/*

* Copyright (c) 2006-2009 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: 

*

*/

#include "dsaverifyimpl.h"

#include "pluginconfig.h"

using namespace SoftwareCrypto;

// Implementation of CDSAVerifierImpl

CDSAVerifierImpl* CDSAVerifierImpl::NewL(const CKey& aKey)

	{

	CDSAVerifierImpl* self = CDSAVerifierImpl::NewLC(aKey);

	CleanupStack::Pop(self);

	return self;

	}

CDSAVerifierImpl* CDSAVerifierImpl::NewLC(const CKey& aKey)

	{

	CDSAVerifierImpl* self = new(ELeave) CDSAVerifierImpl();

	CleanupStack::PushL(self);

	self->ConstructL(aKey);

	return self;

	}

CDSAVerifierImpl::CDSAVerifierImpl() 

	{

	}

CDSAVerifierImpl::~CDSAVerifierImpl()

	{

	}

void CDSAVerifierImpl::ConstructL(const CKey& aKey)

	{

	CVerifierImpl::ConstructL(aKey);

	}

CExtendedCharacteristics* CDSAVerifierImpl::CreateExtendedCharacteristicsL()

	{

	// All Symbian software plug-ins have unlimited concurrency, cannot be reserved

	// for exclusive use and are not CERTIFIED to be standards compliant.

	return CExtendedCharacteristics::NewL(KMaxTInt, EFalse);

	}

const CExtendedCharacteristics* CDSAVerifierImpl::GetExtendedCharacteristicsL()

	{

	return CDSAVerifierImpl::CreateExtendedCharacteristicsL();

	}

TUid CDSAVerifierImpl::ImplementationUid() const

	{

	return KCryptoPluginDsaVerifierUid;

	}

void CDSAVerifierImpl::SetKeyL(const CKey& aPublicKey)

	{

	DoSetKeyL(aPublicKey);

	Reset();	

	}

TInt CDSAVerifierImpl::GetMaximumInputLengthL() const

	{

	return KSha1HashLength;

	}

void CDSAVerifierImpl::VerifyL(const TDesC8& aInput, const CCryptoParams& aSignature, TBool& aVerificationResult)

	{

	//Retrieve the parameter Q from the key	

	const TInteger& tQ=iKey->GetBigIntL(KDsaKeyParameterQUid);

	//see HAC 11.56 or DSS section 6

	//I'll follow HAC as I like the description better

	// a) Obtain A's authenticate public key

	// b) Verify that 0 < r < q and 0 < s < q; if not reject signature

	//Retrieve the R&S in DSA signature from the array

	const TInteger& tR=aSignature.GetBigIntL(KDsaSignatureParameterRUid);

	const TInteger& tS=aSignature.GetBigIntL(KDsaSignatureParameterSUid);

	if (tR <= 0 || tR >= tQ)

		{

		aVerificationResult=EFalse;

		return;

		}

	if (tS <= 0 || tS >= tQ)

		{

		aVerificationResult=EFalse;

		return;

		}

	// c) Compute w = s^(-1) mod q and h(m)

	RInteger w = tS.InverseModL(tQ);

	CleanupStack::PushL(w);

	// Note that in order to be interoperable, compliant with the DSS, and

	// secure, aInput must be the result of a SHA-1 hash

	RInteger hm = RInteger::NewL(aInput);

	CleanupStack::PushL(hm);

	// d) Compute u1 = w * hm mod q and u2 = r * w mod q

	RInteger u1 = TInteger::ModularMultiplyL(w, hm, tQ);

	CleanupStack::PushL(u1);

	RInteger u2 = TInteger::ModularMultiplyL(tR, w, tQ);

	CleanupStack::PushL(u2);

	// e) Compute v = ((g^u1 * y^u2) mod p) mod q

	const TInteger& tG=iKey->GetBigIntL(KDsaKeyParameterGUid);

	const TInteger& tY=iKey->GetBigIntL(KDsaKeyParameterYUid);

	const TInteger& tP=iKey->GetBigIntL(KDsaKeyParameterPUid);

	RInteger temp = TInteger::ModularExponentiateL(tG, u1, tP);

	CleanupStack::PushL(temp);

	RInteger temp1 = TInteger::ModularExponentiateL(tY, u2, tP);

	CleanupStack::PushL(temp1);

	RInteger v = TInteger::ModularMultiplyL(temp, temp1, tP);

	CleanupStack::PushL(v);

	v %= tQ;

	// f) Accept the signature if v == r

	if(v == tR)

		{

		aVerificationResult = ETrue;

		}

	CleanupStack::PopAndDestroy(7, &w);

	}

// Methods which are not supported can be excluded from the coverage.

#ifdef _BullseyeCoverage

#pragma suppress_warnings on

#pragma BullseyeCoverage off

#pragma suppress_warnings off

#endif

void CDSAVerifierImpl::InverseSignL(HBufC8*& /*aOutput*/, const CCryptoParams& /*aSignature*/)

	{

	// Override in subclass

	User::Leave(KErrNotSupported);

	}