text: /*
   *  Entropy accumulator implementation
   *
   *  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 "mbedtls/config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #if defined(MBEDTLS_ENTROPY_C)
  
  #include "mbedtls/entropy.h"
  #include "mbedtls/entropy_poll.h"
  
  #include <string.h>
  
  #if defined(MBEDTLS_FS_IO)
  #include <stdio.h>
  #endif
  
  #if defined(MBEDTLS_SELF_TEST)
  #if defined(MBEDTLS_PLATFORM_C)
  #include "mbedtls/platform.h"
  #else
  #include <stdio.h>
  #define mbedtls_printf     printf
  #endif /* MBEDTLS_PLATFORM_C */
  #endif /* MBEDTLS_SELF_TEST */
  
  #if defined(MBEDTLS_HAVEGE_C)
  #include "mbedtls/havege.h"
  #endif
  
  /* Implementation that should never be optimized out by the compiler */
  static void mbedtls_zeroize( void *v, size_t n ) {
      volatile unsigned char *p = v; while( n-- ) *p++ = 0;
  }
  
  #define ENTROPY_MAX_LOOP    256     /**< Maximum amount to loop before error */
  
  void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
  {
      memset( ctx, 0, sizeof(mbedtls_entropy_context) );
  
  #if defined(MBEDTLS_THREADING_C)
      mbedtls_mutex_init( &ctx->mutex );
  #endif
  
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
      mbedtls_sha512_starts( &ctx->accumulator, 0 );
  #else
      mbedtls_sha256_starts( &ctx->accumulator, 0 );
  #endif
  #if defined(MBEDTLS_HAVEGE_C)
      mbedtls_havege_init( &ctx->havege_data );
  #endif
  
  #if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
  #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
      mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,
                                  MBEDTLS_ENTROPY_MIN_PLATFORM,
                                  MBEDTLS_ENTROPY_SOURCE_STRONG );
  #endif
  #if defined(MBEDTLS_TIMING_C)
      mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL,
                                  MBEDTLS_ENTROPY_MIN_HARDCLOCK,
                                  MBEDTLS_ENTROPY_SOURCE_WEAK );
  #endif
  #if defined(MBEDTLS_HAVEGE_C)
      mbedtls_entropy_add_source( ctx, mbedtls_havege_poll, &ctx->havege_data,
                                  MBEDTLS_ENTROPY_MIN_HAVEGE,
                                  MBEDTLS_ENTROPY_SOURCE_STRONG );
  #endif
  #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
      mbedtls_entropy_add_source( ctx, mbedtls_hardware_poll, NULL,
                                  MBEDTLS_ENTROPY_MIN_HARDWARE,
                                  MBEDTLS_ENTROPY_SOURCE_STRONG );
  #endif
  #endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
  }
  
  void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
  {
  #if defined(MBEDTLS_HAVEGE_C)
      mbedtls_havege_free( &ctx->havege_data );
  #endif
  #if defined(MBEDTLS_THREADING_C)
      mbedtls_mutex_free( &ctx->mutex );
  #endif
      mbedtls_zeroize( ctx, sizeof( mbedtls_entropy_context ) );
  }
  
  int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
                          mbedtls_entropy_f_source_ptr f_source, void *p_source,
                          size_t threshold, int strong )
  {
      int index, ret = 0;
  
  #if defined(MBEDTLS_THREADING_C)
      if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
          return( ret );
  #endif
  
      index = ctx->source_count;
      if( index >= MBEDTLS_ENTROPY_MAX_SOURCES )
      {
          ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;
          goto exit;
      }
  
      ctx->source[index].f_source  = f_source;
      ctx->source[index].p_source  = p_source;
      ctx->source[index].threshold = threshold;
      ctx->source[index].strong    = strong;
  
      ctx->source_count++;
  
  exit:
  #if defined(MBEDTLS_THREADING_C)
      if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
          return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
  #endif
  
      return( ret );
  }
  
  /*
   * Entropy accumulator update
   */
  static int entropy_update( mbedtls_entropy_context *ctx, unsigned char source_id,
                             const unsigned char *data, size_t len )
  {
      unsigned char header[2];
      unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];
      size_t use_len = len;
      const unsigned char *p = data;
  
      if( use_len > MBEDTLS_ENTROPY_BLOCK_SIZE )
      {
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
          mbedtls_sha512( data, len, tmp, 0 );
  #else
          mbedtls_sha256( data, len, tmp, 0 );
  #endif
          p = tmp;
          use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
      }
  
      header[0] = source_id;
      header[1] = use_len & 0xFF;
  
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
      mbedtls_sha512_update( &ctx->accumulator, header, 2 );
      mbedtls_sha512_update( &ctx->accumulator, p, use_len );
  #else
      mbedtls_sha256_update( &ctx->accumulator, header, 2 );
      mbedtls_sha256_update( &ctx->accumulator, p, use_len );
  #endif
  
      return( 0 );
  }
  
  int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
                             const unsigned char *data, size_t len )
  {
      int ret;
  
  #if defined(MBEDTLS_THREADING_C)
      if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
          return( ret );
  #endif
  
      ret = entropy_update( ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len );
  
  #if defined(MBEDTLS_THREADING_C)
      if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
          return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
  #endif
  
      return( ret );
  }
  
  /*
   * Run through the different sources to add entropy to our accumulator
   */
  static int entropy_gather_internal( mbedtls_entropy_context *ctx )
  {
      int ret, i, have_one_strong = 0;
      unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
      size_t olen;
  
      if( ctx->source_count == 0 )
          return( MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED );
  
      /*
       * Run through our entropy sources
       */
      for( i = 0; i < ctx->source_count; i++ )
      {
          if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
              have_one_strong = 1;
  
          olen = 0;
          if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
                          buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen ) ) != 0 )
          {
              return( ret );
          }
  
          /*
           * Add if we actually gathered something
           */
          if( olen > 0 )
          {
              entropy_update( ctx, (unsigned char) i, buf, olen );
              ctx->source[i].size += olen;
          }
      }
  
      if( have_one_strong == 0 )
          return( MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE );
  
      return( 0 );
  }
  
  /*
   * Thread-safe wrapper for entropy_gather_internal()
   */
  int mbedtls_entropy_gather( mbedtls_entropy_context *ctx )
  {
      int ret;
  
  #if defined(MBEDTLS_THREADING_C)
      if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
          return( ret );
  #endif
  
      ret = entropy_gather_internal( ctx );
  
  #if defined(MBEDTLS_THREADING_C)
      if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
          return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
  #endif
  
      return( ret );
  }
  
  int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
  {
      int ret, count = 0, i, done;
      mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
      unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
  
      if( len > MBEDTLS_ENTROPY_BLOCK_SIZE )
          return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
  
  #if defined(MBEDTLS_THREADING_C)
      if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
          return( ret );
  #endif
  
      /*
       * Always gather extra entropy before a call
       */
      do
      {
          if( count++ > ENTROPY_MAX_LOOP )
          {
              ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
              goto exit;
          }
  
          if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
              goto exit;
  
          done = 1;
          for( i = 0; i < ctx->source_count; i++ )
              if( ctx->source[i].size < ctx->source[i].threshold )
                  done = 0;
      }
      while( ! done );
  
      memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
  
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
      mbedtls_sha512_finish( &ctx->accumulator, buf );
  
      /*
       * Reset accumulator and counters and recycle existing entropy
       */
      memset( &ctx->accumulator, 0, sizeof( mbedtls_sha512_context ) );
      mbedtls_sha512_starts( &ctx->accumulator, 0 );
      mbedtls_sha512_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
  
      /*
       * Perform second SHA-512 on entropy
       */
      mbedtls_sha512( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
  #else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
      mbedtls_sha256_finish( &ctx->accumulator, buf );
  
      /*
       * Reset accumulator and counters and recycle existing entropy
       */
      memset( &ctx->accumulator, 0, sizeof( mbedtls_sha256_context ) );
      mbedtls_sha256_starts( &ctx->accumulator, 0 );
      mbedtls_sha256_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
  
      /*
       * Perform second SHA-256 on entropy
       */
      mbedtls_sha256( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
  #endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
  
      for( i = 0; i < ctx->source_count; i++ )
          ctx->source[i].size = 0;
  
      memcpy( output, buf, len );
  
      ret = 0;
  
  exit:
  #if defined(MBEDTLS_THREADING_C)
      if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
          return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
  #endif
  
      return( ret );
  }
  
  #if defined(MBEDTLS_FS_IO)
  int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path )
  {
      int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
      FILE *f;
      unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
  
      if( ( f = fopen( path, "wb" ) ) == NULL )
          return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
  
      if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
          goto exit;
  
      if( fwrite( buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f ) != MBEDTLS_ENTROPY_BLOCK_SIZE )
      {
          ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
          goto exit;
      }
  
      ret = 0;
  
  exit:
      fclose( f );
      return( ret );
  }
  
  int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path )
  {
      FILE *f;
      size_t n;
      unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
  
      if( ( f = fopen( path, "rb" ) ) == NULL )
          return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
  
      fseek( f, 0, SEEK_END );
      n = (size_t) ftell( f );
      fseek( f, 0, SEEK_SET );
  
      if( n > MBEDTLS_ENTROPY_MAX_SEED_SIZE )
          n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
  
      if( fread( buf, 1, n, f ) != n )
      {
          fclose( f );
          return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
      }
  
      fclose( f );
  
      mbedtls_entropy_update_manual( ctx, buf, n );
  
      return( mbedtls_entropy_write_seed_file( ctx, path ) );
  }
  #endif /* MBEDTLS_FS_IO */
  
  #if defined(MBEDTLS_SELF_TEST)
  /*
   * Dummy source function
   */
  static int entropy_dummy_source( void *data, unsigned char *output,
                                   size_t len, size_t *olen )
  {
      ((void) data);
  
      memset( output, 0x2a, len );
      *olen = len;
  
      return( 0 );
  }
  
  /*
   * The actual entropy quality is hard to test, but we can at least
   * test that the functions don't cause errors and write the correct
   * amount of data to buffers.
   */
  int mbedtls_entropy_self_test( int verbose )
  {
      int ret = 0;
      mbedtls_entropy_context ctx;
      unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
      unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
      size_t i, j;
  
      if( verbose != 0 )
          mbedtls_printf( "  ENTROPY test: " );
  
      mbedtls_entropy_init( &ctx );
  
      /* First do a gather to make sure we have default sources */
      if( ( ret = mbedtls_entropy_gather( &ctx ) ) != 0 )
          goto cleanup;
  
      ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16,
                                        MBEDTLS_ENTROPY_SOURCE_WEAK );
      if( ret != 0 )
          goto cleanup;
  
      if( ( ret = mbedtls_entropy_update_manual( &ctx, buf, sizeof buf ) ) != 0 )
          goto cleanup;
  
      /*
       * To test that mbedtls_entropy_func writes correct number of bytes:
       * - use the whole buffer and rely on ASan to detect overruns
       * - collect entropy 8 times and OR the result in an accumulator:
       *   any byte should then be 0 with probably 2^(-64), so requiring
       *   each of the 32 or 64 bytes to be non-zero has a false failure rate
       *   of at most 2^(-58) which is acceptable.
       */
      for( i = 0; i < 8; i++ )
      {
          if( ( ret = mbedtls_entropy_func( &ctx, buf, sizeof( buf ) ) ) != 0 )
              goto cleanup;
  
          for( j = 0; j < sizeof( buf ); j++ )
              acc[j] |= buf[j];
      }
  
      for( j = 0; j < sizeof( buf ); j++ )
      {
          if( acc[j] == 0 )
          {
              ret = 1;
              goto cleanup;
          }
      }
  
  cleanup:
      mbedtls_entropy_free( &ctx );
  
      if( verbose != 0 )
      {
          if( ret != 0 )
              mbedtls_printf( "failed\n" );
          else
              mbedtls_printf( "passed\n" );
  
          mbedtls_printf( "\n" );
      }
  
      return( ret != 0 );
  }
  #endif /* MBEDTLS_SELF_TEST */
  
  #endif /* MBEDTLS_ENTROPY_C */
  