NAME¶

pam_otpw - verify one-time passwords

SYNOPSIS¶

pam_otpw [ arguments ]

DESCRIPTION¶

OTPW is a one-time password authentication system. It compares entered passwords with hash values stored in the user's home directory in the file ~/.otpw. Once a password was entered correctly, its hash value in ~/.otpw will be overwritten with hyphens, which disables its use in future authentication. A lock file ~/.otpw.lock prevents that the same password challenge is issued on several concurrent authentication sessions. This helps to prevent an eavesdropper from copying a one-time password as it is entered instantly into a second session, in the hope to get access by sending the final newline character faster than the user could.

Both an authentication management and a session management function are offered by this module. The authentication function asks for and verifies one-time passwords. The session function prints a message after login that reminds the user of the remaining number of one-time passwords.

ARGUMENTS¶

debug

Turn on debugging via syslog(3).

nolock

Disable locking. This option tells the authentication function of pam_otpw.so to ignore any existing ~/.otpw.lock lock file and not to generate any. With this option, pam_otpw.so will never ask for several passwords simultaneously.

PSEUDO-USER INSTALLATION¶

If a system pseudo user “otpw” exists in the user database (with UID < 1000), then the password hash files will not be stored in the user's home directory. Instead of looking for ~john/.otpw.lock the file has to be located in the home directory of the pseudo user “otpw”, and be named after the user (e.g. “/var/lib/otpw/john”). It will be accessed with the effective UID and GID of that pseudo user.

AUTHOR¶

The OTPW package, which includes the otpw-gen program, has been developed by Markus Kuhn. The most recent version is available from <http://www.cl.cam.ac.uk/~mgk25/otpw.html>.

SEE ALSO¶

otpw-gen(1), pam(8)