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Re: nfs_mount in AIX
From: mouse () Collatz McRCIM McGill EDU (der Mouse)
Date: Wed, 26 Apr 1995 08:04:09 -0400


It appears that the completely undocumented routine 'nfs_mount' can
be used by a non-root user to mount a daemon on a directory ala NFS.
It seems to me that this is a very nasty security hole.
Here's a little additional information.....  the nfs_mount routine
does its work through the vmount() system call, which is documented.
If this is a security hole at all, then it's because it would let an
attacker mount a remote filesystem under his control onto a
world-readable directory like /tmp or /var/preserve, and thereby grab
a copy of everything that was written to that directory.

I don't have access to AIX, so I can't read the vmount() docs, so this
may be a non-issue...but unless it enforces "nosuid,nodev" for non-root
mounts, there are much greater problems - like someone mounting a
filesystem providing suid executables, or device special files with
permissive mode bits.  (Note that if, as the first message implies,
vmount() allows the mounting of a daemon on a directory, then these
executables and/or special files do not have to actually exist
anywhere; root access on another machine is not needed.)

                                        der Mouse

                            mouse () collatz mcrcim mcgill edu



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