kexdhs.c revision 323129
1/* $OpenBSD: kexdhs.c,v 1.24 2016/05/02 10:26:04 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 "sshkey.h" 39#include "cipher.h" 40#include "digest.h" 41#include "kex.h" 42#include "log.h" 43#include "packet.h" 44#include "dh.h" 45#include "ssh2.h" 46 47#include "dispatch.h" 48#include "compat.h" 49#include "ssherr.h" 50#include "sshbuf.h" 51 52static int input_kex_dh_init(int, u_int32_t, void *); 53 54int 55kexdh_server(struct ssh *ssh) 56{ 57 struct kex *kex = ssh->kex; 58 int r; 59 60 /* generate server DH public key */ 61 switch (kex->kex_type) { 62 case KEX_DH_GRP1_SHA1: 63 kex->dh = dh_new_group1(); 64 break; 65 case KEX_DH_GRP14_SHA1: 66 case KEX_DH_GRP14_SHA256: 67 kex->dh = dh_new_group14(); 68 break; 69 case KEX_DH_GRP16_SHA512: 70 kex->dh = dh_new_group16(); 71 break; 72 case KEX_DH_GRP18_SHA512: 73 kex->dh = dh_new_group18(); 74 break; 75 default: 76 r = SSH_ERR_INVALID_ARGUMENT; 77 goto out; 78 } 79 if (kex->dh == NULL) { 80 r = SSH_ERR_ALLOC_FAIL; 81 goto out; 82 } 83 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) 84 goto out; 85 86 debug("expecting SSH2_MSG_KEXDH_INIT"); 87 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init); 88 r = 0; 89 out: 90 return r; 91} 92 93int 94input_kex_dh_init(int type, u_int32_t seq, void *ctxt) 95{ 96 struct ssh *ssh = ctxt; 97 struct kex *kex = ssh->kex; 98 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 99 struct sshkey *server_host_public, *server_host_private; 100 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; 101 u_char hash[SSH_DIGEST_MAX_LENGTH]; 102 size_t sbloblen, slen; 103 size_t klen = 0, hashlen; 104 int kout, r; 105 106 if (kex->load_host_public_key == NULL || 107 kex->load_host_private_key == NULL) { 108 r = SSH_ERR_INVALID_ARGUMENT; 109 goto out; 110 } 111 server_host_public = kex->load_host_public_key(kex->hostkey_type, 112 kex->hostkey_nid, ssh); 113 server_host_private = kex->load_host_private_key(kex->hostkey_type, 114 kex->hostkey_nid, ssh); 115 if (server_host_public == NULL) { 116 r = SSH_ERR_NO_HOSTKEY_LOADED; 117 goto out; 118 } 119 120 /* key, cert */ 121 if ((dh_client_pub = BN_new()) == NULL) { 122 r = SSH_ERR_ALLOC_FAIL; 123 goto out; 124 } 125 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || 126 (r = sshpkt_get_end(ssh)) != 0) 127 goto out; 128 129#ifdef DEBUG_KEXDH 130 fprintf(stderr, "dh_client_pub= "); 131 BN_print_fp(stderr, dh_client_pub); 132 fprintf(stderr, "\n"); 133 debug("bits %d", BN_num_bits(dh_client_pub)); 134#endif 135 136#ifdef DEBUG_KEXDH 137 DHparams_print_fp(stderr, kex->dh); 138 fprintf(stderr, "pub= "); 139 BN_print_fp(stderr, kex->dh->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 kex->dh->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 singed 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, kex->dh->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 if (dh_client_pub) 213 BN_clear_free(dh_client_pub); 214 if (kbuf) { 215 explicit_bzero(kbuf, klen); 216 free(kbuf); 217 } 218 if (shared_secret) 219 BN_clear_free(shared_secret); 220 free(server_host_key_blob); 221 free(signature); 222 return r; 223} 224#endif /* WITH_OPENSSL */ 225