305 lines
12 KiB
C
305 lines
12 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_INTERNAL_H
|
|
#define MBEDTLS_CONSTANT_TIME_INTERNAL_H
|
|
|
|
#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>
|
|
|
|
|
|
/** Turn a value into a mask:
|
|
* - if \p value == 0, return the all-bits 0 mask, aka 0
|
|
* - otherwise, return the all-bits 1 mask, aka (unsigned) -1
|
|
*
|
|
* This function can be used to write constant-time code by replacing branches
|
|
* with bit operations using masks.
|
|
*
|
|
* \param value The value to analyze.
|
|
*
|
|
* \return Zero if \p value is zero, otherwise all-bits-one.
|
|
*/
|
|
unsigned mbedtls_ct_uint_mask( unsigned value );
|
|
|
|
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
|
|
|
|
/** Turn a value into a mask:
|
|
* - if \p value == 0, return the all-bits 0 mask, aka 0
|
|
* - otherwise, return the all-bits 1 mask, aka (size_t) -1
|
|
*
|
|
* This function can be used to write constant-time code by replacing branches
|
|
* with bit operations using masks.
|
|
*
|
|
* \param value The value to analyze.
|
|
*
|
|
* \return Zero if \p value is zero, otherwise all-bits-one.
|
|
*/
|
|
size_t mbedtls_ct_size_mask( size_t value );
|
|
|
|
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC */
|
|
|
|
#if defined(MBEDTLS_BIGNUM_C)
|
|
|
|
/** Turn a value into a mask:
|
|
* - if \p value == 0, return the all-bits 0 mask, aka 0
|
|
* - otherwise, return the all-bits 1 mask, aka (mbedtls_mpi_uint) -1
|
|
*
|
|
* This function can be used to write constant-time code by replacing branches
|
|
* with bit operations using masks.
|
|
*
|
|
* \param value The value to analyze.
|
|
*
|
|
* \return Zero if \p value is zero, otherwise all-bits-one.
|
|
*/
|
|
mbedtls_mpi_uint mbedtls_ct_mpi_uint_mask( mbedtls_mpi_uint value );
|
|
|
|
#endif /* MBEDTLS_BIGNUM_C */
|
|
|
|
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
|
|
|
|
/** Constant-flow mask generation for "greater or equal" comparison:
|
|
* - if \p x >= \p y, return all-bits 1, that is (size_t) -1
|
|
* - otherwise, return all bits 0, that is 0
|
|
*
|
|
* This function can be used to write constant-time code by replacing branches
|
|
* with bit operations using masks.
|
|
*
|
|
* \param x The first value to analyze.
|
|
* \param y The second value to analyze.
|
|
*
|
|
* \return All-bits-one if \p x is greater or equal than \p y,
|
|
* otherwise zero.
|
|
*/
|
|
size_t mbedtls_ct_size_mask_ge( size_t x,
|
|
size_t y );
|
|
|
|
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC */
|
|
|
|
/** Constant-flow boolean "equal" comparison:
|
|
* return x == y
|
|
*
|
|
* This is equivalent to \p x == \p y, but is likely to be compiled
|
|
* to code using bitwise operation rather than a branch.
|
|
*
|
|
* \param x The first value to analyze.
|
|
* \param y The second value to analyze.
|
|
*
|
|
* \return 1 if \p x equals to \p y, otherwise 0.
|
|
*/
|
|
unsigned mbedtls_ct_size_bool_eq( size_t x,
|
|
size_t y );
|
|
|
|
#if defined(MBEDTLS_BIGNUM_C)
|
|
|
|
/** Decide if an integer is less than the other, without branches.
|
|
*
|
|
* This is equivalent to \p x < \p y, but is likely to be compiled
|
|
* to code using bitwise operation rather than a branch.
|
|
*
|
|
* \param x The first value to analyze.
|
|
* \param y The second value to analyze.
|
|
*
|
|
* \return 1 if \p x is less than \p y, otherwise 0.
|
|
*/
|
|
unsigned mbedtls_ct_mpi_uint_lt( const mbedtls_mpi_uint x,
|
|
const mbedtls_mpi_uint y );
|
|
|
|
#endif /* MBEDTLS_BIGNUM_C */
|
|
|
|
/** Choose between two integer values without branches.
|
|
*
|
|
* This is equivalent to `condition ? if1 : if0`, but is likely to be compiled
|
|
* to code using bitwise operation rather than a branch.
|
|
*
|
|
* \param condition Condition to test.
|
|
* \param if1 Value to use if \p condition is nonzero.
|
|
* \param if0 Value to use if \p condition is zero.
|
|
*
|
|
* \return \c if1 if \p condition is nonzero, otherwise \c if0.
|
|
*/
|
|
unsigned mbedtls_ct_uint_if( unsigned condition,
|
|
unsigned if1,
|
|
unsigned if0 );
|
|
|
|
#if defined(MBEDTLS_BIGNUM_C)
|
|
|
|
/** Conditionally assign a value without branches.
|
|
*
|
|
* This is equivalent to `if ( condition ) dest = src`, but is likely
|
|
* to be compiled to code using bitwise operation rather than a branch.
|
|
*
|
|
* \param n \p dest and \p src must be arrays of limbs of size n.
|
|
* \param dest The MPI to conditionally assign to. This must point
|
|
* to an initialized MPI.
|
|
* \param src The MPI to be assigned from. This must point to an
|
|
* initialized MPI.
|
|
* \param condition Condition to test, must be 0 or 1.
|
|
*/
|
|
void mbedtls_ct_mpi_uint_cond_assign( size_t n,
|
|
mbedtls_mpi_uint *dest,
|
|
const mbedtls_mpi_uint *src,
|
|
unsigned char condition );
|
|
|
|
#endif /* MBEDTLS_BIGNUM_C */
|
|
|
|
#if defined(MBEDTLS_BASE64_C)
|
|
|
|
unsigned char mbedtls_ct_base64_enc_char( unsigned char val );
|
|
|
|
signed char mbedtls_ct_base64_dec_value( unsigned char c );
|
|
|
|
#endif /* MBEDTLS_BASE64_C */
|
|
|
|
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
|
|
|
|
/** Conditional memcpy without branches.
|
|
*
|
|
* This is equivalent to `if ( c1 == c2 ) memcpy(dest, src, len)`, but is likely
|
|
* to be compiled to code using bitwise operation rather than a branch.
|
|
*
|
|
* \param dest The pointer to conditionally copy to.
|
|
* \param src The pointer to copy from. Shouldn't overlap with \p dest.
|
|
* \param len The number of bytes to copy.
|
|
* \param c1 The first value to analyze in the condition.
|
|
* \param c2 The second value to analyze in the condition.
|
|
*/
|
|
void mbedtls_ct_memcpy_if_eq( unsigned char *dest,
|
|
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.
|
|
* Functionally equivalent to `memcpy(dst, src + offset_secret, len)`.
|
|
*
|
|
* \param dest The destination buffer. This must point to a writable
|
|
* buffer of at least \p len bytes.
|
|
* \param src The base of the source buffer. This must point to a
|
|
* readable buffer of at least \p offset_max + \p len
|
|
* bytes. Shouldn't overlap with \p dest.
|
|
* \param offset 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.
|
|
* \param offset_max The maximal value of \p offset.
|
|
* \param len The number of bytes to copy.
|
|
*/
|
|
void mbedtls_ct_memcpy_offset( unsigned char *dest,
|
|
const unsigned char *src,
|
|
size_t offset,
|
|
size_t offset_min,
|
|
size_t offset_max,
|
|
size_t len );
|
|
|
|
/** 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 first part of the message whose HMAC is being
|
|
* calculated. 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 buffer containing the second part of the
|
|
* message. 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 the second part of the
|
|
* message, read from \p data.
|
|
* \param max_data_len The maximal length of the second part of the
|
|
* message, read from \p data.
|
|
* \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_ct_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 */
|
|
|
|
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
|
|
|
|
/** This function performs the unpadding part of a PKCS#1 v1.5 decryption
|
|
* operation (EME-PKCS1-v1_5 decoding).
|
|
*
|
|
* \note The return value from this function is a sensitive value
|
|
* (this is unusual). #MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE shouldn't happen
|
|
* in a well-written application, but 0 vs #MBEDTLS_ERR_RSA_INVALID_PADDING
|
|
* is often a situation that an attacker can provoke and leaking which
|
|
* one is the result is precisely the information the attacker wants.
|
|
*
|
|
* \param input The input buffer which is the payload inside PKCS#1v1.5
|
|
* encryption padding, called the "encoded message EM"
|
|
* by the terminology.
|
|
* \param ilen The length of the payload in the \p input buffer.
|
|
* \param output The buffer for the payload, called "message M" by the
|
|
* PKCS#1 terminology. This must be a writable buffer of
|
|
* length \p output_max_len bytes.
|
|
* \param olen The address at which to store the length of
|
|
* the payload. This must not be \c NULL.
|
|
* \param output_max_len The length in bytes of the output buffer \p output.
|
|
*
|
|
* \return \c 0 on success.
|
|
* \return #MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE
|
|
* The output buffer is too small for the unpadded payload.
|
|
* \return #MBEDTLS_ERR_RSA_INVALID_PADDING
|
|
* The input doesn't contain properly formatted padding.
|
|
*/
|
|
int mbedtls_ct_rsaes_pkcs1_v15_unpadding( unsigned char *input,
|
|
size_t ilen,
|
|
unsigned char *output,
|
|
size_t output_max_len,
|
|
size_t *olen );
|
|
|
|
#endif /* MBEDTLS_PKCS1_V15 && MBEDTLS_RSA_C && ! MBEDTLS_RSA_ALT */
|
|
|
|
#endif /* MBEDTLS_CONSTANT_TIME_INTERNAL_H */
|