Keystone tokens

Keystone tokens

Tokens are used to authenticate and authorize your interactions with the various OpenStack APIs. Tokens come in many flavors, representing various authorization scopes and sources of identity. There are also several different “token providers”, each with their own user experience, performance, and deployment characteristics.

Authorization scopes

Tokens can express your authorization in different scopes. You likely have different sets of roles, in different projects, and in different domains. While tokens always express your identity, they may only ever express one set of roles in one authorization scope at a time.

Each level of authorization scope is useful for certain types of operations in certain OpenStack services, and are not interchangeable.

Unscoped tokens

An unscoped token contains neither a service catalog, any roles, a project scope, nor a domain scope. Their primary use case is simply to prove your identity to keystone at a later time (usually to generate scoped tokens), without repeatedly presenting your original credentials.

The following conditions must be met to receive an unscoped token:

  • You must not specify an authorization scope in your authentication request (for example, on the command line with arguments such as --os-project-name or --os-domain-id),
  • Your identity must not have a “default project” associated with it that you also have role assignments, and thus authorization, upon.

Project-scoped tokens

Project-scoped tokens are the bread and butter of OpenStack. They express your authorization to operate in a specific tenancy of the cloud and are useful to authenticate yourself when working with most other services.

They contain a service catalog, a set of roles, and details of the project upon which you have authorization.

Domain-scoped tokens

Domain-scoped tokens also have limited use cases in OpenStack. They express your authorization to operate a domain-level, above that of the user and projects contained therein (typically as a domain-level administrator). Depending on Keystone’s configuration, they are useful for working with a single domain in Keystone.

They contain a limited service catalog (only those services which do not explicitly require per-project endpoints), a set of roles, and details of the project upon which you have authorization.

They can also be used to work with domain-level concerns in other services, such as to configure domain-wide quotas that apply to all users or projects in a specific domain.

Token providers

The token type issued by keystone is configurable through the /etc/keystone/keystone.conf file. Currently, there are four supported token types and they include UUID, fernet, PKI, and PKIZ.

UUID tokens

UUID was the first token type supported and is currently the default token provider. UUID tokens are 32 bytes in length and must be persisted in a back end. Clients must pass their UUID token to the Identity service in order to validate it.

Fernet tokens

The fernet token format was introduced in the OpenStack Kilo release. Unlike the other token types mentioned in this document, fernet tokens do not need to be persisted in a back end. AES256 encryption is used to protect the information stored in the token and integrity is verified with a SHA256 HMAC signature. Only the Identity service should have access to the keys used to encrypt and decrypt fernet tokens. Like UUID tokens, fernet tokens must be passed back to the Identity service in order to validate them. For more information on the fernet token type, see the Fernet - Frequently Asked Questions.

PKI and PKIZ tokens

PKI tokens are signed documents that contain the authentication context, as well as the service catalog. Depending on the size of the OpenStack deployment, these tokens can be very long. The Identity service uses public/private key pairs and certificates in order to create and validate PKI tokens.

The same concepts from PKI tokens apply to PKIZ tokens. The only difference between the two is PKIZ tokens are compressed to help mitigate the size issues of PKI. For more information on the certificate setup for PKI and PKIZ tokens, see the Certificates for PKI.


PKI and PKIZ tokens are deprecated and not supported in Ocata.

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