1/* $OpenBSD: kexecdhc.c,v 1.4 2013/05/17 00:13:13 djm 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#include <sys/types.h> 30 31#include <stdio.h> 32#include <string.h> 33#include <signal.h> 34 35#include "xmalloc.h" 36#include "buffer.h" 37#include "key.h" 38#include "cipher.h" 39#include "kex.h" 40#include "log.h" 41#include "packet.h" 42#include "dh.h" 43#include "ssh2.h" 44 45#ifdef OPENSSL_HAS_ECC 46 47#include <openssl/ecdh.h> 48 49void 50kexecdh_client(Kex *kex) 51{ 52 EC_KEY *client_key; 53 EC_POINT *server_public; 54 const EC_GROUP *group; 55 BIGNUM *shared_secret; 56 Key *server_host_key; 57 u_char *server_host_key_blob = NULL, *signature = NULL; 58 u_char *kbuf, *hash; 59 u_int klen, slen, sbloblen, hashlen; 60 61 if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) 62 fatal("%s: EC_KEY_new_by_curve_name failed", __func__); 63 if (EC_KEY_generate_key(client_key) != 1) 64 fatal("%s: EC_KEY_generate_key failed", __func__); 65 group = EC_KEY_get0_group(client_key); 66 67 packet_start(SSH2_MSG_KEX_ECDH_INIT); 68 packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key)); 69 packet_send(); 70 debug("sending SSH2_MSG_KEX_ECDH_INIT"); 71 72#ifdef DEBUG_KEXECDH 73 fputs("client private key:\n", stderr); 74 key_dump_ec_key(client_key); 75#endif 76 77 debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); 78 packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY); 79 80 /* hostkey */ 81 server_host_key_blob = packet_get_string(&sbloblen); 82 server_host_key = key_from_blob(server_host_key_blob, sbloblen); 83 if (server_host_key == NULL) 84 fatal("cannot decode server_host_key_blob"); 85 if (server_host_key->type != kex->hostkey_type) 86 fatal("type mismatch for decoded server_host_key_blob"); 87 if (kex->verify_host_key == NULL) 88 fatal("cannot verify server_host_key"); 89 if (kex->verify_host_key(server_host_key) == -1) 90 fatal("server_host_key verification failed"); 91 92 /* Q_S, server public key */ 93 if ((server_public = EC_POINT_new(group)) == NULL) 94 fatal("%s: EC_POINT_new failed", __func__); 95 packet_get_ecpoint(group, server_public); 96 97 if (key_ec_validate_public(group, server_public) != 0) 98 fatal("%s: invalid server public key", __func__); 99 100#ifdef DEBUG_KEXECDH 101 fputs("server public key:\n", stderr); 102 key_dump_ec_point(group, server_public); 103#endif 104 105 /* signed H */ 106 signature = packet_get_string(&slen); 107 packet_check_eom(); 108 109 klen = (EC_GROUP_get_degree(group) + 7) / 8; 110 kbuf = xmalloc(klen); 111 if (ECDH_compute_key(kbuf, klen, server_public, 112 client_key, NULL) != (int)klen) 113 fatal("%s: ECDH_compute_key failed", __func__); 114 115#ifdef DEBUG_KEXECDH 116 dump_digest("shared secret", kbuf, klen); 117#endif 118 if ((shared_secret = BN_new()) == NULL) 119 fatal("%s: BN_new failed", __func__); 120 if (BN_bin2bn(kbuf, klen, shared_secret) == NULL) 121 fatal("%s: BN_bin2bn failed", __func__); 122 memset(kbuf, 0, klen); 123 free(kbuf); 124 125 /* calc and verify H */ 126 kex_ecdh_hash( 127 kex->evp_md, 128 group, 129 kex->client_version_string, 130 kex->server_version_string, 131 buffer_ptr(&kex->my), buffer_len(&kex->my), 132 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 133 server_host_key_blob, sbloblen, 134 EC_KEY_get0_public_key(client_key), 135 server_public, 136 shared_secret, 137 &hash, &hashlen 138 ); 139 free(server_host_key_blob); 140 EC_POINT_clear_free(server_public); 141 EC_KEY_free(client_key); 142 143 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) 144 fatal("key_verify failed for server_host_key"); 145 key_free(server_host_key); 146 free(signature); 147 148 /* save session id */ 149 if (kex->session_id == NULL) { 150 kex->session_id_len = hashlen; 151 kex->session_id = xmalloc(kex->session_id_len); 152 memcpy(kex->session_id, hash, kex->session_id_len); 153 } 154 155 kex_derive_keys(kex, hash, hashlen, shared_secret); 156 BN_clear_free(shared_secret); 157 kex_finish(kex); 158} 159#else /* OPENSSL_HAS_ECC */ 160void 161kexecdh_client(Kex *kex) 162{ 163 fatal("ECC support is not enabled"); 164} 165#endif /* OPENSSL_HAS_ECC */ 166