Android odex文件反编译

左手的ㄟ右手 2022-08-02 04:50 280阅读 0赞

**odex** 是经过优化的dex文件，且独立存在于apk文件。odex 多用于系统预制应用或服务。通过将apk中的dex文件进行 odex，可以加载 apk 的启动速度，同时减小空间的占用。请参考[ODEX][]关于 odex 的说明。

在反编译 odex 文件的过程中，我们需要使用到以下工具

*  [smali/baksmali][smali_baksmali]
 *  [dex2jar][]
 *  [JD Compiler, jar反编译工具][JD Compiler_ jar]

**smali/baksmali**是odex与dex文件格式互相转换的两个工具，**dex2jar**则是将dex文件转为java的jar文件，**JD Compiler**用于反编译jar文件。也就是说，经过以上一系列的操作，我们最终可以从一个odex文件得到一个可读的java文件。（事实上，也不是完全可读，与源码上还是有差别，有时候部分代码还无法反编译过来，只能以jdk虚拟机指令的方式存在了）。

首先，一个 odex 文件的生成过程是：java -> class -> dex -> odex，那么反编译的就是上面过程的逆操作了：odex -> dex -> class -> java。

我的测试环境：

*  Android 4.1.2
 *  Samsung Galaxy II

以Android系统中的 uiautomator.odex 文件为例，目标是反编译其源码（其实它的源码[grepcode][]).

## 工具准备 ##

创建一个临时目录test，将 smali/baksmali 相关的工具都放入其中。

## 反编译 (odex -> dex) ##

首先，将目标 odex 文件拿出来。

在合成 odex 文件过程中，还需要用到很多依赖文件，它们同样也是 odex 格式的。因此在合成时，我们需要根据情况反复从手机中抽取相关的依赖包。

关于命令的使用，直接执行 `java -jar baksmali-2.0.2.jar` 可以得到相关的使用说明。这里要用到的参数主要是:

*  `[-a | --api-level]`: Android API等级，Android 4.1.2是16
 *  `[-x | --deodex]`: 操作，反编译
 *  `[-d|--bootclasspath-dir]`: 依赖包的目录，我们用当前目录.

开始反编译，执行以下命令：

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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">&gt;java -jar baksmali-2.0.2.jar -a 16 -x uiautomator.odex -d .</code> 
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       &nbsp; 
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     </div> 
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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">.odex</code> 
     </div> 
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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">at org.jf.dexlib2.analysis.ClassPath.loadClassPathEntry(ClassPath.java:217)</code> 
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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">at org.jf.dexlib2.analysis.ClassPath.fromClassPath(ClassPath.java:161)</code> 
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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">at org.jf.baksmali.baksmali.disassembleDexFile(baksmali.java:59)</code> 
     </div> 
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      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:inherit!important; background:none!important">at org.jf.baksmali.main.main(main.java:274)</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

以上的异常表明，反编译的过程缺少依赖包`/system/framework/core-junit.odex`,那就从系统中提取。

反编译 uiautomator.odex 总共需要使用到以下依赖包：

baksmali 执行成功后，会产生一个 `out` 目录，里面放的是中间文件。这时，可以使用这些中间文件来生成`dex`文件：

classes-dex2jar.jar 便是我们要得到java jar包。通过JD Compiler打开这个jar可以看到反编译后的java内容。

之所以反编译 uiautomator，是因为Android SDK中给出的 uiautomator.jar 包中很多API都没有包含其中，也没有在其官方文档中给予说明。通过阅读 uiautomator 的源码，发现它有很多可以[扩展的地方][Link 1]。

[ODEX]: http://baike.baidu.com/link?url=dvNvK5sYGU9qFfccvm-ndA-8vPCvtcnMYBUUy1XLqNIP6DEsKm_vTdseNNe6zcRxmByoWZT2MXgd79SJHsHun_
[smali_baksmali]: http://code.google.com/p/smali/
[dex2jar]: http://code.google.com/p/dex2jar/downloads/list
[JD Compiler_ jar]: http://jd.benow.ca/
[grepcode]: http://grepcode.com/
[Link 1]: http://blog.codingme.com/