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-rw-r--r--kexc25519c.c169
1 files changed, 169 insertions, 0 deletions
diff --git a/kexc25519c.c b/kexc25519c.c
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+/* $OpenBSD: kexc25519c.c,v 1.9 2017/12/18 02:25:15 djm Exp $ */
+/*
+ * Copyright (c) 2001 Markus Friedl. All rights reserved.
+ * Copyright (c) 2010 Damien Miller. All rights reserved.
+ * Copyright (c) 2013 Aris Adamantiadis. 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"
+
+#include <sys/types.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+#include "sshkey.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "ssh2.h"
+#include "sshbuf.h"
+#include "digest.h"
+#include "ssherr.h"
+
+static int
+input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh);
+
+int
+kexc25519_client(struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ int r;
+
+ kexc25519_keygen(kex->c25519_client_key, kex->c25519_client_pubkey);
+#ifdef DEBUG_KEXECDH
+ dump_digest("client private key:", kex->c25519_client_key,
+ sizeof(kex->c25519_client_key));
+#endif
+ if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
+ (r = sshpkt_put_string(ssh, kex->c25519_client_pubkey,
+ sizeof(kex->c25519_client_pubkey))) != 0 ||
+ (r = sshpkt_send(ssh)) != 0)
+ return r;
+
+ debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_c25519_reply);
+ return 0;
+}
+
+static int
+input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh)
+{
+ struct kex *kex = ssh->kex;
+ struct sshkey *server_host_key = NULL;
+ struct sshbuf *shared_secret = NULL;
+ u_char *server_pubkey = NULL;
+ u_char *server_host_key_blob = NULL, *signature = NULL;
+ u_char hash[SSH_DIGEST_MAX_LENGTH];
+ size_t slen, pklen, sbloblen, hashlen;
+ int r;
+
+ if (kex->verify_host_key == NULL) {
+ r = SSH_ERR_INVALID_ARGUMENT;
+ goto out;
+ }
+
+ /* hostkey */
+ if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+ &sbloblen)) != 0 ||
+ (r = sshkey_from_blob(server_host_key_blob, sbloblen,
+ &server_host_key)) != 0)
+ goto out;
+ if (server_host_key->type != kex->hostkey_type ||
+ (kex->hostkey_type == KEY_ECDSA &&
+ server_host_key->ecdsa_nid != kex->hostkey_nid)) {
+ r = SSH_ERR_KEY_TYPE_MISMATCH;
+ goto out;
+ }
+ if (kex->verify_host_key(server_host_key, ssh) == -1) {
+ r = SSH_ERR_SIGNATURE_INVALID;
+ goto out;
+ }
+
+ /* Q_S, server public key */
+ /* signed H */
+ if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
+ (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+ (r = sshpkt_get_end(ssh)) != 0)
+ goto out;
+ if (pklen != CURVE25519_SIZE) {
+ r = SSH_ERR_SIGNATURE_INVALID;
+ goto out;
+ }
+
+#ifdef DEBUG_KEXECDH
+ dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
+#endif
+
+ if ((shared_secret = sshbuf_new()) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
+ shared_secret)) < 0)
+ goto out;
+
+ /* calc and verify H */
+ hashlen = sizeof(hash);
+ if ((r = kex_c25519_hash(
+ kex->hash_alg,
+ kex->client_version_string,
+ kex->server_version_string,
+ sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+ sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+ server_host_key_blob, sbloblen,
+ kex->c25519_client_pubkey,
+ server_pubkey,
+ sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
+ hash, &hashlen)) < 0)
+ goto out;
+
+ if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
+ kex->hostkey_alg, ssh->compat)) != 0)
+ goto out;
+
+ /* save session id */
+ 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);
+ }
+
+ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+ r = kex_send_newkeys(ssh);
+out:
+ explicit_bzero(hash, sizeof(hash));
+ explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
+ free(server_host_key_blob);
+ free(server_pubkey);
+ free(signature);
+ sshkey_free(server_host_key);
+ sshbuf_free(shared_secret);
+ return r;
+}