CVE-2020-17367: GitHub - netblue30/firejail: Linux namespaces and seccomp-bpf sandbox

Firejail

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.

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://github.com/netblue30/firejail/wiki/Frequently-Asked-Questions

Wiki: https://github.com/netblue30/firejail/wiki

GitLab-CI status: https://gitlab.com/Firejail/firejail_ci/pipelines/

Video Channel: https://odysee.com/@netblue30:9?order=new

Backup Video Channel: https://www.bitchute.com/profile/JSBsA1aoQVfW/

Security vulnerabilities

We take security bugs very seriously. If you believe you have found one, please report it by emailing us at [email protected]

Security Advisory - Feb 8, 2021

Summary: A vulnerability resulting in root privilege escalation was discovered in
Firejail's OverlayFS code,

Versions affected: Firejail software versions starting with 0.9.30.
Long Term Support (LTS) Firejail branch is not affected by this bug.

Workaround: Disable overlayfs feature at runtime.
In a text editor open /etc/firejail/firejail.config file, and set "overlayfs" entry to "no".

      $ grep overlayfs /etc/firejail/firejail.config
      # Enable or disable overlayfs features, default enabled.
      overlayfs no

Fix: The bug is fixed in Firejail version 0.9.64.4

GitHub commit: (file configure.ac)
https://github.com/netblue30/firejail/commit/97d8a03cad19501f017587cc4e47d8418273834b

Credit:  Security researcher Roman Fiedler analyzed the code and discovered the vulnerability.
Functional PoC exploit code was provided to Firejail development team.
A description of the problem is here on Roman's blog:

https://unparalleled.eu/publications/2021/advisory-unpar-2021-0.txt
https://unparalleled.eu/blog/2021/20210208-rigged-race-against-firejail-for-local-root/

Installing****Debian

Debian stable (bullseye): We recommend to use the backports package.

Ubuntu

For Ubuntu 18.04+ and derivatives (such as Linux Mint), users are strongly advised to use the PPA.

How to add and install from the PPA:

sudo add-apt-repository ppa:deki/firejail sudo apt-get update sudo apt-get install firejail firejail-profiles

Reason: The firejail package for Ubuntu 20.04 has been left vulnerable to CVE-2021-26910 for months after a patch for it was posted on Launchpad:

• firejail version in Ubuntu 20.04 LTS is vulnerable to CVE-2021-26910

See also https://wiki.ubuntu.com/SecurityTeam/FAQ:

What software is supported by the Ubuntu Security team?

Ubuntu is currently divided into four components: main, restricted, universe and multiverse. All binary packages in main and restricted are supported by the Ubuntu Security team for the life of an Ubuntu release, while binary packages in universe and multiverse are supported by the Ubuntu community.

Additionally, the PPA version is likely to be more recent and to contain more profile fixes.

See the following discussions for details:

• Should I keep using the version of firejail available in my distro repos?
• How to install the latest version on Ubuntu and derivatives

Other

Firejail is included in a large number of Linux distributions.

Note: The firejail 0.9.52-LTS version is deprecated.

You can also install one of the released packages, or clone Firejail’s source code from our Git repository and compile manually:

$ git clone https://github.com/netblue30/firejail.git
$ cd firejail
$ ./configure && make && sudo make install-strip

On Debian/Ubuntu you will need to install git and gcc compiler. AppArmor development libraries and pkg-config are required when using --apparmor ./configure option:

$ sudo apt-get install git build-essential libapparmor-dev pkg-config gawk

For --selinux option, add libselinux1-dev (libselinux-devel for Fedora).

Detailed information on using firejail from git is available on the wiki.

Running the sandbox

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

Run firejail --list in a terminal to list all active sandboxes. Example:

$ firejail --list
1617:netblue:/usr/bin/firejail /usr/bin/firefox-esr
7719:netblue:/usr/bin/firejail /usr/bin/transmission-qt
7779:netblue:/usr/bin/firejail /usr/bin/galculator
7874:netblue:/usr/bin/firejail /usr/bin/vlc --started-from-file file:///home/netblue/firejail-whitelist.mp4
7916:netblue:firejail --list

Desktop integration

Integrate your sandbox into your desktop by running the following two commands:

$ firecfg --fix-sound
$ sudo firecfg

The first command solves some shared memory/PID namespace bugs in PulseAudio software prior to version 9. The second command integrates Firejail into your desktop. You would need to logout and login back to apply PulseAudio changes.

Start your programs the way you are used to: desktop manager menus, file manager, desktop launchers. The integration applies to any program supported by default by Firejail. There are about 250 default applications in current Firejail version, and the number goes up with every new release. We keep the application list in /etc/firejail/firecfg.config file.

Security profiles

Most Firejail command line options can be passed to the sandbox using profile files. You can find the profiles for all supported applications in /etc/firejail directory.

If you keep additional Firejail security profiles in a public repository, please give us a link:

• https://github.com/chiraag-nataraj/firejail-profiles

• https://github.com/triceratops1/fe

Use this issue to request new profiles: #1139

You can also use this tool to get a list of syscalls needed by a program: contrib/syscalls.sh.

We also keep a list of profile fixes for previous released versions in etc-fixes directory.

Latest released version: 0.9.68****Current development version: 0.9.69

Milestone page: https://github.com/netblue30/firejail/milestone/1

Shell tab completion

       --tab  Enable shell tab completion in sandboxes using private or whitelisted
              home directories.

              $ firejail --private --tab

Profile Statistics

A small tool to print profile statistics. Compile and install as usual. The tool is installed in /usr/lib/firejail directory. Run it over the profiles in /etc/profiles:

$ /usr/lib/firejail/profstats /etc/firejail/*.profile
No include .local found in /etc/firejail/noprofile.profile
Warning: multiple caps in /etc/firejail/transmission-daemon.profile

Stats:
    profiles            1184
    include local profile   1183   (include profile-name.local)
    include globals     1152   (include globals.local)
    blacklist ~/.ssh        1057   (include disable-common.inc)
    seccomp         1076
    capabilities        1178
    noexec          1064   (include disable-exec.inc)
    noroot          985
    memory-deny-write-execute   259
    apparmor            707
    private-bin         686
    private-dev         1040
    private-etc         537
    private-tmp         911
    whitelist home directory    567
    whitelist var       849   (include whitelist-var-common.inc)
    whitelist run/user      1153   (include whitelist-runuser-common.inc
                    or blacklist ${RUNUSER})
    whitelist usr/share     621   (include whitelist-usr-share-common.inc
    net none            403
    dbus-user none      670
    dbus-user filter        114
    dbus-system none        824
    dbus-system filter      10

New profiles:

onionshare, onionshare-cli, opera-developer, songrec