JS逆向对抗教学文档：签名绕过技术详解<\/h1>

1. 签名验证机制概述<\/h2>
签名验证是Web应用中常见的安全防护手段，通过验证请求参数的完整性来防止数据篡改。当客户端发起请求时，会按照特定算法生成签名（sign），服务端收到请求后重新计算签名并进行比对，若不一致则拒绝请求。<\/p>

2. 逆向分析核心思路<\/h2>

2.1 关键参数定位策略<\/h3>

避免常见关键字<\/strong>：直接搜索"sign"等常见参数会返回过多结果，降低效率<\/li>
利用稀有参数<\/strong>：优先搜索"noncestr"、"timestamp"等不常见但相关的参数进行间接定位<\/li>

参数关联性<\/strong>：同一请求的签名参数通常集中出现在相近代码区域<\/li> <\/ul>
2.2 代码分析技巧<\/h3>

在浏览器开发者工具中使用全局搜索功能（Ctrl+Shift+F）<\/li>
找到参数位置后设置断点进行动态调试<\/li>
通过控制台打印中间变量值验证分析结果<\/li> <\/ul>
3. 实际渗透测试案例解析<\/h2>
3.1 签名参数识别<\/h3>
目标请求包含以下关键参数：<\/p>

noncestr<\/code>：随机字符串<\/li>
timestamp<\/code>：时间戳<\/li>
sign<\/code>：签名值（核心验证参数）<\/li> <\/ul> 3.2 加密逻辑定位过程<\/h3> 全局搜索"noncestr"定位到唯一匹配项<\/li> 在相邻代码中发现sign参数生成逻辑<\/li> 设置断点分析参数传递流程<\/li> <\/ol> 3.3 签名生成算法分析<\/h3> 加密函数调用链：<\/p> f() → s() → 最终签名生成 <\/code><\/pre> 关键代码结构：<\/p> c<\/span> =<\/span> function<\/span>(e<\/span>, n<\/span>) { <\/span><\/span> var<\/span> r<\/span> =<\/span> t<\/span>.wordsToBytes<\/span>(s<\/span>(e<\/span>)); <\/span><\/span> return<\/span> n<\/span> &&<\/span> n<\/span>.asBytes<\/span> ?<\/span> r<\/span> :<\/span> n<\/span> &&<\/span> n<\/span>.asString<\/span> ?<\/span> i<\/span>.bytesToString<\/span>(r<\/span>) :<\/span> t<\/span>.bytesToHex<\/span>(r<\/span>) <\/span><\/span>} <\/span><\/span><\/code><\/pre>3.4 完整签名生成流程<\/h3> f<\/span> =<\/span> function<\/span>() { <\/span><\/span> \/\/ 参数处理 <\/span><\/span><\/span><\/span> var<\/span> e<\/span> =<\/span> arguments<\/span>[0<\/span>] ||<\/span> {}; <\/span><\/span> var<\/span> o<\/span> =<\/span> t<\/span>({}, e<\/span>); <\/span><\/span> <\/span><\/span> \/\/ 时间戳和随机数生成 <\/span><\/span><\/span><\/span> o<\/span>.timestamp<\/span> =<\/span> Date.now<\/span>() +<\/span> l<\/span>; <\/span><\/span> o<\/span>.noncestr<\/span> =<\/span> c<\/span>(8<\/span>, "number"<\/span>); <\/span><\/span> <\/span><\/span> \/\/ 待签名字符串拼接 <\/span><\/span><\/span><\/span> var<\/span> f<\/span> =<\/span> Object.keys<\/span>(o<\/span>).filter<\/span>(...) <\/span><\/span> .concat<\/span>("appSignKey"<\/span>) <\/span><\/span> .sort<\/span>() <\/span><\/span> .map<\/span>((function<\/span>(e<\/span>) { <\/span><\/span> return<\/span> ""<\/span>.concat<\/span>(e<\/span>, "="<\/span>).concat<\/span>(i<\/span>[e<\/span>] ||<\/span> o<\/span>[e<\/span>] ||<\/span> ""<\/span>) <\/span><\/span> })) <\/span><\/span> .join<\/span>("&"<\/span>); <\/span><\/span> <\/span><\/span> \/\/ 生成签名 <\/span><\/span><\/span><\/span> o<\/span>.sign<\/span> =<\/span> s<\/span>(f<\/span>); <\/span><\/span> return<\/span> o<\/span>; <\/span><\/span>} <\/span><\/span><\/code><\/pre>4. Python签名伪造实现<\/h2> 4.1 核心加密函数还原<\/h3> import<\/span> hashlib <\/span><\/span> <\/span><\/span>def<\/span> generate_sign<\/span>(sign_str): <\/span><\/span> """ <\/span><\/span><\/span> 核心SHA1加密方法 (还原JS里的s()函数) <\/span><\/span><\/span> :param sign_str: 拼接好的待签名原始字符串 <\/span><\/span><\/span> :return: 小写的sha1签名结果 <\/span><\/span><\/span> """<\/span> <\/span><\/span> sha1 =<\/span> hashlib.<\/span>sha1() <\/span><\/span> sha1.<\/span>update(sign_str.<\/span>encode('utf-8'<\/span>)) <\/span><\/span> return<\/span> sha1.<\/span>hexdigest() <\/span><\/span><\/code><\/pre>4.2 完整签名生成示例<\/h3> def<\/span> generate_complete_signature<\/span>(params): <\/span><\/span> """ <\/span><\/span><\/span> 生成完整签名包 <\/span><\/span><\/span> :param params: 原始请求参数 <\/span><\/span><\/span> :return: 包含有效签名的参数字典 <\/span><\/span><\/span> """<\/span> <\/span><\/span> import<\/span> time <\/span><\/span> import<\/span> random <\/span><\/span> <\/span><\/span> # 添加必要参数<\/span> <\/span><\/span> params['timestamp'<\/span>] =<\/span> int(time.<\/span>time() *<\/span> 1000<\/span>) <\/span><\/span> params['noncestr'<\/span>] =<\/span> ''<\/span>.<\/span>join(random.<\/span>choices('0123456789'<\/span>, k=<\/span>8<\/span>)) <\/span><\/span> <\/span><\/span> # 构造待签名字符串<\/span> <\/span><\/span> sign_params =<\/span> {k: v for<\/span> k, v in<\/span> params.<\/span>items() if<\/span> v not<\/span> in<\/span> [None<\/span>, ''<\/span>]} <\/span><\/span> sign_params['appSignKey'<\/span>] =<\/span> '4bTogwpz7RzNO2VTFtW7zcfRkAE97ox6ZSgcQi7FgYdqrHqKB7aGqEZ4o7yssa2a'<\/span> <\/span><\/span> <\/span><\/span> # 按参数名排序并拼接<\/span> <\/span><\/span> sorted_keys =<\/span> sorted(sign_params.<\/span>keys()) <\/span><\/span> sign_str =<\/span> '&'<\/span>.<\/span>join([f<\/span>"<\/span>{<\/span>key}<\/span>=<\/span>{<\/span>sign_params[key]}<\/span>"<\/span> for<\/span> key in<\/span> sorted_keys]) <\/span><\/span> <\/span><\/span> # 生成签名<\/span> <\/span><\/span> params['sign'<\/span>] =<\/span> generate_sign(sign_str) <\/span><\/span> return<\/span> params <\/span><\/span><\/code><\/pre>5. AI辅助分析技术<\/h2> 5.1 代码还原优化<\/h3> 将复杂的JS加密代码提供给AI进行分析<\/li> AI可自动识别算法逻辑并生成对应语言实现<\/li> 减少手动代码还原的工作量和错误率<\/li> <\/ul> 5.2 验证方法<\/h3> 使用已知输入输出对验证还原算法的正确性<\/li> 对比JS原生执行结果与还原代码结果<\/li> 确保编码格式、大小写等细节完全一致<\/li> <\/ul> 6. 绕过验证实战步骤<\/h2> 6.1 准备工作<\/h3> 配置浏览器开发者工具<\/li> 准备Python运行环境及相关加密库<\/li> 捕获目标网站的正常请求样本<\/li> <\/ol> 6.2 具体实施流程<\/h3> 信息收集<\/strong>：分析请求参数结构，识别签名相关参数<\/li> 代码定位<\/strong>：使用稀有参数搜索法快速定位加密逻辑<\/li> 逻辑分析<\/strong>：通过断点调试理清参数传递和加密流程<\/li> 算法还原<\/strong>：提取核心加密函数并用Python重写<\/li> 签名伪造<\/strong>：构造任意参数并生成有效签名<\/li> 验证测试<\/strong>：使用伪造签名发送请求确认绕过成功<\/li> <\/ol> 7. 防御对策与注意事项<\/h2> 7.1 增强签名安全性的建议<\/h3> 使用动态变化的appSignKey<\/li> 加入请求时效性验证（防止重放攻击）<\/li> 增加客户端环境检测机制<\/li> 采用非标准加密算法或自定义混淆<\/li> <\/ul> 7.2 法律与道德规范<\/h3> 仅限授权测试环境中使用该技术<\/li> 遵守相关法律法规和测试协议<\/li> 测试完成后及时向相关方报告漏洞<\/li> <\/ul> 8. 技术总结<\/h2> JS逆向的核心价值在于理解前端加密逻辑，通过参数定位、代码分析和算法还原三个关键步骤，能够有效突破签名验证机制的防护。结合AI辅助分析可以大幅提升效率，但技术思路和分析方法的掌握才是最重要的核心能力。<\/p> 该方法论不仅适用于签名绕过场景，还可应用于各种前端加密逆向分析，是渗透测试人员的重要技能之一。<\/p>