1*0Sstevel@tonic-gate /* 2*0Sstevel@tonic-gate * Copyright (c) 2001 Markus Friedl. All rights reserved. 3*0Sstevel@tonic-gate * 4*0Sstevel@tonic-gate * Redistribution and use in source and binary forms, with or without 5*0Sstevel@tonic-gate * modification, are permitted provided that the following conditions 6*0Sstevel@tonic-gate * are met: 7*0Sstevel@tonic-gate * 1. Redistributions of source code must retain the above copyright 8*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer. 9*0Sstevel@tonic-gate * 2. Redistributions in binary form must reproduce the above copyright 10*0Sstevel@tonic-gate * notice, this list of conditions and the following disclaimer in the 11*0Sstevel@tonic-gate * documentation and/or other materials provided with the distribution. 12*0Sstevel@tonic-gate * 13*0Sstevel@tonic-gate * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14*0Sstevel@tonic-gate * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15*0Sstevel@tonic-gate * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16*0Sstevel@tonic-gate * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17*0Sstevel@tonic-gate * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18*0Sstevel@tonic-gate * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19*0Sstevel@tonic-gate * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20*0Sstevel@tonic-gate * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21*0Sstevel@tonic-gate * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22*0Sstevel@tonic-gate * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23*0Sstevel@tonic-gate */ 24*0Sstevel@tonic-gate 25*0Sstevel@tonic-gate #include "includes.h" 26*0Sstevel@tonic-gate RCSID("$OpenBSD: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $"); 27*0Sstevel@tonic-gate 28*0Sstevel@tonic-gate #pragma ident "%Z%%M% %I% %E% SMI" 29*0Sstevel@tonic-gate 30*0Sstevel@tonic-gate #include <openssl/crypto.h> 31*0Sstevel@tonic-gate #include <openssl/bn.h> 32*0Sstevel@tonic-gate 33*0Sstevel@tonic-gate #include "xmalloc.h" 34*0Sstevel@tonic-gate #include "buffer.h" 35*0Sstevel@tonic-gate #include "bufaux.h" 36*0Sstevel@tonic-gate #include "key.h" 37*0Sstevel@tonic-gate #include "kex.h" 38*0Sstevel@tonic-gate #include "log.h" 39*0Sstevel@tonic-gate #include "packet.h" 40*0Sstevel@tonic-gate #include "dh.h" 41*0Sstevel@tonic-gate #include "ssh2.h" 42*0Sstevel@tonic-gate #include "monitor_wrap.h" 43*0Sstevel@tonic-gate 44*0Sstevel@tonic-gate void 45*0Sstevel@tonic-gate kexdh_server(Kex *kex) 46*0Sstevel@tonic-gate { 47*0Sstevel@tonic-gate BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 48*0Sstevel@tonic-gate DH *dh; 49*0Sstevel@tonic-gate Key *server_host_key; 50*0Sstevel@tonic-gate u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 51*0Sstevel@tonic-gate u_int sbloblen, klen, kout; 52*0Sstevel@tonic-gate u_int slen; 53*0Sstevel@tonic-gate 54*0Sstevel@tonic-gate /* generate server DH public key */ 55*0Sstevel@tonic-gate dh = dh_new_group1(); 56*0Sstevel@tonic-gate dh_gen_key(dh, kex->we_need * 8); 57*0Sstevel@tonic-gate 58*0Sstevel@tonic-gate debug("expecting SSH2_MSG_KEXDH_INIT"); 59*0Sstevel@tonic-gate packet_read_expect(SSH2_MSG_KEXDH_INIT); 60*0Sstevel@tonic-gate 61*0Sstevel@tonic-gate if (kex->load_host_key == NULL) 62*0Sstevel@tonic-gate fatal("Cannot load hostkey"); 63*0Sstevel@tonic-gate server_host_key = kex->load_host_key(kex->hostkey_type); 64*0Sstevel@tonic-gate if (server_host_key == NULL) 65*0Sstevel@tonic-gate fatal("Unsupported hostkey type %d", kex->hostkey_type); 66*0Sstevel@tonic-gate 67*0Sstevel@tonic-gate /* key, cert */ 68*0Sstevel@tonic-gate if ((dh_client_pub = BN_new()) == NULL) 69*0Sstevel@tonic-gate fatal("dh_client_pub == NULL"); 70*0Sstevel@tonic-gate packet_get_bignum2(dh_client_pub); 71*0Sstevel@tonic-gate packet_check_eom(); 72*0Sstevel@tonic-gate 73*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 74*0Sstevel@tonic-gate fprintf(stderr, "dh_client_pub= "); 75*0Sstevel@tonic-gate BN_print_fp(stderr, dh_client_pub); 76*0Sstevel@tonic-gate fprintf(stderr, "\n"); 77*0Sstevel@tonic-gate debug("bits %d", BN_num_bits(dh_client_pub)); 78*0Sstevel@tonic-gate #endif 79*0Sstevel@tonic-gate 80*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 81*0Sstevel@tonic-gate DHparams_print_fp(stderr, dh); 82*0Sstevel@tonic-gate fprintf(stderr, "pub= "); 83*0Sstevel@tonic-gate BN_print_fp(stderr, dh->pub_key); 84*0Sstevel@tonic-gate fprintf(stderr, "\n"); 85*0Sstevel@tonic-gate #endif 86*0Sstevel@tonic-gate if (!dh_pub_is_valid(dh, dh_client_pub)) 87*0Sstevel@tonic-gate packet_disconnect("bad client public DH value"); 88*0Sstevel@tonic-gate 89*0Sstevel@tonic-gate klen = DH_size(dh); 90*0Sstevel@tonic-gate kbuf = xmalloc(klen); 91*0Sstevel@tonic-gate kout = DH_compute_key(kbuf, dh_client_pub, dh); 92*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 93*0Sstevel@tonic-gate dump_digest("shared secret", kbuf, kout); 94*0Sstevel@tonic-gate #endif 95*0Sstevel@tonic-gate if ((shared_secret = BN_new()) == NULL) 96*0Sstevel@tonic-gate fatal("kexdh_server: BN_new failed"); 97*0Sstevel@tonic-gate BN_bin2bn(kbuf, kout, shared_secret); 98*0Sstevel@tonic-gate memset(kbuf, 0, klen); 99*0Sstevel@tonic-gate xfree(kbuf); 100*0Sstevel@tonic-gate 101*0Sstevel@tonic-gate key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); 102*0Sstevel@tonic-gate 103*0Sstevel@tonic-gate /* calc H */ 104*0Sstevel@tonic-gate hash = kex_dh_hash( 105*0Sstevel@tonic-gate kex->client_version_string, 106*0Sstevel@tonic-gate kex->server_version_string, 107*0Sstevel@tonic-gate buffer_ptr(&kex->peer), buffer_len(&kex->peer), 108*0Sstevel@tonic-gate buffer_ptr(&kex->my), buffer_len(&kex->my), 109*0Sstevel@tonic-gate server_host_key_blob, sbloblen, 110*0Sstevel@tonic-gate dh_client_pub, 111*0Sstevel@tonic-gate dh->pub_key, 112*0Sstevel@tonic-gate shared_secret 113*0Sstevel@tonic-gate ); 114*0Sstevel@tonic-gate BN_clear_free(dh_client_pub); 115*0Sstevel@tonic-gate 116*0Sstevel@tonic-gate /* save session id := H */ 117*0Sstevel@tonic-gate /* XXX hashlen depends on KEX */ 118*0Sstevel@tonic-gate if (kex->session_id == NULL) { 119*0Sstevel@tonic-gate kex->session_id_len = 20; 120*0Sstevel@tonic-gate kex->session_id = xmalloc(kex->session_id_len); 121*0Sstevel@tonic-gate memcpy(kex->session_id, hash, kex->session_id_len); 122*0Sstevel@tonic-gate } 123*0Sstevel@tonic-gate 124*0Sstevel@tonic-gate /* sign H */ 125*0Sstevel@tonic-gate /* XXX hashlen depends on KEX */ 126*0Sstevel@tonic-gate PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20)); 127*0Sstevel@tonic-gate 128*0Sstevel@tonic-gate /* destroy_sensitive_data(); */ 129*0Sstevel@tonic-gate 130*0Sstevel@tonic-gate /* send server hostkey, DH pubkey 'f' and singed H */ 131*0Sstevel@tonic-gate packet_start(SSH2_MSG_KEXDH_REPLY); 132*0Sstevel@tonic-gate packet_put_string(server_host_key_blob, sbloblen); 133*0Sstevel@tonic-gate packet_put_bignum2(dh->pub_key); /* f */ 134*0Sstevel@tonic-gate packet_put_string(signature, slen); 135*0Sstevel@tonic-gate packet_send(); 136*0Sstevel@tonic-gate 137*0Sstevel@tonic-gate xfree(signature); 138*0Sstevel@tonic-gate xfree(server_host_key_blob); 139*0Sstevel@tonic-gate /* have keys, free DH */ 140*0Sstevel@tonic-gate DH_free(dh); 141*0Sstevel@tonic-gate 142*0Sstevel@tonic-gate kex_derive_keys(kex, hash, shared_secret); 143*0Sstevel@tonic-gate BN_clear_free(shared_secret); 144*0Sstevel@tonic-gate kex_finish(kex); 145*0Sstevel@tonic-gate } 146