1264377Sdes/* $OpenBSD: kexgexc.c,v 1.17 2014/02/02 03:44:31 djm Exp $ */ 2113908Sdes/* 3113908Sdes * Copyright (c) 2000 Niels Provos. All rights reserved. 4113908Sdes * Copyright (c) 2001 Markus Friedl. All rights reserved. 5113908Sdes * 6113908Sdes * Redistribution and use in source and binary forms, with or without 7113908Sdes * modification, are permitted provided that the following conditions 8113908Sdes * are met: 9113908Sdes * 1. Redistributions of source code must retain the above copyright 10113908Sdes * notice, this list of conditions and the following disclaimer. 11113908Sdes * 2. Redistributions in binary form must reproduce the above copyright 12113908Sdes * notice, this list of conditions and the following disclaimer in the 13113908Sdes * documentation and/or other materials provided with the distribution. 14113908Sdes * 15113908Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16113908Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17113908Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18113908Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19113908Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20113908Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21113908Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22113908Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23113908Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24113908Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25113908Sdes */ 26113908Sdes 27113908Sdes#include "includes.h" 28113908Sdes 29162852Sdes#include <sys/types.h> 30162852Sdes 31221420Sdes#include <openssl/dh.h> 32221420Sdes 33162852Sdes#include <stdarg.h> 34162852Sdes#include <stdio.h> 35162852Sdes#include <string.h> 36162852Sdes#include <signal.h> 37162852Sdes 38113908Sdes#include "xmalloc.h" 39162852Sdes#include "buffer.h" 40113908Sdes#include "key.h" 41162852Sdes#include "cipher.h" 42113908Sdes#include "kex.h" 43113908Sdes#include "log.h" 44113908Sdes#include "packet.h" 45113908Sdes#include "dh.h" 46113908Sdes#include "ssh2.h" 47113908Sdes#include "compat.h" 48113908Sdes 49113908Sdesvoid 50113908Sdeskexgex_client(Kex *kex) 51113908Sdes{ 52113908Sdes BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; 53113908Sdes BIGNUM *p = NULL, *g = NULL; 54113908Sdes Key *server_host_key; 55113908Sdes u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 56164146Sdes u_int klen, slen, sbloblen, hashlen; 57164146Sdes int kout; 58113908Sdes int min, max, nbits; 59113908Sdes DH *dh; 60113908Sdes 61262566Sdes nbits = dh_estimate(kex->dh_need * 8); 62113908Sdes 63113908Sdes if (datafellows & SSH_OLD_DHGEX) { 64113908Sdes /* Old GEX request */ 65113908Sdes packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD); 66113908Sdes packet_put_int(nbits); 67113908Sdes min = DH_GRP_MIN; 68113908Sdes max = DH_GRP_MAX; 69126274Sdes 70126274Sdes debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits); 71113908Sdes } else { 72113908Sdes /* New GEX request */ 73113908Sdes min = DH_GRP_MIN; 74113908Sdes max = DH_GRP_MAX; 75113908Sdes packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); 76113908Sdes packet_put_int(min); 77113908Sdes packet_put_int(nbits); 78113908Sdes packet_put_int(max); 79126274Sdes 80126274Sdes debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", 81126274Sdes min, nbits, max); 82113908Sdes } 83113908Sdes#ifdef DEBUG_KEXDH 84113908Sdes fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", 85113908Sdes min, nbits, max); 86113908Sdes#endif 87113908Sdes packet_send(); 88113908Sdes 89113908Sdes debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); 90113908Sdes packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP); 91113908Sdes 92113908Sdes if ((p = BN_new()) == NULL) 93113908Sdes fatal("BN_new"); 94113908Sdes packet_get_bignum2(p); 95113908Sdes if ((g = BN_new()) == NULL) 96113908Sdes fatal("BN_new"); 97113908Sdes packet_get_bignum2(g); 98113908Sdes packet_check_eom(); 99113908Sdes 100113908Sdes if (BN_num_bits(p) < min || BN_num_bits(p) > max) 101113908Sdes fatal("DH_GEX group out of range: %d !< %d !< %d", 102113908Sdes min, BN_num_bits(p), max); 103113908Sdes 104113908Sdes dh = dh_new_group(g, p); 105113908Sdes dh_gen_key(dh, kex->we_need * 8); 106113908Sdes 107113908Sdes#ifdef DEBUG_KEXDH 108113908Sdes DHparams_print_fp(stderr, dh); 109113908Sdes fprintf(stderr, "pub= "); 110113908Sdes BN_print_fp(stderr, dh->pub_key); 111113908Sdes fprintf(stderr, "\n"); 112113908Sdes#endif 113113908Sdes 114113908Sdes debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); 115113908Sdes /* generate and send 'e', client DH public key */ 116113908Sdes packet_start(SSH2_MSG_KEX_DH_GEX_INIT); 117113908Sdes packet_put_bignum2(dh->pub_key); 118113908Sdes packet_send(); 119113908Sdes 120113908Sdes debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); 121113908Sdes packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY); 122113908Sdes 123113908Sdes /* key, cert */ 124113908Sdes server_host_key_blob = packet_get_string(&sbloblen); 125113908Sdes server_host_key = key_from_blob(server_host_key_blob, sbloblen); 126113908Sdes if (server_host_key == NULL) 127113908Sdes fatal("cannot decode server_host_key_blob"); 128113908Sdes if (server_host_key->type != kex->hostkey_type) 129113908Sdes fatal("type mismatch for decoded server_host_key_blob"); 130113908Sdes if (kex->verify_host_key == NULL) 131113908Sdes fatal("cannot verify server_host_key"); 132113908Sdes if (kex->verify_host_key(server_host_key) == -1) 133113908Sdes fatal("server_host_key verification failed"); 134113908Sdes 135162852Sdes /* DH parameter f, server public DH key */ 136113908Sdes if ((dh_server_pub = BN_new()) == NULL) 137113908Sdes fatal("dh_server_pub == NULL"); 138113908Sdes packet_get_bignum2(dh_server_pub); 139113908Sdes 140113908Sdes#ifdef DEBUG_KEXDH 141113908Sdes fprintf(stderr, "dh_server_pub= "); 142113908Sdes BN_print_fp(stderr, dh_server_pub); 143113908Sdes fprintf(stderr, "\n"); 144113908Sdes debug("bits %d", BN_num_bits(dh_server_pub)); 145113908Sdes#endif 146113908Sdes 147113908Sdes /* signed H */ 148113908Sdes signature = packet_get_string(&slen); 149113908Sdes packet_check_eom(); 150113908Sdes 151113908Sdes if (!dh_pub_is_valid(dh, dh_server_pub)) 152113908Sdes packet_disconnect("bad server public DH value"); 153113908Sdes 154113908Sdes klen = DH_size(dh); 155113908Sdes kbuf = xmalloc(klen); 156164146Sdes if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0) 157164146Sdes fatal("DH_compute_key: failed"); 158113908Sdes#ifdef DEBUG_KEXDH 159113908Sdes dump_digest("shared secret", kbuf, kout); 160113908Sdes#endif 161113908Sdes if ((shared_secret = BN_new()) == NULL) 162113908Sdes fatal("kexgex_client: BN_new failed"); 163164146Sdes if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 164164146Sdes fatal("kexgex_client: BN_bin2bn failed"); 165264377Sdes explicit_bzero(kbuf, klen); 166255767Sdes free(kbuf); 167113908Sdes 168113908Sdes if (datafellows & SSH_OLD_DHGEX) 169113908Sdes min = max = -1; 170113908Sdes 171113908Sdes /* calc and verify H */ 172157016Sdes kexgex_hash( 173262566Sdes kex->hash_alg, 174113908Sdes kex->client_version_string, 175113908Sdes kex->server_version_string, 176113908Sdes buffer_ptr(&kex->my), buffer_len(&kex->my), 177113908Sdes buffer_ptr(&kex->peer), buffer_len(&kex->peer), 178113908Sdes server_host_key_blob, sbloblen, 179113908Sdes min, nbits, max, 180113908Sdes dh->p, dh->g, 181113908Sdes dh->pub_key, 182113908Sdes dh_server_pub, 183157016Sdes shared_secret, 184157016Sdes &hash, &hashlen 185113908Sdes ); 186157016Sdes 187113908Sdes /* have keys, free DH */ 188113908Sdes DH_free(dh); 189255767Sdes free(server_host_key_blob); 190113908Sdes BN_clear_free(dh_server_pub); 191113908Sdes 192157016Sdes if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) 193113908Sdes fatal("key_verify failed for server_host_key"); 194113908Sdes key_free(server_host_key); 195255767Sdes free(signature); 196113908Sdes 197113908Sdes /* save session id */ 198113908Sdes if (kex->session_id == NULL) { 199157016Sdes kex->session_id_len = hashlen; 200113908Sdes kex->session_id = xmalloc(kex->session_id_len); 201113908Sdes memcpy(kex->session_id, hash, kex->session_id_len); 202113908Sdes } 203262566Sdes kex_derive_keys_bn(kex, hash, hashlen, shared_secret); 204113908Sdes BN_clear_free(shared_secret); 205113908Sdes 206113908Sdes kex_finish(kex); 207113908Sdes} 208