ActivityPub integration

[julianlam]

This pull requests adds ActivityPub integration into NodeBB. It is not meant to be completely exhaustive, but mostly a proof-of-concept integration that will be improved over time.

For example:

• while there is probably a way to integrate groups into the ActivityPub (Friendica has done this I believe?) protocol, that would be beyond the scope of this initial implementation.
• visibility scope can theoretically be used to integrate ActivityPub with NodeBB chats. This is also beyond the initial scope.

High Level Items

• /.well-known/webfinger implementation
• Admin control switch to disable federation
• Ability to view user profiles on remote/federated instances
• Can follow users from another instance, and an accept is automatically sent back (as NodeBB does not have the capability to accept/reject follow requests)
• Unfollow a user on another instance
• User followers and followed (AP responses)
• HTTP signature verification and signing (for inboxes and outboxes respectively)
• User inboxes (POST only) and outboxes (GET only)
• JIT generation of RSA keys (signing outbox items)
• ActivityPub verbs
  • Create
  • Update
  • Delete
  • Follow
  • Accept
• Posts are automatically sent to follower inboxes (and those mentioned)
• Replies (ActivityPub notes) received in user inboxes are parsed and added to topics
• Likewise, edits are propagated similarly
• Likewise, deletions are propagated similarly
• ... TBD...

Associated branches

In addition to the activitypub branch, the following plugins also have corresponding activitypub branches, which are necessary for proper functionality:

1. nodebb-theme-harmony introduces world.tpl
2. nodebb-plugin-markdown introduces logic that skips parsing if content is remote (unless it contains sourceContent in post hash)

Breaking Changes

• [tbd] introduces a change to plugin hooks filter:user.following and filter:user.followers. The uids property used to pass in local uids (aka numbers) but can now contain remote actor uris (strings).

Useful resources

• How to implement a basic ActivityPub server
• Tutorial: A simple FediVerse Server
• ActivityPub Implementation test suite via @bengo@mastodon.social

[nodebb-misty]

💡 Friendly Note

This pull request was made against the develop branch, which is reserved for commits destined for a minor or major release.If your commits simply fixes a bug, please rebase this PR against the master instead.

• patch releases — bug fixes only
• minor releases — new features, enhancements, and bug fixes
• major releases — breaking changes, including all of the above

Thanks!

[julianlam]

As per @helge@mymath.rocks, only a limited subject of ActivityPub verbs needs be implemented for basic federation functionality. I will use those now as the benchmark for completion of this PR.

[julianlam]

It seems that GETting from an inbox and POSTing to an outbox are client-to-server actions, which I don't see a need to support for now.

I have updated the original issue to only specify POSTing to an inbox and GETting from an outbox.

[bil-ash]

Seems this PR has made much progress. Any ETA about when this will be merged?