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Implement mbedtls_mpi_mod_sub()

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Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
Tom Cosgrove 2022-12-01 14:27:37 +00:00
parent c3902ac661
commit 62b20488f1
5 changed files with 218 additions and 1 deletions
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11
library/bignum_mod.c
View file

@ -179,7 +179,18 @@ exit:
/* END MERGE SLOT 2 */
/* BEGIN MERGE SLOT 3 */
int mbedtls_mpi_mod_sub( mbedtls_mpi_mod_residue *X,
const mbedtls_mpi_mod_residue *A,
const mbedtls_mpi_mod_residue *B,
const mbedtls_mpi_mod_modulus *N )
{
if( X->limbs != N->limbs || A->limbs != N->limbs || B->limbs != N->limbs )
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
mbedtls_mpi_mod_raw_sub( X->p, A->p, B->p, N );
return( 0 );
}
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */

30
library/bignum_mod.h
View file

@ -163,7 +163,35 @@ void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m );
/* END MERGE SLOT 2 */
/* BEGIN MERGE SLOT 3 */
/**
* \brief Perform a fixed-size modular subtraction.
*
* Calculate `A - B modulo N`.
*
* \p A, \p B and \p X must all have the same number of limbs as \p N.
*
* \p X may be aliased to \p A or \p B, or even both, but may not overlap
* either otherwise.
*
* \note This function does not check that \p A or \p B are in canonical
* form (that is, are < \p N) - that will have been done by
* mbedtls_mpi_mod_residue_setup().
*
* \param[out] X The address of the result MPI. Must be initialized.
* Must have the same number of limbs as the modulus \p N.
* \param[in] A The address of the first MPI.
* \param[in] B The address of the second MPI.
* \param[in] N The address of the modulus. Used to perform a modulo
* operation on the result of the subtraction.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the given MPIs do not
* have the correct number of limbs.
*/
int mbedtls_mpi_mod_sub( mbedtls_mpi_mod_residue *X,
const mbedtls_mpi_mod_residue *A,
const mbedtls_mpi_mod_residue *B,
const mbedtls_mpi_mod_modulus *N );
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */

19
scripts/mbedtls_dev/bignum_mod.py
View file

@ -34,6 +34,25 @@ class BignumModTarget(test_data_generation.BaseTarget):
# BEGIN MERGE SLOT 3
class BignumModSub(bignum_common.ModOperationCommon, BignumModTarget):
"""Test cases for bignum mpi_mod_sub()."""
symbol = "-"
test_function = "mpi_mod_sub"
test_name = "mbedtls_mpi_mod_sub"
input_style = "fixed"
arity = 2
# To make negative tests easier, append 0 for success to the generated cases
def arguments(self) -> List[str]:
return [bignum_common.quote_str(n) for n in [self.arg_n,
self.arg_a,
self.arg_b]
] + self.result() + ["0"]
def result(self) -> List[str]:
result = (self.int_a - self.int_b) % self.int_n
return [self.format_result(result)]
# END MERGE SLOT 3
# BEGIN MERGE SLOT 4

21
tests/suites/test_suite_bignum_mod.data
View file

@ -17,6 +17,27 @@ mpi_mod_setup:MBEDTLS_MPI_MOD_REP_MONTGOMERY:0
# BEGIN MERGE SLOT 3
mpi_mod_sub base case for negative testing (N, a, b all >= 1 limb)
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"000000025a55a46e5da99c71c7":"00033b2e3c9fd0803ce8000f93":"013fe57440828b4a0008aa4159":0
mpi_mod_sub with modulus too long/both inputs too short
mpi_mod_sub:"0000000014320a022ccb75bdf470ddf25":"000000025a55a46e5da99c71c7":"00033b2e3c9fd0803ce8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
mpi_mod_sub with first input too long
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"0000000000000025a55a46e5da99c71c7":"00033b2e3c9fd0803ce8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
mpi_mod_sub with second input too long
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"000000025a55a46e5da99c71c7":"000000000033b2e3c9fd0803ce8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
mpi_mod_sub with both inputs too long
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"0000000000000025a55a46e5da99c71c7":"000000000033b2e3c9fd0803ce8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
mpi_mod_sub with first input too short
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"a99c71c7":"00033b2e3c9fd0803ce8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
mpi_mod_sub with second input too short
mpi_mod_sub:"014320a022ccb75bdf470ddf25":"000000025a55a46e5da99c71c7":"e8000f93":"00":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
# END MERGE SLOT 3
# BEGIN MERGE SLOT 4

138
tests/suites/test_suite_bignum_mod.function
View file

@ -4,6 +4,47 @@
#include "bignum_mod.h"
#include "constant_time_internal.h"
#include "test/constant_flow.h"
#define TEST_COMPARE_MPI_RESIDUES( a, b ) \
ASSERT_COMPARE( (a).p, (a).limbs * sizeof(mbedtls_mpi_uint), \
(b).p, (b).limbs * sizeof(mbedtls_mpi_uint) )
int test_read_modulus( mbedtls_mpi_mod_modulus *m,
mbedtls_mpi_mod_rep_selector int_rep,
char *input )
{
mbedtls_mpi_uint *p = NULL;
size_t limbs;
int ret = mbedtls_test_read_mpi_core( &p, &limbs, input );
if( ret != 0 )
return( ret );
return( mbedtls_mpi_mod_modulus_setup( m, p, limbs, int_rep ) );
}
int test_read_residue( mbedtls_mpi_mod_residue *r,
const mbedtls_mpi_mod_modulus *m,
char *input,
int skip_limbs_and_value_checks )
{
mbedtls_mpi_uint *p = NULL;
size_t limbs;
int ret = mbedtls_test_read_mpi_core( &p, &limbs, input );
if( ret != 0 )
return( ret );
if( skip_limbs_and_value_checks )
{
r->p = p;
r->limbs = limbs;
return( 0 );
}
/* mbedtls_mpi_mod_residue_setup() checks limbs, and that value < m */
return( mbedtls_mpi_mod_residue_setup( r, m, p, limbs ) );
}
/* END_HEADER */
/* BEGIN_DEPENDENCIES
@ -64,7 +105,104 @@ exit:
/* END MERGE SLOT 2 */
/* BEGIN MERGE SLOT 3 */
/* BEGIN_CASE */
void mpi_mod_sub( char * input_N,
char * input_A, char * input_B,
char * input_D, int oret )
{
mbedtls_mpi_mod_residue a = { NULL, 0 };
mbedtls_mpi_mod_residue b = { NULL, 0 };
mbedtls_mpi_mod_residue d = { NULL, 0 };
mbedtls_mpi_mod_residue x = { NULL, 0 };
mbedtls_mpi_uint *X_raw = NULL;
mbedtls_mpi_mod_modulus m;
mbedtls_mpi_mod_modulus_init( &m );
TEST_EQUAL( 0,
test_read_modulus( &m, MBEDTLS_MPI_MOD_REP_MONTGOMERY, input_N ) );
/* test_read_residue() normally checks that inputs have the same number of
* limbs as the modulus. For negative testing we can ask it to skip this
* with a non-zero final parameter. */
TEST_EQUAL( 0, test_read_residue( &a, &m, input_A, oret != 0 ) );
TEST_EQUAL( 0, test_read_residue( &b, &m, input_B, oret != 0 ) );
TEST_EQUAL( 0, test_read_residue( &d, &m, input_D, oret != 0 ) );
size_t limbs = m.limbs;
size_t bytes = limbs * sizeof( *X_raw );
/* One spare limb for negative testing */
ASSERT_ALLOC( X_raw, limbs + 1 );
if( oret == 0 )
{
/* Sneak in a couple of negative tests on known-good data */
/* First, negative test with too many limbs in output */
x.p = X_raw;
x.limbs = limbs + 1;
TEST_EQUAL( MBEDTLS_ERR_MPI_BAD_INPUT_DATA,
mbedtls_mpi_mod_sub( &x, &a, &b, &m ) );
/* Then negative test with too few limbs in output */
if( limbs > 1 )
{
x.p = X_raw;
x.limbs = limbs - 1;
TEST_EQUAL( MBEDTLS_ERR_MPI_BAD_INPUT_DATA,
mbedtls_mpi_mod_sub( &x, &a, &b, &m ) );
}
/* Negative testing with too many/too few limbs in a and b is covered by
* manually-written test cases with oret != 0. */
/* Back to the normally-scheduled programme */
}
TEST_EQUAL( 0, mbedtls_mpi_mod_residue_setup( &x, &m, X_raw, limbs ) );
/* a - b => Correct result, or expected error */
TEST_EQUAL( oret, mbedtls_mpi_mod_sub( &x, &a, &b, &m ) );
if( oret != 0 )
goto exit;
TEST_COMPARE_MPI_RESIDUES( x, d );
/* a - b: alias x to a => Correct result */
memcpy( x.p, a.p, bytes );
TEST_EQUAL( 0, mbedtls_mpi_mod_sub( &x, &x, &b, &m ) );
TEST_COMPARE_MPI_RESIDUES( x, d );
/* a - b: alias x to b => Correct result */
memcpy( x.p, b.p, bytes );
TEST_EQUAL( 0, mbedtls_mpi_mod_sub( &x, &a, &x, &m ) );
TEST_COMPARE_MPI_RESIDUES( x, d );
if ( memcmp( a.p, b.p, bytes ) == 0 )
{
/* a == b: alias a and b */
/* a - a => Correct result */
TEST_EQUAL( 0, mbedtls_mpi_mod_sub( &x, &a, &a, &m ) );
TEST_COMPARE_MPI_RESIDUES( x, d );
/* a - a: x, a, b all aliased together => Correct result */
memcpy( x.p, a.p, bytes );
TEST_EQUAL( 0, mbedtls_mpi_mod_sub( &x, &x, &x, &m ) );
TEST_COMPARE_MPI_RESIDUES( x, d );
}
exit:
mbedtls_free( (void *)m.p ); /* mbedtls_mpi_mod_modulus_free() sets m.p = NULL */
mbedtls_mpi_mod_modulus_free( &m );
mbedtls_free( a.p );
mbedtls_free( b.p );
mbedtls_free( d.p );
mbedtls_free( X_raw );
}
/* END_CASE */
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */