Processing of pending invites on 3PID binding (#218)

* Add missing file headers

* Move the ID server's signatures verification to common

* Allow verification without specifying a server name

* Add third-party structs to membership events content

* Add processing of 3PID onbind requests

* Use reference for third party invite data

* Fix return arguments order

* Revert "Move the ID server's signatures verification to common"

This reverts commit 93442010316ce71a77ac58ffd3613754ce8fe969.

* Revert "Allow verification without specifying a server name"

This reverts commit fd27afbf82eac50fe9f7b83b26cfce3c66d530d2.

* Remove checks that are already occurring in gomatrixserverlib

* Change return type of createInviteFrom3PIDInvite

* Add doc, add checks in fillDisplayName

* Use MakeFedAPI

* Invert condition

* Use AuthEvents to retrieve the 3PID invite

* Update comment

* Remove unused parameter

* gb vendor update github.com/matrix-org/gomatrixserverlib

src/github.com/matrix-org/dendrite/common/eventcontent.go

@@ -22,11 +22,24 @@ type CreateContent struct {
 
 // MemberContent is the event content for http://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-member
 type MemberContent struct {
-	Membership  string `json:"membership"`
+	Membership       string    `json:"membership"`
-	DisplayName string `json:"displayname,omitempty"`
+	DisplayName      string    `json:"displayname,omitempty"`
-	AvatarURL   string `json:"avatar_url,omitempty"`
+	AvatarURL        string    `json:"avatar_url,omitempty"`
-	Reason      string `json:"reason,omitempty"`
+	Reason           string    `json:"reason,omitempty"`
-	// TODO: ThirdPartyInvite string `json:"third_party_invite,omitempty"`
+	ThirdPartyInvite *TPInvite `json:"third_party_invite,omitempty"`
+}
+
+// TPInvite is the "Invite" structure defined at http://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-member
+type TPInvite struct {
+	DisplayName string         `json:"display_name"`
+	Signed      TPInviteSigned `json:"signed"`
+}
+
+// TPInviteSigned is the "signed" structure defined at http://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-member
+type TPInviteSigned struct {
+	MXID       string                       `json:"mxid"`
+	Signatures map[string]map[string]string `json:"signatures"`
+	Token      string                       `json:"token"`
 }
 
 // ThirdPartyInviteContent is the content event for https://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-third-party-invite

src/github.com/matrix-org/dendrite/federationapi/routing/routing.go

@@ -79,6 +79,13 @@ func Setup(
 		},
 	))
 
+	v1fedmux.Handle("/3pid/onbind", common.MakeFedAPI(
+		"3pid_onbind", cfg.Matrix.ServerName, keys,
+		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
+			return writers.CreateInvitesFrom3PIDInvites(httpReq, query, cfg, producer)
+		},
+	))
+
 	v1fedmux.Handle("/event/{eventID}", common.MakeFedAPI(
 		"federation_get_event", cfg.Matrix.ServerName, keys,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {

src/github.com/matrix-org/dendrite/federationapi/writers/invite.go

@@ -1,3 +1,17 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package writers
 
 import (

src/github.com/matrix-org/dendrite/federationapi/writers/send.go

@@ -1,3 +1,17 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package writers
 
 import (

src/github.com/matrix-org/dendrite/federationapi/writers/threepid.go

@@ -0,0 +1,192 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package writers
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/matrix-org/dendrite/clientapi/httputil"
+	"github.com/matrix-org/dendrite/clientapi/producers"
+	"github.com/matrix-org/dendrite/common"
+	"github.com/matrix-org/dendrite/common/config"
+	"github.com/matrix-org/dendrite/roomserver/api"
+
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+type invite struct {
+	MXID   string                `json:"mxid"`
+	RoomID string                `json:"room_id"`
+	Sender string                `json:"sender"`
+	Token  string                `json:"token"`
+	Signed common.TPInviteSigned `json:"signed"`
+}
+
+type invites struct {
+	Medium  string   `json:"medium"`
+	Address string   `json:"address"`
+	MXID    string   `json:"mxid"`
+	Invites []invite `json:"invites"`
+}
+
+// CreateInvitesFrom3PIDInvites implements POST /_matrix/federation/v1/3pid/onbind
+func CreateInvitesFrom3PIDInvites(
+	req *http.Request, queryAPI api.RoomserverQueryAPI, cfg config.Dendrite,
+	producer *producers.RoomserverProducer,
+) util.JSONResponse {
+	var body invites
+	if reqErr := httputil.UnmarshalJSONRequest(req, &body); reqErr != nil {
+		return *reqErr
+	}
+
+	evs := []gomatrixserverlib.Event{}
+	for _, inv := range body.Invites {
+		event, err := createInviteFrom3PIDInvite(queryAPI, cfg, inv)
+		if err != nil {
+			return httputil.LogThenError(req, err)
+		}
+		if event != nil {
+			evs = append(evs, *event)
+		}
+	}
+
+	// Send all the events
+	if err := producer.SendEvents(evs, cfg.Matrix.ServerName); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: struct{}{},
+	}
+}
+
+// createInviteFrom3PIDInvite processes an invite provided by the identity server
+// and creates a m.room.member event (with "invite" membership) from it.
+// Returns an error if there was a problem building the event or fetching the
+// necessary data to do so.
+func createInviteFrom3PIDInvite(
+	queryAPI api.RoomserverQueryAPI, cfg config.Dendrite, inv invite,
+) (*gomatrixserverlib.Event, error) {
+	// Build the event
+	builder := &gomatrixserverlib.EventBuilder{
+		Type:     "m.room.member",
+		Sender:   inv.Sender,
+		RoomID:   inv.RoomID,
+		StateKey: &inv.MXID,
+	}
+
+	content := common.MemberContent{
+		// TODO: Load the profile
+		Membership: "invite",
+		ThirdPartyInvite: &common.TPInvite{
+			Signed: inv.Signed,
+		},
+	}
+
+	if err := builder.SetContent(content); err != nil {
+		return nil, err
+	}
+
+	eventsNeeded, err := gomatrixserverlib.StateNeededForEventBuilder(builder)
+	if err != nil {
+		return nil, err
+	}
+
+	// Ask the roomserver for information about this room
+	queryReq := api.QueryLatestEventsAndStateRequest{
+		RoomID:       builder.RoomID,
+		StateToFetch: eventsNeeded.Tuples(),
+	}
+	var queryRes api.QueryLatestEventsAndStateResponse
+	if err = queryAPI.QueryLatestEventsAndState(&queryReq, &queryRes); err != nil {
+		return nil, err
+	}
+
+	if !queryRes.RoomExists {
+		// TODO: Use federation to auth the event
+		return nil, nil
+	}
+
+	// Finish building the event
+	builder.Depth = queryRes.Depth
+	builder.PrevEvents = queryRes.LatestEvents
+
+	authEvents := gomatrixserverlib.NewAuthEvents(nil)
+
+	for i := range queryRes.StateEvents {
+		authEvents.AddEvent(&queryRes.StateEvents[i])
+	}
+
+	if err = fillDisplayName(builder, content, authEvents); err != nil {
+		return nil, err
+	}
+
+	refs, err := eventsNeeded.AuthEventReferences(&authEvents)
+	if err != nil {
+		return nil, err
+	}
+	builder.AuthEvents = refs
+
+	eventID := fmt.Sprintf("$%s:%s", util.RandomString(16), cfg.Matrix.ServerName)
+	now := time.Now()
+	event, err := builder.Build(eventID, now, cfg.Matrix.ServerName, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return &event, nil
+}
+
+// fillDisplayName looks in a list of auth events for a m.room.third_party_invite
+// event with the state key matching a given m.room.member event's content's token.
+// If such an event is found, fills the "display_name" attribute of the
+// "third_party_invite" structure in the m.room.member event with the display_name
+// from the m.room.third_party_invite event.
+// Returns an error if there was a problem parsing the m.room.third_party_invite
+// event's content or updating the m.room.member event's content.
+// Returns nil if no m.room.third_party_invite with a matching token could be
+// found. Returning an error isn't necessary in this case as the event will be
+// rejected by gomatrixserverlib.
+func fillDisplayName(
+	builder *gomatrixserverlib.EventBuilder, content common.MemberContent,
+	authEvents gomatrixserverlib.AuthEvents,
+) error {
+	// Look for the m.room.third_party_invite event
+	thirdPartyInviteEvent, _ := authEvents.ThirdPartyInvite(content.ThirdPartyInvite.Signed.Token)
+
+	if thirdPartyInviteEvent == nil {
+		// If the third party invite event doesn't exist then we can't use it to set the display name.
+		return nil
+	}
+
+	var thirdPartyInviteContent common.ThirdPartyInviteContent
+	if err := json.Unmarshal(thirdPartyInviteEvent.Content(), &thirdPartyInviteContent); err != nil {
+		return err
+	}
+
+	// Use the m.room.third_party_invite event to fill the "displayname" and
+	// update the m.room.member event's content with it
+	content.ThirdPartyInvite.DisplayName = thirdPartyInviteContent.DisplayName
+	if err := builder.SetContent(content); err != nil {
+		return err
+	}
+
+	return nil
+}

vendor/manifest

@@ -116,7 +116,7 @@
 		{
 			"importpath": "github.com/matrix-org/gomatrixserverlib",
 			"repository": "https://github.com/matrix-org/gomatrixserverlib",
-			"revision": "768a8767051a4aca7f5e41f912954ae04d5f1efb",
+			"revision": "2e9caead882bcdeb999cf4677cfff47e39d3271e",
 			"branch": "master"
 		},
 		{

vendor/src/github.com/matrix-org/gomatrixserverlib/base64.go

@@ -18,6 +18,7 @@ package gomatrixserverlib
 import (
 	"encoding/base64"
 	"encoding/json"
+	"strings"
 )
 
 // A Base64String is a string of bytes that are base64 encoded when used in JSON.
@@ -43,6 +44,12 @@ func (b64 *Base64String) UnmarshalJSON(raw []byte) (err error) {
 	if err = json.Unmarshal(raw, &str); err != nil {
 		return
 	}
-	*b64, err = base64.RawStdEncoding.DecodeString(str)
+	// We must check whether the string was encoded in a URL-safe way in order
+	// to use the appropriate encoding.
+	if strings.ContainsAny(str, "-_") {
+		*b64, err = base64.RawURLEncoding.DecodeString(str)
+	} else {
+		*b64, err = base64.RawStdEncoding.DecodeString(str)
+	}
 	return
 }

vendor/src/github.com/matrix-org/gomatrixserverlib/base64_test.go

@@ -45,6 +45,19 @@ func TestUnmarshalBase64(t *testing.T) {
 	}
 }
 
+func TestUnmarshalUrlSafeBase64(t *testing.T) {
+	input := []byte(`"dGhpc_9pc_9h_3Rlc3Q"`)
+	want := "this\xffis\xffa\xfftest"
+	var got Base64String
+	err := json.Unmarshal(input, &got)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != want {
+		t.Fatalf("json.Unmarshal(%q): wanted %q got %q", string(input), want, string(got))
+	}
+}
+
 func TestMarshalBase64Struct(t *testing.T) {
 	input := struct{ Value Base64String }{Base64String("this\xffis\xffa\xfftest")}
 	want := `{"Value":"dGhpc/9pc/9h/3Rlc3Q"}`

vendor/src/github.com/matrix-org/gomatrixserverlib/event.go

@@ -422,7 +422,7 @@ func (e Event) CheckFields() error {
 		if e.fields.Type != MRoomMember {
 			return fmt.Errorf(
 				"gomatrixserverlib: sender domain doesn't match origin: %q != %q",
-				eventDomain, e.fields.Origin,
+				senderDomain, e.fields.Origin,
 			)
 		}
 		c, err := newMemberContentFromEvent(e)
@@ -432,7 +432,7 @@ func (e Event) CheckFields() error {
 		if c.Membership != invite || c.ThirdPartyInvite == nil {
 			return fmt.Errorf(
 				"gomatrixserverlib: sender domain doesn't match origin: %q != %q",
-				eventDomain, e.fields.Origin,
+				senderDomain, e.fields.Origin,
 			)
 		}
 	}

vendor/src/github.com/matrix-org/gomatrixserverlib/event_examples_test.go

@@ -0,0 +1,27 @@
+/* Copyright 2016-2017 Vector Creations Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package gomatrixserverlib
+
+import "fmt"
+
+func ExampleSplitID() {
+	localpart, domain, err := SplitID('@', "@alice:localhost:8080")
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(localpart, domain)
+	// Output: alice localhost:8080
+}

vendor/src/github.com/matrix-org/gomatrixserverlib/eventauth.go

@@ -18,6 +18,9 @@ package gomatrixserverlib
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/ed25519"
 
 	"github.com/matrix-org/util"
 )
@@ -224,15 +227,7 @@ func accumulateStateNeeded(result *StateNeeded, eventType, sender string, stateK
 }
 
 // thirdPartyInviteToken extracts the token from the third_party_invite.
-func thirdPartyInviteToken(thirdPartyInviteData rawJSON) (string, error) {
+func thirdPartyInviteToken(thirdPartyInvite *memberThirdPartyInvite) (string, error) {
-	var thirdPartyInvite struct {
-		Signed struct {
-			Token string `json:"token"`
-		} `json:"signed"`
-	}
-	if err := json.Unmarshal(thirdPartyInviteData, &thirdPartyInvite); err != nil {
-		return "", err
-	}
 	if thirdPartyInvite.Signed.Token == "" {
 		return "", fmt.Errorf("missing 'third_party_invite.signed.token' JSON key")
 	}
@@ -774,6 +769,8 @@ type membershipAllower struct {
 	powerLevels powerLevelContent
 	// The m.room.join_rules content for the room.
 	joinRule joinRuleContent
+	// The m.room.third_party_invite content referenced by this event.
+	thirdPartyInvite thirdPartyInviteContent
 }
 
 // newMembershipAllower loads the information needed to authenticate the m.room.member event
@@ -808,6 +805,13 @@ func newMembershipAllower(authEvents AuthEventProvider, event Event) (m membersh
 			return
 		}
 	}
+	// If this event comes from a third_party_invite, we need to check it against the original event.
+	if m.newMember.ThirdPartyInvite != nil {
+		token := m.newMember.ThirdPartyInvite.Signed.Token
+		if m.thirdPartyInvite, err = newThirdPartyInviteContentFromAuthEvents(authEvents, token); err != nil {
+			return
+		}
+	}
 	return
 }
 
@@ -840,10 +844,10 @@ func (m *membershipAllower) membershipAllowed(event Event) error {
 		// Otherwise fall back to the normal checks.
 	}
 
-	if m.newMember.Membership == invite && len(m.newMember.ThirdPartyInvite) != 0 {
+	if m.newMember.Membership == invite && m.newMember.ThirdPartyInvite != nil {
 		// Special case third party invites
 		// https://github.com/matrix-org/synapse/blob/v0.18.5/synapse/api/auth.py#L393
-		panic(fmt.Errorf("ThirdPartyInvite not implemented"))
+		return m.membershipAllowedFromThirdPartyInvite()
 	}
 
 	if m.targetID == m.senderID {
@@ -855,6 +859,42 @@ func (m *membershipAllower) membershipAllowed(event Event) error {
 	return m.membershipAllowedOther()
 }
 
+// membershipAllowedFronThirdPartyInvite determines if the member events is following
+// up the third_party_invite event it claims.
+func (m *membershipAllower) membershipAllowedFromThirdPartyInvite() error {
+	// Check if the event's target matches with the Matrix ID provided by the
+	// identity server.
+	if m.targetID != m.newMember.ThirdPartyInvite.Signed.MXID {
+		return errorf(
+			"The invite target %s doesn't match with the Matrix ID provided by the identity server %s",
+			m.targetID, m.newMember.ThirdPartyInvite.Signed.MXID,
+		)
+	}
+	// Marshal the "signed" so it can be verified by VerifyJSON.
+	marshalledSigned, err := json.Marshal(m.newMember.ThirdPartyInvite.Signed)
+	if err != nil {
+		return err
+	}
+	// Check each signature with each public key. If one signature could be
+	// verified with one public key, accept the event.
+	for _, publicKey := range m.thirdPartyInvite.PublicKeys {
+		for domain, signatures := range m.newMember.ThirdPartyInvite.Signed.Signatures {
+			for keyID := range signatures {
+				if strings.HasPrefix(keyID, "ed25519") {
+					if err = VerifyJSON(
+						domain, KeyID(keyID),
+						ed25519.PublicKey(publicKey.PublicKey),
+						marshalledSigned,
+					); err == nil {
+						return nil
+					}
+				}
+			}
+		}
+	}
+	return errorf("Couldn't verify signature on third-party invite for %s", m.targetID)
+}
+
 // membershipAllowedSelf determines if the change made by the user to their own membership is allowed.
 func (m *membershipAllower) membershipAllowedSelf() error {
 	if m.newMember.Membership == join {

vendor/src/github.com/matrix-org/gomatrixserverlib/eventauth_test.go

@@ -169,7 +169,12 @@ func TestStateNeededForInvite3PID(t *testing.T) {
 		StateKey: &skey,
 		Sender:   "@u1:a",
 	}
-	b.SetContent(memberContent{"invite", rawJSON(`{"signed":{"token":"my_token"}}`)})
+
+	b.SetContent(memberContent{"invite", &memberThirdPartyInvite{
+		Signed: memberThirdPartyInviteSigned{
+			Token: "my_token",
+		},
+	}})
 	testStateNeededForAuth(t, `[{
 		"type": "m.room.member",
 		"state_key": "@u2:b",
@@ -280,7 +285,7 @@ func testEventAllowed(t *testing.T, testCaseJSON string) {
 			panic(err)
 		}
 		if err := Allowed(event, &tc.AuthEvents); err == nil {
-			t.Fatalf("Expected %q to not be allowed but it was: %q", string(data), err)
+			t.Fatalf("Expected %q to not be allowed but it was", string(data))
 		}
 	}
 }
@@ -532,6 +537,146 @@ func TestAllowedWithNoPowerLevels(t *testing.T) {
 	}`)
 }
 
+func TestAllowedInviteFrom3PID(t *testing.T) {
+	testEventAllowed(t, `{
+		"auth_events": {
+			"create": {
+				"type": "m.room.create",
+				"state_key": "",
+				"sender": "@u1:a",
+				"room_id": "!r1:a",
+				"event_id": "$e1:a",
+				"content": {"creator": "@u1:a"}
+			},
+			"member": {
+				"@u1:a": {
+					"type": "m.room.member",
+					"sender": "@u1:a",
+					"room_id": "!r1:a",
+					"state_key": "@u1:a",
+					"event_id": "$e2:a",
+					"content": {"membership": "join"}
+				}
+			},
+			"third_party_invite": {
+				"my_token": {
+					"type": "m.room.third_party_invite",
+					"sender": "@u1:a",
+					"room_id": "!r1:a",
+					"state_key": "my_token",
+					"event_id": "$e3:a",
+					"content": {
+						"display_name": "foo...@bar...",
+						"public_key": "pubkey",
+						"key_validity_url": "https://example.tld/isvalid",
+						"public_keys": [
+							{
+								"public_key": "mrV51jApZKahGjfMhlevp+QtSSTDKCLaLVCzYc4HELY",
+								"key_validity_url": "https://example.tld/isvalid"
+							}
+						]
+					}
+				}
+			}
+		},
+		"allowed": [{
+			"type": "m.room.member",
+			"sender": "@u1:a",
+			"room_id": "!r1:a",
+			"state_key": "@u2:a",
+			"event_id": "$e4:a",
+			"content": {
+				"membership": "invite",
+				"third_party_invite": {
+					"display_name": "foo...@bar...",
+					"signed": {
+						"token": "my_token",
+						"mxid": "@u2:a",
+						"signatures": {
+							"example.tld": {
+								"ed25519:0": "CibGFS0vX93quJFppsQbYQKJFIwxiYEK87lNmekS/fdetUMXPdR2wwNDd09J1jJ28GCH3GogUTuFDB1ScPFxBg"
+							}
+						}
+					}
+				}
+			}
+		}],
+		"not_allowed": [{
+			"type": "m.room.member",
+			"sender": "@u1:a",
+			"room_id": "!r1:a",
+			"state_key": "@u2:a",
+			"event_id": "$e4:a",
+			"content": {
+				"membership": "invite",
+				"third_party_invite": {
+					"display_name": "foo...@bar...",
+					"signed": {
+						"token": "my_token",
+						"mxid": "@u2:a",
+						"signatures": {
+							"example.tld": {
+								"ed25519:0": "some_signature"
+							}
+						}
+					}
+				}
+			},
+			"unsigned": {
+				"not_allowed": "Bad signature"
+			}
+		}, {
+			"type": "m.room.member",
+			"sender": "@u1:a",
+			"room_id": "!r1:a",
+			"state_key": "@u2:a",
+			"event_id": "$e5:a",
+			"content": {
+				"membership": "invite",
+				"third_party_invite": {
+					"display_name": "foo...@bar...",
+					"signed": {
+						"token": "my_token",
+						"mxid": "@u3:a",
+						"signatures": {
+							"example.tld": {
+								"ed25519:0": "CibGFS0vX93quJFppsQbYQKJFIwxiYEK87lNmekS/fdetUMXPdR2wwNDd09J1jJ28GCH3GogUTuFDB1ScPFxBg"
+							}
+						}
+					}
+				}
+			},
+			"unsigned": {
+				"not_allowed": "MXID doesn't match state key"
+			}
+		}, {
+			"type": "m.room.member",
+			"sender": "@u1:a",
+			"room_id": "!r1:a",
+			"state_key": "@u2:a",
+			"event_id": "$e6:a",
+			"content": {
+				"membership": "invite",
+				"third_party_invite": {
+					"display_name": "foo...@bar...",
+					"signed": {
+						"token": "my_other_token",
+						"mxid": "@u2:a",
+						"signatures": {
+							"example.tld": {
+								"ed25519:0": "CibGFS0vX93quJFppsQbYQKJFIwxiYEK87lNmekS/fdetUMXPdR2wwNDd09J1jJ28GCH3GogUTuFDB1ScPFxBg"
+							}
+						}
+					}
+				}
+			},
+			"unsigned": {
+				"not_allowed": "Token doesn't refer to a known third-party invite"
+			}
+		}]
+	}`)
+}
+
 func TestAllowedNoFederation(t *testing.T) {
 	testEventAllowed(t, `{
 		"auth_events": {

vendor/src/github.com/matrix-org/gomatrixserverlib/eventcontent.go

@@ -108,7 +108,18 @@ type memberContent struct {
 	// We use the membership key in order to check if the user is in the room.
 	Membership string `json:"membership"`
 	// We use the third_party_invite key to special case thirdparty invites.
-	ThirdPartyInvite rawJSON `json:"third_party_invite,omitempty"`
+	ThirdPartyInvite *memberThirdPartyInvite `json:"third_party_invite,omitempty"`
+}
+
+type memberThirdPartyInvite struct {
+	DisplayName string                       `json:"display_name"`
+	Signed      memberThirdPartyInviteSigned `json:"signed"`
+}
+
+type memberThirdPartyInviteSigned struct {
+	MXID       string                       `json:"mxid"`
+	Signatures map[string]map[string]string `json:"signatures"`
+	Token      string                       `json:"token"`
 }
 
 // newMemberContentFromAuthEvents loads the member content from the member event for the user ID in the auth events.
@@ -137,6 +148,32 @@ func newMemberContentFromEvent(event Event) (c memberContent, err error) {
 	return
 }
 
+// thirdPartyInviteContent is the JSON content of a m.room.third_party_invite event needed for auth checks.
+// See https://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-third-party-invite for descriptions of the fields.
+type thirdPartyInviteContent struct {
+	// Public keys are used to verify the signature of a m.room.member event that
+	// came from a m.room.third_party_invite event
+	PublicKeys []struct {
+		PublicKey Base64String `json:"public_key"`
+	} `json:"public_keys"`
+}
+
+func newThirdPartyInviteContentFromAuthEvents(authEvents AuthEventProvider, token string) (t thirdPartyInviteContent, err error) {
+	var thirdPartyInviteEvent *Event
+	if thirdPartyInviteEvent, err = authEvents.ThirdPartyInvite(token); err != nil {
+		return
+	}
+	if thirdPartyInviteEvent == nil {
+		// If there isn't a third_party_invite event, then we return with an error
+		err = errorf("Couldn't find third party invite event")
+		return
+	}
+	if err = json.Unmarshal(thirdPartyInviteEvent.Content(), &t); err != nil {
+		err = errorf("unparsable third party invite event content: %s", err.Error())
+	}
+	return
+}
+
 // joinRuleContent is the JSON content of a m.room.join_rules event needed for auth checks.
 // See  https://matrix.org/docs/spec/client_server/r0.2.0.html#m-room-join-rules for descriptions of the fields.
 type joinRuleContent struct {