Add config param to disable client wellknown fetch (#34084)

* Add enable_client_well_known_lookups config option

Signed-off-by: David Langley <langley.dave@gmail.com>

* Gate client .well-known poll on enable_client_well_known_lookups

Signed-off-by: David Langley <langley.dave@gmail.com>

* Gate MatrixRTC foci well-known fallback on enable_client_well_known_lookups

Signed-off-by: David Langley <langley.dave@gmail.com>

---------

Signed-off-by: David Langley <langley.dave@gmail.com>
Co-authored-by: David Langley <langley.dave@gmail.com>

apps/web/src/MatrixClientPeg.test.ts

@@ -15,6 +15,7 @@ import fetchMock from "@fetch-mock/vitest";
 import { advanceDateAndTime, stubClient, createTestClient } from "test-utils";
 
 import { type IMatrixClientPeg, MatrixClientPeg as peg } from "./MatrixClientPeg";
+import SdkConfig from "./SdkConfig";
 
 vi.useFakeTimers();
 
@@ -116,5 +117,30 @@ describe("MatrixClientPeg", () => {
             await testPeg.start();
             expect(mockInitRustCrypto).toHaveBeenCalledTimes(1);
         });
+
+        it("should poll the client well-known by default", async () => {
+            vi.spyOn(testPeg.safeGet(), "initRustCrypto").mockResolvedValue(undefined);
+            const startClient = vi.spyOn(testPeg.safeGet(), "startClient").mockResolvedValue(undefined);
+
+            await testPeg.start();
+
+            const opts = startClient.mock.calls[0][0];
+            expect(opts?.clientWellKnownPollPeriod).toBe(2 * 60 * 60);
+        });
+
+        it("should not poll the client well-known when enable_client_well_known_lookups is false", async () => {
+            const sdkConfigGet = SdkConfig.get;
+            vi.spyOn(SdkConfig, "get").mockImplementation((key?: any, altCaseName?: string): any => {
+                if (key === "enable_client_well_known_lookups") return false;
+                return sdkConfigGet(key, altCaseName);
+            });
+            vi.spyOn(testPeg.safeGet(), "initRustCrypto").mockResolvedValue(undefined);
+            const startClient = vi.spyOn(testPeg.safeGet(), "startClient").mockResolvedValue(undefined);
+
+            await testPeg.start();
+
+            const opts = startClient.mock.calls[0][0];
+            expect(opts?.clientWellKnownPollPeriod).toBeUndefined();
+        });
     });
 });

apps/web/src/MatrixClientPeg.ts

@@ -263,7 +263,11 @@ class MatrixClientPegClass implements IMatrixClientPeg {
         // the react sdk doesn't work without this, so don't allow
         opts.pendingEventOrdering = PendingEventOrdering.Detached;
         opts.lazyLoadMembers = true;
-        opts.clientWellKnownPollPeriod = 2 * 60 * 60; // 2 hours
+        // Poll the user's `<server_name>/.well-known/matrix/client` for client config unless disabled by config.
+        // Leaving `clientWellKnownPollPeriod` unset stops the SDK fetching it.
+        if (SdkConfig.get("enable_client_well_known_lookups")) {
+            opts.clientWellKnownPollPeriod = 2 * 60 * 60; // 2 hours
+        }
         opts.threadSupport = true;
         if (SettingsStore.getValue("feature_user_status")) {
             opts.unstableMSC4429SyncUserProfileFields = ["org.matrix.msc4426.status"];

apps/web/src/SdkConfig.ts

@@ -30,6 +30,7 @@ export const DEFAULTS = {
     integrations_rest_url: "https://scalar.vector.im/api",
     show_labs_settings: false,
     force_verification: false,
+    enable_client_well_known_lookups: true,
 
     jitsi: {
         preferred_domain: "meet.element.io",

apps/web/src/stores/CallStore.ts

@@ -16,6 +16,7 @@ import { AsyncStoreWithClient } from "./AsyncStoreWithClient";
 import WidgetStore from "./WidgetStore";
 import SettingsStore from "../settings/SettingsStore";
 import { SettingLevel } from "../settings/SettingLevel";
+import SdkConfig from "../SdkConfig";
 import { Call, CallEvent, ConnectionState } from "../models/Call";
 
 export enum CallStoreEvent {
@@ -71,10 +72,13 @@ export class CallStore extends AsyncStoreWithClient<EmptyObject> {
         }
         // See https://github.com/matrix-org/matrix-spec-proposals/blob/d61969a9a3696b6c54d7987b1643b5bc03670927/proposals/4143-matrix-rtc.md#discovery-of-foci-using-well-knownmatrixclient
         // This well-known option has since been removed from the spec but is still widely deployed.
-        await this.matrixClient.waitForClientWellKnown();
-        const foci = this.matrixClient.getClientWellKnown()?.["org.matrix.msc4143.rtc_foci"];
-        if (Array.isArray(foci)) {
-            foci.forEach((foci) => this.configuredMatrixRTCTransports.add(foci));
+        // Reading it can be disabled via config; the modern endpoint above is unaffected.
+        if (SdkConfig.get("enable_client_well_known_lookups")) {
+            await this.matrixClient.waitForClientWellKnown();
+            const foci = this.matrixClient.getClientWellKnown()?.["org.matrix.msc4143.rtc_foci"];
+            if (Array.isArray(foci)) {
+                foci.forEach((foci) => this.configuredMatrixRTCTransports.add(foci));
+            }
         }
         this.emit(CallStoreEvent.TransportsUpdated);
     }

apps/web/test/unit-tests/stores/CallStore-test.ts

@@ -11,6 +11,7 @@ import { type MockedObject } from "jest-mock";
 
 import { ElementCall } from "../../../src/models/Call";
 import { CallStore } from "../../../src/stores/CallStore";
+import SdkConfig from "../../../src/SdkConfig";
 import {
     setUpClientRoomAndStores,
     cleanUpClientRoomAndStores,
@@ -66,4 +67,20 @@ describe("CallStore", () => {
             { type: "type-d", other_data: "baz" },
         ]);
     });
+    it("does not fall back to client well-known when enable_client_well_known_lookups is false", async () => {
+        const sdkConfigGet = SdkConfig.get;
+        jest.spyOn(SdkConfig, "get").mockImplementation((key?: any, altCaseName?: string): any => {
+            if (key === "enable_client_well_known_lookups") return false;
+            return sdkConfigGet(key, altCaseName);
+        });
+        client._unstable_getRTCTransports.mockResolvedValue([{ type: "type-a", some_data: "value" }]);
+        client.getClientWellKnown.mockReturnValue({
+            "org.matrix.msc4143.rtc_foci": [{ type: "type-c", other_data: "bar" }],
+        });
+        await setupAsyncStoreWithClient(CallStore.instance, client);
+        // Only the modern endpoint contributes; the legacy well-known fallback is skipped entirely.
+        expect(CallStore.instance.getConfiguredRTCTransports()).toEqual([{ type: "type-a", some_data: "value" }]);
+        expect(client.waitForClientWellKnown).not.toHaveBeenCalled();
+        expect(client.getClientWellKnown).not.toHaveBeenCalled();
+    });
 });

docs/config.md

@@ -57,6 +57,12 @@ If both `default_server_config` and `default_server_name` are used, Element will
 information using `.well-known`, and if that fails, take `default_server_config` as the homeserver connection
 information.
 
+1. `enable_client_well_known_lookups`: Controls whether Element makes runtime requests to the logged-in user's
+   [`<server_name>/.well-known/matrix/...`](https://spec.matrix.org/latest/client-server-api/#getwell-knownmatrixclient)
+   endpoints (for example, polling for client configuration after login). Set it to `false` to stop Element making these
+   requests, so it only contacts the homeserver base URL; the `well_known` object returned inline in the `/login` response
+   is unaffected. Defaults to `true`.
+
 ## Labs flags
 
 Labs flags are optional, typically beta or in-development, features that can be turned on or off. The full range of

packages/shared-types/lib/config.json.d.ts

@@ -37,6 +37,14 @@ export interface WebConfigJson {
     disable_login_language_selector?: boolean;
     disable_3pid_login?: boolean;
 
+    /**
+     * Whether the app may make runtime requests to the user's `<server_name>/.well-known/matrix/...`
+     * endpoints (such as the post-login client well-known poll). Set to false to disable these, so the app
+     * only contacts the homeserver base URL. Does not affect the `well_known` returned inline in the
+     * `/login` response. Defaults to true.
+     */
+    enable_client_well_known_lookups?: boolean;
+
     brand?: string;
     branding?: {
         welcome_background_url?: string | string[]; // chosen at random if array