The Identity service can store user credentials in an SQL Database, or may use an LDAP-compliant directory server. The Identity database may be separate from databases used by other OpenStack services to reduce the risk of a compromise of the stored credentials.
When you use a user name and password to authenticate, Identity does not enforce policies on password strength, expiration, or failed authentication attempts as recommended by NIST Special Publication 800-118 (draft). Organizations that desire to enforce stronger password policies should consider using Identity extensions or external authentication services.
LDAP simplifies integration of Identity authentication into an organization’s existing directory service and user account management processes.
Authentication and authorization policy in OpenStack may be delegated to another service. A typical use case is an organization that seeks to deploy a private cloud and already has a database of employees and users in an LDAP system. Using this as the authentication authority, requests to the Identity service are delegated to the LDAP system, which will then authorize or deny based on its policies. Upon successful authentication, the Identity service then generates a token that is used for access to authorized services.
Note that if the LDAP system has attributes defined for the user such as
admin, finance, HR etc, these must be mapped into roles and groups
within Identity for use by the various OpenStack services. The
/etc/keystone/keystone.conf file maps LDAP attributes to Identity
The Identity service MUST NOT be allowed to write to LDAP services used for authentication outside of the OpenStack deployment as this would allow a sufficiently privileged keystone user to make changes to the LDAP directory. This would allow privilege escalation within the wider organization or facilitate unauthorized access to other information and resources. In such a deployment, user provisioning would be out of the realm of the OpenStack deployment.
Organizations may desire to implement external authentication for compatibility with existing authentication services or to enforce stronger authentication policy requirements. Although passwords are the most common form of authentication, they can be compromised through numerous methods, including keystroke logging and password compromise. External authentication services can provide alternative forms of authentication that minimize the risk from weak passwords.