Saturday, July 21, 2007

USB "Key" based authentication using pam_usb in Fedora

What Is pam_usb?

pam_usb provides hardware authentication for Linux using ordinary USB Flash Drives.
It works with any application supporting PAM (Pluggable Authentication Module), such as su, any login manager (GDM, KDM), etc. The pam_usb package contains:

http://www.pamusb.org/

So? What does it do?

pam_usb enables you to login to your system using a USB "Key" as a physical authentication device. Ever watched some of those movies where user required to key in some sort of card before logging into the computer? Well, pam_usb allows you to do this on Linux, using your USB drive!.

Getting pam_usb

pam_usb 0.3.3 is available in Fedora repository.
yum install pam_usb pam_usb-hotplug


Setting up Your Computer

1 . Setting up console login to use pam_usb
add this entry to the first line in /etc/pam.d/login
auth       sufficient   pam_usb.so


2 . Setting up GDM to use pam_usb
add this entry to the first line in /etc/pam.d/gdm
auth       sufficient   pam_usb.so allow_remote


1 . Setting up su command to use pam_usb
add this entry to the first line in /etc/pam.d/su
auth       sufficient   pam_usb.so


more details about options can be acquired from the quickstart, located at
file:///usr/share/doc/pam_usb-0.3.3/quickstart.html

Creating your DSA key pair

To enable your USB drive as an authentication device, you will need to generate a set of public and private key which one will reside in the USB device and another in your home folder.

To generate the key, first, make sure your USB drive is mounted, then this command:
usbadm keygen /path/to/usb/mountpoint username keybits

eg:
usbadm keygen /media/usbdrive root 1024


Thats it, you're done. Try su-ing to root to test out whether it works or not.

Enabling log for debugging

In case it did not work, you can enable pam_usb logging to find out whats wrong. To enable logging, add log_file=/var/log/pam_usb.log at the end of pam_usb entry in the pam.d files.

eg:
auth       sufficient   pam_usb.so log_file=/var/log/pam_usb.log


then create an empty log file
touch /var/log/pam_usb.log


done.

Ref:
http://forums.gentoo.org/viewtopic-t-305540-highlight-pamusb.html
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