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/* $OpenBSD: kexc25519c.c,v 1.4 2014/01/12 08:13:13 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
* Copyright (c) 2013 Aris Adamantiadis. 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 <stdio.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 "ssh2.h"
void
kexc25519_client(Kex *kex)
{
Key *server_host_key;
u_char client_key[CURVE25519_SIZE];
u_char client_pubkey[CURVE25519_SIZE];
u_char *server_pubkey = NULL;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char *hash;
u_int slen, sbloblen, hashlen;
Buffer shared_secret;
kexc25519_keygen(client_key, client_pubkey);
packet_start(SSH2_MSG_KEX_ECDH_INIT);
packet_put_string(client_pubkey, sizeof(client_pubkey));
packet_send();
debug("sending SSH2_MSG_KEX_ECDH_INIT");
#ifdef DEBUG_KEXECDH
dump_digest("client private key:", client_key, sizeof(client_key));
#endif
debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
/* hostkey */
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");
/* Q_S, server public key */
server_pubkey = packet_get_string(&slen);
if (slen != CURVE25519_SIZE)
fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
#ifdef DEBUG_KEXECDH
dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_check_eom();
buffer_init(&shared_secret);
kexc25519_shared_key(client_key, server_pubkey, &shared_secret);
/* calc and verify H */
kex_c25519_hash(
kex->hash_alg,
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,
client_pubkey,
server_pubkey,
buffer_ptr(&shared_secret), buffer_len(&shared_secret),
&hash, &hashlen
);
free(server_host_key_blob);
free(server_pubkey);
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,
buffer_ptr(&shared_secret), buffer_len(&shared_secret));
buffer_free(&shared_secret);
kex_finish(kex);
}
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