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Use new CT interface in mbedtls_mpi_core_lt_ct

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-05-17 15:16:22 +01:00
parent 231a516682
commit 8ac9a1df24
2 changed files with 15 additions and 19 deletions
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22
library/bignum_core.c
View file

@ -166,15 +166,11 @@ mbedtls_ct_condition_t mbedtls_mpi_core_uint_le_mpi(mbedtls_mpi_uint min,
return mbedtls_ct_bool_or(msll_mask, min_le_lsl);
}
unsigned mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs)
mbedtls_ct_condition_t mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs)
{
unsigned ret, cond, done;
/* The value of any of these variables is either 0 or 1 for the rest of
* their scope. */
ret = cond = done = 0;
mbedtls_ct_condition_t ret = MBEDTLS_CT_FALSE, cond = MBEDTLS_CT_FALSE, done = MBEDTLS_CT_FALSE;
for (size_t i = limbs; i > 0; i--) {
/*
@ -184,8 +180,8 @@ unsigned mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
* Again even if we can make a decision, we just mark the result and
* the fact that we are done and continue looping.
*/
cond = mbedtls_ct_mpi_uint_lt(B[i - 1], A[i - 1]);
done |= cond;
cond = mbedtls_ct_bool_lt(B[i - 1], A[i - 1]);
done = mbedtls_ct_bool_or(done, cond);
/*
* If A[i - 1] < B[i - 1] then A < B is true.
@ -193,9 +189,9 @@ unsigned mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
* Again even if we can make a decision, we just mark the result and
* the fact that we are done and continue looping.
*/
cond = mbedtls_ct_mpi_uint_lt(A[i - 1], B[i - 1]);
ret |= cond & (1 - done);
done |= cond;
cond = mbedtls_ct_bool_lt(A[i - 1], B[i - 1]);
ret = mbedtls_ct_bool_or(ret, mbedtls_ct_bool_and(cond, mbedtls_ct_bool_not(done)));
done = mbedtls_ct_bool_or(done, cond);
}
/*

12
library/bignum_core.h
View file

@ -161,13 +161,13 @@ mbedtls_ct_condition_t mbedtls_mpi_core_uint_le_mpi(mbedtls_mpi_uint min,
* \param limbs The number of limbs in \p A and \p B.
* This must not be 0.
*
* \return The result of the comparison:
* \c 1 if \p A is less than \p B.
* \c 0 if \p A is greater than or equal to \p B.
* \return MBEDTLS_CT_TRUE if \p A is less than \p B.
* MBEDTLS_CT_FALSE if \p A is greater than or equal to \p B.
*/
unsigned mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs);
mbedtls_ct_condition_t mbedtls_mpi_core_lt_ct(const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs);
/**
* \brief Perform a safe conditional copy of an MPI which doesn't reveal
* whether assignment was done or not.