MemberObfuscator


1   /*
2    * ProGuard -- shrinking, optimization, obfuscation, and preverification
3    *             of Java bytecode.
4    *
5    * Copyright (c) 2002-2007 Eric Lafortune (eric@graphics.cornell.edu)
6    *
7    * This program is free software; you can redistribute it and/or modify it
8    * under the terms of the GNU General Public License as published by the Free
9    * Software Foundation; either version 2 of the License, or (at your option)
10   * any later version.
11   *
12   * This program is distributed in the hope that it will be useful, but WITHOUT
13   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14   * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15   * more details.
16   *
17   * You should have received a copy of the GNU General Public License along
18   * with this program; if not, write to the Free Software Foundation, Inc.,
19   * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20   */
21  package proguard.obfuscate;
22  
23  import proguard.classfile.*;
24  import proguard.classfile.util.*;
25  import proguard.classfile.visitor.MemberVisitor;
26  
27  import java.util.*;
28  
29  /**
30   * This MemberVisitor obfuscates all class members that it visits.
31   * It uses names from the given name factory. At the same time, it avoids names
32   * from the given descriptor map.
33   * <p>
34   * The class members must have been linked before applying this visitor.
35   *
36   * @see MethodLinker
37   *
38   * @author Eric Lafortune
39   */
40  public class MemberObfuscator
41  extends      SimplifiedVisitor
42  implements   MemberVisitor
43  {
44      private boolean        allowAggressiveOverloading;
45      private NameFactory    nameFactory;
46      private Map            descriptorMap;
47  
48  
49      /**
50       * Creates a new MemberObfuscator.
51       * @param allowAggressiveOverloading a flag that specifies whether class
52       *                                   members can be overloaded aggressively.
53       * @param nameFactory                the factory that can produce
54       *                                   obfuscated member names.
55       * @param descriptorMap              the map of descriptors to
56       *                                   [new name - old name] maps.
57       */
58      public MemberObfuscator(boolean        allowAggressiveOverloading,
59                              NameFactory    nameFactory,
60                              Map            descriptorMap)
61      {
62          this.allowAggressiveOverloading = allowAggressiveOverloading;
63          this.nameFactory                = nameFactory;
64          this.descriptorMap              = descriptorMap;
65      }
66  
67  
68      // Implementations for MemberVisitor.
69  
70      public void visitAnyMember(Clazz clazz, Member member)
71      {
72          // Special cases: <clinit> and <init> are always kept unchanged.
73          // We can ignore them here.
74          String   name = member.getName(clazz);
75          if (name.equals(ClassConstants.INTERNAL_METHOD_NAME_CLINIT) ||
76              name.equals(ClassConstants.INTERNAL_METHOD_NAME_INIT))
77          {
78              return;
79          }
80  
81          // Get the member's descriptor.
82          String   descriptor = member.getDescriptor(clazz);
83  
84          // Check whether we're allowed to do aggressive overloading
85          if (!allowAggressiveOverloading)
86          {
87              // Trim the return argument from the descriptor if not.
88              // Works for fields and methods alike.
89              descriptor = descriptor.substring(0, descriptor.indexOf(')')+1);
90          }
91  
92          // Get the name map, creating a new one if necessary.
93          Map nameMap = retrieveNameMap(descriptorMap, descriptor);
94  
95          // Get the member's new name.
96          String   newName = newMemberName(member);
97  
98          // Assign a new one, if necessary.
99          if (newName == null)
100         {
101             // Find an acceptable new name.
102             nameFactory.reset();
103 
104             do
105             {
106                 newName = nameFactory.nextName();
107             }
108             while (nameMap.containsKey(newName));
109 
110             // Remember not to use the new name again in this name space.
111             nameMap.put(newName, name);
112 
113             // Assign the new name.
114             setNewMemberName(member, newName);
115         }
116     }
117 
118 
119     // Small utility methods.
120 
121     /**
122      * Gets the name map, based on the given map and a given descriptor.
123      * A new empty map is created if necessary.
124      * @param descriptorMap the map of descriptors to [new name - old name] maps.
125      * @param descriptor    the class member descriptor.
126      * @return the corresponding name map.
127      */
128     static Map retrieveNameMap(Map descriptorMap, String   descriptor)
129     {
130         // See if we can find the nested map with this descriptor key.
131         Map nameMap = (Map)descriptorMap.get(descriptor);
132 
133         // Create a new one if not.
134         if (nameMap == null)
135         {
136             nameMap = new HashMap();
137             descriptorMap.put(descriptor, nameMap);
138         }
139 
140         return nameMap;
141     }
142 
143 
144     /**
145      * Assigns a fixed new name to the given class member.
146      * @param member the class member.
147      * @param name   the new name.
148      */
149     static void setFixedNewMemberName(Member member, String   name)
150     {
151         VisitorAccepter lastVisitorAccepter = MethodLinker.lastVisitorAccepter(member);
152 
153         if (!(lastVisitorAccepter instanceof LibraryMember) &&
154             !(lastVisitorAccepter instanceof MyFixedName))
155         {
156             lastVisitorAccepter.setVisitorInfo(new MyFixedName(name));
157         }
158         else
159         {
160             lastVisitorAccepter.setVisitorInfo(name);
161         }
162     }
163 
164 
165     /**
166      * Assigns a new name to the given class member.
167      * @param member the class member.
168      * @param name   the new name.
169      */
170     static void setNewMemberName(Member member, String   name)
171     {
172         MethodLinker.lastVisitorAccepter(member).setVisitorInfo(name);
173     }
174 
175 
176     /**
177      * Returns whether the new name of the given class member is fixed.
178      * @param member the class member.
179      * @return whether its new name is fixed.
180      */
181     static boolean hasFixedNewMemberName(Member member)
182     {
183         VisitorAccepter lastVisitorAccepter = MethodLinker.lastVisitorAccepter(member);
184 
185         return lastVisitorAccepter instanceof LibraryMember ||
186                lastVisitorAccepter instanceof MyFixedName;
187     }
188 
189 
190     /**
191      * Retrieves the new name of the given class member.
192      * @param member the class member.
193      * @return the class member's new name, or <code>null</code> if it doesn't
194      *         have one yet.
195      */
196     static String   newMemberName(Member member)
197     {
198         return (String  )MethodLinker.lastVisitorAccepter(member).getVisitorInfo();
199     }
200 
201 
202     /**
203      * This VisitorAccepter can be used to wrap a name string, to indicate that
204      * the name is fixed.
205      */
206     private static class MyFixedName implements VisitorAccepter
207     {
208         private String   newName;
209 
210 
211         public MyFixedName(String   newName)
212         {
213             this.newName = newName;
214         }
215 
216 
217         // Implementations for VisitorAccepter.
218 
219         public Object   getVisitorInfo()
220         {
221             return newName;
222         }
223 
224 
225         public void setVisitorInfo(Object   visitorInfo)
226         {
227             newName = (String  )visitorInfo;
228         }
229     }
230 }
231
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