2 ecdh.c -- Diffie-Hellman key exchange handling
3 Copyright (C) 2011 Guus Sliepen <guus@tinc-vpn.org>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
24 #include <openssl/err.h>
25 #include <openssl/ec.h>
26 #include <openssl/obj_mac.h>
31 EC_GROUP *secp256k1 = NULL;
32 EC_GROUP *secp384r1 = NULL;
33 EC_GROUP *secp521r1 = NULL;
36 static void *kdf(const void *in, size_t inlen, void *out, size_t *outlen) {
37 memcpy(out, in, inlen);
42 bool ecdh_generate_public(ecdh_t *ecdh, void *pubkey) {
44 secp521r1 = EC_GROUP_new_by_curve_name(NID_secp521r1);
46 *ecdh = EC_KEY_new_by_curve_name(NID_secp521r1);
47 if(!EC_KEY_generate_key(*ecdh)) {
48 logger(LOG_ERR, "Generating EC key failed: %s", ERR_error_string(ERR_get_error(), NULL));
52 const EC_POINT *point = EC_KEY_get0_public_key(*ecdh);
54 logger(LOG_ERR, "Getting public key failed: %s", ERR_error_string(ERR_get_error(), NULL));
58 size_t result = EC_POINT_point2oct(secp521r1, point, POINT_CONVERSION_COMPRESSED, pubkey, ECDH_SIZE, NULL);
60 logger(LOG_ERR, "Converting EC_POINT to binary failed: %s", ERR_error_string(ERR_get_error(), NULL));
67 bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared) {
68 EC_POINT *point = EC_POINT_new(secp521r1);
70 int result = EC_POINT_oct2point(secp521r1, point, pubkey, ECDH_SIZE, NULL);
72 logger(LOG_ERR, "Converting binary to EC_POINT failed: %s", ERR_error_string(ERR_get_error(), NULL));
76 result = ECDH_compute_key(shared, ECDH_SIZE, point, *ecdh, kdf);
82 logger(LOG_ERR, "Computing Elliptic Curve Diffie-Hellman shared key failed: %s", ERR_error_string(ERR_get_error(), NULL));