缘起
标准的RABC, 权限需要支持动态配置，spring security默认是在代码里约定好权限，真实的业务场景通常需要可以支持动态配置角色访问权限，即在运行时去配置url对应的访问角色。
基于spring security，如何实现这个需求呢？
最简单的方法就是自定义一个Filter去完成权限判断，但这脱离了spring security框架，如何基于spring security优雅的实现呢？
spring security 授权回顾
spring security 通过FilterChainProxy作为注册到web的filter，FilterChainProxy里面一次包含了内置的多个过滤器，我们首先需要了解spring security内置的各种filter：
| Alias | Filter Class | Namespace Element or Attribute |
|---|---|---|
| CHANNEL_FILTER | ChannelProcessingFilter | http/intercept-url@requires-channel |
| SECURITY_CONTEXT_FILTER | SecurityContextPersistenceFilter | http |
| CONCURRENT_SESSION_FILTER | ConcurrentSessionFilter | session-management/concurrency-control |
| HEADERS_FILTER | HeaderWriterFilter | http/headers |
| CSRF_FILTER | CsrfFilter | http/csrf |
| LOGOUT_FILTER | LogoutFilter | http/logout |
| X509_FILTER | X509AuthenticationFilter | http/x509 |
| PRE_AUTH_FILTER | AbstractPreAuthenticatedProcessingFilter Subclasses | N/A |
| CAS_FILTER | CasAuthenticationFilter | N/A |
| FORM_LOGIN_FILTER | UsernamePasswordAuthenticationFilter | http/form-login |
| BASIC_AUTH_FILTER | BasicAuthenticationFilter | http/http-basic |
| SERVLET_API_SUPPORT_FILTER | SecurityContextHolderAwareRequestFilter | http/@servlet-api-provision |
| JAAS_API_SUPPORT_FILTER | JaasApiIntegrationFilter | http/@jaas-api-provision |
| REMEMBER_ME_FILTER | RememberMeAuthenticationFilter | http/remember-me |
| ANONYMOUS_FILTER | AnonymousAuthenticationFilter | http/anonymous |
| SESSION_MANAGEMENT_FILTER | SessionManagementFilter | session-management |
| EXCEPTION_TRANSLATION_FILTER | ExceptionTranslationFilter | http |
| FILTER_SECURITY_INTERCEPTOR | FilterSecurityInterceptor | http |
| SWITCH_USER_FILTER | SwitchUserFilter | N/A |
最重要的是FilterSecurityInterceptor，该过滤器实现了主要的鉴权逻辑，最核心的代码在这里：
protected InterceptorStatusToken beforeInvocation(Object object) {
// 获取访问URL所需权限
Collection<ConfigAttribute> attributes = this.obtainSecurityMetadataSource()
.getAttributes(object);
Authentication authenticated = authenticateIfRequired();
// 通过accessDecisionManager鉴权
try {
this.accessDecisionManager.decide(authenticated, object, attributes);
}
catch (AccessDeniedException accessDeniedException) {
publishEvent(new AuthorizationFailureEvent(object, attributes, authenticated,
accessDeniedException));
throw accessDeniedException;
}
if (debug) {
logger.debug("Authorization successful");
}
if (publishAuthorizationSuccess) {
publishEvent(new AuthorizedEvent(object, attributes, authenticated));
}
// Attempt to run as a different user
Authentication runAs = this.runAsManager.buildRunAs(authenticated, object,
attributes);
if (runAs == null) {
if (debug) {
logger.debug("RunAsManager did not change Authentication object");
}
// no further work post-invocation
return new InterceptorStatusToken(SecurityContextHolder.getContext(), false,
attributes, object);
}
else {
if (debug) {
logger.debug("Switching to RunAs Authentication: " + runAs);
}
SecurityContext origCtx = SecurityContextHolder.getContext();
SecurityContextHolder.setContext(SecurityContextHolder.createEmptyContext());
SecurityContextHolder.getContext().setAuthentication(runAs);
// need to revert to token.Authenticated post-invocation
return new InterceptorStatusToken(origCtx, true, attributes, object);
}
}
从上面可以看出，要实现动态鉴权，可以从两方面着手：
下面来看分别如何实现。
自定义AccessDecisionManager
官方的三个AccessDecisionManager都是基于AccessDecisionVoter来实现权限认证的，因此我们只需要自定义一个AccessDecisionVoter就可以了。
自定义主要是实现AccessDecisionVoter接口，我们可以仿照官方的RoleVoter实现一个：
public class RoleBasedVoter implements AccessDecisionVoter<Object> {
@Override
public boolean supports(ConfigAttribute attribute) {
return true;
}
@Override
public int vote(Authentication authentication, Object object, Collection<ConfigAttribute> attributes) {
if(authentication == null) {
return ACCESS_DENIED;
}
int result = ACCESS_ABSTAIN;
Collection<? extends GrantedAuthority> authorities = extractAuthorities(authentication);
for (ConfigAttribute attribute : attributes) {
if(attribute.getAttribute()==null){
continue;
}
if (this.supports(attribute)) {
result = ACCESS_DENIED;
// Attempt to find a matching granted authority
for (GrantedAuthority authority : authorities) {
if (attribute.getAttribute().equals(authority.getAuthority())) {
return ACCESS_GRANTED;
}
}
}
}
return result;
}
Collection<? extends GrantedAuthority> extractAuthorities(
Authentication authentication) {
return authentication.getAuthorities();
}
@Override
public boolean supports(Class clazz) {
return true;
}
}
如何加入动态权限呢？
vote(Authentication authentication, Object object, Collection<ConfigAttribute> attributes)里的Object object的类型是FilterInvocation，可以通过getRequestUrl获取当前请求的URL:
FilterInvocation fi = (FilterInvocation) object; String url = fi.getRequestUrl();
因此这里扩展空间就大了，可以从DB动态加载，然后判断URL的ConfigAttribute就可以了。
如何使用这个RoleBasedVoter呢？在configure里使用accessDecisionManager方法自定义，我们还是使用官方的UnanimousBased，然后将自定义的RoleBasedVoter加入即可。
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true)
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.addFilterBefore(corsFilter, UsernamePasswordAuthenticationFilter.class)
.exceptionHandling()
.authenticationEntryPoint(problemSupport)
.accessDeniedHandler(problemSupport)
.and()
.csrf()
.disable()
.headers()
.frameOptions()
.disable()
.and()
.sessionManagement()
.sessionCreationPolicy(SessionCreationPolicy.STATELESS)
.and()
.authorizeRequests()
// 自定义accessDecisionManager
.accessDecisionManager(accessDecisionManager())
.and()
.apply(securityConfigurerAdapter());
}
@Bean
public AccessDecisionManager accessDecisionManager() {
List<AccessDecisionVoter<? extends Object>> decisionVoters
= Arrays.asList(
new WebExpressionVoter(),
// new RoleVoter(),
new RoleBasedVoter(),
new AuthenticatedVoter());
return new UnanimousBased(decisionVoters);
}
自定义SecurityMetadataSource
自定义FilterInvocationSecurityMetadataSource只要实现接口即可，在接口里从DB动态加载规则。
为了复用代码里的定义，我们可以将代码里生成的SecurityMetadataSource带上，在构造函数里传入默认的FilterInvocationSecurityMetadataSource。
public class AppFilterInvocationSecurityMetadataSource implements org.springframework.security.web.access.intercept.FilterInvocationSecurityMetadataSource {
private FilterInvocationSecurityMetadataSource superMetadataSource;
@Override
public Collection<ConfigAttribute> getAllConfigAttributes() {
return null;
}
public AppFilterInvocationSecurityMetadataSource(FilterInvocationSecurityMetadataSource expressionBasedFilterInvocationSecurityMetadataSource){
this.superMetadataSource = expressionBasedFilterInvocationSecurityMetadataSource;
// TODO 从数据库加载权限配置
}
private final AntPathMatcher antPathMatcher = new AntPathMatcher();
// 这里的需要从DB加载
private final Map<String,String> urlRoleMap = new HashMap<String,String>(){{
put("/open/**","ROLE_ANONYMOUS");
put("/health","ROLE_ANONYMOUS");
put("/restart","ROLE_ADMIN");
put("/demo","ROLE_USER");
}};
@Override
public Collection<ConfigAttribute> getAttributes(Object object) throws IllegalArgumentException {
FilterInvocation fi = (FilterInvocation) object;
String url = fi.getRequestUrl();
for(Map.Entry<String,String> entry:urlRoleMap.entrySet()){
if(antPathMatcher.match(entry.getKey(),url)){
return SecurityConfig.createList(entry.getValue());
}
}
// 返回代码定义的默认配置
return superMetadataSource.getAttributes(object);
}
@Override
public boolean supports(Class<?> clazz) {
return FilterInvocation.class.isAssignableFrom(clazz);
}
}
怎么使用？和accessDecisionManager不一样，ExpressionUrlAuthorizationConfigurer 并没有提供set方法设置FilterSecurityInterceptor的FilterInvocationSecurityMetadataSource，how to do?
发现一个扩展方法withObjectPostProcessor，通过该方法自定义一个处理FilterSecurityInterceptor类型的ObjectPostProcessor就可以修改FilterSecurityInterceptor。
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true)
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.addFilterBefore(corsFilter, UsernamePasswordAuthenticationFilter.class)
.exceptionHandling()
.authenticationEntryPoint(problemSupport)
.accessDeniedHandler(problemSupport)
.and()
.csrf()
.disable()
.headers()
.frameOptions()
.disable()
.and()
.sessionManagement()
.sessionCreationPolicy(SessionCreationPolicy.STATELESS)
.and()
.authorizeRequests()
// 自定义FilterInvocationSecurityMetadataSource
.withObjectPostProcessor(new ObjectPostProcessor<FilterSecurityInterceptor>() {
@Override
public <O extends FilterSecurityInterceptor> O postProcess(
O fsi) {
fsi.setSecurityMetadataSource(mySecurityMetadataSource(fsi.getSecurityMetadataSource()));
return fsi;
}
})
.and()
.apply(securityConfigurerAdapter());
}
@Bean
public AppFilterInvocationSecurityMetadataSource mySecurityMetadataSource(FilterInvocationSecurityMetadataSource filterInvocationSecurityMetadataSource) {
AppFilterInvocationSecurityMetadataSource securityMetadataSource = new AppFilterInvocationSecurityMetadataSource(filterInvocationSecurityMetadataSource);
return securityMetadataSource;
}
小结
本文介绍了两种基于spring security实现动态权限的方法，一是自定义accessDecisionManager，二是自定义FilterInvocationSecurityMetadataSource。实际项目里可以根据需要灵活选择。
延伸阅读:
Spring Security 架构与源码分析
总结
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