/* $OpenBSD: kexgexs.c,v 1.19 2014/02/02 03:44:31 djm Exp $ */ /* * Copyright (c) 2000 Niels Provos. All rights reserved. * Copyright (c) 2001 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include #include "xmalloc.h" #include "buffer.h" #include "key.h" #include "cipher.h" #include "kex.h" #include "log.h" #include "packet.h" #include "dh.h" #include "ssh2.h" #include "compat.h" #ifdef GSSAPI #include "ssh-gss.h" #endif #include "monitor_wrap.h" void kexgex_server(Kex *kex) { BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; Key *server_host_public, *server_host_private; DH *dh; u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; u_int sbloblen, klen, slen, hashlen; int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1; int type, kout; if (kex->load_host_public_key == NULL || kex->load_host_private_key == NULL) fatal("Cannot load hostkey"); server_host_public = kex->load_host_public_key(kex->hostkey_type); if (server_host_public == NULL) fatal("Unsupported hostkey type %d", kex->hostkey_type); server_host_private = kex->load_host_private_key(kex->hostkey_type); type = packet_read(); switch (type) { case SSH2_MSG_KEX_DH_GEX_REQUEST: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); omin = min = packet_get_int(); onbits = nbits = packet_get_int(); omax = max = packet_get_int(); min = MAX(DH_GRP_MIN, min); max = MIN(DH_GRP_MAX, max); nbits = MAX(DH_GRP_MIN, nbits); nbits = MIN(DH_GRP_MAX, nbits); break; case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received"); onbits = nbits = packet_get_int(); /* unused for old GEX */ omin = min = DH_GRP_MIN; omax = max = DH_GRP_MAX; break; default: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type); } packet_check_eom(); if (omax < omin || onbits < omin || omax < onbits) fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d", omin, onbits, omax); /* Contact privileged parent */ dh = PRIVSEP(choose_dh(min, nbits, max)); if (dh == NULL) packet_disconnect("Protocol error: no matching DH grp found"); debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); packet_start(SSH2_MSG_KEX_DH_GEX_GROUP); packet_put_bignum2(dh->p); packet_put_bignum2(dh->g); packet_send(); /* flush */ packet_write_wait(); /* Compute our exchange value in parallel with the client */ dh_gen_key(dh, kex->we_need * 8); debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT); /* key, cert */ if ((dh_client_pub = BN_new()) == NULL) fatal("dh_client_pub == NULL"); packet_get_bignum2(dh_client_pub); packet_check_eom(); #ifdef DEBUG_KEXDH fprintf(stderr, "dh_client_pub= "); BN_print_fp(stderr, dh_client_pub); fprintf(stderr, "\n"); debug("bits %d", BN_num_bits(dh_client_pub)); #endif #ifdef DEBUG_KEXDH DHparams_print_fp(stderr, dh); fprintf(stderr, "pub= "); BN_print_fp(stderr, dh->pub_key); fprintf(stderr, "\n"); #endif if (!dh_pub_is_valid(dh, dh_client_pub)) packet_disconnect("bad client public DH value"); klen = DH_size(dh); kbuf = xmalloc(klen); if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) fatal("DH_compute_key: failed"); #ifdef DEBUG_KEXDH dump_digest("shared secret", kbuf, kout); #endif if ((shared_secret = BN_new()) == NULL) fatal("kexgex_server: BN_new failed"); if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) fatal("kexgex_server: BN_bin2bn failed"); explicit_bzero(kbuf, klen); free(kbuf); key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD) omin = min = omax = max = -1; /* calc H */ kexgex_hash( kex->hash_alg, kex->client_version_string, kex->server_version_string, buffer_ptr(&kex->peer), buffer_len(&kex->peer), buffer_ptr(&kex->my), buffer_len(&kex->my), server_host_key_blob, sbloblen, omin, onbits, omax, dh->p, dh->g, dh_client_pub, dh->pub_key, shared_secret, &hash, &hashlen ); BN_clear_free(dh_client_pub); /* save session id := H */ if (kex->session_id == NULL) { kex->session_id_len = hashlen; kex->session_id = xmalloc(kex->session_id_len); memcpy(kex->session_id, hash, kex->session_id_len); } /* sign H */ kex->sign(server_host_private, server_host_public, &signature, &slen, hash, hashlen); /* destroy_sensitive_data(); */ /* send server hostkey, DH pubkey 'f' and singed H */ debug("SSH2_MSG_KEX_DH_GEX_REPLY sent"); packet_start(SSH2_MSG_KEX_DH_GEX_REPLY); packet_put_string(server_host_key_blob, sbloblen); packet_put_bignum2(dh->pub_key); /* f */ packet_put_string(signature, slen); packet_send(); free(signature); free(server_host_key_blob); /* have keys, free DH */ DH_free(dh); kex_derive_keys_bn(kex, hash, hashlen, shared_secret); BN_clear_free(shared_secret); kex_finish(kex); }