188 lines
5.6 KiB
Markdown
188 lines
5.6 KiB
Markdown
# ActivityPub federation in Mitra
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Mitra largely follows the [ActivityPub](https://www.w3.org/TR/activitypub/) server-to-server specification but it makes uses of some non-standard extensions, some of which are required for interacting with it.
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The following activities are supported:
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- Accept(Follow)
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- Reject(Follow)
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- Undo(Follow)
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- Create(Note)
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- Delete(Note)
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- Like(Note)
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- Undo(Like)
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- Announce(Note)
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- Undo(Announce)
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- Update(Note)
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- Follow(Person)
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- Update(Person)
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- Move(Person)
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- Delete(Person)
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- Add(Person)
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- Remove(Person)
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And these additional standards:
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- [Http Signatures](https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures)
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- [NodeInfo](https://nodeinfo.diaspora.software/)
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- [WebFinger](https://webfinger.net/)
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Activities are implemented in way that is compatible with Pleroma, Mastodon and other popular ActivityPub servers.
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Supported FEPs:
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- [FEP-f1d5: NodeInfo in Fediverse Software](https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-f1d5.md)
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- [FEP-e232: Object Links](https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-e232.md)
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- [FEP-8b32: Object Integrity Proofs](https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-8b32.md)
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## Object integrity proofs
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All outgoing activities are signed with actor's key in accordance with [FEP-8b32](https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-8b32.md) document.
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Example:
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```json
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{
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"@context": [
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"https://www.w3.org/ns/activitystreams",
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"https://w3id.org/security/data-integrity/v1"
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],
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"actor": "https://example.com/users/alice",
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"cc": [],
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"id": "https://example.com/objects/0185f5f8-10b5-1b69-f45e-25f06792f411",
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"object": "https://example.net/users/bob/posts/141892712081205472",
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"proof": {
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"created": "2023-01-28T01:22:40.183273595Z",
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"proofPurpose": "assertionMethod",
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"proofValue": "z5djAdMSrV...",
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"type": "MitraJcsRsaSignature2022",
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"verificationMethod": "https://example.com/users/alice#main-key"
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},
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"to": [
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"https://example.net/users/bob",
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"https://www.w3.org/ns/activitystreams#Public"
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],
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"type":"Like"
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}
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```
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### Supported proof suites
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#### MitraJcsRsaSignature2022
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Canonicalization algorithm: JCS
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Hashing algorithm: SHA-256
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Signature algorithm: RSASSA-PKCS1-v1_5
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#### MitraJcsEip191Signature2022
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Canonicalization algorithm: JCS
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Hashing algorithm: KECCAK-256 (EIP-191)
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Signature algorithm: ECDSA (EIP-191)
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#### MitraJcsEd25519Signature2022
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Canonicalization algorithm: JCS
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Hashing algorithm: BLAKE2b-512
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Signature algorithm: EdDSA
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## Custom emojis
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Custom emojis are implemented as described in Mastodon documentation: https://docs.joinmastodon.org/spec/activitypub/#emoji.
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## Profile extensions
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### Cryptocurrency addresses
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Cryptocurrency addresses are represented as `PropertyValue` attachments where `name` attribute is a currency symbol prefixed with `$`:
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```json
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{
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"name": "$XMR",
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"type": "PropertyValue",
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"value": "8Ahza5RM4JQgtdqvpcF1U628NN5Q87eryXQad3Fy581YWTZU8o3EMbtScuioQZSkyNNEEE1Lkj2cSbG4VnVYCW5L1N4os5p"
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}
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```
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### Identity proofs
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Identity proofs are represented as attachments of `IdentityProof` type:
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```json
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{
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"name": "<did>",
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"type": "IdentityProof",
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"signatureAlgorithm": "<proof-type>",
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"signatureValue": "<proof>"
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}
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```
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Supported proof types:
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- EIP-191 (Ethereum personal signatures)
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- [Minisign](https://jedisct1.github.io/minisign/)
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[FEP-c390](https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-c390.md) identity proofs are not supported yet.
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## Account migrations
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After registering an account its owner can upload the list of followers and start the migration process. The server then sends `Move` activity to each follower:
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```json
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{
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"@context": [
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"https://www.w3.org/ns/activitystreams"
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],
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"actor": "https://server2.com/users/alice",
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"id": "https://server2.com/activities/00000000-0000-0000-0000-000000000001",
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"object": "https://server1.com/users/alice",
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"target": "https://server2.com/users/alice",
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"to": [
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"https://example.com/users/bob"
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],
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"type": "Move"
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}
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```
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Where `object` is an ID of old account and `target` is an ID of new account. Actors identified by `object` and `target` properties must have at least one identity key in common to be considered aliases. Upon receipt of such activity, actors that follow `object` should un-follow it and follow `target` instead.
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## Subscription events
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Local actor profiles have `subscribers` property which points to the collection of actor's paid subscribers.
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The `Add` activity is used to notify the subscriber about successful subscription payment. Upon receipt of this activity, the receiving server should add specified `object` to actors's `subscribers` collection (specified in `target` property):
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```json
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{
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"@context": [
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"https://www.w3.org/ns/activitystreams"
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],
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"actor": "https://example.com/users/alice",
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"id": "https://example.com/activities/00000000-0000-0000-0000-000000000001",
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"object": "https://example.com/users/bob",
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"target": "https://example.com/users/alice/collections/subscribers",
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"to": [
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"https://example.com/users/bob"
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],
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"type": "Add"
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}
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```
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The `Remove` activity is used to notify the subscriber about expired subscription. Upon receipt of this activity, the receiving server should remove specified `object` from actors's `subscribers` collection (specified in `target` property):
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```json
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{
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"@context": [
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"https://www.w3.org/ns/activitystreams"
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],
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"actor": "https://example.com/users/alice",
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"id": "https://example.com/activities/00000000-0000-0000-0000-000000000002",
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"object": "https://example.com/users/bob",
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"target": "https://example.com/users/alice/collections/subscribers",
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"to": [
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"https://example.com/users/bob"
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],
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"type": "Remove"
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}
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```
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