/**
 * Twilio Webhook Signature Validation Middleware
 *
 * Validates that incoming requests are genuinely from Twilio by verifying
 * the X-Twilio-Signature header using HMAC-SHA1 per Twilio's spec.
 *
 * @see https://www.twilio.com/docs/usage/security#validating-requests
 */
import type { Context, Next } from "hono";
/**
 * Compute the expected Twilio signature for a request.
 *
 * Algorithm (per Twilio docs):
 * 1. Take the full URL of the request
 * 2. Sort POST body params alphabetically by key
 * 3. Append each key-value pair to the URL (no separators)
 * 4. HMAC-SHA1 the result with the auth token, then Base64 encode
 */
export declare function computeTwilioSignature(authToken: string, url: string, params: Record<string, string>): string;
/**
 * Validate a Twilio request signature
 */
export declare function validateTwilioSignature(authToken: string, signature: string, url: string, params: Record<string, string>): boolean;
/**
 * Options for {@link twilioSignatureMiddleware}.
 */
export interface TwilioSignatureOptions {
    /**
     * Accept requests when no auth token is configured, i.e. run with signature
     * validation switched off. Development and local testing only — with this on,
     * anyone who can reach the webhook can impersonate Twilio. Default: false.
     */
    allowUnsigned?: boolean;
}
/**
 * Build the URL Twilio used when it computed its signature.
 *
 * Twilio signs the full request URL *including* the query string, so a
 * webhook configured with query parameters (`/sms?tenant=acme`) only
 * validates when they are preserved here.
 */
export declare function signedRequestUrl(requestUrl: string, path: string, baseUrl?: string): string;
/**
 * Hono middleware factory for Twilio signature validation.
 *
 * Fails closed: without an auth token there is no way to tell a genuine Twilio
 * request from a forged one, so every request is rejected with 403 unless
 * `allowUnsigned` is explicitly set.
 */
export declare function twilioSignatureMiddleware(authToken?: string, baseUrl?: string, options?: TwilioSignatureOptions): (c: Context, next: Next) => Promise<void | (Response & import("hono").TypedResponse<"", 403, "text">)>;