✨ Fully rewrite relay

src/utils/isLocalhost.ts

@@ -0,0 +1,39 @@
+export function isLocalhost(
+  req: Request,
+  connInfo?: Deno.ServeHandlerInfo,
+): boolean {
+  if (connInfo?.remoteAddr) {
+    const remoteAddr = connInfo.remoteAddr;
+    if (remoteAddr.transport === 'tcp') {
+      const hostname = remoteAddr.hostname;
+      return hostname === '127.0.0.1' || hostname === '::1';
+    }
+    if (remoteAddr.transport === 'unix') {
+      return true;
+    }
+  }
+  const url = new URL(req.url);
+  const hostname = url.hostname;
+  if (hostname === '127.0.0.1' || hostname === '::1') {
+    return true;
+  }
+  if (hostname === 'localhost') {
+    const suspiciousHeaders = [
+      'x-forwarded-for',
+      'x-forwarded-host',
+      'x-real-ip',
+      'cf-connecting-ip',
+      'x-cluster-client-ip',
+    ];
+
+    for (const header of suspiciousHeaders) {
+      if (req.headers.get(header)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  return false;
+}