library/bignum_mod_raw.c

/*
 *  Low-level modular bignum functions
 *
 *  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.
 */

#include "common.h"

#if defined(MBEDTLS_BIGNUM_C)

#include <string.h>

#include "mbedtls/error.h"
#include "mbedtls/platform_util.h"

#include "mbedtls/platform.h"

#include "bignum_core.h"
#include "bignum_mod_raw.h"
#include "bignum_mod.h"
#include "constant_time_internal.h"

void mbedtls_mpi_mod_raw_cond_assign( mbedtls_mpi_uint *X,
                                      const mbedtls_mpi_uint *A,
                                      const mbedtls_mpi_mod_modulus *N,
                                      unsigned char assign )
{
    mbedtls_mpi_core_cond_assign( X, A, N->limbs, assign );
}

void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
                                    mbedtls_mpi_uint *Y,
                                    const mbedtls_mpi_mod_modulus *N,
                                    unsigned char swap )
{
    mbedtls_mpi_core_cond_swap( X, Y, N->limbs, swap );
}

int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
                              const mbedtls_mpi_mod_modulus *m,
                              const unsigned char *input,
                              size_t input_length,
                              mbedtls_mpi_mod_ext_rep ext_rep )
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    switch( ext_rep )
    {
        case MBEDTLS_MPI_MOD_EXT_REP_LE:
            ret = mbedtls_mpi_core_read_le( X, m->limbs,
                                            input, input_length );
            break;
        case MBEDTLS_MPI_MOD_EXT_REP_BE:
            ret = mbedtls_mpi_core_read_be( X, m->limbs,
                                            input, input_length );
            break;
        default:
            return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
    }

    if( ret != 0 )
        goto cleanup;

    if( !mbedtls_mpi_core_lt_ct( X, m->p, m->limbs ) )
    {
        ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
        goto cleanup;
    }

cleanup:

    return( ret );
}

int mbedtls_mpi_mod_raw_write( const mbedtls_mpi_uint *A,
                               const mbedtls_mpi_mod_modulus *m,
                               unsigned char *output,
                               size_t output_length,
                               mbedtls_mpi_mod_ext_rep ext_rep )
{
    switch( ext_rep )
    {
        case MBEDTLS_MPI_MOD_EXT_REP_LE:
            return( mbedtls_mpi_core_write_le( A, m->limbs,
                                               output, output_length ) );
        case MBEDTLS_MPI_MOD_EXT_REP_BE:
            return( mbedtls_mpi_core_write_be( A, m->limbs,
                                               output, output_length ) );
        default:
            return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
    }
}

/* BEGIN MERGE SLOT 1 */

/* END MERGE SLOT 1 */

/* BEGIN MERGE SLOT 2 */

void mbedtls_mpi_mod_raw_sub( mbedtls_mpi_uint *X,
                              const mbedtls_mpi_uint *A,
                              const mbedtls_mpi_uint *B,
                              const mbedtls_mpi_mod_modulus *N )
{
    mbedtls_mpi_uint c = mbedtls_mpi_core_sub( X, A, B, N->limbs );

    (void) mbedtls_mpi_core_add_if( X, N->p, N->limbs, (unsigned) c );
}

/* END MERGE SLOT 2 */

/* BEGIN MERGE SLOT 3 */

size_t mbedtls_mpi_mod_raw_inv_prime_working_limbs( size_t AN_limbs )
{
    /* mbedtls_mpi_mod_raw_inv_prime() needs a temporary for the exponent,
     * which will be the same size as the modulus and input (AN_limbs),
     * and additional space to pass to mbedtls_mpi_core_exp_mod(). */
    return( AN_limbs +
            mbedtls_mpi_core_exp_mod_working_limbs( AN_limbs, AN_limbs ) );
}

void mbedtls_mpi_mod_raw_inv_prime( mbedtls_mpi_uint *X,
                                    const mbedtls_mpi_uint *A,
                                    const mbedtls_mpi_uint *N,
                                    size_t AN_limbs,
                                    const mbedtls_mpi_uint *RR,
                                    mbedtls_mpi_uint *T )
{
    /* Inversion by power: g^|G| = 1 => g^(-1) = g^(|G|-1), and
     *                       |G| = N - 1, so we want
     *                 g^(|G|-1) = g^(N - 2)
     */

    /* Use the first AN_limbs of T to hold N - 2 */
    mbedtls_mpi_uint *Nminus2 = T;
    (void) mbedtls_mpi_core_sub_int( Nminus2, N, 2, AN_limbs );

    /* Rest of T is given to exp_mod for its working space */
    mbedtls_mpi_core_exp_mod( X,
                              A, N, AN_limbs, Nminus2, AN_limbs,
                              RR, T + AN_limbs );
}

/* END MERGE SLOT 3 */

/* BEGIN MERGE SLOT 4 */

/* END MERGE SLOT 4 */

/* BEGIN MERGE SLOT 5 */
void mbedtls_mpi_mod_raw_add( mbedtls_mpi_uint *X,
                              const mbedtls_mpi_uint *A,
                              const mbedtls_mpi_uint *B,
                              const mbedtls_mpi_mod_modulus *N )
{
    mbedtls_mpi_uint carry, borrow;
    carry  = mbedtls_mpi_core_add( X, A, B, N->limbs );
    borrow = mbedtls_mpi_core_sub( X, X, N->p, N->limbs );
    (void) mbedtls_mpi_core_add_if( X, N->p, N->limbs, (unsigned) ( carry ^ borrow ) );
}
/* END MERGE SLOT 5 */

/* BEGIN MERGE SLOT 6 */

/* END MERGE SLOT 6 */

/* BEGIN MERGE SLOT 7 */
int mbedtls_mpi_mod_raw_to_mont_rep( mbedtls_mpi_uint *X,
                                     const mbedtls_mpi_mod_modulus *m )
{
    mbedtls_mpi_uint *T;
    const size_t t_limbs = mbedtls_mpi_core_montmul_working_limbs( m->limbs );

    if( ( T = (mbedtls_mpi_uint *) mbedtls_calloc( t_limbs, ciL ) ) == NULL )
        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );

    mbedtls_mpi_core_montmul( X, X, m->rep.mont.rr, m->limbs, m->p, m->limbs,
                              m->rep.mont.mm, T );

    mbedtls_platform_zeroize( T, t_limbs * ciL );
    mbedtls_free( T );
    return( 0 );
}

int mbedtls_mpi_mod_raw_from_mont_rep( mbedtls_mpi_uint *X,
                                       const mbedtls_mpi_mod_modulus *m )
{
    const mbedtls_mpi_uint one = 1;
    const size_t t_limbs = mbedtls_mpi_core_montmul_working_limbs( m->limbs );
    mbedtls_mpi_uint *T;

    if( ( T = (mbedtls_mpi_uint *) mbedtls_calloc( t_limbs, ciL ) ) == NULL )
        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );

    mbedtls_mpi_core_montmul( X, X, &one, 1, m->p, m->limbs,
                              m->rep.mont.mm, T );

    mbedtls_platform_zeroize( T, t_limbs * ciL );
    mbedtls_free( T );
    return( 0 );
}

void mbedtls_mpi_mod_raw_neg( mbedtls_mpi_uint *X,
                              const mbedtls_mpi_uint *A,
                              const mbedtls_mpi_mod_modulus *m )
{
    mbedtls_mpi_core_sub( X, m->p, A, m->limbs );

    /* If A=0 initially, then X=N now. Detect this by
     * subtracting N and catching the carry. */
    mbedtls_mpi_uint borrow = mbedtls_mpi_core_sub( X, X, m->p, m->limbs );
    (void) mbedtls_mpi_core_add_if( X, m->p, m->limbs, (unsigned) borrow  );
}
/* END MERGE SLOT 7 */

/* BEGIN MERGE SLOT 8 */

/* END MERGE SLOT 8 */

/* BEGIN MERGE SLOT 9 */

/* END MERGE SLOT 9 */

/* BEGIN MERGE SLOT 10 */

/* END MERGE SLOT 10 */

#endif /* MBEDTLS_BIGNUM_C */