/*
 * @(#)URLClassLoader.java	1.68 01/11/29
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.net;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.io.File;
import java.io.FilePermission;
import java.io.InputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandlerFactory;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
import java.util.jar.Manifest;
import java.util.jar.Attributes;
import java.util.jar.Attributes.Name;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.SecureClassLoader;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import sun.misc.Resource;
import sun.misc.URLClassPath;

/**
 * This class loader is used to load classes and resources from a search
 * path of URLs referring to both JAR files and directories. Any URL that
 * ends with a '/' is assumed to refer to a directory. Otherwise, the URL
 * is assumed to refer to a JAR file which will be opened as needed.
 * <p>
 * The AccessControlContext of the thread that created the instance of
 * URLClassLoader will be used when subsequently loading classes and
 * resources.
 * <p>
 * The classes that are loaded are by default granted permission only to
 * access the URLs specified when the URLClassLoader was created.
 *
 * @author  David Connelly
 * @version 1.68, 11/29/01
 * @since   JDK1.2
 */
public class URLClassLoader extends SecureClassLoader {
    /* The search path for classes and resources */
    private URLClassPath ucp;

    /* The context to be used when loading classes and resources */
    private AccessControlContext acc;

    /**
     * Constructs a new URLClassLoader for the given URLs. The URLs will be
     * searched in the order specified for classes and resources after first
     * searching in the specified parent class loader. Any URL that ends with
     * a '/' is assumed to refer to a directory. Otherwise, the URL is assumed
     * to refer to a JAR file which will be downloaded and opened as needed.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     * 
     * @param urls the URLs from which to load classes and resources
     * @param parent the parent class loader for delegation
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls, ClassLoader parent) {
	super(parent);
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls);
	acc = AccessController.getContext();
    }

    /**
     * Constructs a new URLClassLoader for the specified URLs using the
     * default delegation parent <code>ClassLoader</code>. The URLs will
     * be searched in the order specified for classes and resources after
     * first searching in the parent class loader. Any URL that ends with
     * a '/' is assumed to refer to a directory. Otherwise, the URL is
     * assumed to refer to a JAR file which will be downloaded and opened
     * as needed.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     * 
     * @param urls the URLs from which to load classes and resources
     *
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls) {
	super();
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls);
	acc = AccessController.getContext();
    }

    /**
     * Constructs a new URLClassLoader for the specified URLs, parent
     * class loader, and URLStreamHandlerFactory. The parent argument
     * will be used as the parent class loader for delegation. The
     * factory argument will be used as the stream handler factory to
     * obtain protocol handlers when creating new URLs.
     *
     * <p>If there is a security manager, this method first
     * calls the security manager's <code>checkCreateClassLoader</code> method
     * to ensure creation of a class loader is allowed.
     *
     * @param urls the URLs from which to load classes and resources
     * @param parent the parent class loader for delegation
     * @param factory the URLStreamHandlerFactory to use when creating URLs
     *
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkCreateClassLoader</code> method doesn't allow 
     *             creation of a class loader.
     * @see SecurityManager#checkCreateClassLoader
     */
    public URLClassLoader(URL[] urls, ClassLoader parent,
			  URLStreamHandlerFactory factory) {
	super(parent);
	// this is to make the stack depth consistent with 1.1
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	ucp = new URLClassPath(urls, factory);
	acc = AccessController.getContext();
    }

    /**
     * Appends the specified URL to the list of URLs to search for
     * classes and resources.
     *
     * @param url the URL to be added to the search path of URLs
     */
    protected void addURL(URL url) {
	ucp.addURL(url);
    }

    /**
     * Returns the search path of URLs for loading classes and resources.
     * This includes the original list of URLs specified to the constructor,
     * along with any URLs subsequently appended by the addURL() method.
     */
    public URL[] getURLs() {
	return ucp.getURLs();
    }

    /**
     * Finds and loads the class with the specified name from the URL search
     * path. Any URLs referring to JAR files are loaded and opened as needed
     * until the class is found.
     *
     * @param name the name of the class
     * @return the resulting class
     * @exception ClassNotFoundException if the class could not be found
     */
    protected Class findClass(final String name)
	 throws ClassNotFoundException
    {
	try {
	    return (Class)
		AccessController.doPrivileged(new PrivilegedExceptionAction() {
		    public Object run() throws ClassNotFoundException {
			String path = name.replace('.', '/').concat(".class");
			Resource res = ucp.getResource(path, false);
			if (res != null) {
			    try {
				return defineClass(name, res);
			    } catch (IOException e) {
				throw new ClassNotFoundException(name, e);
			    }
			} else {
			    throw new ClassNotFoundException(name);
			}
		    }
		}, acc);
	} catch (java.security.PrivilegedActionException pae) {
	    throw (ClassNotFoundException) pae.getException();
	}
    }

    /*
     * Defines a Class using the class bytes obtained from the specified
     * Resource. The resulting Class must be resolved before it can be
     * used.
     */
    private Class defineClass(String name, Resource res) throws IOException {
	int i = name.lastIndexOf('.');
	URL url = res.getCodeSourceURL();
	if (i != -1) {
	    String pkgname = name.substring(0, i);
	    // Check if package already loaded.
	    Package pkg = getPackage(pkgname);
	    Manifest man = res.getManifest();
	    if (pkg != null) {
		// Package found, so check package sealing.
		boolean ok;
		if (pkg.isSealed()) {
		    // Verify that code source URL is the same.
		    ok = pkg.isSealed(url);
		} else {
		    // Make sure we are not attempting to seal the package
		    // at this code source URL.
		    ok = (man == null) || !isSealed(pkgname, man);
		}
		if (!ok) {
		    throw new SecurityException("sealing violation");
		}
	    } else {
		if (man != null) {
		    definePackage(pkgname, man, url);
		}
	    }
	}
	// Now read the class bytes and define the class
	byte[] b = res.getBytes();
	java.security.cert.Certificate[] certs = res.getCertificates();
	CodeSource cs = new CodeSource(url, certs);
	return defineClass(name, b, 0, b.length, cs);
    }

    /**
     * Defines a new package by name in this ClassLoader. The attributes
     * contained in the specified Manifest will be used to obtain package
     * version and sealing information. For sealed packages, the additional
     * URL specifies the code source URL from which the package was loaded.
     *
     * @param name  the package name
     * @param man   the Manifest containing package version and sealing
     *              information
     * @param url   the code source url for the package, or null if none
     * @exception   IllegalArgumentException if the package name duplicates
     *              an existing package either in this class loader or one
     *              of its ancestors
     */
    protected Package definePackage(String name, Manifest man, URL url)
	throws IllegalArgumentException
    {
	String path = name.replace('.', '/').concat("/");
	String specTitle = null, specVersion = null, specVendor = null;
	String implTitle = null, implVersion = null, implVendor = null;
	String sealed = null;
	URL sealBase = null;

	Attributes attr = man.getAttributes(path);
	if (attr != null) {
	    specTitle   = attr.getValue(Name.SPECIFICATION_TITLE);
	    specVersion = attr.getValue(Name.SPECIFICATION_VERSION);
	    specVendor  = attr.getValue(Name.SPECIFICATION_VENDOR);
	    implTitle   = attr.getValue(Name.IMPLEMENTATION_TITLE);
	    implVersion = attr.getValue(Name.IMPLEMENTATION_VERSION);
	    implVendor  = attr.getValue(Name.IMPLEMENTATION_VENDOR);
	    sealed      = attr.getValue(Name.SEALED);
	}
	attr = man.getMainAttributes();
	if (attr != null) {
	    if (specTitle == null) {
		specTitle = attr.getValue(Name.SPECIFICATION_TITLE);
	    }
	    if (specVersion == null) {
		specVersion = attr.getValue(Name.SPECIFICATION_VERSION);
	    }
	    if (specVendor == null) {
		specVendor = attr.getValue(Name.SPECIFICATION_VENDOR);
	    }
	    if (implTitle == null) {
		implTitle = attr.getValue(Name.IMPLEMENTATION_TITLE);
	    }
	    if (implVersion == null) {
		implVersion = attr.getValue(Name.IMPLEMENTATION_VERSION);
	    }
	    if (implVendor == null) {
		implVendor = attr.getValue(Name.IMPLEMENTATION_VENDOR);
	    }
	    if (sealed == null) {
		sealed = attr.getValue(Name.SEALED);
	    }
	}
	if ("true".equalsIgnoreCase(sealed)) {
	    sealBase = url;
	}
	return definePackage(name, specTitle, specVersion, specVendor,
			     implTitle, implVersion, implVendor, sealBase);
    }

    /*
     * Returns true if the specified package name is sealed according to the
     * given manifest.
     */
    private boolean isSealed(String name, Manifest man) {
	String path = name.replace('.', '/').concat("/");
	Attributes attr = man.getAttributes(path);
	String sealed = null;
	if (attr != null) {
	    sealed = attr.getValue(Name.SEALED);
	}
	if (sealed == null) {
	    if ((attr = man.getMainAttributes()) != null) {
		sealed = attr.getValue(Name.SEALED);
	    }
	}
	return "true".equalsIgnoreCase(sealed);
    }

    /**
     * Finds the resource with the specified name on the URL search path.
     * Returns a URL for the resource, or null if the resource could not
     * be found.
     *
     * @param name the name of the resource
     */
    public URL findResource(final String name) {
	/*
	 * The same restriction to finding classes applies to resources
	 */
	Resource res =
	    (Resource) AccessController.doPrivileged(new PrivilegedAction() {
		    public Object run() {
			return ucp.getResource(name, true);
		    }
		}, acc);
	
        return res != null ? ucp.checkURL(res.getURL()) : null;
    }

    /**
     * Returns an Enumeration of URLs representing all of the resources
     * on the URL search path having the specified name.
     *
     * @param name the resource name
     * @exception if an I/O exception occurs
     * @return an <code>Enumeration</code> of <code>URL</code>s
     */
    public Enumeration findResources(final String name) throws IOException {
        final Enumeration e = ucp.getResources(name, true);

        return new Enumeration() {
            private URL res;

            public Object nextElement() {
                if (res == null)
                    throw new NoSuchElementException();
                URL url = res;
                res = null;
                return url;
            }
  
            public boolean hasMoreElements() {
                if (res != null)
                    return true;
                do {
                    Resource r = (Resource)
                        AccessController.doPrivileged(new PrivilegedAction() {
                        public Object run() {
                            if (!e.hasMoreElements())
                                return null;
                            return e.nextElement();
                        }
                    }, acc);
                    if (r == null)
                        break;
                    res = ucp.checkURL(r.getURL());
                } while (res == null);
                return res != null;
            }
	};
    }

    /**
     * Returns the permissions for the given codesource object.
     * The implementation of this method first calls super.getPermissions,
     * to get the permissions
     * granted by the policy, and then adds additional permissions
     * based on the URL of the codesource.
     * <p>
     * If the protocol is "file"
     * and the path specifies a file, then permission to read that
     * file is granted. If protocol is "file" and the path is
     * a directory, permission is granted to read all files
     * and (recursively) all files and subdirectories contained in
     * that directory.
     * <p>
     * If the protocol is not "file", then
     * to connect to and accept connections from the URL's host is granted.
     * @param codesource the codesource
     * @return the permissions granted to the codesource
     */
    protected PermissionCollection getPermissions(CodeSource codesource)
    {
	PermissionCollection perms = super.getPermissions(codesource);

	URL url = codesource.getLocation();

	Permission p;

	try {
	    p = url.openConnection().getPermission();
	} catch (java.io.IOException ioe) {

	    p = null;
	}

	if (p instanceof FilePermission) {
	    // if the permission has a separator char on the end,
	    // it means the codebase is a directory, and we need
	    // to add an additional permission to read recursively
	    String path = p.getName();
	    if (path.endsWith(File.separator)) {
		path += "-";
		p = new FilePermission(path, "read");
	    }
	} else if ((p == null) && (url.getProtocol().equals("file"))) {
	    String path = url.getFile().replace('/', File.separatorChar);
	    if (path.endsWith(File.separator))
		path += "-";
	    p =  new FilePermission(path, "read");
	} else {
	    String host = url.getHost();
	    if (host == null)
		host = "localhost";
	    p = new SocketPermission(host,"connect, accept");
	}

	// make sure the person that created this class loader
	// would have this permission

	if (p != null) {
	    final SecurityManager sm = System.getSecurityManager();
	    if (sm != null) {
		final Permission fp = p;
		AccessController.doPrivileged(new PrivilegedAction() {
		    public Object run() throws SecurityException {
			sm.checkPermission(fp);
			return null;
		    }
		}, acc);
	    }
	    perms.add(p);
	}
	return perms;
    }

    /**
     * Creates a new instance of URLClassLoader for the specified
     * URLs and parent class loader. If a security manager is
     * installed, the <code>loadClass</code> method of the URLClassLoader
     * returned by this method will invoke the
     * <code>SecurityManager.checkPackageAccess</code> method before
     * loading the class.
     *
     * @param urls the URLs to search for classes and resources
     * @param parent the parent class loader for delegation
     * @return the resulting class loader
     */
    public static URLClassLoader newInstance(final URL[] urls,
					     final ClassLoader parent) {
	// Save the caller's context
	AccessControlContext acc = AccessController.getContext();
	// Need a privileged block to create the class loader
	URLClassLoader ucl =
	    (URLClassLoader) AccessController.doPrivileged(new PrivilegedAction() {
		public Object run() {
		    return new FactoryURLClassLoader(urls, parent);
		}
	    });
	// Now set the context on the loader using the one we saved,
	// not the one inside the privileged block...
	ucl.acc = acc;
	return ucl;
    }

    /**
     * Creates a new instance of URLClassLoader for the specified
     * URLs and default parent class loader. If a security manager is
     * installed, the <code>loadClass</code> method of the URLClassLoader
     * returned by this method will invoke the
     * <code>SecurityManager.checkPackageAccess</code> before
     * loading the class.
     *
     * @param urls the URLs to search for classes and resources
     * @return the resulting class loader
     */
    public static URLClassLoader newInstance(final URL[] urls) {
	// Save the caller's context
	AccessControlContext acc = AccessController.getContext();
	// Need a privileged block to create the class loader
	URLClassLoader ucl = (URLClassLoader)
	    AccessController.doPrivileged(new PrivilegedAction() {
		public Object run() {
		    return new FactoryURLClassLoader(urls);
		}
	    });

	// Now set the context on the loader using the one we saved,
	// not the one inside the privileged block...
	ucl.acc = acc;
	return ucl;
    }
}

final class FactoryURLClassLoader extends URLClassLoader {

    FactoryURLClassLoader(URL[] urls, ClassLoader parent) {
	super(urls, parent);
    }

    FactoryURLClassLoader(URL[] urls) {
	super(urls);
    }

    public final synchronized Class loadClass(String name, boolean resolve)
	throws ClassNotFoundException
    {
	// First check if we have permission to access the package. This
	// should go away once we've added support for exported packages.
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    int i = name.lastIndexOf('.');
	    if (i != -1) {
		sm.checkPackageAccess(name.substring(0, i));
	    }
	}
	return super.loadClass(name, resolve);
    }
}