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37 lines
1.2 KiB
C++
37 lines
1.2 KiB
C++
/**
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* Constant-time functions
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#ifndef MBEDTLS_CONSTANT_TIME_H
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#define MBEDTLS_CONSTANT_TIME_H
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#include <stddef.h>
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/** Constant-time buffer comparison without branches.
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*
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* This is equivalent to the standard memcmp function, but is likely to be
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* compiled to code using bitwise operations rather than a branch, such that
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* the time taken is constant w.r.t. the data pointed to by \p a and \p b,
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* and w.r.t. whether \p a and \p b are equal or not. It is not constant-time
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* w.r.t. \p n .
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*
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* This function can be used to write constant-time code by replacing branches
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* with bit operations using masks.
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*
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* \param a Pointer to the first buffer, containing at least \p n bytes. May not be NULL.
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* \param b Pointer to the second buffer, containing at least \p n bytes. May not be NULL.
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* \param n The number of bytes to compare.
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*
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* \return Zero if the contents of the two buffers are the same,
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* otherwise non-zero.
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*/
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int mbedtls_ct_memcmp(const void *a,
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const void *b,
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size_t n);
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#endif /* MBEDTLS_CONSTANT_TIME_H */
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