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Add mbedtls_ct_error_if, with tests

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman
2023-09-22 09:43:49 +01:00
parent 9d0869140b
commit fbe74a9e51
4 changed files with 157 additions and 1 deletions
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12
library/constant_time_impl.h
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@ -331,7 +331,6 @@ static inline unsigned char mbedtls_ct_uchar_in_range_if(unsigned char low,
return (unsigned char) (~(low_mask | high_mask)) & to;
}
/* ============================================================================
* Everything below here is trivial wrapper functions
*/
@ -397,6 +396,17 @@ static inline mbedtls_mpi_uint mbedtls_ct_mpi_uint_if_else_0(mbedtls_ct_conditio
#endif /* MBEDTLS_BIGNUM_C */
static inline int mbedtls_ct_error_if(mbedtls_ct_condition_t condition, int if1, int if0)
{
return -((int) mbedtls_ct_if(condition, (mbedtls_ct_uint_t) (-if1),
(mbedtls_ct_uint_t) (-if0)));
}
static inline int mbedtls_ct_error_if_else_0(mbedtls_ct_condition_t condition, int if1)
{
return -((int) (condition & (-if1)));
}
static inline mbedtls_ct_condition_t mbedtls_ct_uint_eq(mbedtls_ct_uint_t x,
mbedtls_ct_uint_t y)
{

29
library/constant_time_internal.h
View File

@ -411,6 +411,35 @@ static inline unsigned char mbedtls_ct_uchar_in_range_if(unsigned char low,
unsigned char c,
unsigned char t);
/** Choose between two error values. The values must be in the range [-32767..0].
*
* Functionally equivalent to:
*
* condition ? if1 : if0.
*
* \param condition Condition to test.
* \param if1 Value to use if \p condition == MBEDTLS_CT_TRUE.
* \param if0 Value to use if \p condition == MBEDTLS_CT_FALSE.
*
* \return \c if1 if \p condition == MBEDTLS_CT_TRUE, otherwise \c if0.
*/
static inline int mbedtls_ct_error_if(mbedtls_ct_condition_t condition, int if1, int if0);
/** Choose between an error value and 0. The error value must be in the range [-32767..0].
*
* Functionally equivalent to:
*
* condition ? if1 : 0.
*
* Functionally equivalent to mbedtls_ct_error_if(condition, if1, 0) but
* results in smaller code size.
*
* \param condition Condition to test.
* \param if1 Value to use if \p condition == MBEDTLS_CT_TRUE.
*
* \return \c if1 if \p condition == MBEDTLS_CT_TRUE, otherwise 0.
*/
static inline int mbedtls_ct_error_if_else_0(mbedtls_ct_condition_t condition, int if1);
/* ============================================================================
* Block memory operations