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**Bug bounty tip**: **sign up** for **Intigriti**, a premium **bug bounty platform created by hackers, for hackers**! Join us at [**https://go.intigriti.com/hacktricks**](https://go.intigriti.com/hacktricks) today, and start earning bounties up to **$100,000**! {% embed url="https://go.intigriti.com/hacktricks" %} **This is a summary of the post**: [https://11x256.github.io/Frida-hooking-android-part-2/](https://11x256.github.io/Frida-hooking-android-part-2/) (Parts 2, 3 & 4)\ **APKs and Source code**: [https://github.com/11x256/frida-android-examples](https://github.com/11x256/frida-android-examples) The part 1 is so easy. **Some parts of the original code doesn't work and have been modified here.** ## Part 2 Here you can see an example of how to **hook 2 functions with the same name** but different parameters.\ Also, you are going to learn how to **call a function with your own parameters**.\ And finally, there is an example of how to **find an instance of a class and make it call a function**. ```javascript //s2.js console.log("Script loaded successfully "); Java.perform(function x() { console.log("Inside java perform function"); var my_class = Java.use("com.example.a11x256.frida_test.my_activity"); //Hook "fun" with parameters (int, int) my_class.fun.overload("int", "int").implementation = function (x, y) { //hooking the old function console.log("original call: fun(" + x + ", " + y + ")"); var ret_value = this.fun(2, 5); return ret_value; }; //Hook "fun" with paramater(String) var string_class = Java.use("java.lang.String"); my_class.fun.overload("java.lang.String").implementation = function (x) { //hooking the new function console.log("*") //Create a new String and call the function with your input. var my_string = string_class.$new("My TeSt String#####"); console.log("Original arg: " + x); var ret = this.fun(my_string); console.log("Return value: " + ret); console.log("*") return ret; }; //Find an instance of the class and call "secret" function. Java.choose("com.example.a11x256.frida_test.my_activity", { onMatch: function (instance) { console.log(tring, and the it has"Found instance: " + instance); console.log("Result of secret func: " + instance.secret()); }, onComplete: function () { } }); }); ``` You can see that to create a String first is has referenced the class _java.lang.String_ and then it has created a _$new_ object of that class with a String as content. This is the correct way to create a new object of a class. But, in this case, you could just pass to `this.fun()` any String like: `this.fun("hey there!")` ### Python ```python //loader.py import frida import time device = frida.get_usb_device() pid = device.spawn(["com.example.a11x256.frida_test"]) device.resume(pid) time.sleep(1) #Without it Java.perform silently fails session = device.attach(pid) script = session.create_script(open("s2.js").read()) script.load() #prevent the python script from terminating raw_input() ``` ``` python loader.py ``` ## Part 3 ### Python Now you are going to see how to send commands to the hooked app via Python to call function: ```python //loader.py import time import frida def my_message_handler(message, payload): print message print payload device = frida.get_usb_device() pid = device.spawn(["com.example.a11x256.frida_test"]) device.resume(pid) time.sleep(1) # Without it Java.perform silently fails session = device.attach(pid) with open("s3.js") as f: script = session.create_script(f.read()) script.on("message", my_message_handler) script.load() command = "" while 1 == 1: command = raw_input("Enter command:\n1: Exit\n2: Call secret function\n3: Hook Secret\nchoice:") if command == "1": break elif command == "2": script.exports.callsecretfunction() elif command == "3": script.exports.hooksecretfunction() ``` The command "**1**" will **exit**, the command "**2**" will find and **instance of the class and call the private function** _**secret()**_ and command "**3**" will **hook** the function _**secret()**_ so it **return** a **different string**. The, if you call "**2**" you will get the **real secret**, but if you call "**3**" and then "**2**" you will get the **fake secret**. ### JS ```javascript console.log("Script loaded successfully "); var instances_array = []; function callSecretFun() { Java.perform(function () { if (instances_array.length == 0) { // if array is empty Java.choose("com.example.a11x256.frida_test.my_activity", { onMatch: function (instance) { console.log("Found instance: " + instance); instances_array.push(instance) console.log("Result of secret func: " + instance.secret()); }, onComplete: function () { } }); } else {//else if the array has some values console.log("Result of secret func: " + instances_array[0].secret()); } }); } function hookSecret() { Java.perform(function () { var my_class = Java.use("com.example.a11x256.frida_test.my_activity"); var string_class = Java.use("java.lang.String"); my_class.secret.overload().implementation = function(){ var my_string = string_class.$new("TE ENGANNNNEEE"); return my_string; } }); } rpc.exports = { callsecretfunction: callSecretFun, hooksecretfunction: hookSecret }; ``` ## Part 4 Here you will see how to make **Python and JS interact** using JSONs objects. JS use the `send()` function to send data to the python cliente, and Python uses `post()` functions to send data to ths JS script. The **JS will block the execution** until is receives s response from Python. ### Python ```python //loader.py import time import frida def my_message_handler(message, payload): print message print payload if message["type"] == "send": print message["payload"] data = message["payload"].split(":")[1].strip() print 'message:', message data = data.decode("base64") user, pw = data.split(":") data = ("admin" + ":" + pw).encode("base64") print "encoded data:", data script.post({"my_data": data}) # send JSON object print "Modified data sent" device = frida.get_usb_device() pid = device.spawn(["com.example.a11x256.frida_test"]) device.resume(pid) time.sleep(1) session = device.attach(pid) with open("s4.js") as f: script = session.create_script(f.read()) script.on("message", my_message_handler) # register the message handler script.load() raw_input() ``` ### JS ```javascript console.log("Script loaded successfully "); Java.perform(function () { var tv_class = Java.use("android.widget.TextView"); tv_class.setText.overload('java.lang.CharSequence').implementation = function (x) { var string_to_send = x.toString(); var string_to_recv = ""; send(string_to_send); // send data to python code recv(function (received_json_object) { string_to_recv = received_json_object.my_data; }).wait(); //block execution till the message is received console.log("Final string_to_recv: "+ string_to_recv) return this.setText(string_to_recv); } }); ``` There is a part 5 that I am not going to explain because there isn't anything new. But if you want to read it is here: [https://11x256.github.io/Frida-hooking-android-part-5/](https://11x256.github.io/Frida-hooking-android-part-5/)
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