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/*
* AFsplitter - Anti forensic information splitter
* Copyright 2004, Clemens Fruhwirth <clemens@endorphin.org>
*
* AFsplitter diffuses information over a large stripe of data,
* therefor supporting secure data destruction.
*
* This program is grub_free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the grub_free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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 Library General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the grub_free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <grub/crypto.h>
#include <grub/dl.h>
#include <grub/mm.h>
#include <grub/misc.h>
GRUB_MOD_LICENSE ("GPLv2+");
gcry_err_code_t AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src,
grub_uint8_t * dst, grub_size_t blocksize,
grub_size_t blocknumbers);
static void
diffuse (const gcry_md_spec_t * hash, grub_uint8_t * src,
grub_uint8_t * dst, grub_size_t size)
{
grub_size_t i;
grub_uint32_t IV; /* host byte order independend hash IV */
grub_size_t fullblocks = size / hash->mdlen;
int padding = size % hash->mdlen;
grub_uint8_t final[GRUB_CRYPTO_MAX_MDLEN];
grub_uint8_t temp[sizeof (IV) + GRUB_CRYPTO_MAX_MDLEN];
/* hash block the whole data set with different IVs to produce
* more than just a single data block
*/
for (i = 0; i < fullblocks; i++)
{
IV = grub_cpu_to_be32 (i);
grub_memcpy (temp, &IV, sizeof (IV));
grub_memcpy (temp + sizeof (IV), src + hash->mdlen * i, hash->mdlen);
grub_crypto_hash (hash, dst + hash->mdlen * i, temp,
sizeof (IV) + hash->mdlen);
}
if (padding)
{
IV = grub_cpu_to_be32 (i);
grub_memcpy (temp, &IV, sizeof (IV));
grub_memcpy (temp + sizeof (IV), src + hash->mdlen * i, padding);
grub_crypto_hash (hash, final, temp, sizeof (IV) + padding);
grub_memcpy (dst + hash->mdlen * i, final, padding);
}
}
/**
* Merges the splitted master key stored on disk into the original key
*/
gcry_err_code_t
AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src, grub_uint8_t * dst,
grub_size_t blocksize, grub_size_t blocknumbers)
{
grub_size_t i;
grub_uint8_t *bufblock;
if (hash->mdlen > GRUB_CRYPTO_MAX_MDLEN || hash->mdlen == 0)
return GPG_ERR_INV_ARG;
bufblock = grub_zalloc (blocksize);
if (bufblock == NULL)
return GPG_ERR_OUT_OF_MEMORY;
grub_memset (bufblock, 0, blocksize);
for (i = 0; i < blocknumbers - 1; i++)
{
grub_crypto_xor (bufblock, src + (blocksize * i), bufblock, blocksize);
diffuse (hash, bufblock, bufblock, blocksize);
}
grub_crypto_xor (dst, src + (i * blocksize), bufblock, blocksize);
grub_free (bufblock);
return GPG_ERR_NO_ERROR;
}
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