Hashbang.ca

This Thursday, I gave a talk at AtlSecCon 2014. The weather threw a wrench in the organizers' plans, but they managed to pull off a solid conference. Unfortunately, the talks weren’t recorded this year. The slides are posted on SpeakerDeck, and are embedded below the fold.

I also reprised this talk at NSLUG, and recorded audio, now posted on SoundCloud, and also embedded below the fold.

Finally: late last year, I wrote 3 posts exploring Canada’s computer crime laws (1, 2, 3) which were initial versions of work that eventually became two papers I submitted this semester for a directed studies course. If you were interested in those posts, I’ve embedded the final PDFs below. The talk is a condensed version of that work.

Heartbleed is a critical vulnerability in OpenSSL revealed yesterday. I’m not sure it could be more serious: it allows an attacker to connect to your server and use the TLS heartbeat extension to obtain 64k of server memory (and do it again to get another 64k and again and…) – while leaving no traces in logs. That server memory might include primary key material (private keys), secondary key material (usernames and passwords), and collateral (memory addresses, canaries used to detect overflow, etc)

Since the exceptions in copyright law for encryption and security research don’t apply if you’re doing anything criminal, I next looked at the Criminal Code [PDF].

Since the exceptions in copyright law for encryption and security research don’t apply if you’re doing anything criminal, I next looked at the Criminal Code [PDF].

As someone with an interest in technology, security, and the legal issues surrounding them, I often watch relevant legal cases with interest. Typically, those cases come from the United States. The CFAA has been in the news frequently of late, and not always in a good light. I was pleased to see Zoe Lofgren’s proposed changes, which try to make the law less draconian.

This is typical for Canada – we often see more about American news on topics like this than Canadian. I realized that I really didn’t know what the law in Canada said about so-called computer crimes, although I’ve often wondered. A while back, I took an afternoon to do some reading. I was not happy when that afternoon ended. This is part one of a three-part series on what I found.

IRC bouncers are sort of like a proxy. Your bouncer stays online, connected to IRC, all the time, and then you connect to the bouncer using a normal IRC client. I connect to my bouncer with an SSL-encrypted connection, but I hadn’t been validating the certificate until now. Validating the SSL certificate is critical for thwarting man-in-the-middle (MITM) attacks.

In a MITM attack, the victim connects to the attacker, thinking it is the service they want to talk to (the IRC bouncer in this case). The attacker then forwards the connection to the service. Both connections might use SSL, but in the middle, the attacker can see the plaintext. They can simply eavesdrop, or modify the data flowing in both directions. SSL is supposed to prevent that, but if you don’t validate the certificate, then you don’t know who you’re talking to. I want to know I’m really talking to my IRC bouncer, so let’s figure out how to validate that certificate.

Last Monday, I presented my solutions to the Natas server-side security war games at NSLUG. Afterwards, I spent some time to clean up my code, and I’ve now published it to CPAN as Hack::Natas, which comes with modules and scripts to solve level 15 and 16 in an automated way, plus walkthroughs for all the levels up to 17 written in Markdown (those are almost the same as my blog posts, so you’re not missing out by looking at only one or the other).

Last Monday, I presented my solutions to the Natas server-side security war games at my local linux users' group.

I recorded my talk, but it didn’t turn out well. I was using Google Hangouts for the first time, and I forgot that it only records the windows you tell it to. In the video, embedded below the fold, there’s a lot of talking about windows that were being projected, but which didn’t get recorded. Still, the audio counts for something, and you can see what I’m talking about much of the time.

This SSL configuration for nginx achieves an A on the SSL labs tool. It’s what this server currently uses.

This is the last level. We’re challenged with an improved version of level 9 – they’ve added additional “sanitation” to keep us out.

    if(preg_match('/[;|&`\'"]/',$key)) {
        print "Input contains an illegal character!";
    } else {
        passthru("grep -i \"$key\" dictionary.txt");
    }

We’re nearly at the end! This is the 2nd-last level.

We know there is a users table, with columns “username” and “password”. This time, the code just checks that the username exists. There’s no way to print out the data we want. Instead, we’ll have to do something cleverer.

In level 14, we see a more traditional username & password form. Let’s check the source code to see if there are holes we can slip through.

This is level 13. Looks like they claim to only accept image files, in order to close the flaw we used previously. I bet we can get around that restriction just like we did when they disallowed certain characters in the search term. Let’s examine the code.

Here’s the new part of the code:

    if (! exif_imagetype($_FILES['uploadedfile']['tmp_name'])) {
        echo "File is not an image";
    }

In level 12, we’re given a file upload form. Let’s take a look at the code that processes input.

This is level 11. Your clue is that “XOR encryption” is not encryption. Let’s look in the cookies to find out they have XOR-ed, so we can mess with it.

Welcome to level 10. “For security reasons, we now filter on certain characters” – okay they’ve gotten wise to our little game. But let’s check how good their countermeasures are.

Well, they don’t allow us to use the semicolon or ampersand any longer. Well that’s not a problem, I know other ways to manhandle that command into doing what I want.

In level 9, the “Input secret” form is replaced by one that looks like it is searching for words containing the string you provide. Give it a try, and then look at the code.

Well, this is just grepping through a wordlist, using the POSTed needle as a parameter. Since we control the value of that POSTed variable, we can control the command that gets executed. Now we need to figure out how to use that to our advantage.

Level 8 shows us another “Input secret” form. Let’s examine the source again. This time, there is an “encoded” secret. Let’s try to reverse engineer this. They’re using bin2hex, strrev, and base64_encode – those are all trivially reversible.

Level 7 is a simple webpage that doesn’t seem to offer us any clues about a vulnerability. Let’s click around those links a bit to see more.

Well, each of these links passes the name of the page to a PHP script, which seems to just stuff the contents of the file into the webpage. So, we should be able to change that URL parameter to whatever we want, in order to get the contents of the file containing the next password.