/* $OpenBSD: kexecdhs.c,v 1.17 2018/02/07 02:06:51 jsing Exp $ */ /* * Copyright (c) 2001 Markus Friedl. All rights reserved. * Copyright (c) 2010 Damien Miller. 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 <sys/types.h> #include <string.h> #include <signal.h> #include <openssl/ecdh.h> #include "sshkey.h" #include "cipher.h" #include "digest.h" #include "kex.h" #include "log.h" #include "packet.h" #include "ssh2.h" #include "dispatch.h" #include "compat.h" #include "ssherr.h" #include "sshbuf.h" static int input_kex_ecdh_init(int, u_int32_t, struct ssh *); int kexecdh_server(struct ssh *ssh) { debug("expecting SSH2_MSG_KEX_ECDH_INIT"); ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_ecdh_init); return 0; } static int input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh) { struct kex *kex = ssh->kex; EC_POINT *client_public; EC_KEY *server_key = NULL; const EC_GROUP *group; const EC_POINT *public_key; BIGNUM *shared_secret = NULL; struct sshkey *server_host_private, *server_host_public; u_char *server_host_key_blob = NULL, *signature = NULL; u_char *kbuf = NULL; u_char hash[SSH_DIGEST_MAX_LENGTH]; size_t slen, sbloblen; size_t klen = 0, hashlen; int r; if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if (EC_KEY_generate_key(server_key) != 1) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } group = EC_KEY_get0_group(server_key); #ifdef DEBUG_KEXECDH fputs("server private key:\n", stderr); sshkey_dump_ec_key(server_key); #endif if (kex->load_host_public_key == NULL || kex->load_host_private_key == NULL) { r = SSH_ERR_INVALID_ARGUMENT; goto out; } server_host_public = kex->load_host_public_key(kex->hostkey_type, kex->hostkey_nid, ssh); server_host_private = kex->load_host_private_key(kex->hostkey_type, kex->hostkey_nid, ssh); if (server_host_public == NULL) { r = SSH_ERR_NO_HOSTKEY_LOADED; goto out; } if ((client_public = EC_POINT_new(group)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 || (r = sshpkt_get_end(ssh)) != 0) goto out; #ifdef DEBUG_KEXECDH fputs("client public key:\n", stderr); sshkey_dump_ec_point(group, client_public); #endif if (sshkey_ec_validate_public(group, client_public) != 0) { sshpkt_disconnect(ssh, "invalid client public key"); r = SSH_ERR_MESSAGE_INCOMPLETE; goto out; } /* Calculate shared_secret */ klen = (EC_GROUP_get_degree(group) + 7) / 8; if ((kbuf = malloc(klen)) == NULL || (shared_secret = BN_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if (ECDH_compute_key(kbuf, klen, client_public, server_key, NULL) != (int)klen || BN_bin2bn(kbuf, klen, shared_secret) == NULL) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } #ifdef DEBUG_KEXECDH dump_digest("shared secret", kbuf, klen); #endif /* calc H */ if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, &sbloblen)) != 0) goto out; hashlen = sizeof(hash); if ((r = kex_ecdh_hash( kex->hash_alg, group, kex->client_version_string, kex->server_version_string, sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), sshbuf_ptr(kex->my), sshbuf_len(kex->my), server_host_key_blob, sbloblen, client_public, EC_KEY_get0_public_key(server_key), shared_secret, hash, &hashlen)) != 0) goto out; /* save session id := H */ if (kex->session_id == NULL) { kex->session_id_len = hashlen; kex->session_id = malloc(kex->session_id_len); if (kex->session_id == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } memcpy(kex->session_id, hash, kex->session_id_len); } /* sign H */ if ((r = kex->sign(server_host_private, server_host_public, &signature, &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0) goto out; /* destroy_sensitive_data(); */ public_key = EC_KEY_get0_public_key(server_key); /* send server hostkey, ECDH pubkey 'Q_S' and signed H */ if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 || (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || (r = sshpkt_put_ec(ssh, public_key, group)) != 0 || (r = sshpkt_put_string(ssh, signature, slen)) != 0 || (r = sshpkt_send(ssh)) != 0) goto out; if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) r = kex_send_newkeys(ssh); out: explicit_bzero(hash, sizeof(hash)); EC_KEY_free(kex->ec_client_key); kex->ec_client_key = NULL; EC_KEY_free(server_key); if (kbuf) { explicit_bzero(kbuf, klen); free(kbuf); } BN_clear_free(shared_secret); free(server_host_key_blob); free(signature); return r; }