	Key *server_host_key;
	52	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	53	u_int klen, kout, slen, sbloblen, hashlen;
98a58eda	54	int min, max, nbits;
	55	DH *dh;
	56
	57	nbits = dh_estimate(kex->we_need * 8);
	58
	59	if (datafellows & SSH_OLD_DHGEX) {
98a58eda	60	/* Old GEX request */
	61	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
	62	packet_put_int(nbits);
	63	min = DH_GRP_MIN;
	64	max = DH_GRP_MAX;
98a58eda	65
5acd7dc1	66	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
5acd7dc1	67	} else {
98a58eda	68	/* New GEX request */
	69	min = DH_GRP_MIN;
	70	max = DH_GRP_MAX;
	71	packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
	72	packet_put_int(min);
	73	packet_put_int(nbits);
	74	packet_put_int(max);
5acd7dc1	75
	76	debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
	77	min, nbits, max);
98a58eda	78	}
	79	#ifdef DEBUG_KEXDH
	80	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
	81	min, nbits, max);
	82	#endif
	83	packet_send();
	84
	85	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
	86	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
	87
	88	if ((p = BN_new()) == NULL)
	89	fatal("BN_new");
	90	packet_get_bignum2(p);
	91	if ((g = BN_new()) == NULL)
	92	fatal("BN_new");
	93	packet_get_bignum2(g);
	94	packet_check_eom();
	95
	96	if (BN_num_bits(p) < min \|\| BN_num_bits(p) > max)
	97	fatal("DH_GEX group out of range: %d !< %d !< %d",
	98	min, BN_num_bits(p), max);
	99
	100	dh = dh_new_group(g, p);
	101	dh_gen_key(dh, kex->we_need * 8);
	102
	103	#ifdef DEBUG_KEXDH
	104	DHparams_print_fp(stderr, dh);
	105	fprintf(stderr, "pub= ");
	106	BN_print_fp(stderr, dh->pub_key);
	107	fprintf(stderr, "\n");
	108	#endif
	109
	110	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
	111	/* generate and send 'e', client DH public key */
	112	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
	113	packet_put_bignum2(dh->pub_key);
	114	packet_send();
	115
	116	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
	117	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
	118
	119	/* key, cert */
	120	server_host_key_blob = packet_get_string(&sbloblen);
	121	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	122	if (server_host_key == NULL)
	123	fatal("cannot decode server_host_key_blob");
	124	if (server_host_key->type != kex->hostkey_type)
	125	fatal("type mismatch for decoded server_host_key_blob");
	126	if (kex->verify_host_key == NULL)
	127	fatal("cannot verify server_host_key");
	128	if (kex->verify_host_key(server_host_key) == -1)
	129	fatal("server_host_key verification failed");
	130
18c60a0b	131	/* DH parameter f, server public DH key */
98a58eda	132	if ((dh_server_pub = BN_new()) == NULL)
	133	fatal("dh_server_pub == NULL");
	134	packet_get_bignum2(dh_server_pub);
	135
	136	#ifdef DEBUG_KEXDH
	137	fprintf(stderr, "dh_server_pub= ");
	138	BN_print_fp(stderr, dh_server_pub);
	139	fprintf(stderr, "\n");
	140	debug("bits %d", BN_num_bits(dh_server_pub));
	141	#endif
	142
	143	/* signed H */
	144	signature = packet_get_string(&slen);
	145	packet_check_eom();
	146
	147	if (!dh_pub_is_valid(dh, dh_server_pub))
	148	packet_disconnect("bad server public DH value");
	149
	150	klen = DH_size(dh);
	151	kbuf = xmalloc(klen);
	152	kout = DH_compute_key(kbuf, dh_server_pub, dh);
	153	#ifdef DEBUG_KEXDH
	154	dump_digest("shared secret", kbuf, kout);
	155	#endif
	156	if ((shared_secret = BN_new()) == NULL)
	157	fatal("kexgex_client: BN_new failed");
	158	BN_bin2bn(kbuf, kout, shared_secret);
	159	memset(kbuf, 0, klen);
	160	xfree(kbuf);
	161
	162	if (datafellows & SSH_OLD_DHGEX)
	163	min = max = -1;
	164
	165	/* calc and verify H */
47e5dc72	166	kexgex_hash(
47e5dc72	167	kex->evp_md,
98a58eda	168	kex->client_version_string,
	169	kex->server_version_string,
	170	buffer_ptr(&kex->my), buffer_len(&kex->my),
	171	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	172	server_host_key_blob, sbloblen,
	173	min, nbits, max,
	174	dh->p, dh->g,
	175	dh->pub_key,
	176	dh_server_pub,
47e5dc72	177	shared_secret,
47e5dc72	178	&hash, &hashlen
98a58eda	179	);
47e5dc72	180
98a58eda	181	/* have keys, free DH */
	182	DH_free(dh);
	183	xfree(server_host_key_blob);
	184	BN_clear_free(dh_server_pub);
	185
47e5dc72	186	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
98a58eda	187	fatal("key_verify failed for server_host_key");
	188	key_free(server_host_key);
	189	xfree(signature);
	190
	191	/* save session id */
	192	if (kex->session_id == NULL) {
47e5dc72	193	kex->session_id_len = hashlen;
98a58eda	194	kex->session_id = xmalloc(kex->session_id_len);
	195	memcpy(kex->session_id, hash, kex->session_id_len);
	196	}
47e5dc72	197	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	198	BN_clear_free(shared_secret);
	199
	200	kex_finish(kex);
	201	}