text: /*
   * Amazon FreeRTOS Crypto V1.0.1
   * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   * http://aws.amazon.com/freertos
   * http://www.FreeRTOS.org
   */
  
  
  /* FreeRTOS includes. */
  #include "FreeRTOS.h"
  #include "FreeRTOSIPConfig.h"
  #include "aws_crypto.h"
  
  /* mbedTLS includes. */
  #include "mbedtls/config.h"
  #include "mbedtls/platform.h"
  #include "mbedtls/sha256.h"
  #include "mbedtls/sha1.h"
  #include "mbedtls/pk.h"
  #include "mbedtls/x509_crt.h"
  
  /* C runtime includes. */
  #include <string.h>
  
  /**
   * @brief Internal signature verification context structure
   */
  typedef struct SignatureVerificationState
  {
      BaseType_t xAsymmetricAlgorithm;
      BaseType_t xHashAlgorithm;
      mbedtls_sha1_context xSHA1Context;
      mbedtls_sha256_context xSHA256Context;
  } SignatureVerificationState_t, * SignatureVerificationStatePtr_t;
  
  /*
   * Helper routines
   */
  
  /**
   * @brief Implements libc calloc semantics using the FreeRTOS heap
   */
  static void * prvCalloc( size_t xNmemb,
                           size_t xSize )
  {
      void * pvNew = pvPortMalloc( xNmemb * xSize );
  
      if( NULL != pvNew )
      {
          memset( pvNew, 0, xNmemb * xSize );
      }
  
      return pvNew;
  }
  
  /**
   * @brief Verifies a cryptographic signature based on the signer
   * certificate, hash algorithm, and the data that was signed.
   */
  static BaseType_t prvVerifySignature( char * pcSignerCertificate,
                                        size_t xSignerCertificateLength,
                                        BaseType_t xHashAlgorithm,
                                        uint8_t * pucHash,
                                        size_t xHashLength,
                                        uint8_t * pucSignature,
                                        size_t xSignatureLength )
  {
      BaseType_t xResult = pdTRUE;
      mbedtls_x509_crt xCertCtx;
      mbedtls_md_type_t xMbedHashAlg = MBEDTLS_MD_SHA256;
  
  
      memset( &xCertCtx, 0, sizeof( mbedtls_x509_crt ) );
  
      /*
       * Map the hash algorithm
       */
      if( cryptoHASH_ALGORITHM_SHA1 == xHashAlgorithm )
      {
          xMbedHashAlg = MBEDTLS_MD_SHA1;
      }
  
      /*
       * Decode and create a certificate context
       */
      mbedtls_x509_crt_init( &xCertCtx );
  
      if( 0 != mbedtls_x509_crt_parse(
              &xCertCtx, ( const unsigned char * ) pcSignerCertificate, xSignerCertificateLength ) )
      {
          xResult = pdFALSE;
      }
  
      /*
       * Verify the signature using the public key from the decoded certificate
       */
      if( pdTRUE == xResult )
      {
          if( 0 != mbedtls_pk_verify(
                  &xCertCtx.pk,
                  xMbedHashAlg,
                  pucHash,
                  xHashLength,
                  pucSignature,
                  xSignatureLength ) )
          {
              xResult = pdFALSE;
          }
      }
  
      /*
       * Clean-up
       */
      mbedtls_x509_crt_free( &xCertCtx );
  
      return xResult;
  }
  
  /*
   * Interface routines
   */
  
  /**
   * @brief Overrides CRT heap callouts to use FreeRTOS instead
   */
  void CRYPTO_ConfigureHeap( void )
  {
      /*
       * Ensure that the FreeRTOS heap is used
       */
      mbedtls_platform_set_calloc_free( prvCalloc, vPortFree ); /*lint !e534 This function always return 0. */
  }
  
  /**
   * @brief Creates signature verification context.
   */
  BaseType_t CRYPTO_SignatureVerificationStart( void ** ppvContext,
                                                BaseType_t xAsymmetricAlgorithm,
                                                BaseType_t xHashAlgorithm )
  {
      BaseType_t xResult = pdTRUE;
      SignatureVerificationStatePtr_t pxCtx = NULL;
  
      /*
       * Allocate the context
       */
      if( NULL == ( pxCtx = ( SignatureVerificationStatePtr_t ) pvPortMalloc(
                        sizeof( *pxCtx ) ) ) ) /*lint !e9087 Allow casting void* to other types. */
      {
          xResult = pdFALSE;
      }
  
      if( pdTRUE == xResult )
      {
          *ppvContext = pxCtx;
  
          /*
           * Store the algorithm identifiers
           */
          pxCtx->xAsymmetricAlgorithm = xAsymmetricAlgorithm;
          pxCtx->xHashAlgorithm = xHashAlgorithm;
  
          /*
           * Initialize the requested hash type
           */
          if( cryptoHASH_ALGORITHM_SHA1 == pxCtx->xHashAlgorithm )
          {
              mbedtls_sha1_init( &pxCtx->xSHA1Context );
              ( void )mbedtls_sha1_starts_ret( &pxCtx->xSHA1Context );
          }
          else
          {
              mbedtls_sha256_init( &pxCtx->xSHA256Context );
              ( void )mbedtls_sha256_starts_ret( &pxCtx->xSHA256Context, 0 );
          }
      }
  
      return xResult;
  }
  
  /**
   * @brief Adds bytes to an in-progress hash for subsequent signature
   * verification.
   */
  void CRYPTO_SignatureVerificationUpdate( void * pvContext,
                                           uint8_t * pucData,
                                           size_t xDataLength )
  {
      SignatureVerificationStatePtr_t pxCtx = ( SignatureVerificationStatePtr_t ) pvContext; /*lint !e9087 Allow casting void* to other types. */
  
      /*
       * Add the data to the hash of the requested type
       */
      if( cryptoHASH_ALGORITHM_SHA1 == pxCtx->xHashAlgorithm )
      {
          ( void )mbedtls_sha1_update_ret( &pxCtx->xSHA1Context, pucData, xDataLength );
      }
      else
      {
          ( void )mbedtls_sha256_update_ret( &pxCtx->xSHA256Context, pucData, xDataLength );
      }
  }
  
  /**
   * @brief Performs signature verification on a cryptographic hash.
   */
  BaseType_t CRYPTO_SignatureVerificationFinal( void * pvContext,
                                                char * pcSignerCertificate,
                                                size_t xSignerCertificateLength,
                                                uint8_t * pucSignature,
                                                size_t xSignatureLength )
  {
      BaseType_t xResult = pdTRUE;
      SignatureVerificationStatePtr_t pxCtx =
          ( SignatureVerificationStatePtr_t ) pvContext; /*lint !e9087 Allow casting void* to other types. */
      uint8_t ucSHA1[ cryptoSHA1_DIGEST_BYTES ];
      uint8_t ucSHA256[ cryptoSHA256_DIGEST_BYTES ];
      uint8_t * pucHash = NULL;
      size_t xHashLength = 0;
  
      /*
       * Finish the hash
       */
      if( cryptoHASH_ALGORITHM_SHA1 == pxCtx->xHashAlgorithm )
      {
          ( void )mbedtls_sha1_finish_ret( &pxCtx->xSHA1Context, ucSHA1 );
          pucHash = ucSHA1;
          xHashLength = cryptoSHA1_DIGEST_BYTES;
      }
      else
      {
          ( void )mbedtls_sha256_finish_ret( &pxCtx->xSHA256Context, ucSHA256 );
          pucHash = ucSHA256;
          xHashLength = cryptoSHA256_DIGEST_BYTES;
      }
  
      /*
       * Verify the signature
       */
      xResult = prvVerifySignature( pcSignerCertificate,
                                    xSignerCertificateLength,
                                    pxCtx->xHashAlgorithm,
                                    pucHash,
                                    xHashLength,
                                    pucSignature,
                                    xSignatureLength );
  
      /*
       * Clean-up
       */
      vPortFree( pxCtx );
  
      return xResult;
  }
  