MSC3967: Do not require UIA when first uploading cross signing keys

clientapi/routing/key_crosssigning.go

@@ -7,7 +7,12 @@
 package routing
 
 import (
+	"context"
 	"net/http"
+	"time"
+
+	"github.com/matrix-org/gomatrixserverlib/fclient"
+	"github.com/sirupsen/logrus"
 
 	"github.com/element-hq/dendrite/clientapi/auth"
 	"github.com/element-hq/dendrite/clientapi/auth/authtypes"
@@ -23,10 +28,15 @@ type crossSigningRequest struct {
 	Auth newPasswordAuth `json:"auth"`
 }
 
+type UploadKeysAPI interface {
+	QueryKeys(ctx context.Context, req *api.QueryKeysRequest, res *api.QueryKeysResponse)
+	api.UploadDeviceKeysAPI
+}
+
 func UploadCrossSigningDeviceKeys(
-	req *http.Request, userInteractiveAuth *auth.UserInteractive,
-	keyserverAPI api.ClientKeyAPI, device *api.Device,
-	accountAPI api.ClientUserAPI, cfg *config.ClientAPI,
+	req *http.Request,
+	keyserverAPI UploadKeysAPI, device *api.Device,
+	accountAPI auth.GetAccountByPassword, cfg *config.ClientAPI,
 ) util.JSONResponse {
 	uploadReq := &crossSigningRequest{}
 	uploadRes := &api.PerformUploadDeviceKeysResponse{}
@@ -35,32 +45,59 @@ func UploadCrossSigningDeviceKeys(
 	if resErr != nil {
 		return *resErr
 	}
-	sessionID := uploadReq.Auth.Session
-	if sessionID == "" {
-		sessionID = util.RandomString(sessionIDLength)
-	}
-	if uploadReq.Auth.Type != authtypes.LoginTypePassword {
+
+	// Query existing keys to determine if UIA is required
+	keyResp := api.QueryKeysResponse{}
+	keyserverAPI.QueryKeys(req.Context(), &api.QueryKeysRequest{
+		UserID:        device.UserID,
+		UserToDevices: map[string][]string{device.UserID: {device.ID}},
+		Timeout:       time.Second * 10,
+	}, &keyResp)
+
+	if keyResp.Error != nil {
+		logrus.WithError(keyResp.Error).Error("Failed to query keys")
 		return util.JSONResponse{
-			Code: http.StatusUnauthorized,
-			JSON: newUserInteractiveResponse(
-				sessionID,
-				[]authtypes.Flow{
-					{
-						Stages: []authtypes.LoginType{authtypes.LoginTypePassword},
-					},
-				},
-				nil,
-			),
+			Code: http.StatusBadRequest,
+			JSON: spec.Unknown(keyResp.Error.Error()),
 		}
 	}
-	typePassword := auth.LoginTypePassword{
-		GetAccountByPassword: accountAPI.QueryAccountByPassword,
-		Config:               cfg,
+
+	existingMasterKey, hasMasterKey := keyResp.MasterKeys[device.UserID]
+	requireUIA := false
+	if hasMasterKey {
+		// If we have a master key, check if any of the existing keys differ. If they do,
+		// we need to re-authenticate the user.
+		requireUIA = keysDiffer(existingMasterKey, keyResp, uploadReq, device.UserID)
 	}
-	if _, authErr := typePassword.Login(req.Context(), &uploadReq.Auth.PasswordRequest); authErr != nil {
-		return *authErr
+
+	if requireUIA {
+		sessionID := uploadReq.Auth.Session
+		if sessionID == "" {
+			sessionID = util.RandomString(sessionIDLength)
+		}
+		if uploadReq.Auth.Type != authtypes.LoginTypePassword {
+			return util.JSONResponse{
+				Code: http.StatusUnauthorized,
+				JSON: newUserInteractiveResponse(
+					sessionID,
+					[]authtypes.Flow{
+						{
+							Stages: []authtypes.LoginType{authtypes.LoginTypePassword},
+						},
+					},
+					nil,
+				),
+			}
+		}
+		typePassword := auth.LoginTypePassword{
+			GetAccountByPassword: accountAPI,
+			Config:               cfg,
+		}
+		if _, authErr := typePassword.Login(req.Context(), &uploadReq.Auth.PasswordRequest); authErr != nil {
+			return *authErr
+		}
+		sessions.addCompletedSessionStage(sessionID, authtypes.LoginTypePassword)
 	}
-	sessions.addCompletedSessionStage(sessionID, authtypes.LoginTypePassword)
 
 	uploadReq.UserID = device.UserID
 	keyserverAPI.PerformUploadDeviceKeys(req.Context(), &uploadReq.PerformUploadDeviceKeysRequest, uploadRes)
@@ -96,6 +133,21 @@ func UploadCrossSigningDeviceKeys(
 	}
 }
 
+func keysDiffer(existingMasterKey fclient.CrossSigningKey, keyResp api.QueryKeysResponse, uploadReq *crossSigningRequest, userID string) bool {
+	masterKeyEqual := existingMasterKey.Equal(&uploadReq.MasterKey)
+	if !masterKeyEqual {
+		return true
+	}
+	existingSelfSigningKey := keyResp.SelfSigningKeys[userID]
+	selfSigningEqual := existingSelfSigningKey.Equal(&uploadReq.SelfSigningKey)
+	if !selfSigningEqual {
+		return true
+	}
+	existingUserSigningKey := keyResp.UserSigningKeys[userID]
+	userSigningEqual := existingUserSigningKey.Equal(&uploadReq.UserSigningKey)
+	return !userSigningEqual
+}
+
 func UploadCrossSigningDeviceSignatures(req *http.Request, keyserverAPI api.ClientKeyAPI, device *api.Device) util.JSONResponse {
 	uploadReq := &api.PerformUploadDeviceSignaturesRequest{}
 	uploadRes := &api.PerformUploadDeviceSignaturesResponse{}