/**
 * Loads PEM certificate bundles for custom gRPC trust configuration.
 *
 * Use {@link getSystemRootCAs} for environment-selected and common system PEM
 * files. Use {@link normalizeRootCAs} for application-provided PEM data or file
 * paths. These helpers do not access platform certificate stores or Node.js
 * built-in roots.
 *
 * @packageDocumentation
 */
import { Logger } from '../util/logging.js';
/**
 * Loads system root certificates from common paths.
 *
 * The function first reads every valid path in `NODE_EXTRA_CA_CERTS` and
 * `SSL_CERT_FILE`. It then reads the first common operating-system bundle that
 * exists. It joins all loaded PEM data in that order.
 *
 * This is a PEM-file scan. It does not read the Windows certificate store,
 * the macOS Keychain, or Node.js built-in root certificates.
 *
 * File errors do not stop SDK initialization. The function writes lookup
 * details to the supplied {@link Logger} and returns `undefined` when it cannot
 * read a non-empty bundle.
 *
 * @param logger Receives trace and debug details. The function does not log
 * certificate contents.
 * @returns Concatenated PEM data, or `undefined` when no bundle is available.
 */
export declare function getSystemRootCAs(logger: Logger): Buffer | undefined;
/**
 * Loads user-supplied root certificates.
 *
 * A `Buffer` contains the certificate data. A string contains a PEM file path.
 * An array contains PEM file paths in concatenation order. The function
 * returns the same `Buffer` instance when the input is a buffer.
 *
 * Missing, empty, and unreadable files are ignored. If no path produces data,
 * the function returns `undefined`; it does not throw.
 *
 * @example
 * ```ts
 * import { Buffer } from 'node:buffer';
 * import { normalizeRootCAs } from '@nebius/js-sdk/runtime/tls/system_certs';
 *
 * const pem = Buffer.from('application-provided PEM data');
 * const roots = normalizeRootCAs(pem);
 * roots === pem; // true
 * ```
 */
export declare function normalizeRootCAs(input?: Buffer | string | string[]): Buffer | undefined;
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