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shabbir jaorawala

What is BurpSuite?
Burp Suite is a Java based Web Penetration Testing framework. It has become an industry standard suite of tools used by information security professionals. Burp Suite helps you identify vulnerabilities and verify attack vectors that are affecting web applications. Because of its popularity and breadth as well as depth of features, we have created this useful page as a collection of Burp Suite knowledge and information.

In its simplest form, Burp Suite can be classified as an Interception Proxy. While browsing their target application, a penetration tester can configure their internet browser to route traffic through the Burp Suite proxy server. Burp Suite then acts as a (sort of) Man In The Middle by capturing and analyzing each request to and from the target web application so that they can be analyzed.

Everyone has their favorite security tools, but when it comes to mobile and web applications I've always found myself looking BurpSuite . It always seems to have everything I need and for folks just getting started with web application testing it can be a challenge putting all of the pieces together. I'm just going to go through the installation to paint a good picture of how to get it up quickly.

BurpSuite is freely available with everything you need to get started and when you're ready to cut the leash, the professional version has some handy tools that can make the whole process a little bit easier. I'll also go through how to install FoxyProxy which makes it much easier to change your proxy setup, but we'll get into that a little later.

Requirements and assumptions:

Mozilla Firefox 3.1 or Later Knowledge of Firefox Add-ons and installation The Java Runtime Environment installed

Download BurpSuite from http://portswigger.net/burp/download.htmland make a note of where you save it.

on for Firefox from https://addons.mozilla.org/en-US/firefox/addon/foxyproxy-standard/

If this is your first time running the JAR file, it may take a minute or two to load, so be patient and wait.

Video for setup and installation.

You need to install compatible version of java , So that you can run BurpSuite.

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shabbir jaorawala

1. Overview

Is an elf32 static and stripped binary, but the good news is that it was compiled with gcc and it will not have shitty runtimes and libs to fingerprint, just the libc ... and libprhrhead
This binary is writed by Ricardo J Rodrigez

When it's executed, it seems that is computing the flag:

But this process never ends .... let's see what strace say:

There is a thread deadlock, maybe the start point can be looking in IDA the xrefs of 0x403a85
Maybe we can think about an encrypted flag that is not decrypting because of the lock.

This can be solved in two ways:

static: understanding the cryptosystem and programming our own decryptor
dynamic: fixing the the binary and running it (hard: antidebug, futex, rands ...)

At first sight I thought that dynamic approach were quicker, but it turned more complex than the static approach.

2. Static approach

Crawling the xrefs to the futex, it is possible to locate the main:

With libc/libpthread function fingerprinting or a bit of manual work, we have the symbols, here is the main, where 255 threads are created and joined, when the threads end, the xor key is calculated and it calls the print_flag:

The code of the thread is passed to the libc_pthread_create, IDA recognize this area as data but can be selected as code and function.

This is the thread code decompiled, where we can observe two infinite loops for ptrace detection and preload (although is static) this antidebug/antihook are easy to detect at this point.

we have to observe the important thing, is the key random?? well, with the same seed the random sequence will be the same, then the key is "hidden" in the predictability of the random.

If the threads are not executed on the creation order, the key will be wrong because is xored with the th_id which is the identify of current thread.

The print_key function, do the xor between the key and the flag_cyphertext byte by byte.

And here we have the seed and the first bytes of the cypher-text:

With radare we can convert this to a c variable quickly:

And here is the flag cyphertext:

And with some radare magics, we have the c initialized array:

radare, is full featured :)

With a bit of rand() calibration here is the solution ...

The code:
https://github.com/NocONName/CTF_NcN2k15/blob/master/theAnswer/solution.c

3. The Dynamic Approach

First we have to patch the anti-debugs, on beginning of the thread there is two evident anti-debugs (well anti preload hook and anti ptrace debugging) the infinite loop also makes the anti-debug more evident:

There are also a third anti-debug, a bit more silent, if detects a debugger trough the first available descriptor, and here comes the fucking part, don't crash the execution, the execution continues but the seed is modified a bit, then the decryption key will not be ok.

Ok, the seed is incremented by one, this could be a normal program feature, but this is only triggered if the fileno(open("/","r")) > 3 this is a well known anti-debug, that also can be seen from a traced execution.

Ok, just one byte patch, seed+=1 to seed+=0, (add eax, 1 to add eax, 0)

before:

after:

To patch the two infinite loops, just nop the two bytes of each jmp $-0

Ok, but repairing this binary is harder than building a decryptor, we need to fix more things:

The sleep(randInt(1,3)) of the beginning of the thread to execute the threads in the correct order
Modify the pthread_cond_wait to avoid the futex()
We also need to calibrate de rand() to get the key (just patch the sleep and add other rand() before the pthread_create loop

Adding the extra rand() can be done with a patch because from gdb is not possible to make a call rand() in this binary.

With this modifications, the binary will print the key by itself.

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shabbir jaorawala

How do I get started with bug bounty hunting? How do I improve my skills?

These are some simple steps that every bug bounty hunter can use to get started and improve their skills:

Learn to make it; then break it!
A major chunk of the hacker's mindset consists of wanting to learn more. In order to really exploit issues and discover further potential vulnerabilities, hackers are encouraged to learn to build what they are targeting. By doing this, there is a greater likelihood that hacker will understand the component being targeted and where most issues appear. For example, when people ask me how to take over a sub-domain, I make sure they understand the Domain Name System (DNS) first and let them set up their own website to play around attempting to "claim" that domain.

Read books. Lots of books.
One way to get better is by reading fellow hunters' and hackers' write-ups. Follow /r/netsec and Twitter for fantastic write-ups ranging from a variety of security-related topics that will not only motivate you but help you improve. For a list of good books to read, please refer to "What books should I read?".

Join discussions and ask questions.
As you may be aware, the information security community is full of interesting discussions ranging from breaches to surveillance, and further. The bug bounty community consists of hunters, security analysts, and platform staff helping one and another get better at what they do. There are two very popular bug bounty forums: Bug Bounty Forum and Bug Bounty World.

Participate in open source projects; learn to code.
Go to https://github.com/explore or https://gitlab.com/explore/projects and pick a project to contribute to. By doing so you will improve your general coding and communication skills. On top of that, read https://learnpythonthehardway.org/ and https://linuxjourney.com/.

Help others. If you can teach it, you have mastered it.
Once you discover something new and believe others would benefit from learning about your discovery, publish a write-up about it. Not only will you help others, you will learn to really master the topic because you can actually explain it properly.

Smile when you get feedback and use it to your advantage.
The bug bounty community is full of people wanting to help others so do not be surprised if someone gives you some constructive feedback about your work. Learn from your mistakes and in doing so use it to your advantage. I have a little physical notebook where I keep track of the little things that I learnt during the day and the feedback that people gave me.

Learn to approach a target.
The first step when approaching a target is always going to be reconnaissance — preliminary gathering of information about the target. If the target is a web application, start by browsing around like a normal user and get to know the website's purpose. Then you can start enumerating endpoints such as sub-domains, ports and web paths.

A woodsman was once asked, "What would you do if you had just five minutes to chop down a tree?" He answered, "I would spend the first two and a half minutes sharpening my axe."
As you progress, you will start to notice patterns and find yourself refining your hunting methodology. You will probably also start automating a lot of the repetitive tasks.

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Sunday, August 30, 2020

BurpSuite Introduction & Installation

NcN 2015 CTF - theAnswer Writeup

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How Do I Get Started With Bug Bounty ?

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