[7.12] [core.http] Cleanup catch-all route for paths with trailing sl…

…ashes. (#96889) (#97677)

* [core.http] Cleanup catch-all route for paths with trailing slashes. (#96889)

# Conflicts:
#	src/core/server/core_app/core_app.ts
#	src/core/server/core_app/integration_tests/core_app_routes.test.ts

* Fix eslint failures.

src/legacy/server/http/index.js

@@ -24,7 +24,7 @@ export default async function (kbnServer, server) {
     path: '/{p*}',
     handler: function (req, h) {
       const path = req.path;
-      if (path === '/' || path.charAt(path.length - 1) !== '/') {
+      if (path === '/' || path.charAt(path.length - 1) !== '/' || path.charAt(0) === '/') {
         throw Boom.notFound();
       }
 

src/legacy/server/http/integration_tests/index.test.js

@@ -0,0 +1,39 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import * as kbnTestServer from '../../../../core/test_helpers/kbn_server';
+
+describe('Core app routes', () => {
+  let root;
+
+  beforeAll(async function () {
+    root = kbnTestServer.createRoot({
+      plugins: { initialize: false },
+      server: {
+        basePath: '/base-path',
+      },
+    });
+
+    await root.setup();
+    await root.start();
+  });
+
+  afterAll(async function () {
+    await root.shutdown();
+  });
+
+  describe('`/{path*}` route', () => {
+    it('does not redirect if the path starts with `//`', async () => {
+      await kbnTestServer.request.get(root, '//some-path/').expect(404);
+    });
+
+    it('does not redirect if the path does not end with `/`', async () => {
+      await kbnTestServer.request.get(root, '/some-path').expect(404);
+    });
+  });
+});