/*

* Copyright (c) 2004 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:    Contains an SRTP specific cryptographic context.

*

*/

#ifndef __SRTP_CRYPTOHANDLER_SRTP_H__

#define __SRTP_CRYPTOHANDLER_SRTP_H__

// INCLUDES

#include <e32base.h>

#include "srtpcryptocontext.h"

#include "srtpcryptohandler.h"

#include "msrtpcryptohandlercontextrtp.h"

// FORWARD DECLARATIONS

class CSRTPStream;

/**

* Contains RTP specific handling of cryptographic context.

*/

class CSRTPCryptoHandlerSRTP : public CSRTPCryptoHandler,

                                public MSRTPCryptoHandlerContextRTP

    {

    public: // Construction

        /**

        * Two-phased constructor.

        * @param aStream  aStream for this cryptohandler.

        * @leave KErrNone if success, system-wide error code otherwise

        */

        static CSRTPCryptoHandlerSRTP* NewL( CSRTPStream& aStream );

        /**

        * Two-phased constructor.

        * @param aStream  aStream for this cryptohandler.

        * @leave KErrNone if success, system-wide error code otherwise  

        */

        static CSRTPCryptoHandlerSRTP* NewLC( CSRTPStream& aStream);

        /**

        * Calculate authentication tag for an RTP packet.

        * Authentication is based on the current 

        * TSRTPAuthAlg algorithm setting in CryptoContext

        * If the operation fails, the function leaves

        * with a system error code.

        * @leave KErrNone if success, system-wide error code otherwise,

        */

        HBufC8* CalculateAuthTagL();

        ~CSRTPCryptoHandlerSRTP( );

   private: // from MSRTPCryptoHandlerContext

        /*

        * Initialize plain packet class (CSRTPPacketRTP) 

        * @param aPacket   RTP packet.

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void

        */        

        void InitializePlainPacketL(const TDesC8& aPacket);

        /*

        * Initialize encrypted packet class (CSRTPPacketSRTP) 

        * @param aPacket   SRTP packet.

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void

        */        

        void InitializeEncryptedPacketL(const TDesC8& aPacket);

        /* 

        * Derive session encryption, salting and authentication keys

        * for RTP        

        * @return void                

        */

        void DeriveSessionKeysL();

        /*

        * Encrypt plain RTP packet

        * @leave KErrNone if success, system-wide error code otherwise

        * @return encrypted packet

        */        

        HBufC8* EncryptL();

        /*

        * Decrypt ciphered SRTP packet

        * @leave KErrNone if success, system-wide error code otherwise

        * @return plain packet

        */        

        HBufC8* DecryptL();        

        /*

        * Check that crypto context MKI and 

        * packet MKI match.

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void

        */        

        void CheckMasterKeyIdentifierL();

        /*

        * Perform the authentication step

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void

        */        

        void AuthenticateL();

        /*

        * Perform the replay protection step

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void

        */        

        void ReplayProtectionL();

        /*

        * function for querying whether master key or salt has been updated

        * @return master keys update status

        */        

        TBool MasterKeysUpdated();

        /*

        * function for updating Replay index after ReplayProtection Check

        * @return void

        */            

        void AddReplayIndex() ;

    private: // from MSRTPCryptoHandlerContextRTP

        /*

        * Determines the index i

        * of an SRTP packet with given sequence number SEQ on sender's side.         

        * @return void        

        */

        void CountSenderPacketIndexL();        

        /*

        * Implements pseudocode on RFC 3711 Appendix A

        * for determining the index i of an SRTP packet with given sequence number SEQ

        * and current s_l value in receiver side

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void                

        */

        void CountReceiverPacketIndexL();        

        /*

        * Assign receiver counter s_l to the value of first sequence number. 

        * @return void                

        */

        void SetReceiver_s_l();        

        /*

        * Conditionally update ROC in sender's side:

        * Each time SEQ wraps MOD 2^16, the sender side must 

        * increment ROC by one MOD 2^32.

        * @return void                

        */

        void UpdateROC();        

        /*

        * Conditionally update s_l and ROC based on v value. 

        * See RFC 3711 section 3.3.1 for more information

        * @leave KErrNone if success, system-wide error code otherwise

        * @return void                

        */

        void Update_s_l_and_RocL();

       /*

        * Add auth tag to the given packet.

        * @param aSrtpPacketPtr  packet pointer

        * @leave KErrNone if success, system-wide error code otherwise,

        * @return void

        */

        void AddAuthTagToPacketL(TUint8* aSrtpPacketPtr); 

        /*

        * Check if packets is carrying Roll-Over Counter

        * @return TBool return True if it should carry, otherwise return False.

        */

        TBool CarryROC();    

        /*

        * Call AuthenticateL in MSRTPAuthentication -interface

        * to get authentication tag based on algorithm

        * that is currently set in crypto context

        * @param aAuthenticatedArea  portion of data to be authenticated

        * @param aRoc Roll-Over counter 

        * @leave KErrNone if success, system-wide error code otherwise,

        * @return authentication tag 

        */

        HBufC8* DoAuthenticationL(const TDesC8& aAuthenticatedArea,

        						 const TDesC8& aRoc);

      private: // methods   

        /*

        * Count IV and transform payload

        * @return HBufC8*, transformed encrypted / decrypted paylod

        */    

        HBufC8* CountIV_And_TransformL();

        /*

        * Add MKI to the given packet.

        * Common for RTP and RTCP.

        * @param aSrtpPacketPtr  packet pointer

        * @return void

        */

        void AddMKIToPacket(TUint8* aSrtpPacketPtr); 

        /*

        * Count sender packet index when receiving the packet under RCC mode 1

        * based on the attached sender ROC

        * @return TUint64 sender packet index.

        */              

        TInt64 CountSndIndxbySndROC();

        void ConstructL();

        void ReKeyCheck();

        TBool CSRTPCryptoHandlerSRTP::IfAddAuthTag();

        CSRTPCryptoHandlerSRTP( CSRTPStream& aStream );

    private: // data

        TUint32                     iROC;            // //only using when RCC mode as sender Roc

        TUint16                     iS_L;           // s_l, highest received SEQ   

        TUint16                     iCurrentSeq;     // current sequence number  

        TUint64                     iPktIndex;       //packet index

        TInt32                      iV;             // local v value

        TInt						iReplayIndexDelta;

		TUint64			  			iSRTPMasterKeyLifeTime;

    private:

    #ifdef EUNIT_TESTING

        friend class UT_CSRTPCryptoHandlerSRTP;

        friend class UT_CSRTPCryptoHandler;

    #endif 

    };

#endif // __SRTP_CRYPTOHANDLER_SRTP_H__