[openssh.git] / kexgexs.c

/* $OpenBSD: kexgexs.c,v 1.7 2006/08/01 23:22:47 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 <sys/param.h>

#include <stdio.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"
#include "monitor_wrap.h"

void
kexgex_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	Key *server_host_key;
	DH *dh;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, kout, slen, hashlen;
	int min = -1, max = -1, nbits = -1, type;

	if (kex->load_host_key == NULL)
		fatal("Cannot load hostkey");
	server_host_key = kex->load_host_key(kex->hostkey_type);
	if (server_host_key == NULL)
		fatal("Unsupported hostkey type %d", kex->hostkey_type);

	type = packet_read();
	switch (type) {
	case SSH2_MSG_KEX_DH_GEX_REQUEST:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
		min = packet_get_int();
		nbits = packet_get_int();
		max = packet_get_int();
		min = MAX(DH_GRP_MIN, min);
		max = MIN(DH_GRP_MAX, max);
		break;
	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
		nbits = packet_get_int();
		min = DH_GRP_MIN;
		max = DH_GRP_MAX;
		/* unused for old GEX */
		break;
	default:
		fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	}
	packet_check_eom();

	if (max < min || nbits < min || max < nbits)
		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
		    min, nbits, max);

	/* Contact privileged parent */
	dh = PRIVSEP(choose_dh(min, nbits, max));
	if (dh == NULL)
		packet_disconnect("Protocol error: no matching DH grp found");

	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	packet_put_bignum2(dh->p);
	packet_put_bignum2(dh->g);
	packet_send();

	/* flush */
	packet_write_wait();

	/* Compute our exchange value in parallel with the client */
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);

	/* key, cert */
	if ((dh_client_pub = BN_new()) == NULL)
		fatal("dh_client_pub == NULL");
	packet_get_bignum2(dh_client_pub);
	packet_check_eom();

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_client_pub= ");
	BN_print_fp(stderr, dh_client_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_client_pub));
#endif

#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif
	if (!dh_pub_is_valid(dh, dh_client_pub))
		packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	kout = DH_compute_key(kbuf, dh_client_pub, dh);
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexgex_server: BN_new failed");
	BN_bin2bn(kbuf, kout, shared_secret);
	memset(kbuf, 0, klen);
	xfree(kbuf);

	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);

	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
		min = max = -1;

	/* calc H */
	kexgex_hash(
	    kex->evp_md,
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    server_host_key_blob, sbloblen,
	    min, nbits, max,
	    dh->p, dh->g,
	    dh_client_pub,
	    dh->pub_key,
	    shared_secret,
	    &hash, &hashlen
	);
	BN_clear_free(dh_client_pub);

	/* save session id := H */
	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);
	}

	/* sign H */
	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));

	/* destroy_sensitive_data(); */

	/* send server hostkey, DH pubkey 'f' and singed H */
	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
	packet_put_string(server_host_key_blob, sbloblen);
	packet_put_bignum2(dh->pub_key);	/* f */
	packet_put_string(signature, slen);
	packet_send();

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

	kex_derive_keys(kex, hash, hashlen, shared_secret);
	BN_clear_free(shared_secret);

	kex_finish(kex);
}
Commit	Line	Data
cf851879	1	/* $OpenBSD: kexgexs.c,v 1.7 2006/08/01 23:22:47 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
536c14e8	29	#include <sys/param.h>
536c14e8	30
cf851879	31	#include <stdio.h>
00146caa	32	#include <string.h>
00146caa	33
98a58eda	34	#include "xmalloc.h"
	35	#include "key.h"
	36	#include "kex.h"
	37	#include "log.h"
	38	#include "packet.h"
	39	#include "dh.h"
	40	#include "ssh2.h"
	41	#include "compat.h"
	42	#include "monitor_wrap.h"
	43
	44	void
	45	kexgex_server(Kex *kex)
	46	{
	47	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	48	Key *server_host_key;
	49	DH *dh;
	50	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	51	u_int sbloblen, klen, kout, slen, hashlen;
98a58eda	52	int min = -1, max = -1, nbits = -1, type;
	53
	54	if (kex->load_host_key == NULL)
	55	fatal("Cannot load hostkey");
	56	server_host_key = kex->load_host_key(kex->hostkey_type);
	57	if (server_host_key == NULL)
	58	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	59
	60	type = packet_read();
	61	switch (type) {
	62	case SSH2_MSG_KEX_DH_GEX_REQUEST:
	63	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
	64	min = packet_get_int();
	65	nbits = packet_get_int();
	66	max = packet_get_int();
	67	min = MAX(DH_GRP_MIN, min);
	68	max = MIN(DH_GRP_MAX, max);
	69	break;
	70	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
	71	debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
	72	nbits = packet_get_int();
	73	min = DH_GRP_MIN;
	74	max = DH_GRP_MAX;
	75	/* unused for old GEX */
	76	break;
	77	default:
	78	fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	79	}
	80	packet_check_eom();
	81
	82	if (max < min \|\| nbits < min \|\| max < nbits)
	83	fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
	84	min, nbits, max);
	85
	86	/* Contact privileged parent */
	87	dh = PRIVSEP(choose_dh(min, nbits, max));
	88	if (dh == NULL)
	89	packet_disconnect("Protocol error: no matching DH grp found");
	90
	91	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	92	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	93	packet_put_bignum2(dh->p);
	94	packet_put_bignum2(dh->g);
	95	packet_send();
	96
	97	/* flush */
	98	packet_write_wait();
	99
	100	/* Compute our exchange value in parallel with the client */
	101	dh_gen_key(dh, kex->we_need * 8);
	102
	103	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	104	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
	105
	106	/* key, cert */
	107	if ((dh_client_pub = BN_new()) == NULL)
	108	fatal("dh_client_pub == NULL");
	109	packet_get_bignum2(dh_client_pub);
	110	packet_check_eom();
	111
	112	#ifdef DEBUG_KEXDH
	113	fprintf(stderr, "dh_client_pub= ");
	114	BN_print_fp(stderr, dh_client_pub);
	115	fprintf(stderr, "\n");
116	debug("bits %d", BN_num_bits(dh_client_pub));
117	#endif
118
119	#ifdef DEBUG_KEXDH
120	DHparams_print_fp(stderr, dh);
121	fprintf(stderr, "pub= ");
122	BN_print_fp(stderr, dh->pub_key);
123	fprintf(stderr, "\n");
124	#endif
125	if (!dh_pub_is_valid(dh, dh_client_pub))
126	packet_disconnect("bad client public DH value");
127
128	klen = DH_size(dh);
129	kbuf = xmalloc(klen);
130	kout = DH_compute_key(kbuf, dh_client_pub, dh);
131	#ifdef DEBUG_KEXDH
132	dump_digest("shared secret", kbuf, kout);
133	#endif
134	if ((shared_secret = BN_new()) == NULL)
135	fatal("kexgex_server: BN_new failed");
136	BN_bin2bn(kbuf, kout, shared_secret);
137	memset(kbuf, 0, klen);
138	xfree(kbuf);
139
140	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
141
142	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
143	min = max = -1;
144
47e5dc72	145	/* calc H */
	146	kexgex_hash(
	147	kex->evp_md,
98a58eda	148	kex->client_version_string,
	149	kex->server_version_string,
	150	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	151	buffer_ptr(&kex->my), buffer_len(&kex->my),
	152	server_host_key_blob, sbloblen,
	153	min, nbits, max,
	154	dh->p, dh->g,
	155	dh_client_pub,
	156	dh->pub_key,
47e5dc72	157	shared_secret,
47e5dc72	158	&hash, &hashlen
98a58eda	159	);
	160	BN_clear_free(dh_client_pub);
	161
	162	/* save session id := H */
98a58eda	163	if (kex->session_id == NULL) {
47e5dc72	164	kex->session_id_len = hashlen;
98a58eda	165	kex->session_id = xmalloc(kex->session_id_len);
	166	memcpy(kex->session_id, hash, kex->session_id_len);
	167	}
	168
	169	/* sign H */
47e5dc72	170	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
98a58eda	171
	172	/* destroy_sensitive_data(); */
	173
	174	/* send server hostkey, DH pubkey 'f' and singed H */
	175	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
	176	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
	177	packet_put_string(server_host_key_blob, sbloblen);
	178	packet_put_bignum2(dh->pub_key); /* f */
	179	packet_put_string(signature, slen);
	180	packet_send();
	181
	182	xfree(signature);
	183	xfree(server_host_key_blob);
	184	/* have keys, free DH */
	185	DH_free(dh);
	186
47e5dc72	187	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	188	BN_clear_free(shared_secret);
	189
	190	kex_finish(kex);
	191	}