# Frida Tutorial 2
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**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/)
If you are interested in **hacking career** and hack the unhackable - **we are hiring!** (_fluent polish written and spoken required_).
{% embed url="https://www.stmcyber.com/careers" %}
☁️ HackTricks Cloud ☁️ -🐦 Twitter 🐦 - 🎙️ Twitch 🎙️ - 🎥 Youtube 🎥
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** 🐦[**@carlospolopm**](https://twitter.com/hacktricks_live)**.**
* **Share your hacking tricks by submitting PRs to the [hacktricks repo](https://github.com/carlospolop/hacktricks) and [hacktricks-cloud repo](https://github.com/carlospolop/hacktricks-cloud)**.
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