This is a guide that is tested to work with Ubuntu and its Derivatives including Linux Mint. Note that not all derivatives were tested. If you test this against an Ubuntu derivative and it works or does not work, please contact me or leave a comment to let me know.
Last updated 10 Jan 2022
Preface
US Department of Defense (DoD) now limits access to many of its websites to be via a smart Common Access Card (CAC) authenticated with a Personal Identification Number (PIN). The following is a guide to assist in setting up Linux Mint to access CAC-enabled DoD websites.
Install the Middleware
The Linux CAC Reader stack is based on a set of middleware called PCSC (Personal Computer Smart Card), written by the MUSCLE (Movement for the Use of Smart Cards in a Linux Environment) project.
Enter this into Terminal and execute:
sudo apt install libpcsclite1 pcscd pcsc-toolsPKCS #11 module
There are three working modules to access the PKCS #11 keys on your CAC. Each have their strengths and limitations. You will need to choose which version works best for you. In most situations, OpenSC is preferred.
OpenSC
OpenSC provides a set of utilities to access smart cards. It facilitates their use in security applications such as mail encryption, authentication, and digital signature. This module has a broader feature set than CoolKey or CACkey and you are able to access your PIV certificate for those individuals that are Dual Persona. This module is speedy like CoolKey and doesn’t lag like CACkey. This may be the best option if you are dual persona and do not wish to use CACkey from DISA.
sudo apt install openscSmart Card Reader Driver
Without installing any additional drivers the following card readers are tested and work without issue: SCR3310 by SCM Microsystems (Currently being issued to members by the US Army for use on personal computers) SCR3500 by SCM Microsystems (Many members purchase this as a more compact alternative to the SCR3310) O2 Micro, Inc (built-in to many Dell laptops)
You may have to install additional drivers for your hardware. Check your hardware and search using the key word pcsc.
Start Up the Daemon
In Terminal:
sudo systemctl start pcscd
sudo systemctl enable pcscdTesting your Smart Card Driver
Open a terminal (ie konsole, x-term or other) and type/enter. You might have to insert a smart card in order for the message to pop-up.
pcsc_scanSimilar to the following means the card reader is working properly:
PC/SC device scanner V 1.4.18 (c) 2001-2011, Ludovic Rousseau <ludovic.rousseau@free.fr> Compiled with PC/SC lite version: 1.8.8 Using reader plug’n play mechanism Scanning present readers… 0: O2 Micro Oz776 00 00 Sun Mar 24 11:40:07 2013 Reader 0: O2 Micro Oz776 00 00 Card state: Card removed
Similar to this indicates a need to check for additional driver requirements for your hardware:
PC/SC device scanner V 1.4.18 (c) 2001-2011, Ludovic Rousseau <ludovic.rousseau@free.fr> Compiled with PC/SC lite version: 1.8.8 Using reader plug’n play mechanism Scanning present readers… Waiting for the first reader…
Authority Certificates
Download extract and install the DoD Certificates.
The certificates can be obtained from this link:
https://dl.dod.cyber.mil/wp-content/uploads/pki-pke/zip/unclass-certificates_pkcs7_v5-6_dod.zip
Make note of the location you stored these certificates
Configure Firefox
Firefox requires manual selection of the PKCS #11 module.
Import Certificates
The current method of installing the certificates is one-by-one. This can be done through Firefox import mechanism.
Firefox 57 and later
Preferences > Privacy & Security
Scroll Down to Security Section
Select View Certificates
Continue for All versions of Firefox
Select the Import… button at the bottom of the dialog and install the following certificates.
- Certificates_PKCS7_v5.10_WCF_DoD_WCF_Root_CA_1.der.p7b
- Certificates_PKCS7_v5.10_WCF.der.p7b
- Certificates_PKCS7_v5.10_WCF.pem.p7b
Set Firefox to Require Selection of Certificate
When accessing multiple CAC protected pages, some pages will require different certificates from the card. Some require the non-email certificate while Enterprise Email will require the email certificate.
Preferences > Privacy & Security
Scroll Down to Security Section
Below the Certificates heading, select the radio button in front of “Ask me every time.”
Set CAC Module
CAC Module Setup
Open Preferences > Privacy & Security
Scroll Down to Security Section
Select Security Devices
Check the left column. It should show an entry similar to “CAC Module” along with certificate(s) as a sub-item. If it doesn’t work then the entries are wrong.
Select the entry and select Unload to remove the security device
To install/reinstall the CAC driver in Firefox using the above listed Security Devices
Select Load on the dialog box
Module name should be something like: DoD CAC
Module filename: either type in or browse to the location of the opensc-pkcs11.so drivers
Example:
/usr/lib/pkcs11/opensc-pkcs11.soConfigure Chrome / Chromium
Unfortunately, Chrome (Chromium) doesn’t automatically recognize the CAC once you’ve completed all the previous steps but it doesn’t take much more work to get Chrome to work with the CAC.
In Terminal:
modutil -dbdir sql:.pki/nssdb/ -add "CAC Module" -libfile /usr/lib/pkcs11/opensc-pkcs11.soMake sure that the utility is properly installed, in Terminal:
modutil -dbdir sql:.pki/nssdb/ -listIf it is properly installed there will be an entry with “CAC Module” and details of the library, slot and status. If you were not in your home directory when configuring modutil you will receive an error like:
"modutil: function failed: SEC_ERROR_BAD_DATABASE: security library: bad database."Chrome should now be able to utilize the CAC without any issues
Removing CAC Module
If you have previously installed libcackey.so and you wish to utilize CoolKey instead, you will have to unload the “CAC Module”: modutil -dbdir sql:.pki/nssdb/ -delete “CAC Module”
Test out your browser
Go to a CAC-enabled web site (www.us.army.mil) and test the CAC login.
Be patient as there may be a delay while authenticating with the CAC.
The PIN and certificate selection authentication process is in the reverse of what you may be used to when using non-Linux machines. Expect to be prompted first for PIN and then certificate selection.
Troubleshooting
At anytime if you don’t seem to get response from the Smart Card, check and see if the daemon is active by executing this in terminal:
pcsc_scanIf you remove and insert your card with no response during the scan, the daemon has crashed.
If you find that the pcsc daemon has crashed you can run this in terminal to restart the daemon:
sudo systemctl restart pcscdExternal Links
MilitaryCAC.com Linux Page
DoD CAC Instructions for openSUSE
CACkey Alternate Download Site
https://public.cyber.mil/pki-pke/end-users/getting-started/linux-firefox/