thepraandClaude Opus 5.5
a5d9a89445
Communities: - a post addressed to a community (to, cc or audience) is accepted according to its posting policy - followers, anyone, or moderators - and GroupDistributor announces the whole activity with `audience` to the community's followers, plus the object for new posts so Mastodon shows them; updates and deletes of community content are announced too; - top-level posts are Pages with a name (the title, or a headline from the text); /flock counts members, /wardens lists moderators; - a Mastodon client posts into a community by mentioning it, or into a remote group, which sets `audience`; - an Announce of an activity from a remote group a persona follows (Lemmy) is followed through: the object is fetched from its own origin, kept with its AudienceURI, and fanned out to the group's local followers; updates are applied in place and deletes checked against the origin. Circles stop being local-only: an undiscoverable Group actor whose follows are all requests the owner approves; posts addressed to the circle and its /flock and delivered to members' own inboxes, never announced, never public; a remote member's post into the circle is accepted from members only. SignedFetchAuthorizer serves circle posts and collections only to a signed request from a member or a member server's instance actor - 404 for anyone else. Circles never surface in search, lookups, mentions, account ids or profile pages. Federation:SecureMode requires a valid signature on every GET under /peasants except the instance actor. Group forms take a posting policy. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB
120 lines
7.1 KiB
Markdown
120 lines
7.1 KiB
Markdown
# Federation
|
|
|
|
PrivaPub is an ActivityPub server written in C#. This document follows
|
|
[FEP-67ff](https://codeberg.org/fediverse/fep/src/branch/main/fep/67ff/fep-67ff.md) and describes how it federates.
|
|
|
|
## Supported federation protocols and standards
|
|
|
|
- [ActivityPub](https://www.w3.org/TR/activitypub/) (server-to-server)
|
|
- [WebFinger](https://webfinger.net/)
|
|
- [HTTP Signatures](https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures), `rsa-sha256` / `hs2019` with RSA keys
|
|
- [NodeInfo](https://nodeinfo.diaspora.software/) 2.0 and 2.1
|
|
|
|
## Supported FEPs
|
|
|
|
- [FEP-67ff: FEDERATION.md](https://codeberg.org/fediverse/fep/src/branch/main/fep/67ff/fep-67ff.md)
|
|
- [FEP-f1d5: NodeInfo in Fediverse Software](https://codeberg.org/fediverse/fep/src/branch/main/fep/f1d5/fep-f1d5.md)
|
|
- [FEP-2c59: Discovery of a WebFinger address from an ActivityPub actor](https://codeberg.org/fediverse/fep/src/branch/main/fep/2c59/fep-2c59.md)
|
|
|
|
Planned: FEP-1b12 (communities), FEP-8fcf (followers synchronisation), FEP-5feb (`indexable`), FEP-7628 (Move),
|
|
FEP-044f (quotes).
|
|
|
|
## Actors
|
|
|
|
Every account is an *avatar*: one private login can own several, and they are deliberately unlinkable. Nothing in an
|
|
actor document, a collection, NodeInfo or a delivery relates two avatars of the same login.
|
|
|
|
| Thing | Address |
|
|
|---|---|
|
|
| Actor (Person, Group, Application) | `/peasants/{name}` (`/users/{name}` redirects) |
|
|
| Inbox | `/peasants/{name}/mouth` |
|
|
| Outbox | `/peasants/{name}/anus` |
|
|
| Shared inbox | `/human-centipede` |
|
|
| Followers / following | `/peasants/{name}/groupies`, `/peasants/{name}/stalking` |
|
|
| Objects | `/peasants/{name}/scribbles/{id}` |
|
|
| Activities | `/peasants/{name}/grunts/{id}` |
|
|
| Direct-message context | `/peasants/{name}/whispers/{id}` |
|
|
| Profile and post pages | `/@{name}`, `/@{name}/{id}` |
|
|
|
|
The names are the project's own and are stable; resolve actors through WebFinger, not by guessing a path.
|
|
|
|
- The key is `{actor}#main-key`, RSA 2048, served as SPKI PEM with `owner` set to the actor.
|
|
- `published` on an actor is truncated to the day. `indexable` is `false`.
|
|
- The instance actor is `/peasants/privapub` (type `Application`). It signs every fetch PrivaPub makes, so no avatar's key
|
|
is used to read another server's content.
|
|
|
|
## Groups
|
|
|
|
A group is either a **community** or a **circle**.
|
|
|
|
- A **community** follows [FEP-1b12](https://codeberg.org/fediverse/fep/src/branch/main/fep/1b12/fep-1b12.md). Posts
|
|
addressed to it (in `to`, `cc` or `audience`) are accepted according to its posting policy (followers, anyone, or
|
|
moderators only) and the group `Announce`s the whole activity, with `audience` set, to its followers. A new post is
|
|
also announced as an object so Mastodon shows it. Updates and deletes of community content are announced too. A
|
|
top-level post is a `Page` with a `name`. Members are counted at `/flock`; moderators are listed at `/wardens`, which
|
|
`attributedTo` does not yet point to. A mention of a community posts into it.
|
|
- A **circle** is private. Its actor is not discoverable and every follow is a request. Its posts are addressed to the
|
|
circle and its members collection, delivered to each member's own inbox and never announced. They are served only
|
|
to a signed request from a member, or from the instance actor of a member's server; anyone else gets 404. A
|
|
Mastodon member's replies reach only the people they mention.
|
|
- Announces from **remote** groups (Lemmy communities) are followed through to the activity: the object is fetched
|
|
from its own origin, never taken from the announce.
|
|
|
|
## Activities
|
|
|
|
Received:
|
|
|
|
| Activity | Effect |
|
|
|---|---|
|
|
| `Follow` | follows an avatar or community; `Accept` is sent unless the community approves members by hand |
|
|
| `Accept{Follow}`, `Reject{Follow}` | completes or ends a follow an avatar requested |
|
|
| `Undo{Follow, Like, Announce}` | reverses it |
|
|
| `Create{Note, Article, Page, Question, …}` | stored when a local avatar follows the author, is addressed or mentioned, when it replies to a local post, or when it is addressed to a community the author follows; a public parent is fetched to complete the thread |
|
|
| `Update{Note}` | replaces the content; the previous version is kept |
|
|
| `Update{Person}` | refetches the actor |
|
|
| `Like` | counted and notified, on posts the liker could see |
|
|
| `Announce` | counted and notified for local posts; shown to followers of the announcer, with the original refetched from its origin |
|
|
| `Delete` | deletes the object, or the actor and its follows |
|
|
| `Flag` | becomes a report for this server's moderators |
|
|
|
|
Sent: `Follow`, `Undo{Follow}`, `Create{Note}`, `Update{Note}`, `Update{Person}`, `Delete{Tombstone}`, `Accept{Follow}`,
|
|
`Reject{Follow}`, `Like`, `Announce` and their `Undo`, `Flag`. A deleted post answers 410 with a `Tombstone`.
|
|
|
|
- **Attachments** are `Document`s with `mediaType`, `name` (alt text), `blurhash`, `focalPoint`, `width` and `height`.
|
|
Uploaded files have all metadata removed.
|
|
- **Pinned posts** are the actor's `featured` collection (`/trophies`); `featuredTags` is `/tattoos`.
|
|
- **Blocks are never sent.** A blocked account is sent `Reject{Follow}` if it followed, and is unfollowed.
|
|
- **Reports** are sent as `Flag` by the instance actor, never by the reporting account.
|
|
|
|
A `Create`'s `Note` carries Mastodon's `content`, `contentMap`, `summary` and `sensitive`, plus `Mention` and `Hashtag`
|
|
tags. A post's title becomes `name` and is also the first, bold line of `content`, because Mastodon does not show
|
|
`name`. A content warning without its own text uses the title, or "Content warning".
|
|
|
|
Visibility is expressed in `to`/`cc` the way Mastodon does it: public, unlisted, followers-only and direct. Inbound
|
|
followers-only posts are recognised by the author's own `followers` collection.
|
|
|
|
## Local-only posts
|
|
|
|
Posts with a location (shown to nearby users of this server) never leave the server, in any form.
|
|
|
|
## Security rules a peer will notice
|
|
|
|
- **Signatures.** Inbox POSTs must be signed over `(request-target)`, `host`, `digest` and `date` (or `(created)`). The
|
|
date may be at most one hour old and fifteen minutes ahead. A bad signature gets 401, malformed input 400, an accepted
|
|
activity 202, too many requests 429. Activities are processed after the 202.
|
|
- **Origins.** An actor document is accepted only from the address it names as its `id`. A key only if its actor lists
|
|
it with `owner` set to the actor and on the actor's origin. An activity's `id`, and any object it creates, updates or
|
|
deletes, must be on its actor's origin. An embedded object from another origin is fetched from that origin.
|
|
- **Fetching.** All fetches are signed by the instance actor. They go only to public addresses, follow at most three
|
|
redirects and read at most 1 MB.
|
|
- **HTML.** Received HTML is sanitised to Mastodon's allowlist.
|
|
- **Delivery.** Failed deliveries are retried with Mastodon's backoff (16 attempts). A host that keeps failing is paused,
|
|
starting at an hour and growing to a week.
|
|
|
|
## Known limitations
|
|
|
|
- Polls and custom emoji are not implemented.
|
|
- Remote media is fetched through this server's proxy when a local client displays it.
|
|
- Collections expose counts, not members.
|
|
- Only `rsa-sha256`-style keys are verified. RFC 9421 signatures are planned.
|