Agent Token

Purpose

The concept of agent tokens is to provide a mechanism by which the relationship between an operating deployment of the Bare Metal Service and an instance of the ironic-python-agent is verified. In a sense, this token can be viewed as a session identifier or authentication token.

Warning

This functionality does not remove the risk of a man-in-the-middle attack that could occur from connection intercept or when TLS is not used for all communication.

This becomes useful in the case of deploying an "edge" node where intermediate networks are not trustworthy.

How it works

These tokens are provided in one of two ways to the running agent.

A pre-generated token which is embedded into virtual media ISOs.
A one-time generated token that are provided upon the first "lookup" of the node.

In both cases, the tokens are a randomly generated using the Python secrets library. As of mid-2020, the default length is 43 characters.

Once the token has been provided, the token cannot be retrieved or accessed. It remains available to the conductors, and is stored in memory of the ironic-python-agent.

Note

In the case of the token being embedded with virtual media, it is read from a configuration file with-in the image. Ideally this should be paired with Swift temporary URLs.

With the token is available in memory in the agent, the token is embedded with heartbeat operations to the ironic API endpoint. This enables the API to authenticate the heartbeat request, and refuse "heartbeat" requests from the ironic-python-agent. As of the Victoria release, use of Agent Token is required for all agents and the previously available setting to force this functionality to be mandatory, [DEFAULT]require_agent_token no longer has any effect.

Warning

If the Bare Metal Service is updated, and the version of ironic-python-agent should be updated to enable this feature.

In addition to heartbeats being verified, commands from the ironic-conductor service to the ironic-python-agent also include the token, allowing the agent to authenticate the caller.

With Virtual Media

diagram {

API; Conductor; Baremetal; Swift; IPA; activation = none; span_height = 1; edge_length = 250; default_note_color = white; default_fontsize = 14;

Conductor -> Conductor [label = "Generates a random token"]; Conductor -> Conductor [label = "Generates configuration for IPA ramdisk"]; Conductor -> Swift [label = "IPA image, with configuration is uploaded"]; Conductor -> Baremetal [label = "Attach IPA virtual media in Swift as virtual CD"]; Conductor -> Baremetal [label = "Conductor turns power on"]; Baremetal -> Swift [label = "Baremetal reads virtual media"]; Baremetal -> Baremetal [label = "Boots IPA virtual media image"]; Baremetal -> Baremetal [label = "IPA is started"]; IPA -> Baremetal [label = "IPA loads configuration and agent token into memory"]; IPA -> API [label = "Lookup node"]; API -> IPA [label = "API responds with node UUID and token value of '******'"]; IPA -> API [label = "Heartbeat with agent token"];

}

With PXE/iPXE/etc.

diagram {

API; Conductor; Baremetal; iPXE; IPA; activation = none; span_height = 1; edge_length = 250; default_note_color = white; default_fontsize = 14;

Conductor -> Baremetal [label = "Conductor turns power on"]; Baremetal -> iPXE [label = "Baremetal reads kernel/ramdisk and starts boot"]; Baremetal -> Baremetal [label = "Boots IPA iPXE image"]; Baremetal -> Baremetal [label = "IPA is started"]; IPA -> Baremetal [label = "IPA loads configuration"]; IPA -> API [label = "Lookup node"]; API -> Conductor [label = "API requests conductor to generates a random token"]; API -> IPA [label = "API responds with node UUID and token value"]; IPA -> API [label = "Heartbeat with agent token"];

}

Agent Configuration

An additional setting which may be leveraged with the ironic-python-agent is a agent_token_required setting. Under normal circumstances, this setting can be asserted via the configuration supplied from the Bare Metal service deployment upon the lookup action, but can be asserted via the embedded configuration for the agent in the ramdisk. This setting is also available via kernel command line as ipa-agent-token-required.

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