[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"
RCSID("$OpenBSD: kexdhs.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 "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;
	u_int slen;

	/* generate server DH public key */
	dh = dh_new_group1();
	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 */
	hash = 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
	);
	BN_clear_free(dh_client_pub);

	/* save session id := H */
	/* XXX hashlen depends on KEX */
	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);
	}

	/* sign H */
	/* XXX hashlen depends on KEX */
	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));

	/* 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, 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"
	26	RCSID("$OpenBSD: kexdhs.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
	27
	28	#include "xmalloc.h"
	29	#include "key.h"
	30	#include "kex.h"
	31	#include "log.h"
	32	#include "packet.h"
	33	#include "dh.h"
	34	#include "ssh2.h"
	35	#include "monitor_wrap.h"
	36
	37	void
	38	kexdh_server(Kex *kex)
	39	{
	40	BIGNUM shared_secret = NULL, dh_client_pub = NULL;
	41	DH *dh;
	42	Key *server_host_key;
	43	u_char kbuf, hash, signature = NULL, server_host_key_blob = NULL;
	44	u_int sbloblen, klen, kout;
	45	u_int slen;
	46
	47	/* generate server DH public key */
	48	dh = dh_new_group1();
	49	dh_gen_key(dh, kex->we_need * 8);
	50
	51	debug("expecting SSH2_MSG_KEXDH_INIT");
	52	packet_read_expect(SSH2_MSG_KEXDH_INIT);
	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	/* key, cert */
	61	if ((dh_client_pub = BN_new()) == NULL)
	62	fatal("dh_client_pub == NULL");
	63	packet_get_bignum2(dh_client_pub);
	64	packet_check_eom();
65
66	#ifdef DEBUG_KEXDH
67	fprintf(stderr, "dh_client_pub= ");
68	BN_print_fp(stderr, dh_client_pub);
69	fprintf(stderr, "\n");
70	debug("bits %d", BN_num_bits(dh_client_pub));
71	#endif
72
73	#ifdef DEBUG_KEXDH
74	DHparams_print_fp(stderr, dh);
75	fprintf(stderr, "pub= ");
76	BN_print_fp(stderr, dh->pub_key);
77	fprintf(stderr, "\n");
78	#endif
79	if (!dh_pub_is_valid(dh, dh_client_pub))
80	packet_disconnect("bad client public DH value");
81
82	klen = DH_size(dh);
83	kbuf = xmalloc(klen);
84	kout = DH_compute_key(kbuf, dh_client_pub, dh);
85	#ifdef DEBUG_KEXDH
86	dump_digest("shared secret", kbuf, kout);
87	#endif
88	if ((shared_secret = BN_new()) == NULL)
89	fatal("kexdh_server: BN_new failed");
90	BN_bin2bn(kbuf, kout, shared_secret);
91	memset(kbuf, 0, klen);
92	xfree(kbuf);
93
94	key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
95
96	/* calc H */
97	hash = kex_dh_hash(
98	kex->client_version_string,
99	kex->server_version_string,
100	buffer_ptr(&kex->peer), buffer_len(&kex->peer),
101	buffer_ptr(&kex->my), buffer_len(&kex->my),
102	server_host_key_blob, sbloblen,
103	dh_client_pub,
104	dh->pub_key,
105	shared_secret
106	);
107	BN_clear_free(dh_client_pub);
108
109	/* save session id := H */
110	/* XXX hashlen depends on KEX */
111	if (kex->session_id == NULL) {
112	kex->session_id_len = 20;
113	kex->session_id = xmalloc(kex->session_id_len);
114	memcpy(kex->session_id, hash, kex->session_id_len);
115	}
116
117	/* sign H */
118	/* XXX hashlen depends on KEX */
119	PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
120
121	/* destroy_sensitive_data(); */
122
123	/* send server hostkey, DH pubkey 'f' and singed H */
124	packet_start(SSH2_MSG_KEXDH_REPLY);
125	packet_put_string(server_host_key_blob, sbloblen);
126	packet_put_bignum2(dh->pub_key); /* f */
127	packet_put_string(signature, slen);
128	packet_send();
129
130	xfree(signature);
131	xfree(server_host_key_blob);
132	/* have keys, free DH */
133	DH_free(dh);
134
135	kex_derive_keys(kex, hash, shared_secret);
136	BN_clear_free(shared_secret);
137	kex_finish(kex);
138	}