python-openstackclient/doc/source/authentication.rst

Authentication

OpenStackClient leverages python-keystoneclient authentication plugins to support a number of different authentication methods.

Authentication Process

The user provides some number of authentication credential options. If an authentication type is not provided (--os-auth-type), the authentication options are examined to determine if one of the default types can be used. If no match is found an error is reported and OSC exits.

Note that the authentication call to the Identity service has not yet occurred. It is deferred until the last possible moment in order to reduce the number of unnecessary queries to the server, such as when further processing detects an invalid command.

Authentication Plugins

The Keystone client library implements the base set of plugins. Additional plugins may be available from the Keystone project or other sources.

There are at least three authentication types that are always available:

• Password: A project, username and password are used to identify the user. An optional domain may also be included. This is the most common type and is the default any time a username is supplied. An authentication URL for the Identity service is also required. [Required: --os-auth-url, --os-project-name, --os-username; Optional: --os-password]
• Token: This is slightly different from the usual token authentication (described below as token/endpoint) in that a token and an authentication URL are supplied and the plugin retrieves a new token. [Required: --os-auth-url, --os-token]
• Token/Endpoint: This is the original token authentication (known as 'token flow' in the early CLI documentation in the OpenStack wiki). It requires a token and a direct endpoint that is used in the API call. The difference from the new Token type is this token is used as-is, no call is made to the Identity service from the client. This type is most often used to bootstrap a Keystone server where the token is the admin_token configured in keystone.conf. It will also work with other services and a regular scoped token such as one obtained from a token issue command. [Required: --os-url, --os-token]
• Others: Other authentication plugins such as SAML, Kerberos, and OAuth1.0 are under development and also supported. To use them, they must be selected by supplying the --os-auth-type option.

Detailed Process

The authentication process in OpenStackClient is all contained in and handled by the ClientManager object.

• On import api.auth:
  • obtains the list of installed Keystone authentication plugins from the keystoneclient.auth.plugin entry point.
  • builds a list of authentication options from the plugins.
• A new ClientManager is created and supplied with the set of options from the command line and/or environment:

  • If --os-auth-type is provided and is a valid and available plugin

    it is used.

  • If --os-auth-type is not provided an authentication plugin is selected based on the existing options. This is a short-circuit evaluation, the first match wins.
    • If --os-endpoint and --os-token are both present token_endpoint is selected
    • If --os-username is supplied password is selected
    • If --os-token is supplied token is selected
    • If no selection has been made by now exit with error
  • Load the selected plugin class.
• When an operation that requires authentication is attempted ClientManager makes the actual inital request to the Identity service.
  • if --os-auth-url is not supplied for any of the types except Token/Endpoint, exit with an error.