Mastodon
Mastodon is the Fediverse software run in the Shivering-Isles infrastructure. It is currently running as a single-user instance.
The instance is currently deployed using a helm chart maintained as part of the GitOps repository.
SSO Enforcement
Since Mastodon itself has no configuration to enforce the presence of specific claims or roles, an oauth-proxy setup in front of the /auth/ section preventing clients from reaching the callback URL for OIDC authentication, without passing through the oauth2-proxy which can enforce the presence of a role.
While the result in a double redirect to OIDC, once by the oauth2-proxy and once by Mastodon itself, it makes sure that there is proper enforcement of the roles without requiring modification of Mastodon.