1/* $OpenBSD: kexecdhc.c,v 1.13 2018/02/07 02:06:51 jsing Exp $ */ 2/* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27#include "includes.h" 28 29#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) 30 31#include <sys/types.h> 32 33#include <stdio.h> 34#include <string.h> 35#include <signal.h> 36 37#include <openssl/ecdh.h> 38 39#include "sshkey.h" 40#include "cipher.h" 41#include "digest.h" 42#include "kex.h" 43#include "log.h" 44#include "packet.h" 45#include "dh.h" 46#include "ssh2.h" 47#include "dispatch.h" 48#include "compat.h" 49#include "ssherr.h" 50#include "sshbuf.h" 51 52static int input_kex_ecdh_reply(int, u_int32_t, struct ssh *); 53 54int 55kexecdh_client(struct ssh *ssh) 56{ 57 struct kex *kex = ssh->kex; 58 EC_KEY *client_key = NULL; 59 const EC_GROUP *group; 60 const EC_POINT *public_key; 61 int r; 62 63 if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { 64 r = SSH_ERR_ALLOC_FAIL; 65 goto out; 66 } 67 if (EC_KEY_generate_key(client_key) != 1) { 68 r = SSH_ERR_LIBCRYPTO_ERROR; 69 goto out; 70 } 71 group = EC_KEY_get0_group(client_key); 72 public_key = EC_KEY_get0_public_key(client_key); 73 74 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 || 75 (r = sshpkt_put_ec(ssh, public_key, group)) != 0 || 76 (r = sshpkt_send(ssh)) != 0) 77 goto out; 78 debug("sending SSH2_MSG_KEX_ECDH_INIT"); 79 80#ifdef DEBUG_KEXECDH 81 fputs("client private key:\n", stderr); 82 sshkey_dump_ec_key(client_key); 83#endif 84 kex->ec_client_key = client_key; 85 kex->ec_group = group; 86 client_key = NULL; /* owned by the kex */ 87 88 debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 89 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply); 90 r = 0; 91 out: 92 EC_KEY_free(client_key); 93 return r; 94} 95 96static int 97input_kex_ecdh_reply(int type, u_int32_t seq, struct ssh *ssh) 98{ 99 struct kex *kex = ssh->kex; 100 const EC_GROUP *group; 101 EC_POINT *server_public = NULL; 102 EC_KEY *client_key; 103 BIGNUM *shared_secret = NULL; 104 struct sshkey *server_host_key = NULL; 105 u_char *server_host_key_blob = NULL, *signature = NULL; 106 u_char *kbuf = NULL; 107 u_char hash[SSH_DIGEST_MAX_LENGTH]; 108 size_t slen, sbloblen; 109 size_t klen = 0, hashlen; 110 int r; 111 112 if (kex->verify_host_key == NULL) { 113 r = SSH_ERR_INVALID_ARGUMENT; 114 goto out; 115 } 116 group = kex->ec_group; 117 client_key = kex->ec_client_key; 118 119 /* hostkey */ 120 if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 121 &sbloblen)) != 0 || 122 (r = sshkey_from_blob(server_host_key_blob, sbloblen, 123 &server_host_key)) != 0) 124 goto out; 125 if (server_host_key->type != kex->hostkey_type || 126 (kex->hostkey_type == KEY_ECDSA && 127 server_host_key->ecdsa_nid != kex->hostkey_nid)) { 128 r = SSH_ERR_KEY_TYPE_MISMATCH; 129 goto out; 130 } 131 if (kex->verify_host_key(server_host_key, ssh) == -1) { 132 r = SSH_ERR_SIGNATURE_INVALID; 133 goto out; 134 } 135 136 /* Q_S, server public key */ 137 /* signed H */ 138 if ((server_public = EC_POINT_new(group)) == NULL) { 139 r = SSH_ERR_ALLOC_FAIL; 140 goto out; 141 } 142 if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 || 143 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 144 (r = sshpkt_get_end(ssh)) != 0) 145 goto out; 146 147#ifdef DEBUG_KEXECDH 148 fputs("server public key:\n", stderr); 149 sshkey_dump_ec_point(group, server_public); 150#endif 151 if (sshkey_ec_validate_public(group, server_public) != 0) { 152 sshpkt_disconnect(ssh, "invalid server public key"); 153 r = SSH_ERR_MESSAGE_INCOMPLETE; 154 goto out; 155 } 156 157 klen = (EC_GROUP_get_degree(group) + 7) / 8; 158 if ((kbuf = malloc(klen)) == NULL || 159 (shared_secret = BN_new()) == NULL) { 160 r = SSH_ERR_ALLOC_FAIL; 161 goto out; 162 } 163 if (ECDH_compute_key(kbuf, klen, server_public, 164 client_key, NULL) != (int)klen || 165 BN_bin2bn(kbuf, klen, shared_secret) == NULL) { 166 r = SSH_ERR_LIBCRYPTO_ERROR; 167 goto out; 168 } 169 170#ifdef DEBUG_KEXECDH 171 dump_digest("shared secret", kbuf, klen); 172#endif 173 /* calc and verify H */ 174 hashlen = sizeof(hash); 175 if ((r = kex_ecdh_hash( 176 kex->hash_alg, 177 group, 178 kex->client_version_string, 179 kex->server_version_string, 180 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 181 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 182 server_host_key_blob, sbloblen, 183 EC_KEY_get0_public_key(client_key), 184 server_public, 185 shared_secret, 186 hash, &hashlen)) != 0) 187 goto out; 188 189 if ((r = sshkey_verify(server_host_key, signature, slen, hash, 190 hashlen, kex->hostkey_alg, ssh->compat)) != 0) 191 goto out; 192 193 /* save session id */ 194 if (kex->session_id == NULL) { 195 kex->session_id_len = hashlen; 196 kex->session_id = malloc(kex->session_id_len); 197 if (kex->session_id == NULL) { 198 r = SSH_ERR_ALLOC_FAIL; 199 goto out; 200 } 201 memcpy(kex->session_id, hash, kex->session_id_len); 202 } 203 204 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 205 r = kex_send_newkeys(ssh); 206 out: 207 explicit_bzero(hash, sizeof(hash)); 208 EC_KEY_free(kex->ec_client_key); 209 kex->ec_client_key = NULL; 210 EC_POINT_clear_free(server_public); 211 if (kbuf) { 212 explicit_bzero(kbuf, klen); 213 free(kbuf); 214 } 215 BN_clear_free(shared_secret); 216 sshkey_free(server_host_key); 217 free(server_host_key_blob); 218 free(signature); 219 return r; 220} 221#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ 222 223