481–490 of 862 posts
As a de facto maintainer of an obscure open source game, I see devs come and go. I just merge all the worthwhile contributions. Some collaborators go pretty deep with their features, with a variety of coding styles, in a mishmash of C and C++. I'm not always across the implementation details, but in the back of my mind I'm thinking, man, anyone could just code up some real nasty backdoor and the project would be scre…
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dont you think that something as simple as a CLA (contributor legal agreement) would prevent this type of thing? of course creates noise in the open source contribution funnel, but let's be honest: if you are dedicating yourself to something like contributing to oss, signing a CLA should not be something unrealistic.
What exactly is a CLA going to do to a CCP operative (as appears to be the case with xz)? Do you think the party is going to extradite one of their state sponsored hacking groups because they got caught trying to implement a backdoor? Or do you think they don’t have the resources to fake an identity?
There appears to be a string encoded in the binary payload: https://gist.github.com/q3k/af3d93b6a1f399de28fe194add452d01... Which functions as a killswitch: https://piaille.fr/@zeno/112185928685603910 If that is indeed the case, one mitigation might be ``` echo "yolAbejyiejuvnup=Evjtgvsh5okmkAvj" | sudo tee -a /etc/environment ```
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Another analysis locates Jia in Eastern Europe: https://rheaeve.substack.com/p/xz-backdoor-times-damned-time... But I would like to see analysis of timestamp of GitHub events (like PRs and comments timestamps) which are harder to fake.
It's a nice analysis but he misses the fact that the Eastern Europe timezone doesn't match office hours, in particular it'd mean he worked around evenings primarily (see this graph https://files.catbox.moe/4itspl.png ) I had noticed UTC+0300 commits in the repository under his name but I believed they might have been simply committed by the main Finnish maintainer who is in the UTC+0300 timezone. > But I would like t…
There was this one though where they are the author and committer... one in +0300, the other in +0800:
commit 3d1fdddf92321b516d55651888b9c669e254634e
Author: Jia Tan
AuthorDate: Tue Jun 27 17:27:09 2023 +0300
Commit: Jia Tan
CommitDate: Tue Jun 27 23:56:06 2023 +0800
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You can imagine a door that opens if you knock on it just right. For anyone without the secret knock, it appears and functions as a wall. Without the secret knock, there might not even be a way to prove it opens at all. This is sort of the situation here. xz tries to decode some data before it does anything shady; since it is asymmetric; it can do the decryption without providing the secret encryption key (it has the…
I understand that we may never see the secret knock but shouldn't we have the door and what's behind it now? Doesn't this mean that the code is quite literally too hard to figure out for a human being? It's not like he can send a full new executable binary that he simply executes, then we'd see that the door is e.g the exec() call. Honestly this attempt makes me think that the entire c/c++ language stack and ecosyste…
I imagine that we could in short order build ourselves a modified version of the malware, which contains a different secret knock, one that we know in advance, and then test what would have happened with the malware when the secret knock was given. But this still doesn't help us probe existing servers for the flaw, because those servers aren't running our modified version of the malware, they're running the original malware.
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> The problem with xz wasn't a small community; it was no community. A single malicious actor got control of the project, and there was little oversight from anyone else. So because of this a lot of other highly used software was importing and depending on unreviewed code. It's scary to think how common this is. The attack surface seems unmanageable. There need to be tighter policies around what dependencies are incl…
> There need to be tighter policies around what dependencies are included, ensuring that they meet some kind of standard. This is why it's a good practice to minimize the amount of dependencies, and add dependencies only when absolutely required. Taking this a step further, doing a cursory review of each dependency, seeing the transitive dependencies it introduces, are also beneficial. Of course, it's impractical to…
The only thing that would effectively do this, is that people stop trusting build artifacts and instead use direct from public repositories packaging. You could figure out if someone maliciously modified the release artifact by comparing it against the tagged version, but at that point, why not just shallow clone the entire thing and be done.
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One completely awful thing some scanners might choose to do is if you're offering RSA auth (which most SSH servers are and indeed the SecSH RFC says this is Mandatory To Implement) then you're "potentially vulnerable" which would encourage people to do password auth instead. Unless we find that this problem has somehow infested a lot of real world systems that seems to me even worse than the time similar "experts" de…
Have to admit I've never understood why password auth is considered so much worse than using a cert - surely a decent password (long, random, etc) is for all practical purposes unguessable, and so you're either using a private RSA key that no-one can guess, or a password that no-one can guess, and then what's the difference? With the added inconvenience of having to pass around a certificate if you want to login to t…
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You can imagine a door that opens if you knock on it just right. For anyone without the secret knock, it appears and functions as a wall. Without the secret knock, there might not even be a way to prove it opens at all. This is sort of the situation here. xz tries to decode some data before it does anything shady; since it is asymmetric; it can do the decryption without providing the secret encryption key (it has the…
I understand that we may never see the secret knock but shouldn't we have the door and what's behind it now? Doesn't this mean that the code is quite literally too hard to figure out for a human being? It's not like he can send a full new executable binary that he simply executes, then we'd see that the door is e.g the exec() call. Honestly this attempt makes me think that the entire c/c++ language stack and ecosyste…
C/C++ is not a problem here because sshd has to run things to open sessions for users.
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You can imagine a door that opens if you knock on it just right. For anyone without the secret knock, it appears and functions as a wall. Without the secret knock, there might not even be a way to prove it opens at all. This is sort of the situation here. xz tries to decode some data before it does anything shady; since it is asymmetric; it can do the decryption without providing the secret encryption key (it has the…
I understand that we may never see the secret knock but shouldn't we have the door and what's behind it now? Doesn't this mean that the code is quite literally too hard to figure out for a human being? It's not like he can send a full new executable binary that he simply executes, then we'd see that the door is e.g the exec() call. Honestly this attempt makes me think that the entire c/c++ language stack and ecosyste…
Still, let me try. In this case, someone on the inside of the building looked in a dusty closet and saw a strange pair of hinges on the wall of the closet. Turns out that the wall of the closet is an exterior wall adjoining the alley back behind the building! At least they know which contractor built this part of the building.
Further examination revealed the locking mechanism that keeps the secret door closed until the correct knock is used. But because the lock is based on the deep mathematics of prime numbers, no mere examination of the lock will reveal the pattern of locks that will open it. The best you could do is sit there and try every possible knocking pattern until the door opens, and that would take the rest of your life, plus the rest of the lifetime of the Earth itself as well.
Incidentally, I could write the same exploit in rust or any other safe language; no language can protect against a malicious programmer.
As for detecting use of the back door, that's not entirely out of the question. However it sounds like it would not be as easy as logging every program that sshd calls exec on. But the audit subsystem should notice and record the activity for later use in your post–mortem investigation.