1/* $OpenBSD: kexdhs.c,v 1.14 2013/07/19 07:37:48 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#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#ifdef GSSAPI 46#include "ssh-gss.h" 47#endif 48#include "monitor_wrap.h" 49 50void 51kexdh_server(Kex *kex) 52{ 53 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 54 DH *dh; 55 Key *server_host_public, *server_host_private; 56 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 57 u_int sbloblen, klen, hashlen, slen; 58 int kout; 59 60 /* generate server DH public key */ 61 switch (kex->kex_type) { 62 case KEX_DH_GRP1_SHA1: 63 dh = dh_new_group1(); 64 break; 65 case KEX_DH_GRP14_SHA1: 66 dh = dh_new_group14(); 67 break; 68 default: 69 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); 70 } 71 dh_gen_key(dh, kex->we_need * 8); 72 73 debug("expecting SSH2_MSG_KEXDH_INIT"); 74 packet_read_expect(SSH2_MSG_KEXDH_INIT); 75 76 if (kex->load_host_public_key == NULL || 77 kex->load_host_private_key == NULL) 78 fatal("Cannot load hostkey"); 79 server_host_public = kex->load_host_public_key(kex->hostkey_type); 80 if (server_host_public == NULL) 81 fatal("Unsupported hostkey type %d", kex->hostkey_type); 82 server_host_private = kex->load_host_private_key(kex->hostkey_type); 83 84 /* key, cert */ 85 if ((dh_client_pub = BN_new()) == NULL) 86 fatal("dh_client_pub == NULL"); 87 packet_get_bignum2(dh_client_pub); 88 packet_check_eom(); 89 90#ifdef DEBUG_KEXDH 91 fprintf(stderr, "dh_client_pub= "); 92 BN_print_fp(stderr, dh_client_pub); 93 fprintf(stderr, "\n"); 94 debug("bits %d", BN_num_bits(dh_client_pub)); 95#endif 96 97#ifdef DEBUG_KEXDH 98 DHparams_print_fp(stderr, dh); 99 fprintf(stderr, "pub= "); 100 BN_print_fp(stderr, dh->pub_key); 101 fprintf(stderr, "\n"); 102#endif 103 if (!dh_pub_is_valid(dh, dh_client_pub)) 104 packet_disconnect("bad client public DH value"); 105 106 klen = DH_size(dh); 107 kbuf = xmalloc(klen); 108 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) 109 fatal("DH_compute_key: failed"); 110#ifdef DEBUG_KEXDH 111 dump_digest("shared secret", kbuf, kout); 112#endif 113 if ((shared_secret = BN_new()) == NULL) 114 fatal("kexdh_server: BN_new failed"); 115 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 116 fatal("kexdh_server: BN_bin2bn failed"); 117 memset(kbuf, 0, klen); 118 free(kbuf); 119 120 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); 121 122 /* calc H */ 123 kex_dh_hash( 124 kex->client_version_string, 125 kex->server_version_string, 126 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 127 buffer_ptr(&kex->my), buffer_len(&kex->my), 128 server_host_key_blob, sbloblen, 129 dh_client_pub, 130 dh->pub_key, 131 shared_secret, 132 &hash, &hashlen 133 ); 134 BN_clear_free(dh_client_pub); 135 136 /* save session id := H */ 137 if (kex->session_id == NULL) { 138 kex->session_id_len = hashlen; 139 kex->session_id = xmalloc(kex->session_id_len); 140 memcpy(kex->session_id, hash, kex->session_id_len); 141 } 142 143 /* sign H */ 144 kex->sign(server_host_private, server_host_public, &signature, &slen, 145 hash, hashlen); 146 147 /* destroy_sensitive_data(); */ 148 149 /* send server hostkey, DH pubkey 'f' and singed H */ 150 packet_start(SSH2_MSG_KEXDH_REPLY); 151 packet_put_string(server_host_key_blob, sbloblen); 152 packet_put_bignum2(dh->pub_key); /* f */ 153 packet_put_string(signature, slen); 154 packet_send(); 155 156 free(signature); 157 free(server_host_key_blob); 158 /* have keys, free DH */ 159 DH_free(dh); 160 161 kex_derive_keys(kex, hash, hashlen, shared_secret); 162 BN_clear_free(shared_secret); 163 kex_finish(kex); 164} 165