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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);
 	}
 
 }
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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 {
 
 	}
 
 }
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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 {
 
 }
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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;
 } 
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@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;
 	}
 }
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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));
 	}
 
 }
 
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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。

Spring Boot Security自动配置源码解析插图
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