/**
 * Simple username/password authentication.
 */
export interface Authenticator {
    /**
     * Authenticate username/password.
     * @param username Username.
     * @param password Password.
     * @return true if user exists with that password, false otherwise.
     */
    authenticate(username: string, password: string): boolean | Promise<boolean>;
}
/**
 * Basic username/password-based authentication manager.
 */
export declare class PlainAuthenticator implements Authenticator {
    static validateUsername(username: string): void;
    private _users;
    /**
     * Add/replace user, using given password.
     * Note that a username cannot start with an `@`, because that is reserved
     * for group names.
     * @param username Username of user to add or replace
     * @param password Password to use for this user
     */
    setUser(username: string, password: string): void;
    /**
     * Remove user, if it exists.
     */
    deleteUser(username: string): void;
    authenticate(username: string, password: string): boolean;
}