/*

* Copyright (c) 2005-2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "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: 

*

*/

/**

 @file

*/

#include "pkcs5kdf.h"

/* Before complaining about the variable names in this file, 

 * read the pkcs5 spec and all will become clear.

 */

EXPORT_C void TPKCS5KDF::DeriveKeyL(TDes8& aKey, const TDesC8& aPasswd, const TDesC8& aSalt, 

	const TUint aIterations)

{

	CSHA1* sha1 = CSHA1::NewL();

	CleanupStack::PushL(sha1);

	CHMAC* hmac = CHMAC::NewL(aPasswd, sha1);

	CleanupStack::Pop(sha1); //hmac now owns it

	CleanupStack::PushL(hmac);

	TUint hashBytes = hmac->HashSize();

	TUint c = aIterations;

	TUint l = aKey.Length() / hashBytes; 

	if(aKey.Length() % hashBytes != 0) //round up if mod !=0

		{

		l+=1;

		}

	TUint r = aKey.Length() - (l-1) * hashBytes; //r == length of last block

	HBufC8* TiTemp = HBufC8::NewLC(hashBytes);

	TUint32* Ti = (TUint32*)(TiTemp->Ptr());

	aKey.SetLength(0); //we've already saved the length we want

	HBufC8* STemp = HBufC8::NewLC(aSalt.Length() + sizeof(TUint32));

	TUint32* S = (TUint32*)(STemp->Ptr());

	HBufC8* UiTemp = HBufC8::NewLC(hashBytes);

	TUint32* Ui = (TUint32*)(UiTemp->Ptr());

	const TUint32* salt = (TUint32*)(aSalt.Ptr());

	TUint saltBytes = aSalt.Length();

	for(TUint i = 1; i<=l; i++)

		{

		F(*hmac, Ti, S, Ui, hashBytes, salt, saltBytes, c, i);

		if(i == l)

			aKey.Append((TUint8*)Ti, r);

		else 

			aKey.Append((TUint8*)Ti, hashBytes);

		}

	CleanupStack::PopAndDestroy(UiTemp);

	CleanupStack::PopAndDestroy(STemp);

	CleanupStack::PopAndDestroy(TiTemp);

	CleanupStack::PopAndDestroy(hmac);

	}

void TPKCS5KDF::F(CMessageDigest& aDigest, TUint32* aAccumulator, 

	TUint32* S, TUint32* Ui, TUint aHashBytes, const TUint32* aSalt, 

	TUint aSaltBytes, TUint c, TUint i)

	{

	TUint8 itmp[4];

	itmp[0] = (TUint8)((i >> 24) & 0xff);

	itmp[1] = (TUint8)((i >> 16) & 0xff);

	itmp[2] = (TUint8)((i >> 8) & 0xff);

	itmp[3] = (TUint8)(i & 0xff);

	TUint8* endOfS = Mem::Copy(S, aSalt, aSaltBytes);

	Mem::Copy((TUint32*)endOfS, (TUint32*)&itmp, 4);

	TPtr8 sptr((TUint8*)S, aSaltBytes+4);

	sptr.SetLength(aSaltBytes+4);

	Mem::Copy(aAccumulator, (TUint32*)((aDigest.Final(sptr)).Ptr()),aHashBytes);

	Mem::Copy(Ui, aAccumulator, aHashBytes);

	for(TUint j=1; j<c; j++)

		{

		TPtr8 uiptr((TUint8*)Ui, aHashBytes);

		uiptr.SetLength(aHashBytes);

		Mem::Copy(Ui, (TUint32*)((aDigest.Final(uiptr)).Ptr()), aHashBytes);

		XORString(Ui, aAccumulator, aHashBytes);

		}

	}

inline void TPKCS5KDF::XORString(const TUint32* aOp1, TUint32* aOp2,

	TUint aLength)

	{

	const TUint32* i = aOp1;

	//this will overflow the whole final word if aLength % 4 != 0 

	//but I can't see this mattering cuz all memory allocation is on a word by word basis

	//i don't want to do this byte by byte as it'll be way slower

	//also, every sane digest is going to be a multiple of 4 -- so this isn't a problem

	for( ; aOp1 != (TUint32*)((TUint8*)i + aLength); )

		{

			*aOp2++ ^= *aOp1++;	

		}

	}