【Frida Hook 學習記錄】Frida Hook Android 常用方法

1 概述

在逆向過程中，Frida是非常常用的Hook工具，這個工具在日常使用的過程中，有很多通用方法，這裏記錄一下，方便查閱，部分函數使用的時候，可能需要稍微修改一下，本文記錄是Android的方法，不涉及其他的
主要是搬遷的一下參考文章的片段
Android逆向之旅—Hook神器家族的Frida工具使用詳解
Frida官方文檔
看雪 Frida官方手冊 - JavaScript API（篇一）
看雪 Frida官方手冊 - JavaScript API（篇二）
Js中幾種String Byte轉換方法
Frida learn by example

2 啓動方式

2.1 使用js腳本啓動

 frida -U -l exploit.js -f com.package.name 

其中js腳本的寫作方式如下

setImmediate(function() { //prevent timeout
    console.log("[*] Starting script");

    Java.perform(function() {
      myClass = Java.use("com.package.name.xxActivity");
      myClass.implementation = function(v) {
         // do sth.
      }

    })
})

2.2 使用python腳本啓動

import frida, sys

def on_message(message, data):
    if message['type'] == 'send':
        print("[*] {0}".format(message['payload']))
    else:
        print(message)

jscode = """
Java.perform(function () {
    // Function to hook is defined here
    var MainActivity = Java.use('com.example.hook.MainActivity');
    // hook method is setString
    MainActivity.setString.implementation = function (str) {
        // Show a message to know that the function got called
        send('hook success');
        console.log('string is: ' + str));
    };
});
"""

process = frida.get_usb_device().attach('com.example.hook')
#pid = device.spawn(["com.android.chrome"])
#session = device.attach(pid)
#device.resume(pid)
script = process.create_script(jscode)
script.on('message', on_message)
print('[*] Hook Start Running')
script.load()
sys.stdin.read()

3 Android 常用Hook方法彙總

3.1 Hook 一般函數—使用implementation

var MainActivity = Java.use('ese.xposedtest.MainActivity');
//外部類 修改返回值
MainActivity.OutClass.implementation = function (arg) {
    var ret = this.OutClass(arg);
    console.log('Done:' + arg);
    return ret;
}

3.2 Hook 重載函數—使用overload

// If two methods of a class have the same name
// you need to use 'overload'
// hook method 1
myClass.myMethod.overload().implementation = function(){
  // do sth
}

myClass.myMethod.overload("[B", "[B").implementation = function(param1, param2) {
  // do sth
}

myClass.myMethod.overload("android.context.Context", "boolean").implementation = function(param1, param2){
  // do sth
}

// hook method 2
//待補充

3.3 Hook 構造函數—使用$init

// Intercept the initialization of java.lang.Stringbuilder's overloaded constructor.
// Write the partial argument to the console.
const StringBuilder = Java.use('java.lang.StringBuilder');
//We need to overwrite .$init() instead of .$new(), since .$new() = .alloc() + .init()
StringBuilder.$init.overload('java.lang.String').implementation = function (arg) {
    var partial = "";
    var result = this.$init(arg);
    if (arg !== null) {
         partial = arg.toString().replace('\n', '').slice(0,10);
    }
    // console.log('new StringBuilder(java.lang.String); => ' + result)
    console.log('new StringBuilder("' + partial + '");')
    return result;
}
console.log('[+] new StringBuilder(java.lang.String) hooked');

3.4 Hook 生成對象—使用$new

const JavaString = Java.use('java.lang.String');
var exampleString1 = JavaString.$new('Hello World, this is an example string in Java.');
console.log('[+] exampleString1: ' + exampleString1);

3.5 Hook 內部類—使用$

var inInnerClass = Java.use('ese.xposedtest.MainActivity$inInnerClass');

inInnerClass.methodInclass.implementation = function()
{
    var arg0 = arguments[0];
    var arg1 = arguments[1];
    send("params1: "+ arg0 +" params2: " + arg1);
    return this.formInclass(1,"Frida");
}

3.6 Hook native 函數

Interceptor.attach(Module.findExportByName("xxx.so" , "xxxx"), {
    onEnter: function(args) {
        send("open(" + Memory.readCString(args[0])+","+args[1]+")");
    },
    onLeave:function(retval){
    
    }
});

3.7 Hook 靜態變量

var ah = Java.use("com.ah");
console.log("To Log: " + ah.value);
ah.value = true;

3.8 打印堆棧

AndroidLog = Java.use("android.util.Log")
AndroidException = Java.use("java.lang.Exception")
function printStackTrace(){
	console.log(AndroidLog .getStackTraceString(AndroidException .$new()));
}

3.9 byte轉String

function byte2string(array){
    var result = "";
    for(var i = 0; i < array.length; ++i){
        result+= (String.fromCharCode(array[i]));
    }
   return result;
}

3.10 字符串轉Uint8Array

function string2byte(str){
  for (var i = 0,arr=[]; i < str.length;i++){
    arr.push(str.charCodeAt(i));
  }
  return new Uint8Array(arr);
}

3.11 int轉bytes

function intTobytes(n) {
  var bytes = [];
  for (var i = 0; i < 2; i++) {
    bytes[i] = n >> (8 - i * 8);
 
  }
  return bytes;
}

3.12 string轉ArrayBuffer

function str2arraybuffer(str) {
  var buf = new ArrayBuffer(str.length * 2); // 每個字符佔用2個字節
  var bufView = new Uint16Array(buf);
  for (var i = 0, strLen = str.length; i < strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}

3.13 ArrayBuffer轉String

function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint8Array(buf));
}

3.14 添加時間戳

 console.log(new Date(new Date().getTime())