Hans-Christoph Steiner @eighthave@librem.one
Joined Aug 2019
Hans-Christoph Steiner
boosted
Some thoughts about attribution in the XZ backdoor, having just wasted so many hours digging into the details.
The email addresses used for a couple of years at least by the parties involved have absolutely *zero* trace in any kind data breach or database beyond Github/Gitlab, and maybe Tukaani and Debian and a few mailing lists.
Normally when I see this, the assumption is that we're dealing with a single-use or single-purpose email address that was created either for fraud or b/c someone is super paranoid about privacy.
The people in the latter camp who do this tend to have other tells that give them away, or at least *some* trace or home base in the online world. Especially if we're talking on the order of years using that address.
Either way, very few people do opsec well, and for every year you're operating under the same name, nick, number, email, etc you dramatically increase the risk of screwing up that opsec. And almost everyone does, eventually.
To see this complete lack of presence in breached databases once or twice in the course of an investigation is rare, but to find it multiple times suggests we're dealing with an operation that was set up carefully from the beginning. And that almost certainly means a group project (state-sponsored).
A popular dev culture these days is bult on always pulling in the latest library #updates whenever possible. There can be good reasons to do that but new library code must still be reviewed. Or at least, confirm that the maintainers have been doing that, and still are. If you've even been through a code audit, it becomes crystal clear that dependencies are part of the #security profile. #Debian provides another layer of review. I use deps from Debian and review when updating packages, to share.
@nazokiyoubinbou I agree it is a red flag, but it is also perfectly normal for people to want their changes to be merged, especially when they are doing it on a volunteer basis and they want to wrap up that piece of work. Software is so often a rabbit hole that can easily suck down all your time. That's why this is a vulnerability. Developers understand that people want things merged, and it is generally worthwhile to merge improvements if they don't cause problems, even if they are not "done".
@kuketzblog @IzzyOnDroid the #FDroid implementation that checks usesCleartextTraffic and cleartextTrafficPermitted is here:
https://gitlab.com/fdroid/issuebot/-/commit/cd76b15fd6be063fdb614040a26dfe5801629c0a
3/3
@kuketzblog @IzzyOnDroid thanks for the prompt, we just merged related work. Issuebot now reports service intent-filters and checks cleartextTrafficPermitted. `fdroid build` blocks APKs with testOnly. You might be interested in the <meta-data> check in issuebot. For many cases, API key configs are by far the most reliable way to spot that a tracking or proprietary library is actually enabled in the app, and not just accidentally included. <meta-data> fields are tracked in Exodus ETIP.
2/
Nice idea to check usesCleartextTraffic, but that particular check isn't worth much since, as the docs say:
> This flag is ignored on Android 7.0 (API level 24) and above if an Android Network Security Config is present.
Sounds like the IzzyOnDroid scanner would not catch `android:usesCleartextTraffic="false"` then in the Network Security Policy, sets `<base-config cleartextTrafficPermitted="true" />`. From what I've seen, most apps use Network Security Policy anyway.
1/
Hans-Christoph Steiner
boosted
First more detailed analysis of the backdoor AFAIK, in this Bluesky thread: https://bsky.app/profile/did:plc:x2nsupeeo52oznrmplwapppl/post/3kowjkx2njy2b
So the backdoor’s intention isn’t compromising SSH sessions but rather executing arbitrary code on vulnerable Linux servers. The payload is hidden within the RSA key sent to the SSH server during authentication. This payload has to be signed with some unknown Ed448 key which only the attackers possess. If the signature is deemed correct, the payload is passed to system() (executes it as a shell command). Otherwise the code falls back to the default SSH behavior.
Had this backdoor been discovered a few months later, we would now have a lot of vulnerable servers all over the world. And only the attackers would be able to detect from outside which ones are vulnerable, because only they can send a correctly signed payload that would trigger command execution.
Planting a command execution backdoor into most Linux servers out there sounds too ambitious for someone driven by monetary interests, there are simpler ways to build a botnet. The level of sophistication and long-term planning indicates a state-level actor. Unfortunately, there isn’t a shortage of candidates. With quite a few Western governments pushing for lawful interception lately, I wouldn’t rule out any country at this point.
Hans-Christoph Steiner
boosted
It is now possible to re-order the position of repositories in the list. The repo at the top has the highest priority while the repo at the bottom has the lowest priority. Only if an app is available from more than one repo, the priority matters.
For example, if NewPipe's repo was added and the user always wants to prefer apps from that repo, they can move it to the top. In older versions of F-Droid, newly added repos were implicitly granted higher priority than repos added before.
Hans-Christoph Steiner
boosted
If the app is available from more than one repository, the box in the app details screen becomes a drop-down where the user can see all repos and choose which one should be used for installation, updates and app information.
Hans-Christoph Steiner
boosted
When tapping an app, the user sees the app details screen as usual. There, a new box at the top shows the repository the app comes from.
All information on that page including the versions provided for installation are provided by that repo.
Hans-Christoph Steiner
boosted
Version 1.20 of @fdroidorg brings some pretty big changes of how repositories are handled:
• official repo is always preferred
• the repo an app comes from is prominently shown
• if an app is available from more than one repo, they can choose where to get it from
• power users can change global repo priorities
Hans-Christoph Steiner
boosted
If you did not yet opt-in to beta versions of F-Droid, please manually install 1.20 and help testing before we make it available for everyone.
@cratermoon @timbray sounds worthwhile to me, there are so many compression libs out there
Hans-Christoph Steiner
boosted
Are you experienced with GTK and Rust ? 
❤️ 
We are looking to contract someone to work on the new GNOME Password Manager 🔑
We want it to become a core/default app and help secure millions of users.
You'll be working with the GNOME Foundation, a non-profit dedicated to building emancipatory technologies for everyone.
Please send resume / portfolio to stf@gnome.org
Boosts welcome 
#GTK #Rust #rustlang #GNOME #Linux #Ubuntu #Linux #Fedora #OpenSUSE #Debian
Hans-Christoph Steiner
boosted
Its also kinda enlightening on how distros react to the #xz backdoor:
* #arch "lets rerelease the version from the untrusted party, we run autogen.sh ourselves now"
* #debian "lets roll back to the last version not having any changes by the untrusted party and rebuild our infra from scratch"
I know which of these I trust more as an upstream ...
Hans-Christoph Steiner
boosted
@selectallfromdual Latest F-Droid Client 1.20 alpha (expand Versions to install) redesigned the repo section. Feedback is welcome.
@WPalant Because the submitter deleted their account as a response to the review, I think it could be an deliberate attempt to insert the vuln. Plus all the attention from random new accounts. If it had been a normal review process, I could see how it could have been an honest mistake. But that scenario also makes it more attractive to the attacker, since making a mistake there is quite plausible, and could serve as an easy cover story.
@WPalant Ironically, it could be because I was so aware of the crappy state of things that I caught this. The author of the SQL code was no longer involved. I suck at SQL but was well aware that string concat to build SQL queries is a bad idea. So I was terrified to merge any changes to the SQL without really confirming them.
In any case, we've since replaced all that crazy code with libraries that provide much more protection.
@Optional clear communication definitely suffers when maintainers are overloaded, stressed out and feel ganged up on. I think that's another key takeaway from this current incident. For a well resourced actor, it is not too hard to social engineer themselves into a trusted position when projects get into that position. That happens all too often, unfortunately.
@atrus @joeyh I think a more useful and realistic takeaway from the #xz #backdoor is that build systems should be clean, direct, simple, and easily readable. A key part was the m4 code in the build system that read the payload from the obfuscated test file. If the build system was easy to read, then it would have been a lot harder to do that.
Joined Aug 2019
