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/*
* Copyright (C) 2013 Tobias Brunner
* Hochschule fuer Technik Rapperswil
*
* 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 "iv_gen_seq.h"
/**
* Magic value for the initial IV state
*/
#define SEQ_IV_INIT_STATE (~(u_int64_t)0)
#define SEQ_IV_HIGH_MASK (1ULL << 63)
typedef struct private_iv_gen_t private_iv_gen_t;
/**
* Private data of an iv_gen_t object.
*/
struct private_iv_gen_t {
/**
* Public iv_gen_t interface.
*/
iv_gen_t public;
/**
* Previously passed sequence number in lower space to enforce uniqueness
*/
u_int64_t prevl;
/**
* Previously passed sequence number in upper space to enforce uniqueness
*/
u_int64_t prevh;
/**
* Salt to mask counter
*/
u_int8_t *salt;
};
METHOD(iv_gen_t, get_iv, bool,
private_iv_gen_t *this, u_int64_t seq, size_t size, u_int8_t *buffer)
{
u_int8_t iv[sizeof(u_int64_t)];
size_t len = size;
if (!this->salt)
{
return FALSE;
}
if (size < sizeof(u_int64_t))
{
return FALSE;
}
if (this->prevl != SEQ_IV_INIT_STATE && seq <= this->prevl)
{
seq |= SEQ_IV_HIGH_MASK;
if (this->prevh != SEQ_IV_INIT_STATE && seq <= this->prevh)
{
return FALSE;
}
}
if ((seq | SEQ_IV_HIGH_MASK) == SEQ_IV_INIT_STATE)
{
return FALSE;
}
if (seq & SEQ_IV_HIGH_MASK)
{
this->prevh = seq;
}
else
{
this->prevl = seq;
}
if (len > sizeof(u_int64_t))
{
len = sizeof(u_int64_t);
memset(buffer, 0, size - len);
}
htoun64(iv, seq);
memxor(iv, this->salt, sizeof(u_int64_t));
memcpy(buffer + size - len, iv + sizeof(u_int64_t) - len, len);
return TRUE;
}
METHOD(iv_gen_t, allocate_iv, bool,
private_iv_gen_t *this, u_int64_t seq, size_t size, chunk_t *chunk)
{
*chunk = chunk_alloc(size);
if (!get_iv(this, seq, chunk->len, chunk->ptr))
{
chunk_free(chunk);
return FALSE;
}
return TRUE;
}
METHOD(iv_gen_t, destroy, void,
private_iv_gen_t *this)
{
free(this->salt);
free(this);
}
iv_gen_t *iv_gen_seq_create()
{
private_iv_gen_t *this;
rng_t *rng;
INIT(this,
.public = {
.get_iv = _get_iv,
.allocate_iv = _allocate_iv,
.destroy = _destroy,
},
.prevl = SEQ_IV_INIT_STATE,
.prevh = SEQ_IV_INIT_STATE,
);
rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
if (rng)
{
this->salt = malloc(sizeof(u_int64_t));
if (!rng->get_bytes(rng, sizeof(u_int64_t), this->salt))
{
free(this->salt);
this->salt = NULL;
}
rng->destroy(rng);
}
return &this->public;
}
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