kexdhc.c revision 323129
1/* $OpenBSD: kexdhc.c,v 1.19 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 <openssl/dh.h> 33 34#include <stdarg.h> 35#include <stdio.h> 36#include <string.h> 37#include <signal.h> 38 39#include "sshkey.h" 40#include "cipher.h" 41#include "digest.h" 42#include "kex.h" 43#include "log.h" 44#include "packet.h" 45#include "dh.h" 46#include "ssh2.h" 47#include "dispatch.h" 48#include "compat.h" 49#include "ssherr.h" 50#include "sshbuf.h" 51 52static int input_kex_dh(int, u_int32_t, void *); 53 54int 55kexdh_client(struct ssh *ssh) 56{ 57 struct kex *kex = ssh->kex; 58 int r; 59 60 /* generate and send 'e', client 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 debug("sending SSH2_MSG_KEXDH_INIT"); 84 if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 || 85 (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 || 86 (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || 87 (r = sshpkt_send(ssh)) != 0) 88 goto out; 89#ifdef DEBUG_KEXDH 90 DHparams_print_fp(stderr, kex->dh); 91 fprintf(stderr, "pub= "); 92 BN_print_fp(stderr, kex->dh->pub_key); 93 fprintf(stderr, "\n"); 94#endif 95 debug("expecting SSH2_MSG_KEXDH_REPLY"); 96 ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh); 97 r = 0; 98 out: 99 return r; 100} 101 102static int 103input_kex_dh(int type, u_int32_t seq, void *ctxt) 104{ 105 struct ssh *ssh = ctxt; 106 struct kex *kex = ssh->kex; 107 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; 108 struct sshkey *server_host_key = NULL; 109 u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL; 110 u_char hash[SSH_DIGEST_MAX_LENGTH]; 111 size_t klen = 0, slen, sbloblen, hashlen; 112 int kout, r; 113 114 if (kex->verify_host_key == NULL) { 115 r = SSH_ERR_INVALID_ARGUMENT; 116 goto out; 117 } 118 /* key, cert */ 119 if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 120 &sbloblen)) != 0 || 121 (r = sshkey_from_blob(server_host_key_blob, sbloblen, 122 &server_host_key)) != 0) 123 goto out; 124 if (server_host_key->type != kex->hostkey_type || 125 (kex->hostkey_type == KEY_ECDSA && 126 server_host_key->ecdsa_nid != kex->hostkey_nid)) { 127 r = SSH_ERR_KEY_TYPE_MISMATCH; 128 goto out; 129 } 130 if (kex->verify_host_key(server_host_key, ssh) == -1) { 131 r = SSH_ERR_SIGNATURE_INVALID; 132 goto out; 133 } 134 /* DH parameter f, server public DH key */ 135 if ((dh_server_pub = BN_new()) == NULL) { 136 r = SSH_ERR_ALLOC_FAIL; 137 goto out; 138 } 139 /* signed H */ 140 if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 || 141 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 142 (r = sshpkt_get_end(ssh)) != 0) 143 goto out; 144#ifdef DEBUG_KEXDH 145 fprintf(stderr, "dh_server_pub= "); 146 BN_print_fp(stderr, dh_server_pub); 147 fprintf(stderr, "\n"); 148 debug("bits %d", BN_num_bits(dh_server_pub)); 149#endif 150 if (!dh_pub_is_valid(kex->dh, dh_server_pub)) { 151 sshpkt_disconnect(ssh, "bad server public DH value"); 152 r = SSH_ERR_MESSAGE_INCOMPLETE; 153 goto out; 154 } 155 156 klen = DH_size(kex->dh); 157 if ((kbuf = malloc(klen)) == NULL || 158 (shared_secret = BN_new()) == NULL) { 159 r = SSH_ERR_ALLOC_FAIL; 160 goto out; 161 } 162 if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 || 163 BN_bin2bn(kbuf, kout, shared_secret) == NULL) { 164 r = SSH_ERR_LIBCRYPTO_ERROR; 165 goto out; 166 } 167#ifdef DEBUG_KEXDH 168 dump_digest("shared secret", kbuf, kout); 169#endif 170 171 /* calc and verify H */ 172 hashlen = sizeof(hash); 173 if ((r = kex_dh_hash( 174 kex->hash_alg, 175 kex->client_version_string, 176 kex->server_version_string, 177 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 178 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 179 server_host_key_blob, sbloblen, 180 kex->dh->pub_key, 181 dh_server_pub, 182 shared_secret, 183 hash, &hashlen)) != 0) 184 goto out; 185 186 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen, 187 ssh->compat)) != 0) 188 goto out; 189 190 /* save session id */ 191 if (kex->session_id == NULL) { 192 kex->session_id_len = hashlen; 193 kex->session_id = malloc(kex->session_id_len); 194 if (kex->session_id == NULL) { 195 r = SSH_ERR_ALLOC_FAIL; 196 goto out; 197 } 198 memcpy(kex->session_id, hash, kex->session_id_len); 199 } 200 201 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) 202 r = kex_send_newkeys(ssh); 203 out: 204 explicit_bzero(hash, sizeof(hash)); 205 DH_free(kex->dh); 206 kex->dh = NULL; 207 if (dh_server_pub) 208 BN_clear_free(dh_server_pub); 209 if (kbuf) { 210 explicit_bzero(kbuf, klen); 211 free(kbuf); 212 } 213 if (shared_secret) 214 BN_clear_free(shared_secret); 215 sshkey_free(server_host_key); 216 free(server_host_key_blob); 217 free(signature); 218 return r; 219} 220#endif /* WITH_OPENSSL */ 221