1.\" Copyright (c) 2000-2002 Solar Designer.
2.\" All rights reserved.
3.\" Copyright (c) 2001 Networks Associates Technology, Inc.
4.\" All rights reserved.
5.\"
6.\" Portions of this software were developed for the FreeBSD Project by
7.\" ThinkSec AS and NAI Labs, the Security Research Division of Network
8.\" Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
9.\" ("CBOSS"), as part of the DARPA CHATS research program.
10.\"
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35.\" $FreeBSD$
36.\"
37.Dd April 15, 2002
38.Dt PAM_PASSWDQC 8
39.Os
40.Sh NAME
41.Nm pam_passwdqc
42.Nd Password quality-control PAM module
43.Sh SYNOPSIS
44.Op Ar service-name
45.Ar module-type
46.Ar control-flag
47.Pa pam_passwdqc
48.Op Ar options
49.Sh DESCRIPTION
50The
51.Nm
52module is a simple password strength checking module for
53PAM.
54In addition to checking regular passwords, it offers support for
55passphrases and can provide randomly generated passwords.
56.Pp
57The
58.Nm
59module provides functionality for only one PAM category:
60password changing.
61In terms of the
62.Ar module-type
63parameter, this is the
64.Dq Li password
65feature.
66.Pp
67The
68.Fn pam_chauthtok
69service function will ask the user for a new password, and verify that
70it meets certain minimum standards.
71If the chosen password is unsatisfactory, the service function returns
72.Dv PAM_AUTHTOK_ERR .
73.Pp
74The following options may be passed to the authentication module:
75.Bl -tag -width indent
76.It Xo
77.Sm off
78.Cm min No = Ar N0 , N1 , N2 , N3 , N4
79.Sm on
80.Xc
81.Sm off
82.Pq Cm min No = Cm disabled , No 24 , 12 , 8 , 7
83.Sm on
84The minimum allowed password lengths for different kinds of
85passwords/passphrases.
86The keyword
87.Cm disabled
88can be used to
89disallow passwords of a given kind regardless of their length.
90Each subsequent number is required to be no larger than the preceding
91one.
92.Pp
93.Ar N0
94is used for passwords consisting of characters from one character
95class only.
96The character classes are: digits, lower-case letters, upper-case
97letters, and other characters.
98There is also a special class for
99.No non- Ns Tn ASCII
100characters which could not
101be classified, but are assumed to be non-digits.
102.Pp
103.Ar N1
104is used for passwords consisting of characters from two character
105classes, which do not meet the requirements for a passphrase.
106.Pp
107.Ar N2
108is used for passphrases.
109A passphrase must consist of sufficient words (see the
110.Cm passphrase
111option below).
112.Pp
113.Ar N3
114and
115.Ar N4
116are used for passwords consisting of characters from three
117and four character classes, respectively.
118.Pp
119When calculating the number of character classes, upper-case letters
120used as the first character and digits used as the last character of a
121password are not counted.
122.Pp
123In addition to being sufficiently long, passwords are required to
124contain enough different characters for the character classes and
125the minimum length they have been checked against.
126.It Cm max Ns = Ns Ar N
127.Pq Cm max Ns = Ns 40
128The maximum allowed password length.
129This can be used to prevent users from setting passwords which may be
130too long for some system services.
131The value 8 is treated specially: if
132.Cm max
133is set to 8, passwords longer than 8 characters will not be rejected,
134but will be truncated to 8 characters for the strength checks and the
135user will be warned.
136This is for compatibility with the traditional DES password hashes,
137which truncate the password at 8 characters.
138.Pp
139It is important that you do set
140.Cm max Ns = Ns 8
141if you are using the traditional
142hashes, or some weak passwords will pass the checks.
143.It Cm passphrase Ns = Ns Ar N
144.Pq Cm passphrase Ns = Ns 3
145The number of words required for a passphrase, or 0 to disable
146passphrase support.
147.It Cm match Ns = Ns Ar N
148.Pq Cm match Ns = Ns 4
149The length of common substring required to conclude that a password is
150at least partially based on information found in a character string,
151or 0 to disable the substring search.
152Note that the password will not be rejected once a weak substring is
153found; it will instead be subjected to the usual strength requirements
154with the weak substring removed.
155.Pp
156The substring search is case-insensitive and is able to detect and
157remove a common substring spelled backwards.
158.It Xo
159.Sm off
160.Cm similar No = Cm permit | deny
161.Sm on
162.Xc
163.Pq Cm similar Ns = Ns Cm deny
164Whether a new password is allowed to be similar to the old one.
165The passwords are considered to be similar when there is a sufficiently
166long common substring and the new password with the substring removed
167would be weak.
168.It Xo
169.Sm off
170.Cm random No = Ar N Op , Cm only
171.Sm on
172.Xc
173.Pq Cm random Ns = Ns 42
174The size of randomly-generated passwords in bits, or 0 to disable this
175feature.
176Passwords that contain the offered randomly-generated string will be
177allowed regardless of other possible restrictions.
178.Pp
179The
180.Cm only
181modifier can be used to disallow user-chosen passwords.
182.It Xo
183.Sm off
184.Cm enforce No = Cm none | users | everyone
185.Sm on
186.Xc
187.Pq Cm enforce Ns = Ns Cm everyone
188The module can be configured to warn of weak passwords only, but not
189actually enforce strong passwords.
190The
191.Cm users
192setting will enforce strong passwords for non-root users only.
193.It Cm non-unix
194Normally,
195.Nm
196uses
197.Xr getpwnam 3
198to obtain the user's personal login information and use that during
199the password strength checks.
200This behavior can be disabled with the
201.Cm non-unix
202option.
203.It Cm retry Ns = Ns Ar N
204.Pq Cm retry Ns = Ns 3
205The number of times the module will ask for a new password if the user
206fails to provide a sufficiently strong password and enter it twice the
207first time.
208.It Cm ask_oldauthtok Ns Op = Ns Cm update
209Ask for the old password as well.
210Normally,
211.Nm
212leaves this task for subsequent modules.
213With no argument, the
214.Cm ask_oldauthtok
215option will cause
216.Nm
217to ask for the old password during the preliminary check phase.
218If the
219.Cm ask_oldauthtok
220option is specified with the
221.Cm update
222argument,
223.Nm
224will do that during the update phase.
225.It Cm check_oldauthtok
226This tells
227.Nm
228to validate the old password before giving a
229new password prompt.
230Normally, this task is left for subsequent modules.
231.Pp
232The primary use for this option is when
233.Cm ask_oldauthtok Ns = Ns Cm update
234is also specified, in which case no other modules gets a chance to ask
235for and validate the password.
236Of course, this will only work with
237.Ux
238passwords.
239.It Cm use_first_pass , use_authtok
240Use the new password obtained by modules stacked before
241.Nm .
242This disables user interaction within
243.Nm .
244The only difference between
245.Cm use_first_pass
246and
247.Cm use_authtok
248is that the former is incompatible with
249.Cm ask_oldauthtok .
250.El
251.Sh SEE ALSO
252.Xr getpwnam 3 ,
253.Xr pam.conf 5 ,
254.Xr pam 3
255.Sh AUTHORS
256The
257.Nm
258module was written by
259.An Solar Designer Aq Mt solar@openwall.com .
260This manual page, derived from the author's documentation, was written
261for the
262.Fx
263Project by
264ThinkSec AS and NAI Labs, the Security Research Division of Network
265Associates, Inc.\& under DARPA/SPAWAR contract N66001-01-C-8035
266.Pq Dq CBOSS ,
267as part of the DARPA CHATS research program.
268