1 /* $OpenBSD: kexecdhs.c,v 1.17 2018/02/07 02:06:51 jsing Exp $ */
3 * Copyright (c) 2001 Markus Friedl. All rights reserved.
4 * Copyright (c) 2010 Damien Miller. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 #if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
31 #include <sys/types.h>
35 #include <openssl/ecdh.h>
50 static int input_kex_ecdh_init(int, u_int32_t, struct ssh *);
53 kexecdh_server(struct ssh *ssh)
55 debug("expecting SSH2_MSG_KEX_ECDH_INIT");
56 ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_ecdh_init);
61 input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
63 struct kex *kex = ssh->kex;
64 EC_POINT *client_public;
65 EC_KEY *server_key = NULL;
66 const EC_GROUP *group;
67 const EC_POINT *public_key;
68 BIGNUM *shared_secret = NULL;
69 struct sshkey *server_host_private, *server_host_public;
70 u_char *server_host_key_blob = NULL, *signature = NULL;
72 u_char hash[SSH_DIGEST_MAX_LENGTH];
73 size_t slen, sbloblen;
74 size_t klen = 0, hashlen;
77 if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
78 r = SSH_ERR_ALLOC_FAIL;
81 if (EC_KEY_generate_key(server_key) != 1) {
82 r = SSH_ERR_LIBCRYPTO_ERROR;
85 group = EC_KEY_get0_group(server_key);
88 fputs("server private key:\n", stderr);
89 sshkey_dump_ec_key(server_key);
92 if (kex->load_host_public_key == NULL ||
93 kex->load_host_private_key == NULL) {
94 r = SSH_ERR_INVALID_ARGUMENT;
97 server_host_public = kex->load_host_public_key(kex->hostkey_type,
98 kex->hostkey_nid, ssh);
99 server_host_private = kex->load_host_private_key(kex->hostkey_type,
100 kex->hostkey_nid, ssh);
101 if (server_host_public == NULL) {
102 r = SSH_ERR_NO_HOSTKEY_LOADED;
105 if ((client_public = EC_POINT_new(group)) == NULL) {
106 r = SSH_ERR_ALLOC_FAIL;
109 if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
110 (r = sshpkt_get_end(ssh)) != 0)
114 fputs("client public key:\n", stderr);
115 sshkey_dump_ec_point(group, client_public);
117 if (sshkey_ec_validate_public(group, client_public) != 0) {
118 sshpkt_disconnect(ssh, "invalid client public key");
119 r = SSH_ERR_MESSAGE_INCOMPLETE;
123 /* Calculate shared_secret */
124 klen = (EC_GROUP_get_degree(group) + 7) / 8;
125 if ((kbuf = malloc(klen)) == NULL ||
126 (shared_secret = BN_new()) == NULL) {
127 r = SSH_ERR_ALLOC_FAIL;
130 if (ECDH_compute_key(kbuf, klen, client_public,
131 server_key, NULL) != (int)klen ||
132 BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
133 r = SSH_ERR_LIBCRYPTO_ERROR;
138 dump_digest("shared secret", kbuf, klen);
141 if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
144 hashlen = sizeof(hash);
145 if ((r = kex_ecdh_hash(
148 kex->client_version_string,
149 kex->server_version_string,
150 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
151 sshbuf_ptr(kex->my), sshbuf_len(kex->my),
152 server_host_key_blob, sbloblen,
154 EC_KEY_get0_public_key(server_key),
156 hash, &hashlen)) != 0)
159 /* save session id := H */
160 if (kex->session_id == NULL) {
161 kex->session_id_len = hashlen;
162 kex->session_id = malloc(kex->session_id_len);
163 if (kex->session_id == NULL) {
164 r = SSH_ERR_ALLOC_FAIL;
167 memcpy(kex->session_id, hash, kex->session_id_len);
171 if ((r = kex->sign(server_host_private, server_host_public, &signature,
172 &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
175 /* destroy_sensitive_data(); */
177 public_key = EC_KEY_get0_public_key(server_key);
178 /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
179 if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
180 (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
181 (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
182 (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
183 (r = sshpkt_send(ssh)) != 0)
186 if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
187 r = kex_send_newkeys(ssh);
189 explicit_bzero(hash, sizeof(hash));
190 EC_KEY_free(kex->ec_client_key);
191 kex->ec_client_key = NULL;
192 EC_KEY_free(server_key);
194 explicit_bzero(kbuf, klen);
197 BN_clear_free(shared_secret);
198 free(server_host_key_blob);
202 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */