271dcc6a42
This completely removes client-side support for the SSH 1 protocol, which was already disabled in 12 but is still enabled in 11. For that reason, we will not be able to merge 7.6p1 or newer back to 11.
253 lines
7.2 KiB
C
253 lines
7.2 KiB
C
/* $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 "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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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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}
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#endif /* WITH_OPENSSL */
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