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/* $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 <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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} |