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.invoke.MethodHandles;

    27 import java.lang.invoke.MethodHandles.Lookup;

    28 import java.lang.reflect.*;

    29 import java.util.jar.*;

    30 

    31 public class Util {

    32     /**

    33      * Define the class as stored in clsFile with the provided lookup instance,

    34      * with the following modification:

    35      * <ul>

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

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

    38      * </ul>

    39      */

    40     public static Class<?> defineModifiedClass(Lookup lookup, File clsFile, String fromString, String toString)

    41         throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,

    42                InvocationTargetException

    43     {

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

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

    46         dis.readFully(buff);

    47         replace(buff, fromString, toString);

    48 

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

    50 

    51 

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

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

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

    55         Class<?> cls = lookup.defineClass(buff);

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

    57 

    58         return cls;

    59       }

    60     }

    61 

    62     /**

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

    64      * have been replaced.

    65      */

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

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

    68             throw new RuntimeException("bad strings");

    69         }

    70         byte f[] = asciibytes(from);

    71         byte t[] = asciibytes(to);

    72         byte f0 = f[0];

    73 

    74         int numReplaced = 0;

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

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

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

    78                 i += f.length;

    79                 numReplaced ++;

    80             } else {

    81                 i++;

    82             }

    83         }

    84         return numReplaced;

    85     }

    86 

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

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

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

    90                 return false;

    91             }

    92         }

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

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

    95         }

    96         return true;

    97     }

    98 

    99     static byte[] asciibytes(String s) {

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

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

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

   103         }

   104         return b;

   105     }

   106 

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

   108         JarFile jf = new JarFile(jarFile);

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

   110 

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

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

   113             dis.readFully(buff);

   114             return buff;

   115         }

   116     }

   117 }