S1 and S2 of the roadmap. RemoteActorService:
- FetchObject accepts a document only when its id is the address it was
served from; a same-origin document naming another address is asked for
at that address once (how GoToSocial serves its key URIs), anything else
is dropped;
- GetActorByKeyId accepts a key only when the actor lists it, its owner is
the actor and it lives on the actor's origin, whether the keyId points at
the actor or at a key document;
- a refetch for a key or an actor happens at most once per five minutes,
so a bad signature cannot make us hammer a host;
- the cache row is written by one atomic upsert on ActorURI;
- every fetch is signed by the instance actor, never by the persona that
happened to receive the activity.
The inbox refuses an activity whose id is not on its actor's origin, and
an Undo of someone else's activity; a Create's object, an Update and a
Delete must be on the actor's origin too, and a cross-origin object is
refetched from its own origin before it is trusted.
Tests: a fake peer on two origins serves forged actors, foreign-owned keys,
cross-origin key documents, aliases and a GoToSocial-style key address
(integration, PRIVAPUB_TEST_MONGOD=1).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB
