kexdhc.c revision 181110
1/* $OpenBSD: kexdhc.c,v 1.11 2006/11/06 21:25:28 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 <stdio.h> 32#include <string.h> 33#include <signal.h> 34 35#include "xmalloc.h" 36#include "buffer.h" 37#include "key.h" 38#include "cipher.h" 39#include "kex.h" 40#include "log.h" 41#include "packet.h" 42#include "dh.h" 43#include "ssh2.h" 44 45void 46kexdh_client(Kex *kex) 47{ 48 BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; 49 DH *dh; 50 Key *server_host_key; 51 u_char *server_host_key_blob = NULL, *signature = NULL; 52 u_char *kbuf, *hash; 53 u_int klen, slen, sbloblen, hashlen; 54 int kout; 55 56 /* generate and send 'e', client 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 packet_start(SSH2_MSG_KEXDH_INIT); 69 packet_put_bignum2(dh->pub_key); 70 packet_send(); 71 72 debug("sending SSH2_MSG_KEXDH_INIT"); 73#ifdef DEBUG_KEXDH 74 DHparams_print_fp(stderr, dh); 75 fprintf(stderr, "pub= "); 76 BN_print_fp(stderr, dh->pub_key); 77 fprintf(stderr, "\n"); 78#endif 79 80 debug("expecting SSH2_MSG_KEXDH_REPLY"); 81 packet_read_expect(SSH2_MSG_KEXDH_REPLY); 82 83 /* key, cert */ 84 server_host_key_blob = packet_get_string(&sbloblen); 85 server_host_key = key_from_blob(server_host_key_blob, sbloblen); 86 if (server_host_key == NULL) 87 fatal("cannot decode server_host_key_blob"); 88 if (server_host_key->type != kex->hostkey_type) 89 fatal("type mismatch for decoded server_host_key_blob"); 90 if (kex->verify_host_key == NULL) 91 fatal("cannot verify server_host_key"); 92 if (kex->verify_host_key(server_host_key) == -1) 93 fatal("server_host_key verification failed"); 94 95 /* DH parameter f, server public DH key */ 96 if ((dh_server_pub = BN_new()) == NULL) 97 fatal("dh_server_pub == NULL"); 98 packet_get_bignum2(dh_server_pub); 99 100#ifdef DEBUG_KEXDH 101 fprintf(stderr, "dh_server_pub= "); 102 BN_print_fp(stderr, dh_server_pub); 103 fprintf(stderr, "\n"); 104 debug("bits %d", BN_num_bits(dh_server_pub)); 105#endif 106 107 /* signed H */ 108 signature = packet_get_string(&slen); 109 packet_check_eom(); 110 111 if (!dh_pub_is_valid(dh, dh_server_pub)) 112 packet_disconnect("bad server public DH value"); 113 114 klen = DH_size(dh); 115 kbuf = xmalloc(klen); 116 if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0) 117 fatal("DH_compute_key: failed"); 118#ifdef DEBUG_KEXDH 119 dump_digest("shared secret", kbuf, kout); 120#endif 121 if ((shared_secret = BN_new()) == NULL) 122 fatal("kexdh_client: BN_new failed"); 123 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 124 fatal("kexdh_client: BN_bin2bn failed"); 125 memset(kbuf, 0, klen); 126 xfree(kbuf); 127 128 /* calc and verify H */ 129 kex_dh_hash( 130 kex->client_version_string, 131 kex->server_version_string, 132 buffer_ptr(&kex->my), buffer_len(&kex->my), 133 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 134 server_host_key_blob, sbloblen, 135 dh->pub_key, 136 dh_server_pub, 137 shared_secret, 138 &hash, &hashlen 139 ); 140 xfree(server_host_key_blob); 141 BN_clear_free(dh_server_pub); 142 DH_free(dh); 143 144 if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) 145 fatal("key_verify failed for server_host_key"); 146 key_free(server_host_key); 147 xfree(signature); 148 149 /* save session id */ 150 if (kex->session_id == NULL) { 151 kex->session_id_len = hashlen; 152 kex->session_id = xmalloc(kex->session_id_len); 153 memcpy(kex->session_id, hash, kex->session_id_len); 154 } 155 156 kex_derive_keys(kex, hash, hashlen, shared_secret); 157 BN_clear_free(shared_secret); 158 kex_finish(kex); 159} 160