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1. YubiPAM Introduction
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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.


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2. Status
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  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.


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3. Build
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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


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

  auth sufficient pam_yubikey.so

and ensure pam_yubikey.so is located in /lib/security/

Supported PAM module parameters are:

  "debug": enable debug.
  "verbose_otp": enable echoing of the OTP, after all it's only a one time pad.
  "include_users": enable yubikey auth for users in the given file. Eash line
                   can contain one user.
                   Ex: include_users=/etc/yubikey.users
  "exclude_users": disable yubikey auth for users in the given file. Eash line
                   can contain one user.
                   Ex: exclude_users=/etc/yubikey.users
  "passcode_only": 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.

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5. Utilities
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ykpasswd

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.


ykvalidate

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
NOT.

# ykvalidate OTP

# ykvalidate -u joesmith OTP


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6. Troubleshooting
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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 pam_yubikey.so debug

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