Android DEX安全攻防战

妖狐艹你老母 2023-10-16 20:18 23阅读 0赞

来源于看雪论坛： [http://bbs.pediy.com/showthread.php?t=177114][http_bbs.pediy.com_showthread.php_t_177114]

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 本文章由Jack_Jia编写，转载请注明出处。&nbsp;&nbsp; 
 文章链接：http://blog.csdn.net/jiazhijun/article/details/9428861 
 作者：Jack_Jia&nbsp;&nbsp;&nbsp;&nbsp;邮箱：&nbsp;309zhijun@163.com 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;英文原版：http://www.strazzere.com/papers/DexEducation-PracticingSafeDex.pdf 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;该文章发表于Black&nbsp;Hat&nbsp;2012，虽然内容不够新鲜，也许好多方法目前已经失效，但是仍然会给我们反逆向方面很多的启示！ 
 
 一、DEX相关基础知识 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1、什么是DEX? 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DEX是Dalvik&nbsp;EXecutable的简称。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;打包.class文件为单一DEX文件并运行于Dalvik虚拟机。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DEX文件打包进APK文件中（本质上是jar或zip文件）。 
 
 <img src="https://img-blog.csdn.net/20130723221002593?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130723221002593?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130723221002593?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;安装时，系统提取DEX文件进行检查和验证。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;第一次运行时，系统完成DEX优化，转换成odex文件。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;odex文件存放在/data/dalvik-cache目录并在执行时加载进内存执行。 
 
 <img src="https://img-blog.csdn.net/20130723221750109?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130723221750109?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130723221750109?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2、DEX文件格式（查看更多内容请访问：http://blog.csdn.net/androidsecurity/article/details/8664778） 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130723222746531?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130723222746531?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130723222746531?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3、如何查看DEX文件 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;目前有以下工具可以完成DEX文件的反编译。 
 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130723222537734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130723222537734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130723222537734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 二、攻击者隐藏软件行为的方法 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;攻击者经常采用以下方式隐藏软件的行为： 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1、使用反射调用敏感API 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130725225910390?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725225910390?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725225910390?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;该种方式能够使攻击者“隐藏”敏感API调用。但是这种方式只需要查看是否利用JAVA反射即可很容易的被识破。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;如果配合代码混淆技术，就会增加自动化识别的难度。对付这种“隐藏”方式，动态分析会更简单一些。 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2、代码逻辑“藏匿”在资源文件中 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;可以通过修改文件后缀名隐藏代码逻辑&nbsp;，如下图： 
 
 
 <img src="https://img-blog.csdn.net/20130725235517218?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235517218?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235517218?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 
 <img src="https://img-blog.csdn.net/20130725235707921?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235707921?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235707921?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;通过文件后缀隐藏可以通过file命令查看文件类型是否与后缀匹配很容易识别。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们还可以做的更加高级一点。下图将ELF可执行二进制文件附加在有效的图片文件中，通过file指令得到正确的文件类型，且该图片可以正常显示： 
 
 
 <img src="https://img-blog.csdn.net/20130725235612750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235612750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235612750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;该种隐藏方式需要我们更加深入的查看所有的资源文件。看着是jpg图片文件，但并不一定全是（永远不要相信自己的眼睛）。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;也许还有其它更高级的隐藏恶意代码的方法。 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3、使用DexClassLoader动态加载技术 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;可以使用Android&nbsp;DexClassLoader完成DEX的动态加载，DEX文件可以附属在assert或raw目录也可以运行时从网络下载。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 三、Android反逆向分析之旅 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们可以利用逆向分析工具实现上的缺陷来触发其奔溃，从而达到反逆向分析的目的。 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Android反逆向分析的目标： 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Baksmali&nbsp;-&nbsp;使用最广泛的DEX反编译工具&nbsp;(apktool/antilvl等使用)（https://code.google.com/p/smali/） 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dex2jar&nbsp;-&nbsp;可以把DEX反编译成jar的工具，然后通过JD-GUI查看。（http://code.google.com/p/dex2jar/） 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;IDA&nbsp;Pro&nbsp;-&nbsp;（这个就不在介绍了吧！）（https://www.hex-rays.com/index.shtml） 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;androguard&nbsp;-&nbsp;也是比较流行的。（https://code.google.com/p/androguard/） 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1、构建DEX&nbsp;link&nbsp;section触发baksmali工具崩溃（DEX文件结构请查看http://blog.csdn.net/androidsecurity/article/details/8664778） 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;由于baksmali工具不支持DEX文件的link&nbsp;section，所以我们可以构建DEX&nbsp;link&nbsp;section触发baksmali工具奔溃。如下图： 
 
 
 <img src="https://img-blog.csdn.net/20130725235742796?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235742796?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235742796?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;该方式常用于开发者阻止破解者逆向分析代码逻辑。&nbsp;该方法已经被Lohan+&nbsp;(AntiLVL)&nbsp;/&nbsp;jcase&nbsp;/和其它项目中使用。但是这种方式也有明显的缺点，可以根据异常信息很容易的修复分析工具。 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2、利用已知的JAR&nbsp;hack方法 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;由于APK本质上就是zip/jar包，所以我们也可以利用已知的JAR&nbsp;hack方法。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;JAR对文件名的长度是没有现在的，但是操作系统要求文件名不能大于255；我们可以通过构建大于255字符的长类名来达到反逆向的目的。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;如何构建大于255的长类名呢？首先我们看一下DEX&nbsp;Class&nbsp;Def&nbsp;Item的格式： 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130808224444437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130808224444437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130808224444437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们可以通过以下方式构建大于255的长类名： 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1、在源代码中添加大于255的字符串A。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2、编译源代码，修改DEX文件头，修改Class&nbsp;descriptor_id为字符串A的String_idx 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;下图是修改前后比较： 
 
 
 <img src="https://img-blog.csdn.net/20130808224649343?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130808224649343?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130808224649343?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp; 
 &nbsp;&nbsp;修改后的APK能够正常安装，如下图： 
 
 
 <img src="https://img-blog.csdn.net/20130808224947250?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130808224947250?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130808224947250?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;这种修改方法能够防止逆向分析，如下图： 
 
 
 <img src="https://img-blog.csdn.net/20130808225047421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130808225047421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130808225047421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;通过异常我们应该可以看出为什么大于255个字符会报错了吧。 
 &nbsp;&nbsp;&nbsp;但是该种方式缺点是只能对付backsmali。&nbsp;IDA、Dex2jar、Androguard仍然能够正常工作。 
 &nbsp;&nbsp;&nbsp;该种方法易于检测和解决，当class名字长度&gt;255要警惕该应用。 
 &nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;3、插入无效字节码指令引发逆向工具崩溃 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;由于大部分逆向工具都是线性读取字节码并解析，当遇到无效字节码时，就会引起反编译工具字节码解析失败。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们可以插入无效字节码到DEX文件，但要保证该无效字节码永远不会被执行（否则您的程序就会崩溃了！）。 
 &nbsp;&nbsp; 
 [java]&nbsp;view&nbsp;plaincopy 
 1201&nbsp;//&nbsp;Load&nbsp;0&nbsp;into&nbsp;v1&nbsp;&nbsp; 
 3801&nbsp;0300&nbsp;//&nbsp;A&nbsp;conditional&nbsp;jump&nbsp;which&nbsp;should&nbsp;always&nbsp;succeed,&nbsp;jumps&nbsp;over&nbsp;&nbsp; 
 //&nbsp;next&nbsp;bytes&nbsp;&nbsp; 
 FFFF&nbsp;//&nbsp;Bad&nbsp;opcodes&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;安装插入无效字节码的apk文件。如下图： 
 
 
 <img src="https://img-blog.csdn.net/20130809001741093?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130809001741093?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130809001741093?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;但是执行程序时，却报如下的错误： 
 &nbsp;&nbsp; 
 &nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130809002006546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130809002006546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130809002006546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;运行的时候怎么会报错呢？ 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dalvik虚拟机并没有像我们预想的那样跳过无效的字节码，它会在执行之前验证所有调用序列上类的字节码是否有效。 
 &nbsp;&nbsp;&nbsp;现在的问题是如何能够绕过Dalvik虚拟机的代码验证呢？ 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们如果插入无效代码在一个从来不会调用的类上不就可以绕过Dalvik运行时代码验证了吗！ 
 &nbsp;&nbsp;&nbsp;看如下插入后的运行结果： 
 
 <img src="https://img-blog.csdn.net/20130810085818421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810085818421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810085818421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;哈哈，成功运行了，接下来让我们看看该种方式反逆向的效果吧！ 
 
 <img src="https://img-blog.csdn.net/20130810090131953?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810090131953?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810090131953?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;（可惜的backsmali已经在版本2f81aec886d2修复了该bug，该方式已无效） 
 
 &nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130810090414312?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810090414312?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810090414312?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;Dex2jar&nbsp;验证可行。 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130810090533406?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810090533406?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810090533406?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;Androguard验证可行，（可惜的是Androguard很快修复了该bug） 
 
 
 <img src="https://img-blog.csdn.net/20130810090802906?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810090802906?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810090802906?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;IDA验证未成功！ 
 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130810090943015?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810090943015?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810090943015?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;ded工具验证成功！在你杀死该工具进程之前，它将一直运行在无效字节码所在类处理过程中。 
 &nbsp; 
 &nbsp;&nbsp;&nbsp;该种方法的缺点是很容易被工具修复。工具在反编译代码时，只要忽略会无效字节码的处理即可，backsmali、androgurad已经修复了该bug。 
 &nbsp;&nbsp;&nbsp;该种方式和很容易被自动化监测，如果遇到无效代码就要警惕！ 
 &nbsp;&nbsp;&nbsp;逆向分析人员要尽量使用工具的最新版本。 
 
 &nbsp;&nbsp;&nbsp;4、插入有效的字节码指令但后跟无效的数据引用 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;插入无效的字节码指令目前工具已经可以正常工作，但是如果我们插入有效的字节码指令，但是后跟无效的数据引用，结果会是怎么样呢？ 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 [cpp]&nbsp;view&nbsp;plaincopy 
 1201&nbsp;//&nbsp;Load&nbsp;0&nbsp;into&nbsp;v1&nbsp;&nbsp; 
 3801&nbsp;0300&nbsp;//&nbsp;A&nbsp;conditional&nbsp;jump&nbsp;which&nbsp;should&nbsp;always&nbsp;succeed,&nbsp;jumps&nbsp;over&nbsp;&nbsp; 
 //&nbsp;next&nbsp;bytes&nbsp;&nbsp; 
 1a00&nbsp;FF00&nbsp;//&nbsp;Load&nbsp;const-string&nbsp;at&nbsp;index&nbsp;255&nbsp;(doesn’t&nbsp;exist)&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;这次我们仍然绕过Dalvik运行时字节码指令验证，但是我们替换“无效字节码指令”为合法字节码指令 
 
 <img src="https://img-blog.csdn.net/20130810093016750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810093016750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810093016750?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;backsmali验证成功！ 
 
 <img src="https://img-blog.csdn.net/20130810093113671?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810093113671?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810093113671?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dex2jar验证成功！ 
 
 <img src="https://img-blog.csdn.net/20130810093236031?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810093236031?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810093236031?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;Androguard验证成功，但是只会在反编译插入该“有效字节码指令”的方法报错。 
 
 <img src="https://img-blog.csdn.net/20130810093647421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810093647421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810093647421?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;ded验证成功！ 
 
 &nbsp;&nbsp;&nbsp;&nbsp; 
 <img src="https://img-blog.csdn.net/20130810093748437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810093748437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810093748437?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp;&nbsp;&nbsp;IDA验证失败！ 
 
 &nbsp;&nbsp;该种方式也很容易被工具修复，逆向工具只要不盲目的解析一个不存在的索引即可。 
 
 &nbsp;&nbsp;&nbsp;5、针对java反编译器缺陷进行攻击 
 &nbsp;&nbsp;dex2jar+(JD-Gui或JAD)&nbsp;组合工具是逆向分析经常使用的工具。dex2jar用于把DEX文件转换为java字节码JAR文件，JD-GUI或JAD用于把java字节码转化为java源代码。 
 &nbsp;&nbsp;我们可以针对JAVA&nbsp;JD-Gui或JAD工具缺陷来达到反逆向分析的目的。达到的效果如下图所示： 
 
 <img src="https://img-blog.csdn.net/20130810122804265?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130810122804265?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130810122804265?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;6、针对backsmali对文件头处理缺陷 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们刚才讲到baksmali在处理Link&nbsp;section的bug，还有类似的崩溃点吗？如图backsmali代码所示： 
 
 <img src="https://img-blog.csdn.net/20130803142118765?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130803142118765?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130803142118765?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;当DEX&nbsp;Header&nbsp;size&nbsp;不等于0x70时，backsmali也会抛出异常退出！ 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Header_size&nbsp;当前值正常情况下都等于0x70 
 
 <img src="https://img-blog.csdn.net/20130803142436984?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130803142436984?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130803142436984?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;构建这种dex文件很容易实现。 
 &nbsp;&nbsp;&nbsp;需要修复文件头每个表项的偏移量。 
 &nbsp;&nbsp;&nbsp;修改后的Header&nbsp;size&nbsp;等于0x78 
 
 <img src="https://img-blog.csdn.net/20130803143224156?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130803143224156?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130803143224156?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;但是这种方式只能针对baksamli工具。且很工具很容易修复该bug。 
 &nbsp;&nbsp;&nbsp;该方式也可以用于在DEX&nbsp;Header中隐藏数据和代码。 
 &nbsp;&nbsp;&nbsp;我们可以在Dex文件头隐藏另一个DEX数据并在运行时加载附带DEX数据。 
 &nbsp;&nbsp;&nbsp;构建非规范的Dex文件 
 
 <img src="https://img-blog.csdn.net/20130728214717734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130728214717734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130728214717734?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;&nbsp;&nbsp;&nbsp;通过反射调用DexFile类的方法加载附带DEX数据（android4.0以上才有我们需要的方&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;法http://blog.csdn.net/androidsecurity/article/details/9674251） 
 
 
 <img src="https://img-blog.csdn.net/20130728215147468?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130728215147468?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130728215147468?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp;&nbsp; 
 &nbsp;&nbsp;通过反射实际调用DexFile的openDexFile方法 
 
 <img src="https://img-blog.csdn.net/20130803121206546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130803121206546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130803121206546?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 &nbsp;该种方式允许我们通过byte[]解析dex数据，而无须在再把DEX数据存储在设备的某个文件。 
 &nbsp;我们可以从安装APK文件、内存或dalvik-cache等读取dex数据。 
 &nbsp;打包好的DEX文件如下图所示： 
 
 <img src="https://img-blog.csdn.net/20130803122316609?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130803122316609?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130803122316609?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvYW5kcm9pZHNlY3VyaXR5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 &nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;该种方式将给自动化分析工具带来一个问题，自动化工具会按照dex格式处理DEX文件而不会处理附带的dex数据。需要特定的工具、16进制编辑器或手工提取嵌入的dex数据。 
 &nbsp;我们可以采用各种不同的方式增加嵌入数据的提取难度，比如： 
 &nbsp;&nbsp;&nbsp;&nbsp;对嵌入的DEX数据进行加密； 
 &nbsp;&nbsp;&nbsp;&nbsp;嵌入的DEX数据加密后在对其进行ZIP压缩； 
 &nbsp;&nbsp;&nbsp;&nbsp;使用native代码解密，直接从内存加载； 
 &nbsp;&nbsp;&nbsp;&nbsp;......等等 
 
 &nbsp;&nbsp;&nbsp;&nbsp;该种隐藏方式可以通过判断Dex文件头长度是否大于0x70检测。 
 &nbsp; 
 &nbsp;&nbsp;&nbsp;&nbsp;7、大端小端反转理论 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;当前还没有Android逆向工具实现DEX文件端反转（也许IDA支持）。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dalvik虚拟机在DEX优化过程中会检测DEX端模式是否适合当前设备，如果不适合会反转DEX文件端模式。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;我们需要做的是变换DEX文件所有字节端结构，反转后的DEX文件可以中断逆向工具但是仍然可以在设备上运行。 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;这种攻击方式理论上是可行的。我们可以参考Android源代码实现端的反转，具体代码位于/dalvik2/libdex/dexSwapAndVerify.cpp 
 
 四、反虚拟机技术 
 
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;如何检测App运行环境是否为qemu虚拟机呢?&nbsp;我们可以通过getprop获取相关信息，getprop在qemu虚拟机和移动设备上很多属性是不同的。比如： 
 
 &nbsp; 
 <img src="https://img-blog.csdn.net/20130725235326875?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235326875?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235326875?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 getprop&nbsp;Android&nbsp;SDK中并没有公开接口，不过我们可以通过JAVA反射调用。 
 
 <img src="https://img-blog.csdn.net/20130725235034453?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="https://img-blog.csdn.net/20130725235034453?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" title="https://img-blog.csdn.net/20130725235034453?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvamlhemhpanVu/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"> 
 
 五、相关引用 
 http://code.google.com/p/smali/ 
 http://code.google.com/p/androguard/ 
 http://code.google.com/p/dex2jar/ 
 http://siis.cse.psu.edu/ded/ 
 http://hex-rays.com/products/ida/index.shtml 
 http://source.android.com/tech/dalvik/dex-format.html&nbsp; 
 
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