Add config and checks for trusted ID servers (#206)

* Add config for trusted ID servers

* Add new error

* Implement check for trusted ID server

* Complete unfinished comment

* Make comment more explicit in the config file

* Use go standard errors in membership.go

* Use standard errors instead of JSON responses in threepid

* Doc errors

* Remove unused parameter

8 files changed, 175 insertions, 80 deletions

diff --git a/dendrite-config.yaml b/dendrite-config.yaml
index a91429c2..c9cab73e 100644
--- a/dendrite-config.yaml
+++ b/dendrite-config.yaml
@@ -12,6 +12,12 @@ matrix:
     private_key: "/etc/dendrite/matrix_key.pem"
     # The x509 certificates used by the federation listeners for this server
     federation_certificates: ["/etc/dendrite/server.pem"]
+    # The list of identity servers trusted to verify third party identifiers by this server.
+    # Defaults to no trusted servers.
+    trusted_third_party_id_servers:
+      - vector.im
+      - matrix.org
+      - riot.im
 
 # The media repository config
 media:
diff --git a/src/github.com/matrix-org/dendrite/clientapi/jsonerror/jsonerror.go b/src/github.com/matrix-org/dendrite/clientapi/jsonerror/jsonerror.go
index 3a424dde..d267355e 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/jsonerror/jsonerror.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/jsonerror/jsonerror.go
@@ -104,3 +104,12 @@ func LimitExceeded(msg string, retryAfterMS int64) *LimitExceededError {
 		RetryAfterMS: retryAfterMS,
 	}
 }
+
+// NotTrusted is an error which is returned when the client asks the server to
+// proxy a request (e.g. 3PID association) to a server that isn't trusted
+func NotTrusted(serverName string) *MatrixError {
+	return &MatrixError{
+		ErrCode: "M_SERVER_NOT_TRUSTED",
+		Err:     fmt.Sprintf("Untrusted server '%s'", serverName),
+	}
+}
diff --git a/src/github.com/matrix-org/dendrite/clientapi/readers/threepid.go b/src/github.com/matrix-org/dendrite/clientapi/readers/threepid.go
index 4b86108e..b0d79287 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/readers/threepid.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/readers/threepid.go
@@ -22,6 +22,7 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/clientapi/threepid"
+	"github.com/matrix-org/dendrite/common/config"
 
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
@@ -38,7 +39,7 @@ type threePIDsResponse struct {
 // RequestEmailToken implements:
 //     POST /account/3pid/email/requestToken
 //     POST /register/email/requestToken
-func RequestEmailToken(req *http.Request, accountDB *accounts.Database) util.JSONResponse {
+func RequestEmailToken(req *http.Request, accountDB *accounts.Database, cfg config.Dendrite) util.JSONResponse {
 	var body threepid.EmailAssociationRequest
 	if reqErr := httputil.UnmarshalJSONRequest(req, &body); reqErr != nil {
 		return *reqErr
@@ -63,8 +64,13 @@ func RequestEmailToken(req *http.Request, accountDB *accounts.Database) util.JSO
 		}
 	}
 
-	resp.SID, err = threepid.CreateSession(body)
-	if err != nil {
+	resp.SID, err = threepid.CreateSession(body, cfg)
+	if err == threepid.ErrNotTrusted {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.NotTrusted(body.IDServer),
+		}
+	} else if err != nil {
 		return httputil.LogThenError(req, err)
 	}
 
@@ -77,6 +83,7 @@ func RequestEmailToken(req *http.Request, accountDB *accounts.Database) util.JSO
 // CheckAndSave3PIDAssociation implements POST /account/3pid
 func CheckAndSave3PIDAssociation(
 	req *http.Request, accountDB *accounts.Database, device *authtypes.Device,
+	cfg config.Dendrite,
 ) util.JSONResponse {
 	var body threepid.EmailAssociationCheckRequest
 	if reqErr := httputil.UnmarshalJSONRequest(req, &body); reqErr != nil {
@@ -84,8 +91,13 @@ func CheckAndSave3PIDAssociation(
 	}
 
 	// Check if the association has been validated
-	verified, address, medium, err := threepid.CheckAssociation(body.Creds)
-	if err != nil {
+	verified, address, medium, err := threepid.CheckAssociation(body.Creds, cfg)
+	if err == threepid.ErrNotTrusted {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.NotTrusted(body.Creds.IDServer),
+		}
+	} else if err != nil {
 		return httputil.LogThenError(req, err)
 	}
 
@@ -101,7 +113,13 @@ func CheckAndSave3PIDAssociation(
 
 	if body.Bind {
 		// Publish the association on the identity server if requested
-		if err = threepid.PublishAssociation(body.Creds, device.UserID); err != nil {
+		err = threepid.PublishAssociation(body.Creds, device.UserID, cfg)
+		if err == threepid.ErrNotTrusted {
+			return util.JSONResponse{
+				Code: 400,
+				JSON: jsonerror.NotTrusted(body.Creds.IDServer),
+			}
+		} else if err != nil {
 			return httputil.LogThenError(req, err)
 		}
 	}
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
index 58e852fe..1620d6df 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
@@ -241,7 +241,7 @@ func Setup(
 
 	r0mux.Handle("/account/3pid",
 		common.MakeAuthAPI("account_3pid", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
-			return readers.CheckAndSave3PIDAssociation(req, accountDB, device)
+			return readers.CheckAndSave3PIDAssociation(req, accountDB, device, cfg)
 		}),
 	).Methods("POST", "OPTIONS")
 
@@ -253,7 +253,7 @@ func Setup(
 
 	r0mux.Handle("/{path:(?:account/3pid|register)}/email/requestToken",
 		common.MakeAPI("account_3pid_request_token", func(req *http.Request) util.JSONResponse {
-			return readers.RequestEmailToken(req, accountDB)
+			return readers.RequestEmailToken(req, accountDB, cfg)
 		}),
 	).Methods("POST", "OPTIONS")
 
diff --git a/src/github.com/matrix-org/dendrite/clientapi/threepid/invites.go b/src/github.com/matrix-org/dendrite/clientapi/threepid/invites.go
index 85f0b5dc..27cdf343 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/threepid/invites.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/threepid/invites.go
@@ -26,15 +26,11 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
 	"github.com/matrix-org/dendrite/clientapi/events"
-	"github.com/matrix-org/dendrite/clientapi/httputil"
-	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"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"
 )
 
 // MembershipRequest represents the body of an incoming POST request
@@ -66,6 +62,15 @@ type idServerStoreInviteResponse struct {
 	PublicKeys  []common.PublicKey `json:"public_keys"`
 }
 
+var (
+	// ErrMissingParameter is the error raised if a request for 3PID invite has
+	// an incomplete body
+	ErrMissingParameter = errors.New("'address', 'id_server' and 'medium' must all be supplied")
+	// ErrNotTrusted is the error raised if an identity server isn't in the list
+	// of trusted servers in the configuration file.
+	ErrNotTrusted = errors.New("untrusted server")
+)
+
 // CheckAndProcessInvite analyses the body of an incoming membership request.
 // If the fields relative to a third-party-invite are all supplied, lookups the
 // matching Matrix ID from the given identity server. If no Matrix ID is
@@ -80,27 +85,24 @@ type idServerStoreInviteResponse struct {
 // fills the Matrix ID in the request body so a normal invite membership event
 // can be emitted.
 func CheckAndProcessInvite(
-	req *http.Request, device *authtypes.Device, body *MembershipRequest,
-	cfg config.Dendrite, queryAPI api.RoomserverQueryAPI, db *accounts.Database,
+	device *authtypes.Device, body *MembershipRequest, cfg config.Dendrite,
+	queryAPI api.RoomserverQueryAPI, db *accounts.Database,
 	producer *producers.RoomserverProducer, membership string, roomID string,
-) *util.JSONResponse {
+) (inviteStoredOnIDServer bool, err error) {
 	if membership != "invite" || (body.Address == "" && body.IDServer == "" && body.Medium == "") {
 		// If none of the 3PID-specific fields are supplied, it's a standard invite
 		// so return nil for it to be processed as such
-		return nil
+		return
 	} else if body.Address == "" || body.IDServer == "" || body.Medium == "" {
 		// If at least one of the 3PID-specific fields is supplied but not all
 		// of them, return an error
-		return &util.JSONResponse{
-			Code: 400,
-			JSON: jsonerror.BadJSON("'address', 'id_server' and 'medium' must all be supplied"),
-		}
+		err = ErrMissingParameter
+		return
 	}
 
 	lookupRes, storeInviteRes, err := queryIDServer(db, cfg, device, body, roomID)
 	if err != nil {
-		resErr := httputil.LogThenError(req, err)
-		return &resErr
+		return
 	}
 
 	if lookupRes.MXID == "" {
@@ -108,28 +110,16 @@ func CheckAndProcessInvite(
 		// "m.room.third_party_invite" have to be emitted from the data in
 		// storeInviteRes.
 		err = emit3PIDInviteEvent(body, storeInviteRes, device, roomID, cfg, queryAPI, producer)
-		if err == events.ErrRoomNoExists {
-			return &util.JSONResponse{
-				Code: 404,
-				JSON: jsonerror.NotFound(err.Error()),
-			}
-		} else if err != nil {
-			resErr := httputil.LogThenError(req, err)
-			return &resErr
-		}
+		inviteStoredOnIDServer = err == nil
 
-		// If everything went well, returns with an empty response.
-		return &util.JSONResponse{
-			Code: 200,
-			JSON: struct{}{},
-		}
+		return
 	}
 
 	// A Matrix ID have been found: set it in the body request and let the process
 	// continue to create a "m.room.member" event with an "invite" membership
 	body.UserID = lookupRes.MXID
 
-	return nil
+	return
 }
 
 // queryIDServer handles all the requests to the identity server, starting by
@@ -142,9 +132,13 @@ func CheckAndProcessInvite(
 // Returns a representation of the response for both cases.
 // Returns an error if a check or a request failed.
 func queryIDServer(
-	db *accounts.Database, cfg config.Dendrite,
-	device *authtypes.Device, body *MembershipRequest, roomID string,
+	db *accounts.Database, cfg config.Dendrite, device *authtypes.Device,
+	body *MembershipRequest, roomID string,
 ) (lookupRes *idServerLookupResponse, storeInviteRes *idServerStoreInviteResponse, err error) {
+	if err = isTrusted(body.IDServer, cfg); err != nil {
+		return
+	}
+
 	// Lookup the 3PID
 	lookupRes, err = queryIDServerLookup(body)
 	if err != nil {
@@ -249,7 +243,6 @@ func queryIDServerStoreInvite(
 	}
 
 	if resp.StatusCode != http.StatusOK {
-		// TODO: Log the error supplied with the identity server?
 		errMsg := fmt.Sprintf("Identity server %s responded with a %d error code", body.IDServer, resp.StatusCode)
 		return nil, errors.New(errMsg)
 	}
@@ -275,7 +268,6 @@ func queryIDServerPubKey(idServerName string, keyID string) ([]byte, error) {
 	}
 
 	if resp.StatusCode != http.StatusOK {
-		// TODO: Log the error supplied with the identity server?
 		errMsg := fmt.Sprintf("Couldn't retrieve key %s from server %s", keyID, idServerName)
 		return nil, errors.New(errMsg)
 	}
@@ -297,7 +289,6 @@ func checkIDServerSignatures(body *MembershipRequest, res *idServerLookupRespons
 		return err
 	}
 
-	// TODO: Check if the domain is part of a list of trusted ID servers
 	signatures, ok := res.Signatures[body.IDServer]
 	if !ok {
 		return errors.New("No signature for domain " + body.IDServer)
diff --git a/src/github.com/matrix-org/dendrite/clientapi/threepid/threepid.go b/src/github.com/matrix-org/dendrite/clientapi/threepid/threepid.go
index 2ec4599a..f07a3a14 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/threepid/threepid.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/threepid/threepid.go
@@ -22,6 +22,8 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
+
+	"github.com/matrix-org/dendrite/common/config"
 )
 
 // EmailAssociationRequest represents the request defined at https://matrix.org/docs/spec/client_server/r0.2.0.html#post-matrix-client-r0-register-email-requesttoken
@@ -49,8 +51,10 @@ type Credentials struct {
 // Returns the session's ID.
 // Returns an error if there was a problem sending the request or decoding the
 // response, or if the identity server responded with a non-OK status.
-func CreateSession(req EmailAssociationRequest) (string, error) {
-	// TODO: Check if the ID server is trusted
+func CreateSession(req EmailAssociationRequest, cfg config.Dendrite) (string, error) {
+	if err := isTrusted(req.IDServer, cfg); err != nil {
+		return "", err
+	}
 
 	// Create a session on the ID server
 	postURL := fmt.Sprintf("https://%s/_matrix/identity/api/v1/validate/email/requestToken", req.IDServer)
@@ -93,8 +97,11 @@ func CreateSession(req EmailAssociationRequest) (string, error) {
 // identifier and its medium.
 // Returns an error if there was a problem sending the request or decoding the
 // response, or if the identity server responded with a non-OK status.
-func CheckAssociation(creds Credentials) (bool, string, string, error) {
-	// TODO: Check if the ID server is trusted
+func CheckAssociation(creds Credentials, cfg config.Dendrite) (bool, string, string, error) {
+	if err := isTrusted(creds.IDServer, cfg); err != nil {
+		return false, "", "", err
+	}
+
 	url := fmt.Sprintf("https://%s/_matrix/identity/api/v1/3pid/getValidated3pid?sid=%s&client_secret=%s", creds.IDServer, creds.SID, creds.Secret)
 	resp, err := http.Get(url)
 	if err != nil {
@@ -126,8 +133,11 @@ func CheckAssociation(creds Credentials) (bool, string, string, error) {
 // identifier and a Matrix ID.
 // Returns an error if there was a problem sending the request or decoding the
 // response, or if the identity server responded with a non-OK status.
-func PublishAssociation(creds Credentials, userID string) error {
-	// TODO: Check if the ID server is trusted
+func PublishAssociation(creds Credentials, userID string, cfg config.Dendrite) error {
+	if err := isTrusted(creds.IDServer, cfg); err != nil {
+		return err
+	}
+
 	postURL := fmt.Sprintf("https://%s/_matrix/identity/api/v1/3pid/bind", creds.IDServer)
 
 	data := url.Values{}
@@ -154,3 +164,15 @@ func PublishAssociation(creds Credentials, userID string) error {
 
 	return nil
 }
+
+// isTrusted checks if a given identity server is part of the list of trusted
+// identity servers in the configuration file.
+// Returns an error if the server isn't trusted.
+func isTrusted(idServer string, cfg config.Dendrite) error {
+	for _, server := range cfg.Matrix.TrustedIDServers {
+		if idServer == server {
+			return nil
+		}
+	}
+	return ErrNotTrusted
+}
diff --git a/src/github.com/matrix-org/dendrite/clientapi/writers/membership.go b/src/github.com/matrix-org/dendrite/clientapi/writers/membership.go
index 6dd52a00..4173e51a 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/writers/membership.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/writers/membership.go
@@ -15,6 +15,7 @@
 package writers
 
 import (
+	"errors"
 	"net/http"
 
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
@@ -32,6 +33,8 @@ import (
 	"github.com/matrix-org/util"
 )
 
+var errMissingUserID = errors.New("'user_id' must be supplied")
+
 // SendMembership implements PUT /rooms/{roomID}/(join|kick|ban|unban|leave|invite)
 // by building a m.room.member event then sending it to the room server
 func SendMembership(
@@ -44,20 +47,78 @@ func SendMembership(
 		return *reqErr
 	}
 
-	if res := threepid.CheckAndProcessInvite(
-		req, device, &body, cfg, queryAPI, accountDB, producer, membership, roomID,
-	); res != nil {
-		return *res
+	inviteStored, err := threepid.CheckAndProcessInvite(
+		device, &body, cfg, queryAPI, accountDB, producer, membership, roomID,
+	)
+	if err == threepid.ErrMissingParameter {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.BadJSON(err.Error()),
+		}
+	} else if err == threepid.ErrNotTrusted {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.NotTrusted(body.IDServer),
+		}
+	} else if err == events.ErrRoomNoExists {
+		return util.JSONResponse{
+			Code: 404,
+			JSON: jsonerror.NotFound(err.Error()),
+		}
+	} else if err != nil {
+		return httputil.LogThenError(req, err)
 	}
 
-	stateKey, reason, reqErr := getMembershipStateKey(body, device, membership)
-	if reqErr != nil {
-		return *reqErr
+	// If an invite has been stored on an identity server, it means that a
+	// m.room.third_party_invite event has been emitted and that we shouldn't
+	// emit a m.room.member one.
+	if inviteStored {
+		return util.JSONResponse{
+			Code: 200,
+			JSON: struct{}{},
+		}
+	}
+
+	event, err := buildMembershipEvent(
+		body, accountDB, device, membership, roomID, cfg, queryAPI,
+	)
+	if err == errMissingUserID {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.BadJSON(err.Error()),
+		}
+	} else if err == events.ErrRoomNoExists {
+		return util.JSONResponse{
+			Code: 404,
+			JSON: jsonerror.NotFound(err.Error()),
+		}
+	} else if err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	if err := producer.SendEvents([]gomatrixserverlib.Event{*event}, cfg.Matrix.ServerName); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: struct{}{},
+	}
+}
+
+func buildMembershipEvent(
+	body threepid.MembershipRequest, accountDB *accounts.Database,
+	device *authtypes.Device, membership string, roomID string, cfg config.Dendrite,
+	queryAPI api.RoomserverQueryAPI,
+) (*gomatrixserverlib.Event, error) {
+	stateKey, reason, err := getMembershipStateKey(body, device, membership)
+	if err != nil {
+		return nil, err
 	}
 
 	profile, err := loadProfile(stateKey, cfg, accountDB)
 	if err != nil {
-		return httputil.LogThenError(req, err)
+		return nil, err
 	}
 
 	builder := gomatrixserverlib.EventBuilder{
@@ -80,27 +141,10 @@ func SendMembership(
 	}
 
 	if err = builder.SetContent(content); err != nil {
-		return httputil.LogThenError(req, err)
-	}
-
-	event, err := events.BuildEvent(&builder, cfg, queryAPI, nil)
-	if err == events.ErrRoomNoExists {
-		return util.JSONResponse{
-			Code: 404,
-			JSON: jsonerror.NotFound(err.Error()),
-		}
-	} else if err != nil {
-		return httputil.LogThenError(req, err)
-	}
-
-	if err := producer.SendEvents([]gomatrixserverlib.Event{*event}, cfg.Matrix.ServerName); err != nil {
-		return httputil.LogThenError(req, err)
+		return nil, err
 	}
 
-	return util.JSONResponse{
-		Code: 200,
-		JSON: struct{}{},
-	}
+	return events.BuildEvent(&builder, cfg, queryAPI, nil)
 }
 
 // loadProfile lookups the profile of a given user from the database and returns
@@ -130,16 +174,13 @@ func loadProfile(userID string, cfg config.Dendrite, accountDB *accounts.Databas
 // returns a JSONResponse with a corresponding error code and message.
 func getMembershipStateKey(
 	body threepid.MembershipRequest, device *authtypes.Device, membership string,
-) (stateKey string, reason string, response *util.JSONResponse) {
+) (stateKey string, reason string, err error) {
 	if membership == "ban" || membership == "unban" || membership == "kick" || membership == "invite" {
 		// If we're in this case, the state key is contained in the request body,
 		// possibly along with a reason (for "kick" and "ban") so we need to parse
 		// it
 		if body.UserID == "" {
-			response = &util.JSONResponse{
-				Code: 400,
-				JSON: jsonerror.BadJSON("'user_id' must be supplied."),
-			}
+			err = errMissingUserID
 			return
 		}
 
diff --git a/src/github.com/matrix-org/dendrite/common/config/config.go b/src/github.com/matrix-org/dendrite/common/config/config.go
index 8d76a03d..86234b8d 100644
--- a/src/github.com/matrix-org/dendrite/common/config/config.go
+++ b/src/github.com/matrix-org/dendrite/common/config/config.go
@@ -70,6 +70,10 @@ type Dendrite struct {
 		// by remote servers.
 		// Defaults to 24 hours.
 		KeyValidityPeriod time.Duration `yaml:"key_validity_period"`
+		// List of domains that the server will trust as identity servers to
+		// verify third-party identifiers.
+		// Defaults to an empty array.
+		TrustedIDServers []string `yaml:"trusted_third_party_id_servers"`
 	} `yaml:"matrix"`
 
 	// The configuration specific to the media repostitory.
@@ -273,6 +277,10 @@ func (config *Dendrite) setDefaults() {
 		config.Matrix.KeyValidityPeriod = 24 * time.Hour
 	}
 
+	if config.Matrix.TrustedIDServers == nil {
+		config.Matrix.TrustedIDServers = []string{}
+	}
+
 	if config.Media.MaxThumbnailGenerators == 0 {
 		config.Media.MaxThumbnailGenerators = 10
 	}