feat: Add feature flag to disable Snap installation

packages/snaps-controllers/coverage.json

@@ -1,6 +1,6 @@
 {
   "branches": 92.08,
   "functions": 96.74,
-  "lines": 97.95,
-  "statements": 97.63
+  "lines": 97.96,
+  "statements": 97.64
 }

packages/snaps-controllers/src/snaps/SnapController.test.tsx

@@ -909,6 +909,26 @@
     snapController.destroy();
   });
 
+  it('throws an error if the installation is disabled during installSnaps', async () => {
+    const controller = getSnapController(
+      getSnapControllerOptions({
+        featureFlags: {
+          disableSnapInstallation: true,
+        },
+      }),
+    );
+
+    await expect(
+      controller.installSnaps(MOCK_ORIGIN, {
+        [MOCK_SNAP_ID]: {},
+      }),
+    ).rejects.toThrow(
+      'Installing Snaps is currently disabled in this version of MetaMask.',
+    );
+
+    controller.destroy();
+  });
+
   it('throws an error if the platform is disabled during installSnaps', async () => {
     const controller = getSnapController(
       getSnapControllerOptions({
@@ -1729,7 +1749,7 @@
   });
 
   // This isn't stable in CI unfortunately
   it.skip('throws if the Snap is terminated while executing', async () => {
     const { manifest, sourceCode, svgIcon } =
       await getMockSnapFilesWithUpdatedChecksum({
         sourceCode: `
@@ -4576,6 +4596,79 @@
       snapController.destroy();
     });
 
+    it('supports preinstalled snaps when Snap installation is disabled', async () => {
+      const rootMessenger = getControllerMessenger();
+      jest.spyOn(rootMessenger, 'call');
+
+      // The snap should not have permission initially
+      rootMessenger.registerActionHandler(
+        'PermissionController:getPermissions',
+        () => ({}),
+      );
+
+      const preinstalledSnaps = [
+        {
+          snapId: MOCK_SNAP_ID,
+          manifest: getSnapManifest(),
+          files: [
+            {
+              path: DEFAULT_SOURCE_PATH,
+              value: stringToBytes(DEFAULT_SNAP_BUNDLE),
+            },
+            {
+              path: DEFAULT_ICON_PATH,
+              value: stringToBytes(DEFAULT_SNAP_ICON),
+            },
+          ],
+        },
+      ];
+
+      const snapControllerOptions = getSnapControllerWithEESOptions({
+        preinstalledSnaps,
+        rootMessenger,
+      });
+      const [snapController] = getSnapControllerWithEES(snapControllerOptions);
+
+      expect(rootMessenger.call).toHaveBeenCalledWith(
+        'PermissionController:grantPermissions',
+        {
+          approvedPermissions: {
+            'endowment:rpc': {
+              caveats: [
+                { type: 'rpcOrigin', value: { dapps: false, snaps: true } },
+              ],
+            },
+            // eslint-disable-next-line @typescript-eslint/naming-convention
+            snap_dialog: {},
+          },
+          subject: { origin: MOCK_SNAP_ID },
+        },
+      );
+
+      // After install the snap should have permissions
+      rootMessenger.registerActionHandler(
+        'PermissionController:getPermissions',
+        () => MOCK_SNAP_PERMISSIONS,
+      );
+
+      expect(
+        await snapController.installSnaps(MOCK_ORIGIN, {
+          [MOCK_SNAP_ID]: {},
+        }),
+      ).toStrictEqual({ [MOCK_SNAP_ID]: getTruncatedSnap() });
+
+      const result = await snapController.handleRequest({
+        snapId: MOCK_SNAP_ID,
+        origin: MOCK_ORIGIN,
+        request: { method: 'foo' },
+        handler: HandlerType.OnRpcRequest,
+      });
+
+      expect(result).toContain('foo');
+
+      snapController.destroy();
+    });
+
     it('supports updating preinstalled snaps', async () => {
       const rootMessenger = getControllerMessenger();
       jest.spyOn(rootMessenger, 'call');

packages/snaps-controllers/src/snaps/SnapController.ts

@@ -574,6 +574,7 @@ type SnapControllerMessenger = RestrictedControllerMessenger<
 type FeatureFlags = {
   requireAllowlist?: boolean;
   allowLocalSnaps?: boolean;
+  disableSnapInstallation?: boolean;
 };
 
 type DynamicFeatureFlags = {
@@ -1324,6 +1325,16 @@ export class SnapController extends BaseController<
     }
   }
 
+  /**
+   * Asserts whether new Snaps are allowed to be installed.
+   */
+  #assertCanInstallSnaps() {
+    assert(
+      this.#featureFlags.disableSnapInstallation !== true,
+      'Installing Snaps is currently disabled in this version of MetaMask.',
+    );
+  }
+
   /**
    * Asserts whether the Snaps platform is allowed to run.
    */
@@ -2279,6 +2290,8 @@ export class SnapController extends BaseController<
       );
     }
 
+    this.#assertCanInstallSnaps();
+
     let pendingApproval = this.#createApproval({
       origin,
       snapId,
@@ -2423,6 +2436,7 @@ export class SnapController extends BaseController<
     newVersionRange: string = DEFAULT_REQUESTED_SNAP_VERSION,
     emitEvent = true,
   ): Promise<TruncatedSnap> {
+    this.#assertCanInstallSnaps();
     this.#assertCanUsePlatform();
     if (!isValidSemVerRange(newVersionRange)) {
       throw new Error(