How to hook RuntimeException to prevent crashes?

Question

I tried to find out how RuntimeException works internally in cs.android.com so I can understand how to prevent crashes but didn't find anything useful and I have no clue how to analyze components-related JDK in perspective of reverse engineering, I'm curious what's going on behind RuntimeException so I can prevent crashes

I tried with this Frida script but no luck

Java.perform(function() {
    var RuntimeException = Java.use('java.lang.RuntimeException');
    RuntimeException.$init.overload().implementation = function(){
        console.log("hits .overload()")
        return;
    }
    
    RuntimeException.$init.overload('java.lang.String').implementation = function(arg1){
        console.log("hits .overload('java.lang.String')")
        return;
    }
    
    RuntimeException.$init.overload('java.lang.Throwable').implementation = function(arg1){
        console.log("hits .overload('java.lang.Throwable')")
        return;
    }
    
    RuntimeException.$init.overload('java.lang.String', 'java.lang.Throwable').implementation = function(arg1,arg2){
        console.log("hits .overload('java.lang.String', 'java.lang.Throwable')")
        return;
    }
    
    RuntimeException.$init.overload('java.lang.String', 'java.lang.Throwable', 'boolean', 'boolean').implementation = function(arg1,arg2,arg3,arg4){
        console.log("hits .overload('java.lang.String', 'java.lang.Throwable', 'boolean', 'boolean')")
        return;
    }
    
})

Answer 1

RuntimeException is an Exception class like all the others, the only difference is that developers are not forced to catch RuntimeException and its child classes. And there is no special relation between RuntimeException and "native calls" (JNI calls).

Your problems are independent of the RuntimeException instead they are located in your Frida hooking code:

When hooking an Java/Android method (or constructor) the Frida hook replaces the original function. So if you just want to log method/constructor calls you always have to manually execute the original method inside the hook.

At the moment you don't call the original constructor of RuntimeException and return nothing, which means if Android tries to create an instance of RuntimeException no exception instance is created. This can never happen in compiled Java code and in the end the app crashes.

Therefore you have to modify your hooking code to call the original constructor and return the created RuntimeException instance:

let RuntimeException = Java.use('java.lang.RuntimeException');
let RTctor1 = RuntimeException.$init.overload();
RTctor1.implementation = function() {
    console.log("hits .overload()");
    return RTctor1.call(this);
}
let RTctor2 = RuntimeException.$init.overload('java.lang.String');
RTctor2.implementation = function(arg0) {
    console.log("hits .overload('java.lang.String')");
    return RTctor2.call(this, arg0);
}
...