In the wake of the Comodo SSL Certificate Authority (CA) having been compromised by an Iranian hacker the Electronic Frontier Foundation published more evidence of problems in the SSL signing industry.
While many were critical of Comodo’s hard coding passwords into public facing code and using their root certificate to sign certificates, now there is more evidence of industry-wide lax practices.
Chris Palmer wrote a blog on Tuesday outlining work the EFF had done analyzing the quantity of certificates that were signed and trusted by all of our browsers that were technically invalid and could be used for fraud.
The particular practice the EFF was looking for was the signing of certificates that did not contain fully-qualified domain names.
To obtain verification of your identity for the CA to sign a certificate, the certificate must contain something that globally only you could be identified by.
If I try to get a certificate for just plain www, I should be rejected. Yet if I try to purchase secure.sophos.com, you could verify that I am allowed to represent Sophos, and that this certificate would not be valid for any other organization.
So what did the EFF find? They found that certificate authorities have signed over 37,000 certificates that are not specific to any organization, they contain only a hostname. The worst offender was GoDaddy.com.
Each and every one of these could be used to impersonate some local server on your intranet by an intruder…
Wait! It gets worse.. 28 Extended Validation certificates were issued in this manner.. 10 of which are still valid. What is Extended Validation? Wikipedia states three specific conditions must be met:
1. Establish the legal identity as well as the operational and physical presence of website owner.
2. Establish that the applicant is the domain name owner or has exclusive control over the domain name.
3. Confirm the identity and authority of the individuals acting for the website owner, and that documents pertaining to legal obligations are signed by an authorised officer.
Most of the wrongly issued EV certificates were issued by Verisign, including one they signed for themselves.
While I hope that the awareness being raised by the EFF report shakes up the certificate industry, I have a feeling the lack of verification in the way certificates are being issued may just be the beginning of the problems.
While it is nice to see a padlock in your browser, or know that your new Twitter widget is using encryption over the air/wire, it doesn’t mean much if certificates are being issued that compromise the entire system.
At the moment little can be done by end users about this problem. As a community we need to continually apply pressure on the industry to make meaningful changes to the process to make the best of the transitive trust model that we currently possess.
One thing companies can do for their internal web assets is to get away from using just hostnames like intranet, webmail and wiki for their web services. Sticking to fully qualified internal domains (webmail.sophos.local) helps mitigate exploitation through these invalidly issued certificates.