[openssh.git] / kexdhs.c

/* $OpenBSD: kexdhs.c,v 1.6 2006/07/22 20:48:23 stevesk Exp $ */
/*
 * 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 "monitor_wrap.h"

void
kexdh_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	DH *dh;
	Key *server_host_key;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, kout, hashlen;
	u_int slen;

	/* generate server DH public key */
	switch (kex->kex_type) {
	case KEX_DH_GRP1_SHA1:
		dh = dh_new_group1();
		break;
	case KEX_DH_GRP14_SHA1:
		dh = dh_new_group14();
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEXDH_INIT");
	packet_read_expect(SSH2_MSG_KEXDH_INIT);

	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);

	/* 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("kexdh_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);

	/* calc H */
	kex_dh_hash(
	    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,
	    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 */
	packet_start(SSH2_MSG_KEXDH_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
00146caa	1	/* $OpenBSD: kexdhs.c,v 1.6 2006/07/22 20:48:23 stevesk Exp $ */
98a58eda	2	/*
	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"
98a58eda	27
00146caa	28	#include <string.h>
00146caa	29
98a58eda	30	#include "xmalloc.h"
	31	#include "key.h"
	32	#include "kex.h"
	33	#include "log.h"
	34	#include "packet.h"
	35	#include "dh.h"
	36	#include "ssh2.h"
	37	#include "monitor_wrap.h"
	38
	39	void
	40	kexdh_server(Kex *kex)
	41	{
	42	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	43	DH *dh;
	44	Key *server_host_key;
	45	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	46	u_int sbloblen, klen, kout, hashlen;
98a58eda	47	u_int slen;
	48
	49	/* generate server DH public key */
41e5bd9a	50	switch (kex->kex_type) {
	51	case KEX_DH_GRP1_SHA1:
	52	dh = dh_new_group1();
	53	break;
	54	case KEX_DH_GRP14_SHA1:
	55	dh = dh_new_group14();
	56	break;
	57	default:
	58	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	59	}
98a58eda	60	dh_gen_key(dh, kex->we_need * 8);
	61
	62	debug("expecting SSH2_MSG_KEXDH_INIT");
	63	packet_read_expect(SSH2_MSG_KEXDH_INIT);
	64
	65	if (kex->load_host_key == NULL)
	66	fatal("Cannot load hostkey");
	67	server_host_key = kex->load_host_key(kex->hostkey_type);
	68	if (server_host_key == NULL)
	69	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	70
	71	/* key, cert */
	72	if ((dh_client_pub = BN_new()) == NULL)
	73	fatal("dh_client_pub == NULL");
	74	packet_get_bignum2(dh_client_pub);
	75	packet_check_eom();
	76
	77	#ifdef DEBUG_KEXDH
	78	fprintf(stderr, "dh_client_pub= ");
	79	BN_print_fp(stderr, dh_client_pub);
	80	fprintf(stderr, "\n");
	81	debug("bits %d", BN_num_bits(dh_client_pub));
	82	#endif
	83
	84	#ifdef DEBUG_KEXDH
	85	DHparams_print_fp(stderr, dh);
	86	fprintf(stderr, "pub= ");
	87	BN_print_fp(stderr, dh->pub_key);
	88	fprintf(stderr, "\n");
	89	#endif
	90	if (!dh_pub_is_valid(dh, dh_client_pub))
	91	packet_disconnect("bad client public DH value");
	92
	93	klen = DH_size(dh);
	94	kbuf = xmalloc(klen);
	95	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	96	#ifdef DEBUG_KEXDH
	97	dump_digest("shared secret", kbuf, kout);
	98	#endif
	99	if ((shared_secret = BN_new()) == NULL)
	100	fatal("kexdh_server: BN_new failed");
	101	BN_bin2bn(kbuf, kout, shared_secret);
	102	memset(kbuf, 0, klen);
	103	xfree(kbuf);
	104
	105	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	106
	107	/* calc H */
47e5dc72	108	kex_dh_hash(
98a58eda	109	kex->client_version_string,
	110	kex->server_version_string,
	111	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	112	buffer_ptr(&kex->my), buffer_len(&kex->my),
	113	server_host_key_blob, sbloblen,
	114	dh_client_pub,
	115	dh->pub_key,
47e5dc72	116	shared_secret,
47e5dc72	117	&hash, &hashlen
98a58eda	118	);
	119	BN_clear_free(dh_client_pub);
	120
	121	/* save session id := H */
98a58eda	122	if (kex->session_id == NULL) {
47e5dc72	123	kex->session_id_len = hashlen;
98a58eda	124	kex->session_id = xmalloc(kex->session_id_len);
	125	memcpy(kex->session_id, hash, kex->session_id_len);
	126	}
	127
	128	/* sign H */
47e5dc72	129	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
98a58eda	130
	131	/* destroy_sensitive_data(); */
	132
	133	/* send server hostkey, DH pubkey 'f' and singed H */
	134	packet_start(SSH2_MSG_KEXDH_REPLY);
	135	packet_put_string(server_host_key_blob, sbloblen);
	136	packet_put_bignum2(dh->pub_key); /* f */
	137	packet_put_string(signature, slen);
	138	packet_send();
	139
	140	xfree(signature);
	141	xfree(server_host_key_blob);
	142	/* have keys, free DH */
	143	DH_free(dh);
	144
47e5dc72	145	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	146	BN_clear_free(shared_secret);
	147	kex_finish(kex);
	148	}