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/*
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* Copyright (c) 2005-2009 Nokia Corporation and/or its subsidiary(-ies).
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* All rights reserved.
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* This component and the accompanying materials are made available
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* under the terms of the License "Eclipse Public License v1.0"
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* which accompanies this distribution, and is available
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* at the URL "http://www.eclipse.org/legal/epl-v10.html".
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*
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* Initial Contributors:
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* Nokia Corporation - initial contribution.
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*
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* Contributors:
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*
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* Description:
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*
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*/
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/**
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@file
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*/
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#include "pkcs5kdf.h"
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/* Before complaining about the variable names in this file,
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* read the pkcs5 spec and all will become clear.
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*/
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EXPORT_C void TPKCS5KDF::DeriveKeyL(TDes8& aKey, const TDesC8& aPasswd, const TDesC8& aSalt,
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const TUint aIterations)
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{
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CSHA1* sha1 = CSHA1::NewL();
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CleanupStack::PushL(sha1);
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CHMAC* hmac = CHMAC::NewL(aPasswd, sha1);
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CleanupStack::Pop(sha1); //hmac now owns it
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CleanupStack::PushL(hmac);
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TUint hashBytes = hmac->HashSize();
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TUint c = aIterations;
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TUint l = aKey.Length() / hashBytes;
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if(aKey.Length() % hashBytes != 0) //round up if mod !=0
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{
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l+=1;
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}
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TUint r = aKey.Length() - (l-1) * hashBytes; //r == length of last block
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HBufC8* TiTemp = HBufC8::NewLC(hashBytes);
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TUint32* Ti = (TUint32*)(TiTemp->Ptr());
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aKey.SetLength(0); //we've already saved the length we want
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HBufC8* STemp = HBufC8::NewLC(aSalt.Length() + sizeof(TUint32));
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TUint32* S = (TUint32*)(STemp->Ptr());
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HBufC8* UiTemp = HBufC8::NewLC(hashBytes);
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TUint32* Ui = (TUint32*)(UiTemp->Ptr());
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const TUint32* salt = (TUint32*)(aSalt.Ptr());
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TUint saltBytes = aSalt.Length();
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for(TUint i = 1; i<=l; i++)
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{
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F(*hmac, Ti, S, Ui, hashBytes, salt, saltBytes, c, i);
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if(i == l)
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aKey.Append((TUint8*)Ti, r);
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else
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aKey.Append((TUint8*)Ti, hashBytes);
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}
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CleanupStack::PopAndDestroy(UiTemp);
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CleanupStack::PopAndDestroy(STemp);
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CleanupStack::PopAndDestroy(TiTemp);
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CleanupStack::PopAndDestroy(hmac);
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}
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void TPKCS5KDF::F(CMessageDigest& aDigest, TUint32* aAccumulator,
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TUint32* S, TUint32* Ui, TUint aHashBytes, const TUint32* aSalt,
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TUint aSaltBytes, TUint c, TUint i)
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{
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TUint8 itmp[4];
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itmp[0] = (TUint8)((i >> 24) & 0xff);
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itmp[1] = (TUint8)((i >> 16) & 0xff);
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itmp[2] = (TUint8)((i >> 8) & 0xff);
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itmp[3] = (TUint8)(i & 0xff);
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TUint8* endOfS = Mem::Copy(S, aSalt, aSaltBytes);
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Mem::Copy((TUint32*)endOfS, (TUint32*)&itmp, 4);
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TPtr8 sptr((TUint8*)S, aSaltBytes+4);
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sptr.SetLength(aSaltBytes+4);
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Mem::Copy(aAccumulator, (TUint32*)((aDigest.Final(sptr)).Ptr()),aHashBytes);
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Mem::Copy(Ui, aAccumulator, aHashBytes);
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for(TUint j=1; j<c; j++)
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{
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TPtr8 uiptr((TUint8*)Ui, aHashBytes);
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uiptr.SetLength(aHashBytes);
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Mem::Copy(Ui, (TUint32*)((aDigest.Final(uiptr)).Ptr()), aHashBytes);
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XORString(Ui, aAccumulator, aHashBytes);
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}
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}
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inline void TPKCS5KDF::XORString(const TUint32* aOp1, TUint32* aOp2,
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TUint aLength)
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{
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const TUint32* i = aOp1;
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//this will overflow the whole final word if aLength % 4 != 0
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//but I can't see this mattering cuz all memory allocation is on a word by word basis
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//i don't want to do this byte by byte as it'll be way slower
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//also, every sane digest is going to be a multiple of 4 -- so this isn't a problem
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for( ; aOp1 != (TUint32*)((TUint8*)i + aLength); )
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{
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*aOp2++ ^= *aOp1++;
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}
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}
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