From a5e70cbd71a8f706ac8c049888039ae72c225d57 Mon Sep 17 00:00:00 2001
From: Jyoti Puri <jyotipuri@gmail.com>
Date: Fri, 2 Dec 2022 21:08:12 +0530
Subject: [PATCH] Adding middleware to filter out duplicate requests from DAPP
 (#16730)

---
 .../lib/createDupeReqFilterMiddleware.js      | 23 ++++++++++++++
 .../lib/createDupeReqFilterMiddleware.test.js | 30 +++++++++++++++++++
 app/scripts/metamask-controller.js            |  5 ++++
 3 files changed, 58 insertions(+)
 create mode 100644 app/scripts/lib/createDupeReqFilterMiddleware.js
 create mode 100644 app/scripts/lib/createDupeReqFilterMiddleware.test.js

diff --git a/app/scripts/lib/createDupeReqFilterMiddleware.js b/app/scripts/lib/createDupeReqFilterMiddleware.js
new file mode 100644
index 000000000..556e71c18
--- /dev/null
+++ b/app/scripts/lib/createDupeReqFilterMiddleware.js
@@ -0,0 +1,23 @@
+import log from 'loglevel';
+
+/**
+ * Returns a middleware that filters out requests already seen
+ *
+ * @returns {Function}
+ */
+export default function createDupeReqFilterMiddleware() {
+  const processedRequestId = [];
+  return function filterDuplicateRequestMiddleware(
+    /** @type {any} */ req,
+    /** @type {any} */ _res,
+    /** @type {Function} */ next,
+    /** @type {Function} */ end,
+  ) {
+    if (processedRequestId.indexOf(req.id) >= 0) {
+      log.info(`RPC request with id ${req.id} already seen.`);
+      return end();
+    }
+    processedRequestId.push(req.id);
+    return next();
+  };
+}
diff --git a/app/scripts/lib/createDupeReqFilterMiddleware.test.js b/app/scripts/lib/createDupeReqFilterMiddleware.test.js
new file mode 100644
index 000000000..a8e3cfcb9
--- /dev/null
+++ b/app/scripts/lib/createDupeReqFilterMiddleware.test.js
@@ -0,0 +1,30 @@
+import createDupeReqFilterMiddleware from './createDupeReqFilterMiddleware';
+
+describe('createDupeReqFilterMiddleware', () => {
+  it('call function next if request is seen first time', () => {
+    const filterFn = createDupeReqFilterMiddleware();
+    const request = { id: 1 };
+    const nextMock = jest.fn();
+    const endMock = jest.fn();
+
+    filterFn(request, undefined, nextMock, endMock);
+
+    expect(nextMock).toBeCalledTimes(1);
+    expect(endMock).not.toBeCalled();
+  });
+
+  it('call function end if request is seen second time', () => {
+    const filterFn = createDupeReqFilterMiddleware();
+    const request = { id: 1 };
+    const nextMock = jest.fn();
+    const endMock = jest.fn();
+
+    filterFn(request, undefined, nextMock, endMock);
+    expect(nextMock).toBeCalledTimes(1);
+    expect(endMock).not.toBeCalled();
+
+    filterFn(request, undefined, nextMock, endMock);
+    expect(nextMock).toBeCalledTimes(1);
+    expect(endMock).toBeCalledTimes(1);
+  });
+});
diff --git a/app/scripts/metamask-controller.js b/app/scripts/metamask-controller.js
index 68df9b46c..d07f58b62 100644
--- a/app/scripts/metamask-controller.js
+++ b/app/scripts/metamask-controller.js
@@ -113,6 +113,7 @@ import {
 } from './detect-multiple-instances';
 import ComposableObservableStore from './lib/ComposableObservableStore';
 import AccountTracker from './lib/account-tracker';
+import createDupeReqFilterMiddleware from './lib/createDupeReqFilterMiddleware';
 import createLoggerMiddleware from './lib/createLoggerMiddleware';
 import {
   createMethodMiddleware,
@@ -3730,6 +3731,10 @@ export default class MetamaskController extends EventEmitter {
       engine.emit('notification', message),
     );
 
+    if (isManifestV3) {
+      engine.push(createDupeReqFilterMiddleware());
+    }
+
     // append origin to each request
     engine.push(createOriginMiddleware({ origin }));