Handle guest access [1/2?] (#2872)

Needs https://github.com/matrix-org/sytest/pull/1315, as otherwise the
membership events aren't persisted yet when hitting `/state` after
kicking guest users.

Makes the following tests pass:
```
Guest users denied access over federation if guest access prohibited
Guest users are kicked from guest_access rooms on revocation of guest_access
Guest users are kicked from guest_access rooms on revocation of guest_access over federation
```

Todo (in a follow up PR):
- Restrict access to CS API Endpoints as per
https://spec.matrix.org/v1.4/client-server-api/#client-behaviour-14

Co-authored-by: kegsay <kegan@matrix.org>

6 files changed, 258 insertions, 34 deletions

diff --git a/roomserver/api/perform.go b/roomserver/api/perform.go
index e70e5ea9..e789b956 100644
--- a/roomserver/api/perform.go
+++ b/roomserver/api/perform.go
@@ -78,6 +78,7 @@ const (
 type PerformJoinRequest struct {
 	RoomIDOrAlias string                         `json:"room_id_or_alias"`
 	UserID        string                         `json:"user_id"`
+	IsGuest       bool                           `json:"is_guest"`
 	Content       map[string]interface{}         `json:"content"`
 	ServerNames   []gomatrixserverlib.ServerName `json:"server_names"`
 	Unsigned      map[string]interface{}         `json:"unsigned"`
diff --git a/roomserver/internal/api.go b/roomserver/internal/api.go
index 1a362660..451b3769 100644
--- a/roomserver/internal/api.go
+++ b/roomserver/internal/api.go
@@ -4,6 +4,10 @@ import (
 	"context"
 
 	"github.com/getsentry/sentry-go"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/nats-io/nats.go"
+	"github.com/sirupsen/logrus"
+
 	asAPI "github.com/matrix-org/dendrite/appservice/api"
 	fsAPI "github.com/matrix-org/dendrite/federationapi/api"
 	"github.com/matrix-org/dendrite/internal/caching"
@@ -19,9 +23,6 @@ import (
 	"github.com/matrix-org/dendrite/setup/jetstream"
 	"github.com/matrix-org/dendrite/setup/process"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
-	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/nats-io/nats.go"
-	"github.com/sirupsen/logrus"
 )
 
 // RoomserverInternalAPI is an implementation of api.RoomserverInternalAPI
@@ -104,6 +105,11 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 	r.fsAPI = fsAPI
 	r.KeyRing = keyRing
 
+	identity, err := r.Cfg.Matrix.SigningIdentityFor(r.ServerName)
+	if err != nil {
+		logrus.Panic(err)
+	}
+
 	r.Inputer = &input.Inputer{
 		Cfg:                 &r.Base.Cfg.RoomServer,
 		Base:                r.Base,
@@ -114,7 +120,8 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 		JetStream:           r.JetStream,
 		NATSClient:          r.NATSClient,
 		Durable:             nats.Durable(r.Durable),
-		ServerName:          r.Cfg.Matrix.ServerName,
+		ServerName:          r.ServerName,
+		SigningIdentity:     identity,
 		FSAPI:               fsAPI,
 		KeyRing:             keyRing,
 		ACLs:                r.ServerACLs,
@@ -135,7 +142,7 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 		Queryer: r.Queryer,
 	}
 	r.Peeker = &perform.Peeker{
-		ServerName: r.Cfg.Matrix.ServerName,
+		ServerName: r.ServerName,
 		Cfg:        r.Cfg,
 		DB:         r.DB,
 		FSAPI:      r.fsAPI,
@@ -146,7 +153,7 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 		Inputer: r.Inputer,
 	}
 	r.Unpeeker = &perform.Unpeeker{
-		ServerName: r.Cfg.Matrix.ServerName,
+		ServerName: r.ServerName,
 		Cfg:        r.Cfg,
 		DB:         r.DB,
 		FSAPI:      r.fsAPI,
@@ -193,6 +200,7 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 
 func (r *RoomserverInternalAPI) SetUserAPI(userAPI userapi.RoomserverUserAPI) {
 	r.Leaver.UserAPI = userAPI
+	r.Inputer.UserAPI = userAPI
 }
 
 func (r *RoomserverInternalAPI) SetAppserviceAPI(asAPI asAPI.AppServiceInternalAPI) {
diff --git a/roomserver/internal/input/input.go b/roomserver/internal/input/input.go
index e965691c..94131103 100644
--- a/roomserver/internal/input/input.go
+++ b/roomserver/internal/input/input.go
@@ -23,6 +23,8 @@ import (
 	"sync"
 	"time"
 
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+
 	"github.com/Arceliar/phony"
 	"github.com/getsentry/sentry-go"
 	"github.com/matrix-org/gomatrixserverlib"
@@ -79,6 +81,7 @@ type Inputer struct {
 	JetStream           nats.JetStreamContext
 	Durable             nats.SubOpt
 	ServerName          gomatrixserverlib.ServerName
+	SigningIdentity     *gomatrixserverlib.SigningIdentity
 	FSAPI               fedapi.RoomserverFederationAPI
 	KeyRing             gomatrixserverlib.JSONVerifier
 	ACLs                *acls.ServerACLs
@@ -87,6 +90,7 @@ type Inputer struct {
 	workers             sync.Map // room ID -> *worker
 
 	Queryer *query.Queryer
+	UserAPI userapi.RoomserverUserAPI
 }
 
 // If a room consumer is inactive for a while then we will allow NATS
diff --git a/roomserver/internal/input/input_events.go b/roomserver/internal/input/input_events.go
index 10b8ee27..4179fc1e 100644
--- a/roomserver/internal/input/input_events.go
+++ b/roomserver/internal/input/input_events.go
@@ -19,6 +19,7 @@ package input
 import (
 	"context"
 	"database/sql"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"time"
@@ -31,6 +32,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/sirupsen/logrus"
 
+	userAPI "github.com/matrix-org/dendrite/userapi/api"
+
 	fedapi "github.com/matrix-org/dendrite/federationapi/api"
 	"github.com/matrix-org/dendrite/internal"
 	"github.com/matrix-org/dendrite/internal/eventutil"
@@ -440,6 +443,13 @@ func (r *Inputer) processRoomEvent(
 		}
 	}
 
+	// If guest_access changed and is not can_join, kick all guest users.
+	if event.Type() == gomatrixserverlib.MRoomGuestAccess && gjson.GetBytes(event.Content(), "guest_access").Str != "can_join" {
+		if err = r.kickGuests(ctx, event, roomInfo); err != nil {
+			logrus.WithError(err).Error("failed to kick guest users on m.room.guest_access revocation")
+		}
+	}
+
 	// Everything was OK — the latest events updater didn't error and
 	// we've sent output events. Finally, generate a hook call.
 	hooks.Run(hooks.KindNewEventPersisted, headered)
@@ -729,3 +739,98 @@ func (r *Inputer) calculateAndSetState(
 	succeeded = true
 	return nil
 }
+
+// kickGuests kicks guests users from m.room.guest_access rooms, if guest access is now prohibited.
+func (r *Inputer) kickGuests(ctx context.Context, event *gomatrixserverlib.Event, roomInfo *types.RoomInfo) error {
+	membershipNIDs, err := r.DB.GetMembershipEventNIDsForRoom(ctx, roomInfo.RoomNID, true, true)
+	if err != nil {
+		return err
+	}
+
+	memberEvents, err := r.DB.Events(ctx, membershipNIDs)
+	if err != nil {
+		return err
+	}
+
+	inputEvents := make([]api.InputRoomEvent, 0, len(memberEvents))
+	latestReq := &api.QueryLatestEventsAndStateRequest{
+		RoomID: event.RoomID(),
+	}
+	latestRes := &api.QueryLatestEventsAndStateResponse{}
+	if err = r.Queryer.QueryLatestEventsAndState(ctx, latestReq, latestRes); err != nil {
+		return err
+	}
+
+	prevEvents := latestRes.LatestEvents
+	for _, memberEvent := range memberEvents {
+		if memberEvent.StateKey() == nil {
+			continue
+		}
+
+		localpart, senderDomain, err := gomatrixserverlib.SplitID('@', *memberEvent.StateKey())
+		if err != nil {
+			continue
+		}
+
+		accountRes := &userAPI.QueryAccountByLocalpartResponse{}
+		if err = r.UserAPI.QueryAccountByLocalpart(ctx, &userAPI.QueryAccountByLocalpartRequest{
+			Localpart:  localpart,
+			ServerName: senderDomain,
+		}, accountRes); err != nil {
+			return err
+		}
+		if accountRes.Account == nil {
+			continue
+		}
+
+		if accountRes.Account.AccountType != userAPI.AccountTypeGuest {
+			continue
+		}
+
+		var memberContent gomatrixserverlib.MemberContent
+		if err = json.Unmarshal(memberEvent.Content(), &memberContent); err != nil {
+			return err
+		}
+		memberContent.Membership = gomatrixserverlib.Leave
+
+		stateKey := *memberEvent.StateKey()
+		fledglingEvent := &gomatrixserverlib.EventBuilder{
+			RoomID:     event.RoomID(),
+			Type:       gomatrixserverlib.MRoomMember,
+			StateKey:   &stateKey,
+			Sender:     stateKey,
+			PrevEvents: prevEvents,
+		}
+
+		if fledglingEvent.Content, err = json.Marshal(memberContent); err != nil {
+			return err
+		}
+
+		eventsNeeded, err := gomatrixserverlib.StateNeededForEventBuilder(fledglingEvent)
+		if err != nil {
+			return err
+		}
+
+		event, err := eventutil.BuildEvent(ctx, fledglingEvent, r.Cfg.Matrix, r.SigningIdentity, time.Now(), &eventsNeeded, latestRes)
+		if err != nil {
+			return err
+		}
+
+		inputEvents = append(inputEvents, api.InputRoomEvent{
+			Kind:         api.KindNew,
+			Event:        event,
+			Origin:       senderDomain,
+			SendAsServer: string(senderDomain),
+		})
+		prevEvents = []gomatrixserverlib.EventReference{
+			event.EventReference(),
+		}
+	}
+
+	inputReq := &api.InputRoomEventsRequest{
+		InputRoomEvents: inputEvents,
+		Asynchronous:    true, // Needs to be async, as we otherwise create a deadlock
+	}
+	inputRes := &api.InputRoomEventsResponse{}
+	return r.InputRoomEvents(ctx, inputReq, inputRes)
+}
diff --git a/roomserver/internal/perform/perform_join.go b/roomserver/internal/perform/perform_join.go
index 4de008c6..fc7ba940 100644
--- a/roomserver/internal/perform/perform_join.go
+++ b/roomserver/internal/perform/perform_join.go
@@ -16,6 +16,7 @@ package perform
 
 import (
 	"context"
+	"database/sql"
 	"errors"
 	"fmt"
 	"strings"
@@ -270,6 +271,28 @@ func (r *Joiner) performJoinRoomByID(
 		}
 	}
 
+	// If a guest is trying to join a room, check that the room has a m.room.guest_access event
+	if req.IsGuest {
+		var guestAccessEvent *gomatrixserverlib.HeaderedEvent
+		guestAccess := "forbidden"
+		guestAccessEvent, err = r.DB.GetStateEvent(ctx, req.RoomIDOrAlias, gomatrixserverlib.MRoomGuestAccess, "")
+		if (err != nil && !errors.Is(err, sql.ErrNoRows)) || guestAccessEvent == nil {
+			logrus.WithError(err).Warn("unable to get m.room.guest_access event, defaulting to 'forbidden'")
+		}
+		if guestAccessEvent != nil {
+			guestAccess = gjson.GetBytes(guestAccessEvent.Content(), "guest_access").String()
+		}
+
+		// Servers MUST only allow guest users to join rooms if the m.room.guest_access state event
+		// is present on the room and has the guest_access value can_join.
+		if guestAccess != "can_join" {
+			return "", "", &rsAPI.PerformError{
+				Code: rsAPI.PerformErrorNotAllowed,
+				Msg:  "Guest access is forbidden",
+			}
+		}
+	}
+
 	// If we should do a forced federated join then do that.
 	var joinedVia gomatrixserverlib.ServerName
 	if forceFederatedJoin {
diff --git a/roomserver/roomserver_test.go b/roomserver/roomserver_test.go
index 518bb372..595ceb52 100644
--- a/roomserver/roomserver_test.go
+++ b/roomserver/roomserver_test.go
@@ -3,18 +3,23 @@ package roomserver_test
 import (
 	"context"
 	"net/http"
+	"reflect"
 	"testing"
 	"time"
 
 	"github.com/gorilla/mux"
+	"github.com/matrix-org/dendrite/internal/httputil"
+	"github.com/matrix-org/dendrite/setup/base"
+	"github.com/matrix-org/dendrite/userapi"
+
+	userAPI "github.com/matrix-org/dendrite/userapi/api"
+
 	"github.com/matrix-org/gomatrixserverlib"
 
-	"github.com/matrix-org/dendrite/internal/httputil"
 	"github.com/matrix-org/dendrite/roomserver"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/inthttp"
 	"github.com/matrix-org/dendrite/roomserver/storage"
-	"github.com/matrix-org/dendrite/setup/base"
 	"github.com/matrix-org/dendrite/test"
 	"github.com/matrix-org/dendrite/test/testrig"
 )
@@ -29,7 +34,28 @@ func mustCreateDatabase(t *testing.T, dbType test.DBType) (*base.BaseDendrite, s
 	return base, db, close
 }
 
-func Test_SharedUsers(t *testing.T) {
+func TestUsers(t *testing.T) {
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+		base, close := testrig.CreateBaseDendrite(t, dbType)
+		defer close()
+		rsAPI := roomserver.NewInternalAPI(base)
+		// SetFederationAPI starts the room event input consumer
+		rsAPI.SetFederationAPI(nil, nil)
+
+		t.Run("shared users", func(t *testing.T) {
+			testSharedUsers(t, rsAPI)
+		})
+
+		t.Run("kick users", func(t *testing.T) {
+			usrAPI := userapi.NewInternalAPI(base, &base.Cfg.UserAPI, nil, nil, rsAPI, nil)
+			rsAPI.SetUserAPI(usrAPI)
+			testKickUsers(t, rsAPI, usrAPI)
+		})
+	})
+
+}
+
+func testSharedUsers(t *testing.T, rsAPI api.RoomserverInternalAPI) {
 	alice := test.NewUser(t)
 	bob := test.NewUser(t)
 	room := test.NewRoom(t, alice, test.RoomPreset(test.PresetTrustedPrivateChat))
@@ -43,36 +69,93 @@ func Test_SharedUsers(t *testing.T) {
 	}, test.WithStateKey(bob.ID))
 
 	ctx := context.Background()
-	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
-		base, _, close := mustCreateDatabase(t, dbType)
-		defer close()
 
-		rsAPI := roomserver.NewInternalAPI(base)
-		// SetFederationAPI starts the room event input consumer
-		rsAPI.SetFederationAPI(nil, nil)
-		// Create the room
-		if err := api.SendEvents(ctx, rsAPI, api.KindNew, room.Events(), "test", "test", "test", nil, false); err != nil {
-			t.Fatalf("failed to send events: %v", err)
-		}
+	// Create the room
+	if err := api.SendEvents(ctx, rsAPI, api.KindNew, room.Events(), "test", "test", "test", nil, false); err != nil {
+		t.Errorf("failed to send events: %v", err)
+	}
 
-		// Query the shared users for Alice, there should only be Bob.
-		// This is used by the SyncAPI keychange consumer.
-		res := &api.QuerySharedUsersResponse{}
-		if err := rsAPI.QuerySharedUsers(ctx, &api.QuerySharedUsersRequest{UserID: alice.ID}, res); err != nil {
-			t.Fatalf("unable to query known users: %v", err)
-		}
-		if _, ok := res.UserIDsToCount[bob.ID]; !ok {
-			t.Fatalf("expected to find %s in shared users, but didn't: %+v", bob.ID, res.UserIDsToCount)
+	// Query the shared users for Alice, there should only be Bob.
+	// This is used by the SyncAPI keychange consumer.
+	res := &api.QuerySharedUsersResponse{}
+	if err := rsAPI.QuerySharedUsers(ctx, &api.QuerySharedUsersRequest{UserID: alice.ID}, res); err != nil {
+		t.Errorf("unable to query known users: %v", err)
+	}
+	if _, ok := res.UserIDsToCount[bob.ID]; !ok {
+		t.Errorf("expected to find %s in shared users, but didn't: %+v", bob.ID, res.UserIDsToCount)
+	}
+	// Also verify that we get the expected result when specifying OtherUserIDs.
+	// This is used by the SyncAPI when getting device list changes.
+	if err := rsAPI.QuerySharedUsers(ctx, &api.QuerySharedUsersRequest{UserID: alice.ID, OtherUserIDs: []string{bob.ID}}, res); err != nil {
+		t.Errorf("unable to query known users: %v", err)
+	}
+	if _, ok := res.UserIDsToCount[bob.ID]; !ok {
+		t.Errorf("expected to find %s in shared users, but didn't: %+v", bob.ID, res.UserIDsToCount)
+	}
+}
+
+func testKickUsers(t *testing.T, rsAPI api.RoomserverInternalAPI, usrAPI userAPI.UserInternalAPI) {
+	// Create users and room; Bob is going to be the guest and kicked on revocation of guest access
+	alice := test.NewUser(t, test.WithAccountType(userAPI.AccountTypeUser))
+	bob := test.NewUser(t, test.WithAccountType(userAPI.AccountTypeGuest))
+
+	room := test.NewRoom(t, alice, test.RoomPreset(test.PresetPublicChat), test.GuestsCanJoin(true))
+
+	// Join with the guest user
+	room.CreateAndInsert(t, bob, gomatrixserverlib.MRoomMember, map[string]interface{}{
+		"membership": "join",
+	}, test.WithStateKey(bob.ID))
+
+	ctx := context.Background()
+
+	// Create the users in the userapi, so the RSAPI can query the account type later
+	for _, u := range []*test.User{alice, bob} {
+		localpart, serverName, _ := gomatrixserverlib.SplitID('@', u.ID)
+		userRes := &userAPI.PerformAccountCreationResponse{}
+		if err := usrAPI.PerformAccountCreation(ctx, &userAPI.PerformAccountCreationRequest{
+			AccountType: u.AccountType,
+			Localpart:   localpart,
+			ServerName:  serverName,
+			Password:    "someRandomPassword",
+		}, userRes); err != nil {
+			t.Errorf("failed to create account: %s", err)
 		}
-		// Also verify that we get the expected result when specifying OtherUserIDs.
-		// This is used by the SyncAPI when getting device list changes.
-		if err := rsAPI.QuerySharedUsers(ctx, &api.QuerySharedUsersRequest{UserID: alice.ID, OtherUserIDs: []string{bob.ID}}, res); err != nil {
-			t.Fatalf("unable to query known users: %v", err)
+	}
+
+	// Create the room in the database
+	if err := api.SendEvents(ctx, rsAPI, api.KindNew, room.Events(), "test", "test", "test", nil, false); err != nil {
+		t.Errorf("failed to send events: %v", err)
+	}
+
+	// Get the membership events BEFORE revoking guest access
+	membershipRes := &api.QueryMembershipsForRoomResponse{}
+	if err := rsAPI.QueryMembershipsForRoom(ctx, &api.QueryMembershipsForRoomRequest{LocalOnly: true, JoinedOnly: true, RoomID: room.ID}, membershipRes); err != nil {
+		t.Errorf("failed to query membership for room: %s", err)
+	}
+
+	// revoke guest access
+	revokeEvent := room.CreateAndInsert(t, alice, gomatrixserverlib.MRoomGuestAccess, map[string]string{"guest_access": "forbidden"}, test.WithStateKey(""))
+	if err := api.SendEvents(ctx, rsAPI, api.KindNew, []*gomatrixserverlib.HeaderedEvent{revokeEvent}, "test", "test", "test", nil, false); err != nil {
+		t.Errorf("failed to send events: %v", err)
+	}
+
+	// TODO: Even though we are sending the events sync, the "kickUsers" function is sending the events async, so we need
+	//		 to loop and wait for the events to be processed by the roomserver.
+	for i := 0; i <= 20; i++ {
+		// Get the membership events AFTER revoking guest access
+		membershipRes2 := &api.QueryMembershipsForRoomResponse{}
+		if err := rsAPI.QueryMembershipsForRoom(ctx, &api.QueryMembershipsForRoomRequest{LocalOnly: true, JoinedOnly: true, RoomID: room.ID}, membershipRes2); err != nil {
+			t.Errorf("failed to query membership for room: %s", err)
 		}
-		if _, ok := res.UserIDsToCount[bob.ID]; !ok {
-			t.Fatalf("expected to find %s in shared users, but didn't: %+v", bob.ID, res.UserIDsToCount)
+
+		// The membership events should NOT match, as Bob (guest user) should now be kicked from the room
+		if !reflect.DeepEqual(membershipRes, membershipRes2) {
+			return
 		}
-	})
+		time.Sleep(time.Millisecond * 10)
+	}
+
+	t.Errorf("memberships didn't change in time")
 }
 
 func Test_QueryLeftUsers(t *testing.T) {