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Spring Security 实战干货:Spring Boot 中的 Spring Security 自动配置初探

1. 前言

我们在前几篇对 Spring Security 的用户信息管理机制,密码机制进行了探讨。我们发现 Spring Security Starter相关的 Servlet 自动配置都在spring-boot-autoconfigure-2.1.9.RELEASE(当前 Spring Boot 版本为2.1.9.RELEASE) 模块的路径org.springframework.boot.autoconfigure.security.servlet 之下。其实官方提供的Starter组件的自动配置你都能在spring-boot-autoconfigure-2.1.9.RELEASE下找到。今天我们进一步来解密 Spring SecuritySpring Boot 的配置和使用。

2. Spring Boot 下 Spring Security 的自动配置

我们可以通过 org.springframework.boot.autoconfigure.security.servlet 路径下找到 Spring Security 关于Servlet的自动配置类。我们来大致了解一下。

2.1 SecurityAutoConfiguration

  package org.springframework.boot.autoconfigure.security.servlet;

  import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
  import org.springframework.boot.autoconfigure.security.SecurityDataConfiguration;
  import org.springframework.boot.autoconfigure.security.SecurityProperties;
  import org.springframework.boot.context.properties.EnableConfigurationProperties;
  import org.springframework.context.ApplicationEventPublisher;
  import org.springframework.context.annotation.Bean;
  import org.springframework.context.annotation.Configuration;
  import org.springframework.context.annotation.Import;
  import org.springframework.security.authentication.AuthenticationEventPublisher;
  import org.springframework.security.authentication.DefaultAuthenticationEventPublisher;

  /**
   * {@link EnableAutoConfiguration Auto-configuration} for Spring Security.
   *
   * @author Dave Syer
   * @author Andy Wilkinson
   * @author Madhura Bhave
   * @since 1.0.0
   */
  @Configuration
  @ConditionalOnClass(DefaultAuthenticationEventPublisher.class)
  @EnableConfigurationProperties(SecurityProperties.class)
  @Import({ SpringBootWebSecurityConfiguration.class, WebSecurityEnablerConfiguration.class,
          SecurityDataConfiguration.class })
  public class SecurityAutoConfiguration {

      @Bean
      @ConditionalOnMissingBean(AuthenticationEventPublisher.class)
      public DefaultAuthenticationEventPublisher authenticationEventPublisher(ApplicationEventPublisher publisher) {
          return new DefaultAuthenticationEventPublisher(publisher);
      }

  }

SecurityAutoConfiguration 顾名思义安全配置类。该类引入(@import)了 SpringBootWebSecurityConfigurationWebSecurityEnablerConfigurationSecurityDataConfiguration 三个配置类。 让这三个模块的类生效。是一个复合配置,是 Spring Security 自动配置最重要的一个类之一。 Spring Boot 自动配置经常使用这种方式以达到灵活配置的目的,这也是我们研究 Spring Security 自动配置的一个重要入口 同时 SecurityAutoConfiguration 还将 DefaultAuthenticationEventPublisher 作为默认的 AuthenticationEventPublisher 注入 Spring IoC 容器。如果你熟悉 Spring 中的事件机制你就会知道该类是一个 Spring 事件发布器。该类内置了一个HashMap<String, Constructor<? extends AbstractAuthenticationEvent>>维护了认证异常处理和对应异常事件处理逻辑的映射关系,比如账户过期异常 AccountExpiredException 对应认证过期事件AuthenticationFailureExpiredEvent ,也就是说发生不同认证的异常使用不同处理策略。

2.2 SpringBootWebSecurityConfiguration

  @Configuration
  @ConditionalOnClass(WebSecurityConfigurerAdapter.class)
  @ConditionalOnMissingBean(WebSecurityConfigurerAdapter.class)
  @ConditionalOnWebApplication(type = Type.SERVLET)
  public class SpringBootWebSecurityConfiguration {

      @Configuration
      @Order(SecurityProperties.BASIC_AUTH_ORDER)
      static class DefaultConfigurerAdapter extends WebSecurityConfigurerAdapter {

      }

  }

这个类是Spring Security 对 Spring Boot Servlet Web 应用的默认配置。核心在于WebSecurityConfigurerAdapter 适配器。从 @ConditionalOnMissingBean(WebSecurityConfigurerAdapter.class) 我们就能看出 WebSecurityConfigurerAdapter 是安全配置的核心。 默认情况下 DefaultConfigurerAdapter 将以SecurityProperties.BASIC_AUTH_ORDER-5) 的顺序注入 Spring IoC 容器,这是个空实现。如果我们需要个性化可以通过继承 WebSecurityConfigurerAdapter 来实现。我们会在以后的博文重点介绍该类。

2.3 WebSecurityEnablerConfiguration

  @Configuration
  @ConditionalOnBean(WebSecurityConfigurerAdapter.class)
  @ConditionalOnMissingBean(name = BeanIds.SPRING_SECURITY_FILTER_CHAIN)
  @ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.SERVLET)
  @EnableWebSecurity
  public class WebSecurityEnablerConfiguration {

  }

该配置类会在SpringBootWebSecurityConfiguration 注入 Spring IoC 容器后启用 @EnableWebSecurity 注解。也就是说 WebSecurityEnablerConfiguration 目的仅仅就是在某些条件下激活 @EnableWebSecurity 注解。那么这个注解都有什么呢?

3. @EnableWebSecurity 注解

  @Retention(value = java.lang.annotation.RetentionPolicy.RUNTIME)
  @Target(value = { java.lang.annotation.ElementType.TYPE })
  @Documented
  @Import({ WebSecurityConfiguration.class,
          SpringWebMvcImportSelector.class,
          OAuth2ImportSelector.class })
  @EnableGlobalAuthentication
  @Configuration
  public @interface EnableWebSecurity {

      /**
       * Controls debugging support for Spring Security. Default is false.
       * @return if true, enables debug support with Spring Security
       */
      boolean debug() default false;
  } 

@Enable* 这类注解都是带配置导入的注解。通过导入一些配置来启用一些特定功能。 @EnableWebSecurity 导入了 WebSecurityConfigurationSpringWebMvcImportSelectorOAuth2ImportSelector 以及启用了 @EnableGlobalAuthentication注解。

3.1 WebSecurityConfiguration

该配置类WebSecurityConfiguration使用一个WebSecurity对象基于用户指定的或者默认的安全配置,你可以通过继承 WebSecurityConfigurerAdapter 或者实现 WebSecurityConfigurer 来定制 WebSecurity 创建一个FilterChainProxy Bean来对用户请求进行安全过滤。这个FilterChainProxy的名称就是 WebSecurityEnablerConfiguration上的 BeanIds.SPRING_SECURITY_FILTER_CHAIN 也就是 springSecurityFilterChain,它是一个Filter,最终会被作为Servlet过滤器链中的一个Filter应用到Servlet容器中。安全处理的策略主要是过滤器的调用顺序。WebSecurityConfiguration 最终会通过 @EnableWebSecurity 应用到系统。

源码分析:

  package org.springframework.security.config.annotation.web.configuration;

  import java.util.Collections;
  import java.util.List;
  import java.util.Map;

  import javax.servlet.Filter;

  import org.springframework.beans.factory.BeanClassLoaderAware;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
  import org.springframework.context.annotation.Bean;
  import org.springframework.context.annotation.Configuration;
  import org.springframework.context.annotation.DependsOn;
  import org.springframework.context.annotation.ImportAware;
  import org.springframework.core.OrderComparator;
  import org.springframework.core.Ordered;
  import org.springframework.core.annotation.AnnotationAttributes;
  import org.springframework.core.annotation.AnnotationUtils;
  import org.springframework.core.annotation.Order;
  import org.springframework.core.type.AnnotationMetadata;
  import org.springframework.security.access.expression.SecurityExpressionHandler;
  import org.springframework.security.config.annotation.ObjectPostProcessor;
  import org.springframework.security.config.annotation.SecurityConfigurer;
  import org.springframework.security.config.annotation.web.WebSecurityConfigurer;
  import org.springframework.security.config.annotation.web.builders.WebSecurity;
  import org.springframework.security.context.DelegatingApplicationListener;
  import org.springframework.security.web.FilterChainProxy;
  import org.springframework.security.web.FilterInvocation;
  import org.springframework.security.web.access.WebInvocationPrivilegeEvaluator;
  import org.springframework.security.web.context.AbstractSecurityWebApplicationInitializer;


  /**
   * Spring Web Security 的配置类 : 
   *  1. 使用一个 WebSecurity 对象基于安全配置创建一个 FilterChainProxy 对象来对用户请求进行安全过滤。 
   *  2. 也会暴露诸如 安全SpEL表达式处理器 SecurityExpressionHandler 等一些类。
   *   
   * @see EnableWebSecurity
   * @see WebSecurity
   *
   * @author Rob Winch
   * @author Keesun Baik
   * @since 3.2
   */
  @Configuration
  public class WebSecurityConfiguration implements ImportAware, BeanClassLoaderAware {
      private WebSecurity webSecurity;
   // 是否启用了调试模式,来自注解 @EnableWebSecurity 的属性 debug,缺省值 false
      private Boolean debugEnabled;

      private List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers;

      private ClassLoader beanClassLoader;

      @Autowired(required = false)
      private ObjectPostProcessor<Object> objectObjectPostProcessor;
    /**
     *
     * 代理监听器 应该时监听 DefaultAuthenticationEventPublisher 的一些处理策略
     */   
      @Bean
      public static DelegatingApplicationListener delegatingApplicationListener() {
          return new DelegatingApplicationListener();
      }
     /**
      *
      * 安全SpEL表达式处理器 SecurityExpressionHandler 缺省为一个 DefaultWebSecurityExpressionHandler
      */   
      @Bean
      @DependsOn(AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
      public SecurityExpressionHandler<FilterInvocation> webSecurityExpressionHandler() {
          return webSecurity.getExpressionHandler();
      }

      /**
       *  Spring Security 核心过滤器  Spring Security Filter Chain  , Bean ID 为 springSecurityFilterChain
       * @return the {@link Filter} that represents the security filter chain
       * @throws Exception
       */
      @Bean(name = AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
      public Filter springSecurityFilterChain() throws Exception {
          boolean hasConfigurers = webSecurityConfigurers != null
                  && !webSecurityConfigurers.isEmpty();
          if (!hasConfigurers) {
              WebSecurityConfigurerAdapter adapter = objectObjectPostProcessor
                      .postProcess(new WebSecurityConfigurerAdapter() {
                      });
              webSecurity.apply(adapter);
          }
          return webSecurity.build();
      }

      /**
     *
     * 用于模板 如JSP Freemarker 的一些页面标签按钮控制支持
       * Creates the {@link WebInvocationPrivilegeEvaluator} that is necessary for the JSP
       * tag support.
       * @return the {@link WebInvocationPrivilegeEvaluator}
       * @throws Exception
       */
      @Bean
      @DependsOn(AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
      public WebInvocationPrivilegeEvaluator privilegeEvaluator() throws Exception {
          return webSecurity.getPrivilegeEvaluator();
      }

      /**
     *
     * 用于创建web configuration的SecurityConfigurer实例,
     * 注意该参数通过@Value(...)方式注入,对应的bean autowiredWebSecurityConfigurersIgnoreParents
     * 也在该类中定义
     *
       * @param objectPostProcessor the {@link ObjectPostProcessor} used to create a
       * {@link WebSecurity} instance
       * @param webSecurityConfigurers the
       * {@code <SecurityConfigurer<FilterChainProxy, WebSecurityBuilder>} instances used to
       * create the web configuration
       * @throws Exception
       */
      @Autowired(required = false)
      public void setFilterChainProxySecurityConfigurer(
              ObjectPostProcessor<Object> objectPostProcessor,
              @Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers)
              throws Exception {
          webSecurity = objectPostProcessor
                  .postProcess(new WebSecurity(objectPostProcessor));
          if (debugEnabled != null) {
              webSecurity.debug(debugEnabled);
          }

          Collections.sort(webSecurityConfigurers, AnnotationAwareOrderComparator.INSTANCE);

          Integer previousOrder = null;
          Object previousConfig = null;
          for (SecurityConfigurer<Filter, WebSecurity> config : webSecurityConfigurers) {
              Integer order = AnnotationAwareOrderComparator.lookupOrder(config);
              if (previousOrder != null && previousOrder.equals(order)) {
                  throw new IllegalStateException(
                          "@Order on WebSecurityConfigurers must be unique. Order of "
                                  + order + " was already used on " + previousConfig + ", so it cannot be used on "
                                  + config + " too.");
              }
              previousOrder = order;
              previousConfig = config;
          }
          for (SecurityConfigurer<Filter, WebSecurity> webSecurityConfigurer : webSecurityConfigurers) {
              webSecurity.apply(webSecurityConfigurer);
          }
          this.webSecurityConfigurers = webSecurityConfigurers;
      }
     /**
      * 从当前bean容器中获取所有的WebSecurityConfigurer bean。
      * 这些WebSecurityConfigurer通常是由开发人员实现的配置类,并且继承自WebSecurityConfigurerAdapter
      *  
      */   
      @Bean
      public static AutowiredWebSecurityConfigurersIgnoreParents autowiredWebSecurityConfigurersIgnoreParents(
              ConfigurableListableBeanFactory beanFactory) {
          return new AutowiredWebSecurityConfigurersIgnoreParents(beanFactory);
      }

      /**
       * A custom verision of the Spring provided AnnotationAwareOrderComparator that uses
       * {@link AnnotationUtils#findAnnotation(Class, Class)} to look on super class
       * instances for the {@link Order} annotation.
       *
       * @author Rob Winch
       * @since 3.2
       */
      private static class AnnotationAwareOrderComparator extends OrderComparator {
          private static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator();

          @Override
          protected int getOrder(Object obj) {
              return lookupOrder(obj);
          }

          private static int lookupOrder(Object obj) {
              if (obj instanceof Ordered) {
                  return ((Ordered) obj).getOrder();
              }
              if (obj != null) {
                  Class<?> clazz = (obj instanceof Class ? (Class<?>) obj : obj.getClass());
                  Order order = AnnotationUtils.findAnnotation(clazz, Order.class);
                  if (order != null) {
                      return order.value();
                  }
              }
              return Ordered.LOWEST_PRECEDENCE;
          }
      }

      /*
       * 要是为了获取注解 @EnableWebSecurity 的属性 debugEnabled
       *
       * @see org.springframework.context.annotation.ImportAware#setImportMetadata(org.
       * springframework.core.type.AnnotationMetadata)
       */
      public void setImportMetadata(AnnotationMetadata importMetadata) {
          Map<String, Object> enableWebSecurityAttrMap = importMetadata
                  .getAnnotationAttributes(EnableWebSecurity.class.getName());
          AnnotationAttributes enableWebSecurityAttrs = AnnotationAttributes
                  .fromMap(enableWebSecurityAttrMap);
          debugEnabled = enableWebSecurityAttrs.getBoolean("debug");
          if (webSecurity != null) {
              webSecurity.debug(debugEnabled);
          }
      }

      /*
       * (non-Javadoc)
       *
       * @see
       * org.springframework.beans.factory.BeanClassLoaderAware#setBeanClassLoader(java.
       * lang.ClassLoader)
       */
      public void setBeanClassLoader(ClassLoader classLoader) {
          this.beanClassLoader = classLoader;
      }
  }

3.2 SpringWebMvcImportSelector

该类是为了对 Spring Mvc 进行支持的。一旦发现应用使用 Spring Mvc 的核心前置控制器 DispatcherServlet 就会引入 WebMvcSecurityConfiguration 。主要是为了适配 Spring Mvc 。

3.3 OAuth2ImportSelector

该类是为了对 OAuth2.0 开放授权协议进行支持。ClientRegistration 如果被引用,具体点也就是 spring-security-oauth2 模块被启用(引入依赖jar)时。会启用 OAuth2 客户端配置 OAuth2ClientConfiguration

3.4 @EnableGlobalAuthentication

这个类主要引入了 AuthenticationConfiguration 目的主要为了构造 认证管理器 AuthenticationManagerAuthenticationManager 十分重要后面我们会进行专门的分析。

4. SecurityFilterAutoConfiguration

我们在 org.springframework.boot.autoconfigure.security.servlet 路径下还发现了一个配置类 SecurityFilterAutoConfiguration 。该类用于向Servlet容器注册一个名称为securityFilterChainRegistration的bean, 实现类是DelegatingFilterProxyRegistrationBean。该 bean 的目的是注册另外一个 Servlet Filter BeanServlet 容器,实现类为 DelegatingFilterProxyDelegatingFilterProxy 其实是一个代理过滤器,它被 Servlet 容器用于处理请求时,会将任务委托给指定给自己另外一个Filter bean。对于 SecurityFilterAutoConfiguration,来讲,这个被代理的Filter bean的名字为 springSecurityFilterChain , 也就是我们上面提到过的 Spring Security Web提供的用于请求安全处理的Filter bean,其实现类是 FilterChainProxy

相关的源码分析:

  package org.springframework.boot.autoconfigure.security.servlet;

  import java.util.EnumSet;
  import java.util.stream.Collectors;

  import javax.servlet.DispatcherType;

  import org.springframework.boot.autoconfigure.AutoConfigureAfter;
  import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
  import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
  import org.springframework.boot.autoconfigure.security.SecurityProperties;
  import org.springframework.boot.context.properties.EnableConfigurationProperties;
  import org.springframework.boot.web.servlet.DelegatingFilterProxyRegistrationBean;
  import org.springframework.context.annotation.Bean;
  import org.springframework.context.annotation.Configuration;
  import org.springframework.security.config.annotation.web.configuration.WebSecurityConfiguration;
  import org.springframework.security.config.http.SessionCreationPolicy;
  import org.springframework.security.web.context.AbstractSecurityWebApplicationInitializer;

  @Configuration
  // 仅在 Servlet 环境下生效
  @ConditionalOnWebApplication(type = Type.SERVLET)
  // 确保安全属性配置信息被加载并以bean形式被注册到容器
  @EnableConfigurationProperties(SecurityProperties.class)
  // 仅在特定类存在于 classpath 上时才生效
  @ConditionalOnClass({ AbstractSecurityWebApplicationInitializer.class,
          SessionCreationPolicy.class })
  // 指定该配置类在  SecurityAutoConfiguration 配置类应用之后应用       
  @AutoConfigureAfter(SecurityAutoConfiguration.class)
  public class SecurityFilterAutoConfiguration {

      // 要注册到 Servlet 容器的 DelegatingFilterProxy Filter的 
      // 目标代理Filter bean的名称 :springSecurityFilterChain
      private static final String DEFAULT_FILTER_NAME = 
              AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME;


      // 定义一个 bean securityFilterChainRegistration, 
      // 该 bean 的目的是注册另外一个 bean 到 Servlet 容器 : 实现类为 DelegatingFilterProxy 的一个 Servlet Filter
      // 该 DelegatingFilterProxy Filter 其实是一个代理过滤器,它被 Servlet 容器用于匹配特定URL模式的请求,
      // 而它会将任务委托给指定给自己的名字为 springSecurityFilterChain 的 Filter, 也就是 Spring Security Web
      // 提供的用于请求安全处理的一个 Filter bean,其实现类是 FilterChainProxy
      // (可以将 1 个 FilterChainProxy 理解为 1 HttpFirewall + n SecurityFilterChain)
      @Bean
      @ConditionalOnBean(name = DEFAULT_FILTER_NAME)
      public DelegatingFilterProxyRegistrationBean securityFilterChainRegistration(
              SecurityProperties securityProperties) {
          DelegatingFilterProxyRegistrationBean registration = new DelegatingFilterProxyRegistrationBean(
                  DEFAULT_FILTER_NAME);
          registration.setOrder(securityProperties.getFilter().getOrder());
          registration.setDispatcherTypes(getDispatcherTypes(securityProperties));
          return registration;
      }

      private EnumSet<DispatcherType> getDispatcherTypes(
              SecurityProperties securityProperties) {
          if (securityProperties.getFilter().getDispatcherTypes() == null) {
              return null;
          }
          return securityProperties.getFilter().getDispatcherTypes().stream()
                  .map((type) -> DispatcherType.valueOf(type.name())).collect(Collectors
                          .collectingAndThen(Collectors.toSet(), EnumSet::copyOf));
      }

  }

5. 总结

本文主要对 Spring Security 在 Spring Boot 中的自动配置一些机制进行了粗略的讲解。为什么没有细讲。因为从学习出发有些东西不是我们必须要深入了解的,但是又要知道一点点相关的知识。我们先宏观上有个大致的了解就行。所以在阅读本文一定不要钻牛角尖。粗略知道配置策略、加载策略和一些关键类的作用即可。在你对 Spring Security 有了进一步学习之后,回头认真来看这些配置类会有更深层的思考。 从另一个方面该文也给你阅读 Spring 源码提供了一些思路,学会这些才是最重要的。

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