SandboxClassLoader.java

/*
 * Copyright 2007 Xu, Chuan <xuchuan@gmail.com>
 *
 * This file is part of ZOJ.
 *
 * ZOJ is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * ZOJ 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 Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ZOJ. if not, see <http://www.gnu.org/licenses/>.
 */

import java.io.File;
import java.io.FileInputStream;

class SandboxClassLoader extends ClassLoader {
    
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        if (!isAllowedClassName(name)) {
            throw new ClassNotFoundException(name);
        }
        Class<?> ret = super.loadClass(name);
        if (Error.class.isAssignableFrom(ret)) {
            throw new ClassNotFoundException(name);
        }
        return ret;
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        if (name.indexOf('.') >= 0) {
            throw new ClassNotFoundException(name);
        }
        File classFile = new File(name + ".class");
        byte[] classContent = new byte[(int) classFile.length()];
        try {
            FileInputStream in = new FileInputStream(classFile);
            in.read(classContent);
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
            throw new ClassNotFoundException(name);
        }
        return defineClass(name, classContent);
    }

    private boolean isAllowedClassName(String name) {
        if (name.startsWith("java.lang.")) {
            // disable loading the thread class
            // - Mike
            if(name.equals("java.lang.Thread"))
               return false;
            if (name.indexOf('.', 10) >= 0 || name.endsWith(".ClassNotFoundException")) {
                return false;
            }
        } else if (!name.startsWith("java.util.") && !name.startsWith("java.io.") &&
            !name.startsWith("java.nio.") && !name.startsWith("java.net.") && !name.startsWith("java.math.") &&
            !name.startsWith("java.text.") && name.indexOf('.') >= 0) {
            return false;
        }
        return true;
    }

    private Class<?> defineClass(String name, byte[] b) {
        return this.defineClass(name, b, 0, b.length);
    }
}