Fix dashboard redirects leaking internal port

apps/dashboard/src/middleware.test.ts

@@ -77,7 +77,7 @@ describe('dashboard middleware', () => {
 
     const response = middleware(request('http://dashboard:3001/dashboard/team') as never)
 
-    expect(response).toEqual({ kind: 'redirect', url: 'https://rentaldrivego.example:3001/dashboard/sign-in?redirect=%2Fdashboard%2Fteam' })
+    expect(response).toEqual({ kind: 'redirect', url: 'https://rentaldrivego.example/dashboard/sign-in?redirect=%2Fdashboard%2Fteam' })
   })
 
   it('uses trusted forwarded host/proto when building the dashboard sign-in redirect', async () => {
@@ -90,7 +90,7 @@ describe('dashboard middleware', () => {
       },
     }) as never)
 
-    expect(response).toEqual({ kind: 'redirect', url: 'https://workspace.customer.example:3001/dashboard/sign-in?redirect=%2Fdashboard%2Fbilling' })
+    expect(response).toEqual({ kind: 'redirect', url: 'https://workspace.customer.example/dashboard/sign-in?redirect=%2Fdashboard%2Fbilling' })
   })
 
   it('ignores internal forwarded hosts when building the dashboard sign-in redirect', async () => {
@@ -103,7 +103,7 @@ describe('dashboard middleware', () => {
       },
     }) as never)
 
-    expect(response).toEqual({ kind: 'redirect', url: 'https://market.example.com:3001/dashboard/sign-in?redirect=%2Fdashboard%2Ffleet' })
+    expect(response).toEqual({ kind: 'redirect', url: 'https://market.example.com/dashboard/sign-in?redirect=%2Fdashboard%2Ffleet' })
   })
 
   it('redirects signed-in users away from the sign-in page', async () => {

apps/dashboard/src/middleware.ts

@@ -38,16 +38,27 @@ function resolveProxyUrl(req: NextRequest, pathname: string): URL {
   if (forwardedHost && !isInternalHost(forwardedHost)) {
     url.host = forwardedHost
     url.protocol = (forwardedProto ?? 'http') + ':'
+    if (!hasExplicitPort(forwardedHost) || isInternalAppPort(url.port)) url.port = ''
   } else if (!isInternalHost(req.nextUrl.host)) {
     url.host = req.nextUrl.host
     url.protocol = req.nextUrl.protocol
+    if (!hasExplicitPort(req.nextUrl.host) || isInternalAppPort(url.port)) url.port = ''
   } else {
     url.host = storefrontOrigin.host
     url.protocol = storefrontOrigin.protocol
+    if (!hasExplicitPort(storefrontOrigin.host) || isInternalAppPort(url.port)) url.port = ''
   }
   return url
 }
 
+function hasExplicitPort(host: string): boolean {
+  return /^[^:]+:\d+$/.test(host)
+}
+
+function isInternalAppPort(port: string): boolean {
+  return ['3000', '3001', '3002', '3004', '4000'].includes(port)
+}
+
 function isInternalHost(host: string | null): boolean {
   if (!host) return false
   const hostname = host.split(':')[0]?.toLowerCase()