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posted by Fnord666 on Monday July 03 2017, @10:12PM   Printer-friendly
from the it's-a-feature dept.

Submitted via IRC for TheMightyBuzzard

A bug in Linux's systemd init system causes root permissions to be given to services associated with invalid usernames, and while this could pose a security risk, exploitation is not an easy task.

A developer who uses the online moniker "mapleray" last week discovered a problem related to systemd unit files, the configuration files used to describe resources and their behavior. Mapleray noticed that a systemd unit file containing an invalid username – one that starts with a digit (e.g. "0day") – will initiate the targeted process with root privileges instead of regular user privileges.

Systemd is designed not to allow usernames that start with a numeric character, but Red Hat, CentOS and other Linux distributions do allow such usernames.

"It's systemd's parsing of the User= parameter that determines the naming doesn't follow a set of conventions, and decides to fall back to its default value, root," explained developer Mattias Geniar.

While this sounds like it could be leveraged to obtain root privileges on any Linux installation using systemd, exploiting the bug in an attack is not an easy task. Geniar pointed out that the attacker needs root privileges in the first place to edit the systemd unit file and use it.

[...] Systemd developers have classified this issue as "not-a-bug" and they apparently don't plan on fixing it. Linux users are divided on the matter – some believe this is a vulnerability that could pose a serious security risk, while others agree that a fix is not necessary.

See, this is why we can't have nice init systems.

Source: http://www.securityweek.com/linux-systemd-gives-root-privileges-invalid-usernames


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  • (Score: 4, Interesting) by julian on Tuesday July 04 2017, @02:48AM (8 children)

    by julian (6003) on Tuesday July 04 2017, @02:48AM (#534652)

    No one ever said that good software has to be perfect.

      No one ever said that good math has to be perfect.

    ...wait, yes they do. Everyone says that. We can either start thinking of software as math, which it is, or we will have to live with these bugs forever--which is increasingly expensive not just in money but in human lives. We have the concept of provable correctness, we don't deploy it because software "engineers" are not legally responsible for their failures, unlike real engineers.

    Yes, it's enormously expensive to produce something as complex as an operating system or a browser that meets such standards. It also costs tens of millions NOT to do this. That's today. It looks like humanity is only going to become more dependent on software and networks so the cost will only increase.

    If we cared about bug-free code and side-effect free code we could work on making that easier to produce. Our economy is tooled to produce huge amounts of cheap crap that can be quickly brought to market and then obsoleted to make room for the next wave of cheap crap.

    Hazard a guess how long that can keep going? Even saying 50 years oughts you as a naive optimist. And that's not that long. I'll only be in my 70s--still bitching about this when a new firmware bug in the latest model of molecular printer allows hackers to commandeer the device and spew super-ebola into thousands of homes throughout the world.

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  • (Score: 0) by Anonymous Coward on Tuesday July 04 2017, @06:44AM (6 children)

    by Anonymous Coward on Tuesday July 04 2017, @06:44AM (#534698)

    hold on. is it even possible to demand that an operating system is proven to be bug free?
    I mean... since we know that we can write algorithms who's behavior versus their input is undecidable, and the operating system is supposed to allow that algorithm to run, how much can we prove about the behavior of the operating system?

    • (Score: 0) by Anonymous Coward on Tuesday July 04 2017, @07:11AM

      by Anonymous Coward on Tuesday July 04 2017, @07:11AM (#534708)

      We will make the BEST software. Beautiful software. You'll love it so much, you don't even know. That's the level of code quality we should aspire to.

    • (Score: 3, Touché) by maxwell demon on Tuesday July 04 2017, @08:18AM

      by maxwell demon (1608) Subscriber Badge on Tuesday July 04 2017, @08:18AM (#534725) Journal

      hold on. is it even possible to demand that an operating system is proven to be bug free?

      Bug free? Probably not. Free of terrible design decisions? Definitely.

      --
      The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 2) by fido_dogstoyevsky on Tuesday July 04 2017, @12:41PM (2 children)

      is it even possible to demand that an operating system is proven to be bug free?

      Of course - just demand it, politicians and PHBs do the equivalent all the time :)

      I mean... since we know that we can write algorithms who's behavior versus their input is undecidable, and the operating system is supposed to allow that algorithm to run, how much can we prove about the behavior of the operating system?

      We can't prove that something will always work properly. But if a potential problem is identified then it needs to be treated like a real problem. If an engineer is warned that the steel they're using in a bridge is grossly undersized would "not-a-bug" be an adequate reply?*

      *Not that it would happen very often - real engineers understand about being responsible for their work.

      --
      It's NOT a conspiracy... it's a plot.
    • (Score: 0) by Anonymous Coward on Friday July 07 2017, @03:13AM

      by Anonymous Coward on Friday July 07 2017, @03:13AM (#535984)
  • (Score: 2) by Runaway1956 on Tuesday July 04 2017, @07:09AM

    by Runaway1956 (2926) Subscriber Badge on Tuesday July 04 2017, @07:09AM (#534706) Homepage Journal

    I'm not so sure about all of that. Software is not precisely math, but an expression of things we want to do with it. Yeah, you can get a lot of your algorithms to work perfectly, and that's cool and all, but what if the algorithm doesn't do exactly what you wanted it to do? Then you tweak on it, changing the way it does things to more closely match what you wanted to do. That might be cool, but now you have a less than perfect algorithm. Throw it out? Go back to perfect? What good is perfect, if you can't get what you need from it?

    I think you need perfect people before you can get perfect software - and that ain't happening!

    --
    "no more than 8 bullets in a round" - Joe Biden