diff options
Diffstat (limited to 'kexgexs.c')
| -rw-r--r-- | kexgexs.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/kexgexs.c b/kexgexs.c new file mode 100644 index 0000000..72b444f --- /dev/null +++ b/kexgexs.c @@ -0,0 +1,217 @@ +/* $OpenBSD: kexgexs.c,v 1.44 2021/12/19 22:08:06 djm 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" + +#ifdef WITH_OPENSSL + + +#include <stdarg.h> +#include <stdio.h> +#include <string.h> +#include <signal.h> + +#include <openssl/dh.h> + +#include "openbsd-compat/openssl-compat.h" + +#include "sshkey.h" +#include "cipher.h" +#include "digest.h" +#include "kex.h" +#include "log.h" +#include "packet.h" +#include "dh.h" +#include "ssh2.h" +#include "compat.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "dispatch.h" +#include "ssherr.h" +#include "sshbuf.h" +#include "misc.h" + +static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *); +static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *); + +int +kexgex_server(struct ssh *ssh) +{ + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, + &input_kex_dh_gex_request); + debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST"); + return 0; +} + +static int +input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + int r; + u_int min = 0, max = 0, nbits = 0; + const BIGNUM *dh_p, *dh_g; + + debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, &kex_protocol_error); + + if ((r = sshpkt_get_u32(ssh, &min)) != 0 || + (r = sshpkt_get_u32(ssh, &nbits)) != 0 || + (r = sshpkt_get_u32(ssh, &max)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + goto out; + kex->nbits = nbits; + kex->min = min; + kex->max = max; + min = MAXIMUM(DH_GRP_MIN, min); + max = MINIMUM(DH_GRP_MAX, max); + nbits = MAXIMUM(DH_GRP_MIN, nbits); + nbits = MINIMUM(DH_GRP_MAX, nbits); + + if (kex->max < kex->min || kex->nbits < kex->min || + kex->max < kex->nbits || kex->max < DH_GRP_MIN) { + r = SSH_ERR_DH_GEX_OUT_OF_RANGE; + goto out; + } + + /* Contact privileged parent */ + kex->dh = PRIVSEP(choose_dh(min, nbits, max)); + if (kex->dh == NULL) { + sshpkt_disconnect(ssh, "no matching DH grp found"); + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); + DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g); + if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 || + (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 || + (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 || + (r = sshpkt_send(ssh)) != 0) + goto out; + + /* Compute our exchange value in parallel with the client */ + if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) + goto out; + + debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init); + r = 0; + out: + return r; +} + +static int +input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + BIGNUM *dh_client_pub = NULL; + const BIGNUM *pub_key, *dh_p, *dh_g; + struct sshbuf *shared_secret = NULL; + struct sshbuf *server_host_key_blob = NULL; + struct sshkey *server_host_public, *server_host_private; + u_char *signature = NULL; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t slen, hashlen; + int r; + + debug("SSH2_MSG_KEX_DH_GEX_INIT received"); + ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &kex_protocol_error); + + if ((r = kex_load_hostkey(ssh, &server_host_private, + &server_host_public)) != 0) + goto out; + + /* key, cert */ + if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + goto out; + if ((shared_secret = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0) + goto out; + if ((server_host_key_blob = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0) + goto out; + + /* calc H */ + DH_get0_key(kex->dh, &pub_key, NULL); + DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g); + hashlen = sizeof(hash); + if ((r = kexgex_hash( + kex->hash_alg, + kex->client_version, + kex->server_version, + kex->peer, + kex->my, + server_host_key_blob, + kex->min, kex->nbits, kex->max, + dh_p, dh_g, + dh_client_pub, + pub_key, + sshbuf_ptr(shared_secret), sshbuf_len(shared_secret), + hash, &hashlen)) != 0) + goto out; + + /* sign H */ + if ((r = kex->sign(ssh, server_host_private, server_host_public, + &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0) + goto out; + + /* send server hostkey, DH pubkey 'f' and signed H */ + if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 || + (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 || + (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */ + (r = sshpkt_put_string(ssh, signature, slen)) != 0 || + (r = sshpkt_send(ssh)) != 0) + goto out; + + if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 || + (r = kex_send_newkeys(ssh)) != 0) + goto out; + + /* retain copy of hostkey used at initial KEX */ + if (kex->initial_hostkey == NULL && + (r = sshkey_from_private(server_host_public, + &kex->initial_hostkey)) != 0) + goto out; + /* success */ + out: + explicit_bzero(hash, sizeof(hash)); + DH_free(kex->dh); + kex->dh = NULL; + BN_clear_free(dh_client_pub); + sshbuf_free(shared_secret); + sshbuf_free(server_host_key_blob); + free(signature); + return r; +} +#endif /* WITH_OPENSSL */ |