92 lines
3 KiB
C
92 lines
3 KiB
C
/*
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* AFsplitter - Anti forensic information splitter
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* Copyright 2004, Clemens Fruhwirth <clemens@endorphin.org>
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*
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* AFsplitter diffuses information over a large stripe of data,
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* therefor supporting secure data destruction.
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*
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* This program is grub_free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the grub_free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the grub_free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include <grub/crypto.h>
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#include <grub/mm.h>
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#include <grub/misc.h>
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gcry_err_code_t AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src,
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grub_uint8_t * dst, grub_size_t blocksize,
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grub_size_t blocknumbers);
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static void
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diffuse (const gcry_md_spec_t * hash, grub_uint8_t * src,
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grub_uint8_t * dst, grub_size_t size)
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{
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grub_size_t i;
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grub_uint32_t IV; /* host byte order independend hash IV */
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grub_size_t fullblocks = size / hash->mdlen;
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int padding = size % hash->mdlen;
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grub_uint8_t final[GRUB_CRYPTO_MAX_MDLEN];
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grub_uint8_t temp[sizeof (IV) + GRUB_CRYPTO_MAX_MDLEN];
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/* hash block the whole data set with different IVs to produce
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* more than just a single data block
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*/
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for (i = 0; i < fullblocks; i++)
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{
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IV = grub_cpu_to_be32 (i);
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grub_memcpy (temp, &IV, sizeof (IV));
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grub_memcpy (temp + sizeof (IV), src + hash->mdlen * i, hash->mdlen);
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grub_crypto_hash (hash, dst + hash->mdlen * i, temp,
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sizeof (IV) + hash->mdlen);
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}
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if (padding)
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{
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IV = grub_cpu_to_be32 (i);
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grub_memcpy (temp, &IV, sizeof (IV));
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grub_memcpy (temp + sizeof (IV), src + hash->mdlen * i, padding);
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grub_crypto_hash (hash, final, temp, sizeof (IV) + padding);
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grub_memcpy (dst + hash->mdlen * i, final, padding);
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}
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}
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/**
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* Merges the splitted master key stored on disk into the original key
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*/
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gcry_err_code_t
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AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src, grub_uint8_t * dst,
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grub_size_t blocksize, grub_size_t blocknumbers)
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{
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grub_size_t i;
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grub_uint8_t *bufblock;
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if (hash->mdlen > GRUB_CRYPTO_MAX_MDLEN || hash->mdlen == 0)
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return GPG_ERR_INV_ARG;
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bufblock = grub_zalloc (blocksize);
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if (bufblock == NULL)
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return GPG_ERR_OUT_OF_MEMORY;
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grub_memset (bufblock, 0, blocksize);
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for (i = 0; i < blocknumbers - 1; i++)
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{
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grub_crypto_xor (bufblock, src + (blocksize * i), bufblock, blocksize);
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diffuse (hash, bufblock, bufblock, blocksize);
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}
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grub_crypto_xor (dst, src + (i * blocksize), bufblock, blocksize);
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grub_free (bufblock);
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return GPG_ERR_NO_ERROR;
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}
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