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240 lines
6.1 KiB
240 lines
6.1 KiB
/* $OpenBSD: kexecdh.c,v 1.10 2019/01/21 10:40:11 djm Exp $ */
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/*
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* Copyright (c) 2010 Damien Miller. All rights reserved.
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* Copyright (c) 2019 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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#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
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#include <sys/types.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/ecdh.h>
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#include "sshkey.h"
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#include "kex.h"
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#include "sshbuf.h"
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#include "digest.h"
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#include "ssherr.h"
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static int
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kex_ecdh_dec_key_group(struct kex *, const struct sshbuf *, EC_KEY *key,
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const EC_GROUP *, struct sshbuf **);
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int
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kex_ecdh_keypair(struct kex *kex)
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{
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EC_KEY *client_key = NULL;
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const EC_GROUP *group;
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const EC_POINT *public_key;
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struct sshbuf *buf = NULL;
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int r;
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if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == 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 (EC_KEY_generate_key(client_key) != 1) {
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r = SSH_ERR_LIBCRYPTO_ERROR;
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goto out;
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}
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group = EC_KEY_get0_group(client_key);
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public_key = EC_KEY_get0_public_key(client_key);
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if ((buf = 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_ec(buf, public_key, group)) != 0 ||
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(r = sshbuf_get_u32(buf, NULL)) != 0)
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goto out;
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#ifdef DEBUG_KEXECDH
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fputs("client private key:\n", stderr);
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sshkey_dump_ec_key(client_key);
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#endif
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kex->ec_client_key = client_key;
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kex->ec_group = group;
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client_key = NULL; /* owned by the kex */
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kex->client_pub = buf;
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buf = NULL;
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out:
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EC_KEY_free(client_key);
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sshbuf_free(buf);
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return r;
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}
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int
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kex_ecdh_enc(struct kex *kex, const struct sshbuf *client_blob,
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struct sshbuf **server_blobp, struct sshbuf **shared_secretp)
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{
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const EC_GROUP *group;
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const EC_POINT *pub_key;
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EC_KEY *server_key = NULL;
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struct sshbuf *server_blob = NULL;
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int r;
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*server_blobp = NULL;
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*shared_secretp = NULL;
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if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == 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 (EC_KEY_generate_key(server_key) != 1) {
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r = SSH_ERR_LIBCRYPTO_ERROR;
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goto out;
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}
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group = EC_KEY_get0_group(server_key);
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#ifdef DEBUG_KEXECDH
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fputs("server private key:\n", stderr);
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sshkey_dump_ec_key(server_key);
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#endif
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pub_key = EC_KEY_get0_public_key(server_key);
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if ((server_blob = 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_ec(server_blob, pub_key, group)) != 0 ||
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(r = sshbuf_get_u32(server_blob, NULL)) != 0)
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goto out;
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if ((r = kex_ecdh_dec_key_group(kex, client_blob, server_key, group,
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shared_secretp)) != 0)
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goto out;
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*server_blobp = server_blob;
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server_blob = NULL;
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out:
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EC_KEY_free(server_key);
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sshbuf_free(server_blob);
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return r;
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}
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static int
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kex_ecdh_dec_key_group(struct kex *kex, const struct sshbuf *ec_blob,
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EC_KEY *key, const EC_GROUP *group, struct sshbuf **shared_secretp)
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{
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struct sshbuf *buf = NULL;
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BIGNUM *shared_secret = NULL;
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EC_POINT *dh_pub = NULL;
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u_char *kbuf = NULL;
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size_t klen = 0;
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int r;
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*shared_secretp = NULL;
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if ((buf = 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_stringb(buf, ec_blob)) != 0)
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goto out;
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if ((dh_pub = EC_POINT_new(group)) == 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_get_ec(buf, dh_pub, group)) != 0) {
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goto out;
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}
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sshbuf_reset(buf);
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#ifdef DEBUG_KEXECDH
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fputs("public key:\n", stderr);
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sshkey_dump_ec_point(group, dh_pub);
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#endif
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if (sshkey_ec_validate_public(group, dh_pub) != 0) {
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r = SSH_ERR_MESSAGE_INCOMPLETE;
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goto out;
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}
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klen = (EC_GROUP_get_degree(group) + 7) / 8;
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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 (ECDH_compute_key(kbuf, klen, dh_pub, key, NULL) != (int)klen ||
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BN_bin2bn(kbuf, klen, 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_KEXECDH
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dump_digest("shared secret", kbuf, klen);
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#endif
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if ((r = sshbuf_put_bignum2(buf, shared_secret)) != 0)
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goto out;
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*shared_secretp = buf;
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buf = NULL;
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out:
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EC_POINT_clear_free(dh_pub);
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BN_clear_free(shared_secret);
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freezero(kbuf, klen);
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sshbuf_free(buf);
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return r;
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}
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int
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kex_ecdh_dec(struct kex *kex, const struct sshbuf *server_blob,
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struct sshbuf **shared_secretp)
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{
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int r;
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r = kex_ecdh_dec_key_group(kex, server_blob, kex->ec_client_key,
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kex->ec_group, shared_secretp);
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EC_KEY_free(kex->ec_client_key);
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kex->ec_client_key = NULL;
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return r;
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}
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#else
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#include "ssherr.h"
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struct kex;
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struct sshbuf;
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struct sshkey;
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int
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kex_ecdh_keypair(struct kex *kex)
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{
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return SSH_ERR_SIGN_ALG_UNSUPPORTED;
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}
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int
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kex_ecdh_enc(struct kex *kex, const struct sshbuf *client_blob,
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struct sshbuf **server_blobp, struct sshbuf **shared_secretp)
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{
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return SSH_ERR_SIGN_ALG_UNSUPPORTED;
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}
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int
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kex_ecdh_dec(struct kex *kex, const struct sshbuf *server_blob,
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struct sshbuf **shared_secretp)
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{
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return SSH_ERR_SIGN_ALG_UNSUPPORTED;
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}
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#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
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