Spring Security 源码解读：权限控制

本文样例代码地址： spring-security-oauth2.0-sample。

关于此章，官网介绍：Authorization

本文使用Spring Boot 2.7.4版本，对应Spring Security 5.7.3版本。

Introduction

认证过程中会一并获得用户权限，Authentication#getAuthorities接口方法提供权限，认证过后即是鉴权，Spring Security使用GrantedAuthority接口代表权限。早期版本在FilterChain中使用FilterSecurityInterceptor中执行鉴权过程，现使用AuthorizationFilter执行，开始执行顺序两者一致，此外，Filter中具体实现也由 AccessDecisionManager + AccessDecisionVoter 变为 AuthorizationManager

本文关注新版本的实现：AuthorizationFilter和AuthorizationManager。

AuthorizationManager最常用的实现类为RequestMatcherDelegatingAuthorizationManager，其中会根据你的配置生成一系列RequestMatcherEntry，每个entry中包含一个匹配器RequestMatcher和泛型类被匹配对象。

UML类图结构如下：

另外，对于 method security ，实现方式主要为AOP+Spring EL，常用权限方法注解为：

• @EnableMethodSecurity
• @PreAuthorize
• @PostAuthorize
• @PreFilter
• @PostFilter
• @Secured

这些注解可以用在controller方法上用于权限控制，注解中填写Spring EL表述权限信息。这些注解一起使用时的执行顺序由枚举类AuthorizationInterceptorsOrder控制：

public enum AuthorizationInterceptorsOrder {

	FIRST(Integer.MIN_VALUE),
	/**
	 * {@link PreFilterAuthorizationMethodInterceptor}
	 */
	PRE_FILTER,
	PRE_AUTHORIZE,
	SECURED,
	JSR250,
	POST_AUTHORIZE,
	/**
	 * {@link PostFilterAuthorizationMethodInterceptor}
	 */
	POST_FILTER,
	LAST(Integer.MAX_VALUE);
	...
}

而这些权限注解的提取和配置主要由org.springframework.security.config.annotation.method.configuration包下的几个配置类完成：

• PrePostMethodSecurityConfiguration
• SecuredMethodSecurityConfiguration

等

权限配置

权限配置可以通过两种方式配置：

• SecurityFilterChain配置类配置
• @EnableMethodSecurity 开启方法上注解配置

下面是关于SecurityFilterChain的权限配置，以及method security使用

@Configuration
// 其中prepostEnabled默认true,其他注解配置默认false,需手动改为true
@EnableMethodSecurity(securedEnabled = true)
@RequiredArgsConstructor
public class SecurityConfig {
	// 白名单
	private static final String[] AUTH_WHITELIST = ... 

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {

	    // antMatcher or mvcMatcher
        http.authorizeHttpRequests()
                .antMatchers(AUTH_WHITELIST).permitAll()
                // hasRole中不需要添加 ROLE_前缀
                // ant 匹配 /admin /admin/a /admin/a/b 都会匹配上
                .antMatchers("/admin/**").hasRole("ADMIN")
                .anyRequest().authenticated();
                // denyAll慎用
//                .anyRequest().denyAll();

//        http.authorizeHttpRequests()
//                .mvcMatchers(AUTH_WHITELIST).permitAll()
//                        // 效果同上
//                        .mvcMatchers("/admin").hasRole("ADMIN")
//                        .anyRequest().denyAll();
    }

}

以@PreAuthorize为例，在controller方法上使用：

@Api("user")
@RestController
@RequestMapping("/user")
@RequiredArgsConstructor
public class UserController {

	/**
     * {@link EnableMethodSecurity} 注解必须配置在配置类上

     * {@link PreAuthorize}等注解中表达式使用 Spring EL
     * @return
     */
    @PreAuthorize("hasRole('ADMIN')")
    @GetMapping("/admin")
    public ResponseEntity<Map<String, Object>> admin() {
        return ResponseEntity.ok(Collections.singletonMap("msg","u r admin"));
    }
}

源码

配置类权限控制

AuthorizationFilter

public class AuthorizationFilter extends OncePerRequestFilter {
	
	// 在配置类中默认实现为 RequestMatcherDelegatingAuthorizationManager
	private final AuthorizationManager<HttpServletRequest> authorizationManager;

		@Override
	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {
		// 委托给AuthorizationManager
		AuthorizationDecision decision = this.authorizationManager.check(this::getAuthentication, request);
		if (decision != null && !decision.isGranted()) {
			throw new AccessDeniedException("Access Denied");
		}
		filterChain.doFilter(request, response);
	}


}

来看看AuthorizationManager默认实现RequestMatcherDelegatingAuthorizationManager：

public final class RequestMatcherDelegatingAuthorizationManager implements AuthorizationManager<HttpServletRequest> {
	// http.authorizeHttpRequests().antMatchers(AUTH_WHITELIST)...
	// SecurityFilterChain中每配置一项就会增加一个Entry
	// RequestMatcherEntry包含一个RequestMatcher和一个待鉴权对象，这里是AuthorizationManager
	private final List<RequestMatcherEntry<AuthorizationManager<RequestAuthorizationContext>>> mappings;
	...
	@Override
	public AuthorizationDecision check(Supplier<Authentication> authentication, HttpServletRequest request) {
		
		for (RequestMatcherEntry<AuthorizationManager<RequestAuthorizationContext>> mapping : this.mappings) {

			RequestMatcher matcher = mapping.getRequestMatcher();
			MatchResult matchResult = matcher.matcher(request);
			if (matchResult.isMatch()) {
				AuthorizationManager<RequestAuthorizationContext> manager = mapping.getEntry();
				return manager.check(authentication,
						new RequestAuthorizationContext(request, matchResult.getVariables()));
			}
		}
		return null;
	}
}

方法权限控制

总的实现基于 AOP + Spring EL

以案例中 @PreAuthorize注解的源码为例

PrePostMethodSecurityConfiguration

@Configuration(proxyBeanMethods = false)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
final class PrePostMethodSecurityConfiguration {

	private final AuthorizationManagerBeforeMethodInterceptor preAuthorizeAuthorizationMethodInterceptor;
	private final PreAuthorizeAuthorizationManager preAuthorizeAuthorizationManager = new PreAuthorizeAuthorizationManager();
	private final DefaultMethodSecurityExpressionHandler expressionHandler = new DefaultMethodSecurityExpressionHandler();
	...

	@Autowired
	PrePostMethodSecurityConfiguration(ApplicationContext context) {
		// 设置 Spring EL 解析器
		this.preAuthorizeAuthorizationManager.setExpressionHandler(this.expressionHandler);	
		// 拦截@PreAuthorize方法
		this.preAuthorizeAuthorizationMethodInterceptor = AuthorizationManagerBeforeMethodInterceptor
				.preAuthorize(this.preAuthorizeAuthorizationManager);
		...
	}
	...
}

AuthorizationManagerBeforeMethodInterceptor

基于AOP实现

public final class AuthorizationManagerBeforeMethodInterceptor
		implements Ordered, MethodInterceptor, PointcutAdvisor, AopInfrastructureBean {

	/**
	 * 调用起点
	 */
	public static AuthorizationManagerBeforeMethodInterceptor preAuthorize() {		
		// 针对 @PreAuthorize注解提供的AuthorizationManager为PreAuthorizeAuthorizationManager
		return preAuthorize(new PreAuthorizeAuthorizationManager());
	}

	/**
	 * 初始化，创建基于@PreAuthorize注解的aop方法拦截器
	 * Creates an interceptor for the {@link PreAuthorize} annotation
	 * @param authorizationManager the {@link PreAuthorizeAuthorizationManager} to use
	 * @return the interceptor
	 */
	public static AuthorizationManagerBeforeMethodInterceptor preAuthorize(
			PreAuthorizeAuthorizationManager authorizationManager) {
		AuthorizationManagerBeforeMethodInterceptor interceptor = new AuthorizationManagerBeforeMethodInterceptor(
				AuthorizationMethodPointcuts.forAnnotations(PreAuthorize.class), authorizationManager);
		interceptor.setOrder(AuthorizationInterceptorsOrder.PRE_AUTHORIZE.getOrder());
		return interceptor;
	}
	...	
	// 实现MethodInterceptor方法，在调用实际方法是会首先触发这个
	@Override
	public Object invoke(MethodInvocation mi) throws Throwable {
		// 先鉴权
		attemptAuthorization(mi);
		// 后执行实际方法
		return mi.proceed();
	}

	private void attemptAuthorization(MethodInvocation mi) {
		// 判断, @PreAuthorize方法用的manager就是
		// PreAuthorizeAuthorizationManager
		// 是通过上面的static类构造的
		AuthorizationDecision decision = this.authorizationManager.check(AUTHENTICATION_SUPPLIER, mi);
		if (decision != null && !decision.isGranted()) {
			throw new AccessDeniedException("Access Denied");
		}
		...
	}
	
	static final Supplier<Authentication> AUTHENTICATION_SUPPLIER = () -> {
		Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
		if (authentication == null) {
			throw new AuthenticationCredentialsNotFoundException(
					"An Authentication object was not found in the SecurityContext");
		}
		return authentication;
	};
}

针对@PreAuthorize方法用的manager就是 PreAuthorizeAuthorizationManager#check，下面来看看

PreAuthorizeAuthorizationManager

public final class PreAuthorizeAuthorizationManager implements AuthorizationManager<MethodInvocation> {
	private final PreAuthorizeExpressionAttributeRegistry registry = new PreAuthorizeExpressionAttributeRegistry();
	private MethodSecurityExpressionHandler expressionHandler = new DefaultMethodSecurityExpressionHandler();

	@Override
	public AuthorizationDecision check(Supplier<Authentication> authentication, MethodInvocation mi) {
		// 获取方法上@PreAuthorize注解中的Spring EL 表达式属性
		ExpressionAttribute attribute = this.registry.getAttribute(mi);
		if (attribute == ExpressionAttribute.NULL_ATTRIBUTE) {
			return null;
		}
		// Spring EL 的 context
		EvaluationContext ctx = this.expressionHandler.createEvaluationContext(authentication.get(), mi);
		// 执行表达式中结果, 会执行SecurityExpressionRoot类中对应方法。涉及Spring EL执行原理，pass
		boolean granted = ExpressionUtils.evaluateAsBoolean(attribute.getExpression(), ctx);	
		// 返回结果
		return new ExpressionAttributeAuthorizationDecision(granted, attribute);
	}

}