It looks like Let's Encrypt is preparing to offer free wildcard certificates starting in 2018. This is a bold move by NIST, the National Institute of Standards and Technology, who spearheaded the creation of Let’s Encrypt to help move the Internet to HTTPS everywhere faster. Let’s Encrypt’s intention is quite clear: to rectify launching the Internet without considering the implications of online privacy and trust. But what’s not so clear is what additional risks free wildcard certificates may introduce into encrypted traffic.
Before I examine whether free wildcard certificates are a step forward or a step backward, let’s take a look at the factors that led us to this point. When the Internet was just an infant (spawned from ARPENET, its predecessor), it quickly became a research and academia hub responsible for the creation and standardization of the important protocols we rely on today including TCP/IP (Transmission Control Protocol (TCP) and Internet Protocol (IP)), DNS (The Domain Name System), HTML (HyperText Marketup Language) and HTTP (HyperText Transfer Protocol). Yet, the industry missed one very critical piece of the Internet puzzle. They launched the public Internet without security and privacy controls.
The Internet erupted using primarily only HTTP—with no S. Which stands for SECURITY. Quickly peer-to-peer networking and file sharing became an unsecured hot reality! In turn, privacy and trust became a prominent online fear. With the dot.com bubble starting to burst and websites like Yahoo and eBay bursting at the seams with growth—countless vulnerabilities and cyber attacks began to emerge--from widespread denial of service and Napster privacy complaints to the SQL Slammer worm that spread worldwide in 10 minutes!
Hence, Netscape introduced Secure Socket Layer (SSL) cryptography and keys and certificate or machine identities became our online security and privacy activists. Very quickly, cryptography keys and digital identity .X509 certificates were tied to every DNS website. Soon the organizational PKI (Public Key Infrastructure) was up and running like a well-oiled machine.
While security professionals build PKIs to enable encryption everywhere, the business side of humanity wanted administration of it to be simpler. Managing a PKI is not exactly easy. And the business side of the Internet needed to rollout a PKI as fast as possible, ensuring business growth at the speed of business, without security bottlenecks. So, the wildcard identity certificate was born—the ‘easy red button’ to enabling SSL/TLS encryption without having to manage it.
Now don’t get me wrong, wildcard certificates are time and money savers as well. But they can be a double-edged sword. A wildcard certificate allows an admin to secure an unlimited number of first-level sub-domains on a single domain name. That means an organization can get a digital certificate with the common name as *.mydomain.com and use it on all subsequent levels of that domain without receiving any errors. If you have several sub-domains you would have to buy a single SSL/TLS certificate for each one, but with a wildcard certificate you just buy and use one certificate for all subsequent domains. They are seen as easier to manage and cheaper. Well, way cheaper now that Let’s Encrypt is giving them away for free. So, a wildcard certificate simplifies administration—but there are drawbacks.
First, it’s inherently less secure. If an admin only uses one certificate and private key on multiple websites and private servers, it only takes one server to be compromised for them all to be assumed compromised. Now, some certificate providers allow for new wildcard certificates using the same domain name with unique private keys making it just as secure as a single domain, but, and this brings me to my second point, it’s difficult to manage.
Most organizations overuse wildcard certificates without much consideration for management issues. And, most organizations still manage their PKI manually. If a wildcard certificate needs to be revoked, all sub-domains will need a new certificate too. On top of this, renewals will be coming up much more often now due to recently mandated, shorter certificate validity periods. Over using wildcards to make administration easier will end up making things more difficult.
The underlining issue is manual management. Putting the PKI under automated centralized management so you have global visibility of the entire infrastructure solves most wildcard usage security and managements issues and allows the security organization to put certificate issuance under policy to control wildcard usage enterprise-wide.
Remember, wildcards may be easier to rollout but the risk of the entire domain and all associated sub-domains that stem from one wildcard compromise just isn’t acceptable. I’d recommend putting your entire machine identity infrastructure under an automated life-cycle management platform that enables your organization to securely, effectively and properly deploy SSL/TLS everywhere.