/*
 * Compilation Copyright (c) 1995-2019 by Wei Dai.  All rights reserved.
 *	This copyright applies only to this software distribution package
 *	as a compilation, and does not imply a copyright on any particular
 *	file in the package.
 * 
 *	Boost Software License - Version 1.0 - August 17th, 2003
 *
 *	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.
 */

// authenc.h - originally written and placed in the public domain by Wei Dai

/// \file
/// \brief Classes for authenticated encryption modes of operation
/// \details Authenticated encryption (AE) schemes combine confidentiality and authenticity
///   into a single mode of operation They gained traction in the early 2000's because manually
///   combining them was error prone for the typical developer. Around that time, the desire to
///   authenticate but not ecrypt additional data (AAD) was also identified. When both features
///   are available from a scheme, the system is referred to as an AEAD scheme.
/// \details Crypto++ provides four authenticated encryption modes of operation - CCM, EAX, GCM
///   and OCB mode. All modes derive from AuthenticatedSymmetricCipherBase() and the
///   motivation for the API, like calling AAD a &quot;header&quot;, can be found in Bellare,
///   Rogaway and Wagner's <A HREF="http://web.cs.ucdavis.edu/~rogaway/papers/eax.pdf">The EAX
///   Mode of Operation</A>. The EAX paper suggested a basic API to help standardize AEAD
///   schemes in software and promote adoption of the modes.
/// \sa <A HREF="http://www.cryptopp.com/wiki/Authenticated_Encryption">Authenticated
///   Encryption</A> on the Crypto++ wiki.
/// \since Crypto++ 5.6.0

#ifndef CRYPTOPP_AUTHENC_H
#define CRYPTOPP_AUTHENC_H

#include "cryptlib.h"
#include "secblock.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief Base class for authenticated encryption modes of operation
/// \details AuthenticatedSymmetricCipherBase() serves as a base implementation for one direction
///   (encryption or decryption) of a stream cipher or block cipher mode with authentication.
/// \details Crypto++ provides four authenticated encryption modes of operation - CCM, EAX, GCM
///   and OCB mode. All modes derive from AuthenticatedSymmetricCipherBase() and the
///   motivation for the API, like calling AAD a &quot;header&quot;, can be found in Bellare,
///   Rogaway and Wagner's <A HREF="http://web.cs.ucdavis.edu/~rogaway/papers/eax.pdf">The EAX
///   Mode of Operation</A>. The EAX paper suggested a basic API to help standardize AEAD
///   schemes in software and promote adoption of the modes.
/// \sa <A HREF="http://www.cryptopp.com/wiki/Authenticated_Encryption">Authenticated
///   Encryption</A> on the Crypto++ wiki.
/// \since Crypto++ 5.6.0
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE AuthenticatedSymmetricCipherBase : public AuthenticatedSymmetricCipher
{
public:
	AuthenticatedSymmetricCipherBase() : m_totalHeaderLength(0), m_totalMessageLength(0),
		m_totalFooterLength(0), m_bufferedDataLength(0), m_state(State_Start) {}

	// StreamTransformation interface
	bool IsRandomAccess() const {return false;}
	bool IsSelfInverting() const {return true;}

	void SetKey(const byte *userKey, size_t keylength, const NameValuePairs &params);
	void Restart() {if (m_state > State_KeySet) m_state = State_KeySet;}
	void Resynchronize(const byte *iv, int length=-1);
	void Update(const byte *input, size_t length);
	void ProcessData(byte *outString, const byte *inString, size_t length);
	void TruncatedFinal(byte *mac, size_t macSize);

protected:
	void UncheckedSetKey(const byte * key, unsigned int length,const CryptoPP::NameValuePairs &params)
		{CRYPTOPP_UNUSED(key), CRYPTOPP_UNUSED(length), CRYPTOPP_UNUSED(params); CRYPTOPP_ASSERT(false);}

	void AuthenticateData(const byte *data, size_t len);
	const SymmetricCipher & GetSymmetricCipher() const
		{return const_cast<AuthenticatedSymmetricCipherBase *>(this)->AccessSymmetricCipher();}

	virtual SymmetricCipher & AccessSymmetricCipher() =0;
	virtual bool AuthenticationIsOnPlaintext() const =0;
	virtual unsigned int AuthenticationBlockSize() const =0;
	virtual void SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs &params) =0;
	virtual void Resync(const byte *iv, size_t len) =0;
	virtual size_t AuthenticateBlocks(const byte *data, size_t len) =0;
	virtual void AuthenticateLastHeaderBlock() =0;
	virtual void AuthenticateLastConfidentialBlock() {}
	virtual void AuthenticateLastFooterBlock(byte *mac, size_t macSize) =0;

	// State_AuthUntransformed: authentication is applied to plain text (Authenticate-then-Encrypt)
	// State_AuthTransformed: authentication is applied to cipher text (Encrypt-then-Authenticate)
	enum State {State_Start, State_KeySet, State_IVSet, State_AuthUntransformed, State_AuthTransformed, State_AuthFooter};

	AlignedSecByteBlock m_buffer;
	lword m_totalHeaderLength, m_totalMessageLength, m_totalFooterLength;
	unsigned int m_bufferedDataLength;
	State m_state;
};

NAMESPACE_END

#endif
