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Some ActivityPub projects have a FEDERATION.md which is used to describe the various extensions they use. Everything here is also documented elsewhere, but it's a concise starting point with links to that documentation.
30 lines
1.7 KiB
Markdown
30 lines
1.7 KiB
Markdown
## ActivityPub federation in Mastodon
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Mastodon largely follows the ActivityPub server-to-server specification but it makes uses of some non-standard extensions, some of which are required for interacting with Mastodon at all.
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Supported vocabulary: https://docs.joinmastodon.org/spec/activitypub/
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### Required extensions
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#### Webfinger
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In Mastodon, users are identified by a `username` and `domain` pair (e.g., `Gargron@mastodon.social`).
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This is used both for discovery and for unambiguously mentioning users across the fediverse. Furthermore, this is part of Mastodon's database design from its very beginnings.
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As a result, Mastodon requires that each ActivityPub actor uniquely maps back to an `acct:` URI that can be resolved via WebFinger.
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More information and examples are available at: https://docs.joinmastodon.org/spec/webfinger/
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#### HTTP Signatures
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In order to authenticate activities, Mastodon relies on HTTP Signatures, signing every `POST` and `GET` request to other ActivityPub implementations on behalf of the user authoring an activity (for `POST` requests) or an actor representing the Mastodon server itself (for most `GET` requests).
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Mastodon requires all `POST` requests to be signed, and MAY require `GET` requests to be signed, depending on the configuration of the Mastodon server.
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More information on HTTP Signatures, as well as examples, can be found here: https://docs.joinmastodon.org/spec/security/#http
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### Optional extensions
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- Linked-Data Signatures: https://docs.joinmastodon.org/spec/security/#ld
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- Bearcaps: https://docs.joinmastodon.org/spec/bearcaps/
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- Followers collection synchronization: https://git.activitypub.dev/ActivityPubDev/Fediverse-Enhancement-Proposals/src/branch/main/feps/fep-8fcf.md
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