/*

 * 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++;	

 		}

 	}