| /* $OpenBSD: kexecdhs.c,v 1.21 2019/01/21 10:05:09 djm 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 "includes.h" |
| |
| #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) |
| |
| #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 ((r = kex_load_hostkey(ssh, &server_host_private, |
| &server_host_public)) != 0) |
| 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, |
| kex->server_version, |
| 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; |
| |
| /* sign H */ |
| if ((r = kex->sign(ssh, server_host_private, server_host_public, |
| &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 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; |
| } |
| #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ |
| |