spring security源码分析心得

看了半天的文档及源码，终于理出了spring-security的一些总体思路，spring security主要分认证(authentication)和授权(authority)。

1.认证authentication

认证主要代码在spring-security-core下的包org.springframework.security.authentication下，主类：AuthenticationManager、AuthenticationProvider

其关系如下：

 2.授权Authorization

授权也称Access Control，主要代码在spring-security-core下的包org.springframework.security.access下，主类：AccessDecisionManager、SecurityMetadataSource。它们的关系通过ConfigAttribute关联起来。

SecurityMetadataSource获取ConfigAttribute，方法：

Collection<ConfigAttribute> getAttributes(Object object)throws IllegalArgumentException;

AccessDecisionManager根据进行授权，方法：

void decide(Authentication authentication, Object object,Collection<ConfigAttribute> configAttributes) throws AccessDeniedException,InsufficientAuthenticationException;

其实现类：AffirmativeBased的授权逻辑如下：

/**
     * This concrete implementation simply polls all configured
     * {@link AccessDecisionVoter}s and grants access if any
     * <code>AccessDecisionVoter</code> voted affirmatively. Denies access only if there
     * was a deny vote AND no affirmative votes.
     * <p>
     * If every <code>AccessDecisionVoter</code> abstained from voting, the decision will
     * be based on the {@link #isAllowIfAllAbstainDecisions()} property (defaults to
     * false).
     * </p>
     *
     * @param authentication the caller invoking the method
     * @param object the secured object
     * @param configAttributes the configuration attributes associated with the method
     * being invoked
     *
     * @throws AccessDeniedException if access is denied
     */
    public void decide(Authentication authentication, Object object,
            Collection<ConfigAttribute> configAttributes) throws AccessDeniedException {
        int deny = 0;

        for (AccessDecisionVoter voter : getDecisionVoters()) {
            int result = voter.vote(authentication, object, configAttributes);

            if (logger.isDebugEnabled()) {
                logger.debug("Voter: " + voter + ", returned: " + result);
            }

            switch (result) {
            case AccessDecisionVoter.ACCESS_GRANTED:
                return;

            case AccessDecisionVoter.ACCESS_DENIED:
                deny++;

                break;

            default:
                break;
            }
        }

        if (deny > 0) {
            throw new AccessDeniedException(messages.getMessage(
                    "AbstractAccessDecisionManager.accessDenied", "Access is denied"));
        }

        // To get this far, every AccessDecisionVoter abstained
        checkAllowIfAllAbstainDecisions();
    }

从上文可以看出，真正的授权是通过AccessDecisionVoter来完成的。

3.认证和授权的集成AbstractSecurityInterceptor

AbstractSecurityInterceptor包含了四个instance及其get/set方法

    private AccessDecisionManager accessDecisionManager;
    private AfterInvocationManager afterInvocationManager;
    private AuthenticationManager authenticationManager = new NoOpAuthenticationManager();
    private RunAsManager runAsManager = new NullRunAsManager();

加一个抽象的方法：

    /**
     * Indicates the type of secure objects the subclass will be presenting to the
     * abstract parent for processing. This is used to ensure collaborators wired to the
     * {@code AbstractSecurityInterceptor} all support the indicated secure object class.
     *
     * @return the type of secure object the subclass provides services for
     */
    public abstract Class<?> getSecureObjectClass();

AbstractSecurityInterceptor的实现类有两个：

3.1 FilterSecurityInterceptor

定义：

/**
 * Performs security handling of HTTP resources via a filter implementation.
 * <p>
 * The <code>SecurityMetadataSource</code> required by this security interceptor is of
 * type {@link FilterInvocationSecurityMetadataSource}.
 * <p>
 * Refer to {@link AbstractSecurityInterceptor} for details on the workflow.
 * </p>
 *
 * @author Ben Alex
 * @author Rob Winch
 */
public class FilterSecurityInterceptor extends AbstractSecurityInterceptor implements Filter {}

实现了标准的servlet的Filter接口，其逻辑如下：

    /**
     * Method that is actually called by the filter chain. Simply delegates to the
     * {@link #invoke(FilterInvocation)} method.
     *
     * @param request the servlet request
     * @param response the servlet response
     * @param chain the filter chain
     *
     * @throws IOException if the filter chain fails
     * @throws ServletException if the filter chain fails
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        FilterInvocation fi = new FilterInvocation(request, response, chain);
        invoke(fi);
    }

最重要的实现invoke

    public void invoke(FilterInvocation fi) throws IOException, ServletException {
        if ((fi.getRequest() != null)
                && (fi.getRequest().getAttribute(FILTER_APPLIED) != null)
                && observeOncePerRequest) {
            // filter already applied to this request and user wants us to observe
            // once-per-request handling, so don't re-do security checking
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
        }
        else {
            // first time this request being called, so perform security checking
            if (fi.getRequest() != null) {
                fi.getRequest().setAttribute(FILTER_APPLIED, Boolean.TRUE);
            }

            InterceptorStatusToken token = super.beforeInvocation(fi);

            try {
                fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
            }
            finally {
                super.finallyInvocation(token);
            }

            super.afterInvocation(token, null);
        }
    }

3.2 MethodSecurityInterceptor

定义：

/**
 * Provides security interception of AOP Alliance based method invocations.
 * <p>
 * The <code>SecurityMetadataSource</code> required by this security interceptor is of
 * type {@link MethodSecurityMetadataSource}. This is shared with the AspectJ based
 * security interceptor (<code>AspectJSecurityInterceptor</code>), since both work with
 * Java <code>Method</code>s.
 * <p>
 * Refer to {@link AbstractSecurityInterceptor} for details on the workflow.
 *
 * @author Ben Alex
 * @author Rob Winch
 */
public class MethodSecurityInterceptor extends AbstractSecurityInterceptor implements
        MethodInterceptor {}

其invoke方法如下：

    /**
     * This method should be used to enforce security on a <code>MethodInvocation</code>.
     *
     * @param mi The method being invoked which requires a security decision
     *
     * @return The returned value from the method invocation (possibly modified by the
     * {@code AfterInvocationManager}).
     *
     * @throws Throwable if any error occurs
     */
    public Object invoke(MethodInvocation mi) throws Throwable {
        InterceptorStatusToken token = super.beforeInvocation(mi);

        Object result;
        try {
            result = mi.proceed();
        }
        finally {
            super.finallyInvocation(token);
        }
        return super.afterInvocation(token, result);
    }

 4.Spring Security Java Config ---@EnableWebSecurity

 将@EnableWebSecurity注解加到@Configuration下来获得spring securiy的安全性。

WebSecurityConfigurer定义的配置或者对WebSecurityConfigurerAdapter类的扩展类示例如下：

  @Configuration
  @EnableWebSecurity
  public class MyWebSecurityConfiguration extends WebSecurityConfigurerAdapter {
 
      @Override
      public void configure(WebSecurity web) throws Exception {
          web.ignoring()
          // Spring Security should completely ignore URLs starting with /resources/
                  .antMatchers("/resources/");
      }
 
      @Override
      protected void configure(HttpSecurity http) throws Exception {
          http.authorizeRequests().antMatchers("/public/").permitAll().anyRequest()
                  .hasRole("USER").and()
                  // Possibly more configuration ...
                  .formLogin() // enable form based log in
                  // set permitAll for all URLs associated with Form Login
                  .permitAll();
      }
 
      @Override
      protected void configure(AuthenticationManagerBuilder auth) {
          auth
          // enable in memory based authentication with a user named "user" and "admin"
          .inMemoryAuthentication().withUser("user").password("password").roles("USER")
                  .and().withUser("admin").password("password").roles("USER", "ADMIN");
      }
 
      // Possibly more overridden methods ...
  }

4.1 WebSecurityConfigurer

 WebSecurityConfigurer允许对WebSecurity进行定制化，在绝大部分情景下，开发者使用@EnableWebSecurity注解或者对WebSecurityConfigurerAdapter进行重写的方式来自动应用@EnableWebSecurity注解。定义如下：

public interface WebSecurityConfigurer<T extends SecurityBuilder<Filter>> extends
        SecurityConfigurer<Filter, T> {

}

4.2 WebSecurityConfigurerAdapter

WebSecurityConfigurerAdapter提供了创建WebSecurityConfigurer实例的便利方法，它是一个基类。该类的实现通过重写方法来实现定制化。

它自动从SpringFactoriesLoader查找AbstractHttpConfigurer，从而让开发者可以扩展。为达到这个目的，必须创建一个AbstractHttpConfigurer的扩展类，然后在classpath路径下创建一个文件META-INF/spring.factories，示例如下：

org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer = sample.MyClassThatExtendsAbstractHttpConfigurer

如果你有多个扩展类，可以使用逗号分隔，示例如下：

 org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer = sample.MyClassThatExtendsAbstractHttpConfigurer, sample.OtherThatExtendsAbstractHttpConfigurer

 4.2.1 初始化

 初始化分两个过程：获取HttpSecurity，配置FilterSecurityInterceptor到WebSecurity

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

获取HttpSecurity的过程：

/**
     * Creates the {@link HttpSecurity} or returns the current instance
     *
     * ] * @return the {@link HttpSecurity}
     * @throws Exception
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    protected final HttpSecurity getHttp() throws Exception {
        if (http != null) {
            return http;
        }

        DefaultAuthenticationEventPublisher eventPublisher = objectPostProcessor
                .postProcess(new DefaultAuthenticationEventPublisher());
        localConfigureAuthenticationBldr.authenticationEventPublisher(eventPublisher);

        AuthenticationManager authenticationManager = authenticationManager();
        authenticationBuilder.parentAuthenticationManager(authenticationManager);
        Map<Class<? extends Object>, Object> sharedObjects = createSharedObjects();

        http = new HttpSecurity(objectPostProcessor, authenticationBuilder,
                sharedObjects);
        if (!disableDefaults) {
            // @formatter:off
            http
                .csrf().and()
                .addFilter(new WebAsyncManagerIntegrationFilter())
                .exceptionHandling().and()
                .headers().and()
                .sessionManagement().and()
                .securityContext().and()
                .requestCache().and()
                .anonymous().and()
                .servletApi().and()
                .apply(new DefaultLoginPageConfigurer<HttpSecurity>()).and()
                .logout();
            // @formatter:on
            ClassLoader classLoader = this.context.getClassLoader();
            List<AbstractHttpConfigurer> defaultHttpConfigurers =
                    SpringFactoriesLoader.loadFactories(AbstractHttpConfigurer.class, classLoader);

            for(AbstractHttpConfigurer configurer : defaultHttpConfigurers) {
                http.apply(configurer);
            }
        }
        configure(http);
        return http;
    }

 5. xml配置解析类SecurityNamespaceHandler

它的解析器有以下几种：

    private void loadParsers() {
        // Parsers
        parsers.put(Elements.LDAP_PROVIDER, new LdapProviderBeanDefinitionParser());
        parsers.put(Elements.LDAP_SERVER, new LdapServerBeanDefinitionParser());
        parsers.put(Elements.LDAP_USER_SERVICE, new LdapUserServiceBeanDefinitionParser());
        parsers.put(Elements.USER_SERVICE, new UserServiceBeanDefinitionParser());
        parsers.put(Elements.JDBC_USER_SERVICE, new JdbcUserServiceBeanDefinitionParser());
        parsers.put(Elements.AUTHENTICATION_PROVIDER,
                new AuthenticationProviderBeanDefinitionParser());
        parsers.put(Elements.GLOBAL_METHOD_SECURITY,
                new GlobalMethodSecurityBeanDefinitionParser());
        parsers.put(Elements.AUTHENTICATION_MANAGER,
                new AuthenticationManagerBeanDefinitionParser());
        parsers.put(Elements.METHOD_SECURITY_METADATA_SOURCE,
                new MethodSecurityMetadataSourceBeanDefinitionParser());

        // Only load the web-namespace parsers if the web classes are available
        if (ClassUtils.isPresent(FILTER_CHAIN_PROXY_CLASSNAME, getClass()
                .getClassLoader())) {
            parsers.put(Elements.DEBUG, new DebugBeanDefinitionParser());
            parsers.put(Elements.HTTP, new HttpSecurityBeanDefinitionParser());
            parsers.put(Elements.HTTP_FIREWALL, new HttpFirewallBeanDefinitionParser());
            parsers.put(Elements.FILTER_SECURITY_METADATA_SOURCE,
                    new FilterInvocationSecurityMetadataSourceParser());
            parsers.put(Elements.FILTER_CHAIN, new FilterChainBeanDefinitionParser());
            filterChainMapBDD = new FilterChainMapBeanDefinitionDecorator();
        }

        if (ClassUtils.isPresent(MESSAGE_CLASSNAME, getClass().getClassLoader())) {
            parsers.put(Elements.WEBSOCKET_MESSAGE_BROKER,
                    new WebSocketMessageBrokerSecurityBeanDefinitionParser());
        }
    }

6.小结

spring支持注解和xml配置两种方式，因此分析源码可以从xml配置及注解两方面入手，相互印证。

参考文献：

【1】https://spring.io/guides/topicals/spring-security-architecture/

 【2】http://zzy.cincout.cn/2016/12/23/spring-security-2016-12-23-spring-security-01/