kexdhs.c revision 272461
1/* $OpenBSD: kexdhs.c,v 1.18 2014/02/02 03:44:31 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#include <sys/types.h> 29 30#include <stdarg.h> 31#include <string.h> 32#include <signal.h> 33 34#include <openssl/dh.h> 35 36#include "xmalloc.h" 37#include "buffer.h" 38#include "key.h" 39#include "cipher.h" 40#include "kex.h" 41#include "log.h" 42#include "packet.h" 43#include "dh.h" 44#include "ssh2.h" 45 46void 47kexdh_server(Kex *kex) 48{ 49 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 50 DH *dh; 51 Key *server_host_public, *server_host_private; 52 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 53 u_int sbloblen, klen, hashlen, slen; 54 int kout; 55 56 /* generate server DH public key */ 57 switch (kex->kex_type) { 58 case KEX_DH_GRP1_SHA1: 59 dh = dh_new_group1(); 60 break; 61 case KEX_DH_GRP14_SHA1: 62 dh = dh_new_group14(); 63 break; 64 default: 65 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); 66 } 67 dh_gen_key(dh, kex->we_need * 8); 68 69 debug("expecting SSH2_MSG_KEXDH_INIT"); 70 packet_read_expect(SSH2_MSG_KEXDH_INIT); 71 72 if (kex->load_host_public_key == NULL || 73 kex->load_host_private_key == NULL) 74 fatal("Cannot load hostkey"); 75 server_host_public = kex->load_host_public_key(kex->hostkey_type); 76 if (server_host_public == NULL) 77 fatal("Unsupported hostkey type %d", kex->hostkey_type); 78 server_host_private = kex->load_host_private_key(kex->hostkey_type); 79 80 /* key, cert */ 81 if ((dh_client_pub = BN_new()) == NULL) 82 fatal("dh_client_pub == NULL"); 83 packet_get_bignum2(dh_client_pub); 84 packet_check_eom(); 85 86#ifdef DEBUG_KEXDH 87 fprintf(stderr, "dh_client_pub= "); 88 BN_print_fp(stderr, dh_client_pub); 89 fprintf(stderr, "\n"); 90 debug("bits %d", BN_num_bits(dh_client_pub)); 91#endif 92 93#ifdef DEBUG_KEXDH 94 DHparams_print_fp(stderr, dh); 95 fprintf(stderr, "pub= "); 96 BN_print_fp(stderr, dh->pub_key); 97 fprintf(stderr, "\n"); 98#endif 99 if (!dh_pub_is_valid(dh, dh_client_pub)) 100 packet_disconnect("bad client public DH value"); 101 102 klen = DH_size(dh); 103 kbuf = xmalloc(klen); 104 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) 105 fatal("DH_compute_key: failed"); 106#ifdef DEBUG_KEXDH 107 dump_digest("shared secret", kbuf, kout); 108#endif 109 if ((shared_secret = BN_new()) == NULL) 110 fatal("kexdh_server: BN_new failed"); 111 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 112 fatal("kexdh_server: BN_bin2bn failed"); 113 explicit_bzero(kbuf, klen); 114 free(kbuf); 115 116 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); 117 118 /* calc H */ 119 kex_dh_hash( 120 kex->client_version_string, 121 kex->server_version_string, 122 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 123 buffer_ptr(&kex->my), buffer_len(&kex->my), 124 server_host_key_blob, sbloblen, 125 dh_client_pub, 126 dh->pub_key, 127 shared_secret, 128 &hash, &hashlen 129 ); 130 BN_clear_free(dh_client_pub); 131 132 /* save session id := H */ 133 if (kex->session_id == NULL) { 134 kex->session_id_len = hashlen; 135 kex->session_id = xmalloc(kex->session_id_len); 136 memcpy(kex->session_id, hash, kex->session_id_len); 137 } 138 139 /* sign H */ 140 kex->sign(server_host_private, server_host_public, &signature, &slen, 141 hash, hashlen); 142 143 /* destroy_sensitive_data(); */ 144 145 /* send server hostkey, DH pubkey 'f' and singed H */ 146 packet_start(SSH2_MSG_KEXDH_REPLY); 147 packet_put_string(server_host_key_blob, sbloblen); 148 packet_put_bignum2(dh->pub_key); /* f */ 149 packet_put_string(signature, slen); 150 packet_send(); 151 152 free(signature); 153 free(server_host_key_blob); 154 /* have keys, free DH */ 155 DH_free(dh); 156 157 kex_derive_keys_bn(kex, hash, hashlen, shared_secret); 158 BN_clear_free(shared_secret); 159 kex_finish(kex); 160} 161