feat(#707): secure Discord service ingress (#716)

apps/gateway/src/chat/chat.gateway-auth.ts

@@ -1,3 +1,4 @@
+import { timingSafeEqual } from 'node:crypto';
 import type { IncomingHttpHeaders } from 'node:http';
 import { fromNodeHeaders } from 'better-auth/node';
 
@@ -12,6 +13,19 @@ export interface SessionAuth {
   };
 }
 
+export function validateDiscordServiceToken(
+  candidate: unknown,
+  expected: string | undefined,
+): boolean {
+  if (typeof candidate !== 'string' || !expected) return false;
+  const candidateBuffer = Buffer.from(candidate);
+  const expectedBuffer = Buffer.from(expected);
+  return (
+    candidateBuffer.length === expectedBuffer.length &&
+    timingSafeEqual(candidateBuffer, expectedBuffer)
+  );
+}
+
 export async function validateSocketSession(
   headers: IncomingHttpHeaders,
   auth: SessionAuth,