文章转自先知社区:https://xz.aliyun.com/t/13220
作者:0x0101
1、环境及背景
pixel 2
某app (***企业版加固)
frida 15.1.28
启用frida并更改端口没有发现检测行为但是直接hook会闪退
打印so 调用堆栈
function hook_pthread(){var pthread_create_addr = Module.findExportByName(null, 'pthread_createvar pthread_create = new NativeFunction(pthread_create_addr, "int", ["pointer", "pointer", "pointer", "pointer"]);Interceptor.replace(pthread_create_addr, new NativeCallback(function (parg0, parg1, parg2, parg3) {var so_name = Process.findModuleByAddress(parg2).name;var so_path = Process.findModuleByAddress(parg2).path;var so_base = Module.getBaseAddress(so_name);var offset = parg2 - so_base;var PC = 0;if ((so_name.indexOf("libexec.so") > -1)) {console.log("find thread func offset", so_name, offset);} else {PC = pthread_create(parg0, parg1, parg2, parg3);}return PC;}, "int", ["pointer", "pointer", "pointer", "pointer"]))}hook_pthread();
找到了libexec.so开启pthread_create的偏移量,对其进行bypass,即
function hook_pthread() {var pthread_create_addr = Module.findExportByName(null, 'pthread_create');var pthread_create = new NativeFunction(pthread_create_addr, "int", ["pointer", "pointer", "pointer", "pointer"]);Interceptor.replace(pthread_create_addr, new NativeCallback(function (parg0, parg1, parg2, parg3) {var so_name = Process.findModuleByAddress(parg2).name;var so_path = Process.findModuleByAddress(parg2).path;var so_base = Module.getBaseAddress(so_name);var offset = parg2 - so_base;var PC = 0;if ((so_name.indexOf("libexec.so") > -1)) {console.log("find thread func offset", so_name, offset);if ((207076 === offset)) {console.log("anti bypass");} else if (207308 === offset) {console.log("anti bypass");} else if (283820 === offset) {console.log("anti bypass");} else if (286488 === offset) {console.log("anti bypass");} else if (292416 === offset) {console.log("anti bypass");} else if (78136 === offset) {console.log("anti bypass");} else if (293768 === offset) {console.log("anti bypass");} else {PC = pthread_create(parg0, parg1, parg2, parg3);}} else {PC = pthread_create(parg0, parg1, parg2, parg3);}return PC;}, "int", ["pointer", "pointer", "pointer", "pointer"]))}hook_pthread();
已经对其进行绕过frida的检测。
绕过frida的检测之后,开始对其加载的class以及class中的函数进行遍历
Java.enumerateLoadedClasses({onMatch: function(className) {console.log("found class >> " + className);//遍历类中所有的方法和属性var jClass = Java.use(className);console.log(JSON.stringify({_name: className,_methods: Object.getOwnPropertyNames(jClass.__proto__).filter(function(m) {return !m.startsWith('$') // filter out Frida related special properties|| m == 'class' || m == 'constructor' // optional}),_fields: jClass.class.getFields().map(function(f) {return f.toString()})}, null, 2));//遍历类中所有的方法和属性},onComplete: function() {console.log("[*] class enuemration complete");}});
class和函数大部分已经被遍历出来了,但是由于是加固的,部分函数并没有被加载出来(意料之中),利用常规的框架尝试去执行
//框架为if(Java.available) {Java.perform(function(){var application = Java.use("android.app.Application");application.attach.overload('android.content.Context').implementation = function(context) {var result = this.attach(context); // 先执行原来的attach方法var classloader = context.getClassLoader(); // 获取classloaderJava.classFactory.loader = classloader;var Hook_class = Java.classFactory.use("com.xxx.xxx"); // app的类console.log("Hook_class: " + Hook_class);// 下面代码和写正常的hook一样Hook_class.函数.implementation = function() // 有参数填参数{}return result;}});}
发现会执行不成功,说明加固后的app没有用常规的classloader去加载函数。因此需要去遍历在加载app的时候,是哪些classloader被加载
1、可以通过重加载指定classloader去使得脱壳后的源码能在内存中被找到
2、可以一次性重加载所有调用的classloader去执行
//获取加固的classloader并hook函数Java.enumerateClassLoaders({onMatch: function(loader){// 每次匹配到,都要把匹配到的赋值给java默认的loaderJava.classFactory.loader = loader;var TryClass;// console.log(loader); // 输出被加载的classloader// 没报错就hook到了,报错了就hook下一个,如果全都报错了,没打印东西,那可能就是hook错了。try{ // 每一次加载尝试是否可以找到想要的classTryClass = Java.use("cn.xxx"); // 需要被加载之后查询的类TryClass.xx.implementation = function(p1,p2){ // 类的函数console.log('p1:'+p1)console.log('p2:'+p2)return this.xx(p1,p2)}}catch(error){if(error.message.includes("ClassNotFoundException")){console.log(" You are trying to load encrypted class, trying next loader");}else{console.log(error.message);}}},onComplete: function(){}})
用2的方法被加载成功。
最终成功实现在***企业版中去hook数据,当然这需要成功的脱壳之后查看原app存在哪些函数才行。依靠遍历出来的class
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