message: Add check for canonical block signature
diff: @@ -3667,6 +3667,15 @@ static bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidation
  return true;
  }
  +bool static IsCanonicalBlockSignature(const CBlock* pblock, bool checkLowS)
  +{
  + if (pblock->IsProofOfWork()) {
  + return pblock->vchBlockSig.empty();
  + }
  +
  + return checkLowS ? IsLowDERSignature(pblock->vchBlockSig, NULL, false) : IsDERSignature(pblock->vchBlockSig, NULL, false);
  +}
  +
  bool ProcessNewBlock(const CChainParams& chainparams, const std::shared_ptr<const CBlock> pblock, bool fForceProcessing, bool *fNewBlock)
  {
  {
  