162 lines
5.0 KiB
C
162 lines
5.0 KiB
C
/* $OpenBSD: kexecdhs.c,v 1.10 2014/02/02 03:44:31 djm Exp $ */
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/*
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* Copyright (c) 2001 Markus Friedl. All rights reserved.
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* Copyright (c) 2010 Damien Miller. 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 <string.h>
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#include <signal.h>
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#include "xmalloc.h"
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#include "buffer.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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#include "packet.h"
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#include "ssh2.h"
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#ifdef OPENSSL_HAS_ECC
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#include <openssl/ecdh.h>
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void
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kexecdh_server(Kex *kex)
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{
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EC_POINT *client_public;
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EC_KEY *server_key;
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const EC_GROUP *group;
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BIGNUM *shared_secret;
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Key *server_host_private, *server_host_public;
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u_char *server_host_key_blob = NULL, *signature = NULL;
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u_char *kbuf, *hash;
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u_int klen, slen, sbloblen, hashlen;
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if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
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fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
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if (EC_KEY_generate_key(server_key) != 1)
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fatal("%s: EC_KEY_generate_key failed", __func__);
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group = EC_KEY_get0_group(server_key);
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#ifdef DEBUG_KEXECDH
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fputs("server private key:\n", stderr);
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key_dump_ec_key(server_key);
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#endif
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if (kex->load_host_public_key == NULL ||
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kex->load_host_private_key == NULL)
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fatal("Cannot load hostkey");
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server_host_public = kex->load_host_public_key(kex->hostkey_type);
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if (server_host_public == NULL)
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fatal("Unsupported hostkey type %d", kex->hostkey_type);
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server_host_private = kex->load_host_private_key(kex->hostkey_type);
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debug("expecting SSH2_MSG_KEX_ECDH_INIT");
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packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
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if ((client_public = EC_POINT_new(group)) == NULL)
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fatal("%s: EC_POINT_new failed", __func__);
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packet_get_ecpoint(group, client_public);
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packet_check_eom();
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if (key_ec_validate_public(group, client_public) != 0)
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fatal("%s: invalid client public key", __func__);
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#ifdef DEBUG_KEXECDH
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fputs("client public key:\n", stderr);
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key_dump_ec_point(group, client_public);
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#endif
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/* Calculate shared_secret */
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klen = (EC_GROUP_get_degree(group) + 7) / 8;
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kbuf = xmalloc(klen);
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if (ECDH_compute_key(kbuf, klen, client_public,
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server_key, NULL) != (int)klen)
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fatal("%s: ECDH_compute_key failed", __func__);
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#ifdef DEBUG_KEXDH
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dump_digest("shared secret", kbuf, klen);
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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(kbuf, klen, shared_secret) == NULL)
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fatal("%s: BN_bin2bn failed", __func__);
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explicit_bzero(kbuf, klen);
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free(kbuf);
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/* calc H */
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key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
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kex_ecdh_hash(
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kex->hash_alg,
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group,
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kex->client_version_string,
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kex->server_version_string,
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buffer_ptr(&kex->peer), buffer_len(&kex->peer),
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buffer_ptr(&kex->my), buffer_len(&kex->my),
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server_host_key_blob, sbloblen,
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client_public,
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EC_KEY_get0_public_key(server_key),
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shared_secret,
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&hash, &hashlen
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);
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EC_POINT_clear_free(client_public);
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/* save session id := H */
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if (kex->session_id == NULL) {
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kex->session_id_len = hashlen;
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kex->session_id = xmalloc(kex->session_id_len);
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memcpy(kex->session_id, hash, kex->session_id_len);
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}
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/* sign H */
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kex->sign(server_host_private, server_host_public, &signature, &slen,
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hash, hashlen);
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/* destroy_sensitive_data(); */
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/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
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packet_start(SSH2_MSG_KEX_ECDH_REPLY);
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packet_put_string(server_host_key_blob, sbloblen);
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packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
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packet_put_string(signature, slen);
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packet_send();
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free(signature);
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free(server_host_key_blob);
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/* have keys, free server key */
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EC_KEY_free(server_key);
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kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
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BN_clear_free(shared_secret);
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kex_finish(kex);
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}
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#else /* OPENSSL_HAS_ECC */
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void
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kexecdh_server(Kex *kex)
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{
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fatal("ECC support is not enabled");
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}
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#endif /* OPENSSL_HAS_ECC */
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