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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, Insightful) by Anonymous Coward on Tuesday July 04 2017, @04:02AM

    by Anonymous Coward on Tuesday July 04 2017, @04:02AM (#534678)

    Fine, as not-mechanic, you have no issue with mechanics having to dissassemble the full engine to check a small filter. It's cheap anyway.

    High logic there, the issue doesn't affect you directly, then it doesn't matter for anyone (like mechanics that like to be preventive), or even you down the road. Good luck when the fucking filter clogs and you get a huge bill because that cheap part failing cascades into more parts going bad and the engine needs a full replacement. Or the engine fails and you get run over (just in case anybody wants to play the "I don't own a car" card).

    You say that just as WannaCry, and family, is hitting multiple Windows versions all over the world. Monoculture sucks. Stupid complex design sucks. Hidding problems sucks. Decades of multiple OSes, but specially old UNIX, BSD (wars) and (the birth of) Linux have proved it. Starting by the propiertary ones, inlcuding those that provided source but didn't allow changes. Which is just what the comments about talk about, RH gives you the source but good luck changing it the cryptic mess.

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