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/* $OpenBSD: kexdhs.c,v 1.10 2009/06/21 07:37:15 dtucker 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 <stdarg.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, hashlen, slen;

	int kout;

	/* 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);

	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)

		fatal("DH_compute_key: failed");

#ifdef DEBUG_KEXDH

	dump_digest("shared secret", kbuf, kout);

#endif

	if ((shared_secret = BN_new()) == NULL)

		fatal("kexdh_server: BN_new failed");

	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)

		fatal("kexdh_server: BN_bin2bn failed");

	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 */

	if (PRIVSEP(key_sign(server_host_key, &signature, &slen, hash,

	    hashlen)) < 0)

		fatal("kexdh_server: key_sign failed");

	/* 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);

}