[openssh.git] / kexdhs.c

/*
 * 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 "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
98a58eda	1	/*
	2	* Copyright (c) 2001 Markus Friedl. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	14	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	15	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	16	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	17	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	18	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	19	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	20	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	21	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	22	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	23	*/
	24
	25	#include "includes.h"
98a58eda	26
	27	#include "xmalloc.h"
	28	#include "key.h"
	29	#include "kex.h"
	30	#include "log.h"
	31	#include "packet.h"
	32	#include "dh.h"
	33	#include "ssh2.h"
	34	#include "monitor_wrap.h"
	35
	36	void
	37	kexdh_server(Kex *kex)
	38	{
	39	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	40	DH *dh;
	41	Key *server_host_key;
	42	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	43	u_int sbloblen, klen, kout, hashlen;
98a58eda	44	u_int slen;
	45
	46	/* generate server DH public key */
41e5bd9a	47	switch (kex->kex_type) {
	48	case KEX_DH_GRP1_SHA1:
	49	dh = dh_new_group1();
	50	break;
	51	case KEX_DH_GRP14_SHA1:
	52	dh = dh_new_group14();
	53	break;
	54	default:
	55	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	56	}
98a58eda	57	dh_gen_key(dh, kex->we_need * 8);
	58
	59	debug("expecting SSH2_MSG_KEXDH_INIT");
	60	packet_read_expect(SSH2_MSG_KEXDH_INIT);
	61
	62	if (kex->load_host_key == NULL)
	63	fatal("Cannot load hostkey");
	64	server_host_key = kex->load_host_key(kex->hostkey_type);
	65	if (server_host_key == NULL)
	66	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	67
	68	/* key, cert */
	69	if ((dh_client_pub = BN_new()) == NULL)
	70	fatal("dh_client_pub == NULL");
	71	packet_get_bignum2(dh_client_pub);
	72	packet_check_eom();
	73
	74	#ifdef DEBUG_KEXDH
	75	fprintf(stderr, "dh_client_pub= ");
	76	BN_print_fp(stderr, dh_client_pub);
	77	fprintf(stderr, "\n");
	78	debug("bits %d", BN_num_bits(dh_client_pub));
	79	#endif
	80
	81	#ifdef DEBUG_KEXDH
	82	DHparams_print_fp(stderr, dh);
	83	fprintf(stderr, "pub= ");
	84	BN_print_fp(stderr, dh->pub_key);
	85	fprintf(stderr, "\n");
	86	#endif
	87	if (!dh_pub_is_valid(dh, dh_client_pub))
	88	packet_disconnect("bad client public DH value");
	89
	90	klen = DH_size(dh);
	91	kbuf = xmalloc(klen);
	92	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	93	#ifdef DEBUG_KEXDH
	94	dump_digest("shared secret", kbuf, kout);
	95	#endif
	96	if ((shared_secret = BN_new()) == NULL)
	97	fatal("kexdh_server: BN_new failed");
	98	BN_bin2bn(kbuf, kout, shared_secret);
	99	memset(kbuf, 0, klen);
	100	xfree(kbuf);
	101
	102	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	103
	104	/* calc H */
47e5dc72	105	kex_dh_hash(
98a58eda	106	kex->client_version_string,
	107	kex->server_version_string,
	108	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	109	buffer_ptr(&kex->my), buffer_len(&kex->my),
	110	server_host_key_blob, sbloblen,
	111	dh_client_pub,
	112	dh->pub_key,
47e5dc72	113	shared_secret,
47e5dc72	114	&hash, &hashlen
98a58eda	115	);
	116	BN_clear_free(dh_client_pub);
	117
	118	/* save session id := H */
98a58eda	119	if (kex->session_id == NULL) {
47e5dc72	120	kex->session_id_len = hashlen;
98a58eda	121	kex->session_id = xmalloc(kex->session_id_len);
	122	memcpy(kex->session_id, hash, kex->session_id_len);
	123	}
	124
	125	/* sign H */
47e5dc72	126	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
98a58eda	127
	128	/* destroy_sensitive_data(); */
	129
	130	/* send server hostkey, DH pubkey 'f' and singed H */
	131	packet_start(SSH2_MSG_KEXDH_REPLY);
	132	packet_put_string(server_host_key_blob, sbloblen);
	133	packet_put_bignum2(dh->pub_key); /* f */
	134	packet_put_string(signature, slen);
	135	packet_send();
	136
	137	xfree(signature);
	138	xfree(server_host_key_blob);
	139	/* have keys, free DH */
	140	DH_free(dh);
	141
47e5dc72	142	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	143	BN_clear_free(shared_secret);
	144	kex_finish(kex);
	145	}