[openssh.git] / kexgexc.c

/*
 * 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"
RCSID("$OpenBSD: kexgexc.c,v 1.1 2003/02/16 17:09:57 markus Exp $");

#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;
	int min, max, nbits;
	DH *dh;

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

	if (datafellows & SSH_OLD_DHGEX) {
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");

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

		/* 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);
	}
#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 paramter 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 */
	hash = kexgex_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,
	    min, nbits, max,
	    dh->p, dh->g,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret
	);
	/* 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, 20) != 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 = 20;
		kex->session_id = xmalloc(kex->session_id_len);
		memcpy(kex->session_id, hash, kex->session_id_len);
	}
	kex_derive_keys(kex, hash, shared_secret);
	BN_clear_free(shared_secret);

	kex_finish(kex);
}
Commit	Line	Data
98a58eda	1	/*
	2	* Copyright (c) 2000 Niels Provos. All rights reserved.
	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"
	27	RCSID("$OpenBSD: kexgexc.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
	28
	29	#include "xmalloc.h"
	30	#include "key.h"
	31	#include "kex.h"
	32	#include "log.h"
	33	#include "packet.h"
	34	#include "dh.h"
	35	#include "ssh2.h"
	36	#include "compat.h"
	37
	38	void
	39	kexgex_client(Kex *kex)
	40	{
	41	BIGNUM dh_server_pub = NULL, shared_secret = NULL;
	42	BIGNUM p = NULL, g = NULL;
	43	Key *server_host_key;
	44	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	45	u_int klen, kout, slen, sbloblen;
	46	int min, max, nbits;
	47	DH *dh;
	48
	49	nbits = dh_estimate(kex->we_need * 8);
	50
	51	if (datafellows & SSH_OLD_DHGEX) {
	52	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
	53
	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;
	59	} else {
	60	debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
	61
	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);
69	}
70	#ifdef DEBUG_KEXDH
71	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
72	min, nbits, max);
73	#endif
74	packet_send();
75
76	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
77	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
78
79	if ((p = BN_new()) == NULL)
80	fatal("BN_new");
81	packet_get_bignum2(p);
82	if ((g = BN_new()) == NULL)
83	fatal("BN_new");
84	packet_get_bignum2(g);
85	packet_check_eom();
86
87	if (BN_num_bits(p) < min \|\| BN_num_bits(p) > max)
88	fatal("DH_GEX group out of range: %d !< %d !< %d",
89	min, BN_num_bits(p), max);
90
91	dh = dh_new_group(g, p);
92	dh_gen_key(dh, kex->we_need * 8);
93
94	#ifdef DEBUG_KEXDH
95	DHparams_print_fp(stderr, dh);
96	fprintf(stderr, "pub= ");
97	BN_print_fp(stderr, dh->pub_key);
98	fprintf(stderr, "\n");
99	#endif
100
101	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
102	/* generate and send 'e', client DH public key */
103	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
104	packet_put_bignum2(dh->pub_key);
105	packet_send();
106
107	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
108	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
109
110	/* key, cert */
111	server_host_key_blob = packet_get_string(&sbloblen);
112	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
113	if (server_host_key == NULL)
114	fatal("cannot decode server_host_key_blob");
115	if (server_host_key->type != kex->hostkey_type)
116	fatal("type mismatch for decoded server_host_key_blob");
117	if (kex->verify_host_key == NULL)
118	fatal("cannot verify server_host_key");
119	if (kex->verify_host_key(server_host_key) == -1)
120	fatal("server_host_key verification failed");
121
122	/* DH paramter f, server public DH key */
123	if ((dh_server_pub = BN_new()) == NULL)
124	fatal("dh_server_pub == NULL");
125	packet_get_bignum2(dh_server_pub);
126
127	#ifdef DEBUG_KEXDH
128	fprintf(stderr, "dh_server_pub= ");
129	BN_print_fp(stderr, dh_server_pub);
130	fprintf(stderr, "\n");
131	debug("bits %d", BN_num_bits(dh_server_pub));
132	#endif
133
134	/* signed H */
135	signature = packet_get_string(&slen);
136	packet_check_eom();
137
138	if (!dh_pub_is_valid(dh, dh_server_pub))
139	packet_disconnect("bad server public DH value");
140
141	klen = DH_size(dh);
142	kbuf = xmalloc(klen);
143	kout = DH_compute_key(kbuf, dh_server_pub, dh);
144	#ifdef DEBUG_KEXDH
145	dump_digest("shared secret", kbuf, kout);
146	#endif
147	if ((shared_secret = BN_new()) == NULL)
148	fatal("kexgex_client: BN_new failed");
149	BN_bin2bn(kbuf, kout, shared_secret);
150	memset(kbuf, 0, klen);
151	xfree(kbuf);
152
153	if (datafellows & SSH_OLD_DHGEX)
154	min = max = -1;
155
156	/* calc and verify H */
157	hash = kexgex_hash(
158	kex->client_version_string,
159	kex->server_version_string,
160	buffer_ptr(&kex->my), buffer_len(&kex->my),
161	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
162	server_host_key_blob, sbloblen,
163	min, nbits, max,
164	dh->p, dh->g,
165	dh->pub_key,
166	dh_server_pub,
167	shared_secret
168	);
169	/* have keys, free DH */
170	DH_free(dh);
171	xfree(server_host_key_blob);
172	BN_clear_free(dh_server_pub);
173
174	if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
175	fatal("key_verify failed for server_host_key");
176	key_free(server_host_key);
177	xfree(signature);
178
179	/* save session id */
180	if (kex->session_id == NULL) {
181	kex->session_id_len = 20;
182	kex->session_id = xmalloc(kex->session_id_len);
183	memcpy(kex->session_id, hash, kex->session_id_len);
184	}
185	kex_derive_keys(kex, hash, shared_secret);
186	BN_clear_free(shared_secret);
187
188	kex_finish(kex);
189	}