Re: Help! File permissions keep changing...
On Wed, 18 Feb 2004 23:59, Javier Fernández-Sanguino Peña <jfs@computer.org>
wrote:
> On Wed, Feb 18, 2004 at 11:05:30AM +0100, Richard Atterer wrote:
> > Waaaaaah, SCARY!
> >
> > Users can create hard links to arbitrary files in that directory, e.g.
> > links to other users' private files or to /etc/shadow, and automatically
> > get read access to those files.
>
> That is, of course, if the partitions in the system have not been setup
> properly. I assumed they were ok, he _did_ say that he was changing file
> permissions and owners manually.
Regardless, you will still have the same problem if a user creates hard links
to files owned by another user (presuming that you don't have a mount point
per user or a file system such as NFS that doesn't support hard-links).
As I recall this entire discussion started with users who didn't know how to
manage their own permissions, so presumably they make their home dir mode 755
or worse on occasion...
Even if the users' home dirs are mode 711 (fairly common when web servers and
other daemons want to read sub-dirs of the user's home dir) that will still
allow hard links to known files such as ~/.login, ~/.bashrc, etc. Take over
one of those files and taking over the entire account becomes trivial.
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