rsa_genkey.c

/*
 *  Example RSA key generation program
 *
 *  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 "mbedtls/build_info.h"

#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#include <stdlib.h>
#define mbedtls_printf          printf
#define mbedtls_exit            exit
#define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
#define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
#endif /* MBEDTLS_PLATFORM_C */

#if defined(MBEDTLS_BIGNUM_C) && defined(MBEDTLS_ENTROPY_C) && \
    defined(MBEDTLS_RSA_C) && defined(MBEDTLS_GENPRIME) && \
    defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C)
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/bignum.h"
#include "mbedtls/rsa.h"

#include <stdio.h>
#include <string.h>
#endif

#define KEY_SIZE 2048
#define EXPONENT 65537

#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_ENTROPY_C) ||   \
    !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_GENPRIME) ||      \
    !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C)
int main( void )
{
    mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C and/or "
           "MBEDTLS_RSA_C and/or MBEDTLS_GENPRIME and/or "
           "MBEDTLS_FS_IO and/or MBEDTLS_CTR_DRBG_C not defined.\n");
    mbedtls_exit( 0 );
}
#else


int main( void )
{
    int ret = 1;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    mbedtls_rsa_context rsa;
    mbedtls_entropy_context entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    mbedtls_mpi N, P, Q, D, E, DP, DQ, QP;
    FILE *fpub  = NULL;
    FILE *fpriv = NULL;
    const char *pers = "rsa_genkey";

    mbedtls_ctr_drbg_init( &ctr_drbg );
    mbedtls_rsa_init( &rsa );
    mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
    mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E ); mbedtls_mpi_init( &DP );
    mbedtls_mpi_init( &DQ ); mbedtls_mpi_init( &QP );

    mbedtls_printf( "\n  . Seeding the random number generator..." );
    fflush( stdout );

    mbedtls_entropy_init( &entropy );
    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
                               (const unsigned char *) pers,
                               strlen( pers ) ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
        goto exit;
    }

    mbedtls_printf( " ok\n  . Generating the RSA key [ %d-bit ]...", KEY_SIZE );
    fflush( stdout );

    if( ( ret = mbedtls_rsa_gen_key( &rsa, mbedtls_ctr_drbg_random, &ctr_drbg, KEY_SIZE,
                                     EXPONENT ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_rsa_gen_key returned %d\n\n", ret );
        goto exit;
    }

    mbedtls_printf( " ok\n  . Exporting the public  key in rsa_pub.txt...." );
    fflush( stdout );

    if( ( ret = mbedtls_rsa_export    ( &rsa, &N, &P, &Q, &D, &E ) ) != 0 ||
        ( ret = mbedtls_rsa_export_crt( &rsa, &DP, &DQ, &QP ) )      != 0 )
    {
        mbedtls_printf( " failed\n  ! could not export RSA parameters\n\n" );
        goto exit;
    }

    if( ( fpub = fopen( "rsa_pub.txt", "wb+" ) ) == NULL )
    {
        mbedtls_printf( " failed\n  ! could not open rsa_pub.txt for writing\n\n" );
        goto exit;
    }

    if( ( ret = mbedtls_mpi_write_file( "N = ", &N, 16, fpub ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "E = ", &E, 16, fpub ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_mpi_write_file returned %d\n\n", ret );
        goto exit;
    }

    mbedtls_printf( " ok\n  . Exporting the private key in rsa_priv.txt..." );
    fflush( stdout );

    if( ( fpriv = fopen( "rsa_priv.txt", "wb+" ) ) == NULL )
    {
        mbedtls_printf( " failed\n  ! could not open rsa_priv.txt for writing\n" );
        goto exit;
    }

    if( ( ret = mbedtls_mpi_write_file( "N = " , &N , 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "E = " , &E , 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "D = " , &D , 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "P = " , &P , 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "Q = " , &Q , 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "DP = ", &DP, 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "DQ = ", &DQ, 16, fpriv ) ) != 0 ||
        ( ret = mbedtls_mpi_write_file( "QP = ", &QP, 16, fpriv ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_mpi_write_file returned %d\n\n", ret );
        goto exit;
    }
    mbedtls_printf( " ok\n\n" );

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:

    if( fpub  != NULL )
        fclose( fpub );

    if( fpriv != NULL )
        fclose( fpriv );

    mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
    mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E ); mbedtls_mpi_free( &DP );
    mbedtls_mpi_free( &DQ ); mbedtls_mpi_free( &QP );
    mbedtls_rsa_free( &rsa );
    mbedtls_ctr_drbg_free( &ctr_drbg );
    mbedtls_entropy_free( &entropy );

    mbedtls_exit( exit_code );
}
#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_RSA_C &&
          MBEDTLS_GENPRIME && MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */