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-rw-r--r--kexecdhs.c203
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diff --git a/kexecdhs.c b/kexecdhs.c
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+/* $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 "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 (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;
+}
+#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
+