5.2.9 Ensure minimum password length is configured

Information

The minimum password length setting determines the lowers number of characters that make up a password for a user account. There are many different theories about how to determine the best password length for an organization, but perhaps "passphrase" is a better term than "password".

The minlen option sets the minimum acceptable size for the new password.

Strong passwords help protect systems from password attacks. Types of password attacks include dictionary attacks, which attempt to use common words and phrases, and brute force attacks, which try every possible combination of characters. Also attackers may try to obtain the account database so they can use tools to discover the accounts and passwords.

Solution

In /etc/security/user set the default user stanza minlen attribute to be greater than or equal to 14 :

chsec -f /etc/security/user -s default -a minlen=14

This means that all user passwords must be at least 14 characters in length.

NOTE : To support a password length greater than 8 characters the default algorithm must be changed. If the command above returns an error ( 3004-692 Error changing "minlen" to "14" : Value is invalid. ) the recommendation

3.1.15 /etc/security/login.cfg - pwd_algorithm

needs to be completed first.

Impact:

In general, it is true that longer passwords are better (harder to crack), but it is also true that forced password length requirements can cause user behavior that is predictable and undesirable. For example, requiring users to have a minimum 16-character password may cause them to choose repeating patterns like fourfourfourfour or passwordpassword that meet the requirement but aren't hard to guess. Additionally,length requirements increase the chances that users will adopt other insecure practices, like writing them down, re-using them or storing them unencrypted in their documents.

Having a reasonable minimum length with no maximum character limit increases the resulting average password length used (and therefore the strength).

See Also

https://workbench.cisecurity.org/benchmarks/10385

Item Details

Category: IDENTIFICATION AND AUTHENTICATION

References: 800-53|IA-5(1), CSCv7|4.4

Plugin: Unix

Control ID: 25923614c0ed48796a5e5754062932296b5a3bba050090d69af1deae3a9c8969