通过前面的分析我们知道经过filterchain的层层赛选后,请求来到了FilterSecurityInterceptor进行权限校验,那么其底层是如何实现的呢,通过本文带你了解其底层实现原理
一 授权流程整体分析
-
当客户端向某个资源发起请求，请求到达
FilterSecurityInterceptor，然后会调用其父类AbstractSecurityInterceptor
的beforeInvocation方法做授权之前的准备工作 -
在beforeInvocation法中通过
SecurityMetadataSource…getAttributes(object);获得资源所需要的访问权限 ，通过SecurityContextHolder.getContext().getAuthentication()获取当前认证用户的认证信息，即包含了认证信息和权限信息的Authentication对象 -
然后FilterSecurityInterceptor通过调用
AccessDecisionManager.decide(authenticated, object, attributes);进行授权(authenticated中有用户的权限列表，attributes是资源需要的权限)，该方法使用投票器投票来决定用户是否有资源访问权限
AccessDecisionManager接口有三个实现类，他们通过通过AccessDecisionVoter投票器完成投票，三种投票策略如下：
AffirmativeBased ： 只需有一个投票赞成即可通过
ConsensusBased：需要大多数投票赞成即可通过，平票可以配置
UnanimousBased：需要所有的投票赞成才能通过 -
投票通过,访问到对应的站点
二 源码分析
2.1 FilterSecurityInterceptor的创建
通过package org.springframework.security.config.http.HttpConfigurationBuilder中createFilterSecurityInterceptor()创建FilterSecurityInterceptor
void createFilterSecurityInterceptor(BeanReference authManager) {
//判断是否配置了use-expressions属性
//使用 Spring 表达式语言配置访问控制
//注意下方备注
boolean useExpressions = FilterInvocationSecurityMetadataSourceParser.isUseExpressions(httpElt);
//根据intercept-url标签列表创建授权需要的元数据信息。httpElt里面有要去的资源路径。根据它们得出securityMds。上面有说明。后面仔细分析
BeanDefinition securityMds = FilterInvocationSecurityMetadataSourceParser.createSecurityMetadataSource(interceptUrls, httpElt, pc);
RootBeanDefinition accessDecisionMgr;
//创建voter列表，方便使用投票器
ManagedList<BeanDefinition> voters = new ManagedList<BeanDefinition>(2);
//根据不同情况使用不同投票器
//如果是使用了表达式，使用WebExpressionVoter
//没使用表达式，就使用RoleVoter、AuthenticatedVoter
if (useExpressions) {
voters.add(new RootBeanDefinition(WebExpressionVoter.class));
} else {
voters.add(new RootBeanDefinition(RoleVoter.class));
voters.add(new RootBeanDefinition(AuthenticatedVoter.class));
}
//通过改变BeanDefinition里面的信息，来改变创建对象授权的决策管理类AffirmativeBased的bean
accessDecisionMgr = new RootBeanDefinition(AffirmativeBased.class);
//添加依赖的voter列表
accessDecisionMgr.getPropertyValues().addPropertyValue("decisionVoters", voters);
accessDecisionMgr.setSource(pc.extractSource(httpElt));
// Set up the access manager reference for http
//access-decision-manager-ref属性，可以使我们手动注入AccessDecisionManager(认证管理器)，下面是详细配置
String accessManagerId = httpElt.getAttribute(""access-decision-manager-ref"");
//如果未定义access-decision-manager-ref属性，就使用默认的
//AffirmativeBased
if (!StringUtils.hasText(accessManagerId)) {
accessManagerId = pc.getReaderContext().generateBeanName(accessDecisionMgr);
pc.registerBeanComponent(new BeanComponentDefinition(accessDecisionMgr, accessManagerId));
}
//创建FilterSecurityInterceptor过滤器，通过BeanDefinitionBuilder来手动注入bean，下面有提示
BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(FilterSecurityInterceptor.class);
//往创建FilterSecurityInterceptor过滤器添加决策管理器
// // 设置属性accessDecisionManager,此属性引用已经定义的String accessManagerId
builder.addPropertyReference("accessDecisionManager", accessManagerId);
//往创建FilterSecurityInterceptor过滤器添加认证管理类
//设置属性authenticationManager,此属性引用已经定义的bean authManager
builder.addPropertyValue("authenticationManager", authManager);
if ("false".equals(httpElt.getAttribute(ATT_ONCE_PER_REQUEST))) {
builder.addPropertyValue("observeOncePerRequest", Boolean.FALSE);
}
//添加授权需要的安全元数据资源
builder.addPropertyValue("securityMetadataSource", securityMds);
//得到FilterSecurityInterceptor过滤器的BeanDefinition，通过BeanDefinition创建bean
BeanDefinition fsiBean = builder.getBeanDefinition();
//向ioc容器注册FilterSecurityInterceptor的bean
String fsiId = pc.getReaderContext().generateBeanName(fsiBean);
pc.registerBeanComponent(new BeanComponentDefinition(fsiBean,fsiId));
// Create and register a DefaultWebInvocationPrivilegeEvaluator for use with taglibs etc.
BeanDefinition wipe = new RootBeanDefinition(DefaultWebInvocationPrivilegeEvaluator.class);
wipe.getConstructorArgumentValues().addGenericArgumentValue(new RuntimeBeanReference(fsiId));
pc.registerBeanComponent(new BeanComponentDefinition(wipe, pc.getReaderContext().generateBeanName(wipe)));
this.fsi = new RuntimeBeanReference(fsiId);
}
- BeanDefinition在Spring中是用来描述Bean对象的，其不是一个bean实例，仅仅是包含bean实例的所有信息，比如属性值、构造器参数以及其他信息。Bean对象创建是根据BeanDefinitionc中描述的信息来创建的，BeanDefinitionc存在的作用是为了可以方便的进行修改属性值和其他元信息，比如通过BeanFactoryPostProcessor进行修改一些信息，然后在创建Bean对象的时候就可以结合原始信息和修改后的信息创建对象了。
- BeanDefinition spring一开始都是使用GenericBeanDefinition类保存Bean的相关信息，在需要时，在将其转换为其他的BeanDefinition类型
- BeanDefinitionBuilder作用是手动向BeanDefinition注入信息然后通过BeanDefinition手动Spring容器中注入Bean
2.2 SecurityMetadataSource的创建
通过org.springframework.security.config.http.FilterInvocationSecurityMetadataSourceParser中的createSecurityMetadataSource用于SecurityMetadataSource的创建
static BeanDefinition createSecurityMetadataSource(List<Element> interceptUrls, Element elt, ParserContext pc) {
//创建Url处理类，有两个实现：AntUrlPathMatcher、RegexUrlPathMatcher是spring的路径匹配工具类
UrlMatcher matcher = HttpSecurityBeanDefinitionParser.createUrlMatcher(elt);
boolean useExpressions = isUseExpressions(elt);
//解析intercept-url标签，构造所有需要拦截url的map信息
//map中的key：RequestKey的bean定义，value：SecurityConfig的bean定义
ManagedMap<BeanDefinition, BeanDefinition> requestToAttributesMap = parseInterceptUrlsForFilterInvocationRequestMap(
interceptUrls, useExpressions, pc);
BeanDefinitionBuilder fidsBuilder;
if (useExpressions) {
//定义表达式处理类的bean
Element expressionHandlerElt = DomUtils.getChildElementByTagName(elt, Elements.EXPRESSION_HANDLER);
String expressionHandlerRef = expressionHandlerElt == null ? null : expressionHandlerElt.getAttribute("ref");
if (StringUtils.hasText(expressionHandlerRef)) {
logger.info("Using bean '" + expressionHandlerRef + "' as web SecurityExpressionHandler implementation");
} else {
BeanDefinition expressionHandler = BeanDefinitionBuilder.rootBeanDefinition(DefaultWebSecurityExpressionHandler.class).getBeanDefinition();
expressionHandlerRef = pc.getReaderContext().generateBeanName(expressionHandler);
pc.registerBeanComponent(new BeanComponentDefinition(expressionHandler, expressionHandlerRef));
}
//定义表达式类型的FilterInvocationSecurityMetadataSource
fidsBuilder = BeanDefinitionBuilder.rootBeanDefinition(ExpressionBasedFilterInvocationSecurityMetadataSource.class);
//通过构造函数注入依赖
fidsBuilder.addConstructorArgValue(matcher);
fidsBuilder.addConstructorArgValue(requestToAttributesMap);
fidsBuilder.addConstructorArgReference(expressionHandlerRef);
} else {
//定义非表达式类型的FilterInvocationSecurityMetadataSource
fidsBuilder = BeanDefinitionBuilder.rootBeanDefinition(DefaultFilterInvocationSecurityMetadataSource.class);
//通过构造函数注入依赖
fidsBuilder.addConstructorArgValue(matcher);
fidsBuilder.addConstructorArgValue(requestToAttributesMap);
}
fidsBuilder.addPropertyValue("stripQueryStringFromUrls", matcher instanceof AntUrlPathMatcher);
fidsBuilder.getRawBeanDefinition().setSource(pc.extractSource(elt));
return fidsBuilder.getBeanDefinition();
}
2.3 FilterSecurityInterceptor鉴权
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
//封装request, response, chain，方便参数传递、增加代码阅读性
FilterInvocation fi = new FilterInvocation(request, response, chain);
invoke(fi);
}
public void invoke(FilterInvocation fi) throws IOException, ServletException {
if ((fi.getRequest() != null) && (fi.getRequest().getAttribute(FILTER_APPLIED) != null)
&& observeOncePerRequest) {
if (fi.getRequest() != null) {
fi.getRequest().setAttribute(FILTER_APPLIED, Boolean.TRUE);
}
//执行父类beforeInvocation，类似于aop中的before
InterceptorStatusToken token = super.beforeInvocation(fi);
try {
//filter传递
fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
} finally {
//执行父类的afterInvocation，类似于aop中的after
super.afterInvocation(token, null);
}
}
}
在FilterSecurityInterceptor中，会调用父类的beforeInvocation(filterInvocation)方法进行处理，最终返回一个InterceptorStatusToken对象，它就是spring security处理鉴权的入口。
protected InterceptorStatusToken beforeInvocation(Object object) {
Assert.notNull(object, "Object was null");
// 1. 判断object是不是FilterInvocation
if (!getSecureObjectClass().isAssignableFrom(object.getClass())) {
throw new IllegalArgumentException("Security invocation attempted for object " + object.getClass().getName()
+ " but AbstractSecurityInterceptor only configured to support secure objects of type: "
+ getSecureObjectClass());
}
// 2. 获取配置的访问控制规则 any request =》authenticated ，没有配置，return null
Collection<ConfigAttribute> attributes = this.obtainSecurityMetadataSource().getAttributes(object);
if (CollectionUtils.isEmpty(attributes)) {
Assert.isTrue(!this.rejectPublicInvocations,
() -> "Secure object invocation " + object
+ " was denied as public invocations are not allowed via this interceptor. "
+ "This indicates a configuration error because the "
+ "rejectPublicInvocations property is set to 'true'");
if (this.logger.isDebugEnabled()) {
this.logger.debug(LogMessage.format("Authorized public object %s", object));
}
publishEvent(new PublicInvocationEvent(object));
return null; // no further work post-invocation
}
// 3. 判断认证对象Authentication是否为null
if (SecurityContextHolder.getContext().getAuthentication() == null) {
credentialsNotFound(this.messages.getMessage("AbstractSecurityInterceptor.authenticationNotFound",
"An Authentication object was not found in the SecurityContext"), object, attributes);
}
// 4. 获取Authentication对象
Authentication authenticated = authenticateIfRequired();
if (this.logger.isTraceEnabled()) {
this.logger.trace(LogMessage.format("Authorizing %s with attributes %s", object, attributes));
}
// Attempt authorization
// 5. 进行授权判断
attemptAuthorization(object, attributes, authenticated);
if (this.logger.isDebugEnabled()) {
this.logger.debug(LogMessage.format("Authorized %s with attributes %s", object, attributes));
}
// 6. 发布授权成功
if (this.publishAuthorizationSuccess) {
publishEvent(new AuthorizedEvent(object, attributes, authenticated));
}
// Attempt to run as a different user
// 7. 对Authentication进行再处理，这里没有处理，直接返回null
Authentication runAs = this.runAsManager.buildRunAs(authenticated, object, attributes);
if (runAs != null) {
SecurityContext origCtx = SecurityContextHolder.getContext();
SecurityContextHolder.setContext(SecurityContextHolder.createEmptyContext());
SecurityContextHolder.getContext().setAuthentication(runAs);
if (this.logger.isDebugEnabled()) {
this.logger.debug(LogMessage.format("Switched to RunAs authentication %s", runAs));
}
// need to revert to token.Authenticated post-invocation
return new InterceptorStatusToken(origCtx, true, attributes, object);
}
this.logger.trace("Did not switch RunAs authentication since RunAsManager returned null");
// no further work post-invocation
// 8. 返回InterceptorStatusToken
return new InterceptorStatusToken(SecurityContextHolder.getContext(), false, attributes, object);
}
在beforeInvocation方法中的核心方法为
attemptAuthorization，它会调用授权管理器进行决策，当失败发生异常时，会爆出异常。
/**
* 授权判断
*
* @param object filter invocation [GET /test]
* @param attributes 配置的URL放行、需要验证路径等配置
* @param authenticated 认证对象
*/
private void attemptAuthorization(Object object, Collection<ConfigAttribute> attributes,
Authentication authenticated) {
try {
// 1. 调用授权管理器进行决策
this.accessDecisionManager.decide(authenticated, object, attributes);
} catch (AccessDeniedException ex) {
// 2. 访问被拒绝。抛出AccessDeniedException异常
if (this.logger.isTraceEnabled()) {
this.logger.trace(LogMessage.format("Failed to authorize %s with attributes %s using %s", object,
attributes, this.accessDecisionManager));
} else if (this.logger.isDebugEnabled()) {
this.logger.debug(LogMessage.format("Failed to authorize %s with attributes %s", object, attributes));
}
// 3. 发布授权失败事件
publishEvent(new AuthorizationFailureEvent(object, attributes, authenticated, ex));
throw ex;
}
}
决策者进行投票
调用授权管理器进行决策，会进入默认的决策器AffirmativeBased，上面说过它的投票机制，这里获取到的选民只有一个。
开始投票
进入WebExpressionVoter的vote方法开始投票。
// 投票
@Override
public int vote(Authentication authentication, FilterInvocation filterInvocation,
Collection<ConfigAttribute> attributes) {
// 1. 校验参数
Assert.notNull(authentication, "authentication must not be null");
Assert.notNull(filterInvocation, "filterInvocation must not be null");
Assert.notNull(attributes, "attributes must not be null");
// 2. 获取http配置项
WebExpressionConfigAttribute webExpressionConfigAttribute = findConfigAttribute(attributes);
// 3. 没有配置规则，弃权
if (webExpressionConfigAttribute == null) {
this.logger
.trace("Abstained since did not find a config attribute of instance WebExpressionConfigAttribute");
return ACCESS_ABSTAIN;
}
// 4. 对EL表达式进行处理
EvaluationContext ctx = webExpressionConfigAttribute.postProcess(
this.expressionHandler.createEvaluationContext(authentication, filterInvocation), filterInvocation);
boolean granted = ExpressionUtils.evaluateAsBoolean(webExpressionConfigAttribute.getAuthorizeExpression(), ctx);
if (granted) {
// 5. 符合条件，赞成票
return ACCESS_GRANTED;
}
this.logger.trace("Voted to deny authorization");
// 6. 最后都没有则反对票
return ACCESS_DENIED;
}
授权成功处理
没有抛出异常，则认为授权通过，FilterSecurityInterceptor会进入finallyInvocation方法。这个方法主要是判断需不需要重新设置 SecurityContext内容，这里没有配置，直接跳过。
protected void finallyInvocation(InterceptorStatusToken token) {
if (token != null && token.isContextHolderRefreshRequired()) {
SecurityContextHolder.setContext(token.getSecurityContext());
if (this.logger.isDebugEnabled()) {
this.logger.debug(LogMessage.of(() -> {
return "Reverted to original authentication " + token.getSecurityContext().getAuthentication();
}));
}
}
}
接下来进入后置处理afterInvocation方法，再次调用了finallyInvocation方法，然后查询是否还有决策后置处理器，如果有，再次进行决策。最后的最后，才代表授权成功，就交由Spring MVC ,访问到我们的controller方法了。
protected Object afterInvocation(InterceptorStatusToken token, Object returnedObject) {
if (token == null) {
return returnedObject;
} else {
this.finallyInvocation(token);
if (this.afterInvocationManager != null) {
try {
returnedObject = this.afterInvocationManager.decide(token.getSecurityContext().getAuthentication(), token.getSecureObject(), token.getAttributes(), returnedObject);
} catch (AccessDeniedException var4) {
this.publishEvent(new AuthorizationFailureEvent(token.getSecureObject(), token.getAttributes(), token.getSecurityContext().getAuthentication(), var4));
throw var4;
}
}
return returnedObject;
}
}
