    // GenericAuthFilter.java
    // $Id: GenericAuthFilter.html,v 1.2 1999/10/27 22:10:35 ylafon Exp $
    // (c) COPYRIGHT MIT and INRIA, 1996.
    // Please first read the full copyright statement in file COPYRIGHT.html

    package org.w3c.jigsaw.auth;

    import java.io.*;
    import java.util.*;
    import java.net.*;

    import org.w3c.tools.resources.*;
    import org.w3c.jigsaw.http.*;
    import org.w3c.jigsaw.html.*;
    import org.w3c.tools.codec.* ;
    import org.w3c.www.http.*;

    import org.w3c.tools.resources.ProtocolException;

    /**
     * A generic authentication filter.
     * This filter will use both IP and basic authentication to try to authenticate
     * incomming request. It should not be use for big user's database (typically
     * the ones that have more than 1000 entries).
     */

    class BasicAuthContextException extends Exception {

        BasicAuthContextException (String msg) {
    	super (msg) ;
        }
    }

    class BasicAuthContext {
        String user     = null ;
        String password = null ;
        String cookie   = null ;

        public String toString() {
    	return user+":"+password;
        }

        BasicAuthContext (Request request)
    	throws BasicAuthContextException, ProtocolException
        {
    	HttpCredential credential = null;

    	credential = (request.isProxy()
    		      ? request.getProxyAuthorization()
    		      : request.getAuthorization());
    	if ( ! credential.getScheme().equalsIgnoreCase("Basic") ) {
    	    String msg = ("Invalid authentication scheme \""
    			  + credential.getScheme()
    			  + " expecting \"Basic\"");
    	    throw new BasicAuthContextException (msg) ;
    	}
    	// Decode the credentials:
    	String decoded = null ;
    	this.cookie    = credential.getAuthParameter("cookie");
    	try {
    	    Base64Decoder b  = new Base64Decoder (cookie) ;
    	    decoded          = b.processString() ;
    	} catch (Base64FormatException e) {
    	    String msg = "Invalid BASE64 encoding of credentials." ;
    	    throw new BasicAuthContextException (msg) ;
    	}
    	// Get user and password:
    	int icolon = decoded.indexOf (':') ;
    	if ( (icolon > 0) && (icolon+1 < decoded.length()) ) {
    	    // ok, parse was find, check user:
    	    this.user     = decoded.substring (0, icolon) ;
    	    this.password = decoded.substring (icolon+1) ;
    	} else {
    	    String msg = "Invalid credentials syntax in " + decoded ;
    	    throw new BasicAuthContextException (msg) ;
    	}
        }
    }

    /**
     * GenericAuthFilter provides for both IP and basic authentication.
     * This is really a first implementation. It looses on several points:
     * <ul>
     * <li>AuthUser instances, being a subclass of resource dump their classes
     * along with their attributes, although here we know that they will all
     * be instances of AuthUser.
     * <li>The way the ipmatcher is maintained doesn't make much sense.
     * <li>The way groups are handled is no good.
     * <li>The SimpleResourceStore is not an adequat store for the user database,
     * it should rather use the jdbmResourceStore (not written yet).
     * </ul>
     * However, this provides for the basic functionnalities.
     */

    public class GenericAuthFilter extends AuthFilter {
        /**
         * Attribute index - The list of allowed users.
         */
        protected static int ATTR_ALLOWED_USERS = -1 ;
        /**
         * Attribute index - The list of allowed groups.
         */
        protected static int ATTR_ALLOWED_GROUPS = -1 ;

        static {
    	Attribute   a = null ;
    	Class       c = null ;
    	try {
    	    c = Class.forName("org.w3c.jigsaw.auth.GenericAuthFilter");
    	} catch (Exception ex) {
    	    ex.printStackTrace() ;
    	    System.exit(1) ;
    	}
    	// The list of allowed users
    	a = new StringArrayAttribute("users"
    				     , null
    				     , Attribute.EDITABLE) ;
    	ATTR_ALLOWED_USERS = AttributeRegistry.registerAttribute(c, a) ;
    	// The list of allowed groups:
    	a = new StringArrayAttribute("groups"
    				     , null
    				     , Attribute.EDITABLE);
    	ATTR_ALLOWED_GROUPS = AttributeRegistry.registerAttribute(c, a) ;
        }

        /**
         * The IPMatcher to match IP templates to user records.
         */
        protected IPMatcher ipmatcher = null ;
        /**
         * The catalog of realms that make our scope.
         */
        protected RealmsCatalog catalog = null ;
        /**
         * Our associated realm.
         */
        protected ResourceReference rr_realm = null ;
        /**
         * The nam of the realm we cache in <code>realm</code>.
         */
        protected String loaded_realm = null ;

        /**
         * The challenge to issue to any client for Basic Authentication.
         */
        protected HttpChallenge challenge = null;

        /**
         * Get a pointer to our realm, and initialize our ipmatcher.
         */

        protected synchronized void acquireRealm() {
    	// Get our catalog:
    	if ( catalog == null ) {
    	    httpd server = (httpd)
    	      ((FramedResource) getTargetResource()).getServer() ;
    	    catalog = server.getRealmsCatalog() ;
    	}
    	// Check that our realm name is valid:
    	String name = getRealm() ;
    	if ( name == null )
    	    return ;
    	if ((rr_realm != null) && name.equals(loaded_realm))
    	    return ;
    	// Load the realm and create the ipmtacher object
    	rr_realm = catalog.loadRealm(name) ;
    	if (rr_realm != null) {
    	  try {
    	    AuthRealm realm = (AuthRealm) rr_realm.lock();
    	    Enumeration enum = realm.enumerateUserNames() ;
    	    if (enum.hasMoreElements())
    	      ipmatcher       = new IPMatcher() ;
    	    while (enum.hasMoreElements()) {
    	      String   uname = (String) enum.nextElement() ;
    	      ResourceReference rr_user = realm.loadUser(uname) ;
    	      try {
    		AuthUser user  = (AuthUser) rr_user.lock();
    		short    ips[][] = user.getIPTemplates() ;
    		if ( ips != null ) {
    		  for (int i = 0 ; i < ips.length ; i++)
    		    ipmatcher.add(ips[i], rr_user) ;
    		}
    	      } catch (InvalidResourceException ex) {
    		System.out.println("Invalid user reference : "+uname);
    	      } finally {
    		rr_user.unlock();
    	      }
    	    }
    	  } catch (InvalidResourceException ex) {

    	  } finally {
    	    rr_realm.unlock();
    	  }
    	}
        }

        /**
         * Check that our realm does exist.
         * Otherwise we are probably being initialized, and we don't authenticate
         * yet.
         * @return A boolean <strong>true</strong> if realm can be initialized.
         */

        protected synchronized boolean checkRealm() {
    	acquireRealm() ;
    	return (ipmatcher != null) ;
        }

        /**
         * Get the list of allowed users.
         */

        public String[] getAllowedUsers() {
    	return (String[]) getValue(ATTR_ALLOWED_USERS, null) ;
        }

        /**
         * Get the list of allowed groups.
         */

        public String[] getAllowedGroups() {
    	return (String[]) getValue(ATTR_ALLOWED_GROUPS, null) ;
        }

        /**
         * Lookup a user by its IP address.
         * @param ipaddr The IP address to look for.
         * @return An AuthUser instance or <strong>null</strong>.
         */

        public synchronized ResourceReference lookupUser (InetAddress ipaddr) {
    	if ( ipmatcher == null )
    	    acquireRealm() ;
    	return (ResourceReference) ipmatcher.lookup(ipaddr.getAddress()) ;
        }

        /**
         * Lookup a user by its name.
         * @param name The user's name.
         * @return An AuthUser instance, or <strong>null</strong>.
         */

        public synchronized ResourceReference lookupUser (String name) {
    	if ( rr_realm == null )
    	    acquireRealm() ;
    	try {
    	  AuthRealm realm = (AuthRealm) rr_realm.lock();
    	  return realm.loadUser(name) ;
    	} catch (InvalidResourceException ex) {
    	  return null;
    	} finally {
    	  rr_realm.unlock();
    	}
        }

        /**
         * Check the given Basic context against our database.
         * @param ctxt The basic auth context to check.
         * @return A AuthUser instance if check succeeded, <strong>null</strong>
         *    otherwise.
         */

        protected ResourceReference checkBasicAuth(BasicAuthContext ctxt) {
          ResourceReference rr_user = (ResourceReference)lookupUser(ctxt.user) ;
          if (rr_user != null) {
    	try {
    	  AuthUser user = (AuthUser) rr_user.lock();
    	  // This user doesn't even exists !
    	  if ( user == null )
    	    return null ;
    	  // If it has a password check it
    	  if ( ! user.definesAttribute("password") ) {
    	    return  rr_user;
    	  } else {
    	    return user.getPassword().equals(ctxt.password) ? rr_user : null ;
    	  }
    	} catch (InvalidResourceException ex) {
    	  return null;
    	} finally {
    	  rr_user.unlock();
    	}
          }
          return null;
        }

        /**
         * Is this user allowed in the realm ?
         * First check in the list of allowed users (if any), than in the list
         * of allowed groups (if any). If no allowed users or allowed groups
         * are defined, than simply check for the existence of this user.
         * @return A boolean <strong>true</strong> if access allowed.
         */

        protected boolean checkUser(AuthUser user) {
    	String allowed_users[] = getAllowedUsers() ;
    	// Check in the list of allowed users:
    	if ( allowed_users != null ) {
    	    for (int i = 0 ; i < allowed_users.length ; i++) {
    		if (allowed_users[i].equals(user.getName()))
    		    return true ;
    	    }
    	}
    	// Check in the list of allowed groups:
    	String allowed_groups[] = getAllowedGroups() ;
    	if ( allowed_groups != null ) {
    	    String ugroups[] = user.getGroups() ;
    	    if ( ugroups != null ) {
    		for (int i = 0 ; i < ugroups.length ; i++) {
    		    for (int j = 0 ; j < allowed_groups.length ; j++) {
    			if ( allowed_groups[j].equals(ugroups[i]) )
    			    return true ;
    		    }
    		}
    	    }
    	}
    	// If no users or groups specified, return true
    	if ((allowed_users == null) && (allowed_groups == null))
    	    return true ;
    	return false ;
        }

        /**
         * Catch set value on the realm, to maintain cached values.
         */

        public void setValue(int idx, Object value) {
    	super.setValue(idx, value);
    	if ( idx == ATTR_REALM ) {
    	    // Initialize the filter challenge:
    	    challenge = HttpFactory.makeChallenge("Basic");
    	    challenge.setAuthParameter("realm", getRealm());
    	}
        }

        /**
         * Authenticate the given request.
         * We first check for valid authentication information. If no
         * authentication is provided, than we try to map the IP address to some
         * of the ones we know about. If the IP address is not found, we challenge
         * the client for a password.
         * <p>If the IP address is found, than either our user entry requires an
         * extra password step (in wich case we challenge it), or simple IP
         * based authentication is enough, so we allow the request.
         * @param request The request to be authentified.
         */

        public void authenticate (Request request)
    	throws ProtocolException
        {
    	// Are we being edited ?
    	if ( ! checkRealm() )
    	    return ;
    	// Internal requests always allowed:
    	Client client = request.getClient() ;
    	if ( client == null )
    	    return ;
    	// Check for User by IP address:
    	boolean ipchecked = false ;
    	ResourceReference rr_user = lookupUser(client.getInetAddress());
    	if (rr_user != null) {
    	  try {
    	    AuthUser user = (AuthUser) rr_user.lock();
    	    if ( user != null ) {
    	      ipchecked = true ;
                  // Good the user exists, does it need more authentication ?
    	      if ( ! user.definesAttribute("password") && checkUser(user)) {
    		request.setState(STATE_AUTHUSER, user.getName()) ;
    		request.setState(STATE_AUTHTYPE, "ip");
    		return ;
    	      }
    	    }
    	  } catch (InvalidResourceException ex) {
    	    //FIXME
    	  } finally {
    	    rr_user.unlock();
    	  }
    	}
    	// Check authentication according to auth method:
    	if ((request.hasAuthorization() && ! request.isProxy())
    	    || (request.isProxy() && request.hasProxyAuthorization())) {
    	    BasicAuthContext ctxt = null ;
    	    try {
    		ctxt = new BasicAuthContext(request);
    	    } catch (BasicAuthContextException ex) {
    		ctxt = null;
    	    }
    	    // Is that user allowed ?
    	    if ( ctxt != null ) {
    	      rr_user = checkBasicAuth(ctxt) ;
    	      if (rr_user != null) {
    		try {
    		  AuthUser user = (AuthUser) rr_user.lock();
    		  if ((user != null) && checkUser(user)) {
    		    // Check that if IP auth was required, it succeeded:
    		    boolean iprequired = user.definesAttribute("ipaddress") ;
    		    if ( ( ! iprequired) || ipchecked ) {
    		      // Set the request fields, and continue:
    		      request.setState(STATE_AUTHUSER, ctxt.user);
    		      request.setState(STATE_AUTHTYPE, "Basic") ;
    		      return ;
    		    }
    		  }
    		} catch (InvalidResourceException ex) {
    		  //FIXME
    		} finally {
    		  rr_user.unlock();
    		}
    	      }
    	    }
    	}

    	// Every possible scheme has failed for this request, emit an error
    	Reply e = null;
    	if ( request.isProxy() ) {
    	    e = request.makeReply(HTTP.PROXY_AUTH_REQUIRED);
    	    e.setProxyAuthenticate(challenge);
    	} else {
    	    e = request.makeReply(HTTP.UNAUTHORIZED);
    	    e.setWWWAuthenticate (challenge);
    	}
    	HtmlGenerator g = new HtmlGenerator("Unauthorised");
    	g.append ("<h1>Unauthorised access</h1>"
    		  + "<p>You are denied access to this resource.");
    	e.setStream(g);
    	throw new HTTPException (e);
        }

        /**
         * Initialize the filter.
         */

        public void initialize(Object values[]) {
    	super.initialize(values) ;
    	if ( getRealm() != null ) {
    	    // Initialize the filter challenge:
    	    challenge = HttpFactory.makeChallenge("Basic");
    	    challenge.setAuthParameter("realm", getRealm());
    	}
        }

    }