library/psa_crypto_rsa.c

/*
 *  PSA RSA 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_random_impl.h"
#include "psa_crypto_rsa.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/rsa.h>
#include <mbedtls/error.h>
#include <mbedtls/pk.h>
#include <mbedtls/pk_internal.h>

#if ( defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||  \
      ( defined(PSA_CRYPTO_DRIVER_TEST) &&                   \
        defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_KEY_PAIR) ) )
#define BUILTIN_KEY_TYPE_RSA_KEY_PAIR    1
#endif

#if ( defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) ||  \
      ( defined(PSA_CRYPTO_DRIVER_TEST) &&                   \
        defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_PUBLIC_KEY) ) )
#define BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY  1
#endif

#if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_CRYPT) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_OAEP) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS) || \
    defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR) || \
    defined(BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY)

/* Mbed TLS doesn't support non-byte-aligned key sizes (i.e. key sizes
 * that are not a multiple of 8) well. For example, there is only
 * mbedtls_rsa_get_len(), which returns a number of bytes, and no
 * way to return the exact bit size of a key.
 * To keep things simple, reject non-byte-aligned key sizes. */
static psa_status_t psa_check_rsa_key_byte_aligned(
    const mbedtls_rsa_context *rsa )
{
    mbedtls_mpi n;
    psa_status_t status;
    mbedtls_mpi_init( &n );
    status = mbedtls_to_psa_error(
        mbedtls_rsa_export( rsa, &n, NULL, NULL, NULL, NULL ) );
    if( status == PSA_SUCCESS )
    {
        if( mbedtls_mpi_bitlen( &n ) % 8 != 0 )
            status = PSA_ERROR_NOT_SUPPORTED;
    }
    mbedtls_mpi_free( &n );
    return( status );
}

psa_status_t mbedtls_psa_rsa_load_representation(
    psa_key_type_t type, const uint8_t *data, size_t data_length,
    mbedtls_rsa_context **p_rsa )
{
    psa_status_t status;
    mbedtls_pk_context ctx;
    size_t bits;
    mbedtls_pk_init( &ctx );

    /* Parse the data. */
    if( PSA_KEY_TYPE_IS_KEY_PAIR( type ) )
        status = mbedtls_to_psa_error(
            mbedtls_pk_parse_key( &ctx, data, data_length, NULL, 0 ) );
    else
        status = mbedtls_to_psa_error(
            mbedtls_pk_parse_public_key( &ctx, data, data_length ) );
    if( status != PSA_SUCCESS )
        goto exit;

    /* We have something that the pkparse module recognizes. If it is a
     * valid RSA key, store it. */
    if( mbedtls_pk_get_type( &ctx ) != MBEDTLS_PK_RSA )
    {
        status = PSA_ERROR_INVALID_ARGUMENT;
        goto exit;
    }

    /* The size of an RSA key doesn't have to be a multiple of 8. Mbed TLS
     * supports non-byte-aligned key sizes, but not well. For example,
     * mbedtls_rsa_get_len() returns the key size in bytes, not in bits. */
    bits = PSA_BYTES_TO_BITS( mbedtls_rsa_get_len( mbedtls_pk_rsa( ctx ) ) );
    if( bits > PSA_VENDOR_RSA_MAX_KEY_BITS )
    {
        status = PSA_ERROR_NOT_SUPPORTED;
        goto exit;
    }
    status = psa_check_rsa_key_byte_aligned( mbedtls_pk_rsa( ctx ) );
    if( status != PSA_SUCCESS )
        goto exit;

    /* Copy out the pointer to the RSA context, and reset the PK context
     * such that pk_free doesn't free the RSA context we just grabbed. */
    *p_rsa = mbedtls_pk_rsa( ctx );
    ctx.pk_info = NULL;

exit:
    mbedtls_pk_free( &ctx );
    return( status );
}
#endif /* defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_CRYPT) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_OAEP) ||
        * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS) ||
        * defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||
        * defined(BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) */

#if defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR) || \
    defined(BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY)

static psa_status_t rsa_import_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *data, size_t data_length,
    uint8_t *key_buffer, size_t key_buffer_size,
    size_t *key_buffer_length, size_t *bits )
{
    psa_status_t status;
    mbedtls_rsa_context *rsa = NULL;

    /* Parse input */
    status = mbedtls_psa_rsa_load_representation( attributes->core.type,
                                                  data,
                                                  data_length,
                                                  &rsa );
    if( status != PSA_SUCCESS )
        goto exit;

    *bits = (psa_key_bits_t) PSA_BYTES_TO_BITS( mbedtls_rsa_get_len( rsa ) );

    /* Re-export the data to PSA export format, such that we can store export
     * representation in the key slot. Export representation in case of RSA is
     * the smallest representation that's allowed as input, so a straight-up
     * allocation of the same size as the input buffer will be large enough. */
    status = mbedtls_psa_rsa_export_key( attributes->core.type,
                                         rsa,
                                         key_buffer,
                                         key_buffer_size,
                                         key_buffer_length );
exit:
    /* Always free the RSA object */
    mbedtls_rsa_free( rsa );
    mbedtls_free( rsa );

    return( status );
}

psa_status_t mbedtls_psa_rsa_export_key( psa_key_type_t type,
                                         mbedtls_rsa_context *rsa,
                                         uint8_t *data,
                                         size_t data_size,
                                         size_t *data_length )
{
#if defined(MBEDTLS_PK_WRITE_C)
    int ret;
    mbedtls_pk_context pk;
    uint8_t *pos = data + data_size;

    mbedtls_pk_init( &pk );
    pk.pk_info = &mbedtls_rsa_info;
    pk.pk_ctx = rsa;

    /* PSA Crypto API defines the format of an RSA key as a DER-encoded
     * representation of the non-encrypted PKCS#1 RSAPrivateKey for a
     * private key and of the RFC3279 RSAPublicKey for a public key. */
    if( PSA_KEY_TYPE_IS_KEY_PAIR( type ) )
        ret = mbedtls_pk_write_key_der( &pk, data, data_size );
    else
        ret = mbedtls_pk_write_pubkey( &pos, data, &pk );

    if( ret < 0 )
    {
        /* Clean up in case pk_write failed halfway through. */
        memset( data, 0, data_size );
        return( mbedtls_to_psa_error( ret ) );
    }

    /* The mbedtls_pk_xxx functions write to the end of the buffer.
     * Move the data to the beginning and erase remaining data
     * at the original location. */
    if( 2 * (size_t) ret <= data_size )
    {
        memcpy( data, data + data_size - ret, ret );
        memset( data + data_size - ret, 0, ret );
    }
    else if( (size_t) ret < data_size )
    {
        memmove( data, data + data_size - ret, ret );
        memset( data + ret, 0, data_size - ret );
    }

    *data_length = ret;
    return( PSA_SUCCESS );
#else
    (void) type;
    (void) rsa;
    (void) data;
    (void) data_size;
    (void) data_length;
    return( PSA_ERROR_NOT_SUPPORTED );
#endif /* MBEDTLS_PK_WRITE_C */
}

static psa_status_t rsa_export_public_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer, size_t key_buffer_size,
    uint8_t *data, size_t data_size, size_t *data_length )
{
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
    mbedtls_rsa_context *rsa = NULL;

    status = mbedtls_psa_rsa_load_representation(
                 attributes->core.type, key_buffer, key_buffer_size, &rsa );
    if( status != PSA_SUCCESS )
        return( status );

    status = mbedtls_psa_rsa_export_key( PSA_KEY_TYPE_RSA_PUBLIC_KEY,
                                         rsa,
                                         data,
                                         data_size,
                                         data_length );

    mbedtls_rsa_free( rsa );
    mbedtls_free( rsa );

    return( status );
}
#endif /* defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||
        * defined(BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) */

#if defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR)
static psa_status_t psa_read_rsa_exponent( const uint8_t *domain_parameters,
                                           size_t domain_parameters_size,
                                           int *exponent )
{
    size_t i;
    uint32_t acc = 0;

    if( domain_parameters_size == 0 )
    {
        *exponent = 65537;
        return( PSA_SUCCESS );
    }

    /* Mbed TLS encodes the public exponent as an int. For simplicity, only
     * support values that fit in a 32-bit integer, which is larger than
     * int on just about every platform anyway. */
    if( domain_parameters_size > sizeof( acc ) )
        return( PSA_ERROR_NOT_SUPPORTED );
    for( i = 0; i < domain_parameters_size; i++ )
        acc = ( acc << 8 ) | domain_parameters[i];
    if( acc > INT_MAX )
        return( PSA_ERROR_NOT_SUPPORTED );
    *exponent = acc;
    return( PSA_SUCCESS );
}

static psa_status_t rsa_generate_key(
    const psa_key_attributes_t *attributes,
    uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length )
{
    psa_status_t status;
    mbedtls_rsa_context rsa;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    int exponent;

    status = psa_read_rsa_exponent( attributes->domain_parameters,
                                    attributes->domain_parameters_size,
                                    &exponent );
    if( status != PSA_SUCCESS )
        return( status );

    mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE );
    ret = mbedtls_rsa_gen_key( &rsa,
                               mbedtls_psa_get_random,
                               MBEDTLS_PSA_RANDOM_STATE,
                               (unsigned int)attributes->core.bits,
                               exponent );
    if( ret != 0 )
        return( mbedtls_to_psa_error( ret ) );

    status = mbedtls_psa_rsa_export_key( attributes->core.type,
                                         &rsa, key_buffer, key_buffer_size,
                                         key_buffer_length );
    mbedtls_rsa_free( &rsa );

    return( status );
}
#endif /* defined(BUILTIN_KEY_TYPE_RSA_KEY_PAIR) */

#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) || \
    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY)

psa_status_t mbedtls_psa_rsa_import_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *data, size_t data_length,
    uint8_t *key_buffer, size_t key_buffer_size,
    size_t *key_buffer_length, size_t *bits )
{
    return( rsa_import_key( attributes, data, data_length,
                            key_buffer, key_buffer_size,
                            key_buffer_length, bits ) );
}

psa_status_t mbedtls_psa_rsa_export_public_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer, size_t key_buffer_size,
    uint8_t *data, size_t data_size, size_t *data_length )
{
    return( rsa_export_public_key( attributes, key_buffer, key_buffer_size,
                                   data, data_size, data_length ) );
}

#endif /* defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||
        * defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) */

#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR)
psa_status_t mbedtls_psa_rsa_generate_key(
    const psa_key_attributes_t *attributes,
    uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length )
{
    return( rsa_generate_key( attributes, key_buffer, key_buffer_size,
                              key_buffer_length ) );
}
#endif /* defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) */

/*
 * BEYOND THIS POINT, TEST DRIVER ENTRY POINTS ONLY.
 */

#if defined(PSA_CRYPTO_DRIVER_TEST)

#if defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_KEY_PAIR) || \
    defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_PUBLIC_KEY)

psa_status_t mbedtls_transparent_test_driver_rsa_import_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *data, size_t data_length,
    uint8_t *key_buffer, size_t key_buffer_size,
    size_t *key_buffer_length, size_t *bits )
{
    return( rsa_import_key( attributes, data, data_length,
                            key_buffer, key_buffer_size,
                            key_buffer_length, bits ) );
}

psa_status_t mbedtls_transparent_test_driver_rsa_export_public_key(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer, size_t key_buffer_size,
    uint8_t *data, size_t data_size, size_t *data_length )
{
    return( rsa_export_public_key( attributes, key_buffer, key_buffer_size,
                                   data, data_size, data_length ) );
}

#endif /* defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_KEY_PAIR) ||
          defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_PUBLIC_KEY) */

#if defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_KEY_PAIR)
psa_status_t mbedtls_transparent_test_driver_rsa_generate_key(
    const psa_key_attributes_t *attributes,
    uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length )
{
    return( rsa_generate_key( attributes, key_buffer, key_buffer_size,
                              key_buffer_length ) );
}
#endif /* defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_RSA_KEY_PAIR) */

#endif /* PSA_CRYPTO_DRIVER_TEST */

#endif /* MBEDTLS_PSA_CRYPTO_C */