CSRF 跨域

Question

我的 REST API 后端目前使用基于 cookie 的 CSRF 保护。

基本过程是后端设置一个可由客户端应用程序读取的 cookie，然后在随后的 HXR 请求（我的 CORS 设置允许的）上，一个自定义标头与 cookie 一起传递，服务器检查两个值匹配。

基本上，这一切都是通过 Spring Security 中的一行非常简单的 Java 代码实现的。

.csrf().csrfTokenRepository(new CookieCsrfTokenRepository())

当 UI 来自同一个域时，这非常有用，因为客户端中的 JS 可以轻松访问（非 http-only）cookie 以读取值并发送自定义标头。

当我希望我的客户端应用程序部署在不同的域上时，我的挑战就来了，例如

API: api.x.com
UI: ui.y.com

我解决这个问题的想法是

1. 可以将令牌与 cookie 一起发送回自定义响应标头中，而不是仅在 cookie 中发回。
2. 然后客户端读取自定义标头和本地消息（使用本地存储或可能通过在客户端动态创建 cookie，但这次是在 UI 域上，以便稍后读取）。
3. 随后，当客户端在自定义请求标头中发出 XHR 请求时，该值将被客户端使用，并且在步骤 1 中设置的 cookie 也将随之使用。
4. 服务器检查这两个值（cookie 和请求标头）是否已设置并且它们完全匹配。

这是一种众所周知/可接受的方法吗？任何人都可以从安全角度识别这种方法的任何明显缺陷吗？

显然，API 服务器需要允许 UI 域的 CORS + 允许凭据并在 CORS 策略中公开自定义响应标头。

编辑

我将尝试使用我编写的这个自定义存储库在 Spring Security 中实现这一点：

import org.springframework.security.web.csrf.CookieCsrfTokenRepository;
import org.springframework.security.web.csrf.CsrfToken;
import org.springframework.security.web.csrf.CsrfTokenRepository;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * This class is essentially a wrapper for a cookie based CSRF protection scheme.
 * <p>
 * The issue with the pure cookie based mechanism is that if you deploy the UI on a different domain to the API then the client is not able to read the cookie value when a new CSRF token is generated (even if the cookie is not HTTP only).
 * <p>
 * This mechanism essentially does the same thing, but also provides a response header so that the client can read this value and the use some local mechanism to store the token (session storage, local storage, local user agent DB, construct a new cookie on the UI domain etc).
 */
public class CrossDomainHeaderAndCookieCsrfTokenRepository implements CsrfTokenRepository {

    public static final String XSRF_HEADER_NAME = "X-XSRF-TOKEN";
    private static final String XSRF_TOKEN_COOKIE_NAME = "XSRF-TOKEN";
    private static final String CSRF_QUERY_PARAM_NAME = "_csrf";

    private final CookieCsrfTokenRepository delegate = new CookieCsrfTokenRepository();

    public CrossDomainHeaderAndCookieCsrfTokenRepository() {
        delegate.setCookieHttpOnly(true);
        delegate.setHeaderName(XSRF_HEADER_NAME);
        delegate.setCookieName(XSRF_TOKEN_COOKIE_NAME);
        delegate.setParameterName(CSRF_QUERY_PARAM_NAME);
    }

    @Override
    public CsrfToken generateToken(final HttpServletRequest request) {
        return delegate.generateToken(request);
    }

    @Override
    public void saveToken(final CsrfToken token, final HttpServletRequest request, final HttpServletResponse response) {
        delegate.saveToken(token, request, response);
        response.setHeader(token.getHeaderName(), token.getToken());
    }

    @Override
    public CsrfToken loadToken(final HttpServletRequest request) {
        return delegate.loadToken(request);
    }
}

Answer 1

大约 1 年以来，我一直在成功地使用类似于我在生产中的描述编辑中的类。班级是：

/**
 * This class is essentially a wrapper for a cookie based CSRF protection scheme.
 * The issue with the pure cookie based mechanism is that if you deploy the UI on a different domain to the API then
 * the client is not able to read the cookie value when a new CSRF token is generated (even if the cookie is not HTTP only).
 * This mechanism does the same thing, but also provides a response header so that the client can read this value and the use
 * some local mechanism to store the token (local storage, local user agent DB, construct a new cookie on the UI domain etc).
 *
 * @see <a href="https://stackoverflow.com/questions/45424496/csrf-cross-domain">https://stackoverflow.com/questions/45424496/csrf-cross-domain</a>
 */
public class CrossDomainCsrfTokenRepository implements CsrfTokenRepository {

    public static final String XSRF_HEADER_NAME = "X-XSRF-TOKEN";
    public static final String XSRF_TOKEN_COOKIE_NAME = "XSRF-TOKEN";
    private static final String CSRF_QUERY_PARAM_NAME = "_csrf";

    private final CookieCsrfTokenRepository delegate = new CookieCsrfTokenRepository();

    public CrossDomainCsrfTokenRepository() {
        delegate.setCookieHttpOnly(true);
        delegate.setHeaderName(XSRF_HEADER_NAME);
        delegate.setCookieName(XSRF_TOKEN_COOKIE_NAME);
        delegate.setParameterName(CSRF_QUERY_PARAM_NAME);
    }

    @Override
    public CsrfToken generateToken(final HttpServletRequest request) {
        return delegate.generateToken(request);
    }

    @Override
    public void saveToken(final CsrfToken token, final HttpServletRequest request, final HttpServletResponse response) {
        delegate.saveToken(token, request, response);
        response.setHeader(XSRF_HEADER_NAME, nullSafeTokenValue(token));
    }

    @Override
    public CsrfToken loadToken(final HttpServletRequest request) {
        return delegate.loadToken(request);
    }

    private String nullSafeTokenValue(final CsrfToken token) {
        return ofNullable(token)
            .map(CsrfToken::getToken)
            .orElse("");
    }
}

我通过 Spring Boot 安全配置启用它：

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private CsrfTokenRepository csrfTokenRepository;

    @Override
    @SuppressWarnings("PMD.SignatureDeclareThrowsException")
    protected void configure(final HttpSecurity http) throws Exception {
        http.csrf().ignoringAntMatchers(CTM_RESOURCE).csrfTokenRepository(csrfTokenRepository);
    }

}

请注意，我还为本文中显示的 WebSecurityConfig 类启用了 CORS 属性源 bean，以将相关的 XSRF 标头列入白名单：

@Bean
    public UrlBasedCorsConfigurationSource corsConfigurationSource() {
        final CorsConfiguration configuration = new CorsConfiguration();
        configuration.setAllowedOrigins(properties.getAllowedOrigins());
        configuration.setAllowedMethods(allHttpMethods());
        configuration.setAllowedHeaders(asList(CrossDomainCsrfTokenRepository.XSRF_HEADER_NAME, CONTENT_TYPE));
        configuration.setExposedHeaders(asList(LOCATION, CrossDomainCsrfTokenRepository.XSRF_HEADER_NAME));
        configuration.setAllowCredentials(true);
        configuration.setMaxAge(HOURS.toSeconds(properties.getMaxAgeInHours()));
        final UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", configuration);
        return source;
    }

Answer 2

我认为您可以为 CsrfTokenRepository 提供另一种实现，以支持 CSRF 令牌的不同域模式。

您可以通过对代码进行以下更改来克隆原始实现：

....

private String domain;
private Pattern domainPattern;

....

public void saveToken(CsrfToken token, HttpServletRequest request, HttpServletResponse response) {

    ....

    String domain = getDomain(request);
    if (domain != null) {
        cookie.setDomain(domain);
    }

    response.addCookie(cookie);
}

.....    

public void setDomainPattern(String domainPattern) {
    if (this.domain != null) {
        throw new IllegalStateException("Cannot set both domainName and domainNamePattern");
    }
    this.domainPattern = Pattern.compile(domainPattern, Pattern.CASE_INSENSITIVE);
}

public void setDomain(String domain) {
    if (this.domainPattern != null) {
        throw new IllegalStateException("Cannot set both domainName and domainNamePattern");
    }
    this.domain = domain;
}

private String getDomain(HttpServletRequest request) {
    if (this.domain != null) {
        return this.domain;
    }
    if (this.domainPattern != null) {
        Matcher matcher = this.domainPattern.matcher(request.getServerName());
        if (matcher.matches()) {
            return matcher.group(1);
        }
    }
    return null;
}

然后，提供您的新实现。

.csrf().csrfTokenRepository(new CustomCookieCsrfTokenRepository())