Added the [OIDC Discovery](https://openid.net/specs/openid-connect-discovery-1_0.html) `/.well-known/openid-configuration` endpoint to Nomad, but it is only enabled if the `server.oidc_issuer` parameter is set. Documented the parameter, but without a tutorial trying to actually _use_ this will be very hard.
I intentionally did *not* use https://github.com/hashicorp/cap for the OIDC configuration struct because it's built to be a *compliant* OIDC provider. Nomad is *not* trying to be compliant initially because compliance to the spec does not guarantee it will actually satisfy the requirements of third parties. I want to avoid the problem where in an attempt to be standards compliant we ship configuration parameters that lock us in to a certain behavior that we end up regretting. I want to add parameters and behaviors as there's a demonstrable need.
Users always have the escape hatch of providing their own OIDC configuration endpoint. Nomad just needs to know the Issuer so that the JWTs match the OIDC configuration. There's no reason the actual OIDC configuration JSON couldn't live in S3 and get served directly from there. Unlike JWKS the OIDC configuration should be static, or at least change very rarely.
This PR is just the endpoint extracted from #18535. The `RS256` algorithm still needs to be added in hopes of supporting third parties such as [AWS IAM OIDC Provider](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_providers_create_oidc.html).
Co-authored-by: Luiz Aoqui <luiz@hashicorp.com>
When the `Full` flag is passed for key rotation, we kick off a core
job to decrypt and re-encrypt all the secure variables so that they
use the new key.
After internal design review, we decided to remove exposing algorithm
choice to the end-user for the initial release. We'll solve nonce
rotation by forcing rotations automatically on key GC (in a core job,
not included in this changeset). Default to AES-256 GCM for the
following criteria:
* faster implementation when hardware acceleration is available
* FIPS compliant
* implementation in pure go
* post-quantum resistance
Also fixed a bug in the decoding from keystore and switched to a
harder-to-misuse encoding method.
When a server becomes leader, it will check if there are any keys in
the state store, and create one if there is not. The key metadata will
be replicated via raft to all followers, who will then get the key
material via key replication (not implemented in this changeset).
This changeset implements the keystore serialization/deserialization:
* Adds a JSON serialization extension for the `RootKey` struct, along with a metadata stub. When we serialize RootKey to the on-disk keystore, we want to base64 encode the key material but also exclude any frequently-changing fields which are stored in raft.
* Implements methods for loading/saving keys to the keystore.
* Implements methods for restoring the whole keystore from disk.
* Wires it all up with the `Keyring` RPC handlers and fixes up any fallout on tests.
