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[crypto] Add AES key-wrap mode (RFC 3394)
The unwrapping half is used by WPA2 code; the wrapping half is currently unused. Signed-off-by: Marty Connor <mdc@etherboot.org>
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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. | ||
*/ | ||
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FILE_LICENCE ( GPL2_OR_LATER ); | ||
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#include <stdlib.h> | ||
#include <string.h> | ||
#include <gpxe/crypto.h> | ||
#include <gpxe/aes.h> | ||
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/** | ||
* 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 ); | ||
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if ( ! aes_ctx ) | ||
return -1; | ||
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cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 ); | ||
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/* Set up */ | ||
memset ( A, 0xA6, sizeof ( A ) ); | ||
memmove ( dest + 8, src, nblk * 8 ); | ||
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/* 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; | ||
} | ||
} | ||
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free ( aes_ctx ); | ||
return 0; | ||
} | ||
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/** | ||
* 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 ); | ||
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if ( ! aes_ctx ) | ||
return -1; | ||
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cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 ); | ||
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/* Set up */ | ||
memcpy ( A, src, 8 ); | ||
memmove ( dest, src + 8, nblk * 8 ); | ||
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/* 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; | ||
} | ||
} | ||
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free ( aes_ctx ); | ||
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/* Check IV */ | ||
for ( i = 0; i < 8; i++ ) { | ||
if ( A[i] != 0xA6 ) | ||
return -1; | ||
} | ||
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return 0; | ||
} |
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