kexdhs.c revision 113908
1140195Sdas/* 2140195Sdas * Copyright (c) 2001 Markus Friedl. All rights reserved. 3140195Sdas * 4140195Sdas * Redistribution and use in source and binary forms, with or without 5140195Sdas * modification, are permitted provided that the following conditions 6140195Sdas * are met: 7140195Sdas * 1. Redistributions of source code must retain the above copyright 8140195Sdas * notice, this list of conditions and the following disclaimer. 9140195Sdas * 2. Redistributions in binary form must reproduce the above copyright 10140195Sdas * notice, this list of conditions and the following disclaimer in the 11141280Sdas * documentation and/or other materials provided with the distribution. 12140195Sdas * 13140195Sdas * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14140195Sdas * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15140195Sdas * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16140195Sdas * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17140195Sdas * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18140195Sdas * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19140195Sdas * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20192760Sattilio * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21217108Skib * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22217108Skib * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25#include "includes.h" 26RCSID("$OpenBSD: kexdhs.c,v 1.1 2003/02/16 17:09:57 markus Exp $"); 27 28#include "xmalloc.h" 29#include "key.h" 30#include "kex.h" 31#include "log.h" 32#include "packet.h" 33#include "dh.h" 34#include "ssh2.h" 35#include "monitor_wrap.h" 36 37void 38kexdh_server(Kex *kex) 39{ 40 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 41 DH *dh; 42 Key *server_host_key; 43 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 44 u_int sbloblen, klen, kout; 45 u_int slen; 46 47 /* generate server DH public key */ 48 dh = dh_new_group1(); 49 dh_gen_key(dh, kex->we_need * 8); 50 51 debug("expecting SSH2_MSG_KEXDH_INIT"); 52 packet_read_expect(SSH2_MSG_KEXDH_INIT); 53 54 if (kex->load_host_key == NULL) 55 fatal("Cannot load hostkey"); 56 server_host_key = kex->load_host_key(kex->hostkey_type); 57 if (server_host_key == NULL) 58 fatal("Unsupported hostkey type %d", kex->hostkey_type); 59 60 /* key, cert */ 61 if ((dh_client_pub = BN_new()) == NULL) 62 fatal("dh_client_pub == NULL"); 63 packet_get_bignum2(dh_client_pub); 64 packet_check_eom(); 65 66#ifdef DEBUG_KEXDH 67 fprintf(stderr, "dh_client_pub= "); 68 BN_print_fp(stderr, dh_client_pub); 69 fprintf(stderr, "\n"); 70 debug("bits %d", BN_num_bits(dh_client_pub)); 71#endif 72 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 if (!dh_pub_is_valid(dh, dh_client_pub)) 80 packet_disconnect("bad client public DH value"); 81 82 klen = DH_size(dh); 83 kbuf = xmalloc(klen); 84 kout = DH_compute_key(kbuf, dh_client_pub, dh); 85#ifdef DEBUG_KEXDH 86 dump_digest("shared secret", kbuf, kout); 87#endif 88 if ((shared_secret = BN_new()) == NULL) 89 fatal("kexdh_server: BN_new failed"); 90 BN_bin2bn(kbuf, kout, shared_secret); 91 memset(kbuf, 0, klen); 92 xfree(kbuf); 93 94 key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); 95 96 /* calc H */ 97 hash = kex_dh_hash( 98 kex->client_version_string, 99 kex->server_version_string, 100 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 101 buffer_ptr(&kex->my), buffer_len(&kex->my), 102 server_host_key_blob, sbloblen, 103 dh_client_pub, 104 dh->pub_key, 105 shared_secret 106 ); 107 BN_clear_free(dh_client_pub); 108 109 /* save session id := H */ 110 /* XXX hashlen depends on KEX */ 111 if (kex->session_id == NULL) { 112 kex->session_id_len = 20; 113 kex->session_id = xmalloc(kex->session_id_len); 114 memcpy(kex->session_id, hash, kex->session_id_len); 115 } 116 117 /* sign H */ 118 /* XXX hashlen depends on KEX */ 119 PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20)); 120 121 /* destroy_sensitive_data(); */ 122 123 /* send server hostkey, DH pubkey 'f' and singed H */ 124 packet_start(SSH2_MSG_KEXDH_REPLY); 125 packet_put_string(server_host_key_blob, sbloblen); 126 packet_put_bignum2(dh->pub_key); /* f */ 127 packet_put_string(signature, slen); 128 packet_send(); 129 130 xfree(signature); 131 xfree(server_host_key_blob); 132 /* have keys, free DH */ 133 DH_free(dh); 134 135 kex_derive_keys(kex, hash, shared_secret); 136 BN_clear_free(shared_secret); 137 kex_finish(kex); 138} 139