diaspora_federation/docs/federation/relayable.md

title
Relayable

If a person participates on an entity, it needs to be relayed via the author of the parent entity, because only the parent author knows, to whom they shared the original entity.

Such entities are:

• [Comment][comment]
• [Like][like]
• [PollParticipation][poll_participation]

Common Properties

All relayables have the following properties:

Property	Type	Description
author	[diaspora* ID][diaspora-id]	The diaspora* ID of the author of the relayable.
guid	[GUID][guid]	The GUID of the relayable.
parent_guid	[GUID][guid]	The GUID of the parent entity.
author_signature	[Signature][signature]	The signature from the author of the relayable.

Relaying

If the author is not the same as the parent author, the author of the relayable sends the entity to the parent author and the author must include the author_signature.

The parent author then must envelop it in a new [Magic Envelope][magicsig] and send the entity to all the recipients of the parent entity. If the author and the parent author are on the same server, the author must sign the author_signature and the parent author needs to sign the Magic Envelope.

If someone other then the parent author receives a relayable without a valid Magic Envelope signed from the parent author, it must be ignored. If the author is not the same as the parent author and the author_signature is missing or invalid, it also must be ignored. If the author is the same as the parent author, the author_signature can be missing, because a valid signature in the Magic Envelope from the author is enough in that case.

Signatures

The string to sign is built with the content of all properties (except the author_signature itself), concatenated using ; as separator in the same order as they appear in the XML. The order in the XML is not specified.

This ensures that relayables even work, if the parent author or another recipient does not know all properties of the relayable entity (e.g. older version of diaspora*).

This string is then signed with the private RSA key using the RSA-SHA256 algorithm and base64-encoded.

The parent author must use the same order as the relayable author. Unknown properties must be included again in the XML and the signature.

To support fetching of the relayables, the parent author should save the following information:

• order of the received XML
• additional (unknown) properties
• author_signature

Retraction / Reject

The parent author is allowed to retract the entity, so there are no additional signatures required for the [Retraction][retraction] (only the [Salmon Magic Signature][magicsig]).

If the author retracts the entity, they send a [Retraction][retraction] to the parent author. The parent author also must relay this retraction to all recipients of the parent entity.

If the parent author wants to reject the entity (e.g. if they ignore the author of the relayable), they can simply send a [Retraction][retraction] for it back to the author.

[diaspora-id]: {{ site.baseurl }}/federation/types.html#diaspora-id [guid]: {{ site.baseurl }}/federation/types.html#guid [signature]: {{ site.baseurl }}/federation/types.html#signature [comment]: {{ site.baseurl }}/entities/comment.html [like]: {{ site.baseurl }}/entities/like.html [poll_participation]: {{ site.baseurl }}/entities/poll_participation.html [retraction]: {{ site.baseurl }}/entities/retraction.html [magicsig]: {{ site.baseurl }}/federation/magicsig.html