209 lines
4.1 KiB
C
209 lines
4.1 KiB
C
/*
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* Copyright (C) 2014 Andreas Steffen
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* HSR Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#include "mgf1_bitspender.h"
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#include <crypto/mgf1/mgf1.h>
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typedef struct private_mgf1_bitspender_t private_mgf1_bitspender_t;
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/**
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* Private data structure for mgf1_bitspender_t object
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*/
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struct private_mgf1_bitspender_t {
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/**
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* Public interface.
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*/
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mgf1_bitspender_t public;
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/**
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* MGF1 bit mask generator
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*/
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mgf1_t *mgf1;
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/**
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* Octet storage (accommodates up to 64 octets)
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*/
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uint8_t octets[HASH_SIZE_SHA512];
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/**
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* Length of the returned hash value in octets
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*/
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int hash_len;
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/**
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* Number of generated octets
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*/
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int octets_count;
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/**
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* Number of available octets
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*/
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int octets_left;
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/**
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* Bit storage (accommodates up to 32 bits)
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*/
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uint32_t bits;
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/**
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* Number of available bits
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*/
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int bits_left;
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/**
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* Byte storage (accommodates up to 4 bytes)
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*/
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uint8_t bytes[4];
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/**
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* Number of available bytes
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*/
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int bytes_left;
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};
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METHOD(mgf1_bitspender_t, get_bits, bool,
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private_mgf1_bitspender_t *this, int bits_needed, uint32_t *bits)
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{
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int bits_now;
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*bits = 0x00000000;
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if (bits_needed == 0)
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{
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/* trivial */
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return TRUE;
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}
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if (bits_needed > 32)
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{
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/* too many bits requested */
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return FALSE;
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}
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while (bits_needed)
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{
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if (this->bits_left == 0)
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{
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if (this->octets_left == 0)
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{
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/* get another block from MGF1 */
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if (!this->mgf1->get_mask(this->mgf1, this->hash_len,
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this->octets))
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{
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/* no block available */
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return FALSE;
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}
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this->octets_left = this->hash_len;
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this->octets_count += this->hash_len;
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}
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this->bits = untoh32(this->octets + this->hash_len -
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this->octets_left);
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this->bits_left = 32;
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this->octets_left -= 4;
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}
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if (bits_needed > this->bits_left)
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{
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bits_now = this->bits_left;
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this->bits_left = 0;
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bits_needed -= bits_now;
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}
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else
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{
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bits_now = bits_needed;
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this->bits_left -= bits_needed;
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bits_needed = 0;
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}
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if (bits_now == 32)
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{
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*bits = this->bits;
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}
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else
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{
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*bits <<= bits_now;
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*bits |= this->bits >> this->bits_left;
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if (this->bits_left)
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{
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this->bits &= 0xffffffff >> (32 - this->bits_left);
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}
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}
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}
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return TRUE;
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}
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METHOD(mgf1_bitspender_t, get_byte, bool,
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private_mgf1_bitspender_t *this, uint8_t *byte)
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{
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if (this->bytes_left == 0)
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{
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if (this->octets_left == 0)
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{
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/* get another block from MGF1 */
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if (!this->mgf1->get_mask(this->mgf1, this->hash_len, this->octets))
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{
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/* no block available */
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return FALSE;
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}
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this->octets_left = this->hash_len;
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this->octets_count += this->hash_len;
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}
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memcpy(this->bytes, this->octets + this->hash_len - this->octets_left, 4);
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this->bytes_left = 4;
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this->octets_left -= 4;
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}
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*byte = this->bytes[4 - this->bytes_left--];
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return TRUE;
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}
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METHOD(mgf1_bitspender_t, destroy, void,
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private_mgf1_bitspender_t *this)
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{
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DBG2(DBG_LIB, "mgf1 generated %u octets", this->octets_count);
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memwipe(this->octets, sizeof(this->octets));
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this->mgf1->destroy(this->mgf1);
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free(this);
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}
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/**
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* See header.
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*/
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mgf1_bitspender_t *mgf1_bitspender_create(hash_algorithm_t alg, chunk_t seed,
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bool hash_seed)
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{
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private_mgf1_bitspender_t *this;
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mgf1_t *mgf1;
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mgf1 = mgf1_create(alg, seed, hash_seed);
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if (!mgf1)
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{
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return NULL;
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}
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DBG2(DBG_LIB, "mgf1 based on %N is seeded with %u octets",
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hash_algorithm_short_names, alg, seed.len);
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INIT(this,
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.public = {
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.get_bits = _get_bits,
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.get_byte = _get_byte,
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.destroy = _destroy,
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},
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.mgf1 = mgf1,
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.hash_len = mgf1->get_hash_size(mgf1),
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);
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return &this->public;
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}
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