More holes found in Web's SSL security protocol

At Black Hat, researchers say these bugs could be used to create undetectable man-in-the middle attacks

Security researchers have found some serious flaws in software that uses the SSL (Secure Sockets Layer) encryption protocol used to secure communications on the Internet.

At the Black Hat conference in Las Vegas on Thursday, researchers unveiled a number of attacks that could be used to compromise secure traffic travelling between Web sites and browsers.

This type of attack could let an attacker steal passwords, hijack an on-line banking session or even push out a Firefox browser update that contained malicious code, the researchers said.

The problems lie in the way that many browsers have implemented SSL, and also in the X.509 public key infrastructure system that is used to manage the digital certificates used by SSL to determine whether or not a Web site is trustworthy.

A security researcher calling himself Moxie Marlinspike showed a way of intercepting SSL traffic using what he calls a null-termination certificate. To make his attack work, Marlinspike must first get his software on a local area network. Once installed, it spots SSL traffic and presents his null-termination certificate in order to intercept communications between the client and the server. This type of man-in-the-middle attack is undetectable, he said.

Marlinspike's attack is remarkably similar to another common attack known as a SQL injection attack, which sends specially crafted data to the program in hopes of tricking it into doing something it shouldn't normally do. He found that if he created certificates for his own Internet domain that included null characters -- often represented with a \0 -- some programs would misinterpret the certificates.

That's because some programs stop reading text when they see a null character. So a certificate issued to\ might be read as belonging to

The problem is widespread, Marlinspike said, affecting Internet Explorer, VPN (virtual private network) software, e-mail clients and instant messaging software, and Firefox version 3.

To make matters worse, researchers Dan Kaminsky and Len Sassaman reported that they had discovered that a large number of Web programs are dependant on certificates issued using an obsolete cryptographic technology called MD2, which has long been considered insecure. MD2 has not actually been cracked, but it could be broken within a matter of months by a determined attacker, Kaminsky said.

The MD2 algorithm was used 13 years ago by VeriSign to self-sign "one of the core root certificates in every browser on the planet," Kaminsky said.

VeriSign stopped signing certificates using MD2 in May, said Tim Callan, vice president of product marketing at VeriSign.

However, "large number of Web sites use this root, so we can't actually kill it or we'll break the Web," Kaminsky said.

Software makers can, however, tell their products to not trust MD2 certificates; they can also program their products to not be vulnerable to the null-termination attack. To date, however, Firefox 3.5 is the only browser that has patched the null-termination issue, the researchers said.

This is the second time in the past half-year that SSL has come under scrutiny. Late last year, researchers found a way to create a rogue certificate authority, that could in turn issue phoney SSL certificates that would be trusted by any browser.

Kaminsky and Sassaman say there are a raft of problems in the way SSL certificates are issued that make them insecure. All of the researchers agreed that the x.509 system that is used to manage certificates for SSL is out-of-date and needs to be fixed.

Join the CSO newsletter!

Error: Please check your email address.

Tags securitySSL

More about etworkVeriSign Australia

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Robert McMillan

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts