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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 <stdexcept>
#include <vector>
#include "cypher.h"
#include "keyDerivation.h"
extern "C" {
#include <srtp/crypto_kernel.h>
}
void Cypher::cypher(Buffer& buf, seq_nr_t seq_nr, sender_id_t sender_id)
{
Buffer stream = getBitStream(buf.getLength(), seq_nr, sender_id);
exor(buf, stream);
}
void Cypher::exor(Buffer& buf, const Buffer& bit_stream)
{
try
{
for(u_int32_t i; i<buf.getLength(); ++i)
buf[i] ^= bit_stream[i];
}
catch(std::out_of_range& o) {}
}
Buffer NullCypher::getBitStream(u_int32_t length, seq_nr_t seq_nr, sender_id_t sender_id)
{
Buffer buf(length);
for(u_int32_t i; i<length; ++i)
buf[i] = 0;
return buf;
}
void AesIcmCypher::setKey(Buffer key)
{
key_ = key;
}
void AesIcmCypher::setSalt(Buffer salt)
{
salt = salt;
}
void AesIcmCypher::cypher(Buffer& buf, seq_nr_t seq_nr, sender_id_t sender_id)
{
extern cipher_type_t aes_icm;
err_status_t status = err_status_ok;
cipher_t* cipher = NULL;
uint32_t length = 0;
v128_t iv, sid, seq, salt;
v128_set_to_zero(&iv);
v128_set_to_zero(&sid);
v128_set_to_zero(&seq);
v128_set_to_zero(&salt);
// allocate cipher
// FIXXME: why we do not can do this???
// status = cipher_type_alloc(&aes_icm, &cipher, key_.getLength());
status = cipher_type_alloc(&aes_icm, &cipher, 30);
if( status )
return;
// init cipher
status = cipher_init(cipher, key_.getBuf(), direction_any);
if( status )
{
cipher_dealloc(cipher);
return;
}
// set IV
// where the 128-bit integer value IV SHALL be defined by the SSRC, the
// SRTP packet index i, and the SRTP session salting key k_s, as below.
//
// IV = (k_s * 2^16) XOR (SSRC * 2^64) XOR (i * 2^16)
// sizeof(k_s) = 112 bit, random
// iv.v32[0] ^= 0;
// iv.v32[1] ^= sender_id;
// iv.v32[2] ^= (seq_nr >> 16);
// iv.v32[3] ^= (seq_nr << 16);
seq.v64[0] = seq_nr;
sid.v64[0] = sender_id;
v128_copy_octet_string(&salt, salt_.getBuf());
v128_left_shift(&salt, 16);
v128_left_shift(&sid, 64);
v128_left_shift(&seq, 16);
v128_xor(&iv, &salt, &sid);
v128_xor(&iv, &iv, &seq);
status = cipher_set_iv(cipher, &iv);
if( status )
cipher_dealloc(cipher);
length = buf.getLength();
status = cipher_encrypt(cipher, buf, &length);
status = cipher_dealloc(cipher);
}
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