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



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