//***************************************************
//
// VerifyCertSigner
// Verifies certificate issuer and signature
//
// Copyright (C) 2004.  Michel I. Gallant
//
//
//***************************************************

using System;
using System.IO;
using System.Collections;
using System.Runtime.InteropServices;
using System.Security.Cryptography.X509Certificates;
using System.ComponentModel;

public class Win32 {

 [DllImport("crypt32.dll", CharSet=CharSet.Auto, SetLastError=true)]
    public static extern IntPtr CertCreateCertificateContext(
	uint dwCertEncodingType,
	byte[] pbCertEncoded,
	uint cbCertEncoded) ;


 [DllImport("crypt32.dll", CharSet=CharSet.Auto, SetLastError=true)]
    public static extern IntPtr CertOpenSystemStore(
	IntPtr hCryptProv,
	string storename) ;

 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern bool CertCloseStore(
	IntPtr hCertStore,
	uint dwFlags) ;


 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern IntPtr CertFindCertificateInStore(
	IntPtr hCertStore,
	uint dwCertEncodingType,
	uint dwFindFlags,
	uint dwFindType,
	[In, MarshalAs(UnmanagedType.LPWStr)]String pszFindString,
	IntPtr pPrevCertCntxt) ;



 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern IntPtr CertFindCertificateInStore(
	IntPtr hCertStore,
	uint dwCertEncodingType,
	uint dwFindFlags,
	uint dwFindType,
	IntPtr pCertNameBlob,
	IntPtr pPrevCertCntxt) ;



 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern bool CertFreeCertificateContext(
	IntPtr hCertStore) ;


 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern int CertGetPublicKeyLength(
	uint dwCertEncodingType,
	IntPtr pPublicKeyInfo) ;



 [DllImport("crypt32.dll", SetLastError=true)]
  public static extern bool CryptVerifyCertificateSignature(
	IntPtr hCryptProv,
	uint dwCertEncodingType,
	byte[] pbEncoded,	// binary DER cert data
	uint cbEncoded,
	IntPtr pPublicKey);    //PCERT_PUBLIC_KEY_INFO 

}



//--------  Win32 structs prototypes ---------------

 [StructLayout(LayoutKind.Sequential)]
  public struct CERT_CONTEXT
  {
	public uint dwCertEncodingType;  
	public IntPtr pbCertEncoded;  
	public int cbCertEncoded;  
	public IntPtr pCertInfo;  
	public IntPtr hCertStore;
  }



public class VerifyCertSigner {
 const string MY	= "my";
 const string ROOT	= "root";
 const string SUBCA	= "ca";	//Intermediate Certificate Authorities
 const string OTHERS	= "addressbook";

 const uint PKCS_7_ASN_ENCODING 	= 0x00010000;
 const uint X509_ASN_ENCODING 		= 0x00000001;
 const uint CERT_FIND_SUBJECT_STR	= 0x00080007;
 const uint CERT_FIND_SUBJECT_NAME	= 0x00020007;
 const uint CERT_FIND_ISSUER_NAME	= 0x00020004;

 static uint MY_ENCODING_TYPE 	= PKCS_7_ASN_ENCODING | X509_ASN_ENCODING ;
 static ArrayList searchStores = new ArrayList();



 public static void Main(string[] args){ 
  IntPtr hSysStore  = IntPtr.Zero;
  IntPtr hCertCntxt = IntPtr.Zero;
  IntPtr hIssuerCertCntxt = IntPtr.Zero;

  searchStores.Add(ROOT);
  searchStores.Add(SUBCA);
  searchStores.Add(OTHERS);
  searchStores.Add(MY);

	if(args.Length<2){
	 Console.WriteLine("Usage:  VerifyCertSigner  [certfile]  [certificate_store]");
	 return;
	 }
	String fname = args[0];
	if (!File.Exists(fname)){
	 Console.WriteLine("\nFile '" + fname + "' not found ");
	 return;
	}

	String searchStore = args[1].ToLower();
	if(!searchStores.Contains(searchStore)){    //check for alias certstore names
		if(searchStore.Equals("personal"))
			searchStore = "my";
		else if (searchStore.Equals("others") || searchStore.Equals("other people"))
			searchStore = "addressbook";
		else {
		 Console.WriteLine("Store  '{0}' not known", searchStore) ;
		 return;
		}
	}

    byte[] pcert = getCert(fname);  //binary DER encoded cert. data
    if(pcert == null)
	return;

  hCertCntxt = Win32.CertCreateCertificateContext(MY_ENCODING_TYPE, pcert, (uint)pcert.Length);
  if(hCertCntxt==IntPtr.Zero)
	{
	 Console.WriteLine("Couldn't create certificate context");
	 return;
	}


  Console.WriteLine("\nCreated certificate context from file {0}", fname);

  CERT_CONTEXT certcntxt = (CERT_CONTEXT)Marshal.PtrToStructure(hCertCntxt, typeof(CERT_CONTEXT));

  IntPtr certinfo = certcntxt.pCertInfo ;
  //---- Console.WriteLine("pCertInfo:\t0x{0:X}", certinfo);
  //---  Walk IntPtr offset in CERT_INFO to CERT_NAME_BLOB Issuer  (3 ints, 3 IntPtrs)
  IntPtr pIssuerName = (IntPtr)(3*4 + 3*IntPtr.Size + (int)certinfo);
  Console.WriteLine("Got IssuerName for certificate\n");



 //-----  Now search for issuer in searchStore with matching SubjectName  --------
 //----- The SubjectName of this issuer cert should match the IssuerName of hCertCntxt ---
  hSysStore = Win32.CertOpenSystemStore(IntPtr.Zero, searchStore) ;
  Console.WriteLine("Got handle for '{0}' store", searchStore);

 if(hSysStore != IntPtr.Zero)
 {
   hIssuerCertCntxt=Win32.CertFindCertificateInStore(
      hSysStore,
      MY_ENCODING_TYPE,
      0, 
      CERT_FIND_SUBJECT_NAME,
      pIssuerName ,
      IntPtr.Zero) ;

  if(hIssuerCertCntxt != IntPtr.Zero){
 	X509Certificate foundcert = new X509Certificate(hIssuerCertCntxt);
	Console.WriteLine("Found matching issuer certificate in '{0}' store", searchStore) ;
	Console.WriteLine("Issuer SubjectName:\t{0}", foundcert.GetName());
	Console.WriteLine("Issuer Serial No:\t{0}", foundcert.GetSerialNumberString());
	CERT_CONTEXT issuerCntxt = (CERT_CONTEXT)Marshal.PtrToStructure(hIssuerCertCntxt, typeof(CERT_CONTEXT));

	IntPtr issuercertinfo = issuerCntxt.pCertInfo ;
	//--- walk IntPtr offset in CERT_INFO to SubjectPublicKeyInfo structure (5 ints, 2 longs, 5 IntPtrs)
	IntPtr pPublicKeyinfo = (IntPtr)(9*4 + 5*IntPtr.Size + (int)issuercertinfo);
	//Console.WriteLine("Issuer Public key size: {0}", Win32.CertGetPublicKeyLength(MY_ENCODING_TYPE, pPublicKeyinfo)) ;

	Console.WriteLine("\nVerifying Issuer signature on certificate ...");

	if(Win32.CryptVerifyCertificateSignature(IntPtr.Zero, MY_ENCODING_TYPE, pcert, (uint)pcert.Length, pPublicKeyinfo))
		Console.WriteLine("******  Verified signature on certificate  *********");
	else
		Console.WriteLine("!!!!!!   FAILED to verify signature on certificate !!!!!!") ;  
   }
  else
    Console.WriteLine("Could not find issuer cert in '{0}' store matching  IssuerName in cert '{1}'", searchStore, fname);
 }

//-------  Clean Up  -----------
  if(hCertCntxt != IntPtr.Zero)
	Win32.CertFreeCertificateContext(hCertCntxt);
  if(hIssuerCertCntxt != IntPtr.Zero)
	Win32.CertFreeCertificateContext(hIssuerCertCntxt);
  if(hSysStore != IntPtr.Zero)
	Win32.CertCloseStore(hSysStore, 0) ;
 }



 private static byte[] getCert(String filename) {
 if (!File.Exists(filename))
	return null;
 Stream stream=new FileStream(filename,FileMode.Open);
 int datalen = (int)stream.Length;
 byte[] buffer=new byte[datalen];
 stream.Seek(0,SeekOrigin.Begin);
 stream.Read(buffer,0,datalen);
 stream.Close();
 return buffer;
 }


}