mbedtls/library/constant_time.h

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/**
* Constant-time functions
*
* Copyright The Mbed TLS Contributors
* 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.
*/
#include "common.h"
#if defined(MBEDTLS_BIGNUM_C)
#include "mbedtls/bignum.h"
#endif
#if defined(MBEDTLS_SSL_TLS_C)
#include "ssl_misc.h"
#endif
#include <stddef.h>
int mbedtls_ssl_safer_memcmp( const void *a, const void *b, size_t n );
int mbedtls_constant_time_memcmp( const void *v1, const void *v2, size_t len );
unsigned char mbedtls_nist_kw_safer_memcmp( const void *a, const void *b, size_t n );
int mbedtls_safer_memcmp( const void *a, const void *b, size_t n );
unsigned mbedtls_cf_uint_mask( unsigned value );
size_t mbedtls_cf_size_mask( size_t bit );
size_t mbedtls_cf_size_mask_lt( size_t x, size_t y );
size_t mbedtls_cf_size_mask_ge( size_t x, size_t y );
size_t mbedtls_cf_size_bool_eq( size_t x, size_t y );
unsigned mbedtls_cf_size_gt( size_t size, size_t max );
#if defined(MBEDTLS_BIGNUM_C)
unsigned mbedtls_cf_mpi_uint_lt( const mbedtls_mpi_uint x,
const mbedtls_mpi_uint y );
#endif /* MBEDTLS_BIGNUM_C */
unsigned mbedtls_cf_uint_if( unsigned cond, unsigned if1, unsigned if0 );
size_t mbedtls_cf_size_if( unsigned cond, size_t if1, size_t if0 );
int mbedtls_cf_cond_select_sign( int a, int b, unsigned char second );
#if defined(MBEDTLS_BIGNUM_C)
void mbedtls_cf_mpi_uint_cond_assign( size_t n,
mbedtls_mpi_uint *dest,
const mbedtls_mpi_uint *src,
unsigned char assign );
#endif /* MBEDTLS_BIGNUM_C */
void mbedtls_cf_mem_move_to_left( void *start,
size_t total,
size_t offset );
void mbedtls_cf_memcpy_if_eq( unsigned char *dst,
const unsigned char *src,
size_t len,
size_t c1, size_t c2 );
/** Copy data from a secret position with constant flow.
*
* This function copies \p len bytes from \p src_base + \p offset_secret to \p
* dst, with a code flow and memory access pattern that does not depend on \p
* offset_secret, but only on \p offset_min, \p offset_max and \p len.
*
* \param dst The destination buffer. This must point to a writable
* buffer of at least \p len bytes.
* \param src_base The base of the source buffer. This must point to a
* readable buffer of at least \p offset_max + \p len
* bytes.
* \param offset_secret The offset in the source buffer from which to copy.
* This must be no less than \p offset_min and no greater
* than \p offset_max.
* \param offset_min The minimal value of \p offset_secret.
* \param offset_max The maximal value of \p offset_secret.
* \param len The number of bytes to copy.
*/
void mbedtls_cf_memcpy_offset( unsigned char *dst,
const unsigned char *src_base,
size_t offset_secret,
size_t offset_min, size_t offset_max,
size_t len );
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
/** Compute the HMAC of variable-length data with constant flow.
*
* This function computes the HMAC of the concatenation of \p add_data and \p
* data, and does with a code flow and memory access pattern that does not
* depend on \p data_len_secret, but only on \p min_data_len and \p
* max_data_len. In particular, this function always reads exactly \p
* max_data_len bytes from \p data.
*
* \param ctx The HMAC context. It must have keys configured
* with mbedtls_md_hmac_starts() and use one of the
* following hashes: SHA-384, SHA-256, SHA-1 or MD-5.
* It is reset using mbedtls_md_hmac_reset() after
* the computation is complete to prepare for the
* next computation.
* \param add_data The additional data prepended to \p data. This
* must point to a readable buffer of \p add_data_len
* bytes.
* \param add_data_len The length of \p add_data in bytes.
* \param data The data appended to \p add_data. This must point
* to a readable buffer of \p max_data_len bytes.
* \param data_len_secret The length of the data to process in \p data.
* This must be no less than \p min_data_len and no
* greater than \p max_data_len.
* \param min_data_len The minimal length of \p data in bytes.
* \param max_data_len The maximal length of \p data in bytes.
* \param output The HMAC will be written here. This must point to
* a writable buffer of sufficient size to hold the
* HMAC value.
*
* \retval 0 on success.
* \retval MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED
* The hardware accelerator failed.
*/
int mbedtls_ssl_cf_hmac(
mbedtls_md_context_t *ctx,
const unsigned char *add_data, size_t add_data_len,
const unsigned char *data, size_t data_len_secret,
size_t min_data_len, size_t max_data_len,
unsigned char *output );
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC */