package org.openslx.imagemaster.util;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;
import java.security.spec.X509EncodedKeySpec;

import org.openslx.imagemaster.db.DbSatellite;

public class AsymMessageVerifier
{
	
	private PublicKey key;
	
	/**
	 * Load the key
	 * @param organization the organization to verify
	 * @throws Exception 
	 * @throws NoSuchAlgorithmException
	 * @throws CertificateException
	 * @throws FileNotFoundException
	 * @throws IOException
	 * @throws KeyStoreException
	 * @throws UnrecoverableKeyException
	 */
	public AsymMessageVerifier(String organization) throws Exception
	{
		byte[] b = DbSatellite.getKeyfromOrganization( organization );
		
		if (b == null) throw new Exception("Organization not found.");
		
		KeyFactory kf = KeyFactory.getInstance( "RSA" );
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(b);
		key = kf.generatePublic(keySpec);
	}

	/**
	 * Verify an encrypted message.
	 *
	 * @param messageDigest The signed message from hs/uni server
	 * @param expectedCleartext The message that was sent before
	 * @return Whether the message could be verfied or not
	 * @throws NoSuchAlgorithmException
	 * @throws InvalidKeyException
	 * @throws SignatureException
	 * @throws UnrecoverableKeyException
	 * @throws KeyStoreException
	 */
	public boolean verifyMessage( byte[] messageDigest, byte[] expectedCleartext ) throws NoSuchAlgorithmException, InvalidKeyException, SignatureException, UnrecoverableKeyException, KeyStoreException
	{
		// verify message
		Signature signature = Signature.getInstance( "SHA256WITHRSA" );
		signature.initVerify( key );
		signature.update( expectedCleartext );
		return signature.verify( messageDigest );
	}

}