GOG_SignatureCheckBypass

This bypasses the GOG's (Good Old Games) signature checks.

How it works

We force WinVerifyTrust to succeed, this way we don't directly have to patch GOG's own code, which they have more control over. Reversed signature checking:

// #STR: "getValidFileSignature failed closing WinVerifyTrust with e, "getValidFileSignature failed during WinVerifyTrust with er
bool __stdcall getValidFileSignature(int a1)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  v10[1] = a1;
  pWVTData[6] = v10;
  v10[0] = 16;
  v10[2] = 0;
  v10[3] = 0;
  pgActionID.Data1 = 0xAAC56B;
  *&pgActionID.Data2 = 0x11D0CD44;
  *pgActionID.Data4 = 0xC000C28C;
  *&pgActionID.Data4[4] = 0xEE95C24F;
  v7 = 0;
  v9 = 0;
  pWVTData[0] = 52;
  pWVTData[1] = 0;
  pWVTData[2] = 0;
  pWVTData[3] = 2;
  pWVTData[4] = 0;
  pWVTData[5] = 1;
  v4 = 1;
  v5 = 0;
  v6 = 0;
  v8 = 0;
  nTrustStatus = WinVerifyTrust(0, &pgActionID, pWVTData);
  bTrust = nTrustStatus == 0;
  if ( nTrustStatus )
  {
    LastError = GetLastError();
    sub_4F0D10(
      "getValidFileSignature failed during WinVerifyTrust with error {} (detail code: {}).",
      83,
      &nTrustStatus,
      &LastError);
  }
  v4 = 2;
  nTrustStatus = WinVerifyTrust(0, &pgActionID, pWVTData);
  if ( nTrustStatus )
  {
    LastError = GetLastError();
    sub_4F0D10(
      "getValidFileSignature failed closing WinVerifyTrust with error {}, (detail code: {}).",
      85,
      &nTrustStatus,
      &LastError);
  }
  return bTrust;
}

Extra info

I found a function which lists all signatures that they allow, you can find them here.