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Re: chown/chgrp without chmod -s? lost postfix mail?



On Sun, Feb 25, 2001 at 11:45:28AM +1100, Brian May wrote:
> 
> If I had access to chgrp, then I also have access to chmod, so I don't
> see any security benifit.

yeah i don't either, i suppose if its being done through a little
shellcode exploit it would add a tad bit more difficulty in theory...  

> false sense of security? Again, if you can write to the file, chances
> are you can reset the s bit, too.

in this case perhaps not, think of a 4777 /usr/bin/passwd.  (that
would be stupid anyway but...)  

>     Ethan> in the future if you have to change this quickly do
>     Ethan> something like:
> 
>     Ethan> chgrp postdrop /usr/bin/postdrop ; chmod g+s
>     Ethan> /usr/bin/postdrop
> 
> But then you can't do
> 
> find / -gid 104 | xargs chgrp 105

yup

> so the way I see it, this "security measure" actually is a "security
> risk" because you have to replace the simple command line above with
> something more complicated that saves/restores the permissions.

good point, i agree the s removal on chown/chgrp seems largely silly,
one other argument i can think of is it avoids foot shooting in some
cases but this is unix your allowed to shoot yourself in the foot if
you wish ;-)

but in this case i think you would have to take it up with the kernel
developers or the standards people.  i know at least BSD does this too
so its not a linux specific thing by any means.  

-- 
Ethan Benson
http://www.alaska.net/~erbenson/

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