david wong

Hey! I'm David, a security consultant at Cryptography Services, the crypto team of NCC Group . This is my blog about cryptography and security and other related topics that I find interesting.

Exams

posted April 2014

We've been a group of 4-5 students spending each nights at the Crémi these few last days, this building of three floors where each floor has around 10 rooms full of computers.

We work, we eat, we play, and we crash each other computers.

There are a bunch of games installed on every computers but we mostly play SauerBraten, a quake-like.

sauerbraten

My 15-year-old self would have spent most of his days here playing, if only he knew that his future campus would have such a sacred place :)

How do we crash each other computer? We just ssh into their machine and launch a fork bomb:

 :(){ :|:& };:

It operates by defining a function called ':', which calls itself twice, once in the foreground and once in the background.

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The Heartbleed Challenge

posted April 2014

Cloudflare's engineers have set up a server vulnerable to Heartbleed, if you find the secret SSL keys and publish your solution you'll get 10,000$. The challenge is here and there's a blog post here.

an attacker can get up to 64kB of the server’s working memory. This is the result of a classic implementation bug known as a Buffer over-read

Apparently it is not known if it is possible or not to find those keys. If it appears to be possible the results would be catastrophic as every single website that has used OpenSSL would have to revoke and ask for a new certificate. And as Cloudflare says:

the certificate revocation process is far from perfect and was never built for revocation at mass scale.

So it would then be very easy for any server to pretend they're someone else.

A heartbeat is a message that is sent to the server just so the server can send it back. This lets a client know that the server is still connected and listening. The heartbleed bug was a mistake in the implementation of the response to a heartbeat message.

This is the code in question:


p = &s->s3->rrec.data[0]

[...]

hbtype = *p++;
n2s(p, payload); 
pl = p;

[...]

buffer = OPENSSL_malloc(1 + 2 + payload + padding);
bp = buffer;

[...]

memcpy(bp, pl, payload);
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How we got read access on Google’s production servers

posted April 2014

The team at Detectify found a way to access files on one of google's production server. Thanks to an old google product (google toolbar) that was using a poorly secured XML parser.

They just used a simple XXE attack where they uploaded a poisoned xml files and saw what the application printed back

a xxe looks like this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [  
<!ELEMENT foo ANY >
<!ENTITY xxe SYSTEM "file:///etc/passwd" >]><foo>&xxe;</foo>

More on their blog

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How Heartbleed works thanks to XKCD

posted April 2014

I found a pretty nice explanation of Heartbleed for the layman in this XKCD comic. Heartbleed is a recent and alarming vulnerability found in the OpenSSL toolkit that serves most of the application/websites today. To quote Schneier:

"Catastrophic" is the right word. On the scale of 1 to 10, this is an 11.

Here's the comic:

heartbleed

And if you want to dig a bit more into it, you can read some more explanations on security.stackexchange.

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Condoleezza Rice join the Board of Directors at Dropbox

posted April 2014

..We're proud to welcome Dr. Condoleezza Rice to our Board of Directors. When looking to grow our board, we sought out a leader who could help us expand our global footprint. Dr. Rice has had an illustrious career as Provost of Stanford University, board member of companies like Hewlett Packard and Charles Schwab, and former United States Secretary of State. We’re honored to be adding someone as brilliant and accomplished as Dr. Rice to our team.

People are not happy with that news.

When I knew you at Stanford I had the greatest admiration for your abilities and good sense. But now I cannot help but express to you my chagrin that the warm feelings I once had have basically evaporated. I hope you can pause to try to understand why this might be the case.

Don Knuth's open letter to Condoleezza Rice

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Heartbleed already being used to cash bitcoins

posted April 2014

A message some users of Virwox received:

Hello,
here is what has happened:
Similar to other exchanges, our servers are protected from DDOS-attacks by an external service provider. While our own servers themselves were not vulnerable to the "Heartbleed" attack, the proxy servers of the DDOS provider were. They have fixed the problem already and we have turned on the service again.
The good news is that our own server was NOT hacked, and none of our secrets or bitcoins were stolen. However, the attacker was able to get to the session cookies of in total 20 users who were logged in yesterday (between about 8am and 11am), and used this to try to withdraw the money they had in their account in the form of bitcoins.

They don't say how much loss they have suffered, but they have reimbursed the victims.

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My blog

posted April 2014

p1x3l

p1x3l

I wanted to learn Python, so a few months ago (I forgot to post about it here!) I redid my old blog in Django.

It's way different than PHP but it was a lot of fun :) I love learning different technologies. You can check it out here but be careful, it's in french!

Here's a list of what I want to learn right now:

  • QT with C++
  • Unity
  • Android applications
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Brackets

posted April 2014

I recently advised a colleague to try Brackets since he's learning html, css, etc...

But I've never really used it myself for a project. I've tried it, found it really cool, but never had a chance to start a project with it yet. As I was trying to convince my colleague to give it a try I ran into this cool video from Jeffrey Way the guy who made Tutsplus (and the amazing sublime text tutorial) Check it out!

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Fast Fourier Transform

posted April 2014

So, I've learned about Fourier every year in my bachelor of Mathematics and I'm learning about the efficient algorithm dealing with the Fourier Transform in my class of Algebra right now.

I found a really nice video explaining really quick what it is, concretely.

Here's wikipedia way of showing that fourier made by LucasVB, this crazy guy doing all those math gifs you've probably seen before :) more here

There's also a visualization in d3.js here: http://bl.ocks.org/jinroh/7524988

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Long polling and webhooks

posted April 2014

I remember reading about how the newly facebook chat was made using long pollings, years ago. Now with HTML5 with have sockets and webhooks made easy. I wonder if they're still using long polling now...

Anyway, Zapier. A start up that is making APIs easy, is writing a lot of interesting tutorials these last few months. Their new Chapter 7 was released and it's about polling and web hooks. And as usual it's great!

https://zapier.com/learn/apis/chapter-7-real-time-communication

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OpenSSL is written by monkeys

posted April 2014

After messing around with this code for about a month I decided to write this up for the tubes in the hope that I can save some souls. I have come to the conclusion that OpenSSL is equivalent to monkeys throwing feces at the wall. It is, bar none, the worst library I have ever worked with. I can not believe that the internet is running on such a ridiculous complex and gratuitously stupid piece of code. Since circa 1998 the whole world has been trusting their secure communications to this impenetrable morass that calls itself the "OpenSSL" project. I bet that the doctors that work on that shitshow can not prescribe anything useful either!

worrying essay, read it here: https://www.peereboom.us/assl/assl/html/openssl.html

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Heartbleed : serious vulnerability in open SSL

posted April 2014

We have tested some of our own services from attacker’s perspective. We attacked ourselves from outside, without leaving a trace. Without using any privileged information or credentials we were able steal from ourselves the secret keys used for our X.509 certificates, user names and passwords, instant messages, emails and business critical documents and communication.

A pretty bad bug has been found in open SSL during the Codenomicon. more info here: http://heartbleed.com/

List of vulnerable websites from the Alexa top 10,000 websites: https://gist.github.com/dberkholz/10169691

You can test a website here: http://filippo.io/Heartbleed/

And also, if you have a lot of time to waste, this random dude seems to know a lot about it :D

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