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NoirVisor

NoirVisor - The Grimoire Hypervisor solution for AMD64 Processors.

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Introduction

NoirVisor is a hardware-accelerated hypervisor (a.k.a VMM, Virtual Machine Monitor) with support to complex functions and purposes. It is designed to support processors based on x86 architecture with hardware-accelerated virtualization feature. For example, Intel processors supporting Intel VT-x or AMD processors supporting AMD-V meet the requirement. By design, NoirVisor determines the processor manufacturer and selects the function core.

Namesake: NoirVisor is named after the Grimoire Noir in NieR:Gestalt/Replicant.

Processor Requirement

Intel Processors based on Intel 64 and IA-32 Architecture, with support to Intel VT-x. Intel EPT is prefered, but not required.
AMD Processors based on AMD64 Architecture, with support to AMD-V. Nested Paging is prefered, but not required.
Other processors based on x86 architecture may be supported in future.
Currently, it is discovered that x86 processors produced by VIA, Zhaoxin and Hygon supports Hardware-Accelerated Virtualization Technology. In summary, certain facts are observed that:

• Processors produced by Intel Corporation may support Intel VT-x.
• Processors produced by Advanced Micro Devices Inc. may support AMD-V.
• Processors produced by VIA Technologies Inc. may support Intel VT-x.
• Processors produced by Shanghai Zhaoxin Semiconductor Co, Ltd. may support Intel VT-x.
• Processors produced by Tianjin Haiguang Advanced Technology Investment Co, Ltd. may support AMD-V.

Note that early Zhaoxin and VIA use Centaur as vendor.

Nested Virtualization

Algorithm regarding the Nested Virtualization was written in the readme files in both VT-Core and SVM-Core directories.
For Nested Intel VT-x Algorithm, visit here.
For Nested AMD-V Algorithm, visit here.

Nested AMD-V is now in debugging stage. NoirVisor currently can run a modified version of SimpleSvm as nested hypervisor where NPT is turned off.
Nested Intel VT-x is not supported yet.

Announcement to all contributors

NoirVisor is coded in the C programming language and the assembly since it is procedure-oriented designed.
Contributing Guidelines are available in repository. For details, see the markdown file in the root directory of repository.
DO NOT PROVIDE CODES WITH C++ WHICH INVOLVES THE NoirVisor Core IN YOUR PULL-REQUEST!

Rust

A new branch rust-dev is already available at GitHub.
When you switch branches, make sure to execute cleanup.bat script to clean up the compiler outputs.

Build

To build NoirVisor, using batch is essential.
Note that you should execute the build_prep.bat to make directories for first-time compilation.
Once NoirVisor is updated, it is recommended to execute cleanup.bat script before building.

If you use terminal, you may add /s option in order to bypass the pause command. For example:

cd build
.\compchk_win7x64.bat /s

Windows Driver

To build a kernel-mode driver on Windows, you should download and mount Enterprise Windows Driver Kit 11 (Visual Studio Build Tools 16.11.10 and 17.8.6) ISO file to T: and V: drives. I recommend using WinCDEmu to mount the ISO on system startup if you are looking for a free virtual ISO Drive.
Then run the provided batch file to build it. You might have to mount the ISO file manually everytime on your machine startup in that I failed to find a script that mount an ISO to a specific drive letter. If you use WinCDEmu, however, you may order the system to mount EWDK10 and specify its drive letter during startup.
You may download the EWDK11 (with VS Build Tools 16.11.10) from Microsoft: https://docs.microsoft.com/en-us/legal/windows/hardware/enterprise-wdk-license-2019-New
You may download the EWDK11 (with VS Build Tools 17.8.6) from Microsoft: https://docs.microsoft.com/en-us/legal/windows/hardware/enterprise-wdk-license-2022
Make sure you have downloaded the correct version. NoirVisor would continue updating. If not using correct version, you might fail to compile the latest version of NoirVisor.
Note that EWDK11 with VS Build Tools newer than 16 has removed import library for Windows 7.
Presets for Free/Release build are available. Please note that the compiled binary under Free build does not come along with a digital signature. You might have to sign it yourself.

EFI Application and Runtime Driver

Due to different EFI firmware implementation, most modern computer firmware does not support booting an EFI Runtime Driver directly. Therefore, it is necessary to build a separate EFI Application. In this way, modern computer firmware will boot, and the application can load runtime driver into memory.
To build a EFI Runtime Driver and Application, you should NASM and TianoCore EDK II. To install TianoCore EDK II, you may download latest release source code and extract to path C:\UefiDKII. Also, you should mount EWDK11 with VS Build Tools 17.8.6 to V: drive.
You may download NASM from its official website: https://www.nasm.us/pub/nasm/stable/win64/. Make sure you have added the directory to the PATH environment variable.
You may download EDK II from GitHub: https://github.com/tianocore/edk2/releases. Download the source code.
NoirVisor also use EDK II Libraries. However, they should be pre-compiled. Visit EDK-II-Library on GitHub in order to build them.

Disassembler

Project NoirVisor chooses Zydis as NoirVisor's disassembler engine. You should pre-compile Zydis as a static library. Visit the documents for disassembler for further details.
In that Zydis is included as a submodule, and because Zydis itself has a submodule, you must clone this repository recursively.

Python script

Since January 2024, NoirVisor can be built using Python script. The minimum version required for building NoirVisor is 3.9 by virtue of the typing syntax. In other words, building NoirVisor through Python script in Windows 7 is not supported. There is no pip package requirements for compilation.
First of all, in the root directory of this repository, execute the following command to compile the third-party libraries:

make /target disassembler /j
make /target snprintf /j

The first command will build the zydis disassembler engine.
The second command will build the snprintf library.

Then you can compile NoirVisor itself:

make /j

Python-based compilation is parallel. It will achieve a great performance in building NoirVisor.

Current implementation only supports building NoirVisor as Windows Driver.

See documentation for more information using python script to build NoirVisor.

Test

Windows Driver

There is a .NET Framework 4.0 based GUI loader available on GitHub now: https://github.com/Zero-Tang/NoirVisorLoader
If you are using operating systems older than Windows 8, you are supposed to manually install .NET Framework 4.0 or higher.
If you use the digital signature provided in NoirVisor's repository, then you should enable the test-signing on your machine.
You may enable Stealth SSDT Hook by setting up registry. Please note that since hooking is a very dangerous behavior, NoirVisor disables them on default.
Caveat: The stealth hook functionalities are deprecated in that I'm tired of doing this. They are disabled by default. Future updates of NoirVisor will rarely address issues from them. If you encountered issues from stealth hook features, expect no fixes will be applied. This project has no interest in fixing them.

reg add "HKLM\SOFTWARE\Zero-Tang\NoirVisor" /v "StealthMsrHook" /t REG_DWORD /d 1 /f

You may enable Stealth Inline Hook by setting up registry:

reg add "HKLM\SOFTWARE\Zero-Tang\NoirVisor" /v "StealthInlineHook" /t REG_DWORD /d 1 /f

You may set the values to 0, or remove the value key, in order to disable these features again.

You may load NoirVisor by using command-line or batch script:

reg add "HKLM\SOFTWARE\Zero-Tang\NoirVisor" /v "SubvertOnDriverLoad" /t REG_DWORD /d 1 /f
sc create NoirVisor type= kernel binPath= <Path to NoirVisor driver file>
sc start NoirVisor

You may unload NoirVisor by using command-line or batch script as well:

sc stop NoirVisor
sc delete NoirVisor
reg add "HKLM\SOFTWARE\Zero-Tang\NoirVisor" /v "SubvertOnDriverLoad" /t REG_DWORD /d 0 /f

The SubvertOnDriverLoad registry key value specifies whether the driver should subvert the system or not on the entry. This key value conflicts with NoirVisor Loader. You must delete or disable this key value in order to use NoirVisor Loader.

EFI Application and Runtime Driver

There are two methods to test NoirVisor.

Running on a physical machine

This method can also be used on VMware.
Use a USB flash stick and setup with GUID Partition Table (GPT). Construct a partition and format it info FAT32 file system. After you successfully build the image, you should see two images: bootx64.efi and NoirVisor.efi
Those two files are EFI Application and Runtime Driver respectively.
Copy EFI Application to \EFI\BOOT\bootx64.efi
Copy EFI Runtime Driver to \NoirVisor.efi
As the USB flash stick is ready, enter your firmware settings and set it prior to the operating system. Disable Secure Boot feature unless you can sign the executable.
NoirVisor has defined its own vendor GUID {2B1F2A1E-DBDF-44AC-DABCC7A130E2E71E}. Developments regarding Layered Hypervisor would require accessing NoirVisor's UEFI variables.

Running on a virtual machine

The point of this method is to build a virtual disk image.
You may use mtools in order to make a virtual disk image. The pre-built mtools executables are provided here. Put them into directories listed in PATH environment variable.

Build script for NoirVisor on UEFI includes above commands. Add NoirVisor-Uefi.img as a floppy image in your virtual machine.

Documents

This repository provides additional documents which help new developers to join development.

Detection of NoirVisor

As specified in AMD64 Architecture Programming Manual, CPUID.EAX=1.ECX[bit 31] indicates hypervisor presence. So NoirVisor will set this bit. For CPUID instruction, since AMD defines that function leaves 0x40000000-0x400000FF are reserved for hypervisor use, we will use them. Most hypervisors defines leaf 0x40000000 is used to identify hypervisor vendor. The string constructed by register sequence EBX-ECX-EDX is used to identify vendor of hypervisor. For example, VMware hypervisor vendor string is VMwareVMware. In NoirVisor, hypervisor vendor string is defined as NoirVisor ZT.

You may disable the detection for NoirVisor in Windows via setting up the registry.
Locate the registry key: HKLM\Software\Zero-Tang\NoirVisor. If this key does not exist then create it.
Edit the CpuidPresence Key Value to 0. Feel free to execute the following command if you find it less taxing to do:

reg add "HKLM\SOFTWARE\Zero-Tang\NoirVisor" /v "CpuidPresence" /t REG_DWORD /d 0 /f

NoirVisor as a Nested Hypervisor

If NoirVisor is subverting a system under a virtualized environment with exposed detection (e.g: VMware virtual machines with hypervisor.cpuid.v0 = TRUE configuration) as a Type-II hypervisor, the operating system may have already been using functionalities provided by the hypervisor. In this regard, NoirVisor should pass-through the access to hypervisor functionalities (e.g: cpuid instructions, accesses to Microsoft Synthetic MSRs, hypercalls, etc.)

TSC-Omission

Since the end of 2020, NoirVisor implemented a simple Time-Profiler Countermeasure. According to the half-year test, this technique is deemed unstable with multiprocessing systems. For example, TSC-omission may cause external hardwares to trigger drivers resetting themselves. Everything could be messed up: Timer, Graphics Card, NIC, etc. In a nutshell, system may go haywire.
By virtue of this unexpected and unpleasant side-effect, this feature is now obsolete. Codes addressing this feature are now removed.

Customizable VM

Customizable VM is the true explanation of "complex functions and purposes". As the project creator and director, Zero's true intention to create this project is for studying Hardware-Acclerated Virtualization Technology. Therefore, any features which is related to virtualization and which Zero has ideas to implement will be added in the project.
Customizable VM is the feature that Zero researches about Virtualization: to run an arbitrary guest, instead of to just subvert the host system. In a word, it is aimed to be a competitor of the Windows Hypervisor Platform (WHP).
For CVM Algorithm on AMD-V, visit here.
For CVM Algorithm on Intel VT-x, visit here.

APIs to invoke Customizable VMs are available in the NoirCvmApi repository. The documentation of the APIs is available in the wiki page.

NoirVisor Secure Virtualization

NSV (a.k.a NoirVisor Secure Virtualization) is a security extension to NoirVisor CVM. This extension is a crossover project with Columbia University's Operating Systems II course project. Read this document for further details.

NPIEP

NPIEP (a.k.a Non-Privileged Instruction Execution Prevention) is an important security feature in Microsoft Virtualization-based Security. As a hypervisor project in conformance to Microsoft Hv#1 interface, NoirVisor would provide this feature to the guest. This feature is similar to UMIP provided by later models of x86 processors. The differences are:

• NPIEP does not raise an exception even if the instruction is executed in user mode.
• NPIEP would prevent the guest from reading the real values of descriptor tables.
• NPIEP does not intercept smsw instruction, probably in that Intel VT-x does not support intercepting this instruction.

For further details of NPIEP, visit here.

Security Advisories

You should not report security vulnerabilities through the GitHub issue. You should read this document to check out the steps to report security vulnerability.

Supported Platforms

NoirVisor is designed to be cross-platform. It can be built to a kernel-mode component of an operating system, or even as a software with bootstrap running on bare-metal.
Currently, NoirVisor supports the Windows Operating System newer than or same as Windows XP, running as a kernel-mode driver.
Porting to Unified Extensible Firmware Interface (UEFI) is in progress.
If there is already a hypervisor running in the system, make sure it supports native virtualization nesting.

Development Status

Project NoirVisor has six future development plans:

• Develop Customizable VM engine for complex purposes.
• Develop Nested Virtualization.
• Develop IOMMU Core on AMD-Vi.
• Port NoirVisor to the Rust Programming Language.
• Port NoirVisor to Linux.
• Port NoirVisor to UEFI and corresponding layered hypervisor.

For more information, check out the NoirVisor 2020+ Project.

Publications

Here lists some informal publications (blogs) regarding hypervisor development:

• Extending the Tradition Hypervisor's Approach of System Call Hooking in the Post-2018 Windows Operating Systems: https://tangptr.com/?p=149
• MTRR Emulation: Beginner’s Common Mistake in EPT Setup: https://tangptr.com/?p=163
• Introduction to NoirVisor CVM: The Open-Source Alternative of the Windows Hypervisor Platform: https://tangptr.com/?p=173

Completed Features

• Minimal Microsoft Hv#1 Hypervisor Functionalities.
• Stealth SSDT Hook (NtOpenProcess Hook) on 64-bit Windows, both Intel VT-x and AMD-V. (Compatible with the KiErrata420Present mitigation and KVA Shadow mechanism.)
• Stealth Inline Hook (NtSetInformationFile Hook) on 64-bit Windows, both Intel VT-x/EPT and AMD-V/NPT.
• Non-Privileged Instruction Execution Prevention (NPIEP) on AMD-V.
• Customizable VM engine on AMD-V.
• Tagged Translation Lookaside Buffer by ASID/VPID feature.
• Critical Hypervisor Protection.
• Software-Level Code Integrity Enforcement.
• Hardware-Level Code Integrity Enforcement, both Intel EPT and AMD NPT.

License

This repository is under MIT license.

Code of Conduct

The Code of Conduct is added to NoirVisor Project since May.5th, 2019. Please follow the rules when contributing.