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.
Backdoors at a mation-state level are a double edged sword. In order to successfully implement a backdoor, you need to ensure that you are more clever than your adversaries, because those same backdoors can be used against you. You must assume that they will eventually discover them, and be able to leverage them against you. Then you must be able to identify that it had been compromised, and then “responsibly disclose” the vulnerability before too much damage is done.
Much better to be on the defensive. Discover 0days first, either accidental or intentional, and then use them until someone else discloses them and they get patched to hell.
In this instance, that’s not the case. Only those in possession of the right key can use the backdoor. Also, discovering infected systems from the outside, appears to be impossible - the backdoor simply does not do anything to reveal itself if you don’t have the key.
I must be mistaken then. I suppose keys have never, ever been compromised. Nobody has ever taken sensitive information without authorization, either. Especially not from the NSA!
You were talking about adversaries discovering the backdoor. That’s something entirely different from compromised keys. So your sacrasm is quite misplaced here.
Columbus “discovered” America.