Certificate Authorities (CA) in Google Chrome / Chromium and Firefox on Linux

Firefox ships with its own set of root CAs ("Builtin Object Token" as the Security Device in advanced preference settings). Here is the list of all root CAs included in Firefox along with their fingerprints:
https://mozillacaprogram.secure.force.com/CA/IncludedCACertificateReport

Builtin root CAs are hardcoded in /usr/lib/firefox/libnssckbi.so . You can see a list of all CAs in Firefox preferences (advanced settings).

CAs marked as "Software Security Device" are usually intermediate certificates that are downloaded from websites and stored locally. These CAs that are not builtin are either stored on a PKCS#11 compatible smartcard attached to your PC/laptop or saved to your home directory:
certutil -d $HOME/.mozilla/firefox/xxx.default -L

Chromium / Google Chrome does not ship with its own CA list but uses the CAs from the underlying operating system:
https://www.chromium.org/Home/chromium-security/root-ca-policy

In Ubuntu 16.04 these CAs are hardcoded in /usr/lib/x86_64-linux-gnu/nss/libnssckbi.so which is part of the package "libnss3". You should therefore update this package as soon as there is an update available to keep your builtin CA list up-to-date.

CAs that are not builtin and that you installed manually are stored in your home directory:
certutil -d sql:$HOME/.pki/nssdb -L

Important things to note:

  • The security of SSL encrypted websites (https://...) depends on the root CA which is used to sign the website certificate. These CAs are stored locally on your device in different locations based on the browser you are using.
  • There are 2 kinds of CAs:
    1. Builtin CAs that ship with your browser or linux installation. They are stored in shared object files. There is probably no easy way to edit this list unless you change the source files and recompile the package. Nevertheless in both browsers you can remove all trust from a builtin certificate which is basically the same as deleting it.
    2. Manually added CAs are stored in your home directory. You can easily edit that list within the settings of the browser or on the command line.
  • Both Firefox and Chromium / Google Chrome use NSS certificate databases to store manually added CAs that are not builtin. But they use different directories. Maybe you could use symbolic links to point both directories to the same database. That way both browsers would be using the same manual CA list.Currently Firefox uses by default the legacy dbm database version (cert8.db, key3.db) and Chromium / Google Chrome uses by default the new SQLite database version (cert9.db, key4.db). There seems to be an environment variable NSS_DEFAULT_DB_TYPE that makes Firefox use the new SQLite database version as well (s. https://wiki.mozilla.org/NSS_Shared_DB_Howto).
  • Neither Firefox nor Chromium / Google Chrome are using CAs from the package "ca-certificates".
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