Green VPN及加密文件逆向分析实战教学文档<\/h1>

1. 引言<\/h2>
本教学文档详细讲解如何对Green VPN软件进行逆向分析，定位其加密配置文件（如module.ini、system.ini等）的解密算法，并最终实现对这些加密文件的解密过程。该技术可用于网络安全分析、取证调查等合法用途。<\/p>

2. 分析目标<\/h2>

目标软件：Green VPN<\/li>
加密文件：module.ini、system.ini、module_en.ini等配置文件<\/li>

分析目的：解密这些文件获取服务器地址等关键信息<\/li> <\/ul>

3. 分析思路<\/h2>

基本原理<\/strong>：软件运行时必须将加密配置文件解密为明文才能使用<\/li>
关键假设<\/strong>：可执行文件中必然包含解密代码段<\/li>

突破口<\/strong>：通过文件读取API定位解密代码位置<\/li> <\/ol>
4. 工具准备<\/h2>

Ollydbg（或OllyICE）：用于动态调试和分析<\/li>
十六进制编辑器：用于查看文件内容<\/li>
C语言编译器：用于实现解密算法<\/li> <\/ul>
5. 详细分析步骤<\/h2>
5.1 初步定位解密代码位置<\/h3>

使用Ollydbg加载Green.exe<\/li>
查找ReadFile API调用点

这是关键，因为软件需要读取加密文件<\/li> <\/ul> <\/li>
在所有ReadFile API调用处设置断点<\/li> <\/ol>
5.2 动态调试过程<\/h3>

运行程序并触发断点<\/li>
观察读取system.ini文件的过程：

文件内容被读取到内存缓冲区（如00185D48）<\/li> <\/ul> <\/li>
跟踪该缓冲区的硬件访问：

在Ollydbg中对内存地址右键→"断点"→"硬件访问"<\/li> <\/ul> <\/li>
单步执行直到发现解密代码段<\/li> <\/ol>
5.3 解密算法分析<\/h3>
通过调试发现解密过程的核心汇编代码：<\/p>
mov al, [esi] ; 从内存读取一个字节到AL寄存器 xor al, 0xBD ; 与0xBD进行异或操作 add al, 0x69 ; 加上0x69 mov [esi], al ; 将结果存回内存 inc esi ; 移动到下一个字节 dec eax ; 计数器减1 jnz short loc_xxxx ; 循环直到处理完所有字节 <\/code><\/pre> 解密算法特点：<\/p> 逐字节处理<\/li> 每个字节先与0xBD异或<\/li> 然后加上0x69<\/li> 循环处理整个文件<\/li> <\/ul> 5.4 C语言实现解密算法<\/h3> #include<\/span> <stdio.h><\/span> <\/span><\/span><\/span>#include<\/span> <stdlib.h><\/span> <\/span><\/span><\/span><\/span> <\/span><\/span>\/\/ 解密函数 <\/span><\/span><\/span><\/span>void<\/span> decrypt<\/span>(unsigned<\/span> char<\/span>*<\/span> data, int<\/span> length) { <\/span><\/span> for<\/span>(int<\/span> i =<\/span> 0<\/span>; i <<\/span> length; i++<\/span>) { <\/span><\/span> data[i] ^=<\/span> 0xBD<\/span>; <\/span><\/span> data[i] +=<\/span> 0x69<\/span>; <\/span><\/span> } <\/span><\/span>} <\/span><\/span> <\/span><\/span>\/\/ 读取文件函数 <\/span><\/span><\/span><\/span>unsigned<\/span> char<\/span>*<\/span> readfile<\/span>(const<\/span> char<\/span>*<\/span> filename, int<\/span>*<\/span> length) { <\/span><\/span> FILE*<\/span> file =<\/span> fopen(filename, "rb"<\/span>); <\/span><\/span> if<\/span>(!<\/span>file) return<\/span> NULL; <\/span><\/span> <\/span><\/span> fseek(file, 0<\/span>, SEEK_END); <\/span><\/span> *<\/span>length =<\/span> ftell(file); <\/span><\/span> fseek(file, 0<\/span>, SEEK_SET); <\/span><\/span> <\/span><\/span> unsigned<\/span> char<\/span>*<\/span> buffer =<\/span> (unsigned<\/span> char<\/span>*<\/span>)malloc(*<\/span>length); <\/span><\/span> fread(buffer, 1<\/span>, *<\/span>length, file); <\/span><\/span> fclose(file); <\/span><\/span> <\/span><\/span> return<\/span> buffer; <\/span><\/span>} <\/span><\/span> <\/span><\/span>\/\/ 写入文件函数 <\/span><\/span><\/span><\/span>int<\/span> writefile<\/span>(const<\/span> char<\/span>*<\/span> filename, unsigned<\/span> char<\/span>*<\/span> data, int<\/span> length) { <\/span><\/span> FILE*<\/span> file =<\/span> fopen(filename, "wb"<\/span>); <\/span><\/span> if<\/span>(!<\/span>file) return<\/span> 0<\/span>; <\/span><\/span> <\/span><\/span> fwrite(data, 1<\/span>, length, file); <\/span><\/span> fclose(file); <\/span><\/span> return<\/span> 1<\/span>; <\/span><\/span>} <\/span><\/span> <\/span><\/span>int<\/span> main<\/span>(int<\/span> argc, char<\/span>*<\/span> argv[]) { <\/span><\/span> if<\/span>(argc !=<\/span> 3<\/span>) { <\/span><\/span> printf("Usage: %s <input file> <output file><\/span>\n<\/span>"<\/span>, argv[0<\/span>]); <\/span><\/span> return<\/span> 1<\/span>; <\/span><\/span> } <\/span><\/span> <\/span><\/span> int<\/span> length =<\/span> 0<\/span>; <\/span><\/span> unsigned<\/span> char<\/span>*<\/span> data =<\/span> readfile(argv[1<\/span>], &<\/span>length); <\/span><\/span> if<\/span>(!<\/span>data) { <\/span><\/span> printf("Error reading file %s<\/span>\n<\/span>"<\/span>, argv[1<\/span>]); <\/span><\/span> return<\/span> 1<\/span>; <\/span><\/span> } <\/span><\/span> <\/span><\/span> decrypt(data, length); <\/span><\/span> <\/span><\/span> if<\/span>(!<\/span>writefile(argv[2<\/span>], data, length)) { <\/span><\/span> printf("Error writing file %s<\/span>\n<\/span>"<\/span>, argv[2<\/span>]); <\/span><\/span> free(data); <\/span><\/span> return<\/span> 1<\/span>; <\/span><\/span> } <\/span><\/span> <\/span><\/span> free(data); <\/span><\/span> printf("File %s decrypted successfully to %s<\/span>\n<\/span>"<\/span>, argv[1<\/span>], argv[2<\/span>]); <\/span><\/span> return<\/span> 0<\/span>; <\/span><\/span>} <\/span><\/span><\/code><\/pre>5.5 使用解密程序<\/h3> 编译上述C代码生成可执行文件<\/li> 命令行用法： decryptor <加密文件路径> <输出文件路径> <\/code><\/pre> <\/li> 示例： decryptor system.ini system_decrypted.ini <\/code><\/pre> <\/li> <\/ol> 6. 结果验证<\/h2> 解密后的文件应包含明文配置信息，如：<\/p> 服务器地址<\/li> 端口号<\/li> 更新源地址<\/li> 其他连接参数<\/li> <\/ul> 7. 技术要点总结<\/h2> API断点法<\/strong>：通过关键API（如ReadFile）定位相关代码段<\/li> 内存跟踪<\/strong>：通过硬件访问断点跟踪数据处理过程<\/li> 算法逆向<\/strong>：从汇编代码还原高级语言算法<\/li> 循环处理<\/strong>：注意识别循环结构及其终止条件<\/li> 字节操作<\/strong>：关注XOR、ADD等字节级操作指令<\/li> <\/ol> 8. 扩展思考<\/h2> 加密变种<\/strong>：实际分析中可能遇到更复杂的加密算法多轮变换<\/li> 密钥派生<\/li> 动态密钥<\/li> <\/ul> <\/li> 反调试技术<\/strong>：软件可能采用反调试措施需要绕过检测<\/li> 使用更隐蔽的调试方法<\/li> <\/ul> <\/li> 自动化分析<\/strong>：可开发IDA Python脚本自动化部分分析过程<\/li> <\/ol> 9. 注意事项<\/h2> 本技术仅用于合法用途<\/li> 实际分析中加密算法可能不同，需灵活调整<\/li> 建议在隔离环境中进行分析<\/li> 保留完整的分析记录和证据链<\/li> <\/ol> 10. 参考资料<\/h2> 《逆向工程核心原理》<\/li> Ollydbg官方文档<\/li> Windows API参考手册<\/li> x86汇编语言指南<\/li> <\/ol> 本教学文档详细记录了从逆向分析到算法实现的完整过程，可作为类似加密文件分析任务的参考模板。实际应用中需根据具体情况调整分析方法和技术手段。<\/p>

Green VPN及加密文件逆向分析实战教学文档<\/h1>

1. 引言<\/h2> 本教学文档详细讲解如何对Green VPN软件进行逆向分析，定位其加密配置文件（如module.ini、system.ini等）的解密算法，并最终实现对这些加密文件的解密过程。该技术可用于网络安全分析、取证调查等合法用途。<\/p>

5. 详细分析步骤<\/h2>

1. 引言<\/h2>
本教学文档详细讲解如何对Green VPN软件进行逆向分析，定位其加密配置文件（如module.ini、system.ini等）的解密算法，并最终实现对这些加密文件的解密过程。该技术可用于网络安全分析、取证调查等合法用途。<\/p>