Going the other way with padding oracles: Encrypting arbitrary data!

A long time ago, I wrote a couple blogs that went into a lot of detail on how to use padding oracle vulnerabilities to decrypt an encrypted string of data. It's pretty important to understand to use a padding oracle vulnerability for decryption before reading this, so I'd suggest going there for a refresher. When […]

dnscat2 0.05: with tunnels!

Greetings, and I hope you're all having a great holiday! My Christmas present to you, the community, is dnscat2 version 0.05! Some of you will remember that I recently gave a talk at the SANS Hackfest Summit. At the talk, I mentioned some ideas for future plans. That's when Ed jumped on the stage and […]

dnscat2: now with crypto!

Hey everybody, Live from the SANS Pentest Summit, I'm excited to announce the latest beta release of dnscat2: 0.04! Besides some minor cleanups and UI improvements, there is one serious improvement: all dnscat2 sessions are now encrypted by default! Read on for some user information, then some implementation details for those who are interested! For […]

GitS 2015: Giggles (off-by-one virtual machine)

Welcome to part 3 of my Ghost in the Shellcode writeup! Sorry for the delay, I actually just moved to Seattle. On a sidenote, if there are any Seattle hackers out there reading this, hit me up and let's get a drink! Now, down to business: this writeup is about one of the Pwnage 300 […]

GitS 2015: aart.php (race condition)

Welcome to my second writeup for Ghost in the Shellcode 2015! This writeup is for the one and only Web level, "aart" (download it). I wanted to do a writeup for this one specifically because, even though the level isn't super exciting, the solution was actually a pretty obscure vulnerability type that you don't generally […]

Defcon Quals writeup for byhd (reversing a Huffman Tree)

This is my writeup for byhd, a 2-point challenge from the Defcon Qualifier CTF. You can get the files, including my annotated assembly file, here. This is my second (and final) writeup for the Defcon Qualifiers, you can find the writeup for shitsco here. This was a reverse engineering challenge where code would be constructed […]

Defcon Quals writeup for Shitsco (use-after-free vuln)

Hey folks, Apparently this blog has become a CTF writeup blog! Hopefully you don't mind, I still try to keep all my posts educational. Anyway, this is the first of two writeups for the Defcon CTF Qualifiers (2014). I only completed two levels, both of which were binary reversing/exploitation! This particular level was called "shitsco", […]

PlaidCTF writeup for Pwn-275 – Kappa (type confusion vuln)

Hey folks, This is my last writeup for PlaidCTF! You can get a list of all my writeups here. Kappa is a 275-point pwnable level called Kappa, and the goal is to capture a bunch of Pokemon and make them battle each other! Ultimately, this issue came down to a type-confusion bug that let us […]

PlaidCTF writeup for Pwn-200 (a simple overflow bug)

I know what you're thinking of: what's with all the Web levels!? Well, I was saving the exploitation levels for last! This post will be about Pwnable-200 (ezhp), and the next one will be Pwnable-275 (kappa). You can get the binary for ezhp here, and I highly recommend poking at this if you're interested in […]

PlaidCTF writeup for Web-300 – whatscat (SQL Injection via DNS)

Hey folks, This is my writeup for Whatscat, just about the easiest 300-point Web level I've ever solved! I wouldn't normally do a writeup about a level like this, but much like the mtpox level I actually wrote the exact tool for exploiting this, and even wrote a blog post about it almost exactly 4 […]

PlaidCTF writeup for Web-200 – kpop (bad deserialization)

Hello again! This is my second writeup from PlaidCTF this past weekend! It's for the Web level called kpop, and is about how to shoot yourself in the foot by misusing serialization (download the files). There are at least three levels I either solved or worked on that involved serialization attacks (mtpox, reeekeeeeee, and this […]

PlaidCTF writeup for Web-150 – mtpox (hash extension attack)

Hey folks, This is going to be my first of a couple writeups about this past weekend's CTF: PlaidCTF! My first writeup is for a 150-point Web level called mtpox. I chose this one to do first not only because it's the first level I completed, but also because the primary vulnerability was a hash […]

Ghost in the Shellcode: fuzzy (Pwnage 301)

Hey folks, It's a little bit late coming, but this is my writeup for the Fuzzy level from the Ghost in the Shellcode 2014 CTF! I kept putting off writing this, to the point where it became hard to just sit down and do it. But I really wanted to finish before PlaidCTF 2014, which […]

Ghost in the Shellcode: gitsmsg (Pwnage 299)

"It's Saturday night; I have no date, a 2L bottle of Shasta, and my all-rush mix tape. Let's rock!" ...that's what I said before I started gitsmsg. I then entered "Rush" into Pandora, and listened to a mix of Rush, Kansas, Queen, Billy Idol, and other 80's rock for the entire level. True story. Anyway, […]

Ghost in the Shellcode: TI-1337 (Pwnable 100)

Hey everybody, This past weekend was Shmoocon, and you know what that means—Ghost in the Shellcode! Most years I go to Shmoocon, but this year I couldn't attend, so I did the next best thing: competed in Ghost in the Shellcode! This year, our rag-tag band of misfits—that is, the team who purposely decided not […]

ropasaurusrex: a primer on return-oriented programming

One of the worst feelings when playing a capture-the-flag challenge is the hindsight problem. You spend a few hours on a level—nothing like the amount of time I spent on cnot, not by a fraction—and realize that it was actually pretty easy. But also a brainfuck. That's what ROP's all about, after all! Anyway, even […]

Epic “cnot” Writeup (highest value level from PlaidCTF)

When I was at Shmoocon, I saw a talk about how to write an effective capture-the-flag contest. One of their suggestions was to have a tar-pit challenge that would waste all the time of the best player, by giving him a complicated challenge he won't be able to resist. In my opinion, in PlaidCTF, I […]

A padding oracle example

Early last week, I posted a blog about padding oracle attacks. I explained them in detail, as simply as I could (without making diagrams, I suck at diagrams). I asked on Reddit about how I could make it easier to understand, and JoseJimeniz suggested working through an example. I thought that was a neat idea, […]