Category: Security

More ActiveAdmin Customizations with CanCan

Post author By Yoav Aner
Post date 10 August, 2012

Coming from Django, I was a little surprised/disappointed that permissions aren’t very tightly integrated with the Rails ActiveAdmin as they are with the django admin. Luckily, my search for better authorization for ActiveAdmin has led me to this very informative post by Chad Boyd. It makes things much easier so we can authorize resources more flexibly.

However, there were a couple of aspects that I still wasn’t 100% happy with:

When an unauthorized action is attempted, the user is simply redirected with an error message. I personally like to return a 403 response / page. Yes, I’m nitpicking. I know.
Default actions like Edit, View and Delete still appear. They are not dependent on the permission the user has. Clicking on those won’t actually allow you to do anything, but why have some option on the screen if they are not actually allowed??

So with my rather poor Ruby/Rails skill, and together with my much more experienced colleague, we’ve made a few tweaks to the proposal on Chad’s post to make it happen.

rails ruby Security Technology

Simple Detection of Comment Spam in Rails

Post author By Yoav Aner
Post date 4 August, 2012

It’s always nice to be able to get some feedback, or for users to make a contact via a simple Contact form. However, it didn’t take too long before spammers started hitting those forms too. It was quite interesting to see the kind of messages we started receiving. In a way, most of those submissions were more like stories, or snippets from an email to a friend. They didn’t have any of those very much expected keywords for fake watches or erectile dysfunction enhancers. Many didn’t even have any links either. So what were these messages then? My personal guess was that these were some kind of a reconnaissance attempts. The bots were sending innocent messages first to various online forms. Then I imagine they will crawl the site more, trying to see if those submissions appear elsewhere. If/when they do, they will hit those forms hard with the real spam content. In any case, these were all speculations that I didn’t really care to prove right or wrong. I just wanted to get rid of this junk. Fast.

Security

A different kind of spider

Post author By Yoav Aner
Post date 11 February, 2012

It’s always nice to discover a new tool or service that does things differently. Even if just a little. I remember when someone first told me about hipmunk. Just when I thought all flight search websites are pretty much the same, here’s one example of something different.

Arachni

Perhaps this wasn’t as obviously different as hipmunk is, but one of the tools I came across recently within the security testing world is Arachni. A number of things made it stand out a little. First of all, it is written in Ruby. That already sparked some curiosity. I’m not entirely sure why, but I guess I’m naturally more interested in programs and tools in Ruby and Python. The next thing that was evidently different from other web scanners was the fact that Arachni seems to be very pluggable and interface-able. Arachni appears to be geared towards interfacing with external scripts or programs though an API. One of its core features is its distributed architecture, allowing to launch many modules independently and control them programmatically.

After playing around with it, I came across some issues and couldn’t make it work as I expected. Most of them out of my own lack of knowledge or being lazy reading through the extensive documentation. Luckily, it didn’t take more than a few minutes after posting a question on github, that I received a response from Arachni’s creator, Tasos Laskos, aka Zapotek.
After chatting with Tasos a few times via email, I became even more intrigued about him and the project. I then decided it would be interesting to interview him for my blog. I have no experience interviewing people, but what the heck.

Tasos accepted my invitation for an interview, with the condition that it must be a text-based interview. So this interview was carried out via email alone. I personally suspect his voice is funny, but he (obviously) denied it :)
Tasos is certainly not an ordinary person. It becomes apparent when you read his blog, or even the documentation for Arachni. As you could see from the interview, Tasos appears to have very strong and clear opinions. He doesn’t mince his words, and very directly expresses what he thinks. Nevertheless, Tasos and Arachni seem to be doing something a little different, and there’s definitely more to wait for.

linux Security

updating lighttpd on debian squeeze against the BEAST

Post author By Yoav Aner
Post date 11 February, 2012

If you’re updating your debian stable (squeeze) and using Lighttpd as your web server, you might come across a security notice on how to fix your lighttpd against the BEAST attack.

lighttpd (1.4.28-2+squeeze1) stable-security; urgency=high

 This releases includes an option to force Lighttpd to honor the cipher order
 in ssl.cipher-list. This mitigates the effects of a SSL CBC attack commonly
 referred to as "BEAST attack". See [1] and CVE-2011-3389 for more details.

 To minimze the risk of this attack it is recommended either to disable all CBC
 ciphers (beware: this will break older clients), or pursue clients to use safe
 ciphers where possible at least. To do so, set

 ssl.ciphers =  "ECDHE-RSA-AES256-SHA384:AES256-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH:!AESGCM"
 ssl.honor-cipher-order = "enable"

 in your /etc/lighttpd/conf-available/10-ssl.conf file or on any SSL enabled
 host you configured. If you did not change this file previously, this upgrade
 will update it automatically.

 [1] http://blog.ivanristic.com/2011/10/mitigating-the-beast-attack-on-tls.html

There’s a mistake on this note however. Instead of

django optimization python Security

Keep your hands off my tastypie

Post author By Yoav Aner
Post date 26 January, 2012

Update

Please note that since Tastypie v0.9.12 the authorization framework was rewritten. Lots of information on this post no longer applies. I’m hoping to write a follow-up post at some stage.

Original Post

I’ve been using tastypie, the very awesome django REST API framework for a little while now (btw, that’s not the official title, but it might as well be). I’m not going to write yet another comparison between tastypie and django-piston. My reasons for choosing tastypie were that its code looked nicer, and it seemed a much more active project.

One of the things that I immediately liked about tastypie, being a security-geek and all, was the security framework built into it. Primarily the authentication and authorization classes. They make it very easy to extend, and almost a no-brainer to apply to any resource. This means that providing resource-level authorization is also very easy and clean.

However, whilst working with tastypie and applying some authorization rules to my resources, I noticed a couple of pitfalls. Those are quite easy to miss if you’re not very familiar with the tastypie codebase. I wouldn’t say it’s a vulnerability or a bug as such, perhaps more of a (sub-optimal) design choice from a security-perspective. That said, if you use tastypie incorrectly, or unaware of those pitfalls, you might create a security vulnerability on your otherwise delicious API.

Security Technology

encryption is not the right solution

Post author By Yoav Aner
Post date 4 January, 2012

When talking about security, the first thing that usually comes to mind is encryption. Spies secretly coding (or de-coding) some secret message that should not be revealed to the enemy. Encryption is this mysterious thing that turns all text into a part of the matrix. Developers generally like encryption. It’s kinda cool. You pass stuff into a function, get some completely scrambled output. Nobody can tell what’s in there. You pass it back through another function – the text is clear again. Magic.

Encryption is cool. It is fundamental to doing lots of things on the Internet. How could you pay with your credit card on Amazon without encryption? How can you check your bank balance? How can MI5 pass their secret messages without Al-Qaida intercepting it?

But encryption is actually not as useful as people think. It is often used in the wrong place. It can easily give a false sense of security. Why? People forget that encryption, by itself, is usually not sufficient. You cannot read the encrypted data. But nothing stops you from changing it. In many cases, it is very easy to change encrypted data, without knowledge of the encryption key.

Security Technology wordpress

timthumb vulnerability

Post author By Yoav Aner
Post date 5 August, 2011

About a month ago I posted about tweaking timthumb to work with CDN. Timthumb is a great script, but great scripts also have bugs. A recently discovered one is a rather serious bug. It can allow attackers to inject arbitrary php code onto your site, and from there onwards, pretty much take control over it.

Luckily no websites I know or maintain were affected, possibly since the htaccess change I used shouldn’t allow using remote URLs in the first place (and also it renamed timthumb.php from the url string, making it slightly obfuscated). I still very strongly advise anybody using timthumb to upgrade to the latest version to avoid risks.

Security Technology wordpress

ajaxizing

Post author By Yoav Aner
Post date 26 June, 2011

Following from my previous post, I’ve come across another issue related to caching in wordpress: dynamic content. There’s a constant trade-off between caching and dynamic content. If you want your content to be truly dynamic, you can’t cache it properly. If you cache the whole page, it won’t show the latest update. W3 Total Cache, WP Super Cache and others have some workarounds for this. For example, W3TC has something called fragment caching. So if you have a widget that displays dynamic content, you can use fragment caching to prevent caching. However, from what I worked out, all it does is essentially prevent the page with the fragment from being fully cached, which defeats the purpose of caching (especially if this widget is on the sidebar of all pages).

The best solution for these cases is using ajax, to asynchronously pull dynamic content from the server using Javascript. So whilst many plugins already support ajax, and can load data dynamically for you, many others don’t. So what can you do if you have a plugin that you use, and you want to ‘ajaxize’ it?? Well, there are a few solutions out there. For example this post shows you how to do it, and works quite well.

The thing is, I wanted to take it a step further. If I can do it by following this manual process, why can’t I use a plugin that, erm, ‘ajaxizes’ other plugins?? I tried to search for solutions, but found none. So I decided to write one myself. It’s my first ‘proper’ plugin, but I think it works pretty well.

linux Security Technology

timing is everything

Post author By Yoav Aner
Post date 8 May, 2011

A quick-tip on the importance of timestamps and making sure your time zone is set correctly.

I was recently playing around with fail2ban. It’s a really cool little tool that monitors your log files, matches certain patterns, and can act on it. Fail2ban would typically monitor your authentication log file, and if for example it spots 5 or more consecutive failures, it would simply add a filter to your iptables to block this IP address for a certain amount of time. I like fail2ban because it’s simple and effective. It does not try to be too sophisticated, or have too many features. It does one thing, and does it very well.

I was trying to build a custom-rule to watch a specific application log-file. I had a reasonably simple regular expression and I was able to test it successfully using fail2ban-regex. It matched the lines in the log file, and gave me a successful result

Success, the total number of match is 6

However, when running fail2ban, even though it loaded the configuration file correctly, and detected changes in the log files, fail2ban, erm, failed to ban… I couldn’t work out what was the problem.

As it turns-out, the timestamps on my log file was set to a different time-zone, so fail2ban treated those log entries as too old and did not take action. Make sure your timestamps are correct and on the same timezone as your system!! Once the timezone was set, fail2ban was working just fine.

Security Technology

passwordless password manager

Post author By Yoav Aner
Post date 3 March, 2011

[Also published on testuff.com]

Most people I know tend to simply use the same password on ALL websites. Email, Paypal, Amazon, Ebay, Facebook, Twitter. This is obviously a very bad idea.

Passwords are always a problem. Difficult to remember, hard to think of a good one when you need a new one, tricky to keep safe. For the moderately-paranoid and the sufficiently-techie there are many good solutions out there. Password managers. Online, offline, commercial, free. So I usually suggest to my friends and colleagues to use a password manager.