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/*
* Copyright (C) 2007 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.
*
* Alternatively, you may distribute this code in source or binary
* form, with or without modification, provided that the following
* conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the above disclaimer.
*
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the above
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/**
* @file
*
* Keyed-Hashing for Message Authentication
*/
#include <string.h>
#include <assert.h>
#include <ipxe/crypto.h>
#include <ipxe/hmac.h>
/**
* Initialise HMAC
*
* @v digest Digest algorithm to use
* @v ctx HMAC context
* @v key Key
* @v key_len Length of key
*/
void hmac_init ( struct digest_algorithm *digest, void *ctx, const void *key,
size_t key_len ) {
hmac_context_t ( digest ) *hctx = ctx;
unsigned int i;
/* Construct input pad */
memset ( hctx->pad, 0, sizeof ( hctx->pad ) );
if ( key_len <= sizeof ( hctx->pad ) ) {
memcpy ( hctx->pad, key, key_len );
} else {
digest_init ( digest, hctx->ctx );
digest_update ( digest, hctx->ctx, key, key_len );
digest_final ( digest, hctx->ctx, hctx->pad );
}
for ( i = 0 ; i < sizeof ( hctx->pad ) ; i++ ) {
hctx->pad[i] ^= 0x36;
}
/* Start inner hash */
digest_init ( digest, hctx->ctx );
digest_update ( digest, hctx->ctx, hctx->pad, sizeof ( hctx->pad ) );
}
/**
* Finalise HMAC
*
* @v digest Digest algorithm to use
* @v ctx HMAC context
* @v hmac HMAC digest to fill in
*/
void hmac_final ( struct digest_algorithm *digest, void *ctx, void *hmac ) {
hmac_context_t ( digest ) *hctx = ctx;
unsigned int i;
/* Construct output pad from input pad */
for ( i = 0 ; i < sizeof ( hctx->pad ) ; i++ ) {
hctx->pad[i] ^= 0x6a;
}
/* Finish inner hash */
digest_final ( digest, hctx->ctx, hmac );
/* Perform outer hash */
digest_init ( digest, hctx->ctx );
digest_update ( digest, hctx->ctx, hctx->pad, sizeof ( hctx->pad ) );
digest_update ( digest, hctx->ctx, hmac, digest->digestsize );
digest_final ( digest, hctx->ctx, hmac );
/* Erase output pad (from which the key may be derivable) */
memset ( hctx->pad, 0, sizeof ( hctx->pad ) );
}
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