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/* $OpenBSD: kexkems.c,v 1.4 2019/01/21 10:29:56 djm Exp $ */
/*
* Copyright (c) 2019 Markus Friedl. All rights reserved.
*
* 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 <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include "sshkey.h"
#include "digest.h"
#include "kex.h"
#include "log.h"
#include "packet.h"
#include "ssh2.h"
#include "sshbuf.h"
#include "ssherr.h"
static int input_kex_kem_init(int, u_int32_t, struct ssh *);
int
kex_kem_server(struct ssh *ssh)
{
debug("expecting SSH2_MSG_KEX_ECDH_INIT");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_kem_init);
return 0;
}
static int
input_kex_kem_init(int type, u_int32_t seq, struct ssh *ssh)
{
struct kex *kex = ssh->kex;
struct sshkey *server_host_private, *server_host_public;
struct sshbuf *shared_secret = NULL;
struct sshbuf *server_pubkey = NULL;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char *client_pubkey = NULL;
u_char hash[SSH_DIGEST_MAX_LENGTH];
size_t slen, pklen, sbloblen, hashlen;
int r;
if ((r = kex_load_hostkey(ssh, &server_host_private,
&server_host_public)) != 0)
goto out;
if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
/* compute shared secret */
switch (kex->kex_type) {
case KEX_DH_GRP1_SHA1:
case KEX_DH_GRP14_SHA1:
case KEX_DH_GRP14_SHA256:
case KEX_DH_GRP16_SHA512:
case KEX_DH_GRP18_SHA512:
r = kex_dh_enc(kex, client_pubkey, pklen, &server_pubkey,
&shared_secret);
break;
case KEX_ECDH_SHA2:
r = kex_ecdh_enc(kex, client_pubkey, pklen, &server_pubkey,
&shared_secret);
break;
case KEX_C25519_SHA256:
r = kex_c25519_enc(kex, client_pubkey, pklen, &server_pubkey,
&shared_secret);
break;
case KEX_KEM_SNTRUP4591761X25519_SHA512:
r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey, pklen,
&server_pubkey, &shared_secret);
break;
default:
r = SSH_ERR_INVALID_ARGUMENT;
break;
}
if (r !=0 )
goto out;
/* calc H */
if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
&sbloblen)) != 0)
goto out;
hashlen = sizeof(hash);
if ((r = kex_c25519_hash(
kex->hash_alg,
kex->client_version,
kex->server_version,
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
server_host_key_blob, sbloblen,
client_pubkey, pklen,
sshbuf_ptr(server_pubkey), sshbuf_len(server_pubkey),
sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
hash, &hashlen)) != 0)
goto out;
/* sign H */
if ((r = kex->sign(ssh, server_host_private, server_host_public,
&signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
goto out;
/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
(r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
(r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
r = kex_send_newkeys(ssh);
out:
explicit_bzero(hash, sizeof(hash));
free(server_host_key_blob);
free(signature);
free(client_pubkey);
sshbuf_free(shared_secret);
sshbuf_free(server_pubkey);
return r;
}
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