1pam_passwdqc is a simple password strength checking module for 2PAM-aware password changing programs, such as passwd(1). In addition 3to checking regular passwords, it offers support for passphrases and 4can provide randomly generated ones. All features are optional and 5can be (re-)configured without rebuilding. 6 7This module should be stacked before your usual password changing 8module (such as pam_unix or pam_pwdb) in the password management group 9(the "password" lines in /etc/pam.d/passwd or /etc/pam.conf). The 10password changing module should then be told to use the provided new 11authentication token (new password) rather than request it from the 12user. There's usually the "use_authtok" option to do that. If your 13password changing module lacks the "use_authtok" option or its prompts 14are inconsistent with pam_passwdqc's, you may tell pam_passwdqc to ask 15for the old password as well, with "ask_oldauthtok". In that case the 16option to use with the password changing module is "use_first_pass". 17 18There's a number of supported options which can be used to modify the 19behavior of pam_passwdqc (defaults are given in square brackets): 20 21 min=N0,N1,N2,N3,N4 [min=disabled,24,11,8,7] 22 23The minimum allowed password lengths for different kinds of passwords 24and passphrases. The keyword "disabled" can be used to disallow 25passwords of a given kind regardless of their length. Each subsequent 26number is required to be no larger than the preceding one. 27 28N0 is used for passwords consisting of characters from one character 29class only. The character classes are: digits, lower-case letters, 30upper-case letters, and other characters. There is also a special 31class for non-ASCII characters, which could not be classified, but are 32assumed to be non-digits. 33 34N1 is used for passwords consisting of characters from two character 35classes that do not meet the requirements for a passphrase. 36 37N2 is used for passphrases. Note that besides meeting this length 38requirement, a passphrase must also consist of a sufficient number of 39words (see the "passphrase" option below). 40 41N3 and N4 are used for passwords consisting of characters from three 42and four character classes, respectively. 43 44When calculating the number of character classes, upper-case letters 45used as the first character and digits used as the last character of a 46password are not counted. 47 48In addition to being sufficiently long, passwords are required to 49contain enough different characters for the character classes and 50the minimum length they have been checked against. 51 52 max=N [max=40] 53 54The maximum allowed password length. This can be used to prevent 55users from setting passwords that may be too long for some system 56services. 57 58The value 8 is treated specially: with max=8, passwords longer than 8 59characters will not be rejected, but will be truncated to 8 characters 60for the strength checks and the user will be warned. This is to be 61used with the traditional DES-based password hashes, which truncate 62the password at 8 characters. 63 64It is important that you do set max=8 if you are using the traditional 65hashes, or some weak passwords will pass the checks. 66 67 passphrase=N [passphrase=3] 68 69The number of words required for a passphrase, or 0 to disable the 70support for user-chosen passphrases. 71 72 match=N [match=4] 73 74The length of common substring required to conclude that a password is 75at least partially based on information found in a character string, 76or 0 to disable the substring search. Note that the password will not 77be rejected once a weak substring is found; it will instead be 78subjected to the usual strength requirements with the weak substring 79removed. 80 81The substring search is case-insensitive and is able to detect and 82remove a common substring spelled backwards. 83 84 similar=permit|deny [similar=deny] 85 86Whether a new password is allowed to be similar to the old one. The 87passwords are considered to be similar when there is a sufficiently 88long common substring and the new password with the substring removed 89would be weak. 90 91 random=N[,only] [random=42] 92 93The size of randomly-generated passphrases in bits (24 to 72), or 0 to 94disable this feature. Any passphrase that contains the offered 95randomly-generated string will be allowed regardless of other possible 96restrictions. 97 98The "only" modifier can be used to disallow user-chosen passwords. 99 100 enforce=none|users|everyone [enforce=everyone] 101 102The module can be configured to warn of weak passwords only, but not 103actually enforce strong passwords. The "users" setting will enforce 104strong passwords for invocations by non-root users only. 105 106 non-unix [] 107 108Normally, the module uses getpwnam(3) to obtain the user's personal 109login information and use that during the password strength checks. 110This behavior can be disabled with the "non-unix" option. 111 112 retry=N [retry=3] 113 114The number of times the module will ask for a new password if the user 115fails to provide a sufficiently strong password and enter it twice the 116first time. 117 118 ask_oldauthtok[=update] [] 119 120Ask for the old password as well. Normally, pam_passwdqc leaves this 121task for subsequent modules. With no argument, the "ask_oldauthtok" 122option will cause pam_passwdqc to ask for the old password during the 123preliminary check phase. With "ask_oldauthtok=update", pam_passwdqc 124will do that during the update phase. 125 126 check_oldauthtok [] 127 128This tells pam_passwdqc to validate the old password before giving a 129new password prompt. Normally, this task is left for subsequent 130modules. 131 132The primary use for this option is when "ask_oldauthtok=update" is 133also specified, in which case no other module gets a chance to ask 134for and validate the password. Of course, this will only work with 135Unix passwords. 136 137 use_first_pass [] 138 use_authtok [] 139 140Use the new password obtained by modules stacked before pam_passwdqc. 141This disables user interaction within pam_passwdqc. With this module, 142the only difference between "use_first_pass" and "use_authtok" is that 143the former is incompatible with "ask_oldauthtok". 144 145-- 146Solar Designer <solar at openwall.com> 147 148$Owl: Owl/packages/pam_passwdqc/pam_passwdqc/README,v 1.11 2008/02/12 19:43:33 solar Exp $ 149