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pam_passwdqc



DESCRIPTION

     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 manage-
     ment group: password changing.  In terms of the module-type parameter,
     this is the “password” feature.

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

     The following options may be passed to the module:

     min=N0,N1,N2,N3,N4
             (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 char-
             acter 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 clas-
             sified, but are assumed to be non-digits.

             N1 is used for passwords consisting of characters from two char-
             acter classes, which do not meet the requirements for a
             passphrase.

             N2 is used for passphrases.  A passphrase must consist of suffi-
             cient 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 let-
             ters 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 to be used with the
             traditional DES-based password hashes, which truncate the pass-
             word at 8 characters.

             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=permit|deny
             (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 pass-
             word with the substring removed would be weak.

     random=N[,only]
             (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=none|users|everyone
             (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 invocations by
             non-root users only.

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

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

     ask_oldauthtok[=update]
             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.

     check_oldauthtok
             This tells pam_passwdqc to validate the old password before giv-
             ing a new password prompt.  Normally, this task is left for sub-
             sequent modules.

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


AUTHORS

     The pam_passwdqc module was written for Openwall GNU/*/Linux 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.

BSD                            November 1, 2003                            BSD

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