pk_decrypt.c

/*
 *  Public key-based simple decryption 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_PK_PARSE_C) && \
    defined(MBEDTLS_FS_IO) && defined(MBEDTLS_ENTROPY_C) && \
    defined(MBEDTLS_CTR_DRBG_C)
#include "mbedtls/error.h"
#include "mbedtls/pk.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"

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

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


int main( int argc, char *argv[] )
{
    FILE *f;
    int ret = 1;
    unsigned c;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    size_t i, olen = 0;
    mbedtls_pk_context pk;
    mbedtls_entropy_context entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    unsigned char result[1024];
    unsigned char buf[512];
    const char *pers = "mbedtls_pk_decrypt";
    ((void) argv);

    mbedtls_pk_init( &pk );
    mbedtls_entropy_init( &entropy );
    mbedtls_ctr_drbg_init( &ctr_drbg );

    memset(result, 0, sizeof( result ) );

    if( argc != 2 )
    {
        mbedtls_printf( "usage: mbedtls_pk_decrypt <key_file>\n" );

#if defined(_WIN32)
        mbedtls_printf( "\n" );
#endif

        goto exit;
    }

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

    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 -0x%04x\n",
                        (unsigned int) -ret );
        goto exit;
    }

    mbedtls_printf( "\n  . Reading private key from '%s'", argv[1] );
    fflush( stdout );

    if( ( ret = mbedtls_pk_parse_keyfile( &pk, argv[1], "",
                    mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_keyfile returned -0x%04x\n", (unsigned int) -ret );
        goto exit;
    }

    /*
     * Extract the RSA encrypted value from the text file
     */
    if( ( f = fopen( "result-enc.txt", "rb" ) ) == NULL )
    {
        mbedtls_printf( "\n  ! Could not open %s\n\n", "result-enc.txt" );
        ret = 1;
        goto exit;
    }

    i = 0;
    while( fscanf( f, "%02X", (unsigned int*) &c ) > 0 &&
           i < (int) sizeof( buf ) )
    {
        buf[i++] = (unsigned char) c;
    }

    fclose( f );

    /*
     * Decrypt the encrypted RSA data and print the result.
     */
    mbedtls_printf( "\n  . Decrypting the encrypted data" );
    fflush( stdout );

    if( ( ret = mbedtls_pk_decrypt( &pk, buf, i, result, &olen, sizeof(result),
                            mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_pk_decrypt returned -0x%04x\n",
                        (unsigned int) -ret );
        goto exit;
    }

    mbedtls_printf( "\n  . OK\n\n" );

    mbedtls_printf( "The decrypted result is: '%s'\n\n", result );

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:

    mbedtls_pk_free( &pk );
    mbedtls_entropy_free( &entropy );
    mbedtls_ctr_drbg_free( &ctr_drbg );

#if defined(MBEDTLS_ERROR_C)
    if( exit_code != MBEDTLS_EXIT_SUCCESS )
    {
        mbedtls_strerror( ret, (char *) buf, sizeof( buf ) );
        mbedtls_printf( "  !  Last error was: %s\n", buf );
    }
#endif

#if defined(_WIN32)
    mbedtls_printf( "  + Press Enter to exit this program.\n" );
    fflush( stdout ); getchar();
#endif

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