passwdqc.conf - libpasswdqc configuration file
libpasswdqc is a simple password strength checking library. In addition
to checking regular passwords, it offers support for passphrases and can
provide randomly generated ones. A passwdqc.conf configuration file may
be used to override default libpasswdqc settings.
A passwdqc.conf file consists of 0 or more lines of the following format:
Empty lines and lines beginning with “#” are ignored. Whitespace
characters between the option, “=”, and value are not allowed.
Load the specified configuration FILE in the passwdqc.conf
format. This file may define any options described in this
manual, including load of yet another configuration file, but
loops are not allowed.
PASSWORD QUALITY CONTROL OPTIONS
(default: min=disabled,24,11,8,7) 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 that do not meet the requirements for a
N2 is used for passphrases. Note that besides meeting this
length requirement, a passphrase must also consist of a
sufficient number of 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 (default: max=40) The maximum allowed password length. This can
be used to prevent users from setting passwords that 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.
(default: passphrase=3) The number of words required for a
passphrase, or 0 to disable the support for user-chosen
(default: 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 partially
The substring search is case-insensitive and is able to detect
and remove a common substring spelled backwards.
(default: 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 partially discounted would be
(default: random=47) The size of randomly-generated passphrases
in bits (26 to 81), or 0 to disable this feature. Any passphrase
that contains the offered randomly-generated string will be
allowed regardless of other possible restrictions.
The only modifier can be used to disallow user-chosen passwords.
PAM MODULE OPTIONS
(default: enforce=everyone) The PAM 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, the PAM module 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
(default: retry=3) The number of times the PAM 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, the PAM module
leaves this task for subsequent modules. With no argument, the
ask_oldauthtok option will cause the PAM module to ask for the
old password during the preliminary check phase. If the
ask_oldauthtok option is specified with the update argument, the
PAM module will do that during the update phase.
This tells the PAM module 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 other modules stacked before the
PAM module. This disables user interaction within the PAM
module. The only difference between use_first_pass and
use_authtok is that the former is incompatible with
The pam_passwdqc module was written for Openwall GNU/*/Linux by Solar
Designer 〈solar at openwall.com〉. This manual page was derived from
pam_passwdqc(8). The latter, 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.