1/* $OpenBSD: kexdhs.c,v 1.12 2010/11/10 01:33:07 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#ifdef __APPLE_CRYPTO__ 35#include "ossl-dh.h" 36#else 37#include <openssl/dh.h> 38#endif 39 40#include "xmalloc.h" 41#include "buffer.h" 42#include "key.h" 43#include "cipher.h" 44#include "kex.h" 45#include "log.h" 46#include "packet.h" 47#include "dh.h" 48#include "ssh2.h" 49#ifdef GSSAPI 50#include "ssh-gss.h" 51#endif 52#include "monitor_wrap.h" 53 54void 55kexdh_server(Kex *kex) 56{ 57 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 58 DH *dh; 59 Key *server_host_public, *server_host_private; 60 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 61 u_int sbloblen, klen, hashlen, slen; 62 int kout; 63 64 /* generate server DH public key */ 65 switch (kex->kex_type) { 66 case KEX_DH_GRP1_SHA1: 67 dh = dh_new_group1(); 68 break; 69 case KEX_DH_GRP14_SHA1: 70 dh = dh_new_group14(); 71 break; 72 default: 73 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); 74 } 75 dh_gen_key(dh, kex->we_need * 8); 76 77 debug("expecting SSH2_MSG_KEXDH_INIT"); 78 packet_read_expect(SSH2_MSG_KEXDH_INIT); 79 80 if (kex->load_host_public_key == NULL || 81 kex->load_host_private_key == NULL) 82 fatal("Cannot load hostkey"); 83 server_host_public = kex->load_host_public_key(kex->hostkey_type); 84 if (server_host_public == NULL) 85 fatal("Unsupported hostkey type %d", kex->hostkey_type); 86 server_host_private = kex->load_host_private_key(kex->hostkey_type); 87 if (server_host_private == NULL) 88 fatal("Missing private key for hostkey type %d", 89 kex->hostkey_type); 90 91 /* key, cert */ 92 if ((dh_client_pub = BN_new()) == NULL) 93 fatal("dh_client_pub == NULL"); 94 packet_get_bignum2(dh_client_pub); 95 packet_check_eom(); 96 97#ifdef DEBUG_KEXDH 98 fprintf(stderr, "dh_client_pub= "); 99 BN_print_fp(stderr, dh_client_pub); 100 fprintf(stderr, "\n"); 101 debug("bits %d", BN_num_bits(dh_client_pub)); 102#endif 103 104#ifdef DEBUG_KEXDH 105 DHparams_print_fp(stderr, dh); 106 fprintf(stderr, "pub= "); 107 BN_print_fp(stderr, dh->pub_key); 108 fprintf(stderr, "\n"); 109#endif 110 if (!dh_pub_is_valid(dh, dh_client_pub)) 111 packet_disconnect("bad client public DH value"); 112 113 klen = DH_size(dh); 114 kbuf = xmalloc(klen); 115 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) 116 fatal("DH_compute_key: failed"); 117#ifdef DEBUG_KEXDH 118 dump_digest("shared secret", kbuf, kout); 119#endif 120 if ((shared_secret = BN_new()) == NULL) 121 fatal("kexdh_server: BN_new failed"); 122 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 123 fatal("kexdh_server: BN_bin2bn failed"); 124 memset(kbuf, 0, klen); 125 xfree(kbuf); 126 127 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); 128 129 /* calc H */ 130 kex_dh_hash( 131 kex->client_version_string, 132 kex->server_version_string, 133 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 134 buffer_ptr(&kex->my), buffer_len(&kex->my), 135 server_host_key_blob, sbloblen, 136 dh_client_pub, 137 dh->pub_key, 138 shared_secret, 139 &hash, &hashlen 140 ); 141 BN_clear_free(dh_client_pub); 142 143 /* save session id := H */ 144 if (kex->session_id == NULL) { 145 kex->session_id_len = hashlen; 146 kex->session_id = xmalloc(kex->session_id_len); 147 memcpy(kex->session_id, hash, kex->session_id_len); 148 } 149 150 /* sign H */ 151 if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash, 152 hashlen)) < 0) 153 fatal("kexdh_server: key_sign failed"); 154 155 /* destroy_sensitive_data(); */ 156 157 /* send server hostkey, DH pubkey 'f' and singed H */ 158 packet_start(SSH2_MSG_KEXDH_REPLY); 159 packet_put_string(server_host_key_blob, sbloblen); 160 packet_put_bignum2(dh->pub_key); /* f */ 161 packet_put_string(signature, slen); 162 packet_send(); 163 164 xfree(signature); 165 xfree(server_host_key_blob); 166 /* have keys, free DH */ 167 DH_free(dh); 168 169 kex_derive_keys(kex, hash, hashlen, shared_secret); 170 BN_clear_free(shared_secret); 171 kex_finish(kex); 172} 173