The default password syntax requires a minimum password length of eight characters and that no trivial words are used in the password. A trivial word is any value stored in the uid, cn, sn, givenName, ou, or mailattributes of the user's entry.

Additionally, other forms of password syntax enforcement are possible, providing different optional categories for the password syntax:

•Minimum required number of characters in the password (passwordMinLength)

•Minimum number of digit characters, meaning numbers between zero and nine (passwordMinDigits)

•Minimum number of ASCII alphabetic characters, both upper- and lower-case (passwordMinAlphas)

•Minimum number of uppercase ASCII alphabetic characters (passworMinUppers)

•Minimum number of lowercase ASCII alphabetic characters (passwordMinLowers)

•Minimum number of special ASCII characters, such as !@#$ (passwordMinSpecials)

•Minimum number of 8-bit characters (passwordMin8bit)

•Maximum number of times that the same character can be immediately repeated, such as aaabbb (passwordMaxRepeats)

•Minimum number of character categories required per password; a category can be upper- or lower-case letters, special characters, digits, or 8-bit characters (passwordMinCategories)

The more categories of syntax required, the stronger the password.

By default, password syntax checking is disabled.

8.6.2.7Password length

The password policy can require a minimum length for user passwords. In general, shorter passwords are easier to crack. A good length for passwords is eight characters. This is long enough to be difficult to crack but short enough that users can remember the password without writing it down. The valid range of values for this attribute is from two to 512 characters.

By default, no minimum password length is set.

8.6.2.8Password minimum age

The password policy can prevent users from changing their passwords for a specified time. When used in conjunction with the passwordHistory attribute, users are discouraged from reusing old passwords.

For example, if the password minimum age (passwordMinAge) attribute is two days, users cannot repeatedly change their passwords during a single session. This prevents them from cycling through the password history so that they can reuse an old password.

The valid range of values for this attribute is from zero to 24,855 days. A value of zero (0) indicates that the user can change the password immediately.

8.6.2.9Password history

The Directory Server can store from two to 24 passwords in the password history; if a password is in the history, a user cannot reset his password to that old password. This prevents users from reusing a couple of passwords that are easy to remember. Alternatively, the password history can be disabled, thus allowing users to reuse passwords.

The passwords remain in history even if the password history is off so that if the password history is turned back on, users cannot reuse the passwords that were in the history before the password history was disabled.

The server does not maintain a password history by default.

8.6 Designing a password policy 115