fridax: Export not found: `mono_aot_get_method` in JIT-compiled APK

Hello,

I can’t get the modify_class_function_argument.js script to work.

I’m working with this app: https://github.com/xamarin/xamarin-forms-samples/tree/master/WebServices/TodoREST

I’m trying to intercerpt the GetTasksAsync function of the TodoItemManager:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace TodoREST
{
	public class TodoItemManager
	{
		IRestService restService;

		public TodoItemManager (IRestService service)
		{
			restService = service;
		}

		public Task<List<TodoItem>> GetTasksAsync ()
		{
			return restService.RefreshDataAsync ();	
		}

		public Task SaveTaskAsync (TodoItem item, bool isNewItem = false)
		{
			return restService.SaveTodoItemAsync (item, isNewItem);
		}

		public Task DeleteTaskAsync (TodoItem item)
		{
			return restService.DeleteTodoItemAsync (item.ID);
		}
	}
}

Source for the class: https://github.com/xamarin/xamarin-forms-samples/blob/master/WebServices/TodoREST/TodoREST/Data/TodoItemManager.cs

I’m using this script:

import { MonoApiHelper, MonoApi } from '../vendors/frida-mono-api'
import ClassHelper from '../libraries/class_helper'

// Intercept settings
var settingClassName = "TodoREST.TodoItemManager";
var settingMethodName = "GetTasksAsync";
var settingMethodArgCount = 0;

// The root AppDomain is the initial domain created by the runtime when it is initialized. Programs execute on this AppDomain.
const domain = MonoApi.mono_get_root_domain()

console.log('domain: ' + classInformation);

// Get a reference to a certain class within the Xamarin application.
var classInformation = ClassHelper.getClassByName(settingClassName);

console.log('classInformation: ' + classInformation);

// Get the pointer to the ahead-of-time (AOT) compiled method
let methodInformation = MonoApiHelper.ClassGetMethodFromName(classInformation, settingMethodName, settingMethodArgCount)

console.log('methodInformation: ' + methodInformation);

// Allocate enough memory for MonoError initialization
let monoErrorMemory = Memory.alloc(32) 

// Get the pointer to the method
let nativeMethodPointer = MonoApi.mono_aot_get_method(domain, methodInformation, monoErrorMemory)

// Attach interceptor and fish out the first method argument
Interceptor.attach(nativeMethodPointer, {
    onEnter: function(args) {
        console.log("Entered " + settingMethodName + " with " + settingMethodArgCount + " argument(s).");
        console.log("Value of `string id`: " + MonoApiHelper.StringToUtf8(args[3]));

        args[3] = MonoApiHelper.StringNew('This is the replaced value of `string c`.', domain);
    },
    onLeave: function onLeave(log, retval, state) {
        console.log("Left " + settingMethodName + ".");
    }
})

console.log(`'modify_function_argument.js' attached and ready.`)

The stacktrace I’m getting:

node fridax.js inject --scripts scripts/todo-modify.js
[*] Awaiting storage initialization.
[*] Awaiting USB device.
[*] Up and running on Android Emulator 5554.
? Which application do you want to inject? TodoREST
[*] Happy hacking.
[*] Attached to application (session: 3803).
[*] Injected a test script (this runs from within the injected application)!
domain: undefined
classInformation: 0x98f63330
methodInformation: 0x84b95058
Error: Export not found: mono_aot_get_method
    at vendors/frida-mono-api/mono-api.js:799
    at scripts/todo-modify.js:45
    at o (node_modules/browser-pack/_prelude.js:1)
    at r (node_modules/browser-pack/_prelude.js:1)
    at /script2.js:1217
^C[*] Script unloaded.
[*] Script unloaded.```

If you need more info let me know.