kexdhs.c revision 323121
1/* $OpenBSD: kexdhs.c,v 1.23 2015/12/04 16:41:28 markus 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 kex->dh = dh_new_group14(); 67 break; 68 default: 69 r = SSH_ERR_INVALID_ARGUMENT; 70 goto out; 71 } 72 if (kex->dh == NULL) { 73 r = SSH_ERR_ALLOC_FAIL; 74 goto out; 75 } 76 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) 77 goto out; 78 79 debug("expecting SSH2_MSG_KEXDH_INIT"); 80 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init); 81 r = 0; 82 out: 83 return r; 84} 85 86int 87input_kex_dh_init(int type, u_int32_t seq, void *ctxt) 88{ 89 struct ssh *ssh = ctxt; 90 struct kex *kex = ssh->kex; 91 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 92 struct sshkey *server_host_public, *server_host_private; 93 u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; 94 u_char hash[SSH_DIGEST_MAX_LENGTH]; 95 size_t sbloblen, slen; 96 size_t klen = 0, hashlen; 97 int kout, r; 98 99 if (kex->load_host_public_key == NULL || 100 kex->load_host_private_key == NULL) { 101 r = SSH_ERR_INVALID_ARGUMENT; 102 goto out; 103 } 104 server_host_public = kex->load_host_public_key(kex->hostkey_type, 105 kex->hostkey_nid, ssh); 106 server_host_private = kex->load_host_private_key(kex->hostkey_type, 107 kex->hostkey_nid, ssh); 108 if (server_host_public == NULL) { 109 r = SSH_ERR_NO_HOSTKEY_LOADED; 110 goto out; 111 } 112 113 /* key, cert */ 114 if ((dh_client_pub = BN_new()) == NULL) { 115 r = SSH_ERR_ALLOC_FAIL; 116 goto out; 117 } 118 if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || 119 (r = sshpkt_get_end(ssh)) != 0) 120 goto out; 121 122#ifdef DEBUG_KEXDH 123 fprintf(stderr, "dh_client_pub= "); 124 BN_print_fp(stderr, dh_client_pub); 125 fprintf(stderr, "\n"); 126 debug("bits %d", BN_num_bits(dh_client_pub)); 127#endif 128 129#ifdef DEBUG_KEXDH 130 DHparams_print_fp(stderr, kex->dh); 131 fprintf(stderr, "pub= "); 132 BN_print_fp(stderr, kex->dh->pub_key); 133 fprintf(stderr, "\n"); 134#endif 135 if (!dh_pub_is_valid(kex->dh, dh_client_pub)) { 136 sshpkt_disconnect(ssh, "bad client public DH value"); 137 r = SSH_ERR_MESSAGE_INCOMPLETE; 138 goto out; 139 } 140 141 klen = DH_size(kex->dh); 142 if ((kbuf = malloc(klen)) == NULL || 143 (shared_secret = BN_new()) == NULL) { 144 r = SSH_ERR_ALLOC_FAIL; 145 goto out; 146 } 147 if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 || 148 BN_bin2bn(kbuf, kout, shared_secret) == NULL) { 149 r = SSH_ERR_LIBCRYPTO_ERROR; 150 goto out; 151 } 152#ifdef DEBUG_KEXDH 153 dump_digest("shared secret", kbuf, kout); 154#endif 155 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, 156 &sbloblen)) != 0) 157 goto out; 158 /* calc H */ 159 hashlen = sizeof(hash); 160 if ((r = kex_dh_hash( 161 kex->client_version_string, 162 kex->server_version_string, 163 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 164 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 165 server_host_key_blob, sbloblen, 166 dh_client_pub, 167 kex->dh->pub_key, 168 shared_secret, 169 hash, &hashlen)) != 0) 170 goto out; 171 172 /* save session id := H */ 173 if (kex->session_id == NULL) { 174 kex->session_id_len = hashlen; 175 kex->session_id = malloc(kex->session_id_len); 176 if (kex->session_id == NULL) { 177 r = SSH_ERR_ALLOC_FAIL; 178 goto out; 179 } 180 memcpy(kex->session_id, hash, kex->session_id_len); 181 } 182 183 /* sign H */ 184 if ((r = kex->sign(server_host_private, server_host_public, &signature, 185 &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0) 186 goto out; 187 188 /* destroy_sensitive_data(); */ 189 190 /* send server hostkey, DH pubkey 'f' and singed H */ 191 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 || 192 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || 193 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */ 194 (r = sshpkt_put_string(ssh, signature, slen)) != 0 || 195 (r = sshpkt_send(ssh)) != 0) 196 goto out; 197 198 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 199 r = kex_send_newkeys(ssh); 200 out: 201 explicit_bzero(hash, sizeof(hash)); 202 DH_free(kex->dh); 203 kex->dh = NULL; 204 if (dh_client_pub) 205 BN_clear_free(dh_client_pub); 206 if (kbuf) { 207 explicit_bzero(kbuf, klen); 208 free(kbuf); 209 } 210 if (shared_secret) 211 BN_clear_free(shared_secret); 212 free(server_host_key_blob); 213 free(signature); 214 return r; 215} 216#endif /* WITH_OPENSSL */ 217