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_client(Kex *kex) 46*0Sstevel@tonic-gate { 47*0Sstevel@tonic-gate BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; 48*0Sstevel@tonic-gate DH *dh; 49*0Sstevel@tonic-gate Key *server_host_key; 50*0Sstevel@tonic-gate u_char *server_host_key_blob = NULL, *signature = NULL; 51*0Sstevel@tonic-gate u_char *kbuf, *hash; 52*0Sstevel@tonic-gate u_int klen, kout, slen, sbloblen; 53*0Sstevel@tonic-gate 54*0Sstevel@tonic-gate /* generate and send 'e', client 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 packet_start(SSH2_MSG_KEXDH_INIT); 58*0Sstevel@tonic-gate packet_put_bignum2(dh->pub_key); 59*0Sstevel@tonic-gate packet_send(); 60*0Sstevel@tonic-gate 61*0Sstevel@tonic-gate debug("sending SSH2_MSG_KEXDH_INIT"); 62*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 63*0Sstevel@tonic-gate DHparams_print_fp(stderr, dh); 64*0Sstevel@tonic-gate fprintf(stderr, "pub= "); 65*0Sstevel@tonic-gate BN_print_fp(stderr, dh->pub_key); 66*0Sstevel@tonic-gate fprintf(stderr, "\n"); 67*0Sstevel@tonic-gate #endif 68*0Sstevel@tonic-gate 69*0Sstevel@tonic-gate debug("expecting SSH2_MSG_KEXDH_REPLY"); 70*0Sstevel@tonic-gate packet_read_expect(SSH2_MSG_KEXDH_REPLY); 71*0Sstevel@tonic-gate 72*0Sstevel@tonic-gate /* key, cert */ 73*0Sstevel@tonic-gate server_host_key_blob = packet_get_string(&sbloblen); 74*0Sstevel@tonic-gate server_host_key = key_from_blob(server_host_key_blob, sbloblen); 75*0Sstevel@tonic-gate if (server_host_key == NULL) 76*0Sstevel@tonic-gate fatal("cannot decode server_host_key_blob"); 77*0Sstevel@tonic-gate if (server_host_key->type != kex->hostkey_type) 78*0Sstevel@tonic-gate fatal("type mismatch for decoded server_host_key_blob"); 79*0Sstevel@tonic-gate if (kex->verify_host_key == NULL) 80*0Sstevel@tonic-gate fatal("cannot verify server_host_key"); 81*0Sstevel@tonic-gate if (kex->verify_host_key(server_host_key) == -1) 82*0Sstevel@tonic-gate fatal("server_host_key verification failed"); 83*0Sstevel@tonic-gate 84*0Sstevel@tonic-gate /* DH paramter f, server public DH key */ 85*0Sstevel@tonic-gate if ((dh_server_pub = BN_new()) == NULL) 86*0Sstevel@tonic-gate fatal("dh_server_pub == NULL"); 87*0Sstevel@tonic-gate packet_get_bignum2(dh_server_pub); 88*0Sstevel@tonic-gate 89*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 90*0Sstevel@tonic-gate fprintf(stderr, "dh_server_pub= "); 91*0Sstevel@tonic-gate BN_print_fp(stderr, dh_server_pub); 92*0Sstevel@tonic-gate fprintf(stderr, "\n"); 93*0Sstevel@tonic-gate debug("bits %d", BN_num_bits(dh_server_pub)); 94*0Sstevel@tonic-gate #endif 95*0Sstevel@tonic-gate 96*0Sstevel@tonic-gate /* signed H */ 97*0Sstevel@tonic-gate signature = packet_get_string(&slen); 98*0Sstevel@tonic-gate packet_check_eom(); 99*0Sstevel@tonic-gate 100*0Sstevel@tonic-gate if (!dh_pub_is_valid(dh, dh_server_pub)) 101*0Sstevel@tonic-gate packet_disconnect("bad server public DH value"); 102*0Sstevel@tonic-gate 103*0Sstevel@tonic-gate klen = DH_size(dh); 104*0Sstevel@tonic-gate kbuf = xmalloc(klen); 105*0Sstevel@tonic-gate kout = DH_compute_key(kbuf, dh_server_pub, dh); 106*0Sstevel@tonic-gate #ifdef DEBUG_KEXDH 107*0Sstevel@tonic-gate dump_digest("shared secret", kbuf, kout); 108*0Sstevel@tonic-gate #endif 109*0Sstevel@tonic-gate if ((shared_secret = BN_new()) == NULL) 110*0Sstevel@tonic-gate fatal("kexdh_client: BN_new failed"); 111*0Sstevel@tonic-gate BN_bin2bn(kbuf, kout, shared_secret); 112*0Sstevel@tonic-gate memset(kbuf, 0, klen); 113*0Sstevel@tonic-gate xfree(kbuf); 114*0Sstevel@tonic-gate 115*0Sstevel@tonic-gate /* calc and verify H */ 116*0Sstevel@tonic-gate hash = kex_dh_hash( 117*0Sstevel@tonic-gate kex->client_version_string, 118*0Sstevel@tonic-gate kex->server_version_string, 119*0Sstevel@tonic-gate buffer_ptr(&kex->my), buffer_len(&kex->my), 120*0Sstevel@tonic-gate buffer_ptr(&kex->peer), buffer_len(&kex->peer), 121*0Sstevel@tonic-gate server_host_key_blob, sbloblen, 122*0Sstevel@tonic-gate dh->pub_key, 123*0Sstevel@tonic-gate dh_server_pub, 124*0Sstevel@tonic-gate shared_secret 125*0Sstevel@tonic-gate ); 126*0Sstevel@tonic-gate xfree(server_host_key_blob); 127*0Sstevel@tonic-gate BN_clear_free(dh_server_pub); 128*0Sstevel@tonic-gate DH_free(dh); 129*0Sstevel@tonic-gate 130*0Sstevel@tonic-gate if (key_verify(server_host_key, signature, slen, hash, 20) != 1) 131*0Sstevel@tonic-gate fatal("key_verify failed for server_host_key"); 132*0Sstevel@tonic-gate key_free(server_host_key); 133*0Sstevel@tonic-gate xfree(signature); 134*0Sstevel@tonic-gate 135*0Sstevel@tonic-gate /* save session id */ 136*0Sstevel@tonic-gate if (kex->session_id == NULL) { 137*0Sstevel@tonic-gate kex->session_id_len = 20; 138*0Sstevel@tonic-gate kex->session_id = xmalloc(kex->session_id_len); 139*0Sstevel@tonic-gate memcpy(kex->session_id, hash, kex->session_id_len); 140*0Sstevel@tonic-gate } 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