/*
    * #%L
    * Bitrepository Protocol
    * %%
    * Copyright (C) 2010 - 2012 The State and University Library, The Royal Library and The State Archives, Denmark
    * %%
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as 
    * published by the Free Software Foundation, either version 2.1 of the 
   * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   * 
   * You should have received a copy of the GNU General Lesser Public 
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-2.1.html>.
   * #L%
   */
  package org.bitrepository.protocol.security;
  
  import java.security.cert.X509Certificate;
  
  import org.bitrepository.protocol.security.exception.MessageAuthenticationException;
  import org.bitrepository.protocol.security.exception.PermissionStoreException;
  import org.bitrepository.protocol.security.exception.SecurityException;
  import org.bouncycastle.cms.CMSException;
  import org.bouncycastle.cms.CMSProcessableByteArray;
  import org.bouncycastle.cms.CMSSignedData;
  import org.bouncycastle.cms.SignerInformation;
  import org.bouncycastle.cms.SignerInformationVerifier;
  import org.bouncycastle.cms.jcajce.JcaSimpleSignerInfoVerifierBuilder;
  import org.bouncycastle.operator.OperatorCreationException;
  
  /**
   * Class to handle authentication of messages.  
   */
  public class BasicMessageAuthenticator implements MessageAuthenticator {
  
      /**
       * Non-infrastructure certificates and permission store  
       */
      private final PermissionStore permissionStore;
      
      /**
       * @param permissionStore the permissionStore holding the known certificates
       */
      public BasicMessageAuthenticator(PermissionStore permissionStore) {
          this.permissionStore = permissionStore;
      }
      
      /**
       * Attempts to authenticate the message based on a signature. 
       * @param messageData the data that is to be authenticated
       * @param signatureData the signature that of the data to be authenticated.
       * @throws MessageAuthenticationException in case authentication fails.  
       */
      @Override
      public void authenticateMessage(byte[] messageData, byte[] signatureData) throws MessageAuthenticationException {
          try {
              CMSSignedData s = new CMSSignedData(new CMSProcessableByteArray(messageData), signatureData);
              SignerInformation signer = (SignerInformation) s.getSignerInfos().getSigners().iterator().next();
              X509Certificate signingCert = permissionStore.getCertificate(signer.getSID());
              SignerInformationVerifier verifier = new JcaSimpleSignerInfoVerifierBuilder().setProvider(
                      SecurityModuleConstants.BC).build(signingCert);
              
              if(!signer.verify(verifier)) {
                  throw new MessageAuthenticationException("Signature does not match the message. Indicated " +
                      "certificate did not sign message. Certificate issuer: " 
                          + signingCert.getIssuerX500Principal().getName() + ", serial: " 
                      + signingCert.getSerialNumber());  
              }
          } catch (PermissionStoreException e) {
              throw new MessageAuthenticationException(e.getMessage(), e);
          } catch (CMSException e) {
              throw new SecurityException(e.getMessage(), e);
          } catch (OperatorCreationException e) {
              throw new SecurityException(e.getMessage(), e);
          }
      }
  }