Friday, November 20, 2020

AWS EC2 & Quick FTP Server

 Sometimes you just need to transfer some files back and forth over FTP and want something quick and easy. There are a couple of caveats to getting a one-liner-ish FTP server running in AWS EC2 or lightsail:

  1. Additional ports must be opened. Lightsail by default opens 80 & 22. You'll have to also open 21 & 8000-9000 for the following to work. Or you know, open it all because yolo.
  2. File transfers must happen in FTP passive mode. This is the default mode of pftp and lftp on Kali. If you use the basic ftp binary, you have to issue the "passive" command after you connect.
Here are the commands to quick-start:

Wednesday, July 15, 2020

Python Debugging: Output Function Name and Args

Sprinkling print statements everywhere gets annoying so here is a decorator that does 99% of what I need when it comes to debugging function input.

Wednesday, February 26, 2020

Simple DLL To Pop A CMD Shell

Below is some sample code to pop a cmd shell upon execution of the DLL. Pretty great for testing various code injection techniques. Compile it as a DLL project in Visual Studio to generate the .dll file.

Wednesday, February 12, 2020

A Better, More Modern, HTML Link Grabber

Lots of examples of HTML <a> link grabbers simply parse the source code of the page for a links and output that. I'm sure I don't need to say that technique is antiquated and doesn't really work that well with modern web applications and front-end frameworks. Everybody and their mother just loves modifying HTML using javascript. The old method would miss that stuff badly.

Take the following HTML file for example:

            <a href="">html-link</a>
            <a id=jsalink href=placeholder>jsalink</a>
            var jslink = document.getElementById("jsalink")
            jslink.href = ""

There are obviously two A links there, but one of them is being modified by JS. This dynamic modification of elements is extremely common today. So what happens if you use the old method of getting A links?

$ curl localhost:8000/jsalink.html 2>/dev/null | grep '<a'
            <a href="">html-link</a>
            <a id=jsalink href=placeholder>jsalink</a>

Well that obviously didn't work... How about using the BeautifulSoup python module?

$ python3 http://localhost:8000/jsalink.html

Also no...The best way i've found to do it is to actually have a browser engine parse the entire file and execute the JS, and then grab all the a links by issuing a command to the JS interpreter. I wrote the following script to do exactly that. It uses the Chrome browser in headless mode to perform all the parsing, and then via selenium, issues a JS statement to grab all the A links:

Running this results in:

$ python3 http://localhost:8000/jsalink.html

That's more like it.

PS. This is still not "perfect" since certain frameworks will change content via certain event handlers. This handles some (e.g. DOMContentLoaded), but not others (e.g. onclick events). You kinda just have to deal with that. Making a script to identify changes based on all event handlers would likely be extremely risky.