Policies

Glance’s public API calls may be restricted to certain sets of users
using a policy configuration file. This document explains exactly how
policies are configured and what they apply to.

A policy is composed of a set of rules that are used by the policy
“Brain” in determining if a particular action may be performed by the
authorized tenant.

Constructing a Policy
Configuration File

A policy configuration file is a simply JSON object that contain sets
of rules. Each top-level key is the name of a rule. Each rule is a
string that describes an action that may be performed in the Glance
API.

The actions that may have a rule enforced on them are:

• get_images – List available image entities
  • GET /v1/images
  • GET /v1/images/detail
  • GET /v2/images
• get_image – Retrieve a specific image entity
  • HEAD /v1/images/<IMAGE_ID>
  • GET /v1/images/<IMAGE_ID>
  • GET /v2/images/<IMAGE_ID>
• download_image – Download binary image data
  • GET /v1/images/<IMAGE_ID>
  • GET /v2/images/<IMAGE_ID>/file
• upload_image – Upload binary image data
  • POST /v1/images
  • PUT /v1/images/<IMAGE_ID>
  • PUT /v2/images/<IMAGE_ID>/file
• copy_from – Copy binary image data from URL
  • POST /v1/images
  • PUT /v1/images/<IMAGE_ID>
• add_image – Create an image entity
  • POST /v1/images
  • POST /v2/images
• modify_image – Update an image entity
  • PUT /v1/images/<IMAGE_ID>
  • PUT /v2/images/<IMAGE_ID>
• publicize_image – Create or update public images
  • POST /v1/images with attribute is_public =
    true
  • PUT /v1/images/<IMAGE_ID> with attribute
    is_public = true
  • POST /v2/images with attribute visibility
    = public
  • PUT /v2/images/<IMAGE_ID> with attribute
    visibility = public
• communitize_image – Create or update community images
  • POST /v2/images with attribute visibility
    = community
  • PUT /v2/images/<IMAGE_ID> with attribute
    visibility = community
• delete_image – Delete an image entity and associated
  binary data
  • DELETE /v1/images/<IMAGE_ID>
  • DELETE /v2/images/<IMAGE_ID>
• add_member – Add a membership to the member repo of an
  image
  • POST /v2/images/<IMAGE_ID>/members
• get_members – List the members of an image
  • GET /v1/images/<IMAGE_ID>/members
  • GET /v2/images/<IMAGE_ID>/members
• delete_member – Delete a membership of an image
  • DELETE /v1/images/<IMAGE_ID>/members/<MEMBER_ID>
  • DELETE /v2/images/<IMAGE_ID>/members/<MEMBER_ID>
• modify_member – Create or update the membership of an
  image
  • PUT /v1/images/<IMAGE_ID>/members/<MEMBER_ID>
  • PUT /v1/images/<IMAGE_ID>/members
  • POST /v2/images/<IMAGE_ID>/members
  • PUT /v2/images/<IMAGE_ID>/members/<MEMBER_ID>
• manage_image_cache – Allowed to use the image cache
  management API

To limit an action to a particular role or roles, you list the roles
like so :

{
  "delete_image": ["role:admin", "role:superuser"]
}

The above would add a rule that only allowed users that had roles of
either “admin” or “superuser” to delete an image.

Writing Rules

Role checks are going to continue to work exactly as they already do.
If the role defined in the check is one that the user holds, then that
will pass, e.g., role:admin.

To write a generic rule, you need to know that there are three values
provided by Glance that can be used in a rule on the left side of the
colon (:). Those values are the current user’s credentials
in the form of:

• role
• tenant
• owner

The left side of the colon can also contain any value that Python can
understand, e.g.,:

• True
• False
• "a string"
• &c.

Using tenant and owner will only work with
images. Consider the following rule:

tenant:%(owner)s

This will use the tenant value of the currently
authenticated user. It will also use owner from the image
it is acting upon. If those two values are equivalent the check will
pass. All attributes on an image (as well as extra image properties) are
available for use on the right side of the colon. The most useful are
the following:

• owner
• protected
• is_public

Therefore, you could construct a set of rules like the following:

{
    "not_protected": "False:%(protected)s",
    "is_owner": "tenant:%(owner)s",
    "is_owner_or_admin": "rule:is_owner or role:admin",
    "not_protected_and_is_owner": "rule:not_protected and rule:is_owner",

    "get_image": "rule:is_owner_or_admin",
    "delete_image": "rule:not_protected_and_is_owner",
    "add_member": "rule:not_protected_and_is_owner"
}

Examples

Example 1. (The default policy configuration)

{
    "default": ""
}

Note that an empty JSON list means that all methods of the Glance API
are callable by anyone.

Example 2. Disallow modification calls to non-admins

{
    "default": "",
    "add_image": "role:admin",
    "modify_image": "role:admin",
    "delete_image": "role:admin"
}