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Systemd-resolved Subject to Cache Poisoning

posted by n1 on Thursday November 13 2014, @03:19AM   Printer-friendly
from the one-daemon-to-rule-them-all dept.

DECbot writes:

Whether you're running systemd happily or begrudgingly, it's best if you disable systemd-resolved as your DNS resolver for the time being. Reported today at seclists is a new DNS cache poisoning bug in systemd-resolved.

At its simplest, an attacker triggers a query to a domain he controls via SMTP or SSH-login. Upon receipt of the question, he can just add any answer he wants to have cached to the legit answer he provides for the query, e.g. providing two answer RR's: One for the question asked and one for a question that has never been asked - even if the DNS server is not authoritative for this domain.

Systemd-resolved accepts both answers and caches them. There are no reports as to the affected versions or how widespread the problem may be. Comments over at Hacker News suggests that it might not be widespread, most users would still be running the backported 208-stable while the DNS resolver was committed in 213 and considered fairly complete in 216, but that is if they enabled systemd-resolved in /etc/nsswitch.config.

 
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  • (Score: 3, Informative) by LoRdTAW on Thursday November 13 2014, @01:02PM

    by LoRdTAW (3755) on Thursday November 13 2014, @01:02PM (#115518) Journal

    It's a chicken or the egg problem. As another poster mentioned, they are moving towards a managed service system like Windows svchost. The problem though, is if you make a switch to such a radically different service manager, where do the daemons come from?

    And this is why systemd has to reinvent the wheel and reimplement so many services that already exist under linux. In order for there to be a useful systemd they have to write systemd services. Everyone still thinks it is simply trying to be a PID1 and init system, it isn't. It is a entire suite of replacement daemons and one process to rule them all.

    A comparison: If you use Windows go to control panel and administrative tools. Then open services. Pretend services is systemd and all the services listed within are systemd-daemons. That is exactly what systemd is and what is wants to become.

    Have a look at the opening summary for svchost on wikipedia (https://en.wikipedia.org/wiki/Svchost.exe [wikipedia.org]):

    In the Windows NT family of operating systems, svchost.exe (Service Host, or SvcHost) is a system process that hosts multiple Windows services. Svchost is essential in the implementation of so-called shared service processes, where a number of services can share a process in order to reduce resource consumption. Grouping multiple services into a single process conserves computing resources, and this consideration was of particular concern to NT designers because creating Windows processes takes more time and consumes more memory than in other operating systems, e.g. in the Unix family. However, if one of the services causes an unhandled exception, the entire process may crash. In addition, identifying component services can be more difficult for end users. Problems with various hosted services, particularly with Windows Update, get reported by users (and headlined by the press) as involving svchost.

    I am not pretending to be an OS expert, but just the opening of the article makes the idea of systemd sound silly.

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  • (Score: 0) by Anonymous Coward on Thursday November 13 2014, @09:15PM

    by Anonymous Coward on Thursday November 13 2014, @09:15PM (#115665)

    Those who don't understand UNIX^W Linux are doomed to re-invent it--poorly.

    -- gewg_

    • (Score: 2) by LoRdTAW on Friday November 14 2014, @05:25PM

      by LoRdTAW (3755) on Friday November 14 2014, @05:25PM (#115961) Journal

      Actually, it should read:
      Those who do not understand Windows are condemned to reinvent it, poorly.