/* $OpenBSD: kexdhc.c,v 1.13 2013/05/17 00:13:13 djm 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 <stdio.h>

#include <string.h>

#include <signal.h>

#include "../openssl/include/openssl/dh.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"

void

kexdh_client(Kex *kex)

{

BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;

DH *dh;

Key *server_host_key;

u_char *server_host_key_blob = NULL, *signature = NULL;

u_char *kbuf, *hash;

u_int klen, slen, sbloblen, hashlen;

int kout;

/* generate and send 'e', client 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);

packet_start(SSH2_MSG_KEXDH_INIT);

packet_put_bignum2(dh->pub_key);

packet_send();

debug("sending SSH2_MSG_KEXDH_INIT");

#ifdef DEBUG_KEXDH

DHparams_print_fp(stderr, dh);

fprintf(stderr, "pub= ");

BN_print_fp(stderr, dh->pub_key);

fprintf(stderr, "\n");

#endif

debug("expecting SSH2_MSG_KEXDH_REPLY");

packet_read_expect(SSH2_MSG_KEXDH_REPLY);

/* key, cert */

server_host_key_blob = packet_get_string(&sbloblen);

server_host_key = key_from_blob(server_host_key_blob, sbloblen);

if (server_host_key == NULL)

fatal("cannot decode server_host_key_blob");

if (server_host_key->type != kex->hostkey_type)

fatal("type mismatch for decoded server_host_key_blob");

if (kex->verify_host_key == NULL)

fatal("cannot verify server_host_key");

if (kex->verify_host_key(server_host_key) == -1)

fatal("server_host_key verification failed");

/* DH parameter f, server public DH key */

if ((dh_server_pub = BN_new()) == NULL)

fatal("dh_server_pub == NULL");

packet_get_bignum2(dh_server_pub);

#ifdef DEBUG_KEXDH

fprintf(stderr, "dh_server_pub= ");

BN_print_fp(stderr, dh_server_pub);

fprintf(stderr, "\n");

debug("bits %d", BN_num_bits(dh_server_pub));

#endif

/* signed H */

signature = packet_get_string(&slen);

packet_check_eom();

if (!dh_pub_is_valid(dh, dh_server_pub))

packet_disconnect("bad server public DH value");

klen = DH_size(dh);

kbuf = xmalloc(klen);

if ((kout = DH_compute_key(kbuf, dh_server_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_client: BN_new failed");

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

fatal("kexdh_client: BN_bin2bn failed");

memset(kbuf, 0, klen);

free(kbuf);

/* calc and verify H */

kex_dh_hash(

kex->client_version_string,

kex->server_version_string,

buffer_ptr(&kex->my), buffer_len(&kex->my),

buffer_ptr(&kex->peer), buffer_len(&kex->peer),

server_host_key_blob, sbloblen,

dh->pub_key,

dh_server_pub,

shared_secret,

&hash, &hashlen

);

free(server_host_key_blob);

BN_clear_free(dh_server_pub);

DH_free(dh);

if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)

fatal("key_verify failed for server_host_key");

key_free(server_host_key);

free(signature);

/* save session id */

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);

}

kex_derive_keys(kex, hash, hashlen, shared_secret);

BN_clear_free(shared_secret);

kex_finish(kex);

}