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'; CREATE TABLE `Capture the Flag`;' -- Stripe's Web Security CTF is Live (stripe.com)
254 points by CD1212 on Aug 22, 2012 | hide | past | web | favorite | 75 comments

Shameless: Enjoying this challenge? You'd enjoy working with us. We're hiring in Chicago, in Mountain View, and in Manhattan. This stuff is our day-to-day, plus reversing, custom protocols, tool development, and exotic applications. If you've never done appsec work professionally, but find these challenges fun and straightforward, we'd love to talk to you:

We've hired more people off HN than from any other vector.


(Or, you know, ask Stripe for a job. I'm sure they're hiring too!)

Matasano also likes interns! I worked with them for the past two summers and can't say enough good about the experience. You will learn (or get to practice) the things tptacek mentioned above as well as web apps, mobile, ruby, a staggering amount of crypto, and whatever else you find interesting to work on or ask about. If you're into this stuff, check them out!

Shameless, following tptacek and borski's examples: Having fun finding broken code? Want to get paid without going to the effort of writing exploits? You might want to look at the Tarsnap (or scrypt, or kivaloo, or spiped) code and see if you can win some bug bounties: http://www.tarsnap.com/bugbounty.html

(Or, you know, ask Stripe or Matasano or Tinfoil Security for a job. They'll pay you far more than you'd ever get from Tarsnap's bug bounties.)

Disclaimer: Also shameless

A lot of people have fun with this kind of challenge, as well as network security in general. Over 10,000 people went to DEFCON this year (I've seen estimates between 13,000 and 16,000). Hacker IRC rooms are constantly buzzing. Security is fun, and while building software is immensely satisfying, so is breaking it.

So why is the information security industry so tiny?

For one, it's competitive, but I think that many, many qualified security guys don't realize that there's a thriving industry around this kind of stuff.

If you want to work in security, these CTF-style challenges are a great way to show that you're self-motivated and clever. I'm always hiring application security engineers, and honestly it's pretty difficult to find people who are new to the field. People seem to either have a decade of experience and bounce from company to company, or no experience at all and assume that they "aren't good enough."

If a company can't take some raw talent and refine it, they don't deserve raw talent in the first place. We call that training.

If you like this kind of stuff, apply at Stripe, or Matasano, or Tinfoil Security -- or even my engineering team at Redspin. If you mention "HN" or "Hacker News" in an email to jobs at redspin.com, I'll know exactly where you came from :)

PS: Redspin hires all kinds of security engineers, from policy & procedure specialists to network infrastructure guys to appsec experts. It's better to apply and have a conversation than to be too afraid to try!

Shameless, ala tptacek: Enjoying this challenge? We do similar things on a daily basis over at Tinfoil Security. We develop tools to attack websites in a lot of similar ways to this Stripe CTF. We're hiring in Palo Alto, and even if you've never done appsec work before, we'd love to chat.


(Or, you know, ask Stripe or Matasano for a job. They're both crazy awesome, have a ton of respect from me, and are also hiring.)

Huge kudos for the design of the site - it definitely gives off a Tron-like feel. I can't imagine the attention to detail to what amounts to just a game.

> I can't imagine the attention to detail to what amounts to just a game.

Game, marketing exercise, recruitment tool.

It serves an important purpose for them no doubt, but it is surprisingly polished and addictive. Just shows you that it's worth putting time into perfecting even activities which might seem peripheral - I'll bet they'll find some good people via this game (the ones who finished it really quickly and with clever solutions).

I'm totally stuck on Level 7 after getting some waffles and have no time to continue though, oh well.

You nailed it on the addictive bit. I got home from work around 6pm and started the game. I glanced at the clock after a bit and realized it was almost 2am. Oops!

There is always after it's finished to continue. They are releasing it after the game is over.

My favorite part is watching the captures in real time at https://stripe-ctf.com/leaderboard.

As I (and my now partner Eevee) race towards the level 8 finish line, I don't feel quite the same. I see us making limited progress and see the number of people finishing level 7 rising, haha. This is fun, though.

Good luck guys.

I just made it to level 8 this morning and haven't a clue where to really begin with it.

It's definitely a lot of fun and has been an interesting journey for sure. Love little games like this.

I've worked in/with security along these lines for a very long time. This CTF (particularly level 8) has been some of the most difficult stuff I've ever done. Thanks to Stripe for putting this together; if I wasn't already a customer, I absolutely would be now!

More difficult than hotel locks? :)

Yes. A million times, yes. While the lock stuff took a while and was rather involved, it was simple. This... not so much.

Ended up finally finishing level 8. Was a huge pain but definitely feel so much better for completing it -- what a rush.

Yeah it was pretty tricky but once you get down the approach it's not too bad. Took me awhile to realize what was going on.

Looks like someone has found the egg.

Easter-egg? There's menu link on every the main page.

That was in English when I thought it :-)

is that a "Ready Player One" reference?

I was looking forward to verifying the P = NP proof on level 3, but sadly I don't have access to DARPA’s 1000-node testbed, nor does my phone have any optical storage space. Sigh :(

Anyway, love the challenge, the attention to detail is awesome :)

Definitely wish time wasn't a factor - on Level 3, but just don't have the time to commit to it :/ Maybe later tonight

Ditto. I would totally spend a few hours on this if I didn't have work to do :/

Maybe after you complete a level you could get the choice of "Pause the game" or "give me the next challenge" ?

Don't worry -- even if you don't get to play this week, we'll be releasing the levels afterwards so you can run them yourself at home.

It seems like no matter what screen name I pick, the settings claim that it is unavailable.

Fixed! Sorry about that.

I put my screenname in, had not checked "show...". Then, I went back to check that, and now am getting the "screen name is unavailable" error.

This is what I get for editing code on the fly. Should be really fixed now.

Unit tests! ;)

Works now, thanks a bunch.

This is suprisingly fun. At first, you feel like a badass, reading the documentation for every function call, googling for exotic bugs. Then you feel like a total idiot when you notice how simple it actually is. Finally, you laugh at people in the IRC because you know exactly how stupid they feel.

The most frustrating thing was knowing exactly what the exploit was, but not quite getting how to take advantage of it.

Yeah... I can't believe I spent time looking for something wrong with the HMAC used for session cookies. Also, I'm pretty sure I solved #5 the "wrong" way since it didn't actually involve the hint they gave.

I didn't use the Level 2 server for #5 either (although I did for #8) - so I suspect that many people solved it the same way.

Yup. Kept overthinking it. Oy.

I really enjoyed this until I got stuck on level 3. I have a bunch of ideas about what the solution might be but I'm not good. Are there any websites with challenges similar to this that are more geared towards someone that isn't so great at this sort of thing? A "beginner" at security stuff?

You may want to check out the Reading Materials section on https://stripe-ctf.com/about.

Stopped at level 3, for a break, and because I couldn't see the exploit so easily. But still, amazing site design and great fun.

Would love to sit down with it for a bit longer and crack on.

I finished first three levels. I will continue with the rest tomorrow.

I think if they didn't provide code, it would have been really difficult. Is everyone feeling same way?

unrelated to the game, but on the social network question:

> $url = "https://upload.wikimedia.org/wikipedia/commons/f/f8/ . "Question_mark_alternate.svg";

can't someone edit the image on wikipedia and change the image displayed to everyone else here -- or is the wikimedia image system only accessible by admins?


I believe it is very editable once login.

Seriously love this ctf, the style and everything is quality. Hope I have some more time tomorrow to slash away at it. THANKS STRIPE!

What scares me about this is they want you to authenticate via github with an app that's going to be hacked at.

Is this not dangerous?

We just ask for your publicly readable profile information. For exactly that reason :).

Gah, I'm stuck on level 4. I've never really dealt with security in ruby / sinatra / sequel applications.

... Yeah, me too. If you check out the "about" page [1], there's IRC info at the bottom [2], so there may be hints there.

1: https://stripe-ctf.com/about

2: irc://irc.stripe.com:+6697/ctf

Edit: the IRC helped. the issue isn't ruby, sinatra, etc.

I was stumped by disbelief. Well, now I know that Stripe isn't lazy.

On level 7 now. Man this is fun.

Still on 4, was having fun until now :)

Is the "502 bad gateway / nginx" page after signup submission part of the challenge?

Sorry 'bout that: scaling issues. Should be fixed now!

In now, thanks! :)

I'm now really looking forward to work finishing for the day. The first thing I did was email all the developers at work and challenge them with a race to the finish :p ....I'm a grad halfway through my year of QA.

Have had a lot of fun with this so far even though I'm only at level 4, kind of went off on a tangent on level 3 and after getting a partial solution I realised that there was a much easier way of approaching it

I can't wait until the very last challenge just says: "SURPRISE, you typed in your password when you started this event, which is the most common way that someone's password will get stolen."

I just authenticated with Github (public info, read-only).

Don't know if I'll have time (or the skills) to finish Level 8 (it looks pretty intense), but the other levels were a lot of fun. This was done really well - thanks for doing it!

Level 7 is actually harder technically than Level 8, although Level 8 had problems at their end when there were too many people trying for it, overloading the Level 2 and Level 8 servers and making it hard to get a successful exploit. Once they fixed that, it was easy.

The public URL for the Secret Safe given to me in Level 0 doesn't actually return a response when I get request it, the connection just sits open - is this expected?

Nope -- scaling issues. Should be fixed now.

The site's down again. 502 Bad Gateway.

Level 2 is just giving me timeouts. Joined IRC channel to report bug, and somebody gave away the answer for level 2. Bummer, I had been enjoying myself.

Aww, I wish I had the time to participate this time. I had a blast with the first one! I proudly wear my stripe ctf shirt :)

Thanks for the great game, Stripe guys. There were a lot of fun challenges and I learned quite a few things in the process!

Title of this HN post is great example of how to get attention of hacker minds.

WOW, that went better than expected. tptacek can expect an e-mail ;)

Just finished level 8!

I wonder when level 4 will be back up.

love it! bummed different parts keep going down; although I'm sure servers are getting slammed :)

Woo, Finally got level 8

Level 3 timing out :(

I'm having this issue as well.

extremely awesome. just what i like


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