This is a collection of instructions and simple example scripts to help customize the login to a Linux box with pam, using libpam-python.
The instructions and the scripts have been tested with Ubuntu 12.04 LTS. Run them at your risk.
Since working with PAM can lead to problems in authentication, keep a shell with root access open while experimenting.
Install the package libpam-python:
sudo apt-get install libpam-python
Copy the provided
sudo cp pam_custom.py pam_custom.sh /lib/security
Make a backup of the file
sudo cp /etc/pam.d/common-auth /etc/pam.d/common-auth.original
Edit the file
/etc/pam.d/common-auth introducing a line in which you
declare your custom authentication method. It should be something like
auth [success=2 default=ignore] pam_python.so pam_custom.py /lib/security/pam_custom.sh
and should be put just before (or after, according to your needs) the other authentication methods.
"success=2" means that the 2 following lines should be skipped in case of success (edit as needed)
"pam_python.so" is the name of the shared object that will be called by pam
"pam_custom.py" is the script in python that we provide
"/lib/security/pam_custom.sh" is the bash script that is called by the python script (if needed)
Edit the file
/lib/security/pam_custom.sh according to your needs. It is a bash script that
receives username and password as command line arguments, and must exit with 0 if the authentication
is to be granted, or a non-zero value otherwise.