The Identity service supports the notion of groups and roles. Users belong to groups while a group has a list of roles. OpenStack services reference the roles of the user attempting to access the service. The OpenStack policy enforcer middleware takes into consideration the policy rule associated with each resource then the user’s group/roles and association to determine if access is allowed to the requested resource.
The policy enforcement middleware enables fine-grained access control to OpenStack resources. The behaviour of the policy is discussed in depth in Policies.
Establish formal access control policies¶
Prior to configuring roles, groups, and users, document your required access control policies for the OpenStack installation. The policies should be consistent with any regulatory or legal requirements for the organization. Future modifications to the access control configuration should be done consistently with the formal policies. The policies should include the conditions and processes for creating, deleting, disabling, and enabling accounts, and for assigning privileges to the accounts. Periodically review the policies and ensure that the configuration is in compliance with approved policies.
Cloud administrators must define a user with the role of admin for each service, as described in the OpenStack Administrator Guide. This service account provides the service with the authorization to authenticate users.
The Compute and Object Storage services can be configured to use the Identity service to store authentication information. Other options to store authentication information include the use of the “tempAuth” file, however this should not be deployed in a production environment as the password is displayed in plain text.
The Identity service supports client authentication for TLS which may be enabled. TLS client authentication provides an additional authentication factor, in addition to the user name and password, that provides greater reliability on user identification. It reduces the risk of unauthorized access when user names and passwords may be compromised. However, there is additional administrative overhead and cost to issue certificates to users that may not be feasible in every deployment.
We recommend that you use client authentication with TLS for the authentication of services to the Identity service.
The cloud administrator should protect sensitive configuration files
from unauthorized modification. This can be achieved with mandatory
access control frameworks such as SELinux, including
/etc/keystone/keystone.conf and X.509 certificates.
Client authentication with TLS requires certificates be issued to
services. These certificates can be signed by an external or internal
certificate authority. OpenStack services check the validity of
certificate signatures against trusted CAs by default and connections
will fail if the signature is not valid or the CA is not trusted. Cloud
deployers may use self-signed certificates. In this case, the validity
check must be disabled or the certificate should be marked as trusted.
To disable validation of self-signed certificates, set
insecure=False in the
[filter:authtoken] section in the
/etc/nova/api.paste.ini file. This setting also disables
certificates for other components.
We recommend that admin users authenticate using Identity service and an external authentication service that supports 2-factor authentication, such as a certificate. This reduces the risk from passwords that may be compromised. This recommendation is in compliance with NIST 800-53 IA-2(1) guidance in the use of multi-factor authentication for network access to privileged accounts.
The Identity service can directly provide end-user authentication, or can be configured to use external authentication methods to conform to an organization’s security policies and requirements.