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1. YubiPAM Introduction

The YubiPAM module provides a simple, easy to configure, way to integrate the
Yubikey into your existing user authentication infrastructure. PAM is used by
GNU/Linux, Solaris and Mac OS X for user authentication.

2. Status

  1. Manual add/delete from database. Using the ykpasswd tool you can add
     delete yubikey entries from the database (default: /etc/yubikey).

  2. Per user accounting. Supports individual user account authorisation.
     Every user may have multiple Yubikey dongles only make sure you are using
     different public UID's on every Yubikey dongle.

  3. Single and second factor sign in. Next to single factor ie. Yubikey OTP
     you can define an additional passcode. The pam module will detect if the
     second factor passcode is needed.
  4. Static heuristic support. Heuristic support for OTP data deltas is hard
     coded. This will be changable in the next release.

3. Build

Build the YubiPAM module by using autotools. First generate the configure file
  $ autoreconf -i

You should run the configure file which will generate the Makefile. Run make
to build the YubiPAM module.
  $ ./configure
  $ make
  $ sudo make install
  $ sudo addgroup yubiauth
  $ sudo touch /etc/yubikey
  $ sudo chgrp yubiauth /etc/yubikey /usr/local/sbin/yk_chkpwd
  $ sudo chmod g+rw /etc/yubikey
  $ sudo chmod g+s /usr/local/sbin/yk_chkpwd

4. Configuration

Install it in your PAM setup by adding a line to an appropriate file in the
director /etc/pam.d/:

  auth sufficient

and ensure is located in /lib/security/

Supported PAM module parameters are:

        enable debug.

        enable echoing of the OTP, after all it's only a one time pad.

        enable yubikey auth for users in the given file. Eash line
        can contain one user.
        Ex: include_users=/etc/yubikey.users

        disable yubikey auth for users in the given file. Eash line
        can contain one user.
        Ex: exclude_users=/etc/yubikey.users

	instructs the module to not save the pam authtok to allow for
	two-factor authentication with other pam modules such as pam_ecryptfs
	which is configured to use the user's passphrase.

        instead of the OTP, pam authtok will only contain the
        passcode. This can be very handy when you are using other
        pam modules like pam_ecryptfs.

        allows user to enter passcode+OTP on a single prompt line.
        Useful for services that don't work with multiple prompt two-factor
        auth (e.g. certain screensavers, X display managers)
        The passcode and OTP must be separated with a single | character

        emulate the default Unix password prompt, to avoid indicating
        a Yubikey is to be used

Most keyboard layouts will work out of the box, as Yubico designed the
keypresses used by the Yubikey to be the same on many layouts (qwerty,
azerty, etc). Some layouts, however, such as Dvorak and Colemak do not
share the same character mapping. English Dvorak and Colemak will work
out of the box for authentication, as will any other keymaps you add.

However, when using ykpasswd with a keymap other than one compatible with
standard modhex, you must ensure that the OTP given to -o is in modhex 
(this is to ensure you enroll the key that you meant to.)

Thus, you should either temporarily switch your keyboard layout to qwerty
before running ykpasswd to enroll users, or use the provided layout conversion
script contrib/ to convert from your layout of
choice to modhex.

To add support for additional keymaps, edit utils/yk_chkpwd.c and add your
keymap(s) of choice to the KEYMAPS array.

5. Utilities


The ykpasswd utility provides administration, insert and removal of entries,
for the YubiPAM database. The required elements that need to be entered into
the database include the public UID (fixed modhex portion of an OTP), the AES
key which can be used to decrypt the token, and the private UID which is found
after successful decryption of a valid OTP.

If you have apriori knowledge of these values for user joesmith you can enter
them straight into the command line, using:

# ykpasswd -a -k AESKEY -f PUBLICKEY -p PRIVATEKEY -u joesmith

Or alteratnively you can just enter the minimum and be prompted to enter the 
information using:

# ykpasswd -a -u joesmith

If you don't have the private UID it requires you to decrypt a valid token to
get the value. Fortunately you can provide a valid OTP and the appropriate AES
key and let ykpasswd determine the public and private UIDs for you, using:

# ykpasswd -a -u joesmith -k AESKEY -o OTP

The "-u" option is mandatory and should always be defined.


Once a Yubikey has been successfully added to the YubiPAM database, it can be
tested using the ykvalidate tool. Simply pass an OTP associated with the
calling user or specify the actual user and it will confirm if it's VALID or

# ykvalidate OTP

# ykvalidate -u joesmith OTP

6. Troubleshooting

In the event that the YubiPAM module is not working it may pay to enable debug
mode in order to sort out any issues. To enable debug mode just add the
PAM module parameter "debug" to your PAM entry:

  auth sufficient debug

Note: On production systems, debug should NOT be turned on due to its verbosity
and subsequent disclosure of information.


YubiPAM is a module for PAM that provides support for One Time Passwords (OTP) authentication.







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