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/*
* anytun
*
* The secure anycast tunneling protocol (satp) defines a protocol used
* for communication between any combination of unicast and anycast
* tunnel endpoints. It has less protocol overhead than IPSec in Tunnel
* mode and allows tunneling of every ETHER TYPE protocol (e.g.
* ethernet, ip, arp ...). satp directly includes cryptography and
* message authentication based on the methodes used by SRTP. It is
* intended to deliver a generic, scaleable and secure solution for
* tunneling and relaying of packets of any protocol.
*
*
* Copyright (C) 2007 anytun.org <satp@wirdorange.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* 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 (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "keyDerivation.h"
#include <stdexcept>
#include <iostream>
#include <string>
extern "C" {
#include <gcrypt.h>
}
const char* KeyDerivation::MIN_GCRYPT_VERSION = "1.2.3";
void KeyDerivation::init(Buffer key, Buffer salt)
{
gcry_error_t err;
if( !gcry_check_version( MIN_GCRYPT_VERSION ) )
{
std::cerr << "Invalid Version of libgcrypt, should be >= " << MIN_GCRYPT_VERSION << std::endl;
return;
}
/* Allocate a pool of 16k secure memory. This also drops priviliges
* on some systems. */
err = gcry_control(GCRYCTL_INIT_SECMEM, 16384, 0);
if( err )
{
std::cerr << "Failed to allocate 16k secure memory: " << gpg_strerror( err ) << std::endl;
return;
}
/* Tell Libgcrypt that initialization has completed. */
err = gcry_control(GCRYCTL_INITIALIZATION_FINISHED);
if( err )
{
std::cerr << "Failed to finish the initialization of libgcrypt" << gpg_strerror( err ) << std::endl;
return;
}
err = gcry_cipher_open( &cipher_, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CTR, 0 );
if( err )
{
std::cerr << "Failed to open cipher: " << gpg_strerror( err ) << std::endl;
return;
}
}
void KeyDerivation::setLogKDRate(const uint8_t log_rate)
{
if( log_rate < 49 )
ld_kdr_ = log_rate;
}
void KeyDerivation::generate(satp_prf_label label, seq_nr_t seq_nr, Buffer& key, u_int32_t length)
{
gcry_error_t err;
u_int8_t r = 0;
Buffer iv(16);
u_int8_t tmp_key_id[16];
// see at: http://tools.ietf.org/html/rfc3711#section-4.3
// * Let r = index DIV key_derivation_rate (with DIV as defined above).
// * Let key_id = <label> || r.
// * Let x = key_id XOR master_salt, where key_id and master_salt are
// aligned so that their least significant bits agree (right-
// alignment).
//
if( ld_kdr_ == -1 ) // means key_derivation_rate = 0
r = 0;
else
// FIXXME: kdr can be greater than 2^32 (= 2^48)
r = seq_nr / ( 0x01 << ld_kdr_ );
// FIXXME: why i cant access key_id via operator []?
for(u_int8_t i=0; i<sizeof(tmp_key_id); i++)
tmp_key_id[i] = 0x00;
tmp_key_id[0] = r;
tmp_key_id[1] = label;
Buffer key_id(tmp_key_id, 16);
iv = key_id ^ salt_;
err = gcry_cipher_reset( cipher_ );
if( err )
{
std::cerr << "Failed to reset cipher: " << gpg_strerror( err ) << std::endl;
}
err = gcry_cipher_encrypt( cipher_, key, key.getLength(), 0, 0 );
if( err )
{
std::cerr << "Failed to generate cipher bitstream: " << gpg_strerror( err ) << std::endl;
}
}
void KeyDerivation::clear()
{
gcry_cipher_close( cipher_ );
}
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