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NAME    [Toc]    [Back]

     pam_passwdqc -- Password quality-control PAM module

SYNOPSIS    [Toc]    [Back]

     [service-name] module-type control-flag pam_passwdqc [options]

DESCRIPTION    [Toc]    [Back]

     The pam_passwdqc module is a simple password strength checking module for
     PAM.  In addition to checking regular passwords, it offers support for
     passphrases and can provide randomly generated passwords.

     The pam_passwdqc module provides functionality for only one PAM category:
     password changing.  In terms of the module-type parameter, this is the
     ``password'' feature.

     The pam_chauthtok() service function will ask the user for a new password,
 and verify that it meets certain minimum standards.  If the chosen
     password is unsatisfactory, the service function returns PAM_AUTHTOK_ERR.

     The following options may be passed to the authentication module:

             (min=disabled,24,12,8,7) 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, which do not meet the requirements for a

             N2 is used for passphrases.  A passphrase must consist of sufficient
 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   (max=40) The maximum allowed password length.  This can be used
             to prevent users from setting passwords which 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 for compatibility
             with the traditional DES 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=3) The number of words required for a passphrase, or
             0 to disable passphrase support.

             (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 removed.

             The substring search is case-insensitive and is able to detect
             and remove a common substring spelled backwards.

             (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 removed would be weak.

             (random=42) The size of randomly-generated passwords in bits, or
             0 to disable this feature.  Passwords that contain the offered
             randomly-generated string will be allowed regardless of other
             possible restrictions.

             The only modifier can be used to disallow user-chosen passwords.

             (enforce=everyone) The module can be configured to warn of weak
             passwords only, but not actually enforce strong passwords.  The
             users setting will enforce strong passwords for non-root users

             Normally, pam_passwdqc uses getpwnam(3) to obtain the user's personal
 login information and use that during the password strength
             checks.  This behavior can be disabled with the non-unix option.

             (retry=3) The number of times the module will ask for a new password
 if the user fails to provide a sufficiently strong password
             and enter it twice the first time.

             Ask for the old password as well.  Normally, pam_passwdqc leaves
             this task for subsequent modules.  With no argument, the
             ask_oldauthtok option will cause pam_passwdqc to ask for the old
             password during the preliminary check phase.  If the
             ask_oldauthtok option is specified with the update argument,
             pam_passwdqc will do that during the update phase.

             This tells pam_passwdqc to validate the old password before giving
 a new password prompt.  Normally, this task is left for subsequent

             The primary use for this option is when ask_oldauthtok=update is
             also specified, in which case no other modules gets a chance to
             ask for and validate the password.  Of course, this will only
             work with UNIX passwords.

     use_first_pass, use_authtok
             Use the new password obtained by modules stacked before
             pam_passwdqc.  This disables user interaction within
             pam_passwdqc.  The only difference between use_first_pass and
             use_authtok is that the former is incompatible with

SEE ALSO    [Toc]    [Back]

     getpwnam(3), pam.conf(5), pam(8)

AUTHORS    [Toc]    [Back]

     The pam_passwdqc module was written by Solar Designer
     <solar@openwall.com>.  This manual page, derived from the author's documentation,
 was written for the FreeBSD Project by ThinkSec AS and NAI
     Labs, the Security Research Division of Network Associates, Inc. under
     DARPA/SPAWAR contract N66001-01-C-8035 (``CBOSS''), as part of the DARPA
     CHATS research program.

FreeBSD 5.2.1                   April 15, 2002                   FreeBSD 5.2.1
[ Back ]
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