root permissions

[aleph1 () panacea library ucsb edu (Aleph One)]

        Well, this is not a bug but a question on
the design of most Unix systems. It seams to me, and
I tried this on Ultrix 4.3, HPUX 9.01, Linux 1.1.x,
when root opens a file, being the owner or not, the 
system does not check the  file permissions before
granting him access. The same goes for writting and
unlinking a file.

        I belive this is wrong. Root should always be
allowed to chmod a file is he needs to, but granting
access without checking file permissions is bad. If
this were not so, bugs on suids programms that only
allow the attacker to write to a file could be made
to fail. For example just make /etc/paswd, or /.rhost
chmod a-w, and the attacker cant write to them even
with root permissions. Of curse root can always chmod
them when hes making a change, and then chmod them back.

        Any comments on this? If you feell bugtraq is
not the apropiate place to talk about design place
direct me to a better place.

a1
http://dfw.net/~aleph1