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utzoo!decvax!ucbvax!unix-wizards utzoo!decvax!ucbvax!unix-wizards
Wed Sep 9 22:21:20 AEST 1981


>From mhtsa!chico!esquire!nrh at Berkeley Wed Sep  9 22:15:40 1981
A recent netnews item mentioned that Berkeley's vmunix turned off the
setuid bit on a file when that file was modified.
The item suggested that this solved a security problem with v7 mail.

I sent a reply to this item, but it seems to have gotten lost.  Try
again.....

One thing I learned from v6 unix:  An OS that does:

	1. What you tell it to do
	2. \ONLY/ what you tell it to do

is orders of magnitude more usable than one which tries to protect you 
from yourself.  In my (limited) experience, the ones that try to 
protect you mostly manage to protect you from doing any useful work.
Turning off setuid when the ownership is changed by a non-su is 
necessarily in the kernal.

Turning off setuid when the file is modified is "protecting the
programmer from his own foolishness", and could be done in a
library routine, rather than in the kernal. 

One last bit of sour grapes:  the message about Berkeley's mod
said that the kernal change is "simple".  Pfui. It doesn't matter
how simple the mod is if it doesn't belong in the kernal.



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