1295367Sdes/* $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 29295367Sdes#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) 30295367Sdes 31218767Sdes#include <sys/types.h> 32218767Sdes 33218767Sdes#include <stdio.h> 34218767Sdes#include <string.h> 35218767Sdes#include <signal.h> 36218767Sdes 37295367Sdes#include <openssl/ecdh.h> 38295367Sdes 39295367Sdes#include "sshkey.h" 40218767Sdes#include "cipher.h" 41295367Sdes#include "digest.h" 42218767Sdes#include "kex.h" 43218767Sdes#include "log.h" 44218767Sdes#include "packet.h" 45218767Sdes#include "dh.h" 46218767Sdes#include "ssh2.h" 47295367Sdes#include "dispatch.h" 48295367Sdes#include "compat.h" 49295367Sdes#include "ssherr.h" 50295367Sdes#include "sshbuf.h" 51218767Sdes 52295367Sdesstatic int input_kex_ecdh_reply(int, u_int32_t, void *); 53218767Sdes 54295367Sdesint 55295367Sdeskexecdh_client(struct ssh *ssh) 56218767Sdes{ 57295367Sdes struct kex *kex = ssh->kex; 58295367Sdes EC_KEY *client_key = NULL; 59218767Sdes const EC_GROUP *group; 60295367Sdes const EC_POINT *public_key; 61295367Sdes int r; 62218767Sdes 63295367Sdes if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { 64295367Sdes r = SSH_ERR_ALLOC_FAIL; 65295367Sdes goto out; 66295367Sdes } 67295367Sdes if (EC_KEY_generate_key(client_key) != 1) { 68295367Sdes r = SSH_ERR_LIBCRYPTO_ERROR; 69295367Sdes goto out; 70295367Sdes } 71218767Sdes group = EC_KEY_get0_group(client_key); 72295367Sdes public_key = EC_KEY_get0_public_key(client_key); 73218767Sdes 74295367Sdes if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 || 75295367Sdes (r = sshpkt_put_ec(ssh, public_key, group)) != 0 || 76295367Sdes (r = sshpkt_send(ssh)) != 0) 77295367Sdes goto out; 78218767Sdes debug("sending SSH2_MSG_KEX_ECDH_INIT"); 79218767Sdes 80218767Sdes#ifdef DEBUG_KEXECDH 81218767Sdes fputs("client private key:\n", stderr); 82295367Sdes sshkey_dump_ec_key(client_key); 83218767Sdes#endif 84295367Sdes kex->ec_client_key = client_key; 85295367Sdes kex->ec_group = group; 86295367Sdes client_key = NULL; /* owned by the kex */ 87218767Sdes 88218767Sdes debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 89295367Sdes ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply); 90295367Sdes r = 0; 91295367Sdes out: 92295367Sdes if (client_key) 93295367Sdes EC_KEY_free(client_key); 94295367Sdes return r; 95295367Sdes} 96218767Sdes 97295367Sdesstatic int 98295367Sdesinput_kex_ecdh_reply(int type, u_int32_t seq, void *ctxt) 99295367Sdes{ 100295367Sdes struct ssh *ssh = ctxt; 101295367Sdes struct kex *kex = ssh->kex; 102295367Sdes const EC_GROUP *group; 103295367Sdes EC_POINT *server_public = NULL; 104295367Sdes EC_KEY *client_key; 105295367Sdes BIGNUM *shared_secret = NULL; 106295367Sdes struct sshkey *server_host_key = NULL; 107295367Sdes u_char *server_host_key_blob = NULL, *signature = NULL; 108295367Sdes u_char *kbuf = NULL; 109295367Sdes u_char hash[SSH_DIGEST_MAX_LENGTH]; 110295367Sdes size_t slen, sbloblen; 111295367Sdes size_t klen = 0, hashlen; 112295367Sdes int r; 113295367Sdes 114295367Sdes if (kex->verify_host_key == NULL) { 115295367Sdes r = SSH_ERR_INVALID_ARGUMENT; 116295367Sdes goto out; 117295367Sdes } 118295367Sdes group = kex->ec_group; 119295367Sdes client_key = kex->ec_client_key; 120295367Sdes 121218767Sdes /* hostkey */ 122295367Sdes if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 123295367Sdes &sbloblen)) != 0 || 124295367Sdes (r = sshkey_from_blob(server_host_key_blob, sbloblen, 125295367Sdes &server_host_key)) != 0) 126295367Sdes goto out; 127295367Sdes if (server_host_key->type != kex->hostkey_type || 128295367Sdes (kex->hostkey_type == KEY_ECDSA && 129295367Sdes server_host_key->ecdsa_nid != kex->hostkey_nid)) { 130295367Sdes r = SSH_ERR_KEY_TYPE_MISMATCH; 131295367Sdes goto out; 132295367Sdes } 133295367Sdes if (kex->verify_host_key(server_host_key, ssh) == -1) { 134295367Sdes r = SSH_ERR_SIGNATURE_INVALID; 135295367Sdes goto out; 136295367Sdes } 137218767Sdes 138218767Sdes /* Q_S, server public key */ 139295367Sdes /* signed H */ 140295367Sdes if ((server_public = EC_POINT_new(group)) == NULL) { 141295367Sdes r = SSH_ERR_ALLOC_FAIL; 142295367Sdes goto out; 143295367Sdes } 144295367Sdes if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 || 145295367Sdes (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 146295367Sdes (r = sshpkt_get_end(ssh)) != 0) 147295367Sdes goto out; 148218767Sdes 149218767Sdes#ifdef DEBUG_KEXECDH 150218767Sdes fputs("server public key:\n", stderr); 151295367Sdes sshkey_dump_ec_point(group, server_public); 152218767Sdes#endif 153295367Sdes if (sshkey_ec_validate_public(group, server_public) != 0) { 154295367Sdes sshpkt_disconnect(ssh, "invalid server public key"); 155295367Sdes r = SSH_ERR_MESSAGE_INCOMPLETE; 156295367Sdes goto out; 157295367Sdes } 158218767Sdes 159218767Sdes klen = (EC_GROUP_get_degree(group) + 7) / 8; 160295367Sdes if ((kbuf = malloc(klen)) == NULL || 161295367Sdes (shared_secret = BN_new()) == NULL) { 162295367Sdes r = SSH_ERR_ALLOC_FAIL; 163295367Sdes goto out; 164295367Sdes } 165218767Sdes if (ECDH_compute_key(kbuf, klen, server_public, 166295367Sdes client_key, NULL) != (int)klen || 167295367Sdes BN_bin2bn(kbuf, klen, shared_secret) == NULL) { 168295367Sdes r = SSH_ERR_LIBCRYPTO_ERROR; 169295367Sdes goto out; 170295367Sdes } 171218767Sdes 172218767Sdes#ifdef DEBUG_KEXECDH 173218767Sdes dump_digest("shared secret", kbuf, klen); 174218767Sdes#endif 175218767Sdes /* calc and verify H */ 176295367Sdes hashlen = sizeof(hash); 177295367Sdes if ((r = kex_ecdh_hash( 178262566Sdes kex->hash_alg, 179218767Sdes group, 180218767Sdes kex->client_version_string, 181218767Sdes kex->server_version_string, 182295367Sdes sshbuf_ptr(kex->my), sshbuf_len(kex->my), 183295367Sdes 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, 188295367Sdes hash, &hashlen)) != 0) 189295367Sdes goto out; 190218767Sdes 191295367Sdes if ((r = sshkey_verify(server_host_key, signature, slen, hash, 192295367Sdes hashlen, ssh->compat)) != 0) 193295367Sdes goto out; 194218767Sdes 195218767Sdes /* save session id */ 196218767Sdes if (kex->session_id == NULL) { 197218767Sdes kex->session_id_len = hashlen; 198295367Sdes kex->session_id = malloc(kex->session_id_len); 199295367Sdes if (kex->session_id == NULL) { 200295367Sdes r = SSH_ERR_ALLOC_FAIL; 201295367Sdes goto out; 202295367Sdes } 203218767Sdes memcpy(kex->session_id, hash, kex->session_id_len); 204218767Sdes } 205218767Sdes 206295367Sdes if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 207295367Sdes r = kex_send_newkeys(ssh); 208295367Sdes out: 209295367Sdes explicit_bzero(hash, sizeof(hash)); 210295367Sdes if (kex->ec_client_key) { 211295367Sdes EC_KEY_free(kex->ec_client_key); 212295367Sdes kex->ec_client_key = NULL; 213295367Sdes } 214295367Sdes if (server_public) 215295367Sdes EC_POINT_clear_free(server_public); 216295367Sdes if (kbuf) { 217295367Sdes explicit_bzero(kbuf, klen); 218295367Sdes free(kbuf); 219295367Sdes } 220295367Sdes if (shared_secret) 221295367Sdes BN_clear_free(shared_secret); 222295367Sdes sshkey_free(server_host_key); 223295367Sdes free(server_host_key_blob); 224295367Sdes free(signature); 225295367Sdes return r; 226218767Sdes} 227295367Sdes#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ 228295367Sdes 229