In order to support implicit ACL policies for tasks to get their own
secrets, each task would need to have its own ACL token. This would
add extra raft overhead as well as new garbage collection jobs for
cleaning up task-specific ACL tokens. Instead, Nomad will create a
workload Identity Claim for each task.
An Identity Claim is a JSON Web Token (JWT) signed by the server’s
private key and attached to an Allocation at the time a plan is
applied. The encoded JWT can be submitted as the X-Nomad-Token header
to replace ACL token secret IDs for the RPCs that support identity
claims.
Whenever a key is is added to a server’s keyring, it will use the key
as the seed for a Ed25519 public-private private keypair. That keypair
will be used for signing the JWT and for verifying the JWT.
This implementation is a ruthlessly minimal approach to support the
secure variables feature. When a JWT is verified, the allocation ID
will be checked against the Nomad state store, and non-existent or
terminal allocation IDs will cause the validation to be rejected. This
is sufficient to support the secure variables feature at launch
without requiring implementation of a background process to renew
soon-to-expire tokens.
PR #11956 implemented a new mTLS RPC check to validate the role of the
certificate used in the request, but further testing revealed two flaws:
1. client-only endpoints did not accept server certificates so the
request would fail when forwarded from one server to another.
2. the certificate was being checked after the request was forwarded,
so the check would happen over the server certificate, not the
actual source.
This commit checks for the desired mTLS level, where the client level
accepts both, a server or a client certificate. It also validates the
cercertificate before the request is forwarded.
