Vault¶

Going through the docs, a strawman proposal on how to use Vault from an Arvados container:

• Credentials are entered into Vault
• Client (arvados-cwl-runner?) generates a Vault token with restricted policy (can only read credentials)
• Container request is expanded to include Vault token
• Vault token cannot be read back from container request via API
• Cannot have container reuse with Vault tokens
• On the compute node, read the container record
• The container record only includes the vault token when queried by the container run token.
• The container can now read the secret at the path provided in the input
• When the container request is finalized, the Vault token is revoked.

Notes:

• Credentials may be passed in via environment, config file or command line like any other input, so it would be nice to generalize this as a CWL feature where some inputs are simply marked "sensitive" and automatically handled by Vault. However, while arvados-cwl-runner is responsible for constructing the container request it doesn't run on the compute node, only crunch-run, which is "dumb", so its not clear how we go about allowing for arbitrary substitution into the environment, command line, or config file on the compute node.
• Response wrapping is another mechanism provided by Vault for delegating access. A wrapped response can be passed through and accessed exactly once (would imply max_container_count: 1).
• Another solution is to develop an AuthMethod for vault with Arvados Token proivded by the container.