1255767Sdes/* $OpenBSD: kexecdhc.c,v 1.4 2013/05/17 00:13:13 djm Exp $ */ 2218767Sdes/* 3218767Sdes * Copyright (c) 2001 Markus Friedl. All rights reserved. 4218767Sdes * Copyright (c) 2010 Damien Miller. All rights reserved. 5218767Sdes * 6218767Sdes * Redistribution and use in source and binary forms, with or without 7218767Sdes * modification, are permitted provided that the following conditions 8218767Sdes * are met: 9218767Sdes * 1. Redistributions of source code must retain the above copyright 10218767Sdes * notice, this list of conditions and the following disclaimer. 11218767Sdes * 2. Redistributions in binary form must reproduce the above copyright 12218767Sdes * notice, this list of conditions and the following disclaimer in the 13218767Sdes * documentation and/or other materials provided with the distribution. 14218767Sdes * 15218767Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16218767Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17218767Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18218767Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19218767Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20218767Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21218767Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22218767Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23218767Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24218767Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25218767Sdes */ 26218767Sdes 27218767Sdes#include "includes.h" 28218767Sdes 29218767Sdes#include <sys/types.h> 30218767Sdes 31218767Sdes#include <stdio.h> 32218767Sdes#include <string.h> 33218767Sdes#include <signal.h> 34218767Sdes 35218767Sdes#include "xmalloc.h" 36218767Sdes#include "buffer.h" 37218767Sdes#include "key.h" 38218767Sdes#include "cipher.h" 39218767Sdes#include "kex.h" 40218767Sdes#include "log.h" 41218767Sdes#include "packet.h" 42218767Sdes#include "dh.h" 43218767Sdes#include "ssh2.h" 44218767Sdes 45218767Sdes#ifdef OPENSSL_HAS_ECC 46218767Sdes 47218767Sdes#include <openssl/ecdh.h> 48218767Sdes 49218767Sdesvoid 50218767Sdeskexecdh_client(Kex *kex) 51218767Sdes{ 52218767Sdes EC_KEY *client_key; 53218767Sdes EC_POINT *server_public; 54218767Sdes const EC_GROUP *group; 55218767Sdes BIGNUM *shared_secret; 56218767Sdes Key *server_host_key; 57218767Sdes u_char *server_host_key_blob = NULL, *signature = NULL; 58218767Sdes u_char *kbuf, *hash; 59218767Sdes u_int klen, slen, sbloblen, hashlen; 60218767Sdes 61255767Sdes if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) 62218767Sdes fatal("%s: EC_KEY_new_by_curve_name failed", __func__); 63218767Sdes if (EC_KEY_generate_key(client_key) != 1) 64218767Sdes fatal("%s: EC_KEY_generate_key failed", __func__); 65218767Sdes group = EC_KEY_get0_group(client_key); 66218767Sdes 67218767Sdes packet_start(SSH2_MSG_KEX_ECDH_INIT); 68218767Sdes packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key)); 69218767Sdes packet_send(); 70218767Sdes debug("sending SSH2_MSG_KEX_ECDH_INIT"); 71218767Sdes 72218767Sdes#ifdef DEBUG_KEXECDH 73218767Sdes fputs("client private key:\n", stderr); 74218767Sdes key_dump_ec_key(client_key); 75218767Sdes#endif 76218767Sdes 77218767Sdes debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 78218767Sdes packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY); 79218767Sdes 80218767Sdes /* hostkey */ 81218767Sdes server_host_key_blob = packet_get_string(&sbloblen); 82218767Sdes server_host_key = key_from_blob(server_host_key_blob, sbloblen); 83218767Sdes if (server_host_key == NULL) 84218767Sdes fatal("cannot decode server_host_key_blob"); 85218767Sdes if (server_host_key->type != kex->hostkey_type) 86218767Sdes fatal("type mismatch for decoded server_host_key_blob"); 87218767Sdes if (kex->verify_host_key == NULL) 88218767Sdes fatal("cannot verify server_host_key"); 89218767Sdes if (kex->verify_host_key(server_host_key) == -1) 90218767Sdes fatal("server_host_key verification failed"); 91218767Sdes 92218767Sdes /* Q_S, server public key */ 93218767Sdes if ((server_public = EC_POINT_new(group)) == NULL) 94218767Sdes fatal("%s: EC_POINT_new failed", __func__); 95218767Sdes packet_get_ecpoint(group, server_public); 96218767Sdes 97218767Sdes if (key_ec_validate_public(group, server_public) != 0) 98218767Sdes fatal("%s: invalid server public key", __func__); 99218767Sdes 100218767Sdes#ifdef DEBUG_KEXECDH 101218767Sdes fputs("server public key:\n", stderr); 102218767Sdes key_dump_ec_point(group, server_public); 103218767Sdes#endif 104218767Sdes 105218767Sdes /* signed H */ 106218767Sdes signature = packet_get_string(&slen); 107218767Sdes packet_check_eom(); 108218767Sdes 109218767Sdes klen = (EC_GROUP_get_degree(group) + 7) / 8; 110218767Sdes kbuf = xmalloc(klen); 111218767Sdes if (ECDH_compute_key(kbuf, klen, server_public, 112218767Sdes client_key, NULL) != (int)klen) 113218767Sdes fatal("%s: ECDH_compute_key failed", __func__); 114218767Sdes 115218767Sdes#ifdef DEBUG_KEXECDH 116218767Sdes dump_digest("shared secret", kbuf, klen); 117218767Sdes#endif 118218767Sdes if ((shared_secret = BN_new()) == NULL) 119218767Sdes fatal("%s: BN_new failed", __func__); 120218767Sdes if (BN_bin2bn(kbuf, klen, shared_secret) == NULL) 121218767Sdes fatal("%s: BN_bin2bn failed", __func__); 122218767Sdes memset(kbuf, 0, klen); 123255767Sdes free(kbuf); 124218767Sdes 125218767Sdes /* calc and verify H */ 126218767Sdes kex_ecdh_hash( 127218767Sdes kex->evp_md, 128218767Sdes group, 129218767Sdes kex->client_version_string, 130218767Sdes kex->server_version_string, 131218767Sdes buffer_ptr(&kex->my), buffer_len(&kex->my), 132218767Sdes buffer_ptr(&kex->peer), buffer_len(&kex->peer), 133218767Sdes server_host_key_blob, sbloblen, 134218767Sdes EC_KEY_get0_public_key(client_key), 135218767Sdes server_public, 136218767Sdes shared_secret, 137218767Sdes &hash, &hashlen 138218767Sdes ); 139255767Sdes free(server_host_key_blob); 140218767Sdes EC_POINT_clear_free(server_public); 141218767Sdes EC_KEY_free(client_key); 142218767Sdes 143218767Sdes if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) 144218767Sdes fatal("key_verify failed for server_host_key"); 145218767Sdes key_free(server_host_key); 146255767Sdes free(signature); 147218767Sdes 148218767Sdes /* save session id */ 149218767Sdes if (kex->session_id == NULL) { 150218767Sdes kex->session_id_len = hashlen; 151218767Sdes kex->session_id = xmalloc(kex->session_id_len); 152218767Sdes memcpy(kex->session_id, hash, kex->session_id_len); 153218767Sdes } 154218767Sdes 155218767Sdes kex_derive_keys(kex, hash, hashlen, shared_secret); 156218767Sdes BN_clear_free(shared_secret); 157218767Sdes kex_finish(kex); 158218767Sdes} 159218767Sdes#else /* OPENSSL_HAS_ECC */ 160218767Sdesvoid 161218767Sdeskexecdh_client(Kex *kex) 162218767Sdes{ 163218767Sdes fatal("ECC support is not enabled"); 164218767Sdes} 165218767Sdes#endif /* OPENSSL_HAS_ECC */ 166