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PAM_PWQUALITY(8)               Linux-PAM Manual               PAM_PWQUALITY(8)
NAME
       pam_pwquality - PAM module to perform password quality checking
SYNOPSIS
       pam_pwquality.so [...]
DESCRIPTION
       This module can be plugged into the password stack of a given service
       to provide some plug-in strength-checking for passwords.  The code was
       originally based on pam_cracklib module and the module is backwards
       compatible with its options.
       The action of this module is to prompt the user for a password and
       check its strength against a system dictionary and a set of rules for
       identifying poor choices.
       The first action is to prompt for a single password, check its strength
       and then, if it is considered strong, prompt for the password a second
       time (to verify that it was typed correctly on the first occasion). All
       being well, the password is passed on to subsequent modules to be
       installed as the new authentication token.
       The checks for strength are:
       Palindrome
           Is the new password a palindrome?
       Case Change Only
           Is the new password the the old one with only a change of case?
       Similar
           Is the new password too much like the old one? This is primarily
           controlled by one argument, difok which is a number of character
           changes (inserts, removals, or replacements) between the old and
           new password that are enough to accept the new password.
       Simple
           Is the new password too small? This is controlled by 6 arguments
           minlen, maxclassrepeat, dcredit, ucredit, lcredit, and ocredit. See
           the section on the arguments for the details of how these work and
           there defaults.
       Rotated
           Is the new password a rotated version of the old password?
       Same consecutive characters
           Optional check for same consecutive characters.
       Too long monotonic character sequence
           Optional check for too long monotonic character sequence.
       Contains user name
           Check whether the password contains the user's name in some form.
       Dictionary check
           The Cracklib routine is called to check if the password is part of
           a dictionary.
       These checks are configurable either by use of the module arguments or
       by modifying the /etc/security/pwquality.conf configuration file. The
       module arguments override the settings in the configuration file.
OPTIONS
       debug
           This option makes the module write information to syslog(3)
           indicating the behavior of the module (this option does not write
           password information to the log file).
       authtok_type=XXX
           The default action is for the module to use the following prompts
           when requesting passwords: "New UNIX password: " and "Retype UNIX
           password: ". The example word UNIX can be replaced with this
           option, by default it is empty.
       retry=N
           Prompt user at most N times before returning with error. The
           default is 1.
       difok=N
           This argument will change the default of 1 for the number of
           changes in the new password from the old password.
           The special value of 0 disables all checks of similarity of the new
           password with the old password except the new password being
           exactly the same as the old one.
       minlen=N
           The minimum acceptable size for the new password (plus one if
           credits are not disabled which is the default). In addition to the
           number of characters in the new password, credit (of +1 in length)
           is given for each different kind of character (other, upper, lower
           and digit). The default for this parameter is 8. Note that there is
           a pair of length limits also in Cracklib, which is used for
           dictionary checking, a "way too short" limit of 4 which is hard
           coded in and a build time defined limit (6) that will be checked
           without reference to minlen.
       dcredit=N
           (N >= 0) This is the maximum credit for having digits in the new
           password.  If you have less than or N digits, each digit will count
           +1 towards meeting the current minlen value. The default for
           dcredit is 0 which means there is no bonus for digits in password.
           (N < 0) This is the minimum number of digits that must be met for a
           new password.
       ucredit=N
           (N >= 0) This is the maximum credit for having upper case letters
           in the new password.  If you have less than or N upper case
           letters, each upper case letter will count +1 towards meeting the
           current minlen value. The default for ucredit is 0 which means
           there is no bonus for upper case letters in password.
           (N < 0) This is the minimum number of upper case letters that must
           be met for a new password.
       lcredit=N
           (N >= 0) This is the maximum credit for having lower case letters
           in the new password.  If you have less than or N lower case
           letters, each lower case letter will count +1 towards meeting the
           current minlen value. The default for lcredit is 0 which means
           there is no bonus for lower case letters in password.
           (N < 0) This is the minimum number of lower case letters that must
           be met for a new password.
       ocredit=N
           (N >= 0) This is the maximum credit for having other characters in
           the new password.  If you have less than or N other characters,
           each other character will count +1 towards meeting the current
           minlen value. The default for ocredit is 0 which means there is no
           bonus for other characters in password.
           (N < 0) This is the minimum number of other characters that must be
           met for a new password.
       minclass=N
           The minimum number of required classes of characters for the new
           password.  The four classes are digits, upper and lower letters and
           other characters.  The difference to the credit check is that a
           specific class if of characters is not required. Instead N out of
           four of the classes are required. By default the check is disabled.
       maxrepeat=N
           Reject passwords which contain more than N same consecutive
           characters.  The default is 0 which means that this check is
           disabled.
       maxsequence=N
           Reject passwords which contain monotonic character sequences longer
           than N.  The default is 0 which means that this check is disabled.
           Examples of such sequence are '12345' or 'fedcb'. Note that most
           such passwords will not pass the simplicity check unless the
           sequence is only a minor part of the password.
       maxclassrepeat=N
           Reject passwords which contain more than N consecutive characters
           of the same class. The default is 0 which means that this check is
           disabled.
       gecoscheck=N
           If nonzero, check whether the individual words longer than 3
           characters from the passwd(5) GECOS field of the user are contained
           in the new password. The default is 0 which means that this check
           is disabled.
       dictcheck=N
           If nonzero, check whether the password (with possible
           modifications) matches a word in a dictionary. Currently the
           dictionary check is performed using the cracklib library. The
           default is 1 which means that this check is enabled.
       usercheck=N
           If nonzero, check whether the password (with possible
           modifications) contains the user name in some form. The default is
           1 which means that this check is enabled. It is not performed for
           user names shorter than 3 characters.
       usersubstr=N
           If greater than 3 (due to the minimum length in usercheck), check
           whether the password contains a substring of at least N length in
           some form.  The default is 0, which means this check is disabled.
       enforcing=N
           If nonzero, reject the password if it fails the checks, otherwise
           only print the warning. The default is 1 which means that the weak
           password is rejected (for non-root users).
       badwords=<list of words>
           The words more than 3 characters long from this space separated
           list are individually searched for and forbidden in the new
           password.  By default the list is empty which means that this check
           is disabled.
       dictpath=/path/to/dict
           This options allows for specification of non-default path to the
           cracklib dictionaries.
       enforce_for_root
           The module will return error on failed check even if the user
           changing the password is root. This option is off by default which
           means that just the message about the failed check is printed but
           root can change the password anyway. Note that root is not asked
           for an old password so the checks that compare the old and new
           password are not performed.
       local_users_only
           The module will not test the password quality for users that are
           not present in the /etc/passwd file. The module still asks for the
           password so the following modules in the stack can use the
           use_authtok option.  This option is off by default.
       use_authtok
           This argument is used to force the module to not prompt the user
           for a new password but use the one provided by the previously
           stacked password module.
MODULE TYPES PROVIDED
       Only the password module type is provided.
RETURN VALUES
       PAM_SUCCESS
           The new password passes all checks.
       PAM_AUTHTOK_ERR
           No new password was entered, the username could not be determined
           or the new password fails the strength checks.
       PAM_AUTHTOK_RECOVERY_ERR
           The old password was not supplied by a previous stacked module or
           got not requested from the user. The first error can happen if
           use_authtok is specified.
       PAM_SERVICE_ERR
           A internal error occurred.
EXAMPLES
       For an example of the use of this module, we show how it may be stacked
       with the password component of pam_unix(8).
        #
        # These lines stack two password type modules. In this example the
        # user is given 3 opportunities to enter a strong password. The
        # "use_authtok" argument ensures that the pam_unix module does not
        # prompt for a password, but instead uses the one provided by
        # pam_pwquality.
        #
        password required pam_pwquality.so retry=3
        password required pam_unix.so use_authtok
       Another example is for the case that you want to use sha256 password
       encryption:
        #
        # These lines allow modern systems to support passwords of at least 14
        # bytes with extra credit of 2 for digits and 2 for others the new
        # password must have at least three bytes that are not present in the
        # old password
        #
        password required pam_pwquality.so \
                      difok=3 minlen=15 dcredit=2 ocredit=2
        password required pam_unix.so use_authtok nullok sha256
       And here is another example in case you don't want to use credits:
        #
        # These lines require the user to select a password with a minimum
        # length of 8 and with at least 1 digit number, 1 upper case letter,
        # and 1 other character
        #
        password required pam_pwquality.so \
                      dcredit=-1 ucredit=-1 ocredit=-1 lcredit=0 minlen=8
        password required pam_unix.so use_authtok nullok sha256
SEE ALSO
       pwscore(1), pwquality.conf(5), pam_pwquality(8), pam.conf(5), PAM(8)
AUTHORS
       Tomas Mraz <tmraz AT redhat.com>
       Original author of pam_cracklib module Cristian Gafton
       <gafton AT redhat.com>
Red Hat, Inc.                     2020-08-03                  PAM_PWQUALITY(8)