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Document and test mbedtls_ct_size_if_else_0

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-08-10 12:13:27 +01:00
parent 065f912465
commit ac69b45486
2 changed files with 17 additions and 0 deletions
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16
library/constant_time_internal.h
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@ -325,6 +325,22 @@ static inline mbedtls_mpi_uint mbedtls_ct_mpi_uint_if(mbedtls_ct_condition_t con
*/
static inline unsigned mbedtls_ct_uint_if_else_0(mbedtls_ct_condition_t condition, unsigned if1);
/** Choose between an unsigned value and 0.
*
* Functionally equivalent to:
*
* condition ? if1 : 0.
*
* Functionally equivalent to mbedtls_ct_size_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 size_t mbedtls_ct_size_if_else_0(mbedtls_ct_condition_t condition, size_t if1);
#if defined(MBEDTLS_BIGNUM_C)
/** Choose between an mbedtls_mpi_uint value and 0.

1
tests/suites/test_suite_constant_time.function
View file

@ -136,6 +136,7 @@ void mbedtls_ct_if(char *c_str, char *t_str, char *f_str)
#endif
TEST_EQUAL(mbedtls_ct_uint_if_else_0(c, t), (unsigned) expected0);
TEST_EQUAL(mbedtls_ct_size_if_else_0(c, (size_t) t), (size_t) expected0);
#if defined(MBEDTLS_BIGNUM_C)
TEST_EQUAL(mbedtls_ct_mpi_uint_if_else_0(c, t), (mbedtls_mpi_uint) expected0);
#endif