Frida: How to send native method args value in onEnter function when hook native in Android

[lqxn1015]

this is my native code
Java_com_test_MainActivity_stringFromJNI(JNIEnv *env, jobject, jstring prompt) {
std::string hello = "Hello ";
const char *str = env->GetStringUTFChars(prompt, false);
std::string hello1 = hello + str;
jstring rtStr = env->NewStringUTF(hello1.c_str());
env->ReleaseStringUTFChars(prompt, str);
return rtStr;
}
////
how to send prompt value in onEnter function
onEnter: function onEnter(args) {
//how to send prompt value in here .
},

use python frida.
thanks!

[jhscheer]

To read from memory you need to know the start address and how many bytes to read.
So maybe something like this will help you figure it out:

    onEnter: function (args) 
    {
        var ptr_prompt = args[2];
        var length = args[3];    

        var data = Memory.readByteArray(ptr_promt, length);
        send(data);
    }

[lqxn1015]

@jhscheer not work .... thanks

[jhscheer]

I looked up how to do this for jstring and one possibility is:

    onEnter: function (args) 
    {
        var ptr_prompt = args[2];
        Java.perform( function () {
            var String = Java.use("java.lang.String");
            var promt = Java.cast(ptr(ptr_prompt), String);
            send(prompt);
        });
    }

[54kggo]

I looked up how to do this for jstring and one possibility is:

    onEnter: function (args) 
    {
        var ptr_prompt = args[2];
        Java.perform( function () {
            var String = Java.use("java.lang.String");
            var promt = Java.cast(ptr(ptr_prompt), String);
            send(prompt);
        });
    }

Very nice！This solved my big problem！