It was reported by an MS engineer who happens to be involved in another OSS project. MS is doing business with the US intelligence community, for example there is the Skype story: First, rumors that NSA offers a lot of money for people who can break Skype's E2E encryption, then MS buys Skype, then MS changes Skype's client to not be E2E encrypted any more and to use MS servers instead of peer to peer, allowing undetectable wiretapping of arbitrary connections.
But it's a quite credible story too that it was just a random discovery. Even if it was the NSA, why would they hide that capability. It doesn't take much to run a script to compare git state with uploaded source tarballs in distros like Debian (Debian has separate tarballs for the source and the source with Debian patches applied).
I view it as being OSS or postgresql dev that happens to work at microsoft. I've been doing the former for much longer (starting somewhere between 2005 and 2008, depending on how you count) than the latter (2019-12).
Perhaps you’re not familiar with what NSA historically stood for: Never Say Anything.
Let's say agency A has some scanning capability on open source software that detected this backdoor attempt by agency B. If they had gone public, agency B now knows they have this ability. So agency B will adjust their ways the next time and the scanning capability becomes less useful. While if agency A had told Microsoft to "find" this by accident, nobody would know about their scanning capability. And the next attempt by agency B would only try to avoid having the performance impact this first attempt had, probably leaving it visible to agency A.
no this engineer is world-known for being core PostgreSQL, a team with high standards.. unlike that company you mention
There's some plausible evidence here that they may've tried to use alter egos to encourage Debian to update the package: https://twitter.com/f0wlsec/status/1773824841331740708
I don't think it's plausible OSS-Fuzz could have found this. The backdoor required a build configuration that was not used in OSS-Fuzz.
I'm guessing "Jia Tan" knew this and made changes to XZ's use of OSS-Fuzz for the purposes of cementing their position as the new maintainer of XZ, rather than out of worry OSS-Fuzz would find the backdoor as people have speculated.
Had this not been discovered, the backdoored version of xz could have eventually ended up in the ubuntu version oss-fuzz uses for its docker image - and linked into all those packages being tested as well.
Except now there's an explanation if fuzzing starts to fail - honggfuzz uses -fsanitize which is incompatible with xz's use of ifunc, so any package that depends on it should rebuild xz from source with --disable-ifunc instead of using the binary package.
And if that's the case, it was sloppy of "Jia" to disable it in OSS-Fuzz and not do this:
``` __attribute__((__used__,__no_sanitize_address__)) ```
to the XZ source code to fix the false positive and turn off the compilation warning, no attention would have been drawn to this at all since no one would have to change their build script.
With or without this PR, it's very unlikely OSS-Fuzz would have found the bug. OSS-Fuzz also happens to be on Ubuntu 20. I'm not very familiar with Ubuntu release cycles, but I think it would have been a very long time before backdoored packages made their way into Ubuntu 20.
(2) they could just say they found it during some routine dependency review or whatever
Second, maybe a routine dependency review is how they _actually_ found it but they don’t want future people like this focusing too much on that otherwise they may try to mitigate, whereas now they may focus on something inane like a 0.5 second increase in sshd’s load time or whatever.
Basically "parallel construction". It's very possible it's what happened.
People love when there's some explanation that doesn't involve randomness, because with randomness looks like we don't have grasp on things.
Google actually had tooling that was detecting it, but he disabled check that would show it.
Google/Microsoft/NSA could just say they detected it with internal tooling and not disclose how exactly. Google and Microsoft would love to have credit.
https://www.cnx-software.com/2021/04/22/phd-students-willful...