Feeds

Newfangled cookie attack steals/poisons website creds

Google, Facebook risk

Security for virtualized datacentres

A security researcher has discovered a weakness in a core browser protocol that compromises the security of Google, Facebook, and other websites by allowing an attacker to tamper with the cookies they set.

The weakness stems from RFC 2965, which dictates that browsers must allow subdomains (think www.google.com) to set and read cookies for their parent (google.com). The specification also states that if a cookie for a subdomain doesn't already exist, the browser should use the cookie belonging to the parent instead.

The arrangement makes it possible for attackers to steal or even alter the cookies that websites use to authenticate their users. Attackers would first have to identify an XSS, or cross-site scripting, bug in some part of the site they are targeting. But because virtually any subdomain will suffice, the scenario isn't unrealistic, two web security experts said.

"Most websites actually will store session IDs in a cookie and that's actually how they keep track of users throughout the use of their website," said Mike Bailey, a senior researcher for Foreground Security who first documented the flaw at last month's Toorcon hacker conference. "Using the same techniques to attack those cookies, I can really damage sessions and cause some problems."

Bailey's paper goes on to demonstrate how he used the technique to bypass a feature Google recently implemented to beef up security on Gmail and other properties. By exploiting a minor vulnerability in sites.google.com, he was able to falsify the contents of his global Google cookie. Google has since fixed the XSS hole in the subdomain.

In turn, that allowed him fool the Google protection, which checks to make sure the value in the cookie matches a hidden parameter of the login page.

Bailey lists several other sites that have been known to be vulnerable to similar attack techniques. Using an XSS hole on www.advertising.expedia.com, he found it was possible to poison the global cookies for the entire expedia.com domain. Because the site didn't set the cookies with proper escaping, an attacker could have used the weakness to inject malicious javascript into expedia pages.

Chase.com, capitalone.com and chasevisasignature.com either are or were vulnerable to similar attacks because they shared code with images.bigfootinteractive.com, which was vulnerable to XSS exploits.

Bailey said it's not hard to imagine university websites would be vulnerable to such attacks because the domain names frequently use names such as psychology.school.edu, geography.school.edu and so forth. A single bug in a student-maintained computer science project might be enough to compromise personal data stored on the college's student enrollment server, he said.

Websites can guard against attacks by regularly checking their pages for bugs, but because the attack exploits the way browsers are supposed to handle cookies, a more comprehensive fix will probably require a change to the underlying protocols. Which means this attack will probably be around for a while to come.

The paper is here. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
NASTY SSL 3.0 vuln to be revealed soon – sources (Update: It's POODLE)
So nasty no one's even whispering until patch is out
Russian hackers exploit 'Sandworm' bug 'to spy on NATO, EU PCs'
Fix imminent from Microsoft for Vista, Server 2008, other stuff
Microsoft pulls another dodgy patch
Redmond makes a hash of hashing add-on
'LulzSec leader Aush0k' found to be naughty boy not worthy of jail
15 months home detention leaves egg on feds' faces as they grab for more power
Forget passwords, let's use SELFIES, says Obama's cyber tsar
Michael Daniel wants to kill passwords dead
FBI boss: We don't want a backdoor, we want the front door to phones
Claims it's what the Founding Fathers would have wanted – catching killers and pedos
Kill off SSL 3.0 NOW: HTTPS savaged by vicious POODLE
Pull it out ASAP, it is SWISS CHEESE
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Intelligent flash storage arrays
Tegile Intelligent Storage Arrays with IntelliFlash helps IT boost storage utilization and effciency while delivering unmatched storage savings and performance.