import java.io.*;
import java.math.BigInteger;
import java.security.*;
import java.security.interfaces.*;
import java.util.*;

//--- Generate an PKCS #1 RSA signature using keys from specified pkcs #12 store file ----

class RSASigPFX {

 static final String SIGOUT = "_rsasigpfx";

    public static void main(String[] args) {

        /* Generate a RSA signature */

        if (args.length != 2) {
            System.out.println("Usage: RSASigPFX <nameOfFileToSign>  <pkcs12 file>");
	    return;
            }

	/* Use PKCS #12 type keystore  */

	try
	{
	System.out.print("\nPassword to PFX: ");
	BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));


	char[] pswd = stdin.readLine().toCharArray() ;
	KeyStore keystore = KeyStore.getInstance("PKCS12");
	keystore.load(new FileInputStream(args[1]), pswd);

	Enumeration en = keystore.aliases();
	String ALIAS = "" ;

	Vector vectaliases = new Vector() ;
	while (en.hasMoreElements())
	{
		vectaliases.add(en.nextElement()) ;
	}


	String[] aliases = (String []) (vectaliases.toArray(new String[0])) ;

	for(int i=0; i<aliases.length; i++)
		if(keystore.isKeyEntry(aliases[i])){
			ALIAS = aliases[i];
			break;
		}


	if(ALIAS.equals("")) {
	 System.out.println("No key entries found; cannot generate RSA signature");
	 return;
 	}

	   System.out.println("Using key entry alias: " + ALIAS);
           Key priv = keystore.getKey(ALIAS, pswd);
           PublicKey pub = keystore.getCertificate(ALIAS).getPublicKey();
	  // System.out.println("Public Key Format: " + pub.getFormat()) ;
  if(false)
   {
	   if(pub instanceof RSAKey)
		System.out.println("Key Modulus: " +  ((RSAKey)pub).getModulus()) ;
	   byte [] bytesnum = ((RSAKey)pub).getModulus().toByteArray() ;
             System.out.print("Key Modulus Hex: ") ;
	   int bytecon = 0;    //to get unsigned byte representation
	  for(int i=0; i<bytesnum.length ; i++){
		bytecon = bytesnum[i] & 0xFF ;   // byte-wise AND converts signed byte to unsigned.
           if(bytecon<16)
            System.out.print("0" + Integer.toHexString(bytecon).toUpperCase());   // pad on left if single hex digit.
            else
            System.out.print(Integer.toHexString(bytecon).toUpperCase());   // pad on left if single hex digit.
	  }
   }

	  // if(pub instanceof RSAPublicKey)
	//	System.out.println("\nPublic Key Exponent: " +  ((RSAPublicKey)pub).getPublicExponent()) ;


            /* Create a Signature object and initialize it with the private key */

            Signature rsa = Signature.getInstance("SHA1withRSA"); 

            Provider prov = rsa.getProvider() ;
           // System.out.println("SHA1withRSA provider name: " + prov.getName()) ;
            prov = keystore.getProvider() ;
	    //System.out.println("Keystore provider name: " + prov.getName()) ;

            rsa.initSign((PrivateKey)priv);
           // System.out.println("Algorithm: " + rsa.getAlgorithm()) ;
            /* Update and sign the data */

            FileInputStream fis = new FileInputStream(args[0]);
            BufferedInputStream bufin = new BufferedInputStream(fis);
            byte[] buffer = new byte[1024];
            int len=0;
            while (bufin.available() != 0) {
                len = bufin.read(buffer);
                rsa.update(buffer, 0, len);
                };
	System.out.println("Successfully generated signature .. writing to file " + SIGOUT) ;
          //rsa.update((byte)0) ;  // add the null byte for compatibility with cryptoAPI
           // System.out.println("Buffer used: " + len+1) ;
            bufin.close();

            /* Now that all the data to be signed has been read in, 
                    generate a signature for it */

            byte[] realSig = rsa.sign();

        
            /* Save the signature in a file */
            FileOutputStream sigfos = new FileOutputStream(SIGOUT);
            sigfos.write(realSig);

            sigfos.close();


            /* Save the key certificate to a file */
            byte[] keycert = keystore.getCertificate(ALIAS).getEncoded() ;
            FileOutputStream certfos = new FileOutputStream("keycert.cer");
            certfos.write(keycert);
            certfos.close();


            /* Save the public key in a file */
            byte[] key = pub.getEncoded();
            FileOutputStream keyfos = new FileOutputStream("publickey");
            keyfos.write(key);
            keyfos.close();

        }
	catch (Exception e)
	{
            System.err.println("Caught exception " + e.toString());
        }

    }

}