[openssh.git] / kexdhs.c

/* $OpenBSD: kexdhs.c,v 1.7 2006/08/03 03:34:42 deraadt 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 <sys/types.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"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#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
31652869	1	/* $OpenBSD: kexdhs.c,v 1.7 2006/08/03 03:34:42 deraadt 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
31652869	28	#include <sys/types.h>
00146caa	29	#include <string.h>
31652869	30	#include <signal.h>
00146caa	31
98a58eda	32	#include "xmalloc.h"
31652869	33	#include "buffer.h"
98a58eda	34	#include "key.h"
31652869	35	#include "cipher.h"
98a58eda	36	#include "kex.h"
	37	#include "log.h"
	38	#include "packet.h"
	39	#include "dh.h"
	40	#include "ssh2.h"
31652869	41	#ifdef GSSAPI
	42	#include "ssh-gss.h"
	43	#endif
98a58eda	44	#include "monitor_wrap.h"
	45
	46	void
	47	kexdh_server(Kex *kex)
	48	{
	49	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	50	DH *dh;
	51	Key *server_host_key;
	52	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
47e5dc72	53	u_int sbloblen, klen, kout, hashlen;
98a58eda	54	u_int slen;
	55
	56	/* generate server DH public key */
41e5bd9a	57	switch (kex->kex_type) {
	58	case KEX_DH_GRP1_SHA1:
	59	dh = dh_new_group1();
	60	break;
	61	case KEX_DH_GRP14_SHA1:
	62	dh = dh_new_group14();
	63	break;
	64	default:
	65	fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	66	}
98a58eda	67	dh_gen_key(dh, kex->we_need * 8);
	68
	69	debug("expecting SSH2_MSG_KEXDH_INIT");
	70	packet_read_expect(SSH2_MSG_KEXDH_INIT);
	71
	72	if (kex->load_host_key == NULL)
	73	fatal("Cannot load hostkey");
	74	server_host_key = kex->load_host_key(kex->hostkey_type);
	75	if (server_host_key == NULL)
	76	fatal("Unsupported hostkey type %d", kex->hostkey_type);
	77
	78	/* key, cert */
	79	if ((dh_client_pub = BN_new()) == NULL)
	80	fatal("dh_client_pub == NULL");
	81	packet_get_bignum2(dh_client_pub);
	82	packet_check_eom();
	83
	84	#ifdef DEBUG_KEXDH
	85	fprintf(stderr, "dh_client_pub= ");
	86	BN_print_fp(stderr, dh_client_pub);
	87	fprintf(stderr, "\n");
	88	debug("bits %d", BN_num_bits(dh_client_pub));
	89	#endif
	90
	91	#ifdef DEBUG_KEXDH
	92	DHparams_print_fp(stderr, dh);
	93	fprintf(stderr, "pub= ");
	94	BN_print_fp(stderr, dh->pub_key);
	95	fprintf(stderr, "\n");
	96	#endif
	97	if (!dh_pub_is_valid(dh, dh_client_pub))
	98	packet_disconnect("bad client public DH value");
	99
	100	klen = DH_size(dh);
	101	kbuf = xmalloc(klen);
	102	kout = DH_compute_key(kbuf, dh_client_pub, dh);
	103	#ifdef DEBUG_KEXDH
	104	dump_digest("shared secret", kbuf, kout);
	105	#endif
	106	if ((shared_secret = BN_new()) == NULL)
	107	fatal("kexdh_server: BN_new failed");
	108	BN_bin2bn(kbuf, kout, shared_secret);
	109	memset(kbuf, 0, klen);
	110	xfree(kbuf);
	111
	112	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
	113
	114	/* calc H */
47e5dc72	115	kex_dh_hash(
98a58eda	116	kex->client_version_string,
	117	kex->server_version_string,
	118	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	119	buffer_ptr(&kex->my), buffer_len(&kex->my),
	120	server_host_key_blob, sbloblen,
	121	dh_client_pub,
	122	dh->pub_key,
47e5dc72	123	shared_secret,
47e5dc72	124	&hash, &hashlen
98a58eda	125	);
	126	BN_clear_free(dh_client_pub);
	127
	128	/* save session id := H */
98a58eda	129	if (kex->session_id == NULL) {
47e5dc72	130	kex->session_id_len = hashlen;
98a58eda	131	kex->session_id = xmalloc(kex->session_id_len);
	132	memcpy(kex->session_id, hash, kex->session_id_len);
	133	}
	134
	135	/* sign H */
47e5dc72	136	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
98a58eda	137
	138	/* destroy_sensitive_data(); */
	139
	140	/* send server hostkey, DH pubkey 'f' and singed H */
	141	packet_start(SSH2_MSG_KEXDH_REPLY);
	142	packet_put_string(server_host_key_blob, sbloblen);
	143	packet_put_bignum2(dh->pub_key); /* f */
	144	packet_put_string(signature, slen);
	145	packet_send();
	146
	147	xfree(signature);
	148	xfree(server_host_key_blob);
	149	/* have keys, free DH */
	150	DH_free(dh);
	151
47e5dc72	152	kex_derive_keys(kex, hash, hashlen, shared_secret);
98a58eda	153	BN_clear_free(shared_secret);
	154	kex_finish(kex);
	155	}