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mpi_core_ct_uint_table_lookup: style and docs

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Signed-off-by: Janos Follath <janos.follath@arm.com>
This commit is contained in:
Janos Follath 2022-10-31 15:32:28 +00:00
parent ef67d38bc0
commit 8904a2db29
3 changed files with 12 additions and 15 deletions
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5
library/bignum_core.c
View file

@ -546,11 +546,10 @@ void mbedtls_mpi_core_ct_uint_table_lookup( mbedtls_mpi_uint *dest,
size_t count, size_t count,
size_t index ) size_t index )
{ {
for( size_t i = 0; i < count; i++ ) for( size_t i = 0; i < count; i++, table += limbs )
{ {
unsigned char assign = mbedtls_ct_size_bool_eq( i, index ); unsigned char assign = mbedtls_ct_size_bool_eq( i, index );
const mbedtls_mpi_uint *current = table + i * limbs; mbedtls_mpi_core_cond_assign( dest, table, limbs, assign );
mbedtls_mpi_core_cond_assign( dest, current, limbs, assign );
} }
} }

13
library/bignum_core.h
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@ -453,17 +453,16 @@ int mbedtls_mpi_core_get_mont_r2_unsafe( mbedtls_mpi *X,
const mbedtls_mpi *N ); const mbedtls_mpi *N );
/** /**
* Select an MPI from a table without leaking the index. * Copy an MPI from a table without leaking the index.
* *
* \param dest The destination buffer. This must point to a writable * \param dest The destination buffer. This must point to a writable
* buffer of at least \p limbs limbs. * buffer of at least \p limbs limbs.
* \param table The address of the table. This must point to a readable * \param table The address of the table. This must point to a readable
* array of \p count elements of * array of \p count elements of \p limbs limbs each.
* \p limbs limbs each each. * \param limbs The number of limbs in each table entry.
* \param limbs The length of a table entry in limbs. * \param count The number of entries in \p table.
* \param count The number of elements in \p table. * \param index The (secret) table index to look up. This must be in the
* \param index The secret table index to look up. This must be in the * range `0 .. count-1`.
* range `0,..,count-1`.
*/ */
void mbedtls_mpi_core_ct_uint_table_lookup( mbedtls_mpi_uint *dest, void mbedtls_mpi_core_ct_uint_table_lookup( mbedtls_mpi_uint *dest,
const mbedtls_mpi_uint *table, const mbedtls_mpi_uint *table,

1
scripts/mbedtls_dev/bignum_core.py
View file

@ -71,7 +71,6 @@ class BignumCoreShiftR(BignumCoreTarget, metaclass=ABCMeta):
class BignumCoreCTLookup(BignumCoreTarget, metaclass=ABCMeta): class BignumCoreCTLookup(BignumCoreTarget, metaclass=ABCMeta):
"""Test cases for mbedtls_mpi_core_ct_uint_table_lookup().""" """Test cases for mbedtls_mpi_core_ct_uint_table_lookup()."""
count = 0
test_function = "mpi_core_ct_uint_table_lookup" test_function = "mpi_core_ct_uint_table_lookup"
test_name = "Constant time MPI table lookup" test_name = "Constant time MPI table lookup"