Feeds

Attention developers: Your SESSIONIDs are showing

You don't know sidejack

Securing Web Applications Made Simple and Scalable

Protecting passwords is important, but do you take the same care with your SESSIONIDs? You should.

Here's how they work: When you log into a web application, you exchange your credentials for a SESSIONID cookie. This cookie gets sent with every subsequent request from your browser until you log out or the session times out. During that window, if an attacker steals your SESSIONID, they have full access to your account.

What is your SESSIONID? Log into a website and type "javascript:alert(document.cookie)" into your browser. That number is very important and must be kept secret. Anyone who has it can hijack your account.

So what do you need to do to protect your application's SESSIONIDs? Here are some tips.

Don't roll your own

First, you want to make sure your SESSIONIDs are not guessable. Just like a password, they should be long and random so that attackers can't use a brute force attack. Some web applications and web services still create their own SESSIONID token, and a few even use a sequential integer. You should stick to the standard SESSIONID provided by your container.

Believe in SSL

Some web applications use SSL for the username and password, but then fall back to a non-SSL connection after authentication. Unfortunately, this means that the SESSIONID is transmitted in the clear in every HTTP request, where it can be easily read by anyone with access to the network. This attack is called "sidejacking," and there are simple tools available to exploit this weakness.

Don't forget your AJAX requests, as they may also contain a SESSIONID. Gmail has this problem, as the application sometimes falls back to non-SSL for AJAX requests, exposing the user's Gmail SESSIONID on the wire. Google recently added a setting to "always use SSL" that you should enable right now. Despite performance issues, the only solution to protect your SESSIONIDs on the wire is to use SSL for every single page from your login form to your logout confirmation.

Fly the cookie flags

Even if your application always uses SSL, attackers may try to trick the browser into exposing the SESSIONID over a non-SSL connection by getting victims to view a page including the following type of tag:

<img src="http://www.example.com">

When the browser sees this tag (even in the attacker's page), it will generate a non-SSL request and send it to www.example.com. The request will include the SESSIONID, and the attacker can sidejack the user's session. The solution is to use the "Secure" flag on your SESSIONID. This flag tells the browser to send the cookie only over an SSL connection.

Bridging the IT gap between rising business demands and ageing tools

More from The Register

next story
NO MORE ALL CAPS and other pleasures of Visual Studio 14
Unpicking a packed preview that breaks down ASP.NET
Cheer up, Nokia fans. It can start making mobes again in 18 months
The real winner of the Nokia sale is *drumroll* ... Nokia
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
Put down that Oracle database patch: It could cost $23,000 per CPU
On-by-default INMEMORY tech a boon for developers ... as long as they can afford it
Google shows off new Chrome OS look
Athena springs full-grown from Chromium project's head
Apple: We'll unleash OS X Yosemite beta on the MASSES on 24 July
Starting today, regular fanbois will be guinea pigs, it tells Reg
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Seven Steps to Software Security
Seven practical steps you can begin to take today to secure your applications and prevent the damages a successful cyber-attack can cause.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.