fix: Handle Proxy WS upgrade manually for WS handshakes

Signed-off-by: Carlos Esteban Lopez <lcarlosesteb@vmware.com>

.changeset/clean-icons-wonder.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-kubernetes-backend': patch
+---
+
+Handle Proxy WS upgrade manually for WS handshakes

plugins/kubernetes-backend/package.json

@@ -75,6 +75,7 @@
     "express-promise-router": "^4.1.0",
     "fs-extra": "10.1.0",
     "helmet": "^6.0.0",
+    "http-proxy": "^1.18.1",
     "http-proxy-middleware": "^2.0.6",
     "lodash": "^4.17.21",
     "luxon": "^3.0.0",

plugins/kubernetes-backend/src/service/KubernetesProxy.test.ts

@@ -769,10 +769,6 @@ describe('KubernetesProxy', () => {
         ),
       );
 
-      // Prepopulate the proxy so the WebSocket upgrade can happen, result doesn't actually matter
-      const result = await fetch(wsProxyAddress.replace('ws', 'http'));
-      expect(result.ok).toBeFalsy();
-
       const webSocket = new WebSocket(wsProxyAddress);
 
       const connectMessagePromise = eventPromiseFactory(webSocket, 'message');

plugins/kubernetes-backend/src/service/KubernetesProxy.ts

@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 import {
   ErrorResponseBody,
   ForwardedError,
@@ -24,16 +23,19 @@ import {
 import { getBearerTokenFromAuthorizationHeader } from '@backstage/plugin-auth-node';
 import { kubernetesProxyPermission } from '@backstage/plugin-kubernetes-common';
 import {
-  PermissionEvaluator,
   AuthorizeResult,
+  PermissionEvaluator,
 } from '@backstage/plugin-permission-common';
 import { bufferFromFileOrString } from '@kubernetes/client-node';
-import type { Request, RequestHandler } from 'express';
+import { IncomingMessage, ServerResponse } from 'http';
+import Server from 'http-proxy';
 import { createProxyMiddleware } from 'http-proxy-middleware';
 import { Logger } from 'winston';
 import { AuthenticationStrategy } from '../auth';
 import { ClusterDetails, KubernetesClustersSupplier } from '../types/types';
 
+import type { Request, RequestHandler } from 'express';
+
 export const APPLICATION_JSON: string = 'application/json';
 
 /**
@@ -121,7 +123,25 @@ export class KubernetesProxy {
       }
 
       const middleware = await this.getMiddleware(req);
-      middleware(req, res, next);
+      if (
+        req.header('connection')?.toLowerCase() === 'upgrade' &&
+        req.header('upgrade')?.toLowerCase() === 'websocket'
+      ) {
+        type IPartialUpgradeHandler = (
+          ...args: Partial<
+            Parameters<
+              Server<IncomingMessage, ServerResponse<IncomingMessage>>['ws']
+            >
+          >
+        ) => void;
+        (
+          middleware as unknown as {
+            upgrade: IPartialUpgradeHandler;
+          }
+        ).upgrade(req, req.socket);
+      } else {
+        middleware(req, res, next);
+      }
     };
   }
 

yarn.lock

@@ -7651,6 +7651,7 @@ __metadata:
     express-promise-router: ^4.1.0
     fs-extra: 10.1.0
     helmet: ^6.0.0
+    http-proxy: ^1.18.1
     http-proxy-middleware: ^2.0.6
     lodash: ^4.17.21
     luxon: ^3.0.0