Create jit_modify_class_function_argument.js

Author: tijme

examples/jit_modify_class_function_argument.js

@@ -0,0 +1,46 @@
+import { MonoApiHelper, MonoApi } from '../vendors/frida-mono-api'
+import ClassHelper from '../libraries/class_helper'
+
+/*
+    // For JIT-compiled applications only.
+    // This example script can intercept the following method (non-constructor).
+    // Furthermore it modifies the first argument (string id).
+
+    namespace CompanyName.ProjectName.Views.Web.Html {
+
+        class HtmlWebView {
+
+            GetElement(string id) {
+                // This function will be intercepted.
+            }
+
+        }
+
+    }
+*/
+
+// Intercept settings
+var settingClassName = "CompanyName.ProjectName.Views.Web.Html.HtmlWebView";
+var settingMethodName = "GetElement";
+var settingMethodArgCount = 1;
+
+// 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()
+
+// Get a reference to a certain class within the Xamarin application.
+var classInformation = ClassHelper.getClassByName(settingClassName);
+
+// Attach interceptor and fish out the first method argument
+MonoApiHelper.Intercept(classInformation, settingMethodName, {
+    onEnter: function(args) {
+        console.log("Entered " + settingMethodName + " with " + settingMethodArgCount + " argument(s).");
+        console.log("Value of `string id`: " + MonoApiHelper.StringToUtf8(args[1]));
+        
+        args[1] = MonoApiHelper.StringNew('This is the replaced value of `string id`.', domain);
+    },
+    onLeave: function onLeave(log, retval, state) {
+        console.log("Left " + settingMethodName + ".");
+    }
+})
+
+console.log(`'jit_modify_class_function_argument.js' attached and ready.`)