text: /*
   *  RSA/SHA-256 signature verification program
   *
   *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
   *  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.
   *
   *  This file is part of mbed TLS (https://tls.mbed.org)
   */
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "../include/mbedtls/config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #if defined(MBEDTLS_PLATFORM_C)
  #include "../include/mbedtls/platform.h"
  #else
  #include <stdio.h>
  #define mbedtls_printf     printf
  #define mbedtls_snprintf   snprintf
  #endif
  
  #if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_RSA_C) ||  \
      !defined(MBEDTLS_SHA256_C) || !defined(MBEDTLS_MD_C) || \
      !defined(MBEDTLS_FS_IO)
  int rsaverify_main( void )
  {
      mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_RSA_C and/or "
              "MBEDTLS_MD_C and/or "
              "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO not defined.\n");
      return( 0 );
  }
  #else
  
  #include "../include/mbedtls/rsa.h"
  #include "../include/mbedtls/md.h"
  
  #include <stdio.h>
  #include <string.h>
  
  int rsaverify_main( int argc, char *argv[] )
  {
      FILE *f;
      int ret, c;
      size_t i;
      mbedtls_rsa_context rsa;
      unsigned char hash[32];
      unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
      char filename[512];
  
      ret = 1;
      if( argc != 2 )
      {
          mbedtls_printf( "usage: rsa_verify <filename>\n" );
  
  #if defined(_WIN32)
          mbedtls_printf( "\n" );
  #endif
  
          goto exit;
      }
  
      mbedtls_printf( "\n  . Reading public key from rsa_pub.txt" );
      fflush( stdout );
  
      if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
      {
          mbedtls_printf( " failed\n  ! Could not open rsa_pub.txt\n" \
                  "  ! Please run rsa_genkey first\n\n" );
          goto exit;
      }
  
      mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
  
      if( ( ret = mbedtls_mpi_read_file( &rsa.N, 16, f ) ) != 0 ||
          ( ret = mbedtls_mpi_read_file( &rsa.E, 16, f ) ) != 0 )
      {
          mbedtls_printf( " failed\n  ! mbedtls_mpi_read_file returned %d\n\n", ret );
          goto exit;
      }
  
      rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
  
      fclose( f );
  
      /*
       * Extract the RSA signature from the text file
       */
      ret = 1;
      mbedtls_snprintf( filename, sizeof(filename), "%s.sig", argv[1] );
  
      if( ( f = fopen( filename, "rb" ) ) == NULL )
      {
          mbedtls_printf( "\n  ! Could not open %s\n\n", filename );
          goto exit;
      }
  
      i = 0;
      while( fscanf( f, "%02X", &c ) > 0 &&
             i < (int) sizeof( buf ) )
          buf[i++] = (unsigned char) c;
  
      fclose( f );
  
      if( i != rsa.len )
      {
          mbedtls_printf( "\n  ! Invalid RSA signature format\n\n" );
          goto exit;
      }
  
      /*
       * Compute the SHA-256 hash of the input file and
       * verify the signature
       */
      mbedtls_printf( "\n  . Verifying the RSA/SHA-256 signature" );
      fflush( stdout );
  
      if( ( ret = mbedtls_md_file(
                      mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ),
                      argv[1], hash ) ) != 0 )
      {
          mbedtls_printf( " failed\n  ! Could not open or read %s\n\n", argv[1] );
          goto exit;
      }
  
      if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC,
                                    MBEDTLS_MD_SHA256, 20, hash, buf ) ) != 0 )
      {
          mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_verify returned -0x%0x\n\n", -ret );
          goto exit;
      }
  
      mbedtls_printf( "\n  . OK (the signature is valid)\n\n" );
  
      ret = 0;
  
  exit:
  
  #if defined(_WIN32)
      mbedtls_printf( "  + Press Enter to exit this program.\n" );
      fflush( stdout ); getchar();
  #endif
  
      return( ret );
  }
  #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
            MBEDTLS_FS_IO */
  