SpringGateway使用SpringSecurity防止CSRF攻击

@Bean
public SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
	http
		.csrf(csrf -> csrf.csrfTokenRepository(cookieServerCsrfTokenRepository.withHttponlyFalse()))
	return http.build();
}

以上通过cookie持久化XSRF-TOKEN值，jS读取cookie中的值发起请求时需携带X-XSRF-TOKEN
请求头，默认情况GET，HEAD，TRACE，OPTIONS请求方式是放行的，具体实现在DefaultRequireCsrfProtectionMatcher
类。如果需要特殊定制，可以自定义实现类实现ServerWebExchangeMatcher,并替换默认DefaultRequireCsrfProtectionMatcher:

  @Bean
    public SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
        http
                .csrf(csrf -> csrf.csrfTokenRepository(cookieServerCsrfTokenRepository.withHttponlyFalse())
                        .requireCsrfProtectionMatcher(new CustomServerWebExchangeMatcher());
        return http.build();
    }

在我们按照上述配置分别测试GET请求和POST请求时，发现GET请求响应cookie中并没有XSRF-TOKEN，原因在响应式编程中CsrfToken
并没有被订阅。具体问题解析在Spring Security issues中找到答案；
最后也提供了解决方式：

@Slf4j
@Component
public class CsrfHelperFilter implements WebFilter {

    @Override
    public Mono filter(ServerWebExchange exchange, WebFilterChain chain) {
        String key = CsrfToken.class.getName();
        Mono csrfToken = null != exchange.getAttribute(key) ? exchange.getAttribute(key) : Mono.empty();
        return csrfToken.doonSuccess(token -> {
            Responsecookie cookie = Responsecookie.from("XSRF-TOKEN", token.getToken()).maxAge(Duration.ofHours(1))
                    .httponly(false).path("/").build();
            log.debug("cookie: {}", cookie);
            exchange.getResponse().getcookies().add("XSRF-TOKEN", cookie);
        }).then(chain.filter(exchange));
    }
}