spring security中的csrf防御原理(跨域请求伪造)

什么是csrf？

csrf又称跨域请求伪造，攻击方通过伪造用户请求访问受信任站点。CSRF这种攻击方式在2000年已经被国外的安全人员提出，但在国内，直到06年才开始被关注，08年，国内外的多个大型社区和交互网站分别爆出CSRF漏洞，如：NYTimes.com（纽约时报）、Metafilter（一个大型的BLOG网站），YouTube和百度HI......而现在，互联网上的许多站点仍对此毫无防备，以至于安全业界称CSRF为“沉睡的巨人”。

举个例子，用户通过表单发送请求到银行网站，银行网站获取请求参数后对用户账户做出更改。在用户没有退出银行网站情况下，访问了攻击网站，攻击网站中有一段跨域访问的代码，可能自动触发也可能点击提交按钮，访问的url正是银行网站接受表单的url。因为都来自于用户的浏览器端，银行将请求看作是用户发起的，所以对请求进行了处理，造成的结果就是用户的银行账户被攻击网站修改。

解决方法基本上都是增加攻击网站无法获取到的一些表单信息，比如增加图片验证码，可以杜绝csrf攻击，但是除了登陆注册之外，其他的地方都不适合放验证码，因为降低了网站易用性

相关介绍：

http://baike.baidu.com/view/1609487.htm?fr=aladdin

spring-servlet中配置csrf

 <!-- Spring csrf 拦截器 -->
 <mvc:interceptors>
  <mvc:interceptor>
   <mvc:mapping path="/login" />
   <bean class="com.wangzhixuan.commons.csrf.CsrfInterceptor" />
  </mvc:interceptor>
 </mvc:interceptors>

在类中声明Csrf拦截器，用来生成或去除CsrfToken

import java.io.IOException;

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

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import com.wangzhixuan.commons.scan.ExceptionResolver;
import com.wangzhixuan.commons.utils.WebUtils;

/**
 * Csrf拦截器，用来生成或去除CsrfToken
 * 
 * @author L.cm
 */
public class CsrfInterceptor extends HandlerInterceptorAdapter {
 private static final Logger logger = LogManager.getLogger(ExceptionResolver.class);
 
 @Autowired 
 private CsrfTokenRepository csrfTokenRepository;
 
 @Override
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
  HandlerMethod handlerMethod = (HandlerMethod) handler;
  // 非控制器请求直接跳出
  if (!(handler instanceof HandlerMethod)) {
   return true;
  }
  CsrfToken csrfToken = handlerMethod.getMethodAnnotation(CsrfToken.class);
  // 判断是否含有@CsrfToken注解
  if (null == csrfToken) {
   return true;
  }
  // create、remove同时为true时异常
  if (csrfToken.create() && csrfToken.remove()) {
   logger.error("CsrfToken attr create and remove can Not at the same time to true!");
   return renderError(request, response, Boolean.FALSE, "CsrfToken attr create and remove can Not at the same time to true!");
  }
  // 创建
  if (csrfToken.create()) {
   CsrfTokenBean token = csrfTokenRepository.generateToken(request);
   csrfTokenRepository.saveToken(token, request, response);
   // 缓存一个表单页面地址的url
   csrfTokenRepository.cacheUrl(request, response);
   request.setAttribute(token.getParameterName(), token);
   return true;
  }
  // 判断是否ajax请求
  boolean isAjax = WebUtils.isAjax(handlerMethod);
  // 校验，并且清除
  CsrfTokenBean tokenBean = csrfTokenRepository.loadToken(request);
  if (tokenBean == null) {
   return renderError(request, response, isAjax, "CsrfToken is null!");
  }
  String actualToken = request.getHeader(tokenBean.getHeaderName());
  if (actualToken == null) {
   actualToken = request.getParameter(tokenBean.getParameterName());
  }
  if (!tokenBean.getToken().equals(actualToken)) {
   return renderError(request, response, isAjax, "CsrfToken not eq!");
  }
  return true;
 }
 
 private boolean renderError(HttpServletRequest request, HttpServletResponse response, 
   boolean isAjax, String message) throws IOException {
  // 获取缓存的cacheUrl
  String cachedUrl = csrfTokenRepository.getRemoveCacheUrl(request, response);
  // ajax请求直接抛出异常，因为{@link ExceptionResolver}会去处理
  if (isAjax) {
   throw new RuntimeException(message);
  }
  // 非ajax CsrfToken校验异常，先清理token
  csrfTokenRepository.saveToken(null, request, response);
  logger.info("Csrf[redirectUrl]:\t" + cachedUrl);
  response.sendRedirect(cachedUrl);
  return false;
 }

 /**
  * 用于清理@CsrfToken保证只能请求成功一次
  */
 @Override
 public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
   ModelAndView modelAndView) throws Exception {
  HandlerMethod handlerMethod = (HandlerMethod) handler;
  // 非控制器请求直接跳出
  if (!(handler instanceof HandlerMethod)) {
   return;
  }
  CsrfToken csrfToken = handlerMethod.getMethodAnnotation(CsrfToken.class);
  if (csrfToken == null || !csrfToken.remove()) {
   return;
  }
  csrfTokenRepository.getRemoveCacheUrl(request, response);
  csrfTokenRepository.saveToken(null, request, response);
 }

}

声明Csrf过滤注解，通过标注来过滤对应的请求

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Csrf过滤注解
 * @author L.cm
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface CsrfToken {
 boolean create() default false;
 boolean remove() default false;
}

建立实例对象（操作对象）

import java.io.Serializable;
import org.springframework.util.Assert;
public class CsrfTokenBean implements Serializable {
 private static final long serialVersionUID = -6865031901744243607L;
 private final String token;
 private final String parameterName;
 private final String headerName;
 /**
  * Creates a new instance
  * @param headerName the HTTP header name to use
  * @param parameterName the HTTP parameter name to use
  * @param token the value of the token (i.e. expected value of the HTTP parameter of
  * parametername).
  */
 public CsrfTokenBean(String headerName, String parameterName, String token) {
  Assert.hasLength(headerName, "headerName cannot be null or empty");
  Assert.hasLength(parameterName, "parameterName cannot be null or empty");
  Assert.hasLength(token, "token cannot be null or empty");
  this.headerName = headerName;
  this.parameterName = parameterName;
  this.token = token;
 }
 public String getHeaderName() {
  return this.headerName;
 }
 public String getParameterName() {
  return this.parameterName;
 }
 public String getToken() {
  return this.token;
 }
}

过滤过程中需要的仓库

package com.wangzhixuan.commons.csrf;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface CsrfTokenRepository {
 /**
  * Generates a {@link CsrfTokenBean}
  *
  * @param request the {@link HttpServletRequest} to use
  * @return the {@link CsrfTokenBean} that was generated. Cannot be null.
  */
 CsrfTokenBean generateToken(HttpServletRequest request);
 /**
  * Saves the {@link CsrfTokenBean} using the {@link HttpServletRequest} and
  * {@link HttpServletResponse}. If the {@link CsrfTokenBean} is null, it is the same as
  * deleting it.
  *
  * @param token the {@link CsrfTokenBean} to save or null to delete
  * @param request the {@link HttpServletRequest} to use
  * @param response the {@link HttpServletResponse} to use
  */
 void saveToken(CsrfTokenBean token, HttpServletRequest request,
   HttpServletResponse response);
 /**
  * Loads the expected {@link CsrfTokenBean} from the {@link HttpServletRequest}
  *
  * @param request the {@link HttpServletRequest} to use
  * @return the {@link CsrfTokenBean} or null if none exists
  */
 CsrfTokenBean loadToken(HttpServletRequest request);
 /**
  * 缓存来源的url
  * @param request request the {@link HttpServletRequest} to use
  * @param response the {@link HttpServletResponse} to use
  */
 void cacheUrl(HttpServletRequest request, HttpServletResponse response);
 /**
  * 获取并清理来源的url
  * @param request the {@link HttpServletRequest} to use
  * @param response the {@link HttpServletResponse} to use
  * @return 来源url
  */
 String getRemoveCacheUrl(HttpServletRequest request, HttpServletResponse response);
}

HttpSessionCsrfTokenRepository

package com.wangzhixuan.commons.csrf;
import java.util.UUID;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.wangzhixuan.commons.utils.StringUtils;
public final class HttpSessionCsrfTokenRepository implements CsrfTokenRepository {
 private static final String DEFAULT_CSRF_PARAMETER_NAME = "_csrf";
 private static final String DEFAULT_CSRF_HEADER_NAME = "X-CSRF-TOKEN";
 private static final String DEFAULT_CSRF_TOKEN_ATTR_NAME = HttpSessionCsrfTokenRepository.class
   .getName().concat(".CSRF_TOKEN");
 private static final String DEFAULT_CACHE_URL_ATTR_NAME = HttpSessionCsrfTokenRepository.class
   .getName().concat(".CACHE_URL");
 private String parameterName = DEFAULT_CSRF_PARAMETER_NAME;
 private String headerName = DEFAULT_CSRF_HEADER_NAME;
 private String sessionAttributeName = DEFAULT_CSRF_TOKEN_ATTR_NAME;
 private String cacheUrlAttributeName = DEFAULT_CACHE_URL_ATTR_NAME;
 /*
  * (non-Javadoc)
  *
  * @see org.springframework.security.web.csrf.CsrfTokenRepository#saveToken(org.
  * springframework .security.web.csrf.CsrfToken,
  * javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
  */
 public void saveToken(CsrfTokenBean token, HttpServletRequest request,
   HttpServletResponse response) {
  if (token == null) {
   HttpSession session = request.getSession(false);
   if (session != null) {
    session.removeAttribute(this.sessionAttributeName);
   }
  }
  else {
   HttpSession session = request.getSession();
   session.setAttribute(this.sessionAttributeName, token);
  }
 }
 /*
  * (non-Javadoc)
  *
  * @see
  * org.springframework.security.web.csrf.CsrfTokenRepository#loadToken(javax.servlet
  * .http.HttpServletRequest)
  */
 public CsrfTokenBean loadToken(HttpServletRequest request) {
  HttpSession session = request.getSession(false);
  if (session == null) {
   return null;
  }
  return (CsrfTokenBean) session.getAttribute(this.sessionAttributeName);
 }
 /*
  * (non-Javadoc)
  *
  * @see org.springframework.security.web.csrf.CsrfTokenRepository#generateToken(javax.
  * servlet .http.HttpServletRequest)
  */
 public CsrfTokenBean generateToken(HttpServletRequest request) {
  return new CsrfTokenBean(this.headerName, this.parameterName,
    createNewToken());
 }
 private String createNewToken() {
  return UUID.randomUUID().toString();
 }
 @Override
 public void cacheUrl(HttpServletRequest request, HttpServletResponse response) {
  String queryString = request.getQueryString();
  // 被拦截前的请求URL
  String redirectUrl = request.getRequestURI();
  if (StringUtils.isNotBlank(queryString)) {
   redirectUrl = redirectUrl.concat("?").concat(queryString);
  }
  HttpSession session = request.getSession();
  session.setAttribute(this.cacheUrlAttributeName, redirectUrl);
 }
 @Override
 public String getRemoveCacheUrl(HttpServletRequest request, HttpServletResponse response) {
  HttpSession session = request.getSession(false);
  if (session == null) {
   return null;
  }
  String redirectUrl = (String) session.getAttribute(this.cacheUrlAttributeName);
  if (StringUtils.isBlank(redirectUrl)) {
   return null;
  }
  session.removeAttribute(this.cacheUrlAttributeName);
  return redirectUrl;
 }
}

总结

以上所述是小编给大家介绍的spring security中的csrf防御原理(跨域请求伪造)，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对易盾网络网站的支持！
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