| /* $OpenBSD: kexgexs.c,v 1.17 2014/01/09 23:20:00 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 "includes.h" |
| |
| #include <sys/param.h> |
| |
| #include <stdarg.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <signal.h> |
| |
| #include <openssl/dh.h> |
| |
| #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"); |
| memset(kbuf, 0, 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(kex, hash, hashlen, shared_secret); |
| BN_clear_free(shared_secret); |
| |
| kex_finish(kex); |
| } |