[feature] Support new model of interaction flow for forward compat with v0.21.0 (#4394)

~~Still WIP!~~

This PR allows v0.20.0 of GtS to be forward-compatible with the interaction request / authorization flow that will fully replace the current flow in v0.21.0.

Basically, this means we need to recognize LikeRequest, ReplyRequest, and AnnounceRequest, and in response to those requests, deliver either a Reject or an Accept, with the latter pointing towards a LikeAuthorization, ReplyAuthorization, or AnnounceAuthorization, respectively. This can then be used by the remote instance to prove to third parties that the interaction has been accepted by the interactee. These Authorization types need to be dereferencable to third parties, so we need to serve them.

As well as recognizing the above "polite" interaction request types, we also need to still serve appropriate responses to "impolite" interaction request types, where an instance that's unaware of interaction policies tries to interact with a post by sending a reply, like, or boost directly, without wrapping it in a WhateverRequest type.

Doesn't fully close https://codeberg.org/superseriousbusiness/gotosocial/issues/4026 but gets damn near (just gotta update the federating with GtS documentation).

Migrations tested on both Postgres and SQLite.

Co-authored-by: kim <grufwub@gmail.com>
Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4394
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

3 files changed, 60 insertions, 1 deletions

diff --git a/internal/api/activitypub/users/authorizationget.go b/internal/api/activitypub/users/authorizationget.go
new file mode 100644
index 000000000..a7f234854
--- /dev/null
+++ b/internal/api/activitypub/users/authorizationget.go
@@ -0,0 +1,56 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package users
+
+import (
+	"net/http"
+
+	apiutil "code.superseriousbusiness.org/gotosocial/internal/api/util"
+	"code.superseriousbusiness.org/gotosocial/internal/gtserror"
+	"github.com/gin-gonic/gin"
+)
+
+// AuthorizationGETHandler serves an accepted interaction request as a
+// LikeAuthorization, ReplyAuthorization, or AnnounceAuthorization type.
+func (m *Module) AuthorizationGETHandler(c *gin.Context) {
+	username, errWithCode := apiutil.ParseUsername(c.Param(apiutil.UsernameKey))
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	reqID, errWithCode := apiutil.ParseID(c.Param(apiutil.IDKey))
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	contentType, err := apiutil.NegotiateAccept(c, apiutil.ActivityPubHeaders...)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	resp, errWithCode := m.processor.Fedi().AuthorizationGet(c.Request.Context(), username, reqID)
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	apiutil.JSONType(c, http.StatusOK, contentType, resp)
+}
diff --git a/internal/api/activitypub/users/inboxpost_test.go b/internal/api/activitypub/users/inboxpost_test.go
index 81b21eafc..51df35672 100644
--- a/internal/api/activitypub/users/inboxpost_test.go
+++ b/internal/api/activitypub/users/inboxpost_test.go
@@ -192,7 +192,7 @@ func (suite *InboxPostTestSuite) newDelete(actorIRI string, objectIRI string, de
 
 	// Set the To of the delete as public
 	deleteTo := streams.NewActivityStreamsToProperty()
-	deleteTo.AppendIRI(ap.PublicURI())
+	deleteTo.AppendIRI(ap.PublicIRI())
 	delete.SetActivityStreamsTo(deleteTo)
 
 	// set some random-ass ID for the activity
diff --git a/internal/api/activitypub/users/user.go b/internal/api/activitypub/users/user.go
index 7a06e6f03..7fb5f6aa5 100644
--- a/internal/api/activitypub/users/user.go
+++ b/internal/api/activitypub/users/user.go
@@ -58,6 +58,8 @@ const (
 	StatusRepliesPath = StatusPath + "/replies"
 	// AcceptPath is for serving accepts of a status.
 	AcceptPath = BasePath + "/" + uris.AcceptsPath + "/:" + apiutil.IDKey
+	// AuthorizationsPath is for serving authorizations of an interaction.
+	AuthorizationsPath = BasePath + "/" + uris.AuthorizationsPath + "/:" + apiutil.IDKey
 )
 
 type Module struct {
@@ -80,4 +82,5 @@ func (m *Module) Route(attachHandler func(method string, path string, f ...gin.H
 	attachHandler(http.MethodGet, StatusRepliesPath, m.StatusRepliesGETHandler)
 	attachHandler(http.MethodGet, OutboxPath, m.OutboxGETHandler)
 	attachHandler(http.MethodGet, AcceptPath, m.AcceptGETHandler)
+	attachHandler(http.MethodGet, AuthorizationsPath, m.AuthorizationGETHandler)
 }