import { RequestHandler } from 'express';
type RequireTrustedHostOptions = {
    /**
     * Port-agnostic hostnames permitted in the `Host` and `Origin` headers.
     * IPv6 entries must be bracketed, e.g. `[::1]`. Invalid entries cause
     * {@link requireTrustedHost} to throw at construction time (fail fast).
     */
    allowedHosts: string[];
};
/**
 * Loopback hostnames always trusted by {@link requireTrustedHost}. Stored
 * bracketed for IPv6 because `new URL('http://[::1]').hostname` returns `[::1]`.
 */
declare const DEFAULT_ALLOWED_HOSTS: string[];
/**
 * Build the list of hostnames trusted in the Host and Origin headers. Always
 * includes the loopback defaults, plus any names from `allowedHostsEnv`
 * (comma-separated), plus the configured `host` (so an explicit bind — loopback
 * alias like 127.0.1.1, a LAN IP, etc. — is always trusted). Bind wildcards
 * (0.0.0.0/::) are never added because they are never valid Host header values —
 * operators exposing on a wildcard must enumerate client hostnames via
 * ALLOWED_HOSTS.
 */
declare function buildAllowedHosts(host: string, allowedHostsEnv?: string): string[];
/**
 * Express middleware that rejects requests whose `Host` or `Origin` header is
 * not in the trusted allowlist. This is DNS-rebinding protection: a malicious
 * website that rebinds its domain to a victim's loopback address keeps its own
 * `Host`/`Origin`, so string-matching against the allowlist (we never DNS
 * resolve) blocks the request before it can reach the MCP transport.
 *
 * - Missing `Host` → 403.
 * - `Host` hostname not in the allowlist → 403.
 * - `Origin` absent → allowed (non-browser clients such as `mcp-remote`/`curl`
 *   send none; the browser attack path always sends one).
 * - `Origin` present but untrusted or unparseable → 403.
 *
 * Throws at construction time if `allowedHosts` contains an entry that isn't a
 * valid authority, so misconfiguration fails fast instead of becoming opaque
 * 403s at request time.
 */
declare function requireTrustedHost(options: RequireTrustedHostOptions): RequestHandler;
export { DEFAULT_ALLOWED_HOSTS, buildAllowedHosts, requireTrustedHost, type RequireTrustedHostOptions, };
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