1/* $OpenBSD: kexdhc.c,v 1.22 2018/02/07 02:06:51 jsing 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 <openssl/dh.h> 33 34#include <stdarg.h> 35#include <stdio.h> 36#include <string.h> 37#include <signal.h> 38 39#include "openbsd-compat/openssl-compat.h" 40 41#include "sshkey.h" 42#include "cipher.h" 43#include "digest.h" 44#include "kex.h" 45#include "log.h" 46#include "packet.h" 47#include "dh.h" 48#include "ssh2.h" 49#include "dispatch.h" 50#include "compat.h" 51#include "ssherr.h" 52#include "sshbuf.h" 53 54static int input_kex_dh(int, u_int32_t, struct ssh *); 55 56int 57kexdh_client(struct ssh *ssh) 58{ 59 struct kex *kex = ssh->kex; 60 int r; 61 const BIGNUM *pub_key; 62 63 /* generate and send 'e', client DH public key */ 64 switch (kex->kex_type) { 65 case KEX_DH_GRP1_SHA1: 66 kex->dh = dh_new_group1(); 67 break; 68 case KEX_DH_GRP14_SHA1: 69 case KEX_DH_GRP14_SHA256: 70 kex->dh = dh_new_group14(); 71 break; 72 case KEX_DH_GRP16_SHA512: 73 kex->dh = dh_new_group16(); 74 break; 75 case KEX_DH_GRP18_SHA512: 76 kex->dh = dh_new_group18(); 77 break; 78 default: 79 r = SSH_ERR_INVALID_ARGUMENT; 80 goto out; 81 } 82 if (kex->dh == NULL) { 83 r = SSH_ERR_ALLOC_FAIL; 84 goto out; 85 } 86 debug("sending SSH2_MSG_KEXDH_INIT"); 87 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) 88 goto out; 89 DH_get0_key(kex->dh, &pub_key, NULL); 90 if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 || 91 (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || 92 (r = sshpkt_send(ssh)) != 0) 93 goto out; 94#ifdef DEBUG_KEXDH 95 DHparams_print_fp(stderr, kex->dh); 96 fprintf(stderr, "pub= "); 97 BN_print_fp(stderr, pub_key); 98 fprintf(stderr, "\n"); 99#endif 100 debug("expecting SSH2_MSG_KEXDH_REPLY"); 101 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh); 102 r = 0; 103 out: 104 return r; 105} 106 107static int 108input_kex_dh(int type, u_int32_t seq, struct ssh *ssh) 109{ 110 struct kex *kex = ssh->kex; 111 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; 112 const BIGNUM *pub_key; 113 struct sshkey *server_host_key = NULL; 114 u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL; 115 u_char hash[SSH_DIGEST_MAX_LENGTH]; 116 size_t klen = 0, slen, sbloblen, hashlen; 117 int kout, r; 118 119 if (kex->verify_host_key == NULL) { 120 r = SSH_ERR_INVALID_ARGUMENT; 121 goto out; 122 } 123 /* key, cert */ 124 if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 125 &sbloblen)) != 0 || 126 (r = sshkey_from_blob(server_host_key_blob, sbloblen, 127 &server_host_key)) != 0) 128 goto out; 129 if (server_host_key->type != kex->hostkey_type || 130 (kex->hostkey_type == KEY_ECDSA && 131 server_host_key->ecdsa_nid != kex->hostkey_nid)) { 132 r = SSH_ERR_KEY_TYPE_MISMATCH; 133 goto out; 134 } 135 if (kex->verify_host_key(server_host_key, ssh) == -1) { 136 r = SSH_ERR_SIGNATURE_INVALID; 137 goto out; 138 } 139 /* DH parameter f, server public DH key */ 140 if ((dh_server_pub = BN_new()) == NULL) { 141 r = SSH_ERR_ALLOC_FAIL; 142 goto out; 143 } 144 /* signed H */ 145 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 || 146 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 147 (r = sshpkt_get_end(ssh)) != 0) 148 goto out; 149#ifdef DEBUG_KEXDH 150 fprintf(stderr, "dh_server_pub= "); 151 BN_print_fp(stderr, dh_server_pub); 152 fprintf(stderr, "\n"); 153 debug("bits %d", BN_num_bits(dh_server_pub)); 154#endif 155 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) { 156 sshpkt_disconnect(ssh, "bad server public DH value"); 157 r = SSH_ERR_MESSAGE_INCOMPLETE; 158 goto out; 159 } 160 161 klen = DH_size(kex->dh); 162 if ((kbuf = malloc(klen)) == NULL || 163 (shared_secret = BN_new()) == NULL) { 164 r = SSH_ERR_ALLOC_FAIL; 165 goto out; 166 } 167 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 || 168 BN_bin2bn(kbuf, kout, shared_secret) == NULL) { 169 r = SSH_ERR_LIBCRYPTO_ERROR; 170 goto out; 171 } 172#ifdef DEBUG_KEXDH 173 dump_digest("shared secret", kbuf, kout); 174#endif 175 176 /* calc and verify H */ 177 DH_get0_key(kex->dh, &pub_key, NULL); 178 hashlen = sizeof(hash); 179 if ((r = kex_dh_hash( 180 kex->hash_alg, 181 kex->client_version_string, 182 kex->server_version_string, 183 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 184 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 185 server_host_key_blob, sbloblen, 186 pub_key, 187 dh_server_pub, 188 shared_secret, 189 hash, &hashlen)) != 0) 190 goto out; 191 192 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen, 193 kex->hostkey_alg, ssh->compat)) != 0) 194 goto out; 195 196 /* save session id */ 197 if (kex->session_id == NULL) { 198 kex->session_id_len = hashlen; 199 kex->session_id = malloc(kex->session_id_len); 200 if (kex->session_id == NULL) { 201 r = SSH_ERR_ALLOC_FAIL; 202 goto out; 203 } 204 memcpy(kex->session_id, hash, kex->session_id_len); 205 } 206 207 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 208 r = kex_send_newkeys(ssh); 209 out: 210 explicit_bzero(hash, sizeof(hash)); 211 DH_free(kex->dh); 212 kex->dh = NULL; 213 BN_clear_free(dh_server_pub); 214 if (kbuf) { 215 explicit_bzero(kbuf, klen); 216 free(kbuf); 217 } 218 BN_clear_free(shared_secret); 219 sshkey_free(server_host_key); 220 free(server_host_key_blob); 221 free(signature); 222 return r; 223} 224#endif /* WITH_OPENSSL */ 225