1294332Sdes/* $OpenBSD: kexecdhc.c,v 1.10 2015/01/26 06:10:03 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 29294332Sdes#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) 30294332Sdes 31218767Sdes#include <sys/types.h> 32218767Sdes 33218767Sdes#include <stdio.h> 34218767Sdes#include <string.h> 35218767Sdes#include <signal.h> 36218767Sdes 37294332Sdes#include <openssl/ecdh.h> 38294332Sdes 39294332Sdes#include "sshkey.h" 40218767Sdes#include "cipher.h" 41294332Sdes#include "digest.h" 42218767Sdes#include "kex.h" 43218767Sdes#include "log.h" 44218767Sdes#include "packet.h" 45218767Sdes#include "dh.h" 46218767Sdes#include "ssh2.h" 47294332Sdes#include "dispatch.h" 48294332Sdes#include "compat.h" 49294332Sdes#include "ssherr.h" 50294332Sdes#include "sshbuf.h" 51218767Sdes 52294332Sdesstatic int input_kex_ecdh_reply(int, u_int32_t, void *); 53218767Sdes 54294332Sdesint 55294332Sdeskexecdh_client(struct ssh *ssh) 56218767Sdes{ 57294332Sdes struct kex *kex = ssh->kex; 58294332Sdes EC_KEY *client_key = NULL; 59218767Sdes const EC_GROUP *group; 60294332Sdes const EC_POINT *public_key; 61294332Sdes int r; 62218767Sdes 63294332Sdes if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { 64294332Sdes r = SSH_ERR_ALLOC_FAIL; 65294332Sdes goto out; 66294332Sdes } 67294332Sdes if (EC_KEY_generate_key(client_key) != 1) { 68294332Sdes r = SSH_ERR_LIBCRYPTO_ERROR; 69294332Sdes goto out; 70294332Sdes } 71218767Sdes group = EC_KEY_get0_group(client_key); 72294332Sdes public_key = EC_KEY_get0_public_key(client_key); 73218767Sdes 74294332Sdes if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 || 75294332Sdes (r = sshpkt_put_ec(ssh, public_key, group)) != 0 || 76294332Sdes (r = sshpkt_send(ssh)) != 0) 77294332Sdes goto out; 78218767Sdes debug("sending SSH2_MSG_KEX_ECDH_INIT"); 79218767Sdes 80218767Sdes#ifdef DEBUG_KEXECDH 81218767Sdes fputs("client private key:\n", stderr); 82294332Sdes sshkey_dump_ec_key(client_key); 83218767Sdes#endif 84294332Sdes kex->ec_client_key = client_key; 85294332Sdes kex->ec_group = group; 86294332Sdes client_key = NULL; /* owned by the kex */ 87218767Sdes 88218767Sdes debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 89294332Sdes ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply); 90294332Sdes r = 0; 91294332Sdes out: 92294332Sdes if (client_key) 93294332Sdes EC_KEY_free(client_key); 94294332Sdes return r; 95294332Sdes} 96218767Sdes 97294332Sdesstatic int 98294332Sdesinput_kex_ecdh_reply(int type, u_int32_t seq, void *ctxt) 99294332Sdes{ 100294332Sdes struct ssh *ssh = ctxt; 101294332Sdes struct kex *kex = ssh->kex; 102294332Sdes const EC_GROUP *group; 103294332Sdes EC_POINT *server_public = NULL; 104294332Sdes EC_KEY *client_key; 105294332Sdes BIGNUM *shared_secret = NULL; 106294332Sdes struct sshkey *server_host_key = NULL; 107294332Sdes u_char *server_host_key_blob = NULL, *signature = NULL; 108294332Sdes u_char *kbuf = NULL; 109294332Sdes u_char hash[SSH_DIGEST_MAX_LENGTH]; 110294332Sdes size_t slen, sbloblen; 111294332Sdes size_t klen = 0, hashlen; 112294332Sdes int r; 113294332Sdes 114294332Sdes if (kex->verify_host_key == NULL) { 115294332Sdes r = SSH_ERR_INVALID_ARGUMENT; 116294332Sdes goto out; 117294332Sdes } 118294332Sdes group = kex->ec_group; 119294332Sdes client_key = kex->ec_client_key; 120294332Sdes 121218767Sdes /* hostkey */ 122294332Sdes if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 123294332Sdes &sbloblen)) != 0 || 124294332Sdes (r = sshkey_from_blob(server_host_key_blob, sbloblen, 125294332Sdes &server_host_key)) != 0) 126294332Sdes goto out; 127294332Sdes if (server_host_key->type != kex->hostkey_type || 128294332Sdes (kex->hostkey_type == KEY_ECDSA && 129294332Sdes server_host_key->ecdsa_nid != kex->hostkey_nid)) { 130294332Sdes r = SSH_ERR_KEY_TYPE_MISMATCH; 131294332Sdes goto out; 132294332Sdes } 133294332Sdes if (kex->verify_host_key(server_host_key, ssh) == -1) { 134294332Sdes r = SSH_ERR_SIGNATURE_INVALID; 135294332Sdes goto out; 136294332Sdes } 137218767Sdes 138218767Sdes /* Q_S, server public key */ 139294332Sdes /* signed H */ 140294332Sdes if ((server_public = EC_POINT_new(group)) == NULL) { 141294332Sdes r = SSH_ERR_ALLOC_FAIL; 142294332Sdes goto out; 143294332Sdes } 144294332Sdes if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 || 145294332Sdes (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 146294332Sdes (r = sshpkt_get_end(ssh)) != 0) 147294332Sdes goto out; 148218767Sdes 149218767Sdes#ifdef DEBUG_KEXECDH 150218767Sdes fputs("server public key:\n", stderr); 151294332Sdes sshkey_dump_ec_point(group, server_public); 152218767Sdes#endif 153294332Sdes if (sshkey_ec_validate_public(group, server_public) != 0) { 154294332Sdes sshpkt_disconnect(ssh, "invalid server public key"); 155294332Sdes r = SSH_ERR_MESSAGE_INCOMPLETE; 156294332Sdes goto out; 157294332Sdes } 158218767Sdes 159218767Sdes klen = (EC_GROUP_get_degree(group) + 7) / 8; 160294332Sdes if ((kbuf = malloc(klen)) == NULL || 161294332Sdes (shared_secret = BN_new()) == NULL) { 162294332Sdes r = SSH_ERR_ALLOC_FAIL; 163294332Sdes goto out; 164294332Sdes } 165218767Sdes if (ECDH_compute_key(kbuf, klen, server_public, 166294332Sdes client_key, NULL) != (int)klen || 167294332Sdes BN_bin2bn(kbuf, klen, shared_secret) == NULL) { 168294332Sdes r = SSH_ERR_LIBCRYPTO_ERROR; 169294332Sdes goto out; 170294332Sdes } 171218767Sdes 172218767Sdes#ifdef DEBUG_KEXECDH 173218767Sdes dump_digest("shared secret", kbuf, klen); 174218767Sdes#endif 175218767Sdes /* calc and verify H */ 176294332Sdes hashlen = sizeof(hash); 177294332Sdes if ((r = kex_ecdh_hash( 178261320Sdes kex->hash_alg, 179218767Sdes group, 180218767Sdes kex->client_version_string, 181218767Sdes kex->server_version_string, 182294332Sdes sshbuf_ptr(kex->my), sshbuf_len(kex->my), 183294332Sdes sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 184218767Sdes server_host_key_blob, sbloblen, 185218767Sdes EC_KEY_get0_public_key(client_key), 186218767Sdes server_public, 187218767Sdes shared_secret, 188294332Sdes hash, &hashlen)) != 0) 189294332Sdes goto out; 190218767Sdes 191294332Sdes if ((r = sshkey_verify(server_host_key, signature, slen, hash, 192294332Sdes hashlen, ssh->compat)) != 0) 193294332Sdes goto out; 194218767Sdes 195218767Sdes /* save session id */ 196218767Sdes if (kex->session_id == NULL) { 197218767Sdes kex->session_id_len = hashlen; 198294332Sdes kex->session_id = malloc(kex->session_id_len); 199294332Sdes if (kex->session_id == NULL) { 200294332Sdes r = SSH_ERR_ALLOC_FAIL; 201294332Sdes goto out; 202294332Sdes } 203218767Sdes memcpy(kex->session_id, hash, kex->session_id_len); 204218767Sdes } 205218767Sdes 206294332Sdes if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 207294332Sdes r = kex_send_newkeys(ssh); 208294332Sdes out: 209294332Sdes explicit_bzero(hash, sizeof(hash)); 210294332Sdes if (kex->ec_client_key) { 211294332Sdes EC_KEY_free(kex->ec_client_key); 212294332Sdes kex->ec_client_key = NULL; 213294332Sdes } 214294332Sdes if (server_public) 215294332Sdes EC_POINT_clear_free(server_public); 216294332Sdes if (kbuf) { 217294332Sdes explicit_bzero(kbuf, klen); 218294332Sdes free(kbuf); 219294332Sdes } 220294332Sdes if (shared_secret) 221294332Sdes BN_clear_free(shared_secret); 222294332Sdes sshkey_free(server_host_key); 223294332Sdes free(server_host_key_blob); 224294332Sdes free(signature); 225294332Sdes return r; 226218767Sdes} 227294332Sdes#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ 228294332Sdes 229