SpringSecurity源码整体解析

核心思想

spring对请求的处理过程如下：

image.png

而security所有认证逻辑作为特殊的一个Filter加入到spring处理servelet的过滤链中，即FilterChainProxy；
而这个FilterChainProxy内部又有多个过滤器链FilterChain，每个链有matcher，用于匹配请求，请求来时选择最先匹配的一条过滤器链做权限认证，每条过滤器链又由多个多滤器Filter依序连接而成。如下图：

image.png

编程范式

configuator配置类装配到builder类中，builder类借助confuguator类构造filter或者filterChain
SpringSecurity有两个重要的builder：

WebSecurity：构造FilterChainProxy（由多条过滤器链SecurityFilterChain组成的代理）
HttpSecurity：构造过滤器链SecurityFilterChain（DefaultSecurityFilterChain）

Spring如何加载FilterChainProxy

首先生成FilterChainProxy实例，将FilterChainProxy实例再封装到DelegatingFilterProxy（java web的标准过滤器），作为一个web的Filter再注册到spring上下文。

生成FilterChainProxy实例

通过SpringBootApplication注解加载EnableAutoConfiguration注解

@SpringBootApplication
public class AuthCodeServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(AuthCodeServerApplication.class, args);
    }
}

public @interface SpringBootApplication {
    @AliasFor(
        annotation = EnableAutoConfiguration.class,
        attribute = "exclude"
    )
......

自动加载SecurityAutoConfiguation配置类
在spring.factories文件中有

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
......
org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\
......

加载SpringBootWebSecurityConfiguration配置类

@Import({SpringBootWebSecurityConfiguration.class, AuthenticationManagerConfiguration.class, BootGlobalAuthenticationConfiguration.class, SecurityDataConfiguration.class})
public class SecurityAutoConfiguration {
......

加载EnableWebSecurity注解

@Configuration
@EnableConfigurationProperties
@ConditionalOnClass({EnableWebSecurity.class, AuthenticationEntryPoint.class})
@ConditionalOnMissingBean({WebSecurityConfiguration.class})
@ConditionalOnWebApplication
@EnableWebSecurity
public class SpringBootWebSecurityConfiguration {
......

加载WebSecurityConfiguation配置类

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({WebSecurityConfiguration.class, SpringWebMvcImportSelector.class})
@EnableGlobalAuthentication
@Configuration
public @interface EnableWebSecurity {
    boolean debug() default false;
}

通过WebSecurityConfiguation配置类的springSecurityFilterChain方法产生FilterChainProxy 实例（实例名为springSecurityFilterChain）

@Configuration
public class WebSecurityConfiguration implements ImportAware, BeanClassLoaderAware {
    private WebSecurity webSecurity;
    private Boolean debugEnabled;
    private List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers;
    private ClassLoader beanClassLoader;
......
    @Bean(
        name = {"springSecurityFilterChain"}
    )
    public Filter springSecurityFilterChain() throws Exception {
        boolean hasConfigurers = this.webSecurityConfigurers != null && !this.webSecurityConfigurers.isEmpty();
        if (!hasConfigurers) {
            WebSecurityConfigurerAdapter adapter = (WebSecurityConfigurerAdapter)this.objectObjectPostProcessor.postProcess(new WebSecurityConfigurerAdapter() {
            });
            this.webSecurity.apply(adapter);
        }

        return (Filter)this.webSecurity.build();
    }

至于this.webSecurity.build()内部怎么实现的，后面再讲。

将FilterChainProxy实例注册到spring

将FilterChainProxy再封装到DelegatingFilterProxy，在注入到spring上下文。有两种方式，如下：

通过SecurityFilterAutoConfiguration配置类

    @Bean
    @ConditionalOnBean(
        name = {"springSecurityFilterChain"}
    )
    public DelegatingFilterProxyRegistrationBean securityFilterChainRegistration(SecurityProperties securityProperties) {
        DelegatingFilterProxyRegistrationBean registration = new DelegatingFilterProxyRegistrationBean("springSecurityFilterChain", new ServletRegistrationBean[0]);
        registration.setOrder(securityProperties.getFilterOrder());
        registration.setDispatcherTypes(this.getDispatcherTypes(securityProperties));
        return registration;
    }

通过继承实现AbstractSecurityWebApplicationInitializer抽象类
在onStartUp方法里调用insertSpringSecurityFilterChain方法注入

    public final void onStartup(ServletContext servletContext) throws ServletException {
        this.beforeSpringSecurityFilterChain(servletContext);
        if (this.configurationClasses != null) {
            AnnotationConfigWebApplicationContext rootAppContext = new AnnotationConfigWebApplicationContext();
            rootAppContext.register(this.configurationClasses);
            servletContext.addListener(new ContextLoaderListener(rootAppContext));
        }

        if (this.enableHttpSessionEventPublisher()) {
            servletContext.addListener("org.springframework.security.web.session.HttpSessionEventPublisher");
        }

        servletContext.setSessionTrackingModes(this.getSessionTrackingModes());
        this.insertSpringSecurityFilterChain(servletContext);
        this.afterSpringSecurityFilterChain(servletContext);
    }
......
    private void insertSpringSecurityFilterChain(ServletContext servletContext) {
        String filterName = "springSecurityFilterChain";
        DelegatingFilterProxy springSecurityFilterChain = new DelegatingFilterProxy(filterName);
        String contextAttribute = this.getWebApplicationContextAttribute();
        if (contextAttribute != null) {
            springSecurityFilterChain.setContextAttribute(contextAttribute);
        }

        this.registerFilter(servletContext, true, filterName, springSecurityFilterChain);
    }

详解FilterChainProxy实例如何产生

上面讲到了通过调用this.webSecurity.build()方法产生FilterChainProxy实例，现在仔细分析具体怎么实现的。

实例化并配置WebSecurity
在WebSecurityConfiguration配置类，通过setFilterChainProxySecurityConfigurer方法实例化WebSecurity，并搜索实现了WebSecurityConfigurer（WebSecurityConfigurerAdapter）的所有配置类，加载到WebSecurity中

    @Autowired(
        required = false
    )
    public void setFilterChainProxySecurityConfigurer(ObjectPostProcessor<Object> objectPostProcessor, @Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers) throws Exception {
        this.webSecurity = (WebSecurity)objectPostProcessor.postProcess(new WebSecurity(objectPostProcessor));
        if (this.debugEnabled != null) {
            this.webSecurity.debug(this.debugEnabled);
        }

        Collections.sort(webSecurityConfigurers, WebSecurityConfiguration.AnnotationAwareOrderComparator.INSTANCE);
        Integer previousOrder = null;
        Object previousConfig = null;

        Iterator var5;
        SecurityConfigurer config;
        for(var5 = webSecurityConfigurers.iterator(); var5.hasNext(); previousConfig = config) {
            config = (SecurityConfigurer)var5.next();
            Integer order = WebSecurityConfiguration.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;
        }

        var5 = webSecurityConfigurers.iterator();

        while(var5.hasNext()) {
            config = (SecurityConfigurer)var5.next();
            this.webSecurity.apply(config);
        }

        this.webSecurityConfigurers = webSecurityConfigurers;
    }

调用WebSucurity 的build方法构造FilterChainProxy实例
见上面第5步
最终会调到doBuild方法。

    protected final O doBuild() throws Exception {
        synchronized(this.configurers) {
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.INITIALIZING;
            this.beforeInit();
            this.init();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.CONFIGURING;
            this.beforeConfigure();
            this.configure();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.BUILDING;
            O result = this.performBuild();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.BUILT;
            return result;
        }
    }

由上可见，主要是init、configure、performBuild三个方法
2.1. init（WebSecurity）
会遍历所有之前加载好的配置类configuator（adaptor），调用其init。

    private void init() throws Exception {
        Collection<SecurityConfigurer<O, B>> configurers = this.getConfigurers();
        Iterator var2 = configurers.iterator();

        SecurityConfigurer configurer;
        while(var2.hasNext()) {
            configurer = (SecurityConfigurer)var2.next();
            configurer.init(this);
        }

        var2 = this.configurersAddedInInitializing.iterator();

        while(var2.hasNext()) {
            configurer = (SecurityConfigurer)var2.next();
            configurer.init(this);
        }

    }

其中配置类的init方法，主要是构造了HttpSecurity，放入到securityFilterChainBuilders；并在postBuild之后设置inteceptor到websecurity。可见WebSecurityConfigurerAdapter类的init方法实现：

    public void init(final WebSecurity web) throws Exception {
        final HttpSecurity http = this.getHttp();
        web.addSecurityFilterChainBuilder(http).postBuildAction(new Runnable() {
            public void run() {
                FilterSecurityInterceptor securityInterceptor = (FilterSecurityInterceptor)http.getSharedObject(FilterSecurityInterceptor.class);
                web.securityInterceptor(securityInterceptor);
            }
        });
    }

2.2. configure（WebSecurity）
会遍历所有之前加载好的配置类configuator（adaptor），调用其configure

    private void configure() throws Exception {
        Collection<SecurityConfigurer<O, B>> configurers = this.getConfigurers();
        Iterator var2 = configurers.iterator();

        while(var2.hasNext()) {
            SecurityConfigurer<O, B> configurer = (SecurityConfigurer)var2.next();
            configurer.configure(this);
        }
    }

配置类的configure方法，主要是配置上一步构造好的HttpSecurity实例，将其相关的configuator配置类装配到HttpSecurity实例。可见WebSecurityConfigurerAdapter类的configure方法实现：

    protected void configure(HttpSecurity http) throws Exception {
        this.logger.debug("Using default configure(HttpSecurity). If subclassed this will potentially override subclass configure(HttpSecurity).");
        ((HttpSecurity)((HttpSecurity)((AuthorizedUrl)http.authorizeRequests().anyRequest()).authenticated().and()).formLogin().and()).httpBasic();
    }

我们在定义自己的过滤器链的时候，可以继承WebSecurityConfigurerAdapter重写configure方法，比如：

protected void configure(HttpSecurity http) throws Exception {        
  http.requestMatchers() // 指定当前`SecurityFilterChain`实例匹配哪些请求                
    .anyRequest().and()            
    .authorizeRequests() // 拦截请求，创建FilterSecurityInterceptor                
    .anyRequest().authenticated() // 在创建过滤器的基础上的一些自定义配置                
    .and() // 用and来表示配置过滤器结束，以便进行下一个过滤器的创建和配置            
    .formLogin().and() // 设置表单登录，创建UsernamePasswordAuthenticationFilter            
    .httpBasic(); // basic验证，创建BasicAuthenticationFilter
}

2.3. performBuild（WebSecurity）
遍历securityFilterChainBuilders（其实就是HttpSecurity）列表调用其build方法，生成SecurityFilterChain实例，最后利用多个SecurityFilterChain实例组成List，再封装到FilterChainProxy。

    protected Filter performBuild() throws Exception {
        Assert.state(!this.securityFilterChainBuilders.isEmpty(), "At least one SecurityBuilder<? extends SecurityFilterChain> needs to be specified. Typically this done by adding a @Configuration that extends WebSecurityConfigurerAdapter. More advanced users can invoke " + WebSecurity.class.getSimpleName() + ".addSecurityFilterChainBuilder directly");
        int chainSize = this.ignoredRequests.size() + this.securityFilterChainBuilders.size();
        List<SecurityFilterChain> securityFilterChains = new ArrayList(chainSize);
        Iterator var3 = this.ignoredRequests.iterator();

        while(var3.hasNext()) {
            RequestMatcher ignoredRequest = (RequestMatcher)var3.next();
            securityFilterChains.add(new DefaultSecurityFilterChain(ignoredRequest, new Filter[0]));
        }

        var3 = this.securityFilterChainBuilders.iterator();

        while(var3.hasNext()) {
            SecurityBuilder<? extends SecurityFilterChain> securityFilterChainBuilder = (SecurityBuilder)var3.next();
            securityFilterChains.add(securityFilterChainBuilder.build());
        }

        FilterChainProxy filterChainProxy = new FilterChainProxy(securityFilterChains);
        if (this.httpFirewall != null) {
            filterChainProxy.setFirewall(this.httpFirewall);
        }

        filterChainProxy.afterPropertiesSet();
        Filter result = filterChainProxy;
        if (this.debugEnabled) {
            this.logger.warn("\n\n********************************************************************\n**********        Security debugging is enabled.       *************\n**********    This may include sensitive information.  *************\n**********      Do not use in a production system!     *************\n********************************************************************\n\n");
            result = new DebugFilter(filterChainProxy);
        }

        this.postBuildAction.run();
        return (Filter)result;
    }

securityFilterChainBuilders（其实就是HttpSecurity）的build方法，内部最后也是调用自己的init、configure、performBuild。

2.3.1. init（HttpSecurity）
会遍历所有之前加载好的配置类configuator，调用其init
配置类的init一般是配置HttpSecurity。以HttpBasicConfigurer配置类为例：

    public void init(B http) throws Exception {
        this.registerDefaults(http);
    }

    private void registerDefaults(B http) {
        ContentNegotiationStrategy contentNegotiationStrategy = (ContentNegotiationStrategy)http.getSharedObject(ContentNegotiationStrategy.class);
        if (contentNegotiationStrategy == null) {
            contentNegotiationStrategy = new HeaderContentNegotiationStrategy();
        }

        MediaTypeRequestMatcher restMatcher = new MediaTypeRequestMatcher((ContentNegotiationStrategy)contentNegotiationStrategy, new MediaType[]{MediaType.APPLICATION_ATOM_XML, MediaType.APPLICATION_FORM_URLENCODED, MediaType.APPLICATION_JSON, MediaType.APPLICATION_OCTET_STREAM, MediaType.APPLICATION_XML, MediaType.MULTIPART_FORM_DATA, MediaType.TEXT_XML});
        restMatcher.setIgnoredMediaTypes(Collections.singleton(MediaType.ALL));
        RequestMatcher notHtmlMatcher = new NegatedRequestMatcher(new MediaTypeRequestMatcher((ContentNegotiationStrategy)contentNegotiationStrategy, new MediaType[]{MediaType.TEXT_HTML}));
        RequestMatcher restNotHtmlMatcher = new AndRequestMatcher(Arrays.asList(notHtmlMatcher, restMatcher));
        RequestMatcher preferredMatcher = new OrRequestMatcher(Arrays.asList(X_REQUESTED_WITH, restNotHtmlMatcher));
        this.registerDefaultEntryPoint(http, preferredMatcher);
        this.registerDefaultLogoutSuccessHandler(http, preferredMatcher);
    }

2.3.2. configure（HttpSecurity）
会遍历所有之前加载好的配置类configuator，调用其configure
配置类的configure一般构造Filter，添加到HttpSecurity的Filter列表中，作为过滤器链的其中一个。以HttpBasicConfigurer配置类为例：

    public void configure(B http) throws Exception {
        AuthenticationManager authenticationManager = (AuthenticationManager)http.getSharedObject(AuthenticationManager.class);
        BasicAuthenticationFilter basicAuthenticationFilter = new BasicAuthenticationFilter(authenticationManager, this.authenticationEntryPoint);
        if (this.authenticationDetailsSource != null) {
            basicAuthenticationFilter.setAuthenticationDetailsSource(this.authenticationDetailsSource);
        }

        RememberMeServices rememberMeServices = (RememberMeServices)http.getSharedObject(RememberMeServices.class);
        if (rememberMeServices != null) {
            basicAuthenticationFilter.setRememberMeServices(rememberMeServices);
        }

        basicAuthenticationFilter = (BasicAuthenticationFilter)this.postProcess(basicAuthenticationFilter);
        http.addFilter(basicAuthenticationFilter);
    }

2.3.3. performBuild（HttpSecurity）
将List<Filter>以及matcher封装成SecurityFilterChain

    protected DefaultSecurityFilterChain performBuild() throws Exception {
        Collections.sort(this.filters, this.comparator);
        return new DefaultSecurityFilterChain(this.requestMatcher, this.filters);
    }

请求来时，FilterChainProxy如何起作用

请求到达的时候，FilterChainProxy的dofilter()方法内部，会遍历所有的SecurityFilterChain，匹配url，第一个匹配到之后则调用该SecurityFilterChain中的List<filter>依次做认证或鉴权，执行最后调用外层传入的filterchain，将控制权交给上层过滤链，即spring 的过滤链。
核心逻辑如下：

    private void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        FirewalledRequest fwRequest = this.firewall.getFirewalledRequest((HttpServletRequest)request);
        HttpServletResponse fwResponse = this.firewall.getFirewalledResponse((HttpServletResponse)response);
        List<Filter> filters = this.getFilters((HttpServletRequest)fwRequest);//选择匹配的过滤器链
        if (filters != null && filters.size() != 0) {
            FilterChainProxy.VirtualFilterChain vfc = new FilterChainProxy.VirtualFilterChain(fwRequest, chain, filters);
            vfc.doFilter(fwRequest, fwResponse);//将请求交给该过滤器链，逐个通过filter进行验证
        } else {
            if (logger.isDebugEnabled()) {
                logger.debug(UrlUtils.buildRequestUrl(fwRequest) + (filters == null ? " has no matching filters" : " has an empty filter list"));
            }

            fwRequest.reset();
            chain.doFilter(fwRequest, fwResponse);//security逻辑已执行完，交给上层
        }
    }
//取第一个匹配的过滤器链
    private List<Filter> getFilters(HttpServletRequest request) {
        Iterator var2 = this.filterChains.iterator();

        SecurityFilterChain chain;
        do {
            if (!var2.hasNext()) {
                return null;
            }

            chain = (SecurityFilterChain)var2.next();
        } while(!chain.matches(request));

        return chain.getFilters();
    }

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