PAM_PASSWDQC(8) BSD System Manager's Manual PAM_PASSWDQC(8)NAMEpam_passwdqc — Password quality-control PAM module
SYNOPSIS
[service-name] module-type control-flag pam_passwdqc [options]
DESCRIPTION
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 ones.
The pam_passwdqc module provides functionality for only one PAM manage‐
ment 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 pass‐
word is unsatisfactory, the service function returns PAM_AUTHTOK_ERR.
The following options may be passed to the module:
min=N0,N1,N2,N3,N4
(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 char‐
acter 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 char‐
acter 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 suffi‐
cient 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 let‐
ters 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 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 pass‐
word at 8 characters.
It is important that you do set max=8 if you are using the tradi‐
tional hashes, or some weak passwords will pass the checks.
passphrase=N
(passphrase=3) The number of words required for a passphrase, or
0 to disable the support for user-chosen passphrases.
match=N
(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=permit|deny
(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 pass‐
word with the substring removed would be weak.
random=N[,only]
(random=42) The size of randomly-generated passphrases in bits
(24 to 72), 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.
enforce=none|users|everyone
(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.
non-unix
Normally, pam_passwdqc uses getpwnam(3) to obtain the user's per‐
sonal login information and use that during the password strength
checks. This behavior can be disabled with the non-unix option.
retry=N
(retry=3) The number of times the module will ask for a new pass‐
word 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, 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.
check_oldauthtok
This tells pam_passwdqc to validate the old password before giv‐
ing a new password prompt. Normally, this task is left for sub‐
sequent 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 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
ask_oldauthtok.
SEE ALSOgetpwnam(3), pam.conf(5), pam(8)AUTHORS
The pam_passwdqc module was written for Openwall GNU/*/Linux by Solar
Designer ⟨solar at openwall.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.
BSD February 12, 2008 BSD
