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HMACEngine.h
//
// HMACEngine.h
//
// $Id: //poco/1.4/Foundation/include/Poco/HMACEngine.h#1 $
//
// Library: Foundation
// Package: Crypt
// Module:  HMACEngine
//
// Definition of the HMACEngine class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// 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, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_HMACEngine_INCLUDED
#define Foundation_HMACEngine_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/DigestEngine.h"
#include <cstring>


namespace Poco {


template <class Engine>
00052 class HMACEngine: public DigestEngine
      /// This class implementes the HMAC message
      /// authentication code algorithm, as specified
      /// in RFC 2104. The underlying DigestEngine
      /// (MD5Engine, SHA1Engine, etc.) must be given as 
      /// template argument.
      /// Since the HMACEngine is a DigestEngine, it can
      /// be used with the DigestStream class to create
      /// a HMAC for a stream.
{
public:
      enum
      {
            BLOCK_SIZE  = Engine::BLOCK_SIZE,
            DIGEST_SIZE = Engine::DIGEST_SIZE
      };
      
      HMACEngine(const std::string& passphrase)
      {
            init(passphrase.data(), (unsigned) passphrase.length());
      }
      
      HMACEngine(const char* passphrase, unsigned length)
      {
            poco_check_ptr (passphrase);

            init(passphrase, length);
      }
      
      ~HMACEngine()
      {
            std::memset(_ipad, 0, BLOCK_SIZE);
            std::memset(_opad, 0, BLOCK_SIZE);
            delete [] _ipad;
            delete [] _opad;
      }
            
00089       unsigned digestLength() const
      {
            return DIGEST_SIZE;
      }
      
00094       void reset()
      {
            _engine.reset();
            _engine.update(_ipad, BLOCK_SIZE);
      }
      
00100       const DigestEngine::Digest& digest()
      {
            const DigestEngine::Digest& d = _engine.digest();
            char db[DIGEST_SIZE];
            char* pdb = db;
            for (DigestEngine::Digest::const_iterator it = d.begin(); it != d.end(); ++it)
                  *pdb++ = *it;
            _engine.reset();
            _engine.update(_opad, BLOCK_SIZE);
            _engine.update(db, DIGEST_SIZE);
            const DigestEngine::Digest& result = _engine.digest();
            reset();
            return result;
      }

protected:
      void init(const char* passphrase, unsigned length)
      {
            _ipad = new char[BLOCK_SIZE];
            _opad = new char[BLOCK_SIZE];
            std::memset(_ipad, 0, BLOCK_SIZE);
            std::memset(_opad, 0, BLOCK_SIZE);
            if (length > BLOCK_SIZE)
            {
                  _engine.reset();
                  _engine.update(passphrase, length);
                  const DigestEngine::Digest& d = _engine.digest();
                  char* ipad = _ipad;
                  char* opad = _opad;
                  int n = BLOCK_SIZE;
                  for (DigestEngine::Digest::const_iterator it = d.begin(); it != d.end() && n-- > 0; ++it)
                  {
                        *ipad++ = *it;
                        *opad++ = *it;
                  }
            }
            else
            {
                  std::memcpy(_ipad, passphrase, length);
                  std::memcpy(_opad, passphrase, length);
            }
            for (int i = 0; i < BLOCK_SIZE; ++i)
            {
                  _ipad[i] ^= 0x36;
                  _opad[i] ^= 0x5c;
            }
            reset();
      }
      
00149       void updateImpl(const void* data, unsigned length)
      {
            _engine.update(data, length);
      }

private:
      HMACEngine();
      HMACEngine(const HMACEngine&);
      HMACEngine& operator = (const HMACEngine&);

      Engine _engine;
      char*  _ipad;
      char*  _opad;
};


} // namespace Poco


#endif // Foundation_HMACEngine_INCLUDED

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