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Stripe-CTF 3 Writeup

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Re: Stripe-CTF 3 Writeup

#11

Post by recentdarkness »

mkaufmann wrote: post #9
recentdarkness wrote: post #7

Earlier quoted context omitted.

well to level3 I can tell you, I just used grep embedded in a nodejs server application :D Everything boiled down to this: "cd " + data_path + "; grep -rno " + key + " | cut -d: -f1,2 | sort | uniq" I read the result from stdout and transformed the result into json that was enough to make it. I did not want at that time to spend more time on that level ;)

Damn ok, so I also missed that opportunity. Great find!

I forgot to add: I cached every result for every key which was searched for, because there was quite often that it asked 3-5 times for the same term in a row. So I had an instant result in a simple javascript object :D

Re: Stripe-CTF 3 Writeup

#12

Post by recentdarkness »

ajdecon wrote: post #10

I got stuck on level3 over the weekend and then had to put it down due to life stuff. But it was still a ton of fun, and I learned a lot. If anyone from Stripe is here, do you plan to post the original problem statements and repos for the problems anywhere public now that it's done? I'd love to get a look at level 4... :)

https://github.com/ctfs/write-ups/tree/master/stripe-ctf3/le...

Re: Stripe-CTF 3 Writeup

#13

Post by ajdecon »

recentdarkness wrote: post #12
ajdecon wrote: post #10

I got stuck on level3 over the weekend and then had to put it down due to life stuff. But it was still a ton of fun, and I learned a lot. If anyone from Stripe is here, do you plan to post the original problem statements and repos for the problems anywhere public now that it's done? I'd love to get a look at level 4... :)

https://github.com/ctfs/write-ups/tree/master/stripe-ctf3/le...

Ha, I missed that this existed. Thank you!

Re: Stripe-CTF 3 Writeup

#15

Post by fragmede »

mkaufmann wrote: post #5

Great article, I am really eager to see the solutions in github. I guess there won't be many with c++ solutions. I only found the challenge two days before the end. My goal with the challenge was not to get the best solution, but rather use it as an exercise to practice the different languages and finding intuitive solutions. Level 0 as you wrote was really just a two line change. Level 1 was fun, because I tried to…

Mind posting your code for level3? I got that partitioning was the main trick but I am too unfamiliar with scala to reassemble the responses properly.

Re: Stripe-CTF 3 Writeup

#16

Post by ithkuil »

jeremymcanally wrote: post #2

I got stuck on Level 3, partially because Scala is a little wacky (but I learned to appreciate it!) and partially because their specs were super terrible. They didn't mention it required substring matching or was case-sensitive until I'd been working on it for 2-3 days and then was out of time. Given the bad debug output (the head of a diff which often didn't show anything and didn't include what term the failure was…

I just rewrote it in Go, you can easily do the same with your preferred language. the readme is actually well written, and you can easily check the actual input you get by just sniffing.

give it a try

Re: Stripe-CTF 3 Writeup

#17

Post by ithkuil »

jeremymcanally wrote: post #2

I got stuck on Level 3, partially because Scala is a little wacky (but I learned to appreciate it!) and partially because their specs were super terrible. They didn't mention it required substring matching or was case-sensitive until I'd been working on it for 2-3 days and then was out of time. Given the bad debug output (the head of a diff which often didn't show anything and didn't include what term the failure was…

I just rewrote it in Go, you can easily do the same with your preferred language. the readme is actually well written, and you can easily check the actual input you get by just sniffing.

give it a try

Re: Stripe-CTF 3 Writeup

#18

Post by adwf »

One recommendation I'd make, is to reveal all problems at the very beginning.

I logged in, saw that the first problem was nothing to do with distributed computing. Also realised it would take me longer to submit the code than it had taken to work out the answer... then I quit and didn't look back.

It's a shame, because levels 2 & 4 possibly look quite interesting, I might have persevered if I'd known. Sadly, limited time on my hands means I dismissed it too quickly!

Re: Stripe-CTF 3 Writeup

#19

Post by gatehouse »

I bailed out on level 3 after about 10 total hours into the contest, as I see was pretty common.

I really enjoyed level1. I ended up doing an ugly little modification to git itself to mess around with the last few bits of the commit until I got the desired number of prefixed zeros on the sha1: http://pastebin.com/RwTjjtTU

Re: Stripe-CTF 3 Writeup

#20

Post by gdb »

ajdecon wrote: post #10

I got stuck on level3 over the weekend and then had to put it down due to life stuff. But it was still a ton of fun, and I learned a lot. If anyone from Stripe is here, do you plan to post the original problem statements and repos for the problems anywhere public now that it's done? I'd love to get a look at level 4... :)

I have a post on the CTF infrastructure that I'm working on; should be out in the next few days hopefully.

Looks like the original level sources have been published, though perhaps we'll do something official as well.

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