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/*
* Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 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
* 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 Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <string.h>
#include <assert.h>
#include <ipxe/crypto.h>
#include <ipxe/cbc.h>
/** @file
*
* Cipher-block chaining
*
*/
/**
* XOR data blocks
*
* @v src Input data
* @v dst Second input data and output data buffer
* @v len Length of data
*/
static void cbc_xor ( const void *src, void *dst, size_t len ) {
const uint32_t *srcl = src;
uint32_t *dstl = dst;
unsigned int i;
/* Assume that block sizes will always be dword-aligned, for speed */
assert ( ( len % sizeof ( *srcl ) ) == 0 );
for ( i = 0 ; i < ( len / sizeof ( *srcl ) ) ; i++ )
dstl[i] ^= srcl[i];
}
/**
* Encrypt data
*
* @v ctx Context
* @v src Data to encrypt
* @v dst Buffer for encrypted data
* @v len Length of data
* @v raw_cipher Underlying cipher algorithm
* @v cbc_ctx CBC context
*/
void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
size_t blocksize = raw_cipher->blocksize;
assert ( ( len % blocksize ) == 0 );
while ( len ) {
cbc_xor ( src, cbc_ctx, blocksize );
cipher_encrypt ( raw_cipher, ctx, cbc_ctx, dst, blocksize );
memcpy ( cbc_ctx, dst, blocksize );
dst += blocksize;
src += blocksize;
len -= blocksize;
}
}
/**
* Decrypt data
*
* @v ctx Context
* @v src Data to decrypt
* @v dst Buffer for decrypted data
* @v len Length of data
* @v raw_cipher Underlying cipher algorithm
* @v cbc_ctx CBC context
*/
void cbc_decrypt ( void *ctx, const void *src, void *dst, size_t len,
struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
size_t blocksize = raw_cipher->blocksize;
uint8_t next_cbc_ctx[blocksize];
assert ( ( len % blocksize ) == 0 );
while ( len ) {
memcpy ( next_cbc_ctx, src, blocksize );
cipher_decrypt ( raw_cipher, ctx, src, dst, blocksize );
cbc_xor ( cbc_ctx, dst, blocksize );
memcpy ( cbc_ctx, next_cbc_ctx, blocksize );
dst += blocksize;
src += blocksize;
len -= blocksize;
}
}
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