1*18de8d7fSPeter Avalos /* $OpenBSD: kexgexs.c,v 1.10 2006/11/06 21:25:28 markus Exp $ */ 2*18de8d7fSPeter Avalos /* 3*18de8d7fSPeter Avalos * Copyright (c) 2000 Niels Provos. All rights reserved. 4*18de8d7fSPeter Avalos * Copyright (c) 2001 Markus Friedl. All rights reserved. 5*18de8d7fSPeter Avalos * 6*18de8d7fSPeter Avalos * Redistribution and use in source and binary forms, with or without 7*18de8d7fSPeter Avalos * modification, are permitted provided that the following conditions 8*18de8d7fSPeter Avalos * are met: 9*18de8d7fSPeter Avalos * 1. Redistributions of source code must retain the above copyright 10*18de8d7fSPeter Avalos * notice, this list of conditions and the following disclaimer. 11*18de8d7fSPeter Avalos * 2. Redistributions in binary form must reproduce the above copyright 12*18de8d7fSPeter Avalos * notice, this list of conditions and the following disclaimer in the 13*18de8d7fSPeter Avalos * documentation and/or other materials provided with the distribution. 14*18de8d7fSPeter Avalos * 15*18de8d7fSPeter Avalos * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16*18de8d7fSPeter Avalos * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17*18de8d7fSPeter Avalos * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18*18de8d7fSPeter Avalos * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19*18de8d7fSPeter Avalos * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20*18de8d7fSPeter Avalos * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21*18de8d7fSPeter Avalos * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22*18de8d7fSPeter Avalos * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23*18de8d7fSPeter Avalos * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24*18de8d7fSPeter Avalos * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25*18de8d7fSPeter Avalos */ 26*18de8d7fSPeter Avalos 27*18de8d7fSPeter Avalos #include "includes.h" 28*18de8d7fSPeter Avalos 29*18de8d7fSPeter Avalos #include <sys/param.h> 30*18de8d7fSPeter Avalos 31*18de8d7fSPeter Avalos #include <stdarg.h> 32*18de8d7fSPeter Avalos #include <stdio.h> 33*18de8d7fSPeter Avalos #include <string.h> 34*18de8d7fSPeter Avalos #include <signal.h> 35*18de8d7fSPeter Avalos 36*18de8d7fSPeter Avalos #include "xmalloc.h" 37*18de8d7fSPeter Avalos #include "buffer.h" 38*18de8d7fSPeter Avalos #include "key.h" 39*18de8d7fSPeter Avalos #include "cipher.h" 40*18de8d7fSPeter Avalos #include "kex.h" 41*18de8d7fSPeter Avalos #include "log.h" 42*18de8d7fSPeter Avalos #include "packet.h" 43*18de8d7fSPeter Avalos #include "dh.h" 44*18de8d7fSPeter Avalos #include "ssh2.h" 45*18de8d7fSPeter Avalos #include "compat.h" 46*18de8d7fSPeter Avalos #ifdef GSSAPI 47*18de8d7fSPeter Avalos #include "ssh-gss.h" 48*18de8d7fSPeter Avalos #endif 49*18de8d7fSPeter Avalos #include "monitor_wrap.h" 50*18de8d7fSPeter Avalos 51*18de8d7fSPeter Avalos void 52*18de8d7fSPeter Avalos kexgex_server(Kex *kex) 53*18de8d7fSPeter Avalos { 54*18de8d7fSPeter Avalos BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 55*18de8d7fSPeter Avalos Key *server_host_key; 56*18de8d7fSPeter Avalos DH *dh; 57*18de8d7fSPeter Avalos u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 58*18de8d7fSPeter Avalos u_int sbloblen, klen, slen, hashlen; 59*18de8d7fSPeter Avalos int min = -1, max = -1, nbits = -1, type, kout; 60*18de8d7fSPeter Avalos 61*18de8d7fSPeter Avalos if (kex->load_host_key == NULL) 62*18de8d7fSPeter Avalos fatal("Cannot load hostkey"); 63*18de8d7fSPeter Avalos server_host_key = kex->load_host_key(kex->hostkey_type); 64*18de8d7fSPeter Avalos if (server_host_key == NULL) 65*18de8d7fSPeter Avalos fatal("Unsupported hostkey type %d", kex->hostkey_type); 66*18de8d7fSPeter Avalos 67*18de8d7fSPeter Avalos type = packet_read(); 68*18de8d7fSPeter Avalos switch (type) { 69*18de8d7fSPeter Avalos case SSH2_MSG_KEX_DH_GEX_REQUEST: 70*18de8d7fSPeter Avalos debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); 71*18de8d7fSPeter Avalos min = packet_get_int(); 72*18de8d7fSPeter Avalos nbits = packet_get_int(); 73*18de8d7fSPeter Avalos max = packet_get_int(); 74*18de8d7fSPeter Avalos min = MAX(DH_GRP_MIN, min); 75*18de8d7fSPeter Avalos max = MIN(DH_GRP_MAX, max); 76*18de8d7fSPeter Avalos break; 77*18de8d7fSPeter Avalos case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD: 78*18de8d7fSPeter Avalos debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received"); 79*18de8d7fSPeter Avalos nbits = packet_get_int(); 80*18de8d7fSPeter Avalos min = DH_GRP_MIN; 81*18de8d7fSPeter Avalos max = DH_GRP_MAX; 82*18de8d7fSPeter Avalos /* unused for old GEX */ 83*18de8d7fSPeter Avalos break; 84*18de8d7fSPeter Avalos default: 85*18de8d7fSPeter Avalos fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type); 86*18de8d7fSPeter Avalos } 87*18de8d7fSPeter Avalos packet_check_eom(); 88*18de8d7fSPeter Avalos 89*18de8d7fSPeter Avalos if (max < min || nbits < min || max < nbits) 90*18de8d7fSPeter Avalos fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d", 91*18de8d7fSPeter Avalos min, nbits, max); 92*18de8d7fSPeter Avalos 93*18de8d7fSPeter Avalos /* Contact privileged parent */ 94*18de8d7fSPeter Avalos dh = PRIVSEP(choose_dh(min, nbits, max)); 95*18de8d7fSPeter Avalos if (dh == NULL) 96*18de8d7fSPeter Avalos packet_disconnect("Protocol error: no matching DH grp found"); 97*18de8d7fSPeter Avalos 98*18de8d7fSPeter Avalos debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); 99*18de8d7fSPeter Avalos packet_start(SSH2_MSG_KEX_DH_GEX_GROUP); 100*18de8d7fSPeter Avalos packet_put_bignum2(dh->p); 101*18de8d7fSPeter Avalos packet_put_bignum2(dh->g); 102*18de8d7fSPeter Avalos packet_send(); 103*18de8d7fSPeter Avalos 104*18de8d7fSPeter Avalos /* flush */ 105*18de8d7fSPeter Avalos packet_write_wait(); 106*18de8d7fSPeter Avalos 107*18de8d7fSPeter Avalos /* Compute our exchange value in parallel with the client */ 108*18de8d7fSPeter Avalos dh_gen_key(dh, kex->we_need * 8); 109*18de8d7fSPeter Avalos 110*18de8d7fSPeter Avalos debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); 111*18de8d7fSPeter Avalos packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT); 112*18de8d7fSPeter Avalos 113*18de8d7fSPeter Avalos /* key, cert */ 114*18de8d7fSPeter Avalos if ((dh_client_pub = BN_new()) == NULL) 115*18de8d7fSPeter Avalos fatal("dh_client_pub == NULL"); 116*18de8d7fSPeter Avalos packet_get_bignum2(dh_client_pub); 117*18de8d7fSPeter Avalos packet_check_eom(); 118*18de8d7fSPeter Avalos 119*18de8d7fSPeter Avalos #ifdef DEBUG_KEXDH 120*18de8d7fSPeter Avalos fprintf(stderr, "dh_client_pub= "); 121*18de8d7fSPeter Avalos BN_print_fp(stderr, dh_client_pub); 122*18de8d7fSPeter Avalos fprintf(stderr, "\n"); 123*18de8d7fSPeter Avalos debug("bits %d", BN_num_bits(dh_client_pub)); 124*18de8d7fSPeter Avalos #endif 125*18de8d7fSPeter Avalos 126*18de8d7fSPeter Avalos #ifdef DEBUG_KEXDH 127*18de8d7fSPeter Avalos DHparams_print_fp(stderr, dh); 128*18de8d7fSPeter Avalos fprintf(stderr, "pub= "); 129*18de8d7fSPeter Avalos BN_print_fp(stderr, dh->pub_key); 130*18de8d7fSPeter Avalos fprintf(stderr, "\n"); 131*18de8d7fSPeter Avalos #endif 132*18de8d7fSPeter Avalos if (!dh_pub_is_valid(dh, dh_client_pub)) 133*18de8d7fSPeter Avalos packet_disconnect("bad client public DH value"); 134*18de8d7fSPeter Avalos 135*18de8d7fSPeter Avalos klen = DH_size(dh); 136*18de8d7fSPeter Avalos kbuf = xmalloc(klen); 137*18de8d7fSPeter Avalos if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) 138*18de8d7fSPeter Avalos fatal("DH_compute_key: failed"); 139*18de8d7fSPeter Avalos #ifdef DEBUG_KEXDH 140*18de8d7fSPeter Avalos dump_digest("shared secret", kbuf, kout); 141*18de8d7fSPeter Avalos #endif 142*18de8d7fSPeter Avalos if ((shared_secret = BN_new()) == NULL) 143*18de8d7fSPeter Avalos fatal("kexgex_server: BN_new failed"); 144*18de8d7fSPeter Avalos if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 145*18de8d7fSPeter Avalos fatal("kexgex_server: BN_bin2bn failed"); 146*18de8d7fSPeter Avalos memset(kbuf, 0, klen); 147*18de8d7fSPeter Avalos xfree(kbuf); 148*18de8d7fSPeter Avalos 149*18de8d7fSPeter Avalos key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); 150*18de8d7fSPeter Avalos 151*18de8d7fSPeter Avalos if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD) 152*18de8d7fSPeter Avalos min = max = -1; 153*18de8d7fSPeter Avalos 154*18de8d7fSPeter Avalos /* calc H */ 155*18de8d7fSPeter Avalos kexgex_hash( 156*18de8d7fSPeter Avalos kex->evp_md, 157*18de8d7fSPeter Avalos kex->client_version_string, 158*18de8d7fSPeter Avalos kex->server_version_string, 159*18de8d7fSPeter Avalos buffer_ptr(&kex->peer), buffer_len(&kex->peer), 160*18de8d7fSPeter Avalos buffer_ptr(&kex->my), buffer_len(&kex->my), 161*18de8d7fSPeter Avalos server_host_key_blob, sbloblen, 162*18de8d7fSPeter Avalos min, nbits, max, 163*18de8d7fSPeter Avalos dh->p, dh->g, 164*18de8d7fSPeter Avalos dh_client_pub, 165*18de8d7fSPeter Avalos dh->pub_key, 166*18de8d7fSPeter Avalos shared_secret, 167*18de8d7fSPeter Avalos &hash, &hashlen 168*18de8d7fSPeter Avalos ); 169*18de8d7fSPeter Avalos BN_clear_free(dh_client_pub); 170*18de8d7fSPeter Avalos 171*18de8d7fSPeter Avalos /* save session id := H */ 172*18de8d7fSPeter Avalos if (kex->session_id == NULL) { 173*18de8d7fSPeter Avalos kex->session_id_len = hashlen; 174*18de8d7fSPeter Avalos kex->session_id = xmalloc(kex->session_id_len); 175*18de8d7fSPeter Avalos memcpy(kex->session_id, hash, kex->session_id_len); 176*18de8d7fSPeter Avalos } 177*18de8d7fSPeter Avalos 178*18de8d7fSPeter Avalos /* sign H */ 179*18de8d7fSPeter Avalos PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen)); 180*18de8d7fSPeter Avalos 181*18de8d7fSPeter Avalos /* destroy_sensitive_data(); */ 182*18de8d7fSPeter Avalos 183*18de8d7fSPeter Avalos /* send server hostkey, DH pubkey 'f' and singed H */ 184*18de8d7fSPeter Avalos debug("SSH2_MSG_KEX_DH_GEX_REPLY sent"); 185*18de8d7fSPeter Avalos packet_start(SSH2_MSG_KEX_DH_GEX_REPLY); 186*18de8d7fSPeter Avalos packet_put_string(server_host_key_blob, sbloblen); 187*18de8d7fSPeter Avalos packet_put_bignum2(dh->pub_key); /* f */ 188*18de8d7fSPeter Avalos packet_put_string(signature, slen); 189*18de8d7fSPeter Avalos packet_send(); 190*18de8d7fSPeter Avalos 191*18de8d7fSPeter Avalos xfree(signature); 192*18de8d7fSPeter Avalos xfree(server_host_key_blob); 193*18de8d7fSPeter Avalos /* have keys, free DH */ 194*18de8d7fSPeter Avalos DH_free(dh); 195*18de8d7fSPeter Avalos 196*18de8d7fSPeter Avalos kex_derive_keys(kex, hash, hashlen, shared_secret); 197*18de8d7fSPeter Avalos BN_clear_free(shared_secret); 198*18de8d7fSPeter Avalos 199*18de8d7fSPeter Avalos kex_finish(kex); 200*18de8d7fSPeter Avalos } 201