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Thread: Is the /tmp directory secure for ~/.cache?

  1. #1
    Join Date
    Sep 2011
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    30

    Is the /tmp directory secure for ~/.cache?

    Hi,

    I have a SSD, so to reduce wear I created a tmpfs in ram for /tmp and I moved my ~/.cache folder to /tmp and created a symbolic link.

    I was just wondering if there are any seurity concerns in doing this.

    The computer is a single user desktop setup, so I think in my situation there is no concerns ...

  2. #2
    Join Date
    Mar 2011
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    665

    Re: Is the /tmp directory secure for ~/.cache?

    There are probably potential security issues with this.

    I suggest you use chmod to set the folder to noexecute.

  3. #3
    Join Date
    Sep 2011
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    30

    Re: Is the /tmp directory secure for ~/.cache?

    My fstab file has this entry;

    tmpfs /tmp tmpfs nodev,nosuid,noexec,mode=1777 0 0

    So I expect this should have the same effect as chmod?

  4. #4
    Join Date
    Jun 2009
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    4,101
    Distro
    Xubuntu 13.04 Raring Ringtail

    Re: Is the /tmp directory secure for ~/.cache?

    keep in mind you will need to recreate the folder in /tmp for your cache at every boot i suggest using /etc/rc.local for this task
    like this should work nicely and be secure enough
    Code:
    mkdir /tmp/mabo-cache
    chown mabo:mabo /tmp/mabo-cache
    chmod go-rwx /tmp/mabo-cache
    Laptop: ASUS A54C-NB91 (Storage: WD3200BEKT + MKNSSDCR60GB-DX); Desktop: Custom Build - Images included; rPi Server
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  5. #5
    Join Date
    Sep 2011
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    30

    Re: Is the /tmp directory secure for ~/.cache?

    Actually, yes your right, I had problems when I created .cache in /tmp, because it's obvious to me now that it disappears after each reboot, so I just created a link between .cache to /tmp, so all the files and folders are just created in /temp rather then /temp/.cache ...

    Seems to be working ok, but was wondering if there are any security concerns ....

  6. #6
    Join Date
    Jun 2009
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    4,101
    Distro
    Xubuntu 13.04 Raring Ringtail

    Re: Is the /tmp directory secure for ~/.cache?

    like that would very likely have issues but if you use the rc.local file with those 3 lines you should be secure and have /tmp cleaner
    Laptop: ASUS A54C-NB91 (Storage: WD3200BEKT + MKNSSDCR60GB-DX); Desktop: Custom Build - Images included; rPi Server
    Putting your Networked Printer's scanner software to shame PHP Scanner Server
    I frequently edit my post when I have the last post

  7. #7
    Join Date
    Mar 2011
    Beans
    665

    Re: Is the /tmp directory secure for ~/.cache?

    When a program executes it's loaded into RAM. RAM is your executable space. By moving files into your RAM you are moving them into space that would normally be executable. Because having all RAM executable would be horribly insecure some smart guys invented NX.

    I don't know a lot about how Linux handles it let alone how the ramdisks handle it, but the big concern here is that you're loading files into an area of your machine that wants to execute. Blocking execution pretty much solves this.

  8. #8
    Join Date
    Feb 2008
    Beans
    606
    Distro
    Ubuntu 11.04 Natty Narwhal

    Re: Is the /tmp directory secure for ~/.cache?

    As suggested up above, I wrote an rc.local script which goes through all the users in /home and creates a set of directories in /tmp for cache, etc, which only have permission for that user. Then each user's home directory links to the relevant directory in there.

    It's worked fine so far.

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