OpenStack Identity manages authentication and authorization. A trust is an OpenStack Identity extension that enables delegation and, optionally, impersonation through keystone. A trust extension defines a relationship between:


The user delegating a limited set of their own rights to another user.


The user trust is being delegated to, for a limited time.

The trust can eventually allow the trustee to impersonate the trustor. For security reasons, some safeties are added. For example, if a trustor loses a given role, any trusts the user issued with that role, and the related tokens, are automatically revoked.

The delegation parameters are:

User ID

The user IDs for the trustor and trustee.


The delegated privileges are a combination of a project ID and a number of roles that must be a subset of the roles assigned to the trustor.

If you omit all privileges, nothing is delegated. You cannot delegate everything.

Delegation depth

Defines whether or not the delegation is recursive. If it is recursive, defines the delegation chain length.

Specify one of the following values:

  • 0. The delegate cannot delegate these permissions further.

  • 1. The delegate can delegate the permissions to any set of delegates but the latter cannot delegate further.

  • inf. The delegation is infinitely recursive.


A list of endpoints associated with the delegation.

This parameter further restricts the delegation to the specified endpoints only. If you omit the endpoints, the delegation is useless. A special value of all_endpoints allows the trust to be used by all endpoints associated with the delegated project.


(Optional) Comprised of the start time and end time for the trust.


See the administrator guide on removing expired trusts for recommended maintenance procedures.