`felis nano` serves the vanilla sessionserver protocol
(GET /session/minecraft/hasJoined) as a federating multiplexer over
Mojang plus any number of third-party Yggdrasil roots, with no k3s,
Postgres, or panel — a MultiLogin-style auth front-end delivered as a
subcommand of the single felis binary rather than a separate build.
- config.LoadNano reads only [[auth_source]] blocks; it skips the
database.url / root_domain / archive requirements the full server
needs. Zero sources is valid (Mojang-only).
- Mojang is prepended in code (Identity:true), never from config, so it
is always the sole identity root. Third-party profiles are rewritten
to canonical = UUIDv3(felisAuthNS, tag+":"+nativeID).
- validateAuthSources rejects unknown keys, duplicate tags, and
scheme-less URLs — a malformed nano config fails loud at load.
- Reuses api.HasJoinedHandler with a stub Repo (no blacklist backend);
a rejected login is a 204, matching the vanilla sessionserver.
- nano.go binds the -listen flag and ignores [server] listen in config.
Verified on WSL (go1.26.4): go build/vet/test ./... green; a runtime
smoke against the template config returns 204 on a miss and logs
"Mojang + 0 third-party source(s)"; a duplicate-tag config exits
non-zero citing "unique".
Step 2 of Felis-nano: a [[auth_source]] array-of-tables (tag + full hasJoined
url, config order = priority) supplies the multiplexer's third-party Yggdrasil
roots; cmd/felis prepends Mojang as the sole code-owned identity anchor and
wires them into API.AuthSources. With no sources configured the endpoint stays
inert (204s), unchanged from step 1.
The config deliberately has no identity/trusted field: Mojang is the only source
whose self-asserted UUIDs are trusted verbatim, so no misconfiguration can
reopen the impersonation hole the per-source UUID rewrite closes. An identity=
key is an unknown key and Load rejects it. Validate adds two fail-fast guards:
unique tags (namespace collision) and a scheme-qualified url (else the source is
silently dead, never validating any login).
Foundational libraries: deterministic resource naming, the RCON client, the Postgres store with embedded SQL migrations, configuration loading, and container image-build helpers.
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