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绕过ObRegisterCallbacks注册的回调
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发表于: 2018-11-21 22:00
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其实我感觉这个东西挺鸡肋的，只是雕虫小技，大佬们笑笑就好。
如有错误，请大佬们指出。
测试环境：win7 x64
这里以ObjectType类型为PsProcessType的PreCallback为例子。
先自己注册一个回调，下个断点看看是什么在调用我们注册的回调。
查看栈回溯得到关键函数ObpCallPreOperationCallbacks，ida上看有三个参数，网上搜了一圈只确定了前两个参数。
signed __int64 __fastcall ObpCallPreOperationCallbacks(POBJECT_TYPE pObjectType, POB_PRE_OPERATION_INFORMATION OperationInformation, _QWORD *a3);
ida f5如下（做了一点重命名）
signed __int64 __fastcall ObpCallPreOperationCallbacks(POBJECT_TYPE pObjectType, POB_PRE_OPERATION_INFORMATION pOperationInformation, _QWORD *a3)
{
struct _KTHREAD *v3; // rax
_QWORD *v4; // rbp
POB_PRE_OPERATION_INFORMATION v_pOperationInformation; // r12
POBJECT_TYPE v6; // rsi
_QWORD *v7; // r13
_OB_CALLBACK *pCallbackList; // r15
signed __int64 v10; // rdx
void (__fastcall *PreOperationCallback)(_QWORD, POB_PRE_OPERATION_INFORMATION); // r8
__int64 v12; // r9
struct _KTHREAD *v13; // r11
signed __int64 v16; // rtt
signed __int64 v17; // rax
signed __int64 v18; // rcx
volatile signed __int64 v19; // rtt
struct _KTHREAD *v20; // rax
bool v21; // zf
signed __int64 v22; // rax
unsigned __int64 v23; // rtt
_QWORD *v24; // rax
_QWORD *v25; // rcx
_KTHREAD *v26; // rax
signed __int64 v27; // rax
unsigned __int64 v28; // rcx
bool v29; // cf
signed __int64 v30; // rcx
volatile signed __int64 v31; // rtt
struct _KTHREAD *v32; // rax
signed __int64 v33; // rtt
__int64 v34; // rdx
__int64 v35; // rcx
__int64 v36; // r8
__int64 v37; // r9
struct _KTHREAD *v38; // r11
signed __int64 v41; // rtt
int v42; // er11
__int64 v43; // rcx
PVOID v44; // rcx
int Dst; // [rsp+20h] [rbp-58h]
ULONG v46; // [rsp+24h] [rbp-54h]
PVOID v47; // [rsp+28h] [rbp-50h]
__int64 v48; // [rsp+30h] [rbp-48h]
int v49; // [rsp+40h] [rbp-38h]
v3 = KeGetCurrentThread();
v4 = a3;
--v3->KernelApcDisable;
v_pOperationInformation = pOperationInformation;
v6 = pObjectType;
v7 = 0i64;
_RDI = 0i64;
pCallbackList = &pObjectType->CallbackList; // 获得Object的CallbackList
ObfReferenceObject(pOperationInformation->Object);
v13 = KeGetCurrentThread();
--v13->SpecialApcDisable;
_RSI = &v6->TypeLock;
if ( _InterlockedCompareExchange(_RSI, 17i64, 0i64) )
ExfAcquirePushLockShared(_RSI);
for ( _RBX = pCallbackList->ListEntry.Flink; ; _RBX = _RBX->ListEntry.Flink )
{
if ( _RBX == pCallbackList ) // 判断CallbackList是否遍历完毕
{
__asm { prefetchw byte ptr [rsi] }
v27 = *_RSI;
v28 = *_RSI & 0xFFFFFFFFFFFFFFF0ui64;
v29 = v28 < 0x10;
v21 = v28 == 16;
v30 = *_RSI - 16;
if ( v29 || v21 )
v30 = 0i64;
if ( v27 & 2 || (v31 = *_RSI, v31 != _InterlockedCompareExchange(_RSI, v30, v27)) )
ExfReleasePushLock(_RSI);
v32 = KeGetCurrentThread();
v21 = v32->SpecialApcDisable++ == -1;
if ( v21 && v32->ApcState.ApcListHead[0].Flink != &v32->80 )
KiCheckForKernelApcDelivery(v30, v10, PreOperationCallback, v12);
if ( _RDI )
{
__asm { prefetchw byte ptr [rdi] }
v33 = *_RDI & 0xFFFFFFFFFFFFFFFEui64;
if ( v33 != _InterlockedCompareExchange(_RDI, v33 - 2, v33) )
ExfReleaseRundownProtection(_RDI);
}
if ( *v4 == v4 )
{
ObfDereferenceObject(v_pOperationInformation->Object);
v38 = KeGetCurrentThread();
v21 = v38->KernelApcDisable++ == -1;
if ( v21 && v38->ApcState.ApcListHead[0].Flink != &v38->80 && !v38->SpecialApcDisable )
KiCheckForKernelApcDelivery(v35, v34, v36, v37);
}
return 0i64;
}
if ( _RBX->Unknown1 & 0x100000000i64 )
{
if ( _RBX->Unknown1 & v_pOperationInformation->Operation )
{
__asm { prefetchw byte ptr [rbx+38h] }
v16 = _RBX->RundownProtect.Count & 0xFFFFFFFFFFFFFFFEui64;
if ( v16 == _InterlockedCompareExchange(&_RBX->RundownProtect, v16 + 2, v16)
|| ExfAcquireRundownProtection(&_RBX->RundownProtect) )
{
break;
}
}
}
LABEL_31:
;
}
__asm { prefetchw byte ptr [rsi] }
v17 = *_RSI;
if ( (*_RSI & 0xFFFFFFFFFFFFFFF0ui64) <= 0x10 )
v18 = 0i64;
else
v18 = v17 - 16;
if ( v17 & 2 || (v19 = *_RSI, v19 != _InterlockedCompareExchange(_RSI, v18, v17)) )
ExfReleasePushLock(_RSI);
v20 = KeGetCurrentThread();
v21 = v20->SpecialApcDisable++ == -1;
if ( v21 && v20->ApcState.ApcListHead[0].Flink != &v20->80 )
KiCheckForKernelApcDelivery(1i64, v10, PreOperationCallback, v12);
if ( _RDI )
{
__asm { prefetchw byte ptr [rdi] }
v22 = *_RDI & 0xFFFFFFFFFFFFFFFEui64;
v10 = v22 - 2;
v23 = *_RDI & 0xFFFFFFFFFFFFFFFEui64;
if ( v23 != _InterlockedCompareExchange(_RDI, v22 - 2, v22) )
ExfReleaseRundownProtection(_RDI);
_RDI = 0i64;
}
if ( !_RBX->PostCall )
{
LABEL_24:
PreOperationCallback = _RBX->PreCall;
if ( PreOperationCallback )
{
PreOperationCallback(*(_RBX->ObHandle + 8), v_pOperationInformation);// 调用PreOperationCallback
if ( _RBX->PostCall )
v7[3] = v_pOperationInformation->CallContext;
else
_RDI = &_RBX->RundownProtect;
v_pOperationInformation->CallContext = 0i64;
}
v26 = KeGetCurrentThread();
--v26->SpecialApcDisable;
if ( _InterlockedCompareExchange(_RSI, 17i64, 0i64) )
ExfAcquirePushLockShared(_RSI);
goto LABEL_31;
}
v24 = ExAllocatePoolWithTag(PagedPool, 0x20u, 0x6C46624Fu);
v7 = v24;
if ( v24 )
{
v24[3] = 0i64;
v24[2] = _RBX;
v25 = v4[1];
v24[1] = v25;
*v24 = v4;
*v25 = v24;
v4[1] = v24;
goto LABEL_24;
}
_RCX = &_RBX->RundownProtect;
__asm { prefetchw byte ptr [rcx] }
v41 = _RBX->RundownProtect.Count & 0xFFFFFFFFFFFFFFFEui64;
if ( v41 != _InterlockedCompareExchange(&_RBX->RundownProtect, v41 - 2, v41) )
ExfReleaseRundownProtection(_RCX);
if ( *v4 != v4 )
{
memset(&Dst, 0, 0x30u);
v42 = v_pOperationInformation->Operation;
v46 = v_pOperationInformation->Flags;
v43 = v_pOperationInformation->ObjectType;
Dst = v42;
v48 = v43;
v44 = v_pOperationInformation->Object;
v49 = 0xC000009A;
v47 = v44;
ObfReferenceObject(v44);
ObpCallPostOperationCallbacks(&Dst, v4);
}
return 0xC000009Ai64;
}
虽然这个f5问题很大，但是大致可以看出来ObpCallPreOperationCallbacks是通过循环遍历_OBJECT_TYPE里的CallbackList来调用注册的回调的。
TA教程里提供的有关CallbackList的结构如下，里面的ListEntry就是CallbackList。
typedef struct _OB_CALLBACK
{
LIST_ENTRY ListEntry;
ULONG64 Unknown;
ULONG64 ObHandle;
ULONG64 ObjTypeAddr;
ULONG64 PreCall;
ULONG64 PostCall;
} OB_CALLBACK, *POB_CALLBACK;
但是通过阅读f5的函数之后，我发现TA提供的结构并不完整，现补充一下。
typedef struct _OB_CALLBACK
{
LIST_ENTRY ListEntry;
ULONG64 Unknown;
ULONG64 ObHandle;
ULONG64 ObjTypeAddr;
ULONG64 PreCall;
ULONG64 PostCall;
EX_RUNDOWN_REF RundownProtect;
} OB_CALLBACK, *POB_CALLBACK;
有关RundownProtect可以看https://bbs.pediy.com/thread-173763.htm
这个补充的成员在后面绕过的时候会用到。
现在看看有关循环的部分
for ( _RBX = pCallbackList->ListEntry.Flink; ; _RBX = _RBX->ListEntry.Flink )
可以发现ObpCallPreOperationCallbacks通过RBX来存储当前的CallbackList节点，我寻思着能不能通过在自己注册的回调里面改变这个RBX来跳过其他的回调，于是我做了一个实验。
先写两个回调
回调1
OB_PREOP_CALLBACK_STATUS PreCallbackProcess(
PVOID RegistrationContext,
POB_PRE_OPERATION_INFORMATION OperationInformation
)
{
DbgPrint("我没被拦截\n");
return OB_PREOP_SUCCESS;
}
回调2（因为要操作RBX 想了想就用汇编来写了，代码有点渣，请见谅）
DbgPrint proto
ExAcquireRundownProtection proto
ExReleaseRundownProtection proto
.data
EXTERN PsProcessType:QWORD
str1 db '我开始拦截了',0Ah,0
.code
PreCallbackProcess2 proc
sub rsp,64h
lea rcx,str1
call DbgPrint
mov rax,rbx
lea rcx,[rax+38h]
call ExReleaseRundownProtection ;减少原本回调引用计数
mov rax,PsProcessType
mov rax,[rax]
mov rax,[rax+0c8h] ;CallbackList的最后一个节点
mov rbx,rax ;提前结束循环
lea rcx,[rax+38h]
call ExAcquireRundownProtection ;增加修改后回调的引用计数
xor rax,rax
add rsp,64h
ret
PreCallbackProcess2 endp
end
这里需要用到ExAcquireRundownProtection和ExReleaseRundownProtection是因为ObpCallPreOperationCallbacks里有维护每个回调的RundownProtect成员，如果我们通过修改RBX来跳过其他回调的话，就需要自己动手维护这个成员，否则在卸载回调的时候会出大问题。
然后通过ObRegisterCallbacks来注册这两个回调，因为回调的顺序是根据Altitude来确定的，所以PreCallbackProcess2的高度要比PreCallbackProcess高，否则将起不到绕过其他回调的效果。
载入驱动后用DebugView看看
可以看到PreCallbackProcess并没有执行，证明可以成功绕过。
后来我在win10 x64也测试过了，暂时没发现啥大问题。
然而一通操作下来我发现用处似乎不大，但应该比直接ObUnRegisterCallbacks好一点，大家看着乐一乐就好。
[注意]传递专业知识、拓宽行业人脉——看雪讲师团队等你加入！
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环境是win7 nt!_OBJECT_TYPE +0x000 TypeList : _LIST_ENTRY +0x010 Name : _UNICODE_STRING +0x020 DefaultObject : Ptr64 Void +0x028 Index : UChar +0x02c TotalNumberOfObjects : Uint4B +0x030 TotalNumberOfHandles : Uint4B +0x034 HighWaterNumberOfObjects : Uint4B +0x038 HighWaterNumberOfHandles : Uint4B +0x040 TypeInfo : _OBJECT_TYPE_INITIALIZER +0x0b0 TypeLock : _EX_PUSH_LOCK +0x0b8 Key : Uint4B +0x0c0 CallbackList : _LIST_ENTRY |
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这个问题我也想过，我看了一下win7的一个版本和win10的一个版本，用的都是rbx。 我寻思着可能微软就基本没动过这边的代码 |
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