1PAM_PASSWDQC(8) BSD System Manager's Manual PAM_PASSWDQC(8)
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4 pam_passwdqc — Password quality-control PAM module
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7 [service-name] module-type control-flag pam_passwdqc [options]
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10 The pam_passwdqc module is a simple password strength checking module for
11 PAM. In addition to checking regular passwords, it offers support for
12 passphrases and can provide randomly generated ones.
13 The pam_passwdqc module provides functionality for only one PAM manage‐
15 ment group: password changing. In terms of the module-type parameter,
16 this is the “password” feature.
17 The pam_chauthtok() service function may ask the user for a new password,
19 and verify that it meets certain minimum standards. If the chosen pass‐
20 word is unsatisfactory, the service function returns PAM_AUTHTOK_ERR.
21 The following options may be passed to the module:
23 min=N0,N1,N2,N3,N4
25 (min=disabled,24,11,8,7) The minimum allowed password lengths for
26 different kinds of passwords/passphrases. The keyword disabled
27 can be used to disallow passwords of a given kind regardless of
28 their length. Each subsequent number is required to be no larger
29 than the preceding one.
30 N0 is used for passwords consisting of characters from one char‐
32 acter class only. The character classes are: digits, lower-case
33 letters, upper-case letters, and other characters. There is also
34 a special class for non-ASCII characters, which could not be
35 classified, but are assumed to be non-digits.
36 N1 is used for passwords consisting of characters from two char‐
38 acter classes that do not meet the requirements for a passphrase.
39 N2 is used for passphrases. Note that besides meeting this
41 length requirement, a passphrase must also consist of a suffi‐
42 cient number of words (see the passphrase option below).
43 N3 and N4 are used for passwords consisting of characters from
45 three and four character classes, respectively.
46 When calculating the number of character classes, upper-case let‐
48 ters used as the first character and digits used as the last
49 character of a password are not counted.
50 In addition to being sufficiently long, passwords are required to
52 contain enough different characters for the character classes and
53 the minimum length they have been checked against.
54 Required password complexity is proportional to its length.
56 Passwords must have at least N4 characters. Passwords shorter
57 than N3 characters need to have lower case letters, upper case
58 letters, digits and symbols. Passwords shorter than N2 characters
59 must have 3 or more classes of characters. Passwords shorter
60 than N1 characters must have 2 or more classes of characters.
61 Passwords longer than N1 characters can have just one type of
62 characters in them.
63 In other words, the number of required unique characters depends
65 how long or complex the password is.
66 max=N (max=40) The maximum allowed password length. This can be used
68 to prevent users from setting passwords that may be too long for
69 some system services. The value 8 is treated specially: if max
70 is set to 8, passwords longer than 8 characters will not be
71 rejected, but will be truncated to 8 characters for the strength
72 checks and the user will be warned. This is to be used with the
73 traditional DES-based password hashes, which truncate the pass‐
74 word at 8 characters.
75 It is important that you do set max=8 if you are using the tradi‐
77 tional hashes, or some weak passwords will pass the checks.
78 passphrase=N
80 (passphrase=3) The number of words required for a passphrase, or
81 0 to disable the support for user-chosen passphrases.
82 match=N
84 (match=4) The length of common substring required to conclude
85 that a password is at least partially based on information found
86 in a character string, or 0 to disable the substring search.
87 Note that the password will not be rejected once a weak substring
88 is found; it will instead be subjected to the usual strength
89 requirements with the weak substring removed.
90 The substring search is case-insensitive and is able to detect
92 and remove a common substring spelled backwards.
93 similar=permit|deny
95 (similar=deny) Whether a new password is allowed to be similar to
96 the old one. The passwords are considered to be similar when
97 there is a sufficiently long common substring and the new pass‐
98 word with the substring removed would be weak.
99 random=N[,only]
101 (random=42) The size of randomly-generated passphrases in bits
102 (24 to 72), or 0 to disable this feature. Any passphrase that
103 contains the offered randomly-generated string will be allowed
104 regardless of other possible restrictions.
105 The only modifier can be used to disallow user-chosen passwords.
107 enforce=none|users|everyone
109 (enforce=everyone) The module can be configured to warn of weak
110 passwords only, but not actually enforce strong passwords. The
111 users setting will enforce strong passwords for invocations by
112 non-root users only.
113 non-unix
115 Normally, pam_passwdqc uses getpwnam(3) to obtain the user's per‐
116 sonal login information and use that during the password strength
117 checks. This behavior can be disabled with the non-unix option.
118 retry=N
120 (retry=3) The number of times the module will ask for a new pass‐
121 word if the user fails to provide a sufficiently strong password
122 and enter it twice the first time.
123 ask_oldauthtok[=update]
125 Ask for the old password as well. Normally, pam_passwdqc leaves
126 this task for subsequent modules. With no argument, the
127 ask_oldauthtok option will cause pam_passwdqc to ask for the old
128 password during the preliminary check phase. If the
129 ask_oldauthtok option is specified with the update argument,
130 pam_passwdqc will do that during the update phase.
131 check_oldauthtok
133 This tells pam_passwdqc to validate the old password before giv‐
134 ing a new password prompt. Normally, this task is left for sub‐
135 sequent modules.
136 The primary use for this option is when ask_oldauthtok=update is
138 also specified, in which case no other module gets a chance to
139 ask for and validate the password. Of course, this will only
140 work with UNIX passwords.
141 disable_firstupper_lastdigit_check
143 This tells pam_passwdqc to include upper-case letters used as the
144 first character and digits used as the last character of a pass‐
145 word when calculating the number of character classes.
146 use_first_pass, use_authtok
148 Use the new password obtained by modules stacked before
149 pam_passwdqc. This disables user interaction within
150 pam_passwdqc. The only difference between use_first_pass and
151 use_authtok is that the former is incompatible with
152 ask_oldauthtok.
153 oldpass_prompt_file, newpass_prompt_file = absolute-file-path
155 These can be used to override prompts while requesting old pass‐
156 word and new password, respectively. The maximum size of the
157 prompt files can be 4096 characters at present. If the file size
158 is more than 4096 characters, the output will be truncated to
159 4096 characters.
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162 getpwnam(3), pam.conf(5), pam(8)
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165 The pam_passwdqc module was written for Openwall GNU/*/Linux by Solar
166 Designer <solar at openwall.com>. This manual page, derived from the
167 author's documentation, was written for the FreeBSD Project by ThinkSec
168 AS and NAI Labs, the Security Research Division of Network Associates,
169 Inc. under DARPA/SPAWAR contract N66001-01-C-8035 (“CBOSS”), as part of
170 the DARPA CHATS research program.
171BSD February 12, 2008 BSD