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128 lines
4.2 KiB
C
128 lines
4.2 KiB
C
/* $OpenBSD: kexc25519.c,v 1.2 2013/11/02 22:02:14 markus Exp $ */
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/*
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* Copyright (c) 2001, 2013 Markus Friedl. All rights reserved.
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* Copyright (c) 2010 Damien Miller. All rights reserved.
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* Copyright (c) 2013 Aris Adamantiadis. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <signal.h>
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#include <string.h>
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#include <openssl/bn.h>
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#include <openssl/evp.h>
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#include "buffer.h"
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#include "ssh2.h"
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#include "key.h"
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#include "cipher.h"
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#include "kex.h"
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#include "log.h"
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extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
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const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
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__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
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__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)))
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__attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE)));
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void
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kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
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{
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static const u_char basepoint[CURVE25519_SIZE] = {9};
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arc4random_buf(key, CURVE25519_SIZE);
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crypto_scalarmult_curve25519(pub, key, basepoint);
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}
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BIGNUM *
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kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
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const u_char pub[CURVE25519_SIZE])
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{
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u_char shared_key[CURVE25519_SIZE];
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BIGNUM *shared_secret;
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crypto_scalarmult_curve25519(shared_key, key, pub);
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#ifdef DEBUG_KEXECDH
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dump_digest("shared secret", shared_key, CURVE25519_SIZE);
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#endif
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if ((shared_secret = BN_new()) == NULL)
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fatal("%s: BN_new failed", __func__);
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if (BN_bin2bn(shared_key, sizeof(shared_key), shared_secret) == NULL)
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fatal("%s: BN_bin2bn failed", __func__);
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memset(shared_key, 0, CURVE25519_SIZE); /* XXX explicit_bzero() */
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return (shared_secret);
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}
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void
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kex_c25519_hash(
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const EVP_MD *evp_md,
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char *client_version_string,
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char *server_version_string,
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char *ckexinit, int ckexinitlen,
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char *skexinit, int skexinitlen,
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u_char *serverhostkeyblob, int sbloblen,
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const u_char client_dh_pub[CURVE25519_SIZE],
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const u_char server_dh_pub[CURVE25519_SIZE],
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const BIGNUM *shared_secret,
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u_char **hash, u_int *hashlen)
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{
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Buffer b;
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EVP_MD_CTX md;
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static u_char digest[EVP_MAX_MD_SIZE];
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buffer_init(&b);
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buffer_put_cstring(&b, client_version_string);
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buffer_put_cstring(&b, server_version_string);
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/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
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buffer_put_int(&b, ckexinitlen+1);
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buffer_put_char(&b, SSH2_MSG_KEXINIT);
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buffer_append(&b, ckexinit, ckexinitlen);
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buffer_put_int(&b, skexinitlen+1);
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buffer_put_char(&b, SSH2_MSG_KEXINIT);
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buffer_append(&b, skexinit, skexinitlen);
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buffer_put_string(&b, serverhostkeyblob, sbloblen);
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buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
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buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
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buffer_put_bignum2(&b, shared_secret);
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#ifdef DEBUG_KEX
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buffer_dump(&b);
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#endif
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EVP_DigestInit(&md, evp_md);
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EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
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EVP_DigestFinal(&md, digest, NULL);
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buffer_free(&b);
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#ifdef DEBUG_KEX
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dump_digest("hash", digest, EVP_MD_size(evp_md));
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#endif
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*hash = digest;
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*hashlen = EVP_MD_size(evp_md);
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}
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