bug#865: 23.0.60; The directory is unsafe today

[Jason Rumney]

Eli Zaretskii wrote:

> The current lie is relatively small: it is limited to the
> interpretation of the group ID, while the owner of the file is
> displayed and interpreted correctly.
>
>   
> > If we are going to attempt this, then it is better to tell a lie
> > that fits with the expectations of POSIX (ie that owners of files
> > are individual users).
> >     
>
> The problem is, I don't see how we can do this reliably.  In this
> particular case, Emacs compares the file's ownership with the UID of
> the user running Emacs, so we could pretend the file is owned by that
> user.  But in other cases, Emacs could compare the ownership to a UID
> of some other user, and what will we do then?
>   

I can't imagine any Lisp code doing this, as it will not know which 
other users are on the system. The only use for checking the owner seems 
to be to check if the current user is the owner. Rather than a 
technically correct mapping of ownership to groups, I think it is better 
for users if the mapping reflects whether the current user has ownership 
(individually or through a group they are a member of) so that such 
binary tests can work.