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/*
* Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <stdlib.h>
#include <string.h>
#include <gpxe/crypto.h>
#include <gpxe/aes.h>
/**
* Wrap a key or other data using AES Key Wrap (RFC 3394)
*
* @v kek Key Encryption Key, 16 bytes
* @v src Data to encrypt
* @v nblk Number of 8-byte blocks in @a data
* @ret dest Encrypted data (8 bytes longer than input)
*
* The algorithm is implemented such that @a src and @a dest may point
* to the same buffer.
*/
int aes_wrap ( const void *kek, const void *src, void *dest, int nblk )
{
u8 *A = dest;
u8 B[16];
u8 *R;
int i, j;
void *aes_ctx = malloc ( AES_CTX_SIZE );
if ( ! aes_ctx )
return -1;
cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
/* Set up */
memset ( A, 0xA6, sizeof ( A ) );
memmove ( dest + 8, src, nblk * 8 );
/* Wrap */
for ( j = 0; j < 6; j++ ) {
R = dest + 8;
for ( i = 1; i <= nblk; i++ ) {
memcpy ( B, A, 8 );
memcpy ( B + 8, R, 8 );
cipher_encrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
memcpy ( A, B, 8 );
A[7] ^= ( nblk * j ) + i;
memcpy ( R, B + 8, 8 );
R += 8;
}
}
free ( aes_ctx );
return 0;
}
/**
* Unwrap a key or other data using AES Key Wrap (RFC 3394)
*
* @v kek Key Encryption Key, 16 bytes
* @v src Data to decrypt
* @v nblk Number of 8-byte blocks in @e plaintext key
* @ret dest Decrypted data (8 bytes shorter than input)
* @ret rc Zero on success, nonzero on IV mismatch
*
* The algorithm is implemented such that @a src and @a dest may point
* to the same buffer.
*/
int aes_unwrap ( const void *kek, const void *src, void *dest, int nblk )
{
u8 A[8], B[16];
u8 *R;
int i, j;
void *aes_ctx = malloc ( AES_CTX_SIZE );
if ( ! aes_ctx )
return -1;
cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
/* Set up */
memcpy ( A, src, 8 );
memmove ( dest, src + 8, nblk * 8 );
/* Unwrap */
for ( j = 5; j >= 0; j-- ) {
R = dest + ( nblk - 1 ) * 8;
for ( i = nblk; i >= 1; i-- ) {
memcpy ( B, A, 8 );
memcpy ( B + 8, R, 8 );
B[7] ^= ( nblk * j ) + i;
cipher_decrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
memcpy ( A, B, 8 );
memcpy ( R, B + 8, 8 );
R -= 8;
}
}
free ( aes_ctx );
/* Check IV */
for ( i = 0; i < 8; i++ ) {
if ( A[i] != 0xA6 )
return -1;
}
return 0;
}
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