Submitted 2 years ago by Ziggurat@sh.itjust.works to [deleted]
My mastodon feed is full of IT security specialist talking about the xz affair where someone let a backdoor in some library.
But beside showing the two side of Free/Libre software (anybody can add a backdoor, and anybody can spot it), I have no idea how it impacts the average person. Is it a common library or something used only by specific application ? Would my home-grade router protects me ?
Quick summary:
liblzma is a library for the lzma compression format. Loosely, this means it’s used by various other pieces of software that need this type of compression, rather than being an application itself.
It is very widely used. It comes installed on most major Linux distributions and is used by software like openssh, one of the standard remote connection packages.
However, since it was only in the tarball, you wouldn’t see it widely until debian, fedora, et al release a new version that includes the latest liblzma updates. This version hadn’t been added to any of the stable release channels yet, so the typical user wouldn’t have gotten it yet.
I believe this would have gone out in debian 12.6 next week, and the attacker was actively petitioning fedora maintainers to get it added to fedora 40 & 41
The interesting thing about this situation was how much effort the attacker put in to gain trust just to get to the point where they could do this, and how targeted the vulnerability seems to have been. They tried very hard to reduce the likelihood of being caught by only hitting a limited set of configurations
I’m still confused exactly what the circumstances would be where this worked as the attacker intended. Would simply having the infected liblzma version on the system create the vulnerability or does something have to happen to invoke it and then what? What’s he chain of events that would have happened had this worked perfectly and gone undetected? I tried to read some of the more detailed analysis but the stuff went way over my head.
Also, what about Mac OS? Can the package create any vulnerability there if installed via homebrew as it’s reported to have done in some cases? Or is that environment also not right for it to work?
Here’s how it was intended to work:
only someone running arch or debian sid or an bleeding edge rolling release on an internet exposed ssh port. the idea of that configuration would sound ludicrous. even so we should be building off git repos not tar balls.
the weird part this situation has made me feel safer. the amount of work that went into social engineering this and it only lasted a month tops for people that run distros that would just not be or should not be used as an exposed server ever.
it shows open source works. This is more embarrassing than anything and we deserve it. We need to pay core library devs and have a mechanism that core libraries can be handed off to a trusted org.while another upstream maintainer can be found or the project shut down and other projects move away from the un maintained project. When the person maintaining the project gets burned out or has other issues.
From the archlinux.org news post on the issue.
Arch does not directly link openssh to liblzma, and thus this attack vector is not possible.
oh 100% i was just taking in general of upstream bleeding edge distro being vulnerable to this kind of upstream attack not specific to xz
why does everyone keep mentioning arch?
For exploits like this, most of the risk is in services you use. Websites, power company customer database, etc. are at risk of customer data dumps leaking.
Be extra alert for targeted scams and phishing, i.e. Phil from HBO Max customer department calling and asking to correct your payment details and he sounds very convincing because he knows your username, viewing history, etc.
And be extra fast with installing any security updates on all your stuff.
The average user? Likely doesn’t. the package is for Linux, so that removes any windows users.
The version was only on “bleeding edge” releases, so if you are on a lts release you will likely be ok.
I’m one of those security specialists (although not on mastodon). To be clear, if a vulnerable version of libxz were included in a distribution that we actually use; this would be an all hands on deck, drop everything until it is fixed emergency.
Having said that, for an average user, it probably doesn’t matter. First, many users just don’t have the vulnerable version installed. All things considered, it was found very quickly; so only rolling release distros would have it. Additionally, it appears that only .deb or .rpm based distributions would have it. Not because they are particularly vulnerable, the attack explicitly tests for it.
However, lets set all of this asside and assume a typical use is running a vulnerable system. In my assessment, the risk to them is still quite low. With most vulnerabilities, the hard part is discovering it. Once that happens, the barrier to exploiting it is relatively low, so you get a bunch of unrelated hackers trying to exploit any system they can find. This case is different; exploiting it requires the attackers private key. Even though the attack is now widely known, there is still only 1 organization capable of using it.
Further, this attack was sophisticated. I’m not going to go as far as others in saying that only a state actor could do it. However, it is hard to think of anyone other than a state actor who would do it. Maybe a group of college kids doing it for the lolz research? But, if the motivation us lolz, I don’t see them pivoting to do anything damaging with it. And even if they wanted to, there would still only be a handful of them. In short, this is one of those cases where obscurity works. Whoever did this attack does not know or care about Joe the Linux user; and they were probably never going to risk burning it by exploiting it on a large scale.
However, setting all of that asside, suppose you were using vulnerable software, and someone with the private key is interested in your home system. First, you would need to be running OpenSSH on a remotely accessible interface. [0]. Second, you would need your firewall to allow remote SSH traffic. Third, you would need your router to have port forwarding enabled; and explicitly configured to forward traffic to your OpenSSH server [1].
If all of that happens; then yes, you would be at risk.
[0] Even though the attack itself is in the libxz library, it appears to specifically target OpenSSH.
[1] Or, the attacker would need some other mechanism to get on the same network as you.
I don’t even have xz installed on my machine. Could anyone clue me in for what it is normally used?
It’s a library for a specific type of compression. You may have seen .tar.xz files.
sneakyninjapants@sh.itjust.works 2 years ago
It doesn’t.
Average person:
The malicious code was discovered within a day or two of upload iirc and presumably very few people were affected by this. There’s more to it but it’s technical and not directly relevant to your question.
For the average person it has no practical impact. For those involved with or interested in software supply chain security, it’s a big deal.
Cryophilia@lemmy.world 2 years ago
I don’t even understand what anyone in this thread is saying.
That’s not an invitation, please don’t explain Linux to me.
I’m just saying this means nothing for average people.
hperrin@lemmy.world 2 years ago
It could have meant a lot to the average person if it wasn’t caught. If this was some adversary, they could have used it to cripple critical infrastructure in the largest cyber attack in history.
earmuff@lemmy.dbzer0.com 2 years ago
It actually means a lot for average people. Only because you are not able to comprehend some things, does not mean you are not affected by it. But feel free to keep on using Windows XP.
maxprime@lemmy.ml 2 years ago
Can I explain GUN/Linux to you?
earmuff@lemmy.dbzer0.com 2 years ago
Not just a day, a full month the backdoor was available. On the Arch Repo, v5.6.0 was uploaded on February 24th. Will be similar to other repos.
SteveTech@programming.dev 2 years ago
I believe 5.6.0 was in Debian testing for almost a month too.
sneakyninjapants@sh.itjust.works 2 years ago
Thanks for the correction. A full month is much more problematic.
qaz@lemmy.world 2 years ago
You forgot about OpenSUSE Tumbleweed, it also shipped the infected package. I had to update to a newer non-infected version of xz.
sneakyninjapants@sh.itjust.works 2 years ago
Thanks, SUSE completely slipped my mind
Hawk@lemmynsfw.com 2 years ago
What about vpn behind WireGuard/OpenVPV?
I would presume no?