[Obsolete] Secure Boot for Windows Virtual Machines on Proxmox, compiling from source

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IMPORTANT: With the release of Proxmox VE 7.0-13, secure boot functionality is now built in and this walkthrough is no longer required. I am leaving it here for historical reasons.

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Note: Any and all comments/improvements are welcomed.

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What is Secure Boot?

Secure Boot is a security standard that helps make sure that a device boots using trusted software. This feature and the underling hardware Trusted Platform Module (TPM) is also required by Windows to enable certain features such as Bit Locker disk encryption.

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Secure Boot and Windows 11

Whist this feature has been around since Microsoft Windows 8, it has gained a lot of coverage in the press because initially Microsoft stated that Microsoft Windows 11 would only install on machines that supported and had Secure Boot enabled. Currently it is unknown if Microsoft will eventually require Secure Boot for Windows 11.

It could be said that using Secure Boot with a Virtual Machines is pointless, however, certain corporate environments require features like Bit Locker to be enabled for a machine to be “compliant” and join their corporate network.

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Proxmox and Secure Boot

Proxmox 7.x does not currently support Secure Boot but there has been a significant amount of work done to enable it in the underlying QEMU open source machine emulation and virtualization technology.

This walkthrough leverages that work to provide an updated OVMF UEFI virtual machine bios and a Virtual TPM to support it.

This process is by no means integrated into the Proxmox web interface, virtual machines need to be started from the shell.

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Note: This guide is based on the excellent work by the following people, many thanks for all your hard work.

• vTPM and Secureboot capability in a Proxmox-KVM by zimsneexh
• Common EDK II Build Instructions for Linux
• Software emulation of a Trusted Platform Module by rayures
• libtpms & swtpm by Stefan Berger

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The build and install script

The installation script downloads source from Github, compiles a new version of OVMF with to provide the SecureBoot and TPM capability; compiles and installs both swtpm and libtpms for emulating a TPM2. All of this needs to be run as root.

#!/bin/bash

# check i am (g)root
if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi

# install dependent packages
apt update -y
apt install -y automake expect gnutls-bin libgnutls28-dev wget git gawk m4 socat fuse libfuse-dev checkinstall libgmp-dev libtool libglib2.0-dev libjson-glib-dev libnspr4-dev libnss3-dev libssl-dev libtasn1-6-dev net-tools libseccomp-dev python-setuptools python3-pip python3-distutils build-essential uuid-dev iasl gcc nasm 

# this one causes a problem - works without it anyways. Do we need it?
# apt install -y tpm-tools

# create directory
mkdir ~/vtpm
chmod ugoa+rwx -R ~/vtpm

# libtpms
git clone https://github.com/stefanberger/libtpms.git ~/vtpm/libtpms
cd ~/vtpm/libtpms
./bootstrap.sh
./configure  --with-openssl --with-tpm2 
make
checkinstall --install=yes
cp ~/vtpm/libtpms/*.deb ~/vtpm

# swtpm
git clone https://github.com/stefanberger/swtpm.git ~/vtpm/swtpm
cd ~/vtpm/swtpm
./autogen.sh
./configure  --prefix=/usr --with-openssl --with-tpm2
make
make install
checkinstall --install=yes
cp ~/vtpm/swtpm/*.deb ~/vtpm
ldconfig

# OVMF with Secureboot and TPM - compile
git clone https://github.com/tianocore/edk2 ~/vtpm/edk2
cd ~/vtpm/edk2
git submodule update --init
make -C BaseTools
. edksetup.sh
build -p OvmfPkg/OvmfPkgX64.dsc -b RELEASE -a X64 -t GCC5 -D TPM_ENABLE -D TPM_CONFIG_ENABLE -D SECURE_BOOT_ENABLE -D NETWORK_TLS_ENABLE
cp ~/vtpm/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd ~/vtpm

# download the launch script
cd ~/vtpm
wget https://raw.githubusercontent.com/garjones/gareth.com/master/vTPM-launch.sh
chmod +x vTPM-launch.sh

The script can be run in a couple of different ways – The following command downloads the script and pipes the output directly to the shell.

This is commonly thought of as a security concern and is not recommended without reading and fully understanding the contents of the script.

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/garjones/gareth.com/master/vTPM-install.sh)"

If you are uncomfortable with the above, the script can be downloaded from here – https://github.com/garjones/gareth.com/blob/main/vTPM-install.sh

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Running the Script

The script is as automated as possible and requires very little user input. However during the checkinstall phase of swtpm, a number of variables are not enumerated properly and I am yet to work out how to solve this – If anyone has any pointers please leave me a comment.

checkinstall 1.6.3, Copyright 2010 Felipe Eduardo Sanchez Diaz Duran
           This software is released under the GNU GPL.


The package documentation directory ./doc-pak does not exist. 
Should I create a default set of package docs?  [y]: 

Press [Enter] to create the default set of package docs.

Preparing package documentation...OK

Please write a description for the package.
End your description with an empty line or EOF.
>> 

Either enter a description or leave blank and Press [Enter][Enter]

*****************************************
**** Debian package creation selected ***
*****************************************

This package will be built according to these values: 

0 -  Maintainer: [ root@vtpm ]
1 -  Summary: [ TPM Emulator
Private libraries for swtpm TPM emulators
Include files for the TPM emulator's CUSE interface for usage by clients
Tools for the TPM emulator
Tools for creating a local CA based on a pkcs11 device ]
2 -  Name:    [ swtpm ]
3 -  Version: [ 0.7.0 ]
4 -  Release: [ 1%{?dist} ]
5 -  License: [ GPL ]
6 -  Group:   [ checkinstall ]
7 -  Architecture: [ amd64 ]
8 -  Source location: [ swtpm ]
9 -  Alternate source location: [  ]
10 - Requires: [ trousers >= 0.3.9 bash gnutls-utils
tpm2-pkcs11 tpm2-pkcs11-tools tpm2-tools tpm2-abrmd
expect gnutls-utils trousers >= 0.3.9 ]
11 - Recommends: [  ]
12 - Suggests: [  ]
13 - Provides: [ swtpm ]
14 - Conflicts: [  ]
15 - Replaces: [  ]

Enter a number to change any of them or press ENTER to continue: 

The Release number contains illegal characters and needs to be cleared:

Note: This is a really bad idea but makes it work.

4 [ENTER] [ENTER]

Requires contains illegal characters. This is not a good practice, but clearing it solves the problem:

Note: This is a really, really bad idea but makes it work.

10 [ENTER] [ENTER]

Building can now continue ..

[ENTER]

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Verifying success

On completion if everything has gone correctly the folder /root/vTPM will contain the following files:

• libtpms_xxx_amd64.deb – Debian package for libtpms
• swtpm_xxx_amd64.deb – Debian package for swtpm
• OVMF.fd – Custom OVMF UEFI Bios
• vTPM-launch.sh – Custom script to launch a VM with SecureBoot

At this point the only files that are needed are OVMF.fd and vTPM-launch.sh, everything else can be deleted if you want to.

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Starting your VM

The launch script creates a temporary copy of your Virtual machine configuration and modifies it to use the new custom OVMF bios and adds entries to connect to the virtual TPM. It then starts the swtpm socket service and finally launches the virtual machine. The socket service runs in the background until the virtual machine is stopped.

#!/bin/bash

# launch script for Proxmox VM with a virtual TPM

# check for VMID
re='^[0-9]+$'
if ! [[ $1 =~ $re ]] ; then echo "Usage: $0 <VMID>" ; exit 1 ; fi 

# dump vm configuration into temp launch script
qm show $1 --pretty > launch$1.sh
chmod +x launch$1.sh

# replace OVMF with our updated one
# -drive 'if=pflash,unit=0,format=raw,readonly=on,file=/usr/share/pve-edk2-firmware//OVMF_CODE.fd' \
# -drive 'if=pflash,unit=0,format=raw,readonly,file=/root//OVMF.fd' \
sed -i 's/usr\/share\/pve-edk2-firmware\/\/OVMF_CODE.fd/root\/vtpm\/\/OVMF.fd/' launch$1.sh

# add a \ to the last line
sed -i '$ s/$/ \\/' launch$1.sh

# appen file with required extra lines
echo " -chardev 'socket,id=chrtpm,path=//var/tpm$1/swtpm-sock' \\" >> launch$1.sh
echo " -tpmdev 'emulator,id=tpm$1,chardev=chrtpm' \\"              >> launch$1.sh
echo " -device 'tpm-tis,tpmdev=tpm$1' \\"                          >> launch$1.sh
echo " -bios /root/OVMF.fd"                                        >> launch$1.sh

# create folder for the socket
[ ! -d "/var/tpm$1" ] && mkdir /var/tpm$1

# launch the service in the background
swtpm socket --tpmstate dir=/var/tpm$1 --tpm2 --ctrl type=unixio,path=/var/tpm$1/swtpm-sock &

# launch VM
./launch$1.sh

# delete temp launch script
rm ./launch$1.sh

First, configure the virtual machine in Proxmox as you would normally making a note of the VMID (101 etc).

Next run the script passing in the VMID

./vTPM-launch.sh 201

Looking at the Proxmox console you will see that the machine is using the custom OVMF UEFI bios.

After Windows is booted, opening the TPM Microsoft Management Console shows that Windows recognizes a valid TPM!

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Job done.

References:
1. [Guide] vTPM and Secureboot capability in a Proxmox-KVM [For Windows 11] – https://www.reddit.com/r/Proxmox/comments/oai5cr/guide_vtpm_and_secureboot_capability_in_a/
2. Common EDK II Build Instructions for Linux – https://github.com/tianocore/tianocore.github.io/wiki/Common-instructions
3. VTPM [rayures] – https://github.com/rayures/vTPM
4. Stefan Berger – libtpms and swtpm – https://github.com/stefanberger/
4. Gareth Jones – https://github.com/garjones/gareth.com/blob/main/vTPM-install.sh