qubes-mirage-firewall

A unikernel that can run as a QubesOS ProxyVM, replacing sys-firewall. It uses the mirage-qubes library to implement the Qubes protocols.

Note: This firewall ignores the rules set in the Qubes GUI. See rules.ml for the actual policy.

See A Unikernel Firewall for QubesOS for more details.

Binary releases

Pre-built binaries are available from the releases page. See the Deploy section below for installation instructions.

Build from source

Create a new Fedora-30 AppVM (or reuse an existing one). In the Qube's Settings (Basic / Disk storage), increase the private storage max size from the default 2048 MiB to 4096 MiB. Open a terminal.

Clone this Git repository and run the build-with-docker.sh script:

mkdir /home/user/docker
sudo ln -s /home/user/docker /var/lib/docker
sudo dnf install docker
sudo systemctl start docker
git clone https://github.com/mirage/qubes-mirage-firewall.git
cd qubes-mirage-firewall
sudo ./build-with-docker.sh

This took about 10 minutes on my laptop (it will be much quicker if you run it again). The symlink step at the start isn't needed if your build VM is standalone. It gives Docker more disk space and avoids losing the Docker image cache when you reboot the Qube.

Note: the object files are stored in the _build directory to speed up incremental builds. If you change the dependencies, you will need to delete this directory before rebuilding.

If you want to build on Debian, follow the instructions at docker.com to get Docker and then run sudo ./build-with-docker.sh as above.

It's OK to install the Docker package in a template VM if you want it to remain after a reboot, but the build of the firewall itself should be done in a regular AppVM.

You can also build without Docker, as for any normal Mirage unikernel; see the Mirage installation instructions for details.

The Docker build fixes the versions of the libraries it uses, ensuring that you will get exactly the same binary that is in the release. If you build without Docker, it will build against the latest versions instead (and the hash will therefore probably not match). However, it should still work fine.

Deploy

If you want to deploy manually, unpack mirage-firewall.tar.bz2 in dom0, inside /var/lib/qubes/vm-kernels/. e.g. (if dev is the AppVM where you built it):

[tal@dom0 ~]$ cd /var/lib/qubes/vm-kernels/
[tal@dom0 vm-kernels]$ qvm-run -p dev 'cat qubes-mirage-firewall/mirage-firewall.tar.bz2' | tar xjf -

The tarball contains vmlinuz, which is the unikernel itself, plus a couple of dummy files that Qubes requires.

Run this command in dom0 to create a mirage-firewall VM using the mirage-firewall kernel you added above:

qvm-create \
  --property kernel=mirage-firewall \
  --property kernelopts=None \
  --property memory=32 \
  --property maxmem=32 \
  --property netvm=sys-net \
  --property provides_network=True \
  --property vcpus=1 \
  --property virt_mode=pv \
  --label=green \
  --class StandaloneVM \
  mirage-firewall

To upgrade from an earlier release, just overwrite /var/lib/qubes/vm-kernels/mirage-firewall/vmlinuz with the new version and restart the firewall VM.

Configure AppVMs to use it

You can run mirage-firewall alongside your existing sys-firewall and you can choose which AppVMs use which firewall using the GUI. To configure an AppVM to use it, go to the app VM's settings in the GUI and change its NetVM from default (sys-firewall) to mirage-firewall.

You can also configure it by running this command in dom0 (replace my-app-vm with the AppVM's name):

qvm-prefs --set my-app-vm netvm mirage-firewall

Alternatively, you can configure mirage-firewall to be your default firewall VM.

Note that by default dom0 uses sys-firewall as its "UpdateVM" (a proxy for downloading updates). mirage-firewall cannot be used for this, but any Linux VM should be fine. https://www.qubes-os.org/doc/software-update-dom0/ says:

The role of UpdateVM can be assigned to any VM in the Qubes VM Manager, and there are no significant security implications in this choice. By default, this role is assigned to the firewallvm.

Components

This diagram show the main components (each box corresponds to a source .ml file with the same name):

Ethernet frames arrives from client qubes (such as work or personal) or from sys-net. Internet (IP) packets are sent to firewall, which consults rules to decide what to do with the packet. If it should be sent on, it uses router to send it to the chosen destination. client_net watches the XenStore database provided by dom0 to find out when clients need to be added or removed.

The boot process:

• config.ml describes the libraries used and static configuration settings (NAT table size). The mirage tool uses this to generate main.ml.
• main.ml initialises the drivers selected by config.ml and calls the start function in unikernel.ml.
• unikernel.ml connects the Qubes agents, sets up the networking components, and then waits for a shutdown request.

Easy deployment for developers

For development, use the test-mirage scripts to deploy the unikernel (qubes_firewall.xen) from your development AppVM. This takes a little more setting up the first time, but will be much quicker after that. e.g.

$ test-mirage qubes_firewall.xen mirage-firewall
Waiting for 'Ready'... OK
Uploading 'qubes_firewall.xen' (5901080 bytes) to "mirage-firewall"
Waiting for 'Booting'... OK
--> Loading the VM (type = ProxyVM)...
--> Starting Qubes DB...
--> Setting Qubes DB info for the VM...
--> Updating firewall rules...
--> Starting the VM...
--> Starting the qrexec daemon...
Waiting for VM's qrexec agent.connected
--> Starting Qubes GUId...
Connecting to VM's GUI agent: .connected
--> Sending monitor layout...
--> Waiting for qubes-session...
Connecting to mirage-firewall console...
MirageOS booting...
Initialising timer interface
Initialising console ... done.
gnttab_stubs.c: initialised mini-os gntmap
2017-03-18 11:32:37 -00:00: INF [qubes.rexec] waiting for client...
2017-03-18 11:32:37 -00:00: INF [qubes.gui] waiting for client...
2017-03-18 11:32:37 -00:00: INF [qubes.db] connecting to server...
2017-03-18 11:32:37 -00:00: INF [qubes.db] connected
2017-03-18 11:32:37 -00:00: INF [qubes.rexec] client connected, using protocol version 2
2017-03-18 11:32:37 -00:00: INF [qubes.db] got update: "/qubes-keyboard" = "xkb_keymap {\n\txkb_keycodes  { include \"evdev+aliases(qwerty)\"\t};\n\txkb_types     { include \"complete\"\t};\n\txkb_compat    { include \"complete\"\t};\n\txkb_symbols   { include \"pc+gb+inet(evdev)\"\t};\n\txkb_geometry  { include \"pc(pc105)\"\t};\n};"
2017-03-18 11:32:37 -00:00: INF [qubes.gui] client connected (screen size: 6720x2160)
2017-03-18 11:32:37 -00:00: INF [unikernel] Qubes agents connected in 0.095 s (CPU time used since boot: 0.008 s)
2017-03-18 11:32:37 -00:00: INF [net-xen:frontend] connect 0
2017-03-18 11:32:37 -00:00: INF [memory_pressure] Writing meminfo: free 6584 / 17504 kB (37.61 %)
Note: cannot write Xen 'control' directory
2017-03-18 11:32:37 -00:00: INF [net-xen:frontend] create: id=0 domid=1
2017-03-18 11:32:37 -00:00: INF [net-xen:frontend]  sg:true gso_tcpv4:true rx_copy:true rx_flip:false smart_poll:false
2017-03-18 11:32:37 -00:00: INF [net-xen:frontend] MAC: 00:16:3e:5e:6c:11
2017-03-18 11:32:37 -00:00: WRN [command] << Unknown command "QUBESRPC qubes.SetMonitorLayout dom0"
2017-03-18 11:32:38 -00:00: INF [ethif] Connected Ethernet interface 00:16:3e:5e:6c:11
2017-03-18 11:32:38 -00:00: INF [arpv4] Connected arpv4 device on 00:16:3e:5e:6c:11
2017-03-18 11:32:38 -00:00: INF [dao] Watching backend/vif
2017-03-18 11:32:38 -00:00: INF [qubes.db] got update: "/qubes-netvm-domid" = "1"

Testing if the firewall works

Build the test unikernel in the test directory. Install it to a vm which has the firewall as netvm. Set the rules for the testvm to "textfile". Run the test unikernel.

Security advisories

See issues tagged "security" for security advisories affecting the firewall.

LICENSE

Copyright (c) 2019, Thomas Leonard All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.