Spring Security基于路径的动态权限控制

首先我们需要创建一个过滤器，用于实现动态权限控制，这里需要注意的是doFilter方法，对于OPTIONS请求直接放行，否则前端调用会出现跨域问题。对于配置在IgnoreUrlsConfig中的白名单路径我也需要直接放行，所有的鉴权操作都会在super.beforeInvocation(fi)中进行。

/**
 * 动态权限过滤器，用于实现基于路径的动态权限过滤
 */
public class DynamicSecurityFilter extends AbstractSecurityInterceptor implements Filter {

    @Autowired
    private DynamicSecurityMetadataSource dynamicSecurityMetadataSource;
    @Autowired
    private IgnoreUrlsConfig ignoreUrlsConfig;

    @Autowired
    public void setMyAccessDecisionManager(DynamicAccessDecisionManager dynamicAccessDecisionManager) {
        super.setAccessDecisionManager(dynamicAccessDecisionManager);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        FilterInvocation fi = new FilterInvocation(servletRequest, servletResponse, filterChain);
        //OPTIONS请求直接放行
        if(request.getMethod().equals(HttpMethod.OPTIONS.toString())){
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
            return;
        }
        //白名单请求直接放行
        PathMatcher pathMatcher = new AntPathMatcher();
        for (String path : ignoreUrlsConfig.getUrls()) {
            if(pathMatcher.match(path,request.getRequestURI())){
                fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
                return;
            }
        }
        //此处会调用AccessDecisionManager中的decide方法进行鉴权操作
        InterceptorStatusToken token = super.beforeInvocation(fi);
        try {
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
        } finally {
            super.afterInvocation(token, null);
        }
    }

    @Override
    public void destroy() {
    }

    @Override
    public Class<?> getSecureObjectClass() {
        return FilterInvocation.class;
    }

    @Override
    public SecurityMetadataSource obtainSecurityMetadataSource() {
        return dynamicSecurityMetadataSource;
    }

}

在DynamicSecurityFilter中调用super.beforeInvocation(fi)方法时会调用AccessDecisionManager中的decide方法用于鉴权操作，而decide方法中的configAttributes参数会通过SecurityMetadataSource中的getAttributes方法来获取，configAttributes其实就是配置好的访问当前接口所需要的权限，下面是简化版的beforeInvocation源码。
接下来我们就需要创建一个类来继承AccessDecisionManager，通过decide方法对访问接口所需权限和用户拥有的权限进行匹配，匹配则放行；

/**
 * 动态权限决策管理器，用于判断用户是否有访问权限
 * Created by macro on 2020/2/7.
 */
public class DynamicAccessDecisionManager implements AccessDecisionManager {

    @Override
    public void decide(Authentication authentication, Object object,
                       Collection<ConfigAttribute> configAttributes) throws AccessDeniedException, InsufficientAuthenticationException {
        // 当接口未被配置资源时直接放行
        if (CollUtil.isEmpty(configAttributes)) {
            return;
        }
        Iterator<ConfigAttribute> iterator = configAttributes.iterator();
        while (iterator.hasNext()) {
            ConfigAttribute configAttribute = iterator.next();
            //将访问所需资源或用户拥有资源进行比对
            String needAuthority = configAttribute.getAttribute();
            for (GrantedAuthority grantedAuthority : authentication.getAuthorities()) {
                if (needAuthority.trim().equals(grantedAuthority.getAuthority())) {
                    return;
                }
            }
        }
        throw new AccessDeniedException("抱歉，您没有访问权限");
    }

    @Override
    public boolean supports(ConfigAttribute configAttribute) {
        return true;
    }

    @Override
    public boolean supports(Class<?> aClass) {
        return true;
    }

}

由于上面的decide方法中的configAttributes属性是从FilterInvocationSecurityMetadataSource的getAttributes方法中获取的，我们还需创建一个类继承它，getAttributes方法可用于获取访问当前路径所需权限值。

/**
 * 动态权限数据源，用于获取动态权限规则
 */
public class DynamicSecurityMetadataSource implements FilterInvocationSecurityMetadataSource {

    private static Map<String, ConfigAttribute> configAttributeMap = null;
    @Autowired
    private DynamicSecurityService dynamicSecurityService;

    @PostConstruct
    public void loadDataSource() {
        configAttributeMap = dynamicSecurityService.loadDataSource();
    }

    public void clearDataSource() {
        configAttributeMap.clear();
        configAttributeMap = null;
    }

    @Override
    public Collection<ConfigAttribute> getAttributes(Object o) throws IllegalArgumentException {
        if (configAttributeMap == null) this.loadDataSource();
        List<ConfigAttribute>  configAttributes = new ArrayList<>();
        //获取当前访问的路径
        String url = ((FilterInvocation) o).getRequestUrl();
        String path = URLUtil.getPath(url);
        PathMatcher pathMatcher = new AntPathMatcher();
        Iterator<String> iterator = configAttributeMap.keySet().iterator();
        //获取访问该路径所需资源
        while (iterator.hasNext()) {
            String pattern = iterator.next();
            if (pathMatcher.match(pattern, path)) {
                configAttributes.add(configAttributeMap.get(pattern));
            }
        }
        // 未设置操作请求权限，返回空集合
        return configAttributes;
    }

    @Override
    public Collection<ConfigAttribute> getAllConfigAttributes() {
        return null;
    }

    @Override
    public boolean supports(Class<?> aClass) {
        return true;
    }

}

所有路径对应的权限值数据来自于自定义的DynamicSecurityService；

/**
 * 动态权限相关业务类
 */
public interface DynamicSecurityService {
    /**
     * 加载资源ANT通配符和资源对应MAP
     */
    Map<String, ConfigAttribute> loadDataSource();
}

由于我们的后台资源规则被缓存在了一个Map对象之中，所以当后台资源发生变化时，我们需要清空缓存的数据，然后下次查询时就会被重新加载进来。这里我们需要修改UmsResourceController类，注入DynamicSecurityMetadataSource，当修改后台资源时，需要调用clearDataSource方法来清空缓存的数据。

/**
 * 后台资源管理Controller
 */
@Controller
@Api(tags = "UmsResourceController", description = "后台资源管理")
@RequestMapping("/resource")
public class UmsResourceController {

    @Autowired
    private UmsResourceService resourceService;
    @Autowired
    private DynamicSecurityMetadataSource dynamicSecurityMetadataSource;

    @ApiOperation("添加后台资源")
    @RequestMapping(value = "/create", method = RequestMethod.POST)
    @ResponseBody
    public CommonResult create(@RequestBody UmsResource umsResource) {
        int count = resourceService.create(umsResource);
        dynamicSecurityMetadataSource.clearDataSource();
        if (count > 0) {
            return CommonResult.success(count);
        } else {
            return CommonResult.failed();
        }
    }
 }

接下来我们需要修改Spring Security的配置类SecurityConfig，当有动态权限业务类时在FilterSecurityInterceptor过滤器前添加我们的动态权限过滤器。这里在创建动态权限相关对象时，还使用了@ConditionalOnBean这个注解，当没有动态权限业务类时就不会创建动态权限相关对象，实现了有动态权限控制和没有这两种情况的兼容。

/**
 * 对SpringSecurity的配置的扩展，支持自定义白名单资源路径和查询用户逻辑
 * Created by macro on 2019/11/5.
 */
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired(required = false)
    private DynamicSecurityService dynamicSecurityService;

    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception {
        ExpressionUrlAuthorizationConfigurer<HttpSecurity>.ExpressionInterceptUrlRegistry registry = httpSecurity
                .authorizeRequests();
        //有动态权限配置时添加动态权限校验过滤器
        if(dynamicSecurityService!=null){
            registry.and().addFilterBefore(dynamicSecurityFilter(), FilterSecurityInterceptor.class);
        }
    }

    @ConditionalOnBean(name = "dynamicSecurityService")
    @Bean
    public DynamicAccessDecisionManager dynamicAccessDecisionManager() {
        return new DynamicAccessDecisionManager();
    }


    @ConditionalOnBean(name = "dynamicSecurityService")
    @Bean
    public DynamicSecurityFilter dynamicSecurityFilter() {
        return new DynamicSecurityFilter();
    }

    @ConditionalOnBean(name = "dynamicSecurityService")
    @Bean
    public DynamicSecurityMetadataSource dynamicSecurityMetadataSource() {
        return new DynamicSecurityMetadataSource();
    }

}

这里还有个问题需要提下，当前端跨域访问没有权限的接口时，会出现跨域问题，只需要在没有权限访问的处理类RestfulAccessDeniedHandler中添加允许跨域访问的响应头即可。

/**
 * 自定义返回结果：没有权限访问时
 */
public class RestfulAccessDeniedHandler implements AccessDeniedHandler{
    @Override
    public void handle(HttpServletRequest request,
                       HttpServletResponse response,
                       AccessDeniedException e) throws IOException, ServletException {
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Cache-Control","no-cache");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json");
        response.getWriter().println(JSONUtil.parse(CommonResult.forbidden(e.getMessage())));
        response.getWriter().flush();
    }
}

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