[wrangler] fix: listen on loopback for wrangler dev port check and login

The `wrangler dev` port availability check triggers a firewall prompt on
macOS while it briefly opens and closes listeners. The OAuth callback
server from `wrangler login` has the same issue.

Fix both cases by listening on the loopback address only by default.

Relates to cloudflare#4430

.changeset/smart-owls-jog.md

@@ -0,0 +1,10 @@
+---
+"wrangler": patch
+---
+
+fix: listen on loopback for wrangler dev port check and login
+
+Avoid listening on the wildcard address by default to reduce the attacker's
+surface and avoid firewall prompts on macOS.
+
+Relates to #4430.

packages/wrangler/src/dev.tsx

@@ -626,12 +626,16 @@ export async function startApiDev(args: StartDevOptions) {
 	};
 }
 /**
+ * Get an available TCP port number.
+ *
  * Avoiding calling `getPort()` multiple times by memoizing the first result.
  */
-function memoizeGetPort(defaultPort?: number) {
+function memoizeGetPort(defaultPort: number, host: string) {
 	let portValue: number;
 	return async () => {
-		return portValue || (portValue = await getPort({ port: defaultPort }));
+		// Check a specific host to avoid probing all local addresses.
+		portValue = portValue ?? (await getPort({ port: defaultPort, host: host }));
+		return portValue;
 	};
 }
 /**
@@ -705,14 +709,15 @@ async function validateDevServerSettings(
 	);
 
 	const { zoneId, host, routes } = await getZoneIdHostAndRoutes(args, config);
-	const getLocalPort = memoizeGetPort(DEFAULT_LOCAL_PORT);
-	const getInspectorPort = memoizeGetPort(DEFAULT_INSPECTOR_PORT);
+	const initialIp = args.ip || config.dev.ip;
+	const getLocalPort = memoizeGetPort(DEFAULT_LOCAL_PORT, initialIp);
+	const getInspectorPort = memoizeGetPort(DEFAULT_INSPECTOR_PORT, "localhost");
 
 	// Our inspector proxy server will be binding to the result of
 	// `getInspectorPort`. If we attempted to bind workerd to the same inspector
 	// port, we'd get a port already in use error. Therefore, generate a new port
 	// for our runtime to bind its inspector service to.
-	const getRuntimeInspectorPort = memoizeGetPort();
+	const getRuntimeInspectorPort = memoizeGetPort(0, "localhost");
 
 	if (config.services && config.services.length > 0) {
 		logger.warn(

packages/wrangler/src/dev/proxy.ts

@@ -154,7 +154,8 @@ export async function startPreviewServer({
 			accessTokenRef,
 		});
 
-		await waitForPortToBeAvailable(port, {
+		const listenCheckIp = ip === "*" ? "0.0.0.0" : ip;
+		await waitForPortToBeAvailable(port, listenCheckIp, {
 			retryPeriod: 200,
 			timeout: 2000,
 			abortSignal: abortController.signal,
@@ -295,7 +296,7 @@ export function usePreviewServer({
 			return;
 		}
 
-		waitForPortToBeAvailable(port, {
+		waitForPortToBeAvailable(port, listenCheckIp, {
 			retryPeriod: 200,
 			timeout: 2000,
 			abortSignal: abortController.signal,
@@ -636,6 +637,7 @@ function createStreamHandler(
  */
 export async function waitForPortToBeAvailable(
 	port: number,
+	host: string,
 	options: { retryPeriod: number; timeout: number; abortSignal: AbortSignal }
 ): Promise<void> {
 	return new Promise((resolve, reject) => {
@@ -686,7 +688,7 @@ export async function waitForPortToBeAvailable(
 					doReject(err);
 				}
 			});
-			server.listen(port, () =>
+			server.listen(port, host, () =>
 				terminator
 					.terminate()
 					.then(doResolve, () =>

packages/wrangler/src/user/user.ts

@@ -1014,7 +1014,7 @@ export async function login(
 			}
 		});
 
-		server.listen(8976);
+		server.listen(8976, "localhost");
 	});
 	if (props?.browser) {
 		logger.log(`Opening a link in your default browser: ${urlToOpen}`);