1 /*

     2  * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 import java.io.*;

    26 import java.lang.reflect.*;

    27 import java.util.jar.*;

    28 

    29 public class Util {

    30     /**

    31      * Invoke the loader.defineClass() class method to define the class stored in clsFile,

    32      * with the following modification:

    33      * <ul>

    34      *  <li> All ASCII strings in the class file bytes that matches fromString will be replaced with toString.

    35      *       NOTE: the two strings must be the exact same length.

    36      * </ul>

    37      */

    38     public static Class defineModifiedClass(ClassLoader loader, File clsFile, String fromString, String toString)

    39         throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,

    40                InvocationTargetException

    41     {

    42       try (DataInputStream dis = new DataInputStream(new FileInputStream(clsFile))) {

    43         byte[] buff = new byte[(int)clsFile.length()];

    44         dis.readFully(buff);

    45         replace(buff, fromString, toString);

    46 

    47         System.out.println("Loading from: " + clsFile + " (" + buff.length + " bytes)");

    48 

    49         Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass",

    50                                                                  buff.getClass(), int.class, int.class);

    51         defineClass.setAccessible(true);

    52 

    53         // We directly call into ClassLoader.defineClass() to define the "Super" class. Also,

    54         // rewrite its classfile so that it returns ___yyy___ instead of ___xxx___. Changing the

    55         // classfile will guarantee that this class will NOT be loaded from the CDS archive.

    56         Class cls = (Class)defineClass.invoke(loader, buff, new Integer(0), new Integer(buff.length));

    57         System.out.println("Loaded : " + cls);

    58 

    59         return cls;

    60       }

    61     }

    62 

    63     /**

    64      * @return the number of occurrences of the <code>from</code> string that

    65      * have been replaced.

    66      */

    67     public static int replace(byte buff[], String from, String to) {

    68         if (to.length() != from.length()) {

    69             throw new RuntimeException("bad strings");

    70         }

    71         byte f[] = asciibytes(from);

    72         byte t[] = asciibytes(to);

    73         byte f0 = f[0];

    74 

    75         int numReplaced = 0;

    76         int max = buff.length - f.length;

    77         for (int i=0; i<max; ) {

    78             if (buff[i] == f0 && replace(buff, f, t, i)) {

    79                 i += f.length;

    80                 numReplaced ++;

    81             } else {

    82                 i++;

    83             }

    84         }

    85         return numReplaced;

    86     }

    87 

    88     public static boolean replace(byte buff[], byte f[], byte t[], int i) {

    89         for (int x=0; x<f.length; x++) {

    90             if (buff[x+i] != f[x]) {

    91                 return false;

    92             }

    93         }

    94         for (int x=0; x<f.length; x++) {

    95             buff[x+i] = t[x];

    96         }

    97         return true;

    98     }

    99 

   100     static byte[] asciibytes(String s) {

   101         byte b[] = new byte[s.length()];

   102         for (int i=0; i<b.length; i++) {

   103             b[i] = (byte)s.charAt(i);

   104         }

   105         return b;

   106     }

   107 

   108     public static Class defineClassFromJAR(ClassLoader loader, File jarFile, String className)

   109         throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,

   110                InvocationTargetException {

   111         return defineClassFromJAR(loader, jarFile, className, null, null);

   112     }

   113 

   114     /**

   115      * Invoke the loader.defineClass() class method to define the named class stored in a JAR file.

   116      *

   117      * If a class exists both in the classpath, as well as in the list of URLs of a URLClassLoader,

   118      * by default, the URLClassLoader will not define the class, and instead will delegate to the

   119      * app loader. This method is an easy way to force the class to be defined by the URLClassLoader.

   120      *

   121      * Optionally, you can modify the contents of the classfile buffer. See comments in

   122      * defineModifiedClass.

   123      */

   124     public static Class defineClassFromJAR(ClassLoader loader, File jarFile, String className,

   125                                            String fromString, String toString)

   126         throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,

   127                InvocationTargetException

   128     {

   129         byte[] buff = getClassFileFromJar(jarFile, className);

   130 

   131         if (fromString != null) {

   132             replace(buff, fromString, toString);

   133         }

   134 

   135         //System.out.println("Loading from: " + ent + " (" + buff.length + " bytes)");

   136 

   137         Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass",

   138                                                                  buff.getClass(), int.class, int.class);

   139         defineClass.setAccessible(true);

   140         Class cls = (Class)defineClass.invoke(loader, buff, new Integer(0), new Integer(buff.length));

   141 

   142         //System.out.println("Loaded : " + cls);

   143         return cls;

   144     }

   145 

   146     public static byte[] getClassFileFromJar(File jarFile, String className) throws FileNotFoundException, IOException {

   147         JarFile jf = new JarFile(jarFile);

   148         JarEntry ent = jf.getJarEntry(className.replace('.', '/') + ".class");

   149 

   150         try (DataInputStream dis = new DataInputStream(jf.getInputStream(ent))) {

   151             byte[] buff = new byte[(int)ent.getSize()];

   152             dis.readFully(buff);

   153             return buff;

   154         }

   155     }

   156 }