8.6.2.10 Password storage schemes

The password storage scheme specifies the type of encryption used to store Directory Server passwords within the directory. The Directory Server supports several different password storage schemes:

•Salted Secure Hash Algorithm (SSHA, SSHA-256, SSHA-384, and SSHA-512).

This is the most secure password storage scheme and is the default. The recommended SSHA scheme is SSHA-256 or stronger.

•CLEAR

No encryption. This is the only option which can be used with SASL Digest-MD5, so using SASL requires the CLEAR password storage scheme.

Although passwords stored in the directory can be protected through the use of access control information (ACI) instructions, it is still not a good idea to store plain text passwords in the directory.

•Secure Hash Algorithm (SHA, SHA-256, SHA-384, and SHA-512) This is less secure than SSHA.

•UNIX CRYPT algorithm

This algorithm provides compatibility with UNIX passwords.

•MD5

This storage scheme is less secure than SSHA, but it is included for legacy applications which require MD5.

8.6.3Designing an account lockout policy

After establishing a password policy for the directory service, protect user passwords from potential threats by configuring an account lockout policy.

The lockout policy works in conjunction with the password policy to provide further security. The account lockout feature protects against crackers who try to break into the directory by repeatedly trying to guess a user's password. A specific user can be locked out of the directory after a given number of failed attempts to bind.

8.6.4 Designing a password policy in a replicated environment

Password and account lockout policies are enforced in a replicated environment as follows:

•Password policies are enforced on the data master.

•Account lockout is enforced on all servers in the replication setup.

The password policy information in the directory, such as password age, the account lockout counter, and the expiration warning counter, are all replicated. The configuration information, however, is stored locally and is not replicated. This information includes the password syntax and the history of password modifications.

When configuring a password policy in a replicated environment, consider the following points:

•All replicas issue warnings of an impending password expiration. This information is kept locally on each server, so if a user binds to several replicas in turn, the user receives the same warning several times. In addition, if the user changes the password, it may take time for this information to filter through to the replicas. If a user changes a password, then immediately rebinds, the bind may fail until the replica registers the changes.

•The same bind behavior should occur on all servers, including suppliers and replicas. Always create the same password policy configuration information on each server.

•Account lockout counters may not work as expected in a multi-master environment.

116 Designing a secure directory