September 9, 2020
This post will be the first of a new series in which we will get deep into Windows Kernel Exploitation. I’ll be using HEVD (HackSys Extreme Vulnerable Driver) as the target and, just as we did with the Vulnserver series, there’s going to be a different articles on the ways to exploit it.
Before dealing with vulnerabilities, we must setup the lab environment
first. Kernel exploiting is different than application exploiting. When
you are attacking an application, if something goes wrong, you can
simply restart it. In kernel mode, you will likely get an infamous blue
screen of death
This post will guide you to setup a testing lab for kernel debugging on
a Windows 10 target machine and finally we will be able to install
HEVD driver that will be our kernel space victim.
Unlike common user-land applications, the Windows Kernel is commonly debugged remotely. This is because, as I mentioned earlier, when you mess with kernel memory, you’re likely making the OS unusable. For that, we will setup a testing environment with a target Windows OS system (the debuggee) and some tools in the debugger machine.
The following are the tools needed to setup the environment:
WinDBG. We’ll use the version that’s included in the Windows 10 SDK
WinDBG dark theme (optional): Because I like fancy debugging
Pykd: To run Python scripts on WinDBG. Download here.
Windbglib + Mona: Download here
Windows 10 1703 (Creators Update): For now, we’d only need the 32 bits version
A virtual machine player. I’ll be using VMWare Workstation Player.
HackSys Extreme Vulnerable Driver: Our target. We’ll be using the latest stable release (
HEVD v3.00to the date of this post).
OSR Driver Loader: To load
HEVDinto the OS. Download here
With all the requirements in place, we can start setting up our lab,
which will be composed of a debugger machine, that will be the host
machine from which we will run
WinDBG; and the debuggee machine, on
which we will install
HEVD that will be running as a virtual machine.
Setting up debugger
The first stage is to download and install the Windows 10 SDK. If you
want to install only WinDBG, you can choose only the
Debugging Tools for Windows option:
Once installed, if you search for
windbg on Windows, you should get
something like this:
WinDBG configuration provides a not so friendly UI.
However we can use a dark theme for
WinDBG (see the Pre-Requisites
section). To do that, just download the
dark.reg file and install it.
You will get a much friendly UI:
Next, we need to adjust the Windows symbols resolution. It is done by
creating a new environment variable
_NT_SYMBOL_PATH with the value
srv*https://msdl.microsoft.com/download/symbols, like this:
Now, we need to install our friend
mona. To do that, we need to grab
pykd.zip file located
That ZIP has two files. The
pykd.pyd file should be placed at
C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\winext. Now run
vcredist_x86.exe and follow the installing instructions.
To check if that worked, load an executable on
.load pykd.pyd and then
!py mona. You should see something like this:
With that, we have now debugger machine set.
Setting up the debuggee
Now it’s time to setup our target OS. The first thing is to launch a new virtual machine with a Windows 10 1703 (Creators Update) instance.
It’s recommended to disable Windows Update service to avoid messing with our lab results.
With the target machine up an running, it’s time to load
HEVD in the
system. This is done by copying the
HEVD.3.00.zip files to this target OS and uncompressed them. Then, we
OSR Driver Loader (run the one in the
WNET → i386 → FRE
Now browse for the
HEVD.sys file, click on
Register Service and then
To check if that went well, open a terminal and type
driverquery | findstr HEVD. You should see something like this:
Great! To ensure that the
HEVD driver is load every time, open a
terminal as administrator and run
> sc config HEVD start=system
Now we must connect our target OS with the debugger. You need to launch a new terminal windows as administrator:
And then you need to enable remote debugging by issuing the following command:
> bcdedit /dbgsettings NET HOSTIP:192.168.20.31 PORT:50000
You need to change the
HOSTIP param with the IP of the debugger
This will return a key that will be used for
WinDBG to expect for a
connection with that identifier.
In the debugger machine, setup
WinDBG to listen for a connection with
Now, we need to make Windows to start in
DEBUG mode and restart. To
that, we should issue the following command:
> bcdedit /debug ON > shutdown -r -t 0
The target OS will restart and the debugger machine should now get a connection from the target OS:
Great. Now break the execution (
Debug → Break) and type
load the debugging symbols:
To check if everything’s working,
x /f nt!Create*Process.
This will list all the functions in the
NT module that contain
Now, set a breakpoint in
nt!MmCreateProcessAddressSpace and resume
Great! But as we are going to debug
HEVD, we must add the debugging
symbols to our environment. If you look at the folder
HEVD.3.00\driver\vulnerable\x86 you can see several files, including
HEVD.sys driver file and
HEVD.pdb. The latter is the file
HEVD debugging symbols. To load it on our debugger,
follow this steps:
Create a folder called
HEVD.pdbfile in that directory.
lm m HEVDto check if the
HEVDmodule is loaded.
x HEVD!*to check if the symbols were successfully added.
With that, we can start debugging our target machine’s kernel space!:
In the next post, you can see a short reference of
WinDBG commands that we will be using during this process.
This post will help you to setup a working Windows Kernel debugging lab. In the next posts we will be dealing with some theory on Windows Kernel and will start exploiting HEVD.
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