[bugfix] Federate status delete using just the URI (#1584)

docs/federation/federating_with_gotosocial.md

@@ -267,3 +267,58 @@ Some of the URIs served as part of the collection may point to followers-only po
 Another difference between GoToSocial and other server implementations is that GoToSocial does not send updates to remote servers when a post is pinned or unpinned by a user. Mastodon does this by sending [Add](https://www.w3.org/TR/activitypub/#add-activity-inbox) and [Remove](https://www.w3.org/TR/activitypub/#remove-activity-inbox) Activity types where the `object` is the post being pinned or unpinned, and the `target` is the sending `Actor`'s `featured` collection. While this conceptually makes sense, it is not in line with what the ActivityPub protocol recommends, since the `target` of the Activity "is not owned by the receiving server, and thus they can't update it".
 
 Instead, to build a view of a GoToSocial user's pinned posts, it is recommended that remote instances simply poll a GoToSocial Actor's `featured` collection every so often, and add/remove posts in their cached representation as appropriate.
+
+## Post Deletes
+
+GoToSocial allows users to delete posts that they have created. These deletes will be federated out to other instances, which are expected to also delete their local cache of the post.
+
+### Outgoing
+
+When a post is deleted by a GoToSocial user, the server will send a `Delete` activity out to other instances.
+
+The `Delete` will have the ActivityPub URI of the post set as the value of the `Object` entry.
+
+`to` and `cc` will be set according to the visibility of the original post, and any users mentioned/replied to by the original post.
+
+If the original post was not a direct message, the ActivityPub `Public` URI will be addressed in `to`. Otherwise, only mentioned and replied to users will be addressed.
+
+In the following example, the 'admin' user deletes a public post of theirs in which the 'foss_satan' user was mentioned:
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://example.org/users/admin",
+  "cc": [
+    "http://example.org/users/admin/followers",
+    "http://fossbros-anonymous.io/users/foss_satan"
+  ],
+  "object": "http://example.org/users/admin/statuses/01FF25D5Q0DH7CHD57CTRS6WK0",
+  "to": "https://www.w3.org/ns/activitystreams#Public",
+  "type": "Delete"
+}
+```
+
+In the next example, the '1happyturtle' user deletes a direct message which was originally addressed to the 'the_mighty_zork' user.
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://example.org/users/1happyturtle",
+  "cc": [],
+  "object": "http://example.org/users/1happyturtle/statuses/01FN3VJGFH10KR7S2PB0GFJZYG",
+  "to": "http://somewhere.com/users/the_mighty_zork",
+  "type": "Delete"
+}
+```
+
+To process a `Delete` activity coming from a GoToSocial instance, remote instances should check if they have the `Object` stored according to the provided URI. If they do, they should remove it from their local cache. If not, then no action is required, since they never had the now-deleted post stored in the first place.
+
+### Incoming
+
+GoToSocial processes `Delete` activities coming in from remote instances as thoroughly as possible in order to respect the privacy of other users.
+
+When a GoToSocial instance receives a `Delete`, it will attempt to derive the deleted post URI from the `Object` field. If the `Object` is just a URI, then this URI will be taken. If the `Object` is a `Note` or another type commonly used to represent a post, then the URI will be extracted from it.
+
+Then, GoToSocial will check if it has a post stored with the given URI. If it does, it will be completely deleted from the database and all user timelines.
+
+GoToSocial will only delete a post if it can be sure that the original post was owned by the `actor` that the `Delete` is attributed to.

internal/processing/fromclientapi.go

@@ -467,38 +467,16 @@ func (p *Processor) federateStatusDelete(ctx context.Context, status *gtsmodel.S
 		return nil
 	}
 
-	asStatus, err := p.tc.StatusToAS(ctx, status)
+	delete, err := p.tc.StatusToASDelete(ctx, status)
 	if err != nil {
-		return fmt.Errorf("federateStatusDelete: error converting status to as format: %s", err)
+		return fmt.Errorf("federateStatusDelete: error creating Delete: %w", err)
 	}
 
 	outboxIRI, err := url.Parse(status.Account.OutboxURI)
 	if err != nil {
-		return fmt.Errorf("federateStatusDelete: error parsing outboxURI %s: %s", status.Account.OutboxURI, err)
+		return fmt.Errorf("federateStatusDelete: error parsing outboxURI %s: %w", status.Account.OutboxURI, err)
 	}
 
-	actorIRI, err := url.Parse(status.Account.URI)
-	if err != nil {
-		return fmt.Errorf("federateStatusDelete: error parsing actorIRI %s: %s", status.Account.URI, err)
-	}
-
-	// create a delete and set the appropriate actor on it
-	delete := streams.NewActivityStreamsDelete()
-
-	// set the actor for the delete
-	deleteActor := streams.NewActivityStreamsActorProperty()
-	deleteActor.AppendIRI(actorIRI)
-	delete.SetActivityStreamsActor(deleteActor)
-
-	// Set the status as the 'object' property.
-	deleteObject := streams.NewActivityStreamsObjectProperty()
-	deleteObject.AppendActivityStreamsNote(asStatus)
-	delete.SetActivityStreamsObject(deleteObject)
-
-	// set the to and cc as the original to/cc of the original status
-	delete.SetActivityStreamsTo(asStatus.GetActivityStreamsTo())
-	delete.SetActivityStreamsCc(asStatus.GetActivityStreamsCc())
-
 	_, err = p.federator.FederatingActor().Send(ctx, outboxIRI, delete)
 	return err
 }

internal/typeutils/converter.go

@@ -148,6 +148,9 @@ type TypeConverter interface {
 	AccountToASMinimal(ctx context.Context, a *gtsmodel.Account) (vocab.ActivityStreamsPerson, error)
 	// StatusToAS converts a gts model status into an activity streams note, suitable for federation
 	StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.ActivityStreamsNote, error)
+	// StatusToASDelete converts a gts model status into a Delete of that status, using just the
+	// URI of the status as object, and addressing the Delete appropriately.
+	StatusToASDelete(ctx context.Context, status *gtsmodel.Status) (vocab.ActivityStreamsDelete, error)
 	// FollowToASFollow converts a gts model Follow into an activity streams Follow, suitable for federation
 	FollowToAS(ctx context.Context, f *gtsmodel.Follow, originAccount *gtsmodel.Account, targetAccount *gtsmodel.Account) (vocab.ActivityStreamsFollow, error)
 	// MentionToAS converts a gts model mention into an activity streams Mention, suitable for federation

internal/typeutils/converter_test.go

@@ -477,6 +477,7 @@ type TypeUtilsTestSuite struct {
 	testPeople      map[string]vocab.ActivityStreamsPerson
 	testEmojis      map[string]*gtsmodel.Emoji
 	testReports     map[string]*gtsmodel.Report
+	testMentions    map[string]*gtsmodel.Mention
 
 	typeconverter typeutils.TypeConverter
 }
@@ -495,6 +496,7 @@ func (suite *TypeUtilsTestSuite) SetupSuite() {
 	suite.testPeople = testrig.NewTestFediPeople()
 	suite.testEmojis = testrig.NewTestEmojis()
 	suite.testReports = testrig.NewTestReports()
+	suite.testMentions = testrig.NewTestMentions()
 	suite.typeconverter = typeutils.NewConverter(suite.db)
 }
 

internal/typeutils/internaltoas.go

@@ -22,6 +22,7 @@
 	"context"
 	"crypto/x509"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"net/url"
 
@@ -29,6 +30,7 @@
 	"github.com/superseriousbusiness/activity/streams"
 	"github.com/superseriousbusiness/activity/streams/vocab"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
@@ -414,18 +416,10 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 	status.SetActivityStreamsSummary(statusSummaryProp)
 
 	// inReplyTo
-	if s.InReplyToID != "" {
+	if s.InReplyToURI != "" {
-		// fetch the replied status if we don't have it on hand already
+		rURI, err := url.Parse(s.InReplyToURI)
-		if s.InReplyTo == nil {
-			rs, err := c.db.GetStatusByID(ctx, s.InReplyToID)
-			if err != nil {
-				return nil, fmt.Errorf("StatusToAS: error getting replied to status %s: %s", s.InReplyToID, err)
-			}
-			s.InReplyTo = rs
-		}
-		rURI, err := url.Parse(s.InReplyTo.URI)
 		if err != nil {
-			return nil, fmt.Errorf("StatusToAS: error parsing url %s: %s", s.InReplyTo.URI, err)
+			return nil, fmt.Errorf("StatusToAS: error parsing url %s: %s", s.InReplyToURI, err)
 		}
 
 		inReplyToProp := streams.NewActivityStreamsInReplyToProperty()
@@ -465,13 +459,9 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 	// tag -- mentions
 	mentions := s.Mentions
 	if len(s.MentionIDs) > len(mentions) {
-		mentions = []*gtsmodel.Mention{}
+		mentions, err = c.db.GetMentions(ctx, s.MentionIDs)
-		for _, mentionID := range s.MentionIDs {
+		if err != nil {
-			mention, err := c.db.GetMention(ctx, mentionID)
+			return nil, fmt.Errorf("StatusToAS: error getting mentions: %w", err)
-			if err != nil {
-				return nil, fmt.Errorf("StatusToAS: error getting mention %s from database: %s", mentionID, err)
-			}
-			mentions = append(mentions, mention)
 		}
 	}
 	for _, m := range mentions {
@@ -524,7 +514,7 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 	switch s.Visibility {
 	case gtsmodel.VisibilityDirect:
 		// if DIRECT, then only mentioned users should be added to TO, and nothing to CC
-		for _, m := range s.Mentions {
+		for _, m := range mentions {
 			iri, err := url.Parse(m.TargetAccount.URI)
 			if err != nil {
 				return nil, fmt.Errorf("StatusToAS: error parsing uri %s: %s", m.TargetAccount.URI, err)
@@ -536,7 +526,7 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 	case gtsmodel.VisibilityFollowersOnly:
 		// if FOLLOWERS ONLY then we want to add followers to TO, and mentions to CC
 		toProp.AppendIRI(authorFollowersURI)
-		for _, m := range s.Mentions {
+		for _, m := range mentions {
 			iri, err := url.Parse(m.TargetAccount.URI)
 			if err != nil {
 				return nil, fmt.Errorf("StatusToAS: error parsing uri %s: %s", m.TargetAccount.URI, err)
@@ -547,7 +537,7 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 		// if UNLOCKED, we want to add followers to TO, and public and mentions to CC
 		toProp.AppendIRI(authorFollowersURI)
 		ccProp.AppendIRI(publicURI)
-		for _, m := range s.Mentions {
+		for _, m := range mentions {
 			iri, err := url.Parse(m.TargetAccount.URI)
 			if err != nil {
 				return nil, fmt.Errorf("StatusToAS: error parsing uri %s: %s", m.TargetAccount.URI, err)
@@ -558,7 +548,7 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 		// if PUBLIC, we want to add public to TO, and followers and mentions to CC
 		toProp.AppendIRI(publicURI)
 		ccProp.AppendIRI(authorFollowersURI)
-		for _, m := range s.Mentions {
+		for _, m := range mentions {
 			iri, err := url.Parse(m.TargetAccount.URI)
 			if err != nil {
 				return nil, fmt.Errorf("StatusToAS: error parsing uri %s: %s", m.TargetAccount.URI, err)
@@ -617,6 +607,141 @@ func (c *converter) StatusToAS(ctx context.Context, s *gtsmodel.Status) (vocab.A
 	return status, nil
 }
 
+func (c *converter) StatusToASDelete(ctx context.Context, s *gtsmodel.Status) (vocab.ActivityStreamsDelete, error) {
+	// Parse / fetch some information
+	// we need to create the Delete.
+
+	if s.Account == nil {
+		var err error
+		s.Account, err = c.db.GetAccountByID(ctx, s.AccountID)
+		if err != nil {
+			return nil, fmt.Errorf("StatusToASDelete: error retrieving author account from db: %w", err)
+		}
+	}
+
+	actorIRI, err := url.Parse(s.AccountURI)
+	if err != nil {
+		return nil, fmt.Errorf("StatusToASDelete: error parsing actorIRI %s: %w", s.AccountURI, err)
+	}
+
+	statusIRI, err := url.Parse(s.URI)
+	if err != nil {
+		return nil, fmt.Errorf("StatusToASDelete: error parsing statusIRI %s: %w", s.URI, err)
+	}
+
+	// Create a Delete.
+	delete := streams.NewActivityStreamsDelete()
+
+	// Set appropriate actor for the Delete.
+	deleteActor := streams.NewActivityStreamsActorProperty()
+	deleteActor.AppendIRI(actorIRI)
+	delete.SetActivityStreamsActor(deleteActor)
+
+	// Set the status IRI as the 'object' property.
+	// We should avoid serializing the whole status
+	// when doing a delete because it's wasteful and
+	// could accidentally leak the now-deleted status.
+	deleteObject := streams.NewActivityStreamsObjectProperty()
+	deleteObject.AppendIRI(statusIRI)
+	delete.SetActivityStreamsObject(deleteObject)
+
+	// Address the Delete appropriately.
+	toProp := streams.NewActivityStreamsToProperty()
+	ccProp := streams.NewActivityStreamsCcProperty()
+
+	// Unless the status was a direct message, we can
+	// address the Delete To the ActivityPub Public URI.
+	// This ensures that the Delete will have as wide an
+	// audience as possible.
+	//
+	// Because we're using just the status URI, not the
+	// whole status, it won't leak any sensitive info.
+	// At worst, a remote instance becomes aware of the
+	// URI for a status which is now deleted anyway.
+	if s.Visibility != gtsmodel.VisibilityDirect {
+		publicURI, err := url.Parse(pub.PublicActivityPubIRI)
+		if err != nil {
+			return nil, fmt.Errorf("StatusToASDelete: error parsing url %s: %w", pub.PublicActivityPubIRI, err)
+		}
+		toProp.AppendIRI(publicURI)
+
+		actorFollowersURI, err := url.Parse(s.Account.FollowersURI)
+		if err != nil {
+			return nil, fmt.Errorf("StatusToASDelete: error parsing url %s: %w", s.Account.FollowersURI, err)
+		}
+		ccProp.AppendIRI(actorFollowersURI)
+	}
+
+	// Always include the replied-to account and any
+	// mentioned accounts as addressees as well.
+	//
+	// Worst case scenario here is that a replied account
+	// who wasn't mentioned (and perhaps didn't see the
+	// message), sees that someone has now deleted a status
+	// in which they were replied to but not mentioned. In
+	// other words, they *might* see that someone subtooted
+	// about them, but they won't know what was said.
+
+	// Ensure mentions are populated.
+	mentions := s.Mentions
+	if len(s.MentionIDs) > len(mentions) {
+		mentions, err = c.db.GetMentions(ctx, s.MentionIDs)
+		if err != nil {
+			return nil, fmt.Errorf("StatusToASDelete: error getting mentions: %w", err)
+		}
+	}
+
+	// Remember which accounts were mentioned
+	// here to avoid duplicating them later.
+	mentionedAccountIDs := make(map[string]interface{}, len(mentions))
+
+	// For direct messages, add URI
+	// to To, else just add to CC.
+	var f func(v *url.URL)
+	if s.Visibility == gtsmodel.VisibilityDirect {
+		f = toProp.AppendIRI
+	} else {
+		f = ccProp.AppendIRI
+	}
+
+	for _, m := range mentions {
+		mentionedAccountIDs[m.TargetAccountID] = nil // Remember this ID.
+
+		iri, err := url.Parse(m.TargetAccount.URI)
+		if err != nil {
+			return nil, fmt.Errorf("StatusToAS: error parsing uri %s: %s", m.TargetAccount.URI, err)
+		}
+
+		f(iri)
+	}
+
+	if s.InReplyToAccountID != "" {
+		if _, ok := mentionedAccountIDs[s.InReplyToAccountID]; !ok {
+			// Only address to this account if it
+			// wasn't already included as a mention.
+			if s.InReplyToAccount == nil {
+				s.InReplyToAccount, err = c.db.GetAccountByID(ctx, s.InReplyToAccountID)
+				if err != nil && !errors.Is(err, db.ErrNoEntries) {
+					return nil, fmt.Errorf("StatusToASDelete: db error getting account %s: %w", s.InReplyToAccountID, err)
+				}
+			}
+
+			if s.InReplyToAccount != nil {
+				inReplyToAccountURI, err := url.Parse(s.InReplyToAccount.URI)
+				if err != nil {
+					return nil, fmt.Errorf("StatusToASDelete: error parsing url %s: %w", s.InReplyToAccount.URI, err)
+				}
+				ccProp.AppendIRI(inReplyToAccountURI)
+			}
+		}
+	}
+
+	delete.SetActivityStreamsTo(toProp)
+	delete.SetActivityStreamsCc(ccProp)
+
+	return delete, nil
+}
+
 func (c *converter) FollowToAS(ctx context.Context, f *gtsmodel.Follow, originAccount *gtsmodel.Account, targetAccount *gtsmodel.Account) (vocab.ActivityStreamsFollow, error) {
 	// parse out the various URIs we need for this
 	// origin account (who's doing the follow)

internal/typeutils/internaltoas_test.go

@@ -430,6 +430,116 @@ func (suite *InternalToASTestSuite) TestStatusToASWithMentions() {
 }`, string(bytes))
 }
 
+func (suite *InternalToASTestSuite) TestStatusToASDeletePublicReply() {
+	testStatus := suite.testStatuses["admin_account_status_3"]
+	ctx := context.Background()
+
+	asDelete, err := suite.typeconverter.StatusToASDelete(ctx, testStatus)
+	suite.NoError(err)
+
+	ser, err := streams.Serialize(asDelete)
+	suite.NoError(err)
+
+	bytes, err := json.MarshalIndent(ser, "", "  ")
+	suite.NoError(err)
+
+	suite.Equal(`{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://localhost:8080/users/admin",
+  "cc": [
+    "http://localhost:8080/users/admin/followers",
+    "http://localhost:8080/users/the_mighty_zork"
+  ],
+  "object": "http://localhost:8080/users/admin/statuses/01FF25D5Q0DH7CHD57CTRS6WK0",
+  "to": "https://www.w3.org/ns/activitystreams#Public",
+  "type": "Delete"
+}`, string(bytes))
+}
+
+func (suite *InternalToASTestSuite) TestStatusToASDeletePublicReplyOriginalDeleted() {
+	testStatus := suite.testStatuses["admin_account_status_3"]
+	ctx := context.Background()
+
+  // Delete the status this replies to.
+  if err := suite.db.DeleteStatusByID(ctx, testStatus.ID); err != nil {
+    suite.FailNow(err.Error())
+  }
+
+  // Delete the mention the reply created.
+  mention := suite.testMentions["admin_account_mention_zork"]
+  if err := suite.db.DeleteByID(ctx, mention.ID, mention); err != nil {
+    suite.FailNow(err.Error())
+  }
+
+  // The delete should still be created OK.
+	asDelete, err := suite.typeconverter.StatusToASDelete(ctx, testStatus)
+	suite.NoError(err)
+
+	ser, err := streams.Serialize(asDelete)
+	suite.NoError(err)
+
+	bytes, err := json.MarshalIndent(ser, "", "  ")
+	suite.NoError(err)
+
+	suite.Equal(`{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://localhost:8080/users/admin",
+  "cc": [
+    "http://localhost:8080/users/admin/followers",
+    "http://localhost:8080/users/the_mighty_zork"
+  ],
+  "object": "http://localhost:8080/users/admin/statuses/01FF25D5Q0DH7CHD57CTRS6WK0",
+  "to": "https://www.w3.org/ns/activitystreams#Public",
+  "type": "Delete"
+}`, string(bytes))
+}
+
+func (suite *InternalToASTestSuite) TestStatusToASDeletePublic() {
+	testStatus := suite.testStatuses["admin_account_status_1"]
+	ctx := context.Background()
+
+	asDelete, err := suite.typeconverter.StatusToASDelete(ctx, testStatus)
+	suite.NoError(err)
+
+	ser, err := streams.Serialize(asDelete)
+	suite.NoError(err)
+
+	bytes, err := json.MarshalIndent(ser, "", "  ")
+	suite.NoError(err)
+
+	suite.Equal(`{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://localhost:8080/users/admin",
+  "cc": "http://localhost:8080/users/admin/followers",
+  "object": "http://localhost:8080/users/admin/statuses/01F8MH75CBF9JFX4ZAD54N0W0R",
+  "to": "https://www.w3.org/ns/activitystreams#Public",
+  "type": "Delete"
+}`, string(bytes))
+}
+
+func (suite *InternalToASTestSuite) TestStatusToASDeleteDirectMessage() {
+	testStatus := suite.testStatuses["local_account_2_status_6"]
+	ctx := context.Background()
+
+	asDelete, err := suite.typeconverter.StatusToASDelete(ctx, testStatus)
+	suite.NoError(err)
+
+	ser, err := streams.Serialize(asDelete)
+	suite.NoError(err)
+
+	bytes, err := json.MarshalIndent(ser, "", "  ")
+	suite.NoError(err)
+
+	suite.Equal(`{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "actor": "http://localhost:8080/users/1happyturtle",
+  "cc": [],
+  "object": "http://localhost:8080/users/1happyturtle/statuses/01FN3VJGFH10KR7S2PB0GFJZYG",
+  "to": "http://localhost:8080/users/the_mighty_zork",
+  "type": "Delete"
+}`, string(bytes))
+}
+
 func (suite *InternalToASTestSuite) TestStatusesToASOutboxPage() {
 	testAccount := suite.testAccounts["admin_account"]
 	ctx := context.Background()