Frida脚本详解与实战指南<\/h1>

一、Frida基础概念<\/h2>

1.1 什么是Hook<\/h3>
Hook（钩子）是一种在程序运行时拦截和修改函数行为的技术。在Frida中，我们可以通过编写脚本来"钩住"目标函数，实现参数修改、返回值替换、函数调用监控等操作。<\/p>

1.2 Frida脚本基本框架<\/h3>
Java<\/span>.perform<\/span>(function<\/span> () {
<\/span><\/span>    \/\/ 在这里编写hook代码
<\/span><\/span><\/span><\/span>    console<\/span>.log<\/span>("Frida脚本已附加到进程"<\/span>);
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>
Java.perform(fn)<\/code>：确保当前线程连接到Java虚拟机并执行回调函数<\/li>
console.log()<\/code>：在控制台输出信息<\/li>
JavaScript语法：对缩进无要求，分号可选<\/li>
<\/ul>
二、Frida核心API详解<\/h2>
2.1 获取Java类<\/h3>
Java<\/span>.use<\/span>("完整类名"<\/span>)
<\/span><\/span><\/code><\/pre>示例：<\/p>
var<\/span> LoginActivity<\/span> =<\/span> Java<\/span>.use<\/span>("com.example.LoginActivity"<\/span>);
<\/span><\/span><\/code><\/pre>2.2 主动调用函数<\/h3>
var<\/span> result<\/span> =<\/span> LoginActivity<\/span>.a<\/span>("123"<\/span>, "123"<\/span>);
<\/span><\/span>console<\/span>.log<\/span>(result<\/span>);
<\/span><\/span><\/code><\/pre>2.3 修改函数实现<\/h3>
LoginActivity<\/span>.a<\/span>.implementation<\/span> =<\/span> function<\/span>(x<\/span>, y<\/span>) {
<\/span><\/span>    \/\/ 修改原始逻辑
<\/span><\/span><\/span><\/span>    return<\/span> "修改后的返回值"<\/span>;
<\/span><\/span>};
<\/span><\/span><\/code><\/pre>2.4 调用非静态函数<\/h3>
Java<\/span>.choose<\/span>("com.example.TargetClass"<\/span>, {
<\/span><\/span>    onMatch<\/span>:<\/span> function<\/span>(instance<\/span>) {
<\/span><\/span>        instance<\/span>.nonStaticMethod<\/span>();
<\/span><\/span>    },
<\/span><\/span>    onComplete<\/span>:<\/span> function<\/span>() {
<\/span><\/span>        console<\/span>.log<\/span>("搜索完成"<\/span>);
<\/span><\/span>    }
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>2.5 修改成员变量<\/h3>
instance<\/span>._variableName<\/span>.value<\/span> =<\/span> newValue<\/span>;
<\/span><\/span><\/code><\/pre>注意：当成员变量名与函数名相同时，需要在变量名前加下划线<\/p>
2.6 处理动态加载的Dex<\/h3>
Java<\/span>.enumerateClassLoaders<\/span>({
<\/span><\/span>    onMatch<\/span>:<\/span> function<\/span>(loader<\/span>) {
<\/span><\/span>        try<\/span> {
<\/span><\/span>            if<\/span> (loader<\/span>.findClass<\/span>("动态加载的类名"<\/span>)) {
<\/span><\/span>                Java<\/span>.classFactory<\/span>.loader<\/span> =<\/span> loader<\/span>;
<\/span><\/span>            }
<\/span><\/span>        } catch<\/span> (e<\/span>) {}
<\/span><\/span>    },
<\/span><\/span>    onComplete<\/span>:<\/span> function<\/span>() {}
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>三、实战场景与解决方案<\/h2>
3.1 场景一：修改返回值绕过验证<\/h3>
问题<\/strong>：函数返回的字符串与固定值比较，需要修改返回值使其匹配<\/p>
解决方案<\/strong>：<\/p>
TargetClass<\/span>.targetMethod<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>    return<\/span> "需要匹配的固定值"<\/span>;
<\/span><\/span>};
<\/span><\/span><\/code><\/pre>3.2 场景二：调用非静态方法<\/h3>
问题<\/strong>：需要调用没有static修饰的成员方法<\/p>
解决方案<\/strong>：<\/p>
Java<\/span>.choose<\/span>("com.example.TargetClass"<\/span>, {
<\/span><\/span>    onMatch<\/span>:<\/span> function<\/span>(instance<\/span>) {
<\/span><\/span>        instance<\/span>.setBool_var<\/span>();
<\/span><\/span>    },
<\/span><\/span>    onComplete<\/span>:<\/span> function<\/span>() {}
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>3.3 场景三：修改成员变量<\/h3>
问题<\/strong>：需要修改类的成员变量值<\/p>
解决方案<\/strong>：<\/p>
Java<\/span>.choose<\/span>("com.example.TargetClass"<\/span>, {
<\/span><\/span>    onMatch<\/span>:<\/span> function<\/span>(instance<\/span>) {
<\/span><\/span>        instance<\/span>._bool_var<\/span>.value<\/span> =<\/span> true<\/span>;
<\/span><\/span>    }
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>3.4 场景四：Hook动态加载的类<\/h3>
问题<\/strong>：目标类通过DexClassLoader动态加载，直接Hook会找不到类<\/p>
解决方案<\/strong>：<\/p>

枚举所有类加载器<\/li>
找到能加载目标类的loader<\/li>
设置当前classFactory的loader<\/li>
<\/ol>
Java<\/span>.enumerateClassLoaders<\/span>({
<\/span><\/span>    onMatch<\/span>:<\/span> function<\/span>(loader<\/span>) {
<\/span><\/span>        try<\/span> {
<\/span><\/span>            if<\/span> (loader<\/span>.findClass<\/span>("com.example.DynamicCheck"<\/span>)) {
<\/span><\/span>                Java<\/span>.classFactory<\/span>.loader<\/span> =<\/span> loader<\/span>;
<\/span><\/span>                var<\/span> DynamicCheck<\/span> =<\/span> Java<\/span>.use<\/span>("com.example.DynamicCheck"<\/span>);
<\/span><\/span>                DynamicCheck<\/span>.check<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>                    return<\/span> true<\/span>;
<\/span><\/span>                };
<\/span><\/span>            }
<\/span><\/span>        } catch<\/span> (e<\/span>) {}
<\/span><\/span>    }
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>3.5 场景五：从Native层获取数据<\/h3>
问题<\/strong>：关键数据（如加密密钥）存储在native层<\/p>
解决方案<\/strong>：<\/p>
\/\/ Hook native方法获取key
<\/span><\/span><\/span><\/span>var<\/span> NativeClass<\/span> =<\/span> Java<\/span>.use<\/span>("com.example.NativeHelper"<\/span>);
<\/span><\/span>NativeClass<\/span>.getKey<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>    var<\/span> original<\/span> =<\/span> this<\/span>.getKey<\/span>();
<\/span><\/span>    console<\/span>.log<\/span>("获取到Key: "<\/span> +<\/span> original<\/span>);
<\/span><\/span>    return<\/span> original<\/span>;
<\/span><\/span>};
<\/span><\/span>
<\/span><\/span>\/\/ Hook native方法获取IV
<\/span><\/span><\/span><\/span>NativeClass<\/span>.getIV<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>    var<\/span> original<\/span> =<\/span> this<\/span>.getIV<\/span>();
<\/span><\/span>    console<\/span>.log<\/span>("获取到IV: "<\/span> +<\/span> original<\/span>);
<\/span><\/span>    return<\/span> original<\/span>;
<\/span><\/span>};
<\/span><\/span><\/code><\/pre>四、CTF实战案例解析<\/h2>
4.1 案例一：SHA256验证绕过<\/h3>
题目逻辑<\/strong>：<\/p>

a方法接受两个相同参数，返回第一个参数的SHA256值<\/li>
验证条件：username的SHA256值与password相等<\/li>
<\/ul>
解决方案<\/strong>：<\/p>
Java<\/span>.perform<\/span>(function<\/span> () {
<\/span><\/span>    var<\/span> LoginActivity<\/span> =<\/span> Java<\/span>.use<\/span>("com.example.LoginActivity"<\/span>);
<\/span><\/span>    var<\/span> result<\/span> =<\/span> LoginActivity<\/span>.a<\/span>("123"<\/span>, "123"<\/span>);
<\/span><\/span>    console<\/span>.log<\/span>("Password should be: "<\/span> +<\/span> result<\/span>);
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>4.2 案例二：字符串比较绕过<\/h3>
题目逻辑<\/strong>：<\/p>

函数返回的字符串与固定值比较<\/li>
需要修改返回值使其匹配<\/li>
<\/ul>
解决方案<\/strong>：<\/p>
TargetClass<\/span>.a<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>    return<\/span> "R4jSLLLLLLLLLLOrLE7\/5B+Z6fsl65yj6BgC6YWz66gO6g2t65Pk6a+P65NK44NNROl0wNOLLLL="<\/span>;
<\/span><\/span>};
<\/span><\/span><\/code><\/pre>4.3 案例三：动态DEX检查绕过<\/h3>
题目逻辑<\/strong>：<\/p>

check方法在动态加载的DEX中实现<\/li>
需要Hook动态加载的类的方法<\/li>
<\/ul>
解决方案<\/strong>：<\/p>
Java<\/span>.perform<\/span>(function<\/span>() {
<\/span><\/span>    Java<\/span>.enumerateClassLoaders<\/span>({
<\/span><\/span>        onMatch<\/span>:<\/span> function<\/span>(loader<\/span>) {
<\/span><\/span>            try<\/span> {
<\/span><\/span>                if<\/span> (loader<\/span>.findClass<\/span>("com.example.DynamicCheck"<\/span>)) {
<\/span><\/span>                    Java<\/span>.classFactory<\/span>.loader<\/span> =<\/span> loader<\/span>;
<\/span><\/span>                    var<\/span> DynamicCheck<\/span> =<\/span> Java<\/span>.use<\/span>("com.example.DynamicCheck"<\/span>);
<\/span><\/span>                    DynamicCheck<\/span>.check<\/span>.implementation<\/span> =<\/span> function<\/span>() {
<\/span><\/span>                        return<\/span> true<\/span>;
<\/span><\/span>                    };
<\/span><\/span>                }
<\/span><\/span>            } catch<\/span> (e<\/span>) {}
<\/span><\/span>        }
<\/span><\/span>    });
<\/span><\/span>});
<\/span><\/span><\/code><\/pre>五、最佳实践与技巧<\/h2>

错误处理<\/strong>：在Hook脚本中加入try-catch块防止崩溃<\/li>
调试输出<\/strong>：使用console.log输出关键信息<\/li>
多线程处理<\/strong>：确保在主线程执行Java.perform<\/li>
性能考虑<\/strong>：避免在频繁调用的函数中实现复杂逻辑<\/li>
脚本模块化<\/strong>：将常用功能封装为函数便于复用<\/li>
<\/ol>
六、总结<\/h2>
Frida提供了强大的动态插桩能力，掌握以下核心技能：<\/p>

理解Java.perform的作用和用法<\/li>
熟练使用Java.use获取目标类<\/li>
掌握implementation修改函数实现<\/li>
了解Java.choose处理非静态方法<\/li>
能够处理动态加载的DEX<\/li>
熟悉从Native层获取数据的方法<\/li>
<\/ul>
通过实际CTF题目练习，可以快速提升Frida脚本编写能力，灵活应对各种逆向分析场景。<\/p>
Frida脚本详解与实战指南<\/h1>

一、Frida基础概念<\/h2>

1.1 什么是Hook<\/h3> Hook（钩子）是一种在程序运行时拦截和修改函数行为的技术。在Frida中，我们可以通过编写脚本来"钩住"目标函数，实现参数修改、返回值替换、函数调用监控等操作。<\/p>

二、Frida核心API详解<\/h2>

三、实战场景与解决方案<\/h2>

四、CTF实战案例解析<\/h2>

1.1 什么是Hook<\/h3>
Hook（钩子）是一种在程序运行时拦截和修改函数行为的技术。在Frida中，我们可以通过编写脚本来"钩住"目标函数，实现参数修改、返回值替换、函数调用监控等操作。<\/p>
