Re: FD/overwriting suid files

[iceman () MBnet MB CA (Oliver Friedrichs)]

On Mon, 13 Feb 1995, Nathan Lawson wrote:

> I always have thought that any good OS will reset any suid/sgid bits on a file
> write.  Such is the case for the Solaris 2.4 machine I tested this on.  I think
> any OS that doesn't do this has some deep design flaws.

This isn't the case for the superuser.

# touch s
# chmod 4755 s
# ls -l s
-rwsr-xr-x   1 root     other          0 Feb 13 23:27 s
# cp /bin/sh s
# ls -l s
-rwsr-xr-x   1 root     other      85924 Feb 13 23:27 s
#

It also doesn't apply to the superuser writing to setuid files owned by 
anyone else.  This is rightly so, since root could do whatever it wanted 
anyways.

- Oliver