systemd VS supervisor

https://github.com/systemd/systemd/issues/32028#issuecomment...

There are some very compelling arguments made there if you care to read them

Maybe it was because you weren't pointing out anything new?

There was a pull request to stop linking libzma to systemd before the attack even took place

https://github.com/systemd/systemd/pull/31550

This was likely one of many things that pushed the attackers to work faster, and forced them into making mistakes.

The PR for changing compression libraries to use dlopen() was opened several weeks before the xz-utils backdoor was revealed.

https://github.com/systemd/systemd/pull/31550

I find this the most plausible explanation by far:

* The highly professional outfit simply did not see teknoraver's commit to remove liblzma as standard dependency of systemd build scripts coming.

* The race was on between their compromised code and that commit. They had to win it, with as large a window as possible.

* This caused serious errors.

* The performance regression is __not__ big. It's lucky Andres caught it at all. It's also not necessarily all that simple to remove it. It's not simply a bug in a loop or some such.

* The payload of the 'hack' contains fairly easy ways for the xz hackers to update the payload. They actually used it to remove a real issue where their hackery causes issues with valgrind that might lead to discovering it, and they also used it to release 5.6.1 which rewrites significant chunks; I've as yet not read, nor know of any analysis, as to why they changed so much.

Extra info for those who don't know:

https://github.com/systemd/systemd/commit/3fc72d54132151c131...

That's a commit that changes how liblzma is a dependency of systemd. Not because the author of this commit knew anything was wrong with it. But, pretty much entirely by accident (although removing deps was part of the point of that commit), almost entirely eliminates the value of all those 2 years of hard work.

And that was with the finish line in sight for the xz hackers: On 24 feb 2024, the xz hackers release liblzma 5.6.0 which is the first fully operational compromised version. __12 days later systemd merges a commit that means it won't work__.

So now the race is on. Can they get 5.6.0 integrated into stable releases of major OSes _before_ teknoraver's commit that removes liblzma's status as direct dep of systemd?

I find it plausible that they knew about teknoraver's commit _just before_ Feb 24th 2024 (when liblzma v5.6.0 was released, the first backdoored release), and rushed to release ASAP, before doing the testing you describe. Buoyed by their efforts to add ways to update the payload which they indeed used - March 8th (after teknoraver's commit was accepted) it was used to fix the valgrind issue.

So, no, I don't find this weird, and I don't think the amateurish aspects should be taken as some sort of indication that parts of the outfit were amateuristic. As long as it's plausible that the amateuristic aspects were simply due to time pressure, it sounds like a really bad idea to make assumptions in this regard.

sshd is started by systemd.

systemd has several ways of starting programs and waiting until they're "ready" before starting other programs that depend on them: Type=oneshot, simple, exec, forking, dbus, notify, ...

A while back, several distro maintainers found problems with using Type=exec (?) and chose Type=notify instead. When sshd is ready, it notifies systemd. How you do notification is you send a datagram to systemd's unix domain socket. That's about 10 lines of C code. But to make life even simpler, systemd also provides the one-line sd_notify() call, which is in libsystemd.so. This library is so other programmers can easily integrate with systemd.

So the distro maintainers patched sshd to use the sd_notify() function from libsystemd.so

What else is in libsystemd.so? That's right, systemd also does logging. All the logging functions are in there, so user programs can do logging the systemd way. You can even _read_ logs, using the functions in libsystemd.so. For example, sd_journal_open_files().

By the way... systemd supports the environment variable SYSTEMD_JOURNAL_COMPRESS which can be LZ4, XZ or ZSTD, to allow systemd log files to be compressed.

So, if you're a client program, that needs to read systemd logs, you'll call sd_journal_open_files() in libsystemd.so, which may then need liblz4, liblzma or libzstd functions.

These compression libraries could be dynamically loaded, should sd_journal_open_files() need them - which is what https://github.com/systemd/systemd/pull/31550 submitted on the 29th February this year did. But clearly that's not in common use. No, right now, most libsystemd.so libraries have headers saying "you'll need to load liblz4.so, liblzma.so and libzstd before you can load me!", so liblzma.so gets loaded for the logging functions that sshd doesn't use, so the distro maintainers of sshd can add 1 line instead of 10 to notify systemd that sshd is ready.

They just added an example to the documentation[0] of how to implement the sd_notify protocol without linking to libsystemd, so a little bit of discarding systemd (or at least parts of it) does seem to be part of the solution.

[0] https://github.com/systemd/systemd/pull/32030/files

I think this analysis is more interesting if you consider these two events in particular:

2024-02-29: On GitHub, @teknoraver sends pull request to stop linking liblzma into libsystemd.[1]

2024-03-20: The attacker is now a co-contributor for a patchset proposed to the Linux kernel, with the patchset adding the attacker as a maintainer and mirroring activity with xz-utils.

A theory is that the attacker saw the sshd/libsystemd/xz-utils vector as closing soon with libsystemd removing its dependency on xz-utils. When building a Linux kernel image, the resulting image is compressed by default with gzip [3], but can also be optionally compressed using xz-utils (amongst other compression utilities). There's a lot of distributions of Linux which have chosen xz-utils as the method used to compress kernel images, particularly embedded Linux distributions.[4] xz-utils is even the recommended mode of compression if a small kernel build image is desired.[5] If the attacker can execute code during the process of building a new kernel image, they can cause even more catastrophic impacts than targeting sshd. Targeting sshd was always going to be limited due to targets not exposing sshd over accessible networks, or implementing passive optical taps and real time behavioural analysis, or receiving real time alerts from servers indicative of unusual activity or data transfers. Targeting the Linux kernel would have far worse consequences possible, particularly if the attacker was targeting embedded systems (such as military transport vehicles [6]) where the chance of detection is reduced due to lack of eyeballs looking over it.

[1] https://github.com/systemd/systemd/pull/31550

[2] https://lkml.org/lkml/2024/3/20/1004

[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

[4] https://github.com/search?q=CONFIG_KERNEL_XZ%3Dy&type=code

[5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

[6] https://linuxdevices.org/large-military-truck-runs-embedded-...

systemd merged a change to using dlopen for compression libraries recently https://github.com/systemd/systemd/pull/31550 which is a safer linking method in that sense.

1) Debian includes this downstream patch, also.

2) A potential explanation for "why now" is that systemd DID prevent these dependencies from loading automatically in a patch one month ago, and the patches enabling the backdoor merged a few days later. It could be a total coincidence or it could be that the attacker was trying to catch the window before it was closed on them https://github.com/systemd/systemd/pull/31550#issuecomment-1...

What I went with was having both a web server (Apache/Nginx) and PHP-FPM in the same container image, held together by Supervisor: http://supervisord.org/

In my case, the Dockerfile looks a bit like the following:

  # Whatever base web server image you want, Debian/Ubuntu based here

As you can see there are several methods of running devpi server including cron, launchd (OSX service), nginx, Windows service, and supervisord. It also has a systemd service file which we can use to manage the service easily as Ubuntu uses it for primary service management. First off though we're going to need a proxy script to ensure that devpi is running in the virtual environment:

If it's a linux box you can make it a systemctl service, or you could use http://supervisord.org/.

I used supervisord to start my server and the cloud SQL proxy within the same container. That should work for your use case too.

I convinced (previous) $dayjob to use it. It (nix) kind of hung around in the background with the team that used haskell for awhile, but became prime time when we needed to support a range of VMs running within client infrastructure that were in reality just running various python scripts under supervisord (http://supervisord.org/). The range of client machines (redhat, centos, debian, ubuntu all of different releases) with differing versions of python and supervisord were driving our support and devops teams crazy (but in a weird way - they thought they were being productive, and really enjoyed tweaking things to work with additional varieties of os...). Additionally, having to work around some minor pain points of supervisord (adding and removing config files and not interrupting running services) lead to the realisation that there was a perfectly good service manager at the bottom of the modern versions of these systems (systemd) and that nixos was just a nix wrapper around this systemd and it would only restart what actually changed...

Here's more information about the configuration file format, in case anyone is curious: http://supervisord.org/configuration.html

My problem is that it's not always immediately clear how software that would normally run as a systemd service could be launched in the foreground instead. It usually takes a bit of digging around.

This post is structured as follows: The first chapter Requirements and Design, describes the requirements for such an application, defines its processes, breaks it down into logical components, and proposes a data model. The second chapter Implementation, provides an introduction to key implementation issues, such as implementing asynchronous tasks and LDAP authentication. It also showcases the usage of Docker with Python SDK in the project, including network configuration, and describes the deployment configuration using supervisord. The final chapter summarizes the efforts and provides links to the code repositories.

I have set up supervisord running cron job. However based on the discussion in supervisord GitHub, it is not possible to redirect cron's spawned command output to supervisord.

The project MISP-Docker from Coolacid is providing a containerized version of the MISP solution. This all-in-one solution includes the frontend, background jobs, cronjobs and an HTTP Server (Nginx) all orchestrated by process manager tool called supervisor. External services such as the database and Redis aren’t part of the container but are necessary. We decided that this project is very a good starting point to scale the MISP on Kubernetes.