Exploiting the Math.expm1 typing bug in V8

Minus zero behaves like zero, right?

I love browser exploitation. Must be something about breaking what I consider to be one of the most complex pieces of software we run every day. At 35C3 CTF this year (I played with KJC + mhackeroni, we got first place!) there was a Chrome challenge about exploiting a bug in V8, Chrome’s JavaScript engine. The bug caused incorrect typing during static analysis, producing incorrect optimizations in just-in-time compiled code. It was really hard to trigger: I didn’t finish in time for the CTF, but I feel like many people would be interested in a full writeup. Shouts out to @_tsuro for finding the bug in the first place and for the amazing challenge, and to ESPR for the incredible CTF!

X-MAS CTF 2018 - A white rabbit in a snowstorm

Make your S-boxes not linear, kids.

This week, we spritzers played X-MAS CTF 2018. We enjoyed this week-long event, and took the chance to mix things up a bit (e.g., web guys playing pwn). While I’m mainly a pwner, recently I’ve been getting into crypto. I found “A white rabbit in a snowstorm” to be an interesting challenge. It’s probably trivial for the more experienced crypto guys out there, but I had never broken a (very) weakened DES, so I learnt a few things.

Pwn2Win 2018 - TPM 2.0

Writeup for challenge “TPM 2.0” of Pwn2Win CTF 2018.

At last year’s Pwn2Win, we (spritzers) were the only team to solve the SGX challenge. We played again this year, getting 6th place. There was another trusted computing challenge (pwn), on TPM 2.0 this time: we kept up the tradition and were the only team to solve it. So here’s a writeup, enjoy :)

Kaspersky Industrial CTF 2018 - modcontroller

Writeup for challenge “modcontroller” of Kaspersky Industrial CTF 2018.

This weekend I played Kaspersky Industrial CTF 2018 with spritzers, where we got 7th place. Not bad considering most of us couldn’t play (and I slept way too much :P). I liked “modcontroller”, a pwn challenge worth 994 points in the end. It actually was more of a web challenge than a pwn one, and I enjoyed doing something different than usual.

HITCON CTF 2018 - Secret Note

Writeup for challenge “Secret Note” of HITCON CTF 2018.

Last weekend, I played HITCON CTF 2018 for a bit with our spritzers team. I did not have much free time, so I ended up focusing on a single hard challenge: Secret Note (342 points, pwn/crypto). I have been doing pwn for a while, but recently I have also become interested in crypto, so it looked like fun, and indeed it was!


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