Ubuntu Manpage: passwdqc.conf — libpasswdqc configuration file

NAME

       passwdqc.conf — libpasswdqc configuration file

DESCRIPTION

       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.

FORMAT

       A passwdqc.conf file consists of 0 or more lines of the following format:
             option=value

       Empty lines and lines beginning with “#” are ignored.  Whitespace characters between the option, “=”, and
       value are not allowed.

DIRECTIVE OPTIONS

       config=FILE
               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

min=N0,N1,N2,N3,N4
(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 passphrase.

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=72) 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.

passphrase=N
(default: passphrase=3) The number of words required for a passphrase, or 0 to disable the
support for user-chosen passphrases.

match=N
(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
discounted.

The substring search is case-insensitive and is able to detect and remove a common substring
spelled backwards.

similar=permit|deny
(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 weak.

wordlist=FILE
Deny passwords that are based on lines of the tiny external text FILE, which can reasonably be
e.g. a list of a few thousand common passwords. Common dictionary words may also reasonably be
included, especially in a local language other than English, or longer yet common English words.
(passwdqc includes a list of a few thousand common English words of lengths from 3 to 6 built in.
Any word list possibly specified with this option is used in addition to the built-in word list.)

Substring matching and discounting will be used if the match setting above is non-zero. Please
note that this is very inefficient, and isn't to be used with large wordlists.

denylist=FILE
Deny passwords or passphrases directly appearing in the tiny external text FILE. That file can
reasonably be e.g. a list of common passwords if only a relaxed policy is desired and stricter
checks are thus disabled (using their separate options). Such policy would only be somewhat
effective against online/remote attacks, but not against offline attacks on hashed passwords.

filter=FILE
Deny passwords or passphrases directly appearing in a maybe huge binary filter FILE created with
pwqfilter. This is very efficient, needing at most two random disk reads per query. A filter
created from millions of leaked passwords can reasonably be used on top of passwdqc's other
checks to further reduce the number of passing yet weak passwords without causing unreasonable
inconvenience (as e.g. higher minimum lengths and character set requirements could).

random=N[,only]
(default: random=47) The size of randomly-generated passphrases in bits (24 to 136), 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

enforce=none|users|everyone
(default: enforce=everyone) The PAM module can be configured to warn of weak passwords only, but
not actually enforce strong passwords. The users setting is like everyone for all PAM services
except chpasswd and passwd. For these two PAM services users will enforce strong passwords for
invocations by non-root users only.

non-unix
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
option.

retry=N
(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_oldauthtok[=update]
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.

check_oldauthtok
This tells the PAM module to validate the old password before giving a new password prompt.
Normally, this task is left for subsequent modules.

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_first_pass, use_authtok
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 ask_oldauthtok.

noaudit
If audit is enabled at build time, the PAM module logs audit events once user tries to change
their credentials. This option disables that audit logging.

FILES

       /etc/passwdqc.conf  (not  read  unless   this   suggested   file   location   is   specified   with   the
       config=/etc/passwdqc.conf option).

AUTHORS

       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.

Openwall Project                                 March 10, 2021                                 PASSWDQC.CONF(5)