feat(vercel): skew protection

.changeset/honest-games-bathe.md

@@ -0,0 +1,5 @@
+---
+"@astrojs/vercel": minor
+---
+
+Implements the vercel skew protection

packages/integrations/vercel/src/serverless/adapter.ts

@@ -72,16 +72,18 @@ function getAdapter({
 	edgeMiddleware,
 	functionPerRoute,
 	middlewareSecret,
+	skewProtection,
 }: {
 	edgeMiddleware: boolean;
 	functionPerRoute: boolean;
 	middlewareSecret: string;
+	skewProtection: boolean;
 }): AstroAdapter {
 	return {
 		name: PACKAGE_NAME,
 		serverEntrypoint: `${PACKAGE_NAME}/entrypoint`,
 		exports: ['default'],
-		args: { middlewareSecret },
+		args: { middlewareSecret, skewProtection },
 		adapterFeatures: {
 			edgeMiddleware,
 			functionPerRoute,
@@ -139,6 +141,10 @@ export interface VercelServerlessConfig {
 
 	/** Whether to cache on-demand rendered pages in the same way as static files. */
 	isr?: boolean | VercelISRConfig;
+	/**
+	 * It enables Vercel skew protection: https://vercel.com/docs/deployments/skew-protection
+	 */
+	skewProtection?: boolean;
 }
 
 interface VercelISRConfig {
@@ -180,6 +186,7 @@ export default function vercelServerless({
 	edgeMiddleware = false,
 	maxDuration,
 	isr = false,
+	skewProtection = false,
 }: VercelServerlessConfig = {}): AstroIntegration {
 	if (maxDuration) {
 		if (typeof maxDuration !== 'number') {
@@ -277,7 +284,9 @@ export default function vercelServerless({
 					);
 				}
 
-				setAdapter(getAdapter({ functionPerRoute, edgeMiddleware, middlewareSecret }));
+				setAdapter(
+					getAdapter({ functionPerRoute, edgeMiddleware, middlewareSecret, skewProtection })
+				);
 
 				_config = config;
 				_buildTempFolder = config.build.server;

packages/integrations/vercel/src/serverless/entrypoint.ts

@@ -12,7 +12,7 @@ applyPolyfills();
 
 export const createExports = (
 	manifest: SSRManifest,
-	{ middlewareSecret }: { middlewareSecret: string }
+	{ middlewareSecret, skewProtection }: { middlewareSecret: string; skewProtection: boolean }
 ) => {
 	const app = new NodeApp(manifest);
 	const handler = async (req: IncomingMessage, res: ServerResponse) => {
@@ -38,6 +38,11 @@ export const createExports = (
 		// hide the secret from the rest of user code
 		delete req.headers[ASTRO_MIDDLEWARE_SECRET_HEADER];
 
+		// https://vercel.com/docs/deployments/skew-protection#supported-frameworks
+		if (skewProtection && process.env.VERCEL_SKEW_PROTECTION_ENABLED === '1') {
+			req.headers['x-deployment-id'] = process.env.VERCEL_DEPLOYMENT_ID;
+		}
+
 		const webResponse = await app.render(req, { addCookieHeader: true, clientAddress, locals });
 		await NodeApp.writeResponse(webResponse, res);
 	};