Security/PamUsb/GettingStarted
Getting Started
Setting up pam_usb requires the following, Install:
- Set up devices and users
- Configuring PAM for system authentication
- (Optional) Configuring pamusb-agent to run programs when the device is inserted or removed
Setting up Devices and Users
Once you've connected your USB device to the computer, use pamusb-conf to add it to the configuration file:
pamusb-conf --add-device masterkey Please select the device you wish to add. * Using "USB Flash Disk (FBF1101121100745)" (only option) Which volume would you like to use for storing data ? 0) /dev/sdd1 (UUID: 335F405C0A8030B0) 1) /dev/sdd3 (UUID: 3ea9b653-a346-4827-85a8-b809bcec4028) 2) /dev/sdd2 (UUID: c7467fbf-6ef2-40ac-9ce1-d019292fc266) [0-2]: 1 Name : masterkey Vendor : USB Model : Flash Disk Serial : FBF1101121100745 UUID : 3ea9b653-a346-4827-85a8-b809bcec4028 Save to /etc/pamusb.conf ? [Y/n] y Done.
Device name can be any arbitrary name you'd like. Also, you can add as many devices as you want.
Next, configure users you want to be able to authenticate with pam_usb:
pamusb-conf --add-user root Which device would you like to use for authentication ? * Using "masterkey" (only option) User : root Device : masterkey Save to /etc/pamusb.conf ? [Y/n] Done.
pamusb-conf --add-user didier Which device would you like to use for authentication ? * Using "masterkey" (only option) User : didier Device : masterkey Save to /etc/pamusb.conf ? [Y/n] Done.
Check the configuration
You can run pamusb-check anytime to check if everything is correctly worked. This tool will simulate an authentication request (requires your device to be connected, otherwise it will fail).
pamusb-check didier * Authentication request for user "didier" (pamusb-check) * Device "masterkey" is connected (good). * Performing one time pad verification... * Access granted.
Setting up the PAM module
To add pam_usb into the system authentication process, we need to edit <path>/etc/pam.d/common-auth</path>
This file can be known as /etc/pam/system-auth.
Your default PAM common-auth configuration should include the following line:
auth required pam_unix.so nullok_secure
This is a current standard which uses passwords to authenticate a user.
Alter your /etc/pam.d/common-auth configuration to:
auth sufficient pam_usb.so auth required pam_unix.so nullok_secure
The suffient keyword means that if pam_usb allows the authentication, then no password will be asked. If the authentication fails, then the default password-based authentication will be used as fallback.
If you change it to required, it means that *both* the USB flash drive and the password will be required to grant access to the system.
At this point, you should be able to authenticate with the relevant USB device plugged-in.
$ su - * pam_usb v0.5.0 * Authentication request for user "root" (su-l) * Device "masterkey" is connected (good). * Performing one time pad verification... * Regenerating new pads... * Access granted. #
Agent
The pam_usb agent (pamusb-agent) allows you to automatically execute commands upon locking and unlocking events. Those events are generated when you insert or remove your authentication device. To configure the commands, you have to edit pam_usb's configuration file (<path>/etc/pamusb.conf</path>) and add agent entries into your user section.
For instance, you could automatically start your screensaver as soon as you remove the device, and deactivate it when you plug the device back.
GNOME (gnome-screensaver):
<user id="didier">
<device>didier-key</device>
<agent event="lock">gnome-screensaver-command --lock</agent>
<agent event="unlock">gnome-screensaver-command --deactivate</agent>
</user>
KDE3 (kscreensaver via DCOP):
<user id="didier">
<device>didier-key</device>
<agent event="lock">dcop kdesktop KScreensaverIface lock</agent>
<agent event="unlock">dcop kdesktop KScreensaverIface quit</agent>
</user>
KDE4 (kscreensaver via DBUS):
<user id="didier">
<device>didier-key</device>
<agent event="lock">qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock</agent>
<agent event="unlock">qdbus org.kde.screenlocker /MainApplication quit</agent>
</user>
You can execute more commands by adding extra <agent> entries.
$ ./pamusb-agent pamusb-agent[6674]: pamusb-agent up and running. pamusb-agent[6674]: Watching device "masterkey" for user "didier" pamusb-agent[6674]: Device "masterkey" has been removed, locking down user "didier"... pamusb-agent[6674]: Running "qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock" pamusb-agent[6674]: Running "ssh-add -D" All identities removed. pamusb-agent[6674]: Running "fusermount -u /home/didier/unsafe" pamusb-agent[6674]: Locked. pamusb-agent[6674]: Device "masterkey" has been inserted. Performing verification... pamusb-agent[6674]: Executing "/usr/bin/pamusb-check --quiet --config=/etc/pamusb.conf --service=pamusb-agent didier" pamusb-agent[6674]: Authentication succeeded. Unlocking user "didier"... pamusb-agent[6674]: Running "qdbus org.kde.screenlocker /MainApplication quit" pamusb-agent[6674]: Running "/home/didier/.kde/Autostart/ssh-add.sh" pamusb-agent[6674]: Running "encfs /home/didier/.safe/ /home/didier/unsafe --extpass=ksshaskpass" pamusb-agent[6674]: Unlocked.
F.A.Q.
rm ~/.pamusb/*
Fine Tuning
Agent must
- Lock/Unlock screen
- call ssh-agent to load/unload private key without password
- encrypt/decrypt safe directories automatically.
Fichier <path>/etc/pamusb.conf</path>
<?xml version="1.0" ?><configuration>
<!-- Default options -->
<defaults>
<option name="hostname">didier.home.org</option>
</defaults>
<!-- Device settings -->
<devices>
<device id="masterkey">
<vendor>USB</vendor>
<model>Flash Disk</model>
<serial>FBF1101121100745</serial>
<volume_uuid>c7467fbf-6ef2-40ac-9ce1-d019292fc266</volume_uuid>
</device>
</devices>
<!-- User settings -->
<users>
<user id="root">
<device>masterkey</device>
</user>
<user id="didier">
<device>masterkey</device>
<agent event="lock">qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock</agent>
<agent event="lock">ssh-add -D</agent>
<agent event="lock">fusermount -u /home/didier/unsafe</agent>
<agent event="unlock">qdbus org.kde.screenlocker /MainApplication quit</agent>
<agent event="unlock">/home/didier/.kde/Autostart/ssh-add.sh</agent>
<agent event="unlock">encfs /home/didier/.safe/ /home/didier/unsafe --extpass=ksshaskpass</agent>
</user>
</users>
<!-- Services settings (e.g. gdm, su, sudo...) -->
<services>
</services>
</configuration>
Usefull scripts
Depending on your desktop environment, you have to add pamusb-agent to the list of autostarted applications so it will be started automatically.
KDE Autostart script
We use <app>ksshaskpass</app> to make application password-less.
To use this script, you must create <path>/var/log/didier</path> directory, and change its owner and group before use. In that case :
mkdir /var/log/didier
chown didier:didier /var/log/didier
File <path>/home/didier/.kde/Autostart/pamusb-agent.sh</path>
#!/bin/bash
nohup /usr/bin/pamusb-agent 1>/var/log/didier/pamusb-agent.log 2>&1 &
Associate logrotate configuration file <path>/etc/logrotate.d/didier</path>
/var/log/didier/pamusb-agent.log {
weekly
compress
missingok
notifempty
rotate 4
}
GNOME:
- Open System -> Preferences -> Sessions
- Select Startup Programs and press Add
- Enter pamusb-agent and press OK
- Press Close
There are many options available to fine configure pam_usb.
Check out the Configuration File.