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