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PAM_PWQUALITY(8)                               System Manager's 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-check‐
       ing 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 dictio‐
       nary 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 strength checks works in the following manner: at first the Cracklib routine is called  to  check  if  the
       password  is part of a dictionary; if this is not the case an additional set of strength checks is done. These
       checks 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. This defaults to 5 changes.

       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
           Optional check whether the password contains the user's name in some form.

       These checks are configurable either by use of the module arguments or by modifying the  /etc/security/pwqual‐
       ity.conf configuration file.

OPTIONS
       debug
           This  option  makes  the module write information to syslog(3) indicating the behavior of the module (this
           password.

       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 9
           . 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 1
           which is the recommended value for minlen less than 10.

           (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 letter will count +1 towards meeting the current minlen value. The
           default for ucredit is 1 which is the recommended value for minlen less than 10.

           (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 letter will count +1 towards meeting the current minlen value. The
           default for lcredit is 1 which is the recommended value for minlen less than 10.

           (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 character will count +1 towards meeting the current minlen value. The default
           for ocredit is 1 which is the recommended value for minlen less than 10.

           (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 default  number  is  zero.
           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.

       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 pass‐
           words will not pass the simplicity check unless the sequence is only a minor part of the password.

       maxclassrepeat=N

           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  pro‐
           vided by the previously stacked password module.

       dictpath=/path/to/dict
           Path to the cracklib dictionaries.


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.
           #
           passwd  password required       pam_pwquality.so retry=3
           passwd  password required       pam_unix.so use_authtok


       Another example (in the /etc/pam.d/passwd format) is for the case that you want to use  md5  password  encryp‐
       tion:

       And here is another example in case you don´t want to use credits:

           #%PAM-1.0
           #
           # 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 md5


SEE ALSO
       pwscore(1), pwquality.conf(5), pam_pwquality(8), pam.conf(5), PAM(8)


AUTHORS
       Tomas Mraz <[email protected]>
       Original author of pam_cracklib module Cristian Gafton <[email protected]>



Red Hat, Inc.                                        10 Nov 2011                                     PAM_PWQUALITY(8)