/* ecdh.c -- Diffie-Hellman key exchange handling Copyright (C) 2011 Guus Sliepen This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include "system.h" #include "utils.h" #include "xalloc.h" #include #include #include #include "ecdh.h" #include "logger.h" bool ecdh_generate_public(ecdh_t *ecdh, void *pubkey) { *ecdh = EC_KEY_new_by_curve_name(NID_secp521r1); if(!EC_KEY_generate_key(*ecdh)) { logger(LOG_ERR, "Generating EC key failed: %s", ERR_error_string(ERR_get_error(), NULL)); abort(); } const EC_POINT *point = EC_KEY_get0_public_key(*ecdh); if(!point) { logger(LOG_ERR, "Getting public key failed: %s", ERR_error_string(ERR_get_error(), NULL)); abort(); } size_t result = EC_POINT_point2oct(EC_KEY_get0_group(*ecdh), point, POINT_CONVERSION_COMPRESSED, pubkey, ECDH_SIZE, NULL); if(!result) { logger(LOG_ERR, "Converting EC_POINT to binary failed: %s", ERR_error_string(ERR_get_error(), NULL)); abort(); } return true; } bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared) { EC_POINT *point = EC_POINT_new(EC_KEY_get0_group(*ecdh)); if(!point) { logger(LOG_ERR, "EC_POINT_new() failed: %s", ERR_error_string(ERR_get_error(), NULL)); abort(); } int result = EC_POINT_oct2point(EC_KEY_get0_group(*ecdh), point, pubkey, ECDH_SIZE, NULL); if(!result) { logger(LOG_ERR, "Converting binary to EC_POINT failed: %s", ERR_error_string(ERR_get_error(), NULL)); abort(); } result = ECDH_compute_key(shared, ECDH_SIZE, point, *ecdh, NULL); EC_POINT_free(point); EC_KEY_free(*ecdh); *ecdh = NULL; if(!result) { logger(LOG_ERR, "Computing Elliptic Curve Diffie-Hellman shared key failed: %s", ERR_error_string(ERR_get_error(), NULL)); return false; } return true; }