56e5d6887f
Co-authored-by: Tom Cosgrove <tom.cosgrove@arm.com> Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
48 lines
1.7 KiB
C
48 lines
1.7 KiB
C
/**
|
|
* 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.
|
|
*/
|
|
|
|
#ifndef MBEDTLS_CONSTANT_TIME_H
|
|
#define MBEDTLS_CONSTANT_TIME_H
|
|
|
|
#include <stddef.h>
|
|
|
|
/** Constant-time buffer comparison without branches.
|
|
*
|
|
* This is equivalent to the standard memcmp function, but is likely to be
|
|
* compiled to code using bitwise operations rather than a branch, such that
|
|
* the time taken is constant w.r.t. the data pointed to by \p a and \p b,
|
|
* and w.r.t. whether \p a and \p b are equal or not. It is not constant-time
|
|
* w.r.t. \p n .
|
|
*
|
|
* This function can be used to write constant-time code by replacing branches
|
|
* with bit operations using masks.
|
|
*
|
|
* \param a Pointer to the first buffer, containing at least \p n bytes. May not be NULL.
|
|
* \param b Pointer to the second buffer, containing at least \p n bytes. May not be NULL.
|
|
* \param n The number of bytes to compare.
|
|
*
|
|
* \return Zero if the contents of the two buffers are the same,
|
|
* otherwise non-zero.
|
|
*/
|
|
int mbedtls_ct_memcmp(const void *a,
|
|
const void *b,
|
|
size_t n);
|
|
|
|
#endif /* MBEDTLS_CONSTANT_TIME_H */
|