Firejail is a SUID sandbox program that reduces the risk of security breaches by restricting the running environment of untrusted applications using Linux namespaces, seccomp-bpf and Linux capabilities. It allows a process and all its descendants to have their own private view of the globally shared kernel resources, such as the network stack, process table, mount table. Firejail can work in a SELinux or AppArmor environment, and it is integrated with Linux Control Groups.
Written in C with virtually no dependencies, the software runs on any Linux computer with a 3.x kernel version or newer. It can sandbox any type of processes: servers, graphical applications, and even user login sessions. The software includes sandbox profiles for a number of more common Linux programs, such as Mozilla Firefox, Chromium, VLC, Transmission etc.
The sandbox is lightweight, the overhead is low. There are no complicated configuration files to edit, no socket connections open, no daemons running in the background. All security features are implemented directly in Linux kernel and available on any Linux computer. To start the sandbox, prefix your command with “firejail”:
$ firejail firefox # starting Mozilla Firefox
$ firejail transmission-gtk # starting Transmission BitTorrent
$ firejail vlc # starting VideoLAN Client
$ sudo firejail /etc/init.d/nginx start
Project webpage: https://firejail.wordpress.com/
Download and Installation: https://firejail.wordpress.com/download-2/
Features: https://firejail.wordpress.com/features-3/
Documentation: https://firejail.wordpress.com/documentation-2/
FAQ: https://firejail.wordpress.com/support/frequently-asked-questions/
Version 0.9.40-rc1 released!
X11 support is built around Xpra (http://xpra.org/) or Xephyr.
--x11 Start a new X11 server using Xpra or Xephyr and attach the sand‐
box to this server. The regular X11 server (display 0) is not
visible in the sandbox. This prevents screenshot and keylogger
applications started in the sandbox from accessing other X11
displays. A network namespace needs to be instantiated in order
to deny access to X11 abstract Unix domain socket.
Firejail will try first Xpra, and if Xpra is not installed on
the system, it will try to find Xephyr. This feature is not
available when running as root.
Example:
$ firejail --x11 --net=eth0 firefox
--x11=xpra
Start a new X11 server using Xpra (http://xpra.org) and attach
the sandbox to this server. Xpra is a persistent remote display
server and client for forwarding X11 applications and desktop
screens. On Debian platforms Xpra is installed with the command
sudo apt-get install xpra. This feature is not available when
running as root.
Example:
$ firejail --x11 --net=eth0 firefox
--x11=xephyr
Start a new X11 server using Xephyr and attach the sandbox to
this server. Xephyr is a display server implementing the X11
display server protocol. It runs in a window just like other X
applications, but it is an X server itself in which you can run
other software. The default Xephyr window size is 800x600. This
can be modified in /etc/firejail/firejail.config file, see man 5
firejail-config for more details.
The recommended way to use this feature is to run a window man‐
ager inside the sandbox. A security profile for OpenBox is pro‐
vided. On Debian platforms Xephyr is installed with the command
sudo apt-get install xserver-xephyr. This feature is not avail‐
able when running as root.
Example:
$ firejail --x11 --net=eth0 openbox
More information here: https://firejail.wordpress.com/documentation-2/x11-guide/
FILE TRANSFER
These features allow the user to inspect the filesystem container of an
existing sandbox and transfer files from the container to the host
filesystem.
--get=name filename
Retrieve the container file and store it on the host in the cur‐
rent working directory. The container is specified by name
(--name option). Full path is needed for filename.
--get=pid filename
Retrieve the container file and store it on the host in the cur‐
rent working directory. The container is specified by process
ID. Full path is needed for filename.
--ls=name dir_or_filename
List container files. The container is specified by name
(--name option). Full path is needed for dir_or_filename.
--ls=pid dir_or_filename
List container files. The container is specified by process ID.
Full path is needed for dir_or_filename.
Examples:
$ firejail --name=mybrowser --private firefox
$ firejail --ls=mybrowser ~/Downloads
drwxr-xr-x netblue netblue 4096 .
drwxr-xr-x netblue netblue 4096 ..
-rw-r--r-- netblue netblue 7847 x11-x305.png
-rw-r--r-- netblue netblue 6800 x11-x642.png
-rw-r--r-- netblue netblue 34139 xpra-clipboard.png
$ firejail --get=mybrowser ~/Downloads/xpra-clipboard.png
NAME
Firecfg - Desktop configuration program for Firejail software.
SYNOPSIS
firecfg [OPTIONS]
DESCRIPTION
Firecfg is the desktop configuration utility for Firejail software. The
utility creates several symbolic links to firejail executable. This
allows the user to sandbox applications automatically, just by clicking
on a regular desktop menus and icons.
The symbolic links are placed in /usr/local/bin. For more information,
see DESKTOP INTEGRATION section in man 1 firejail.
OPTIONS
--clean
Remove all firejail symbolic links
-?, --help
Print options end exit.
--list List all firejail symbolic links
--version
Print program version and exit.
Example:
$ sudo firecfg
/usr/local/bin/firefox created
/usr/local/bin/vlc created
[...]
$ firecfg --list
/usr/local/bin/firefox
/usr/local/bin/vlc
[...]
$ sudo firecfg --clean
/usr/local/bin/firefox removed
/usr/local/bin/vlc removed
[...]
Most Linux kernel security features require root privileges during configuration. The same is true for kernel networking features. Firejail (SUID binary) opens the access to these features to regular users. The privilege escalation is restricted to the sandbox being configured, and is not extended to the rest of the system. This arrangement works fine for user desktops or servers where the access is already limited.
If you not happy with a particular feature, all the support can be eliminated from SUID binary at compile time, or at run time by editing /etc/firejail/firejail.config file.
The following features can be enabled or disabled:
bind Enable or disable bind support, default enabled.
chroot Enable or disable chroot support, default enabled.
file-transfer
Enable or disable file transfer support, default enabled.
network
Enable or disable networking features, default enabled.
restricted-network
Enable or disable restricted network support, default disabled.
If enabled, networking features should also be enabled (network
yes). Restricted networking grants access to --interface and
--net=ethXXX only to root user. Regular users are only allowed
--net=none.
secomp Enable or disable seccomp support, default enabled.
userns Enable or disable user namespace support, default enabled.
x11 Enable or disable X11 sandboxing support, default enabled.
xephyr-screen
Screen size for --x11=xephyr, default 800x600. Run
/usr/bin/xrandr for a full list of resolutions available on your
specific setup. Examples:
xephyr-screen 640x480
xephyr-screen 800x600
xephyr-screen 1024x768
xephyr-screen 1280x1024
Currently 50 syscalls are blacklisted by default, out of a total of 318 calls (AMD64, Debian Jessie).
The current netfilter configuration (--netfilter option) looks like this:
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
# allow ping
-A INPUT -p icmp --icmp-type destination-unreachable -j ACCEPT
-A INPUT -p icmp --icmp-type time-exceeded -j ACCEPT
-A INPUT -p icmp --icmp-type echo-request -j ACCEPT
# drop STUN (WebRTC) requests
-A OUTPUT -p udp --dport 3478 -j DROP
-A OUTPUT -p udp --dport 3479 -j DROP
-A OUTPUT -p tcp --dport 3478 -j DROP
-A OUTPUT -p tcp --dport 3479 -j DROP
COMMIT
The filter is loaded by default for Firefox if a network namespace is configured:
$ firejail --net=eth0 firefox
--nice=value
Set nice value for all processes running inside the sandbox.
Example:
$ firejail --nice=-5 firefox
$ man firejail-profile
[...]
mkdir directory
Create a directory in user home. Use this command for
whitelisted directories you need to preserve when the sandbox is
closed. Subdirectories also need to be created using mkdir.
Example from firefox profile:
mkdir ~/.mozilla
whitelist ~/.mozilla
mkdir ~/.cache
mkdir ~/.cache/mozilla
mkdir ~/.cache/mozilla/firefox
whitelist ~/.cache/mozilla/firefox
[...]
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