Let’s first have a look at the challenge:

First, let’s extract the binaries from the apk:

apktool d allsafe.apk -o allsafe/

It loads the function checkPassword from the file libnative_library.so, let’s grab this file. Remember to take the one that correspond to your emulator architecture:

I opened this libnative_library.so inside Ghidra:

Let’s hook this function, and change the return value to true.

Java.perform(function(){
    const checkPass_address = Process.findModuleByName("libnative_library.so").findExportByName("Java_infosecadventures_allsafe_challenges_NativeLibrary_checkPassword");
    Interceptor.attach(checkPass_address, {
        onLeave: function(retval){
            retval.replace(1);
        }
    })

})

Now, Execute with frida:

frida -U -N infosecadventures.allsafe -l ./frida-script.js