Mozilla maintains a database containing a set of “root” certificates that we use as “trust anchors”. This database, commonly referred to as a “root store”, allows us to determine which Certificate Authorities (CAs) can issue SSL/TLS certificates that are trusted by Firefox, and email certificates that are trusted by Thunderbird. Properly maintaining a root store is a significant undertaking – it requires constant effort to evaluate new trust anchors, monitor existing ones, and react to incidents that threaten our users. Despite the effort involved, Mozilla is committed to maintaining our own root store because doing so is vital to the security of our products and the web in general. It gives us the ability to set policies, determine which CAs meet them, and to take action when a CA fails to do so.
A major advantage to controlling our own root store is that we can do so in a way that reflects our values. We manage our CA Certificate Program in the open, and by encouraging public participation we give individuals a voice in these trust decisions. Our root inclusion process is one example. We process lots of data and perform significant due diligence, then publish our findings and hold a public discussion before accepting each new root. Managing our own root store also allows us to have a public incident reporting process that emphasizes disclosure and learning from experts in the field. Our mailing list includes participants from many CAs, CA auditors, and other root store operators and is the most widely recognized forum for open, public discussion of policy issues.
The value delivered by our root program extends far beyond Mozilla. Everyone who relies on publicly-trusted certificates benefits from our work, regardless of their choice of browser. And because our root store, which is part of the NSS cryptographic library, is open source, it has become a de-facto standard for many Linux distributions and other products that need a root store but don’t have the resources to curate their own. Providing one root store that many different products can rely on, regardless of platform, reduces compatibility problems that would result from each product having a unique set of root certificates.
Finally, operating a root store allows Mozilla to lead and influence the entire web Public Key Infrastructure (PKI) ecosystem. We created the Common Certificate Authority Database (CCADB) to help us manage our own program, and have since opened it up to other root store operators, resulting in better information and less redundant work for all involved. With full membership in the CA/Browser Forum, we collaborate with other root store operators, CAs, and auditors to create standards that continue to increase the trustworthiness of CAs and the SSL/TLS certificates they issue. Our most recent effort was aimed at improving the standards for validating IP Addresses.
The primary alternative to running our own root store is to rely on the one that is built in to most operating systems (OSs). However, relying on our own root store allows us to provide a consistent experience across OS platforms because we can guarantee that the exact same set of trust anchors is available to Firefox. In addition, OS vendors often serve customers in government and industry in addition to their end users, putting them in a position to sometimes make root store decisions that Mozilla would not consider to be in the best interest of individuals.
Sometimes we experience problems that wouldn’t have occurred if Firefox relied on the OS root store. Companies often want to add their own private trust anchors to systems that they control, and it is easier for them if they can modify the OS root store and assume that all applications will rely on it. The same is true for products that intercept traffic on a computer. For example, many antivirus programs unfortunately include a web filtering feature that intercepts HTTPS requests by adding a special trust anchor to the OS root store. This will trigger security errors in Firefox unless the vendor supports Firefox by turning on the setting we provide to address these situations.
Principle 4 of the Mozilla Manifesto states that “Individuals’ security and privacy on the internet are fundamental and must not be treated as optional.” The costs of maintaining a CA Certificate Program and root store are significant, but there are fundamental benefits for our users and the larger internet community that undoubtedly make doing it ourselves the right choice for Mozilla.