Stack domain users

Stack domain users allow the Orchestration service to authorize and start the following operations within booted virtual machines:

  • Provide metadata to agents inside instances. Agents poll for changes and apply the configuration that is expressed in the metadata to the instance.

  • Detect when an action is complete. Typically, software configuration on a virtual machine after it is booted. Compute moves the VM state to “Active” as soon as it creates it, not when the Orchestration service has fully configured it.

  • Provide application level status or meters from inside the instance. For example, allow auto-scaling actions to be performed in response to some measure of performance or quality of service.

The Orchestration service provides APIs that enable all of these operations, but all of those APIs require authentication. For example, credentials to access the instance that the agent is running upon. The heat-cfntools agents use signed requests, which require an ec2 key pair created through Identity. The key pair is then used to sign requests to the Orchestration CloudFormation and CloudWatch compatible APIs, which are authenticated through signature validation. Signature validation uses the Identity ec2tokens extension.

Stack domain users encapsulate all stack-defined users (users who are created as a result of data that is contained in an Orchestration template) in a separate domain. The separate domain is created specifically to contain data related to the Orchestration stacks only. A user is created, which is the domain admin, and Orchestration uses the domain admin to manage the lifecycle of the users in the stack user domain.

Stack domain users configuration

To configure stack domain user, the Orchestration service completes the following tasks:

  1. A special OpenStack Identity service domain is created. For example, a domain that is called heat and the ID is set with the stack_user_domain option in the heat.conf file.

  2. A user with sufficient permissions to create and delete projects and users in the heat domain is created.

  3. The username and password for the domain admin user is set in the heat.conf file (stack_domain_admin and stack_domain_admin_password). This user administers stack domain users on behalf of stack owners, so they no longer need to be administrators themselves. The risk of this escalation path is limited because the heat_domain_admin is only given administrative permission for the heat domain.

To set up stack domain users, complete the following steps:

  1. Create the domain:

    $OS_TOKEN refers to a token. For example, the service admin token or some other valid token for a user with sufficient roles to create users and domains. $KS_ENDPOINT_V3 refers to the v3 OpenStack Identity endpoint (for example, http://keystone_address:5000/v3 where keystone_address is the IP address or resolvable name for the Identity service).

    $ openstack --os-token $OS_TOKEN --os-url=$KS_ENDPOINT_V3 --os-\
  identity-api-version=3 domain create heat --description "Owns \
  users and projects created by heat"

    The domain ID is returned by this command, and is referred to as $HEAT_DOMAIN_ID below.

  2. Create the user:

    $ openstack --os-token $OS_TOKEN --os-url=$KS_ENDPOINT_V3 --os-\
  identity-api-version=3 user create --password $PASSWORD --domain \
  $HEAT_DOMAIN_ID heat_domain_admin --description "Manages users \
  and projects created by heat"

    The user ID is returned by this command and is referred to as $DOMAIN_ADMIN_ID below.

  3. Make the user a domain admin:

    $ openstack --os-token $OS_TOKEN --os-url=$KS_ENDPOINT_V3 --os-\
  identity-api-version=3 role add --user $DOMAIN_ADMIN_ID --domain \
  $HEAT_DOMAIN_ID admin

    Then you must add the domain ID, username and password from these steps to the heat.conf file:

    stack_domain_admin_password = password
stack_domain_admin = heat_domain_admin
stack_user_domain = domain id returned from domain create above

Usage workflow

The following steps are run during stack creation:

  1. Orchestration creates a new stack domain project in the heat domain if the stack contains any resources that require creation of a stack domain user.

  2. For any resources that require a user, the Orchestration service creates the user in the stack domain project. The stack domain project is associated with the Orchestration stack in the Orchestration database, but is separate and unrelated (from an authentication perspective) to the stack owners project. The users who are created in the stack domain are still assigned the heat_stack_user role, so the API surface they can access is limited through the policy.yaml file. For more information, see OpenStack Identity documentation.

  3. When API requests are processed, the Orchestration service performs an internal lookup, and allows stack details for a given stack to be retrieved. Details are retrieved from the database for both the stack owner’s project (the default API path to the stack) and the stack domain project, subject to the policy.yaml restrictions.

This means there are now two paths that can result in the same data being retrieved through the Orchestration API. The following example is for resource-metadata:

GET v1/​{stack_owner_project_id}​/stacks/​{stack_name}​/\
​{stack_id}​/resources/​{resource_name}​/metadata

or:

GET v1/​{stack_domain_project_id}​/stacks/​{stack_name}​/​\
{stack_id}​/resources/​{resource_name}​/metadata

The stack owner uses the former (via openstack stack resource metadata STACK RESOURCE), and any agents in the instance use the latter.