library/psa_crypto_ecp.c

/*
 *  PSA ECP layer on top of Mbed TLS crypto
 */
/*
 *  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_PSA_CRYPTO_C)

#include <psa/crypto.h>
#include "psa_crypto_core.h"
#include "psa_crypto_ecp.h"

#include <stdlib.h>
#include <string.h>
#include "mbedtls/platform.h"
#if !defined(MBEDTLS_PLATFORM_C)
#define mbedtls_calloc calloc
#define mbedtls_free   free
#endif

#include <mbedtls/ecp.h>
#include <mbedtls/error.h>

#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR) || \
    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_PUBLIC_KEY) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA)
psa_status_t mbedtls_psa_ecp_load_representation(
    psa_key_type_t type, const uint8_t *data, size_t data_length,
    mbedtls_ecp_keypair **p_ecp )
{
    mbedtls_ecp_group_id grp_id = MBEDTLS_ECP_DP_NONE;
    psa_status_t status;
    mbedtls_ecp_keypair *ecp = NULL;
    size_t curve_size = data_length;

    if( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) &&
        PSA_KEY_TYPE_ECC_GET_FAMILY( type ) != PSA_ECC_FAMILY_MONTGOMERY )
    {
        /* A Weierstrass public key is represented as:
         * - The byte 0x04;
         * - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
         * - `y_P` as a `ceiling(m/8)`-byte string, big-endian.
         * So its data length is 2m+1 where m is the curve size in bits.
         */
        if( ( data_length & 1 ) == 0 )
            return( PSA_ERROR_INVALID_ARGUMENT );
        curve_size = data_length / 2;

        /* Montgomery public keys are represented in compressed format, meaning
         * their curve_size is equal to the amount of input. */

        /* Private keys are represented in uncompressed private random integer
         * format, meaning their curve_size is equal to the amount of input. */
    }

    /* Allocate and initialize a key representation. */
    ecp = mbedtls_calloc( 1, sizeof( mbedtls_ecp_keypair ) );
    if( ecp == NULL )
        return( PSA_ERROR_INSUFFICIENT_MEMORY );
    mbedtls_ecp_keypair_init( ecp );

    /* Load the group. */
    grp_id = mbedtls_ecc_group_of_psa( PSA_KEY_TYPE_ECC_GET_FAMILY( type ),
                                       curve_size );
    if( grp_id == MBEDTLS_ECP_DP_NONE )
    {
        status = PSA_ERROR_INVALID_ARGUMENT;
        goto exit;
    }

    status = mbedtls_to_psa_error(
                mbedtls_ecp_group_load( &ecp->grp, grp_id ) );
    if( status != PSA_SUCCESS )
        goto exit;

    /* Load the key material. */
    if( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) )
    {
        /* Load the public value. */
        status = mbedtls_to_psa_error(
            mbedtls_ecp_point_read_binary( &ecp->grp, &ecp->Q,
                                           data,
                                           data_length ) );
        if( status != PSA_SUCCESS )
            goto exit;

        /* Check that the point is on the curve. */
        status = mbedtls_to_psa_error(
            mbedtls_ecp_check_pubkey( &ecp->grp, &ecp->Q ) );
        if( status != PSA_SUCCESS )
            goto exit;
    }
    else
    {
        /* Load and validate the secret value. */
        status = mbedtls_to_psa_error(
            mbedtls_ecp_read_key( ecp->grp.id,
                                  ecp,
                                  data,
                                  data_length ) );
        if( status != PSA_SUCCESS )
            goto exit;
    }

    *p_ecp = ecp;
exit:
    if( status != PSA_SUCCESS )
    {
        mbedtls_ecp_keypair_free( ecp );
        mbedtls_free( ecp );
    }

    return( status );
}
#endif /* defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR) ||
        * defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_PUBLIC_KEY) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) */

#endif /* MBEDTLS_PSA_CRYPTO_C */