The death of MD5 (and some SSL certificates)
Fake SSL Certificates
The bad news is attackers have a much simpler way to get an SSL certificate for an arbitrary site: They can simply buy one. In one case, someone was able to buy a certificate for Mozilla.org from an SSL reseller that did no checks to ensure that the individual was allowed to get certificates or even was affiliated at all with Mozilla.org [2].
In other cases, attackers have been able to get a certificate "Issued in minutes" (to quote RapidSSL.com) with fake requests by faxing in orders on official looking letterhead from organizations for which they want the SSL certificates. To put it simply, they claim to verify your information securely somehow in a few minutes (realistically, some simply query the WHOIS information for your domain and email the contacts listed, giving them a chance to cancel the certificate order). With CCL certificate authorities selling certificates to virtually anyone requesting them with only minimal oversight, the system can be abused easily by attackers.
How to Protect Yourself
Unfortunately, you can't do much to protect yourself. Even if you enable certificate revocation checking in your web browser, if attackers use the MD5 method to create a fake authority certificate, they can simply leave out the certificate revocation information (meaning your browser can't check to see whether it has been revoked or not!). Disabling the root certificates for the authorities that still support MD5 will break a large number of websites, some of which you might want to use (which is largely why, so far, Firefox has not blocked the use of the Comodo SSL authority).
If you want to do this for yourself, the instructions are: Go to the Advanced | Encryption settings tab in Firefox and click on View Certificates, then select Authorities. Now search for the certificate you want to disable (manually, because there is no search function) and select it, then all you have to do is select Edit and uncheck the box for This certificate can identify web sites.
In the future, websites that use this certificate authority to get their website certificates will show up as not signed by a trusted authority, and you'll get the Firefox warning. The process is just as, or more, convoluted in other web browsers. Oh, and most of the certificate authorities in your web browser have no descriptive information. Some of them don't even have valid websites (because they have gone out of business and sold their signing certificates to other companies). Web browsers could make significant improvements in this area.
Conclusion
The good news is that the organizations responsible for technical standards such as MD5 and SHA-1 have not been sitting still. The American National Institute of Standards and Technology (NIST) is holding a competition to develop and choose a new hashing algorithm that should be good for several decades of use [3]. Web browser vendors have also not been standing still. The advent of new "Extended Verification" certificates place much stricter controls on how certificates are issued and to whom (although one could argue this should have been done all along).
Unfortunately, without education, most users will not be able to tell the difference between a website with a "standard" certificate and one with "Extended Verification," although in most cases, the browser places the company name on a green background in the address bar.
Infos
- Creating a rogue CA certificate: http://www.phreedom.org/research/rogue-ca/
- mozilla.dev.tech.crypto: http://groups.google.com/group/mozilla.dev.tech.crypto/browse_thread/thread/9c0cc829204487bf?pli=1
- Cryptographic hash algorithm competition: http://csrc.nist.gov/groups/ST/hash/sha-3/index.html
« Previous 1 2
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs