某企业版加固app绕过hook

一、环境及背景

pixel 2

某app （***企业版加固）

frida 15.1.28

二、hook绕过

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_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);
        } 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classloader
            Java.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