Now with added Chromium!

Fun and games with Nginx and client authentication certificates means we need to deploy certificates to the user for them to trust our CA and have a trusted personal certificate to validate with our server.

I can see why many just pop up a help page and navigate the user through importing the CA and their certificate in the browser. We need to make this a bit more automated though as the machines will be out with customers.

There’s a lot of controversy over Firefox’s certificate stores. Let’s just stay out of that an inject or certificates using some command line tools.

The tools we need (certutil and pk12util) are part of the package libnss-tools which you may need to install first.

$ sudo apt install libnss3-tools

Once we have out tools we’ll need the certificates we want to install. The public one for the Certificate Authority is generally straight forward and comes as a PEM formatted .crt file. If not, it’s time to get down with openssl and convert it to a PEM version.

For the client certificate you’ll need both the public and the private key. These will typically be separate PEM formatted files – probably a .key and a .pem. For this we will need to combine them into a single pkcs12 format file – so we will need to get down with openssh to do this.

$ openssl pkcs12 -export -inkey client01.key -in client01.pem -name Client01 -out client01.pfx

This will take both parts and convert them into a single .pfx file which we can then import into the certificate store.

Now for the fun part – finding your Mozilla certificate store. It will be in your profile, but it will have a string of random characters/digits in the path. eg.


Hmm, but according to Mozilla your default profile folder will contain .default in the name. Not really that helpful – I decided to script the process and have it drop the certificates into any path listed in ~/.mozilla/firefox/profile.ini certificate store that it finds. I’m sure this can be made more elegant, but it works.



# Install certificates into Firefox profiles

for PROFILE in $(grep "Path=" $BASE/profiles.ini | sed s/Path\=//)
  echo Installing to $PROFILE
  certutil -A -i ca.crt -n MyCA -t "CT,C,T" -d $BASE/$PROFILE
  pk12util -i MyClient.pfx -n MyClient -d $BASE/$PROFILE -W $1

You’ll want to edit this to include your password or pass it as a parameter and use $1. It’s also possible to use a lowercase option -w which will point to a file containing the password – which may be useful for some automation practices.

undefined Chromium Certificates

Turns out I inadvertently stepped into a Chromium solution too. Whilst inserting certificates into Firefox I found a ~/.pki folder that also contained a certificate store.

Then when I discovered many of the customer systems used Chromium I installed it for testing and put the certificates into the ~/.pki folder using certutil and pk12util and it worked! Chromium now has the required certificates and works just as required.

$ certutil -A -i ca.crt -n MyCA -t "CT,C,T" -d ~/.pki
$ pk12util -i MyClient.pfx -n MyClient -d ~/.pki -W mypassword

A simple modification of the script and I can have both.