axtls_aes.c

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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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <string.h>
#include <errno.h>
#include <byteswap.h>
#include <gpxe/crypto.h>
#include <gpxe/cbc.h>
#include <gpxe/aes.h>
#include "crypto/axtls/crypto.h"

/** @file
 *
 * AES algorithm
 *
 */

/**
 * Set key
 *
 * @v ctx               Context
 * @v key               Key
 * @v keylen            Key length
 * @ret rc              Return status code
 */
static int aes_setkey ( void *ctx, const void *key, size_t keylen ) {
        struct aes_context *aes_ctx = ctx;
        AES_MODE mode;
        void *iv;

        switch ( keylen ) {
        case ( 128 / 8 ):
                mode = AES_MODE_128;
                break;
        case ( 256 / 8 ):
                mode = AES_MODE_256;
                break;
        default:
                return -EINVAL;
        }

        /* IV is not a relevant concept at this stage; use a dummy
         * value that will have no side-effects.
         */
        iv = &aes_ctx->axtls_ctx.iv;

        AES_set_key ( &aes_ctx->axtls_ctx, key, iv, mode );

        aes_ctx->decrypting = 0;

        return 0;
}

/**
 * Set initialisation vector
 *
 * @v ctx               Context
 * @v iv                Initialisation vector
 */
static void aes_setiv ( void *ctx __unused, const void *iv __unused ) {
        /* Nothing to do */
}

/**
 * Call AXTLS' AES_encrypt() or AES_decrypt() functions
 *
 * @v axtls_ctx         AXTLS AES context
 * @v src               Data to process
 * @v dst               Buffer for output
 * @v func              AXTLS AES function to call
 */
static void aes_call_axtls ( AES_CTX *axtls_ctx, const void *src, void *dst,
                             void ( * func ) ( const AES_CTX *axtls_ctx,
                                               uint32_t *data ) ){
        const uint32_t *srcl = src;
        uint32_t *dstl = dst;
        unsigned int i;

        /* AXTLS' AES_encrypt() and AES_decrypt() functions both
         * expect to deal with an array of four dwords in host-endian
         * order.
         */
        for ( i = 0 ; i < 4 ; i++ )
                dstl[i] = ntohl ( srcl[i] );
        func ( axtls_ctx, dstl );
        for ( i = 0 ; i < 4 ; i++ )
                dstl[i] = htonl ( dstl[i] );
}

/**
 * Encrypt data
 *
 * @v ctx               Context
 * @v src               Data to encrypt
 * @v dst               Buffer for encrypted data
 * @v len               Length of data
 */
static void aes_encrypt ( void *ctx, const void *src, void *dst,
                          size_t len ) {
        struct aes_context *aes_ctx = ctx;

        assert ( len == AES_BLOCKSIZE );
        if ( aes_ctx->decrypting )
                assert ( 0 );
        aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_encrypt );
}

/**
 * Decrypt data
 *
 * @v ctx               Context
 * @v src               Data to decrypt
 * @v dst               Buffer for decrypted data
 * @v len               Length of data
 */
static void aes_decrypt ( void *ctx, const void *src, void *dst,
                          size_t len ) {
        struct aes_context *aes_ctx = ctx;

        assert ( len == AES_BLOCKSIZE );
        if ( ! aes_ctx->decrypting ) {
                AES_convert_key ( &aes_ctx->axtls_ctx );
                aes_ctx->decrypting = 1;
        }
        aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_decrypt );
}

/** Basic AES algorithm */
struct cipher_algorithm aes_algorithm = {
        .name = "aes",
        .ctxsize = sizeof ( struct aes_context ),
        .blocksize = AES_BLOCKSIZE,
        .setkey = aes_setkey,
        .setiv = aes_setiv,
        .encrypt = aes_encrypt,
        .decrypt = aes_decrypt,
};

/* AES with cipher-block chaining */
CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
             aes_algorithm, struct aes_context, AES_BLOCKSIZE );