/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.
 */

/*
 * XSEC
 *
 * WinCAPICryptoHashHMAC := Windows CAPI Implementation of HMAC
 *
 * Author(s): Berin Lautenbach
 *
 * $Id$
 *
 */

#ifndef WINCAPICRYPTOHASHHMAC_INCLUDE
#define WINCAPICRYPTOHASHHMAC_INCLUDE

#include <xsec/framework/XSECDefs.hpp>
#include <xsec/enc/XSECCryptoHash.hpp>

#if defined (XSEC_HAVE_WINCAPI)

#if !defined(_WIN32_WINNT)
#	define _WIN32_WINNT 0x0400
#endif

#include <wincrypt.h>

class WinCAPICryptoProvider;

/**
 * @ingroup wincapicrypto
 */

/**
 * \brief Implementation of HMAC Hash functions in the Windows providers
 *
 * Uses the Windows Crypt* API functions to implement an HMAC.
 *
 * Unfortunately the Windows Crypto API does not allow callers to enter an
 * HMAC key directly.  It relies on a seed being entered into a digest
 * function that is then used to derive a key that can be used in an
 * HMAC function.
 *
 * Two types of key can therefore be used - a direct Windows key, or
 * a "standard" string as the HMAC key.  In the latter case, the HMAC
 * function is implemented internally around a standard Windows
 * hash function.  In the former case, the Windows HMAC functions are
 * used.  (The latter case is mainly for interoperability testing, where
 * the key is provided and needs to be entered "as is".
 *
 */

class XSEC_EXPORT WinCAPICryptoHashHMAC : public XSECCryptoHash {


public :

	/** @name Constructors and Destructors */
	//@{

	/**
	 * \brief Constructor
	 *
	 * Create the object, with the indicated algorithm
	 * (Currently supports MD5 and SHA1)
	 *
	 *
	 * @param prov handle to a provider that supports the required algorithm.
	 * Both PROV_RSA_FULL and PROV_DSS support MD5 and SHA1
	 * @param alg Digest algorithm to use
	 */
	
	WinCAPICryptoHashHMAC(HCRYPTPROV prov, XSECCryptoHash::HashType alg);
	virtual ~WinCAPICryptoHashHMAC();

	//@}

	/** @name HMAC Functions */
	//@{
	
	/**
	 *\brief Set the HMAC key
	 *
	 * Sets the key - which needs to have a base class of 
	 * WinCAPICryptoKeyHMAC.
	 *
	 * @param key The key the HMAC function should use.
	 */

	virtual void		setKey(const XSECCryptoKey * key);

	//@}

	/** @name Hash functions */
	//@{

	/**
	 * \brief Reset the hash function
	 *
	 * Re-initialises the digest structure.
	 */

	virtual void		reset(void);

	/**
	 * \brief Hash some data.
	 *
	 * Take length bytes of data from the data buffer and update the hash
	 * that already exists.  This function may (and normally will) be called
	 * many times for large blocks of data.
	 *
	 * @param data The buffer containing the data to be hashed.
	 * @param length The number of bytes to be read from data
	 */

	virtual void		hash(unsigned char * data, 
							 unsigned int length);

							 /**
	 * \brief Finish up a Digest operation and read the result.
	 *
	 * This call tells the CryptoHash object that the input is complete and
	 * to finalise the Digest.  The output of the digest is read into the 
	 * hash buffer (at most maxLength bytes).  This is effectively the
	 * signature for the data that has been run through the HMAC function.
	 *
	 * @param hash The buffer the hash should be read into.
	 * @param maxLength The maximum number of bytes to be read into hash
	 * @returns The number of bytes copied into the hash buffer
	 */

	virtual unsigned int finish(unsigned char * hash,
								unsigned int maxLength);

	//@}

	/** @name Information functions */
	//@{

	/**
	 *\brief
	 *
	 * Determine the hash type of this object
	 *
	 * @returns The hash type
	 */

	virtual HashType getHashType(void) const;

	//@}

private:

	// Not implemented constructors
	WinCAPICryptoHashHMAC();

	unsigned char				m_mdValue[XSEC_MAX_HASH_SIZE];		// Final output
	unsigned int				m_mdLen;

	ALG_ID						m_algId;
	XSECCryptoHash::HashType	m_hashType;

	HCRYPTPROV					m_p;
	HCRYPTHASH					m_h;

	unsigned char				m_ipadKeyed[XSEC_MAX_HASH_SIZE];
	unsigned char				m_opadKeyed[XSEC_MAX_HASH_SIZE];

	unsigned int				m_blockSize;		// Block size (bytes) for used alg.

	// Internal functions
	void eraseKeys();

};

#endif /* XSEC_HAVE_WINCAPI */
#endif /* WINCAPICRYPTOHASHHMAC_INCLUDE */