text: /*
  	Copyright (c) 2009-2010 Christopher A. Taylor.  All rights reserved.
  
  	Redistribution and use in source and binary forms, with or without
  	modification, are permitted provided that the following conditions are met:
  
  	* Redistributions of source code must retain the above copyright notice,
  	  this list of conditions and the following disclaimer.
  	* Redistributions in binary form must reproduce the above copyright notice,
  	  this list of conditions and the following disclaimer in the documentation
  	  and/or other materials provided with the distribution.
  	* Neither the name of LibCat nor the names of its contributors may be used
  	  to endorse or promote products derived from this software without
  	  specific prior written permission.
  
  	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  	AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  	IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  	ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  	LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  	CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  	SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  	INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  	CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  	ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  	POSSIBILITY OF SUCH DAMAGE.
  */
  
  #include <cat/crypt/tunnel/KeyAgreementInitiator.hpp>
  #include <cat/crypt/SecureCompare.hpp>
  #include <cat/port/AlignedAlloc.hpp>
  using namespace cat;
  
  bool KeyAgreementInitiator::AllocateMemory()
  {
      FreeMemory();
  
      B = new (Aligned::ii) Leg[KeyLegs * 17];
      a = B + KeyLegs*4;
      A = a + KeyLegs;
      hB = A + KeyLegs*4;
  	A_neutral = hB + KeyLegs*4;
  	B_neutral = A_neutral + KeyLegs*2;
  
      return !!B;
  }
  
  void KeyAgreementInitiator::FreeMemory()
  {
      if (B)
      {
          CAT_CLR(a, KeyBytes);
          Aligned::Delete(B);
          B = 0;
      }
  
  	if (G_MultPrecomp)
  	{
  		Aligned::Delete(G_MultPrecomp);
  		G_MultPrecomp = 0;
   	}
  
  	if (B_MultPrecomp)
  	{
  		Aligned::Delete(B_MultPrecomp);
  		B_MultPrecomp = 0;
  	}
  
  	if (Y_MultPrecomp)
  	{
  		Aligned::Delete(Y_MultPrecomp);
  		Y_MultPrecomp = 0;
  	}
  
  	if (I_private)
  	{
  		Aligned::Delete(I_private);
  		I_private = 0;
  	}
  
  	if (I_public)
  	{
  		Aligned::Delete(I_public);
  		I_public = 0;
  	}
  }
  
  KeyAgreementInitiator::KeyAgreementInitiator()
  {
      B = 0;
      G_MultPrecomp = 0;
      B_MultPrecomp = 0;
      Y_MultPrecomp = 0;
  	I_private = 0;
  	I_public = 0;
  }
  
  KeyAgreementInitiator::~KeyAgreementInitiator()
  {
      FreeMemory();
  }
  
  void KeyAgreementInitiator::SecureErasePrivateKey()
  {
  	if (B) CAT_CLR(a, KeyBytes);
  }
  
  bool KeyAgreementInitiator::Initialize(BigTwistedEdwards *math, const u8 *responder_public_key, int public_bytes)
  {
  #if defined(CAT_USER_ERROR_CHECKING)
  	if (!math) return false;
  #endif
  
  	int bits = math->RegBytes() * 8;
  
      // Validate and accept number of bits
      if (!KeyAgreementCommon::Initialize(bits))
          return false;
  
      // Allocate memory space for the responder's key pair and generator point
      if (!AllocateMemory())
          return false;
  
      // Verify that inputs are of the correct length
      if (public_bytes != KeyBytes*2) return false;
  
  	// Precompute a table for multiplication
  	G_MultPrecomp = math->PtMultiplyPrecompAlloc(6);
      if (!G_MultPrecomp) return false;
      math->PtMultiplyPrecomp(math->GetGenerator(), 6, G_MultPrecomp);
  
      // Unpack the responder's public key
      if (!math->LoadVerifyAffineXY(responder_public_key, responder_public_key + KeyBytes, B))
          return false;
  
  	// Verify public point is not identity element
  	if (math->IsAffineIdentity(B))
  		return false;
  
  	memcpy(B_neutral, responder_public_key, KeyBytes*2);
  
  	// Precompute a table for multiplication
  	B_MultPrecomp = math->PtMultiplyPrecompAlloc(6);
  	if (!B_MultPrecomp) return false;
  	math->PtUnpack(B);
      math->PtMultiplyPrecomp(B, 6, B_MultPrecomp);
  
      // hB = h * B for small subgroup attack resistance
      math->PtDoubleZ1(B, hB);
      math->PtEDouble(hB, hB);
  
      return true;
  }
  
  bool KeyAgreementInitiator::SetIdentity(BigTwistedEdwards *math,
  										const u8 *initiator_public_key, int public_bytes,
  										const u8 *initiator_private_key, int private_bytes)
  {
  #if defined(CAT_USER_ERROR_CHECKING)
  	if (!math || public_bytes != KeyBytes*2 || private_bytes != KeyBytes) return false;
  #endif
  
  	Leg *I_temp = math->Get(0);
  
  	// Unpack the initiator's public key
  	if (!math->LoadVerifyAffineXY(initiator_public_key, initiator_public_key + KeyBytes, I_temp))
  		return false;
  
  	// Verify public point is not identity element
  	if (math->IsAffineIdentity(I_temp))
  		return false;
  
  	// Allocate space for private key if needed
  	if (!I_private)
  	{
  		I_private = (Leg*)Aligned::Acquire(KeyBytes);
  		if (!I_private) return false;
  	}
  
  	// Allocate space for public key if needed
  	if (!I_public)
  	{
  		I_public = (Leg*)Aligned::Acquire(KeyBytes*2);
  		if (!I_public) return false;
  	}
  
  	// Copy the endian-neutral public key
  	memcpy(I_public, initiator_public_key, KeyBytes*2);
  
  	// Load the private key
  	math->Load(initiator_private_key, KeyBytes, I_private);
  
  	return true;
  }
  
  bool KeyAgreementInitiator::GenerateChallenge(BigTwistedEdwards *math, FortunaOutput *csprng,
  											  u8 *initiator_challenge, int challenge_bytes)
  {
  #if defined(CAT_USER_ERROR_CHECKING)
  	// Verify that inputs are of the correct length
  	if (!math || !csprng || challenge_bytes != KeyBytes*2) return false;
  #endif
  
      // a = initiator private key
  	GenerateKey(math, csprng, a);
  
      // A = a * G
      math->PtMultiply(G_MultPrecomp, 6, a, 0, A);
      math->PtNormalize(A, A);
  
      math->SaveAffineXY(A, initiator_challenge, initiator_challenge + KeyBytes);
  
  	memcpy(A_neutral, initiator_challenge, KeyBytes*2);
  
      return true;
  }
  
  bool KeyAgreementInitiator::ProcessAnswer(BigTwistedEdwards *math,
  										  const u8 *responder_answer, int answer_bytes,
                                            Skein *key_hash)
  {
  #if defined(CAT_USER_ERROR_CHECKING)
  	// Verify that inputs are of the correct length
  	if (!math || answer_bytes < KeyBytes*3) return false;
  #endif
  
      Leg *Y = math->Get(0);
      Leg *S = math->Get(4);
      Leg *T = math->Get(8);
      Leg *hY = math->Get(12);
      Leg *ah = math->Get(16);
  
      // Load the responder's affine point Y
      if (!math->LoadVerifyAffineXY(responder_answer, responder_answer + KeyBytes, Y))
          return false;
  
  	// Verify the point is not the additive identity (will never happen unless being attacked)
  	if (math->IsAffineIdentity(Y))
  		return false;
  
      // hY = h * Y for small subgroup attack resistance
      math->PtDoubleZ1(Y, hY);
      math->PtEDouble(hY, hY);
  
  	// Precompute a table for multiplication
  	if (!Y_MultPrecomp)
  	{
  		Y_MultPrecomp = math->PtMultiplyPrecompAlloc(6);
  		if (!Y_MultPrecomp) return false;
  	}
  
  	// S = H(A,B,Y,r)
  	if (!key_hash->BeginKey(KeyBits))
  		return false;
  	key_hash->Crunch(A_neutral, KeyBytes*2); // A
  	key_hash->Crunch(B_neutral, KeyBytes*2); // B
  	key_hash->Crunch(responder_answer, KeyBytes*3); // Y,r
  	key_hash->End();
  	key_hash->Generate(S, KeyBytes);
  	math->Load(S, KeyBytes, S);
  
  	// Insure S >= 1000
  	if (math->LessX(S, 1000))
  		return false;
  
  	// ah = a*h
  	if (math->Double(a, ah))
  		math->Subtract(ah, math->GetCurveQ(), ah);
  	if (math->Double(ah, ah))
  		math->Subtract(ah, math->GetCurveQ(), ah);
  
  	// T = AffineX(ah * B + S*a * hY)
  	math->MulMod(S, a, math->GetCurveQ(), S);
  	math->PtMultiplyPrecomp(hY, 6, Y_MultPrecomp);
  	math->PtSiMultiply(B_MultPrecomp, Y_MultPrecomp, 6, ah, 0, S, 0, T);
  	math->SaveAffineX(T, T);
  
  	// k = H(d,T)
  	if (!key_hash->BeginKDF())
  		return false;
  	key_hash->Crunch(T, KeyBytes);
  	key_hash->End();
  
  	// Verify initiator proof of key
  	Skein mac;
  
  	if (!mac.SetKey(key_hash) || !mac.BeginMAC()) return false;
  	mac.CrunchString("shfolder.dll");
  	mac.End();
  
  	u8 expected[KeyAgreementCommon::MAX_BYTES];
  	mac.Generate(expected, KeyBytes);
  
  	return SecureEqual(expected, responder_answer + KeyBytes * 3, KeyBytes);
  }
  
  bool KeyAgreementInitiator::ProcessAnswerWithIdentity(BigTwistedEdwards *math, FortunaOutput *csprng,
  													  const u8 *responder_answer, int answer_bytes,
  													  Skein *key_hash,
  													  u8 *identity_proof, int proof_bytes)
  {
  	// Process answer first and fail out if needed
  	if (!ProcessAnswer(math, responder_answer, answer_bytes, key_hash))
  		return false;
  
  #if defined(CAT_USER_ERROR_CHECKING)
  	// Verify that inputs are of the correct length
  	if (!csprng || proof_bytes != KeyBytes*5) return false;
  #endif
  
  	// Fill endian-neutral public key for initiator
  	memcpy(identity_proof, I_public, KeyBytes * 2);
  
  	// Fill initiator's random nonce
  	csprng->Generate(identity_proof + KeyBytes * 2, KeyBytes);
  
  	// Sign() code from KeyAgreementResponder.cpp:
  
  	Leg *k = math->Get(0);
  	Leg *K = math->Get(1);
  	Leg *e = math->Get(5);
  	Leg *s = math->Get(6);
  
  	do {
  
  		do {
  
  			// k = ephemeral key
  			GenerateKey(math, csprng, k);
  
  			// K = k * G
  			math->PtMultiply(G_MultPrecomp, 6, k, 0, K);
  			math->SaveAffineX(K, K);
  
  			// e = H(IRN || RRN || K)
  			Skein H;
  
  			if (!H.BeginKey(KeyBits)) return false;
  			H.Crunch(identity_proof + KeyBytes * 2, KeyBytes); // client random number
  			H.Crunch(responder_answer + KeyBytes * 2, KeyBytes); // server random number
  			H.Crunch(K, KeyBytes);
  			H.End();
  			H.Generate(identity_proof + KeyBytes * 3, KeyBytes);
  
  			math->Load(identity_proof + KeyBytes * 3, KeyBytes, e);
  
  			// e = e (mod q), for checking if it is congruent to q
  			while (!math->Less(e, math->GetCurveQ()))
  				math->Subtract(e, math->GetCurveQ(), e);
  
  		} while (math->IsZero(e));
  
  		// s = I_private * e (mod q)
  		math->MulMod(I_private, e, math->GetCurveQ(), s);
  
  		// s = -s (mod q)
  		if (!math->IsZero(s)) math->Subtract(math->GetCurveQ(), s, s);
  
  		// s = s + k (mod q)
  		if (math->Add(s, k, s))
  			while (!math->Subtract(s, math->GetCurveQ(), s));
  		while (!math->Less(s, math->GetCurveQ()))
  			math->Subtract(s, math->GetCurveQ(), s);
  
  	} while (math->IsZero(s));
  
  	math->Save(s, identity_proof + KeyBytes * 4, KeyBytes);
  
  	// Erase the ephemeral secret from memory
  	math->CopyX(0, k);
  
  	/*
  		Format of identity buffer:
  
  		256-bit security: [Initiator Public Key] (64) || [Initiator Random Number] (32) || [Signature] (64)
  	*/
  
  	return true;
  }
  
  bool KeyAgreementInitiator::Verify(BigTwistedEdwards *math,
  								   const u8 *message, int message_bytes,
  								   const u8 *signature, int signature_bytes)
  {
  #if defined(CAT_USER_ERROR_CHECKING)
  	// Verify that inputs are of the correct length
  	if (!math || signature_bytes != KeyBytes*2) return false;
  #endif
  
      Leg *e = math->Get(0);
      Leg *s = math->Get(1);
      Leg *Kp = math->Get(2);
      Leg *ep = math->Get(6);
  
  	// Load e, s from signature
  	math->Load(signature, KeyBytes, e);
  	math->Load(signature + KeyBytes, KeyBytes, s);
  
  	// e = e (mod q), for checking if it is congruent to q
  	while (!math->Less(e, math->GetCurveQ()))
  		math->Subtract(e, math->GetCurveQ(), e);
  
  	// Check e, s are in the range [1,q-1]
  	if (math->IsZero(e) || math->IsZero(s) ||
  		!math->Less(e, math->GetCurveQ()) ||
  		!math->Less(s, math->GetCurveQ()))
  	{
  		return false;
  	}
  
  	// K' = s*G + e*B
  	math->PtSiMultiply(G_MultPrecomp, B_MultPrecomp, 6, s, 0, e, 0, Kp);
  	math->SaveAffineX(Kp, Kp);
  
  	// e' = H(M || K')
  	Skein H;
  	if (!H.BeginKey(KeyBits)) return false;
  	H.Crunch(message, message_bytes);
  	H.Crunch(Kp, KeyBytes);
  	H.End();
  	H.Generate(ep, KeyBytes);
  
  	// Verify that e' == e
  	return SecureEqual(signature, ep, KeyBytes);
  }
  