release/src/router/tinc/src/openssl/ecdh.c

   1 /*
   2     ecdh.c -- Diffie-Hellman key exchange handling
   3     Copyright (C) 2011-2013 Guus Sliepen <guus@tinc-vpn.org>
   4
   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.
   9
  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.
  14
  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.
  18 */
  19
  20 #include "../system.h"
  21
  22 #include <openssl/err.h>
  23 #include <openssl/ec.h>
  24 #include <openssl/ecdh.h>
  25 #include <openssl/obj_mac.h>
  26
  27 #define __TINC_ECDH_INTERNAL__
  28 typedef EC_KEY ecdh_t;
  29
  30 #include "../ecdh.h"
  31 #include "../logger.h"
  32 #include "../utils.h"
  33 #include "../xalloc.h"
  34
  35 ecdh_t *ecdh_generate_public(void *pubkey) {
  36         ecdh_t *ecdh = EC_KEY_new_by_curve_name(NID_secp521r1);
  37         if(!ecdh) {
  38                 logger(DEBUG_ALWAYS, LOG_ERR, "Generating EC key_by_curve_name failed: %s", ERR_error_string(ERR_get_error(), NULL));
  39                 return false;
  40         }
  41
  42         if(!EC_KEY_generate_key(ecdh)) {
  43                 EC_KEY_free(ecdh);
  44                 logger(DEBUG_ALWAYS, LOG_ERR, "Generating EC key failed: %s", ERR_error_string(ERR_get_error(), NULL));
  45                 return NULL;
  46         }
  47
  48         const EC_POINT *point = EC_KEY_get0_public_key(ecdh);
  49         if(!point) {
  50                 EC_KEY_free(ecdh);
  51                 logger(DEBUG_ALWAYS, LOG_ERR, "Getting public key failed: %s", ERR_error_string(ERR_get_error(), NULL));
  52                 return NULL;
  53         }
  54
  55         size_t result = EC_POINT_point2oct(EC_KEY_get0_group(ecdh), point, POINT_CONVERSION_COMPRESSED, pubkey, ECDH_SIZE, NULL);
  56         if(!result) {
  57                 EC_KEY_free(ecdh);
  58                 logger(DEBUG_ALWAYS, LOG_ERR, "Converting EC_POINT to binary failed: %s", ERR_error_string(ERR_get_error(), NULL));
  59                 return NULL;
  60         }
  61
  62         return ecdh;
  63 }
  64
  65 bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared) {
  66         EC_POINT *point = EC_POINT_new(EC_KEY_get0_group(ecdh));
  67         if(!point) {
  68                 logger(DEBUG_ALWAYS, LOG_ERR, "EC_POINT_new() failed: %s", ERR_error_string(ERR_get_error(), NULL));
  69                 EC_KEY_free(ecdh);
  70                 return false;
  71         }
  72
  73         int result = EC_POINT_oct2point(EC_KEY_get0_group(ecdh), point, pubkey, ECDH_SIZE, NULL);
  74         if(!result) {
  75                 EC_POINT_free(point);
  76                 EC_KEY_free(ecdh);
  77                 logger(DEBUG_ALWAYS, LOG_ERR, "Converting binary to EC_POINT failed: %s", ERR_error_string(ERR_get_error(), NULL));
  78                 return false;
  79         }
  80
  81         result = ECDH_compute_key(shared, ECDH_SIZE, point, ecdh, NULL);
  82         EC_POINT_free(point);
  83         EC_KEY_free(ecdh);
  84
  85         if(!result) {
  86                 logger(DEBUG_ALWAYS, LOG_ERR, "Computing Elliptic Curve Diffie-Hellman shared key failed: %s", ERR_error_string(ERR_get_error(), NULL));
  87                 return false;
  88         }
  89
  90         return true;
  91 }
  92
  93 void ecdh_free(ecdh_t *ecdh) {
  94         if(ecdh)
  95                 EC_KEY_free(ecdh);
  96 }