1/* $OpenBSD: kexdhs.c,v 1.27 2018/04/10 00:10:49 djm Exp $ */ 2/* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#include "includes.h" 27 28#ifdef WITH_OPENSSL 29 30#include <sys/types.h> 31 32#include <stdarg.h> 33#include <string.h> 34#include <signal.h> 35 36#include <openssl/dh.h> 37 38#include "openbsd-compat/openssl-compat.h" 39 40#include "sshkey.h" 41#include "cipher.h" 42#include "digest.h" 43#include "kex.h" 44#include "log.h" 45#include "packet.h" 46#include "dh.h" 47#include "ssh2.h" 48 49#include "dispatch.h" 50#include "compat.h" 51#include "ssherr.h" 52#include "sshbuf.h" 53 54static int input_kex_dh_init(int, u_int32_t, struct ssh *); 55 56int 57kexdh_server(struct ssh *ssh) 58{ 59 struct kex *kex = ssh->kex; 60 int r; 61 62 /* generate server DH public key */ 63 switch (kex->kex_type) { 64 case KEX_DH_GRP1_SHA1: 65 kex->dh = dh_new_group1(); 66 break; 67 case KEX_DH_GRP14_SHA1: 68 case KEX_DH_GRP14_SHA256: 69 kex->dh = dh_new_group14(); 70 break; 71 case KEX_DH_GRP16_SHA512: 72 kex->dh = dh_new_group16(); 73 break; 74 case KEX_DH_GRP18_SHA512: 75 kex->dh = dh_new_group18(); 76 break; 77 default: 78 r = SSH_ERR_INVALID_ARGUMENT; 79 goto out; 80 } 81 if (kex->dh == NULL) { 82 r = SSH_ERR_ALLOC_FAIL; 83 goto out; 84 } 85 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) 86 goto out; 87 88 debug("expecting SSH2_MSG_KEXDH_INIT"); 89 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init); 90 r = 0; 91 out: 92 return r; 93} 94 95int 96input_kex_dh_init(int type, u_int32_t seq, struct ssh *ssh) 97{ 98 struct kex *kex = ssh->kex; 99 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 100 const BIGNUM *pub_key; 101 struct sshkey *server_host_public, *server_host_private; 102 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; 103 u_char hash[SSH_DIGEST_MAX_LENGTH]; 104 size_t sbloblen, slen; 105 size_t klen = 0, hashlen; 106 int kout, r; 107 108 if (kex->load_host_public_key == NULL || 109 kex->load_host_private_key == NULL) { 110 r = SSH_ERR_INVALID_ARGUMENT; 111 goto out; 112 } 113 server_host_public = kex->load_host_public_key(kex->hostkey_type, 114 kex->hostkey_nid, ssh); 115 server_host_private = kex->load_host_private_key(kex->hostkey_type, 116 kex->hostkey_nid, ssh); 117 if (server_host_public == NULL) { 118 r = SSH_ERR_NO_HOSTKEY_LOADED; 119 goto out; 120 } 121 122 /* key, cert */ 123 if ((dh_client_pub = BN_new()) == NULL) { 124 r = SSH_ERR_ALLOC_FAIL; 125 goto out; 126 } 127 DH_get0_key(kex->dh, &pub_key, NULL); 128 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || 129 (r = sshpkt_get_end(ssh)) != 0) 130 goto out; 131 132#ifdef DEBUG_KEXDH 133 fprintf(stderr, "dh_client_pub= "); 134 BN_print_fp(stderr, dh_client_pub); 135 fprintf(stderr, "\n"); 136 debug("bits %d", BN_num_bits(dh_client_pub)); 137 DHparams_print_fp(stderr, kex->dh); 138 fprintf(stderr, "pub= "); 139 BN_print_fp(stderr, pub_key); 140 fprintf(stderr, "\n"); 141#endif 142 if (!dh_pub_is_valid(kex->dh, dh_client_pub)) { 143 sshpkt_disconnect(ssh, "bad client public DH value"); 144 r = SSH_ERR_MESSAGE_INCOMPLETE; 145 goto out; 146 } 147 148 klen = DH_size(kex->dh); 149 if ((kbuf = malloc(klen)) == NULL || 150 (shared_secret = BN_new()) == NULL) { 151 r = SSH_ERR_ALLOC_FAIL; 152 goto out; 153 } 154 if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 || 155 BN_bin2bn(kbuf, kout, shared_secret) == NULL) { 156 r = SSH_ERR_LIBCRYPTO_ERROR; 157 goto out; 158 } 159#ifdef DEBUG_KEXDH 160 dump_digest("shared secret", kbuf, kout); 161#endif 162 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, 163 &sbloblen)) != 0) 164 goto out; 165 /* calc H */ 166 hashlen = sizeof(hash); 167 if ((r = kex_dh_hash( 168 kex->hash_alg, 169 kex->client_version_string, 170 kex->server_version_string, 171 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 172 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 173 server_host_key_blob, sbloblen, 174 dh_client_pub, 175 pub_key, 176 shared_secret, 177 hash, &hashlen)) != 0) 178 goto out; 179 180 /* save session id := H */ 181 if (kex->session_id == NULL) { 182 kex->session_id_len = hashlen; 183 kex->session_id = malloc(kex->session_id_len); 184 if (kex->session_id == NULL) { 185 r = SSH_ERR_ALLOC_FAIL; 186 goto out; 187 } 188 memcpy(kex->session_id, hash, kex->session_id_len); 189 } 190 191 /* sign H */ 192 if ((r = kex->sign(server_host_private, server_host_public, &signature, 193 &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0) 194 goto out; 195 196 /* destroy_sensitive_data(); */ 197 198 /* send server hostkey, DH pubkey 'f' and signed H */ 199 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 || 200 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || 201 (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */ 202 (r = sshpkt_put_string(ssh, signature, slen)) != 0 || 203 (r = sshpkt_send(ssh)) != 0) 204 goto out; 205 206 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 207 r = kex_send_newkeys(ssh); 208 out: 209 explicit_bzero(hash, sizeof(hash)); 210 DH_free(kex->dh); 211 kex->dh = NULL; 212 BN_clear_free(dh_client_pub); 213 if (kbuf) { 214 explicit_bzero(kbuf, klen); 215 free(kbuf); 216 } 217 BN_clear_free(shared_secret); 218 free(server_host_key_blob); 219 free(signature); 220 return r; 221} 222#endif /* WITH_OPENSSL */ 223