251 lines
7.2 KiB
C
251 lines
7.2 KiB
C
/* $OpenBSD: kexgexs.c,v 1.32 2018/02/07 02:06:51 jsing 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 "includes.h"
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#ifdef WITH_OPENSSL
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#include <stdarg.h>
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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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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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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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}
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#endif /* WITH_OPENSSL */
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