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/

X11 support is built around Xpra (http://xpra.org/). So far I've seen it working on Debian 7 and 8, and Ubuntu 14.04. If you manage to run it on another distribution, please let me know. Example:

$ firejail --x11 --net=eth0 firefox

--x11 starts the server, --net is required in order to remove the main X11 server socket from the sandbox. More information here: https://firejail.wordpress.com/documentation-2/x11-guide/

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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