tests/src/bignum_helpers.c

/**
 * \file bignum_helpers.c
 *
 * \brief   This file contains the prototypes of helper functions for
 *          bignum-related testing.
 */

/*
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#define MBEDTLS_ALLOW_PRIVATE_ACCESS
#include <test/bignum_helpers.h>

#if defined(MBEDTLS_BIGNUM_C)

#include <stdlib.h>
#include <string.h>

#include <mbedtls/bignum.h>
#include <bignum_core.h>
#include <bignum_mod.h>
#include <bignum_mod_raw.h>

#include <test/helpers.h>
#include <test/macros.h>

int mbedtls_test_read_mpi_core( mbedtls_mpi_uint **pX, size_t *plimbs,
                                const char *input )
{
    /* Sanity check */
    if( *pX != NULL )
        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );

    size_t hex_len = strlen( input );
    size_t byte_len = ( hex_len + 1 ) / 2;
    *plimbs = CHARS_TO_LIMBS( byte_len );

    /* A core bignum is not allowed to be empty. Forbid it as test data,
     * this way static analyzers have a chance of knowing we don't expect
     * the bignum functions to support empty inputs. */
    if( *plimbs == 0 )
        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );

    *pX = mbedtls_calloc( *plimbs, sizeof( **pX ) );
    if( *pX == NULL )
        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );

    unsigned char *byte_start = ( unsigned char * ) *pX;
    if( byte_len % sizeof( mbedtls_mpi_uint ) != 0 )
    {
        byte_start += sizeof( mbedtls_mpi_uint ) - byte_len % sizeof( mbedtls_mpi_uint );
    }
    if( ( hex_len & 1 ) != 0 )
    {
        /* mbedtls_test_unhexify wants an even number of hex digits */
        TEST_ASSERT( mbedtls_test_ascii2uc( *input, byte_start ) == 0 );
        ++byte_start;
        ++input;
        --byte_len;
    }
    TEST_ASSERT( mbedtls_test_unhexify( byte_start,
                                        byte_len,
                                        input,
                                        &byte_len ) == 0 );

    mbedtls_mpi_core_bigendian_to_host( *pX, *plimbs );
    return( 0 );

exit:
    mbedtls_free( *pX );
    return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
}

int mbedtls_test_read_mpi( mbedtls_mpi *X, const char *s )
{
    int negative = 0;
    /* Always set the sign bit to -1 if the input has a minus sign, even for 0.
     * This creates an invalid representation, which mbedtls_mpi_read_string()
     * avoids but we want to be able to create that in test data. */
    if( s[0] == '-' )
    {
        ++s;
        negative = 1;
    }
    /* mbedtls_mpi_read_string() currently retains leading zeros.
     * It always allocates at least one limb for the value 0. */
    if( s[0] == 0 )
    {
        mbedtls_mpi_free( X );
        return( 0 );
    }
    int ret = mbedtls_mpi_read_string( X, 16, s );
    if( ret != 0 )
        return( ret );
    if( negative )
    {
        if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
            ++mbedtls_test_case_uses_negative_0;
        X->s = -1;
    }
    return( 0 );
}

#endif /* MBEDTLS_BIGNUM_C */