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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.


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  • (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.
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  • (Score: 3, Interesting) by mcgrew on Tuesday July 04 2017, @05:33PM (1 child)

    by mcgrew (701) <> on Tuesday July 04 2017, @05:33PM (#534849) Homepage Journal

    Measure with a micrometer, mark with chalk and cut with a chain saw.

    Free Martian whores! []