Yubikey authentication module
Create an API key for YubiCloud
Grab a free API key from Yubico. One application, context or server should mean a new client id.
Enter your email, select the
Yubikey OTP input and touch your Yubikey. The resulting page will include:
Client ID: <clientId> Secret Key: <secretKey>
Store these credentials in a safe place (password manager) as you will need them in the next step.
Create the Yubikey authentication module
After the system-wide mapping is completed and the API credentials generated, create and add the following configuration line to
# Enable YubiCloud OTP Validation (implicitly includes `mode=client` and the default validation `urllist`). auth required pam_yubico.so id=<clientId> key=<secretKey> authfile=/etc/yubikeys
To enable debugging, create the log files and add the
debug_file parameters as arguments to
❯ touch /var/log/yubikey-auth.log ❯ chmod go+w /var/log/yubikey-auth.log
auth required pam_yubico.so id=<clientId> key=<secretKey> authfile=/etc/yubikeys debug debug_file=/var/log/yubikey-auth.log
Remove when debugging is no longer necessary.
Update common-auth authentication module
try_first_pass directive to the
pam_unix.so backend inside the
/etc/pam.d/common-auth module so that it first attempts to use the previous stacked module's password in case that satisfies this module as well before asking it again. Not all distributions have a
common-auth file, so you may look on other files to see what makes sense.
Also, you must include the previously created Yubikey authentication module (order matters):
auth include yubikey-auth auth [success=1 default=ignore] pam_unix.so nullok_secure try_first_pass