pam_pwquality(category5-qmail.html) - phpMan

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-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 strength checks works in the following manner: at first the  Crack-
       lib 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/pwquality.conf configuration file.
OPTIONS
       debug
           This option makes the module write information to  syslog(3)  indi-
           cating the behavior of the module (this option does not write pass-
           word 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  5  for  the  number  of
           changes in the new password from the old password.
       minlen=N
           The minimum acceptable size for the new password (plus one if cred-
           its are not disabled which is the default). In addition to the num-
           ber  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  dictio-
           nary  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 charac-
           ters.  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  char-
           acters from the passwd GECOS field of the user are contained in the
           new password.  The default is 0 which means that this check is dis-
           abled.
       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  pass-
           word.   By default the list is empty which means that this check is
           disabled.
       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.
       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 encryption:
           #%PAM-1.0
           #
           # These lines allow a md5 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 md5

       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 <tmraz AT redhat.com>
       Original author of pam_cracklib module Cristian Gafton <gafton AT redhat.com>

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