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/* $OpenBSD: kexgexs.c,v 1.31 2017/05/30 14:23:52 markus Exp $ */ |
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/* |
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* Copyright (c) 2000 Niels Provos. All rights reserved. |
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* Copyright (c) 2001 Markus Friedl. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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*/ |
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#include <stdio.h> |
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#include <string.h> |
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#include <signal.h> |
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#include <openssl/dh.h> |
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#include "sshkey.h" |
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#include "cipher.h" |
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#include "digest.h" |
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#include "kex.h" |
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#include "log.h" |
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#include "packet.h" |
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#include "dh.h" |
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#include "ssh2.h" |
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#include "compat.h" |
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#ifdef GSSAPI |
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#include "ssh-gss.h" |
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#endif |
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#include "monitor_wrap.h" |
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#include "dispatch.h" |
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#include "ssherr.h" |
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#include "sshbuf.h" |
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#include "misc.h" |
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static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *); |
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static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *); |
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int |
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kexgex_server(struct ssh *ssh) |
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{ |
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, |
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&input_kex_dh_gex_request); |
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debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST"); |
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return 0; |
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} |
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static int |
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input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh) |
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{ |
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struct kex *kex = ssh->kex; |
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int r; |
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u_int min = 0, max = 0, nbits = 0; |
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debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); |
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if ((r = sshpkt_get_u32(ssh, &min)) != 0 || |
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(r = sshpkt_get_u32(ssh, &nbits)) != 0 || |
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(r = sshpkt_get_u32(ssh, &max)) != 0 || |
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(r = sshpkt_get_end(ssh)) != 0) |
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goto out; |
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kex->nbits = nbits; |
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kex->min = min; |
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kex->max = max; |
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min = MAXIMUM(DH_GRP_MIN, min); |
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max = MINIMUM(DH_GRP_MAX, max); |
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nbits = MAXIMUM(DH_GRP_MIN, nbits); |
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nbits = MINIMUM(DH_GRP_MAX, nbits); |
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if (kex->max < kex->min || kex->nbits < kex->min || |
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kex->max < kex->nbits || kex->max < DH_GRP_MIN) { |
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r = SSH_ERR_DH_GEX_OUT_OF_RANGE; |
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goto out; |
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} |
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/* Contact privileged parent */ |
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kex->dh = PRIVSEP(choose_dh(min, nbits, max)); |
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if (kex->dh == NULL) { |
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sshpkt_disconnect(ssh, "no matching DH grp found"); |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); |
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 || |
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(r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 || |
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(r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 || |
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(r = sshpkt_send(ssh)) != 0) |
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goto out; |
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/* Compute our exchange value in parallel with the client */ |
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if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) |
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goto out; |
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debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); |
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init); |
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r = 0; |
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out: |
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return r; |
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} |
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static int |
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input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh) |
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{ |
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struct kex *kex = ssh->kex; |
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BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; |
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struct sshkey *server_host_public, *server_host_private; |
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u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; |
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u_char hash[SSH_DIGEST_MAX_LENGTH]; |
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size_t sbloblen, slen; |
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size_t klen = 0, hashlen; |
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int kout, r; |
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if (kex->load_host_public_key == NULL || |
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kex->load_host_private_key == NULL) { |
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r = SSH_ERR_INVALID_ARGUMENT; |
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goto out; |
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} |
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server_host_public = kex->load_host_public_key(kex->hostkey_type, |
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kex->hostkey_nid, ssh); |
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server_host_private = kex->load_host_private_key(kex->hostkey_type, |
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kex->hostkey_nid, ssh); |
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if (server_host_public == NULL) { |
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r = SSH_ERR_NO_HOSTKEY_LOADED; |
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goto out; |
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} |
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/* key, cert */ |
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if ((dh_client_pub = BN_new()) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || |
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(r = sshpkt_get_end(ssh)) != 0) |
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goto out; |
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#ifdef DEBUG_KEXDH |
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fprintf(stderr, "dh_client_pub= "); |
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BN_print_fp(stderr, dh_client_pub); |
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fprintf(stderr, "\n"); |
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debug("bits %d", BN_num_bits(dh_client_pub)); |
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#endif |
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#ifdef DEBUG_KEXDH |
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DHparams_print_fp(stderr, kex->dh); |
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fprintf(stderr, "pub= "); |
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BN_print_fp(stderr, kex->dh->pub_key); |
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fprintf(stderr, "\n"); |
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#endif |
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if (!dh_pub_is_valid(kex->dh, dh_client_pub)) { |
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sshpkt_disconnect(ssh, "bad client public DH value"); |
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r = SSH_ERR_MESSAGE_INCOMPLETE; |
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goto out; |
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} |
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klen = DH_size(kex->dh); |
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if ((kbuf = malloc(klen)) == NULL || |
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(shared_secret = BN_new()) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 || |
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BN_bin2bn(kbuf, kout, shared_secret) == NULL) { |
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r = SSH_ERR_LIBCRYPTO_ERROR; |
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goto out; |
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} |
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#ifdef DEBUG_KEXDH |
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dump_digest("shared secret", kbuf, kout); |
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#endif |
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if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, |
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&sbloblen)) != 0) |
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goto out; |
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/* calc H */ |
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hashlen = sizeof(hash); |
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if ((r = kexgex_hash( |
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kex->hash_alg, |
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kex->client_version_string, |
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kex->server_version_string, |
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sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), |
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sshbuf_ptr(kex->my), sshbuf_len(kex->my), |
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server_host_key_blob, sbloblen, |
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kex->min, kex->nbits, kex->max, |
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kex->dh->p, kex->dh->g, |
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dh_client_pub, |
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kex->dh->pub_key, |
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shared_secret, |
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hash, &hashlen)) != 0) |
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goto out; |
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/* save session id := H */ |
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if (kex->session_id == NULL) { |
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kex->session_id_len = hashlen; |
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kex->session_id = malloc(kex->session_id_len); |
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if (kex->session_id == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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memcpy(kex->session_id, hash, kex->session_id_len); |
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} |
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/* sign H */ |
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if ((r = kex->sign(server_host_private, server_host_public, &signature, |
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&slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0) |
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goto out; |
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/* destroy_sensitive_data(); */ |
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/* send server hostkey, DH pubkey 'f' and singed H */ |
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 || |
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(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || |
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(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */ |
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(r = sshpkt_put_string(ssh, signature, slen)) != 0 || |
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(r = sshpkt_send(ssh)) != 0) |
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goto out; |
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if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) |
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r = kex_send_newkeys(ssh); |
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out: |
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DH_free(kex->dh); |
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kex->dh = NULL; |
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if (dh_client_pub) |
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BN_clear_free(dh_client_pub); |
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if (kbuf) { |
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explicit_bzero(kbuf, klen); |
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free(kbuf); |
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} |
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if (shared_secret) |
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BN_clear_free(shared_secret); |
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free(server_host_key_blob); |
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free(signature); |
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return r; |
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} |