java.lang.NullPointerException when using Engine.BURP2

[mschwager]

I get the following error when using this Turbo Intruder script:

def queueRequests(target, wordlists):
    engine = RequestEngine(endpoint=target.endpoint,
                            concurrentConnections=1,
                            engine=Engine.BURP2
                            )
    
    for i in range(20):
        engine.queue(target.req, [i], gate='1')
    
    engine.openGate('1')

def handleResponse(req, interesting):
    table.add(req)

Ignoring error: java.lang.NullPointerException: Cannot invoke "burp.api.montoya.http.message.responses.HttpResponse.toByteArray()" because the return value of "burp.api.montoya.http.message.HttpRequestResponse.response()" is null

If I switch to Engine.BURP then I don't get the error.

Interestingly, if I use Engine.HTTP2, then a connection is made, but the process hangs forever with the requests queued.

This is after following along in the "Speed tuning" section of this article.

[albinowax]

Judging by the error message, the server isn't replying to the request so there's no much opportunity for Turbo Intruder to handle this differently. That said, I'd be interested to know what happens if you try to send the exact same request over HTTP/2 using Repeater.

[mschwager]

Judging by the error message, the server isn't replying to the request so there's no much opportunity for Turbo Intruder to handle this differently.

Sorry, I should've been more specific when I was originally creating the issue. It took me a long time to realize I had to change the engine when I was looking at the original error above. A NullPointerException isn't much to go off of when you should be considering the engine being used. It'd be really helpful if there was some kind of warning produced that suggested trying other engines if Turbo Intruder doesn't receive a response from the server 👍

I'm not sure if there's a more accurate way to predict whether you might need to change the engine or not, but I suppose a lack of response from the server is a start. Of course, there could be reasons other than an engine mismatch that causes the server to not respond, so I'm not sure what the best recommendation for the user would be here. Ultimately, I think handling the null response case, avoiding the NullPointerException, and giving the user some kind of nudge in the right direction would be very helpful.

That said, I'd be interested to know what happens if you try to send the exact same request over HTTP/2 using Repeater.

I tried this out and here's the response I got from the server:

HTTP/1.1 400 Bad Request
Content-Type: text/plain; charset=utf-8
Connection: close

400 Bad Request

So the server is responding to the HTTP/2 request with a HTTP/1.1 response 🤔. Perhaps that's the reason Engine.BURP2 is failing to process the response.

Thanks for all your help here! I'm definitely understanding the situation a lot better now.