/**
* \brief AES block cipher, ESP32-S2 hardware accelerated version
* Based on mbedTLS FIPS-197 compliant version.
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* Additions Copyright (C) 2016-2020, Espressif Systems (Shanghai) PTE Ltd
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
/*
* The AES block cipher was designed by Vincent Rijmen and Joan Daemen.
*
* http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf
* http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
*/
/* Below XTS implementation is copied aes.c of mbedtls library.
* When MBEDTLS_AES_ALT is defined mbedtls expects alternate
* definition of XTS functions to be available. Even if this
* could have been avoided, it is done for consistency reason.
*/
#include <stdio.h>
#include <string.h>
#include <sys/lock.h>
#include "mbedtls/aes.h"
#if CONFIG_IDF_TARGET_ESP32
#include "esp32/aes.h"
#elif CONFIG_IDF_TARGET_ESP32S2
#include "esp32s2/aes.h"
#endif
void esp_aes_xts_init( esp_aes_xts_context *ctx )
{
esp_aes_init( &ctx->crypt );
esp_aes_init( &ctx->tweak );
}
void esp_aes_xts_free( esp_aes_xts_context *ctx )
{
esp_aes_free( &ctx->crypt );
esp_aes_free( &ctx->tweak );
}
static int esp_aes_xts_decode_keys( const unsigned char *key,
unsigned int keybits,
const unsigned char **key1,
unsigned int *key1bits,
const unsigned char **key2,
unsigned int *key2bits )
{
const unsigned int half_keybits = keybits / 2;
const unsigned int half_keybytes = half_keybits / 8;
switch ( keybits ) {
case 256: break;
case 512: break;
default : return ( MBEDTLS_ERR_AES_INVALID_KEY_LENGTH );
}
*key1bits = half_keybits;
*key2bits = half_keybits;
*key1 = &key[0];
*key2 = &key[half_keybytes];
return 0;
}
int esp_aes_xts_setkey_enc( esp_aes_xts_context *ctx,
const unsigned char *key,
unsigned int keybits)
{
int ret;
const unsigned char *key1, *key2;
unsigned int key1bits, key2bits;
ret = esp_aes_xts_decode_keys( key, keybits, &key1, &key1bits,
&key2, &key2bits );
if ( ret != 0 ) {
return ( ret );
}
/* Set the tweak key. Always set tweak key for the encryption mode. */
ret = esp_aes_setkey( &ctx->tweak, key2, key2bits );
if ( ret != 0 ) {
return ( ret );
}
/* Set crypt key for encryption. */
return esp_aes_setkey( &ctx->crypt, key1, key1bits );
}
int esp_aes_xts_setkey_dec( esp_aes_xts_context *ctx,
const unsigned char *key,
unsigned int keybits)
{
int ret;
const unsigned char *key1, *key2;
unsigned int key1bits, key2bits;
ret = esp_aes_xts_decode_keys( key, keybits, &key1, &key1bits,
&key2, &key2bits );
if ( ret != 0 ) {
return ( ret );
}
/* Set the tweak key. Always set tweak key for encryption. */
ret = esp_aes_setkey( &ctx->tweak, key2, key2bits );
if ( ret != 0 ) {
return ( ret );
}
/* Set crypt key for decryption. */
return esp_aes_setkey( &ctx->crypt, key1, key1bits );
}
/* Endianess with 64 bits values */
#ifndef GET_UINT64_LE
#define GET_UINT64_LE(n,b,i) \
{ \
(n) = ( (uint64_t) (b)[(i) + 7] << 56 ) \
| ( (uint64_t) (b)[(i) + 6] << 48 ) \
| ( (uint64_t) (b)[(i) + 5] << 40 ) \
| ( (uint64_t) (b)[(i) + 4] << 32 ) \
| ( (uint64_t) (b)[(i) + 3] << 24 ) \
| ( (uint64_t) (b)[(i) + 2] << 16 ) \
| ( (uint64_t) (b)[(i) + 1] << 8 ) \
| ( (uint64_t) (b)[(i) ] ); \
}
#endif
#ifndef PUT_UINT64_LE
#define PUT_UINT64_LE(n,b,i) \
{ \
(b)[(i) + 7] = (unsigned char) ( (n) >> 56 ); \
(b)[(i) + 6] = (unsigned char) ( (n) >> 48 ); \
(b)[(i) + 5] = (unsigned char) ( (n) >> 40 ); \
(b)[(i) + 4] = (unsigned char) ( (n) >> 32 ); \
(b)[(i) + 3] = (unsigned char) ( (n) >> 24 ); \
(b)[(i) + 2] = (unsigned char) ( (n) >> 16 ); \
(b)[(i) + 1] = (unsigned char) ( (n) >> 8 ); \
(b)[(i) ] = (unsigned char) ( (n) ); \
}
#endif
/*
* GF(2^128) multiplication function
*
* This function multiplies a field element by x in the polynomial field
* representation. It uses 64-bit word operations to gain speed but compensates
* for machine endianess and hence works correctly on both big and little
* endian machines.
*/
static void esp_gf128mul_x_ble( unsigned char r[16],
const unsigned char x[16] )
{
uint64_t a, b, ra, rb;
GET_UINT64_LE( a, x, 0 );
GET_UINT64_LE( b, x, 8 );
ra = ( a << 1 ) ^ 0x0087 >> ( 8 - ( ( b >> 63 ) << 3 ) );
rb = ( a >> 63 ) | ( b << 1 );
PUT_UINT64_LE( ra, r, 0 );
PUT_UINT64_LE( rb, r, 8 );
}
/*
* AES-XTS buffer encryption/decryption
*/
int esp_aes_crypt_xts( esp_aes_xts_context *ctx,
int mode,
size_t length,
const unsigned char data_unit[16],
const unsigned char *input,
unsigned char *output )
{
int ret;
size_t blocks = length / 16;
size_t leftover = length % 16;
unsigned char tweak[16];
unsigned char prev_tweak[16];
unsigned char tmp[16];
/* Sectors must be at least 16 bytes. */
if ( length < 16 ) {
return MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH;
}
/* NIST SP 80-38E disallows data units larger than 2**20 blocks. */
if ( length > ( 1 << 20 ) * 16 ) {
return MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH;
}
/* Compute the tweak. */
ret = esp_aes_crypt_ecb( &ctx->tweak, MBEDTLS_AES_ENCRYPT,
data_unit, tweak );
if ( ret != 0 ) {
return ( ret );
}
while ( blocks-- ) {
size_t i;
if ( leftover && ( mode == MBEDTLS_AES_DECRYPT ) && blocks == 0 ) {
/* We are on the last block in a decrypt operation that has
* leftover bytes, so we need to use the next tweak for this block,
* and this tweak for the lefover bytes. Save the current tweak for
* the leftovers and then update the current tweak for use on this,
* the last full block. */
memcpy( prev_tweak, tweak, sizeof( tweak ) );
esp_gf128mul_x_ble( tweak, tweak );
}
for ( i = 0; i < 16; i++ ) {
tmp[i] = input[i] ^ tweak[i];
}
ret = esp_aes_crypt_ecb( &ctx->crypt, mode, tmp, tmp );
if ( ret != 0 ) {
return ( ret );
}
for ( i = 0; i < 16; i++ ) {
output[i] = tmp[i] ^ tweak[i];
}
/* Update the tweak for the next block. */
esp_gf128mul_x_ble( tweak, tweak );
output += 16;
input += 16;
}
if ( leftover ) {
/* If we are on the leftover bytes in a decrypt operation, we need to
* use the previous tweak for these bytes (as saved in prev_tweak). */
unsigned char *t = mode == MBEDTLS_AES_DECRYPT ? prev_tweak : tweak;
/* We are now on the final part of the data unit, which doesn't divide
* evenly by 16. It's time for ciphertext stealing. */
size_t i;
unsigned char *prev_output = output - 16;
/* Copy ciphertext bytes from the previous block to our output for each
* byte of cyphertext we won't steal. At the same time, copy the
* remainder of the input for this final round (since the loop bounds
* are the same). */
for ( i = 0; i < leftover; i++ ) {
output[i] = prev_output[i];
tmp[i] = input[i] ^ t[i];
}
/* Copy ciphertext bytes from the previous block for input in this
* round. */
for ( ; i < 16; i++ ) {
tmp[i] = prev_output[i] ^ t[i];
}
ret = esp_aes_crypt_ecb( &ctx->crypt, mode, tmp, tmp );
if ( ret != 0 ) {
return ret;
}
/* Write the result back to the previous block, overriding the previous
* output we copied. */
for ( i = 0; i < 16; i++ ) {
prev_output[i] = tmp[i] ^ t[i];
}
}
return ( 0 );
}