What is sandwine?

sandwine is a command-line tool to run Windows applications on GNU/Linux that offers more isolation than raw Wine and more convenience than raw bubblewrap. It uses Wine and bubblewrap (>=0.8.0), it does not replace them. sandwine is Software Libre written in Python 3, and is licensed under the "GPL v3 or later" license.

Installation

# pip3 install sandwine

Git development

git clone https://github.com/hartwork/sandwine
cd sandwine
python3 -m venv venv/
source venv/bin/activate
pip3 install .

Usage Examples

Install Winamp 5.66: no networking, no X11, no sound, no access to ~/* files

# cd ~/Downloads/
# sha256sum -c <(echo 'ac70a0c8a2928c91400b9ac3774b331f1d700f3486bab674dbd09da6b31fe130  winamp566_full_en-us.exe')
# WINEDEBUG=-all sandwine --dotwine winamp/:rw ./winamp566_full_en-us.exe /S /D='C:\Program' 'Files' '(x86)\Winamp' '5.66'

(The weird quoting in /D='C:\Program' 'Files' '(x86)\Winamp' '5.66' is documented behavior for NSIS.)

Run installed Winamp: with sound, with nested X11, no networking, no ~/* file access

# sandwine --pulseaudio --x11 --dotwine winamp/:rw --pass ~/Music/:ro --configure -- winamp

Argument --configure will bring up winecfg prior to Winamp so that you have a chance at unchecking these two boxes:

• Graphics:
  • Allow the window manage to *decorate* the windows
  • Allow the window manage to *control* the windows

If Winamp crashes right after showing the main window, run it once more, there is some Wine bug at work here.

Run Games (3D applications) with modern stack (Wayland)

sandwine --dotwine ~/.wine-games:rw --pass /path/to/Games/folder:rw --wayland --pulseaudio "/path/to/Games/folder/Start.exe"

--dotwine ~/.wine-games:rw is needed to specify persistent Wineprefix. Needed for saves to be stored.

--pass /path/to/Games/folder:rw is used if your Games sit in system storage path. If your games are located in Wineprefix like "~/.wine/drive_c/Games", you don't need this parameter.

Optional: --nvidia-gpu to enable access to Nvidia GPU.

Optional: --raw-input to enable access to controllers (gamepads).

Run Geiss Screensaver: with sound, with host X11 (careful!), no networking, no ~/* file access

sandwine --host-x11-danger-danger --pulseaudio --retry -- ./geiss.scr /S

--host-x11-danger-danger make sandwine talk to the host X11 server, which would expose you to keyloggers so please re-visit your threat model before using --host-x11-danger-danger.

--retry is used to start programs a second time that consistently crash from graphics issues in a fresh Wine environment the first but not the second time. Potentially a bug in Wine, needs more investigation.

PS: The Geiss Screensaver has its GitHub home at https://github.com/geissomatik/geiss .

Run wget: with networking, no X11, no sound, no access to ~/* files

# sandwine --network --no-wine -- wget -S -O/dev/null https://blog.hartwork.org/

Argument --no-wine is mostly intended for debugging, but is needed here to invoke non-Wine wget.

Under the Hood

sandwine aims to protect against Windows applications that:

• read and leak personal files through/to the Internet
• read and leak keystrokes from other running applications (related post)
• modify/destroy personal files
• modify/destroy system files

To achieve that, by default the launched application:

• Sees no files in ${HOME} and/or /home/ (but a tmpfs where written data lives in RAM and is being discarded on process termination, unless you pass --pass PATH:{ro,rw} for a related directory)
• Does not have access to the internet (unless you pass --network)
• Does not have access to your local X11 server (unless you enable some form of X11 integration, ideally nested X11)
• Does not have access to your local Wayland display server (unless you pass --wayland)
• Does not have access to your sound card (unless you pass --pulseaudio and/or --pipewire)
• Does not have access to your GPU card (unless you pass --nvidia-gpu)
• Does not have access to /dev/input (unless you pass --raw-input)
• Does not have access to /dev/dri (unless you pass --nvidia-gpu, --wayland, or enable X11 support some way)

So what is shared with the application by default then?

What is Exposed by Default?

Files

Environment Variables

• ${DISPLAY}
• ${HOME}
• ${HOSTNAME} (with random 12-hex-digits value)
• ${PATH} (with known-unavailable entries removed)
• ${TERM}
• ${USER}
• ${WINEDEBUG}
• ${WINEDLLOVERRIDES}
• ${wineserver} (lowercase, with the path to command wineserver)

sandwine features include:

• A focus on security, usability, transparency
• Support for nested X11 provided by:
  • X2Go nxagent (seamless)
  • Xephyr
  • Xnest
  • Xpra (experimental, careful!)
  • Xvfb (invisible)
• Support for Wayland
• Support for PulseAudio
• Support for PipeWire
• Support for /etc/resolv.conf provided by:
  • NetworkManager
  • systemd-resolved
• Support for Nvidia GPUs
• Support for NTsync

Threat Model and Known Limitations

• If your life depends on the sandbox, please consider using a virtual machine rather than sandwine, e.g. because your username is exposed to the running application and depending on your threat model, that may be too much already.
• sandwine is not intended for use with known-malicious software, viruses, malware.
• sandwine has not seen any known external security audits, yet.
• sandwine relies on bubblewrap for its security, so it can only be as secure as bubblewrap.
• sandwine does not limit the set of syscalls that the application can do. bubblewrap supports arguments --seccomp and --add-seccomp-fd to go further on that end, but sandwine does not use them so far.
• sandwine does not keep the application from using loads of RAM, CPU time and/or disk space. If your concerns include denial of service, you need protection beyond sandwine.
• sandwine relies on sane file permissions in the places that are shared read-only. If you have files in e.g. /etc that contain credentials but are readable by unprivileged users, sandwine will do nothing to block that read access.
• If the Windows application to be run expects a GNU/Linux environment and includes Linux Kernel exploit code, then that exploit is not likely to be stopped by sandwine.
• If you manually allow the sandboxed application to communicate with an unsandboxed application and the latter executes commands for the former, then the sandbox cannot prevent privilege escalation. Think of a model like the Docker daemon where whoever can talk to the Docker daemon can become root. If you use sandwine with something like that, sandwine will have a problem.
• Start-up time below 200ms is not a goal.

Reporting Vulnerabilities

If you think you found a vulnerability in sandwine, please reach out via e-mail so we can have a closer look and coordinate disclosure.

Sebastian Pipping, Berlin, 2023