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/*
* Copyright (C) 2010 Martin Willi
* Copyright (C) 2010 revosec AG
*
* 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. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* 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.
*/
#include "ctr_ipsec_crypter.h"
typedef struct private_ctr_ipsec_crypter_t private_ctr_ipsec_crypter_t;
/**
* Private data of an ctr_ipsec_crypter_t object.
*/
struct private_ctr_ipsec_crypter_t {
/**
* Public ctr_ipsec_crypter_t interface.
*/
ctr_ipsec_crypter_t public;
/**
* Underlying CBC crypter
*/
crypter_t *crypter;
/**
* counter state
*/
struct {
char nonce[4];
char iv[8];
u_int32_t counter;
} __attribute__((packed)) state;
};
/**
* Do the CTR crypto operation
*/
static void crypt_ctr(private_ctr_ipsec_crypter_t *this,
chunk_t in, chunk_t out)
{
size_t is, bs;
chunk_t state;
is = this->crypter->get_iv_size(this->crypter);
bs = sizeof(this->state);
this->state.counter = htonl(1);
state = chunk_create((char*)&this->state, bs);
while (in.len > 0)
{
char iv[is], block[bs];
memset(iv, 0, is);
memcpy(block, state.ptr, bs);
this->crypter->encrypt(this->crypter,
chunk_create(block, bs), chunk_create(iv, is), NULL);
chunk_increment(state);
if (in.ptr != out.ptr)
{
memcpy(out.ptr, in.ptr, min(in.len, bs));
}
memxor(out.ptr, block, min(in.len, bs));
in = chunk_skip(in, bs);
out = chunk_skip(out, bs);
}
}
METHOD(crypter_t, crypt, void,
private_ctr_ipsec_crypter_t *this, chunk_t in, chunk_t iv, chunk_t *out)
{
memcpy(this->state.iv, iv.ptr, sizeof(this->state.iv));
if (out)
{
*out = chunk_alloc(in.len);
crypt_ctr(this, in, *out);
}
else
{
crypt_ctr(this, in, in);
}
}
METHOD(crypter_t, get_block_size, size_t,
private_ctr_ipsec_crypter_t *this)
{
return 1;
}
METHOD(crypter_t, get_iv_size, size_t,
private_ctr_ipsec_crypter_t *this)
{
return sizeof(this->state.iv);
}
METHOD(crypter_t, get_key_size, size_t,
private_ctr_ipsec_crypter_t *this)
{
return this->crypter->get_key_size(this->crypter)
+ sizeof(this->state.nonce);
}
METHOD(crypter_t, set_key, void,
private_ctr_ipsec_crypter_t *this, chunk_t key)
{
memcpy(this->state.nonce, key.ptr + key.len - sizeof(this->state.nonce),
sizeof(this->state.nonce));
key.len -= sizeof(this->state.nonce);
this->crypter->set_key(this->crypter, key);
}
METHOD(crypter_t, destroy, void,
private_ctr_ipsec_crypter_t *this)
{
this->crypter->destroy(this->crypter);
free(this);
}
/**
* See header
*/
ctr_ipsec_crypter_t *ctr_ipsec_crypter_create(encryption_algorithm_t algo,
size_t key_size)
{
private_ctr_ipsec_crypter_t *this;
switch (algo)
{
case ENCR_AES_CTR:
algo = ENCR_AES_CBC;
break;
case ENCR_CAMELLIA_CTR:
algo = ENCR_CAMELLIA_CBC;
break;
default:
return NULL;
}
INIT(this,
.public = {
.crypter = {
.encrypt = _crypt,
.decrypt = _crypt,
.get_block_size = _get_block_size,
.get_iv_size = _get_iv_size,
.get_key_size = _get_key_size,
.set_key = _set_key,
.destroy = _destroy,
},
},
.crypter = lib->crypto->create_crypter(lib->crypto, algo, key_size),
);
if (!this->crypter)
{
free(this);
return NULL;
}
return &this->public;
}
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