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Backdoor found in widely used Linux utility breaks encrypted SSH connections (arstechnica.com)

submitted 8 months ago by [email protected] to c/[email protected]

187 comments fedilink hide all child comments

The malicious changes were submitted by JiaT75, one of the two main xz Utils developers with years of contributions to the project.

“Given the activity over several weeks, the committer is either directly involved or there was some quite severe compromise of their system,” an official with distributor OpenWall wrote in an advisory. “Unfortunately the latter looks like the less likely explanation, given they communicated on various lists about the ‘fixes’” provided in recent updates. Those updates and fixes can be found here, here, here, and here.

On Thursday, someone using the developer's name took to a developer site for Ubuntu to ask that the backdoored version 5.6.1 be incorporated into production versions because it fixed bugs that caused a tool known as Valgrind to malfunction.

“This could break build scripts and test pipelines that expect specific output from Valgrind in order to pass,” the person warned, from an account that was created the same day.

One of maintainers for Fedora said Friday that the same developer approached them in recent weeks to ask that Fedora 40, a beta release, incorporate one of the backdoored utility versions.

“We even worked with him to fix the valgrind issue (which it turns out now was caused by the backdoor he had added),” the Ubuntu maintainer said.

He has been part of the xz project for two years, adding all sorts of binary test files, and with this level of sophistication, we would be suspicious of even older versions of xz until proven otherwise.

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[–] [email protected] 2 points 8 months ago (1 children)

I would highly recommend Curve25519, etc., just because such keys are faster and less common than RSA public-private keys in today's world. RSA 2048-bit keys are considered weak today, while the Curve25519 256-bit keys remain stronger. Also, the ChaCha20-Poly1305 cipher has an interesting backstory and doesn't necessarily need hardware acceleration (which, in theory, could be borked by the HW-vendor) to obtain good performance.

Unfortunately, some SSH front-ends don't play nice with Curve25519 public-private keys yet... (I'm pointing at the putty SSH client, but that may have improved from the last time I had to use it)

[–] [email protected] 6 points 8 months ago

It would be Ed25519 for SSH:

$ ssh-keygen -t ed25519