/**

  * Copyright 2005-2011 The Kuali Foundation

  *

  * Licensed under the Educational Community License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  * http://www.opensource.org/licenses/ecl2.php

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.kuali.rice.ksb.security;

 import java.io.IOException;

 import java.io.InputStream;

 import java.security.GeneralSecurityException;

 import java.security.Signature;

 import javax.servlet.ServletInputStream;

 /**

  * An InputStream which decorates another InputStream with a wrapper that verifies the digital signature

  * of the data after the last piece of data is read.  The digital signature to verify against is

  * passed into the constructor of this stream.

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class SignatureVerifyingInputStream extends ServletInputStream {

         private byte[] digitalSignature;

         private Signature signature;

         private InputStream wrappedInputStream;

         public SignatureVerifyingInputStream(byte[] digitalSignature, Signature signature, InputStream wrappedInputStream) {

                 this.digitalSignature = digitalSignature;

                 this.signature = signature;

                 this.wrappedInputStream = wrappedInputStream;

         }

         @Override

         public synchronized int read() throws IOException {

                 int data = this.wrappedInputStream.read();

                 try {

                         if (data == -1) {

                                 verifySignature();

                         } else {

                             this.signature.update((byte)data);

                         }

                 } catch (GeneralSecurityException e) {

                         IOException exception = new IOException("Error processing digital signature.");

                         exception.initCause(e);

                         throw exception;

                 }

                 return data;

         }

         protected void verifySignature() throws IOException, GeneralSecurityException {

                 boolean verifies = this.signature.verify(this.digitalSignature);

                 if (!verifies) {

                         throw new IOException("The digital signature could not be successfully verified!");

                 }

         }

 }