/*

* Copyright (c) 2007-2009 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: 

* DSA Keypair implementation

* DSA keypair generation implementation

*

*/

/**

 @file

*/

#include "dsakeypairgenimpl.h"

#include "pluginconfig.h"

#include "keypair.h"

#include "common/inlines.h"    // For TClassSwap

#include "mont.h"

#include "sha1impl.h"

#include <random.h>

const TUint KShaSize = 20;

const TUint KMinPrimeLength = 512;

const TUint KMaxPrimeLength = 1024;

const TUint KPrimeLengthMultiple = 64;

using namespace SoftwareCrypto;

/* CDSAPrimeCertificate */

CDSAPrimeCertificate* CDSAPrimeCertificate::NewL(const TDesC8& aSeed, TUint aCounter)

	{

	CDSAPrimeCertificate* self = NewLC(aSeed, aCounter);

	CleanupStack::Pop();

	return self;

	}

CDSAPrimeCertificate* CDSAPrimeCertificate::NewLC(const TDesC8& aSeed, TUint aCounter)

	{

	CDSAPrimeCertificate* self = new(ELeave) CDSAPrimeCertificate(aCounter);

	CleanupStack::PushL(self);

	self->ConstructL(aSeed);

	return self;

	}

const TDesC8& CDSAPrimeCertificate::Seed() const

	{

	return *iSeed;

	}

TUint CDSAPrimeCertificate::Counter() const

	{

	return iCounter;

	}

CDSAPrimeCertificate::~CDSAPrimeCertificate() 

	{

	delete const_cast<HBufC8*>(iSeed);

	}

void CDSAPrimeCertificate::ConstructL(const TDesC8& aSeed)

	{

	iSeed = aSeed.AllocL();

	}

CDSAPrimeCertificate::CDSAPrimeCertificate(TUint aCounter) 

	: iCounter(aCounter)

	{

	}

CDSAPrimeCertificate::CDSAPrimeCertificate() 

	{

	}

/* CDSAKeyPairGenImpl */

CDSAKeyPairGenImpl::CDSAKeyPairGenImpl()

	{

	}

CDSAKeyPairGenImpl::~CDSAKeyPairGenImpl()

	{

	delete iPrimeCertificate;

	}

CDSAKeyPairGenImpl* CDSAKeyPairGenImpl::NewL()

	{

	CDSAKeyPairGenImpl* self = CDSAKeyPairGenImpl::NewLC();

	CleanupStack::Pop(self);

	return self;

	}

CDSAKeyPairGenImpl* CDSAKeyPairGenImpl::NewLC()

	{

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

	CleanupStack::PushL(self);

	self->ConstructL();

	return self;

	}

void CDSAKeyPairGenImpl::ConstructL(void)

	{

	CKeyPairGenImpl::ConstructL();

	}

CExtendedCharacteristics* CDSAKeyPairGenImpl::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* CDSAKeyPairGenImpl::GetExtendedCharacteristicsL()

	{

	return CDSAKeyPairGenImpl::CreateExtendedCharacteristicsL();

	}

TUid CDSAKeyPairGenImpl::ImplementationUid() const

	{

	return KCryptoPluginDsaKeyPairGenUid;

	}

void CDSAKeyPairGenImpl::Reset()

	{

	// does nothing in this plugin

	}

TBool CDSAKeyPairGenImpl::ValidPrimeLength(TUint aPrimeBits)

	{

	return (aPrimeBits >= KMinPrimeLength &&

			aPrimeBits <= KMaxPrimeLength &&

			aPrimeBits % KPrimeLengthMultiple == 0);

	}

TBool CDSAKeyPairGenImpl::GeneratePrimesL(const TDesC8& aSeed,

										 TUint& aCounter, 

										 RInteger& aP, 

										 TUint aL, 

										 RInteger& aQ, 

										 TBool aUseInputCounter)

	{

	//This follows the steps in FIPS 186-2 

	//See DSS Appendix 2.2

	//Note. Step 1 is performed prior to calling GeneratePrimesL, so that this

	//routine can be used for both generation and validation.

	//Step 1.  Choose an arbitrary sequence of at least 160 bits and call it

	//SEED.  Let g be the length of SEED in bits.

	if(!ValidPrimeLength(aL))

		{

		User::Leave(KErrNotSupported);

		}

	CSHA1Impl* sha1 = CSHA1Impl::NewL();

	CleanupStack::PushL(sha1);

	HBufC8* seedBuf = aSeed.AllocLC();

	TPtr8 seed = seedBuf->Des();

	TUint gBytes = aSeed.Size();

	//Note that the DSS's g = BytesToBits(gBytes) ie. the number of random bits

	//in the seed.  

	//This function has made the assumption (for ease of computation) that g%8

	//is 0.  Ie the seed is a whole number of random bytes.

	TBuf8<KShaSize> U; 

	TBuf8<KShaSize> temp; 

	const TUint n = (aL-1)/160;

	const TUint b = (aL-1)%160;

	HBufC8* Wbuf = HBufC8::NewMaxLC((n+1) * KShaSize);

	TUint8* W = const_cast<TUint8*>(Wbuf->Ptr());

	U.Copy(sha1->Final(seed));

	//Step 2. U = SHA-1[SEED] XOR SHA-1[(SEED+1) mod 2^g]

	for(TInt i=gBytes - 1, carry=ETrue; i>=0 && carry; i--)

		{

		//!++(TUint) adds one to the current word which if it overflows to zero

		//sets carry to 1 thus letting the loop continue.  It's a poor man's

		//multi-word addition.  Swift eh?

		carry = !++(seed[i]);

		}

	temp.Copy(sha1->Final(seed));

	XorBuf(const_cast<TUint8*>(U.Ptr()), temp.Ptr(), KShaSize);

	//Step 3. Form q from U by setting the most significant bit (2^159)

	//and the least significant bit to 1.

	U[0] |= 0x80;

	U[KShaSize-1] |= 1;

	aQ = RInteger::NewL(U);

	CleanupStack::PushL(aQ);

	//Step 4. Use a robust primality testing algo to test if q is prime

	//The robust part is the calling codes problem.  This will use whatever

	//random number generator you set for the thread.  To attempt FIPS 186-2

	//compliance, set a FIPS 186-2 compliant RNG.

	if( !aQ.IsPrimeL() )

		{

		//Step 5. If not exit and get a new seed

		CleanupStack::PopAndDestroy(4, sha1);

		return EFalse;

		}

	TUint counterEnd = aUseInputCounter ? aCounter+1 : 4096;

	//Step 6. Let counter = 0 and offset = 2

	//Note 1. that the DSS speaks of SEED + offset + k because they always

	//refer to a constant SEED.  We update our seed as we go so the offset

	//variable has already been added to seed in the previous iterations.

	//Note 2. We've already added 1 to our seed, so the first time through this

	//the offset in DSS speak will be 2.

	for(TUint counter=0; counter < counterEnd; counter++)

		{

		//Step 7. For k=0, ..., n let

		// Vk = SHA-1[(SEED + offset + k) mod 2^g]

		//I'm storing the Vk's inside of a big W buffer.

		for(TUint k=0; k<=n; k++)

			{

			for(TInt i=gBytes-1, carry=ETrue; i>=0 && carry; i--)

				{

				carry = !++(seed[i]);

				}

			if(!aUseInputCounter || counter == aCounter)

				{

				TPtr8 Wptr(W+(n-k)*KShaSize, gBytes);

				Wptr.Copy(sha1->Final(seed));

				}

			}

		if(!aUseInputCounter || counter == aCounter)

			{

			//Step 8. Let W be the integer...  and let X = W + 2^(L-1)

			const_cast<TUint8&>((*Wbuf)[KShaSize - 1 - b/8]) |= 0x80;

			TPtr8 Wptr(W + KShaSize - 1 - b/8, aL/8, aL/8);

			RInteger X = RInteger::NewL(Wptr);

			CleanupStack::PushL(X);

			//Step 9. Let c = X mod 2q and set p = X - (c-1)

			RInteger twoQ = aQ.TimesL(TInteger::Two());

			CleanupStack::PushL(twoQ);

			RInteger c = X.ModuloL(twoQ);

			CleanupStack::PushL(c);

			--c;

			aP = X.MinusL(c);

			CleanupStack::PopAndDestroy(3, &X); //twoQ, c, X

			CleanupStack::PushL(aP);

			//Step 10 and 11: if p >= 2^(L-1) and p is prime

			if( aP.Bit(aL-1) && aP.IsPrimeL() )

				{

				aCounter = counter;

				CleanupStack::Pop(2, &aQ);

				CleanupStack::PopAndDestroy(3, sha1);

				return ETrue;

				}

			CleanupStack::PopAndDestroy(&aP);

			}

		}

	CleanupStack::PopAndDestroy(4, &sha1);

	return EFalse;

	}

void CDSAKeyPairGenImpl::GenerateKeyPairL(TInt aKeySize, 

										const CCryptoParams& aKeyParameters,

										CKeyPair*& aKeyPair)

	{

	//This is the first step of DSA prime generation.  The remaining steps are

	//performed in CDSAParameters::GeneratePrimesL

	//Step 1.  Choose an arbitrary sequence of at least 160 bits and call it

	//SEED.  Let g be the length of SEED in bits.	

	TBuf8<KShaSize> seed(KShaSize);

	TUint c;

	RInteger p;

	RInteger q;

	do 

		{

		GenerateRandomBytesL(seed);

		}

	while(!GeneratePrimesL(seed, c, p, aKeySize, q));

	//Double PushL will not fail as GeneratePrimesL uses the CleanupStack

	//(at least one push and pop ;)

	CleanupStack::PushL(p);

	CleanupStack::PushL(q);

	iPrimeCertificate = CDSAPrimeCertificate::NewL(seed, c);

	// aKeyParameters isn't const here anymore

	CCryptoParams& paramRef=const_cast<CCryptoParams&>(aKeyParameters);

	paramRef.AddL(c, KDsaKeyGenerationCounterUid);

	paramRef.AddL(seed, KDsaKeyGenerationSeedUid);

	CMontgomeryStructure* montP = CMontgomeryStructure::NewLC(p);

	--p;

	// e = (p-1)/q

	RInteger e = p.DividedByL(q);

	CleanupStack::PushL(e);

	--p; //now it's p-2 :)

	RInteger h;

	const TInteger* g = 0;

	do

		{

		// find a random h | 1 < h < p-1

		h = RInteger::NewRandomL(TInteger::Two(), p);

		CleanupStack::PushL(h);

		// g = h^e mod p

		g = &(montP->ExponentiateL(h, e));

		CleanupStack::PopAndDestroy(&h); 

		}

	while( *g <= TInteger::One() );

	CleanupStack::PopAndDestroy(&e);

	++p; //reincrement p to original value

	++p;

	RInteger g1 = RInteger::NewL(*g); //take a copy of montP's g

	CleanupStack::PushL(g1);

	--q;

	// select random x | 0 < x < q

	RInteger x = RInteger::NewRandomL(TInteger::One(), q);

	CleanupStack::PushL(x);

	++q;

	//

	// create the keys parameters

	CCryptoParams* privateKeyParameters = CCryptoParams::NewLC();

	privateKeyParameters->AddL(p, KDsaKeyParameterPUid);

	privateKeyParameters->AddL(q, KDsaKeyParameterQUid);

	privateKeyParameters->AddL(g1, KDsaKeyParameterGUid);

	privateKeyParameters->AddL(x, KDsaKeyParameterXUid);

	TKeyProperty privateKeyProperties = {KDSAKeyPairGeneratorUid, 

										 KCryptoPluginDsaKeyPairGenUid,

									     KDsaPrivateKeyUid, 

									     KNonEmbeddedKeyUid};

	CCryptoParams* publicKeyParameters = CCryptoParams::NewLC();

	publicKeyParameters->AddL(p, KDsaKeyParameterPUid);

	publicKeyParameters->AddL(q, KDsaKeyParameterQUid);

	publicKeyParameters->AddL(g1, KDsaKeyParameterGUid);

	RInteger y = RInteger::NewL(montP->ExponentiateL(*g, x));

	CleanupStack::PushL(y);

	publicKeyParameters->AddL(y, KDsaKeyParameterYUid);

	TKeyProperty publicKeyProperties = {KDSAKeyPairGeneratorUid,

										KCryptoPluginDsaKeyPairGenUid, 

										KDsaPublicKeyUid,

										KNonEmbeddedKeyUid};

	//

	// create the private key

	//

	CKey* privateKey = CKey::NewL(privateKeyProperties, *privateKeyParameters);

	CleanupStack::PushL(privateKey);

	//

	// create the public key

	//

	CKey* publicKey = CKey::NewL(publicKeyProperties, *publicKeyParameters);

	CleanupStack::PushL(publicKey);

	aKeyPair = CKeyPair::NewL(publicKey, privateKey);

	//publicKey, publicKeyParameters, y, privateKey, privateKeyParameters, x, g1, montP, q, p

	CleanupStack::Pop(2, privateKey);

	CleanupStack::PopAndDestroy(8, &p);	

	}