| /* $OpenBSD: kexgexc.c,v 1.8 2006/08/01 23:22:47 stevesk 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 <stdio.h> |
| #include <string.h> |
| |
| #include "xmalloc.h" |
| #include "key.h" |
| #include "kex.h" |
| #include "log.h" |
| #include "packet.h" |
| #include "dh.h" |
| #include "ssh2.h" |
| #include "compat.h" |
| |
| void |
| kexgex_client(Kex *kex) |
| { |
| BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; |
| BIGNUM *p = NULL, *g = NULL; |
| Key *server_host_key; |
| u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; |
| u_int klen, kout, slen, sbloblen, hashlen; |
| int min, max, nbits; |
| DH *dh; |
| |
| nbits = dh_estimate(kex->we_need * 8); |
| |
| if (datafellows & SSH_OLD_DHGEX) { |
| /* Old GEX request */ |
| packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD); |
| packet_put_int(nbits); |
| min = DH_GRP_MIN; |
| max = DH_GRP_MAX; |
| |
| debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits); |
| } else { |
| /* New GEX request */ |
| min = DH_GRP_MIN; |
| max = DH_GRP_MAX; |
| packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); |
| packet_put_int(min); |
| packet_put_int(nbits); |
| packet_put_int(max); |
| |
| debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", |
| min, nbits, max); |
| } |
| #ifdef DEBUG_KEXDH |
| fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", |
| min, nbits, max); |
| #endif |
| packet_send(); |
| |
| debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP"); |
| packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP); |
| |
| if ((p = BN_new()) == NULL) |
| fatal("BN_new"); |
| packet_get_bignum2(p); |
| if ((g = BN_new()) == NULL) |
| fatal("BN_new"); |
| packet_get_bignum2(g); |
| packet_check_eom(); |
| |
| if (BN_num_bits(p) < min || BN_num_bits(p) > max) |
| fatal("DH_GEX group out of range: %d !< %d !< %d", |
| min, BN_num_bits(p), max); |
| |
| dh = dh_new_group(g, p); |
| dh_gen_key(dh, kex->we_need * 8); |
| |
| #ifdef DEBUG_KEXDH |
| DHparams_print_fp(stderr, dh); |
| fprintf(stderr, "pub= "); |
| BN_print_fp(stderr, dh->pub_key); |
| fprintf(stderr, "\n"); |
| #endif |
| |
| debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); |
| /* generate and send 'e', client DH public key */ |
| packet_start(SSH2_MSG_KEX_DH_GEX_INIT); |
| packet_put_bignum2(dh->pub_key); |
| packet_send(); |
| |
| debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY"); |
| packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY); |
| |
| /* key, cert */ |
| server_host_key_blob = packet_get_string(&sbloblen); |
| server_host_key = key_from_blob(server_host_key_blob, sbloblen); |
| if (server_host_key == NULL) |
| fatal("cannot decode server_host_key_blob"); |
| if (server_host_key->type != kex->hostkey_type) |
| fatal("type mismatch for decoded server_host_key_blob"); |
| if (kex->verify_host_key == NULL) |
| fatal("cannot verify server_host_key"); |
| if (kex->verify_host_key(server_host_key) == -1) |
| fatal("server_host_key verification failed"); |
| |
| /* DH parameter f, server public DH key */ |
| if ((dh_server_pub = BN_new()) == NULL) |
| fatal("dh_server_pub == NULL"); |
| packet_get_bignum2(dh_server_pub); |
| |
| #ifdef DEBUG_KEXDH |
| fprintf(stderr, "dh_server_pub= "); |
| BN_print_fp(stderr, dh_server_pub); |
| fprintf(stderr, "\n"); |
| debug("bits %d", BN_num_bits(dh_server_pub)); |
| #endif |
| |
| /* signed H */ |
| signature = packet_get_string(&slen); |
| packet_check_eom(); |
| |
| if (!dh_pub_is_valid(dh, dh_server_pub)) |
| packet_disconnect("bad server public DH value"); |
| |
| klen = DH_size(dh); |
| kbuf = xmalloc(klen); |
| kout = DH_compute_key(kbuf, dh_server_pub, dh); |
| #ifdef DEBUG_KEXDH |
| dump_digest("shared secret", kbuf, kout); |
| #endif |
| if ((shared_secret = BN_new()) == NULL) |
| fatal("kexgex_client: BN_new failed"); |
| BN_bin2bn(kbuf, kout, shared_secret); |
| memset(kbuf, 0, klen); |
| xfree(kbuf); |
| |
| if (datafellows & SSH_OLD_DHGEX) |
| min = max = -1; |
| |
| /* calc and verify H */ |
| kexgex_hash( |
| kex->evp_md, |
| kex->client_version_string, |
| kex->server_version_string, |
| buffer_ptr(&kex->my), buffer_len(&kex->my), |
| buffer_ptr(&kex->peer), buffer_len(&kex->peer), |
| server_host_key_blob, sbloblen, |
| min, nbits, max, |
| dh->p, dh->g, |
| dh->pub_key, |
| dh_server_pub, |
| shared_secret, |
| &hash, &hashlen |
| ); |
| |
| /* have keys, free DH */ |
| DH_free(dh); |
| xfree(server_host_key_blob); |
| BN_clear_free(dh_server_pub); |
| |
| if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) |
| fatal("key_verify failed for server_host_key"); |
| key_free(server_host_key); |
| xfree(signature); |
| |
| /* save session id */ |
| 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); |
| } |
| kex_derive_keys(kex, hash, hashlen, shared_secret); |
| BN_clear_free(shared_secret); |
| |
| kex_finish(kex); |
| } |