Slashdot Mirror


Abusing Symbolic Links Like It's 1999

An anonymous reader writes with this snippet from James Forshaw's recent post at Google's Project Zero, which begins For the past couple of years I've been researching Windows elevation of privilege attacks. This might be escaping sandboxing or gaining system privileges. One of the techniques I've used multiple times is abusing the symbolic link facilities of the Windows operating system to redirect privileged code to create files or registry keys to escape the restrictive execution context. Symbolic links in themselves are not vulnerabilities, instead they're useful primitives for exploiting different classes of vulnerabilities such as resource planting or time-of-check time-of-use. Click through that link to see examples of this abuse in action, but also information about how the underlying risks have been (or can be) mitigated.

14 of 54 comments (clear)

  1. we can fix this by Gravis+Zero · · Score: 3, Funny

    it seems to me that we can stop shit commercial software from being published if governments set up a mandatory bug bounty systems. it's simple, you demo the exploit and get money based on the severity and the company making the software must pay it and has X days to fix it before paying the fine again. this would result in either better education on how to find exploits, better Q/A mechanism or companies going under. frankly, i don't care which happens as long as commercial software is held accountable for bad code.

    --
    Anons need not reply. Questions end with a question mark.
    1. Re:we can fix this by Calydor · · Score: 5, Insightful

      The end of your post combined with your signature is comedy gold, mate.

      --
      -=This sig has nothing to do with my comment. Move along now=-
    2. Re:we can fix this by RabidReindeer · · Score: 4, Funny

      Hey! Our product line is created, maintained and supported by the finest professionals $1.75/hour can buy!

    3. Re:we can fix this by sjames · · Score: 2

      Because if it's gratis there is no implied warranty of merchantability. If it's proper Free software (not tivoized), anyone can fix the bug.

      If it's proprietary, there are implied warranties on it and only the creator has the source needed to fix it.

    4. Re:we can fix this by fraxinus-tree · · Score: 2

      Good luck imposing this. You will simply kill the proprietary software in this jurisdiction.

    5. Re:we can fix this by bmo · · Score: 5, Informative

      If it's proprietary, there are implied warranties on it

      Since when?

      Microsoft excludes all implied warranties and conditions, including those of merchantability, fitness for a particular purpose, and non-infringement.

      Bolded in the eula itself.

      --
      BMO

    6. Re:we can fix this by bmo · · Score: 2

      https://www.microsoft.com/en-u...

      Forgot to put in the web page.

      --
      BMO

    7. Re:we can fix this by Zontar+The+Mindless · · Score: 3

      You will simply kill the proprietary software in this jurisdiction.

      You say this as though it's a bad thing...

      --
      Il n'y a pas de Planet B.
  2. Re: MS is still 20 years behind. This will remain by Anonymous Coward · · Score: 3, Insightful

    Why have paid QA when your customers have proven over and over again that they'll still buy your software no matter how buggy it is? Thompson isn't that bright, and got his job just because of his race, but he isn't stupid.

  3. You want me to what now? by Daetrin · · Score: 4, Funny

    [This person is an expert at hacking systems using links!]

    "Click through that link to see examples of this abuse in action"

    o_O

    (And yes, i'm aware that URL links are not the same as symbolic links, but the phrasing is still amusing.)

    .

    --
    This Space Intentionally Left Blank
  4. Windows uses a unix file hierarchy by innocent_white_lamb · · Score: 3, Informative

    I never realized that Windows uses a unix-like file hierarchy.

    According to the article, drive C: is actually a symbolic link to \Device\HarddiskVolume4, COM3 is \Device\Serial0 and so on.

    I'm surprised, frankly. My exposure to Windows is pretty much nil (and I like it that way) but I always assumed that the the C: drive and COM: stuff was a completely different way of accessing the devices and whatnot than what Unix uses. Apparently, it's actually quite similar once you get under the hood.

    Learn something new every day....

    --
    If you're a zombie and you know it, bite your friend!
  5. As the old saying goes... by turbidostato · · Score: 4, Insightful

    On proper time Windows has added symlinks, a (somehow) worthwhile command line, non-graphic environment, the ability to remotely manage, declarative-based configuration management...

    It's only they are reinventing all these things on their own, forgetting about how did they came to be and, of course, not caring about the way those facilities have been used and abused in the past.

    I think it was Henry Spencer the one that said "Those who do not understand Unix are condemned to reinvent it, poorly."

    1. Re:As the old saying goes... by lucm · · Score: 4, Funny

      On proper time systemd has added symlinks, a (somehow) worthwhile command line, non-graphic environment, the ability to remotely manage, declarative-based configuration management...

      It's only they are reinventing all these things on their own, forgetting about how did they came to be and, of course, not caring about the way those facilities have been used and abused in the past.

      I think it was Henry Spencer the one that said "Those who do not understand Unix are condemned to reinvent it, poorly."

      Hehe

      --
      lucm, indeed.
  6. Re:Just like systemd and /etc/resolv.conf? by Zontar+The+Mindless · · Score: 2

    systemd is responsible for that mess?

    Before learning about this, I merely *disliked* systemd.

    But now...?

    KILL IT WITH FIRE!!!

    --
    Il n'y a pas de Planet B.