Release notes are available at https://www.openssh.com/txt/release-8.9 Some highlights: * ssh(1), sshd(8), ssh-add(1), ssh-agent(1): add a system for restricting forwarding and use of keys added to ssh-agent(1) * ssh(1), sshd(8): add the sntrup761x25519-sha512@openssh.com hybrid ECDH/x25519 + Streamlined NTRU Prime post-quantum KEX to the default KEXAlgorithms list (after the ECDH methods but before the prime-group DH ones). The next release of OpenSSH is likely to make this key exchange the default method. * sshd(8), portable OpenSSH only: this release removes in-built support for MD5-hashed passwords. If you require these on your system then we recommend linking against libxcrypt or similar. Future deprecation notice ========================= A near-future release of OpenSSH will switch scp(1) from using the legacy scp/rcp protocol to using SFTP by default. Legacy scp/rcp performs wildcard expansion of remote filenames (e.g. "scp host:* .") through the remote shell. This has the side effect of requiring double quoting of shell meta-characters in file names included on scp(1) command-lines, otherwise they could be interpreted as shell commands on the remote side. MFC after: 1 month Relnotes: Yes Sponsored by: The FreeBSD Foundation
242 lines
7.0 KiB
C
242 lines
7.0 KiB
C
/* $OpenBSD: kexgexc.c,v 1.38 2021/12/19 22:08:06 djm 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 <sys/types.h>
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#include <openssl/dh.h>
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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 "openbsd-compat/openssl-compat.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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#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_group(int, u_int32_t, struct ssh *);
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static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *);
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int
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kexgex_client(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 nbits;
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nbits = dh_estimate(kex->dh_need * 8);
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kex->min = DH_GRP_MIN;
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kex->max = DH_GRP_MAX;
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kex->nbits = nbits;
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if (ssh->compat & SSH_BUG_DHGEX_LARGE)
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kex->nbits = MINIMUM(kex->nbits, 4096);
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/* New GEX request */
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
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(r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
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(r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
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(r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
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(r = sshpkt_send(ssh)) != 0)
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goto out;
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debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
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kex->min, kex->nbits, kex->max);
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
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kex->min, kex->nbits, kex->max);
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#endif
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debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
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&input_kex_dh_gex_group);
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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_group(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 *p = NULL, *g = NULL;
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const BIGNUM *pub_key;
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int r, bits;
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debug("SSH2_MSG_KEX_DH_GEX_GROUP received");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, &kex_protocol_error);
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if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 ||
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(r = sshpkt_get_bignum2(ssh, &g)) != 0 ||
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(r = sshpkt_get_end(ssh)) != 0)
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goto out;
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if ((bits = BN_num_bits(p)) < 0 ||
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(u_int)bits < kex->min || (u_int)bits > kex->max) {
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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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if ((kex->dh = dh_new_group(g, p)) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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p = g = NULL; /* belong to kex->dh now */
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/* generate and send 'e', client DH public key */
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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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DH_get0_key(kex->dh, &pub_key, NULL);
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
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(r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
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(r = sshpkt_send(ssh)) != 0)
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goto out;
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debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
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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, pub_key);
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fprintf(stderr, "\n");
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#endif
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debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
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r = 0;
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out:
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BN_clear_free(p);
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BN_clear_free(g);
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return r;
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}
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static int
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input_kex_dh_gex_reply(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 *dh_server_pub = NULL;
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const BIGNUM *pub_key, *dh_p, *dh_g;
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struct sshbuf *shared_secret = NULL;
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struct sshbuf *tmp = NULL, *server_host_key_blob = NULL;
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struct sshkey *server_host_key = NULL;
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u_char *signature = NULL;
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u_char hash[SSH_DIGEST_MAX_LENGTH];
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size_t slen, hashlen;
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int r;
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debug("SSH2_MSG_KEX_DH_GEX_REPLY received");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &kex_protocol_error);
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/* key, cert */
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if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
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goto out;
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/* sshkey_fromb() consumes its buffer, so make a copy */
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if ((tmp = sshbuf_fromb(server_host_key_blob)) == 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 = sshkey_fromb(tmp, &server_host_key)) != 0 ||
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(r = kex_verify_host_key(ssh, server_host_key)) != 0)
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goto out;
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/* DH parameter f, server public DH key, signed H */
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if ((r = sshpkt_get_bignum2(ssh, &dh_server_pub)) != 0 ||
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(r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
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(r = sshpkt_get_end(ssh)) != 0)
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goto out;
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if ((shared_secret = sshbuf_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 = kex_dh_compute_key(kex, dh_server_pub, shared_secret)) != 0)
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goto out;
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if (ssh->compat & SSH_OLD_DHGEX)
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kex->min = kex->max = -1;
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/* calc and verify H */
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DH_get0_key(kex->dh, &pub_key, NULL);
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DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
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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,
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kex->server_version,
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kex->my,
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kex->peer,
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server_host_key_blob,
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kex->min, kex->nbits, kex->max,
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dh_p, dh_g,
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pub_key,
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dh_server_pub,
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sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
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hash, &hashlen)) != 0)
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goto out;
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if ((r = sshkey_verify(server_host_key, signature, slen, hash,
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hashlen, kex->hostkey_alg, ssh->compat, NULL)) != 0)
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goto out;
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if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
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(r = kex_send_newkeys(ssh)) != 0)
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goto out;
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/* save initial signature and hostkey */
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if ((kex->flags & KEX_INITIAL) != 0) {
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if (kex->initial_hostkey != NULL || kex->initial_sig != NULL) {
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r = SSH_ERR_INTERNAL_ERROR;
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goto out;
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}
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if ((kex->initial_sig = sshbuf_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 = sshbuf_put(kex->initial_sig, signature, slen)) != 0)
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goto out;
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kex->initial_hostkey = server_host_key;
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server_host_key = NULL;
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}
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/* success */
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out:
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explicit_bzero(hash, sizeof(hash));
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DH_free(kex->dh);
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kex->dh = NULL;
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BN_clear_free(dh_server_pub);
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sshbuf_free(shared_secret);
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sshkey_free(server_host_key);
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sshbuf_free(tmp);
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sshbuf_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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