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/* $OpenBSD: kexc25519.c,v 1.2 2013/11/02 22:02:14 markus Exp $ */
/*
* Copyright (c) 2001, 2013 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 <sys/types.h>
#include <signal.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/evp.h>
#include "buffer.h"
#include "ssh2.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "log.h"
extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)))
__attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE)));
void
kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
{
static const u_char basepoint[CURVE25519_SIZE] = {9};
arc4random_buf(key, CURVE25519_SIZE);
crypto_scalarmult_curve25519(pub, key, basepoint);
}
BIGNUM *
kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
const u_char pub[CURVE25519_SIZE])
{
u_char shared_key[CURVE25519_SIZE];
BIGNUM *shared_secret;
crypto_scalarmult_curve25519(shared_key, key, pub);
#ifdef DEBUG_KEXECDH
dump_digest("shared secret", shared_key, CURVE25519_SIZE);
#endif
if ((shared_secret = BN_new()) == NULL)
fatal("%s: BN_new failed", __func__);
if (BN_bin2bn(shared_key, sizeof(shared_key), shared_secret) == NULL)
fatal("%s: BN_bin2bn failed", __func__);
memset(shared_key, 0, CURVE25519_SIZE); /* XXX explicit_bzero() */
return (shared_secret);
}
void
kex_c25519_hash(
const EVP_MD *evp_md,
char *client_version_string,
char *server_version_string,
char *ckexinit, int ckexinitlen,
char *skexinit, int skexinitlen,
u_char *serverhostkeyblob, int sbloblen,
const u_char client_dh_pub[CURVE25519_SIZE],
const u_char server_dh_pub[CURVE25519_SIZE],
const BIGNUM *shared_secret,
u_char **hash, u_int *hashlen)
{
Buffer b;
EVP_MD_CTX md;
static u_char digest[EVP_MAX_MD_SIZE];
buffer_init(&b);
buffer_put_cstring(&b, client_version_string);
buffer_put_cstring(&b, server_version_string);
/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
buffer_put_int(&b, ckexinitlen+1);
buffer_put_char(&b, SSH2_MSG_KEXINIT);
buffer_append(&b, ckexinit, ckexinitlen);
buffer_put_int(&b, skexinitlen+1);
buffer_put_char(&b, SSH2_MSG_KEXINIT);
buffer_append(&b, skexinit, skexinitlen);
buffer_put_string(&b, serverhostkeyblob, sbloblen);
buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
buffer_put_bignum2(&b, shared_secret);
#ifdef DEBUG_KEX
buffer_dump(&b);
#endif
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
EVP_DigestFinal(&md, digest, NULL);
buffer_free(&b);
#ifdef DEBUG_KEX
dump_digest("hash", digest, EVP_MD_size(evp_md));
#endif
*hash = digest;
*hashlen = EVP_MD_size(evp_md);
}
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