134 lines
4.6 KiB
C
134 lines
4.6 KiB
C
/* $OpenBSD: kexc25519.c,v 1.10 2016/05/02 08:49:03 djm 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 "sshbuf.h"
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#include "ssh2.h"
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#include "sshkey.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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#include "digest.h"
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#include "ssherr.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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int
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kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
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const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
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{
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u_char shared_key[CURVE25519_SIZE];
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int r;
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/* Check for all-zero public key */
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explicit_bzero(shared_key, CURVE25519_SIZE);
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if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0)
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return SSH_ERR_KEY_INVALID_EC_VALUE;
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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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sshbuf_reset(out);
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r = sshbuf_put_bignum2_bytes(out, shared_key, CURVE25519_SIZE);
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explicit_bzero(shared_key, CURVE25519_SIZE);
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return r;
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}
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int
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kex_c25519_hash(
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int hash_alg,
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const char *client_version_string,
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const char *server_version_string,
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const u_char *ckexinit, size_t ckexinitlen,
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const u_char *skexinit, size_t skexinitlen,
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const u_char *serverhostkeyblob, size_t 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 u_char *shared_secret, size_t secretlen,
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u_char *hash, size_t *hashlen)
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{
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struct sshbuf *b;
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int r;
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if (*hashlen < ssh_digest_bytes(hash_alg))
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return SSH_ERR_INVALID_ARGUMENT;
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if ((b = sshbuf_new()) == NULL)
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return SSH_ERR_ALLOC_FAIL;
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if ((r = sshbuf_put_cstring(b, client_version_string)) < 0 ||
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(r = sshbuf_put_cstring(b, server_version_string)) < 0 ||
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/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
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(r = sshbuf_put_u32(b, ckexinitlen+1)) < 0 ||
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(r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 ||
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(r = sshbuf_put(b, ckexinit, ckexinitlen)) < 0 ||
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(r = sshbuf_put_u32(b, skexinitlen+1)) < 0 ||
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(r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 ||
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(r = sshbuf_put(b, skexinit, skexinitlen)) < 0 ||
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(r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) < 0 ||
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(r = sshbuf_put_string(b, client_dh_pub, CURVE25519_SIZE)) < 0 ||
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(r = sshbuf_put_string(b, server_dh_pub, CURVE25519_SIZE)) < 0 ||
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(r = sshbuf_put(b, shared_secret, secretlen)) < 0) {
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sshbuf_free(b);
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return r;
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}
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#ifdef DEBUG_KEX
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sshbuf_dump(b, stderr);
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#endif
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if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
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sshbuf_free(b);
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return SSH_ERR_LIBCRYPTO_ERROR;
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}
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sshbuf_free(b);
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*hashlen = ssh_digest_bytes(hash_alg);
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#ifdef DEBUG_KEX
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dump_digest("hash", hash, *hashlen);
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#endif
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return 0;
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}
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