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Major Linux PolicyKit Security Vulnerability Uncovered: Pwnkit

posted by martyb on Thursday January 27 2022, @04:34AM   Printer-friendly

upstart writes:

Major Linux PolicyKit security vulnerability uncovered: Pwnkit:

Polkit, formerly known as PolicyKit, is a systemd SUID-root program. It's installed by default in every major Linux distribution.

[...] This vulnerability is easy to exploit. And, with it, any ordinary user can gain full root privileges on a vulnerable computer by exploiting this vulnerability in its default configuration. As Qualys wrote in its brief description of the problem: "This vulnerability is an attacker's dream come true."

[...] Why is it so bad? Let us count the ways:

  • Pkexec is installed by default on all major Linux distributions.
  • Qualys has exploited Ubuntu, Debian, Fedora, and CentOS in their tests, and they're sure other distributions are also exploitable.
  • Pkexec has been vulnerable since its creation in May 2009 (commit c8c3d83, "Add a pkexec(1) command").
  • An unprivileged local user can exploit this vulnerability to get full root privileges.
  • Although this vulnerability is technically a memory corruption, it is exploitable instantly and reliably in an architecture-independent way.
  • And, last but not least, it's exploitable even if the polkit daemon itself is not running.

[...] While we know Linux can be attacked, Solaris and other Unix systems may also be vulnerable. We do know, however, that OpenBSD can't be attacked by exploits using this vulnerability.

Red Hat rates the PwnKit as having a Common Vulnerability Scoring System (CVSS) score of 7.8. This is high.

When used correctly, Polkit provides an organized way for non-privileged processes to communicate with privileged processes. It is also possible to use polkit to execute commands with elevated privileges using the command pkexec followed by the command intended to be executed with root permission.

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  • (Score: 4, Interesting) by digitalaudiorock on Thursday January 27 2022, @07:45PM (2 children)

    by digitalaudiorock (688) on Thursday January 27 2022, @07:45PM (#1216244)

    Despite what some say, it is not a systemd component (but is is a freedesktop.org project).

    Between those two it's a pretty close race as to who sucks more frankly (with the Mozilla devs arguably not far behind). Don't even get me started with the freedesktop.org project. Here's one I ran into recently:

    I use only fluxbox as a window manager. After a recent update to thunderbird I no longer had any Window decorations at all and couldn't even move the Window. Just to note: The only reason I use thunderbird for email is because I need a client that fully supports the Godless travesty that is HTML email (because of my work). If it weren't for that, I'd use a sane text only client like Claws mail. It turns out that the missing decorations issue was caused by the freedesktop.org's GTK3 "client side decorations" which they do NOT [github.com] allow you to disable, despite the fact that it breaks some window managers. With the help of another user on the gentoo forums I was able to come up with a patch that addressed this in fluxbox. I now have window decorations back...the ones that I want, and not the ones GTK3 wants.

    More importantly, you have to consider what they're doing with that whole concept of "client side decorations": You as a user choose a theme for the way you want windows to appear, any they say "fuck you..we want all GTK apps to look the same to protect our brand". And yes...although being (supposedly) part of the open source community, they very much DO use the term "brand" [wordpress.com].

    So yea, for me all three of systemd, Mozilla, and freedesktop.org pretty much epitomize everything that's wrong with Linux these day. Somehow I manage to maintain a sane, lean system despite all these a-holes.

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  • (Score: 0) by Anonymous Coward on Thursday January 27 2022, @11:27PM (1 child)

    by Anonymous Coward on Thursday January 27 2022, @11:27PM (#1216330)

    You may also check gtk3-nocsd. https://gpo.zugaina.org/x11-misc/gtk3-nocsd/Dep [zugaina.org]

    Also avaliable in other distros like Arch or Debian. Personally, irrespective of distro I need it for, I read Arch's wiki: lots of hints that can lead to discovering the proper solution in other distributions. In this case https://wiki.archlinux.org/title/GTK [archlinux.org] let me discover there is a newer nocsd repo https://github.com/ZaWertun/gtk3-nocsd [github.com] and a full set of patches https://github.com/lah7/gtk3-classic [github.com]