Certificate Authorities Hacked – So Who Can You Trust?
September 12, 2011 3 Comments
Last week’s revelations that one, and possible multiple, Certificate Authorities (CA) had been breached really rocks the basic foundation of information security as we know it. When you couple this news with the RSA breaches reported earlier this year, there are clearly some large and foreboding cracks in some of the foundational underpinnings of security – SSL and Public Key Infrastructure (PKI), for example – that require us to take a hard look at the entire concept of trust.
Early last week, news broke about the hack of Dutch certificate authority (CA) DigiNotar, which followed the patterns of an earlier hack of Comodo, another CA. The hacker taking credit for this breach claims he has infiltrated four other CAs, including GlobalSign, although GlobalSign is rejecting the claim. Analysis has shown that the hacker used some very sophisticated techniques to penetrate the CA servers at DigiNotar and obtain root access for five of the company’s root certificates.
Without getting too deep into digital certificates, it is useful to know that CA like DigiNotar issue certificates that are at the heart of SSL and PKI. The issued certificate is linked through a chain of trust back to the certificate authority’s root certificate. The security of issued certificates, and the security of the implementations that use them, is only as good as the security of the root. If the root is compromised, all of the issued certificates are compromised.
You know when you enter a transaction on a web site and the address bar turns green? That happens because the browser recognizes that the site is using a certificate that has a chain of trust back to a root recognized by the browser. If someone were to compromise a CA, they could issue bogus certificates that would have a valid chain of trust. These certificates could then be used to produce “man in the middle” attacks that the browser will view as trusted transactions. That is exactly how the hacker used the infiltration of DigiNotar.
Beyond the micro issues of the attacks, the infiltration of one or more CAs has forced the industry to ask a question fundamental to many security processes: can CAs be trusted to protect certificate roots and the chain of trust? Will this damage the trust, and therefore the usefulness, of SSL? This would also effect by extension any web transaction protected by SSL. No trust, no e-commerce. Starting to get the idea?
In response to the revelations of the hack, the major browser vendors no longer recognize the five root certificates of DigiNotar. Any transaction that used a certificate based on these roots is no longer viewed as secure. No green address bar. The other CA’s are being pressed to validate their practices and safeguards, and early returns have shown many to be lacking.
Think of all of the people in the world walking around with identity cards that use PKI. These cards provide access to physical locations, and many are an authentication factor used to enter highly secure systems. Can the chain of trust for these cards still be trusted? If I could hack the chain of trust for a PKI implementation, could I create cards for access to nuclear reactors, weapon systems, water treatment plants, and airport tarmacs? Many will tell you no, that there are safeguards in place. But as much as that questions sets off my fear-mongering alarms I think the questions are valid to be asked.
How about the cloud? There is no more overused term on the planet right now as “in the cloud”, and vendors defend the security of the cloud by invoking the promise of two-factor authentication. But one such factor would likely be an RSA token or PKI. Still feel good about the cloud? Ready to move your most sensitive data to a cloud server?
The public likely does not get the criticality of hacking a certificate authority, but I do, and it really makes me uncomfortable. It turns out that the infrastructure of trust is actually quite fragile and can be profoundly compromised. It is in fact only as good as the ability of the CA companies to defend the process, and this event has shown them to be lacking.
Ultimately it all comes down to “who can you trust?” and today we know that the answer to that question is not what we thought. This leads us back to the notion of adding detection in equal parts to prevention. When trust begins to break down, so will some of the preventive measures of IT security. All the more reason to have a tool that detects the attacks that evade protections.