pwqcheck —
Check
passphrase quality
The
pwqcheck program checks passphrase quality
using the libpasswdqc library. By default, it expects to read 3 lines from
standard input:
- first line is a new password,
- second line is an old password, and
- third line is either an existing account name or a
passwd(5) entry.
There are a number of supported options, which can be used to control the
pwqcheck behavior.
pwqcheck prints
OK
on success. Scripts invoking
pwqcheck are
suggested to check for both a zero exit status and the
OK line.
-
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.
-
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).
-
config=FILE
- Load config FILE in the
passwdqc.conf format. This file may define
any options described in passwdqc.conf(5),
but only the min,
max, passphrase,
match, and
config options are honored by
pwqcheck.
- -1
- Read just 1 line (new passphrase). This is needed to use
pwqcheck as the passwordcheck program on
OpenBSD - e.g., with ":passwordcheck=/usr/bin/pwqcheck -1:\"
(without the quotes, but with the trailing backslash) in the
"default" section in
/etc/login.conf.
- -2
- Read just 2 lines (new and old passphrases).
- --multi
- Check multiple passphrases (until EOF). This option may be
used on its own or along with the -1 or
-2 options.
pwqcheck will read 1, 2, or 3 lines and will
output one line per passphrase to check. The lines will start with either
OK or a message explaining why the
passphrase did not pass the checks, followed by a colon and a space, and
finally followed by the passphrase. The explanatory message is guaranteed
to not include a colon. With this option, the exit status of
pwqcheck depends solely on whether there were
any errors preventing the strength of passphrases from being fully checked
or not. A primary use for this option is to test different policies and/or
different versions of passwdqc on large passphrase lists.
- --version
- Output pwqcheck program
version and exit.
-
-h,
--help
- Output pwqcheck help text and
exit.
pwqcheck exits with non-zero status when it
encounters invalid config file, invalid option, invalid parameter value,
invalid data in standard input, and in any case when it fails to check
passphrase strength. Without the
--multi option,
pwqcheck also exits with non-zero status when it
detects a weak passphrase.
/etc/passwdqc.conf (not read unless this suggested
file location is specified with the
config=/etc/passwdqc.conf option).
pwqgen(1),
libpasswdqc(3),
passwd(5),
passwdqc.conf(5),
pam_passwdqc(8).
https://www.openwall.com/passwdqc/
The pam_passwdqc module was written for Openwall GNU/*/Linux by Solar Designer.
The
pwqcheck program was originally written for
ALT GNU/*/Linux by Dmitry V. Levin, indirectly reusing code from pam_passwdqc
(via libpasswdqc). This manual page (derived from the pam_passwdqc
documentation) was written for Openwall GNU/*/Linux by Dmitry V. Levin.