Spring Security笔记：解决CsrfFilter与Rest服务Post方式的矛盾

基于Spring Security+Spring MVC的web应用，为了防止跨站提交攻击，通常会配置csrf，即：

1     <http ...>
2         ...
3         <csrf />
4     </http>

如果应用中有Post方式访问的Rest服务(参考下面的代码)，会很不幸的发现，所有POST方式请求的服务会调用失败。

1     @RequestMapping(value = "/user/create", method = RequestMethod.POST)
2     @ResponseBody
3     public UserInfo createUser(@RequestBody(required = true) UserInfo user,
4             HttpServletRequest request, HttpServletResponse response)
5             throws Exception {
6         ...
7     }

原因在于：启用csrf后，所有http请求都被会CsrfFilter拦截，而CsrfFilter中有一个私有类DefaultRequiresCsrfMatcher

 1     private static final class DefaultRequiresCsrfMatcher implements RequestMatcher {
 2         private Pattern allowedMethods = Pattern.compile("^(GET|HEAD|TRACE|OPTIONS)$");
 3
 4         /* (non-Javadoc)
 5          * @see org.springframework.security.web.util.matcher.RequestMatcher#matches(javax.servlet.http.HttpServletRequest)
 6          */
 7         public boolean matches(HttpServletRequest request) {
 8             return !allowedMethods.matcher(request.getMethod()).matches();
 9         }
10     }

从这段源码可以发现，POST方法被排除在外了，也就是说只有GET|HEAD|TRACE|OPTIONS这4类方法会被放行，其它Method的http请求，都要验证_csrf的token是否正确，而通常post方式调用rest服务时，又没有_csrf的token，所以校验失败。

解决方法：自己弄一个Matcher

 1 package com.cnblogs.yjmyzz.utils;
 2
 3 import java.util.List;
 4 import java.util.regex.Pattern;
 5
 6 import javax.servlet.http.HttpServletRequest;
 7
 8 import org.springframework.security.web.util.matcher.RequestMatcher;
 9
10 public class CsrfSecurityRequestMatcher implements RequestMatcher {
11     private Pattern allowedMethods = Pattern
12             .compile("^(GET|HEAD|TRACE|OPTIONS)$");
13
14     public boolean matches(HttpServletRequest request) {
15
16         if (execludeUrls != null && execludeUrls.size() > 0) {
17             String servletPath = request.getServletPath();
18             for (String url : execludeUrls) {
19                 if (servletPath.contains(url)) {
20                     return false;
21                 }
22             }
23         }
24         return !allowedMethods.matcher(request.getMethod()).matches();
25     }
26
27     /**
28      * 需要排除的url列表
29      */
30     private List<String> execludeUrls;
31
32     public List<String> getExecludeUrls() {
33         return execludeUrls;
34     }
35
36     public void setExecludeUrls(List<String> execludeUrls) {
37         this.execludeUrls = execludeUrls;
38     }
39 }

这里添加了一个属性execludeUrls，允许人为排除哪些url。

然后在配置文件里，这样修改：

 1     <http entry-point-ref="loginEntryPoint" use-expressions="true">
 2         ...
 3         <intercept-url pattern="/rest/**" access="permitAll" />
 4         ...
 5         <csrf request-matcher-ref="csrfSecurityRequestMatcher"/>
 6     </http>
 7
 8     <beans:bean id="csrfSecurityRequestMatcher" class="com.cnblogs.yjmyzz.utils.CsrfSecurityRequestMatcher">
 9         <beans:property name="execludeUrls">
10             <beans:list>
11                 <beans:value>/rest/</beans:value>
12             </beans:list>
13         </beans:property>
14     </beans:bean>

这里约定所有/rest/开头的都是Rest服务地址，上面的配置就把/rest/排除在csrf验证的范围之外了.