Provided by: libpam-passwdqc_0.7.5-1_i386
pam_passwdqc - Password quality-control PAM module
[service-name] module-type control-flag pam_passwdqc [options]
The pam_passwdqc module is a simple password strength checking module for
PAM. In addition to checking regular passwords, it offers support for
passphrases and can provide randomly generated passwords.
The pam_passwdqc module provides functionality for only one PAM
management group: password changing. In terms of the module-type
parameter, this is the “password” feature.
The pam_chauthtok() service function may ask the user for a new password,
and verify that it meets certain minimum standards. If the chosen
password is unsatisfactory, the service function returns PAM_AUTHTOK_ERR.
The following options may be passed to the module:
(min=disabled,24,12,8,7) The minimum allowed password lengths for
different kinds of passwords/passphrases. The keyword disabled
can be used to disallow passwords of a given kind regardless of
their length. Each subsequent number is required to be no larger
than the preceding one.
N0 is used for passwords consisting of characters from one
character class only. The character classes are: digits, lower-
case letters, upper-case letters, and other characters. There is
also a special class for non-ASCII characters which could not be
classified, but are assumed to be non-digits.
N1 is used for passwords consisting of characters from two
character classes, which do not meet the requirements for a
N2 is used for passphrases. A passphrase must consist of
sufficient words (see the passphrase option below).
N3 and N4 are used for passwords consisting of characters from
three and four character classes, respectively.
When calculating the number of character classes, upper-case
letters used as the first character and digits used as the last
character of a password are not counted.
In addition to being sufficiently long, passwords are required to
contain enough different characters for the character classes and
the minimum length they have been checked against.
max=N (max=40) The maximum allowed password length. This can be used
to prevent users from setting passwords which may be too long for
some system services. The value 8 is treated specially: if max
is set to 8, passwords longer than 8 characters will not be
rejected, but will be truncated to 8 characters for the strength
checks and the user will be warned. This is to be used with the
traditional DES-based password hashes, which truncate the
password at 8 characters.
It is important that you do set max=8 if you are using the
traditional hashes, or some weak passwords will pass the checks.
(passphrase=3) The number of words required for a passphrase, or
0 to disable the support for passphrases.
(match=4) The length of common substring required to conclude
that a password is at least partially based on information found
in a character string, or 0 to disable the substring search.
Note that the password will not be rejected once a weak substring
is found; it will instead be subjected to the usual strength
requirements with the weak substring removed.
The substring search is case-insensitive and is able to detect
and remove a common substring spelled backwards.
(similar=deny) Whether a new password is allowed to be similar to
the old one. The passwords are considered to be similar when
there is a sufficiently long common substring and the new
password with the substring removed would be weak.
(random=42) The size of randomly-generated passwords in bits, or
0 to disable this feature. Passwords that contain the offered
randomly-generated string will be allowed regardless of other
The only modifier can be used to disallow user-chosen passwords.
(enforce=everyone) The module can be configured to warn of weak
passwords only, but not actually enforce strong passwords. The
users setting will enforce strong passwords for invocations by
non-root users only.
Normally, pam_passwdqc uses getpwnam(3) to obtain the user’s
personal login information and use that during the password
strength checks. This behavior can be disabled with the non-unix
(retry=3) The number of times the module will ask for a new
password if the user fails to provide a sufficiently strong
password and enter it twice the first time.
Ask for the old password as well. Normally, pam_passwdqc leaves
this task for subsequent modules. With no argument, the
ask_oldauthtok option will cause pam_passwdqc to ask for the old
password during the preliminary check phase. If the
ask_oldauthtok option is specified with the update argument,
pam_passwdqc will do that during the update phase.
This tells pam_passwdqc to validate the old password before
giving a new password prompt. Normally, this task is left for
The primary use for this option is when ask_oldauthtok=update is
also specified, in which case no other module gets a chance to
ask for and validate the password. Of course, this will only
work with UNIX passwords.
Use the new password obtained by modules stacked before
pam_passwdqc. This disables user interaction within
pam_passwdqc. The only difference between use_first_pass and
use_authtok is that the former is incompatible with
getpwnam(3), pam.conf(5), pam(8)
The pam_passwdqc module was written for Openwall GNU/*/Linux by Solar
Designer 〈email@example.com〉. This manual page, derived from the
author’s documentation, was written for the FreeBSD Project by ThinkSec
AS and NAI Labs, the Security Research Division of Network Associates,
Inc. under DARPA/SPAWAR contract N66001-01-C-8035 (“CBOSS”), as part of
the DARPA CHATS research program.