/*
 * VerifyHandler.java (för 10.2)
 * Karl-Adam Karlsson
 * 06-10-11
 *
 * java VerifyHandler <data> <certificate> <signature> som kontrollerar om certifikatet (med den publika nyckeln)
 * i filen <certificate> och signaturen i filen <signature> verifierar filen <data> 
 *
 */

import java.security.*;
import java.io.*;

public class VerifyHandler{


	VerifyHandler(String dataPath, String certPath, String sigPath){
		verifyData((java.security.cert.Certificate)loadObj(certPath),getInS(dataPath), loadSignature(sigPath));
	}


	/*
	 * Kollar om certifikatet cert och signaturen asig
	 * verifierar datat i ins.
	 * Resultatet av verifieringen skrivs ut i konsolfönstret.
	 *
	 * @param Certificate aCert The certificate to use during verification
	 * @param FileInputStream ins A stream connected to the data to verify
	 * @param Signature aSig A signature to use during verification
	 *
	 */
	private void verifyData(java.security.cert.Certificate aCert, FileInputStream ins, byte[] aSig){
		Signature anotherSig=null;
		
		
		
		try{
			anotherSig = Signature.getInstance( "SHA1withDSA" );
			anotherSig.initVerify(aCert);
		}catch(InvalidKeyException ink){
			ink.printStackTrace();
			System.exit(1);	
		}catch(NoSuchAlgorithmException noAl){
			noAl.printStackTrace();
			System.exit(1);	
		}
		
		
		//update signature fopr verification
		int aLen;
		byte[] buffLn = new byte[1024];
		
		try{
	        	while ((aLen = ins.read(buffLn)) != -1) {
    	    	             anotherSig.update( buffLn );
        		}
        		
        	boolean verification = anotherSig.verify( aSig );
			System.out.println("signature verifies: " + verification);
        		
				
        }catch(IOException ioe){
        	ioe.printStackTrace();
			System.exit(1);	
        }catch(SignatureException sigEx){
        	sigEx.printStackTrace();
			System.exit(1);	
        }
        //
		
	}


	/*
	* loadObj loads and returns a Object from a file named path.
	* @param path the path to the file to load the Object from
	* @return Object The loaded Object.
	*/
	private  Object loadObj(String path){
		Object aObj = null;
		FileInputStream fIn = null;
		ObjectInputStream obIn = null;
		
		try{
			fIn = getInS(path);
			obIn = new ObjectInputStream(fIn);
			aObj = (Object)obIn.readObject();		
		}catch(IOException ioe){
			ioe.printStackTrace();
			System.exit(1);
		}catch(ClassNotFoundException cNof){
			cNof.printStackTrace();
			System.exit(1);
		}

	return aObj;
	}//end of loadObj



	/*
	* getInS
	* Returns a FileInputStream connected to a file
	* @param String fimeName The name of the file to connect the stream to.
	* @return FileInputStream A stream connected to the file.
	*/
	private FileInputStream getInS(String fileName){
		FileInputStream inFstream = null;
		
		try{
			inFstream = new FileInputStream(fileName);
		}catch(FileNotFoundException fEx){
			fEx.printStackTrace();;
			System.exit(1);
		}
	return inFstream;	
	}//end of getInS
	
	
		/*
	 * Loads a signature as byte[] form from the file
	 * signame and returns the byte[] representation.
	 *
	 * @param String sigName The name of the file to load the signature from
	 * @return byte[] A bytearray representation of the signature.
	 */
	private byte[] loadSignature(String sigName){
		byte[] byteArr = null;
		
		try{
			FileInputStream sIn = new FileInputStream (sigName);
    		byteArr = new byte[sIn.available ()];
     		sIn.read (byteArr);
     		sIn.close ();
     	}catch(FileNotFoundException fNf){
			System.err.print(fNf);
			System.exit(1);
		}catch(IOException iOE){
			System.err.print(iOE);
			System.exit(1);
		}
		
     return byteArr;
	}//End of loadsignature

	/*
	* main
	* 
	*/
	public static void main (String[] args) {
		
		if(args==null || args.length < 3 ||args.length>3){
			System.out.println("Usage: VerifyHandler <data> <certificate> <signature>");
			System.out.println("Where <data> is to verify.");
			System.out.println("Where <certificate> is the name of certificatefile to use for verification.");
			System.out.println("Where <signature> is the signature to use for verification.");
		}
		else if(args.length==3&&args[0]!=null&&args[1]!=null&&args[2]!=null){
			new VerifyHandler(args[0],args[1],args[2]);
		}
		else if(args[0]==null||args[1]==null||args[2]==null){
			System.out.println("Usage: VerifyHandler <data> <certificate> <signature>");
			System.out.println("Where <data> is to verify.");
			System.out.println("Where <certificate> is the name of certificatefile to use for verification.");
			System.out.println("Where <signature> is the signature to use for verification.");
		}
  		
  	}//end of main
}//End of Class