Function buildStrictModeAuthenticator

server/src/training-agent/index.ts:189–216

* Presence-gated authenticator for all `/mcp-strict*` routes. Accepts a lazy * signing authenticator so each route uses its own capability instance * (covers_content_digest varies per route and is baked at init time). * * Delegates to `requireAuthenticatedOrSigned` (5.7): bypass on valid bearer,

(lazyAuth: () => Authenticator)

 * surfaces RFC 9421 error codes on bad signatures.
 */
function buildStrictModeAuthenticator(lazyAuth: () => Authenticator): Authenticator | null {
  const bearerAuth = buildBearerAuthenticator();
  if (!bearerAuth) return null;
  return enforceSigningWhenWebhookAuthPresent(requireAuthenticatedOrSigned({
    signature: lazyAuth(),
    fallback: bearerAuth,
    requiredFor: STRICT_REQUIRED_FOR,
    resolveOperation: (req) => {
      // rawBody is populated by the production http.ts `verify` callback.
      // Fall back to req.body (already-parsed by express.json) when rawBody
      // is absent — e.g. in test harnesses that skip the verify callback.
      // Safe here because resolveOperation drives only the required_for
      // routing decision, not cryptographic verification.
      const raw = (req as { rawBody?: string }).rawBody;
      try {
        const body = raw
          ? JSON.parse(raw) as { method?: string; params?: { name?: string } }
          : (req as { body?: { method?: string; params?: { name?: string } } }).body;
        if (body && body.method === 'tools/call' && typeof body.params?.name === 'string') {
          return body.params.name;
        }
      } catch {
        // Transport rejects malformed JSON downstream.
      }
      return undefined;
    },
  }));
}

const defaultAuthenticator = buildDefaultAuthenticator();
const strictAuthenticator = buildStrictModeAuthenticator(lazyStrictSigningAuth);