On another free weekend afternoon, I decided to finish off the rest of the coreutils brainteasers I started last month. This time I learned more about Linux audio, bash substring replacement, and the assortment of flags that ls supports.

Reading through an article, What every computer science major should know, I came across a couple of interesting coreutils brain teasers under “The Unix philosophy” to play with of an evening. They turned out to be a great way to learn about some more tools, and to brush up on some of those I already knew.

A couple of months ago I wrote a web challenge for the 9447 CTF called ramble. Spoiler alert, the challenge was written in nodejs, but allowed the user to execute arbitrary shell code. Clearly I didn’t want players to be able to destroy the challenge for others, so I wanted my process to have ~no privileges. This proved to be more of a challenge than expected.

I’ve had brief encounters with gpg in the past, but never enough to warrant grokking the different types of things you can do with it. However, Stripe uses gpg enough internally that I figured it was time to actually learn how this thing worked.

I was surprised to learn this week that I wasn’t the only person in the world who was scared by OAuth. Given its popularity (Login with Facebook! Login with Google!) it seemed like it must be fairly well understood, but asking around I could find few people who said they felt comfortable with it, and no one able to describe it to me succinctly, especially without using the terms “resource owner” or “client”.