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Date: Sun, 30 Mar 2025 23:43:26 +0200
To: Bruno Haible <bruno AT clisp DOT org>
Subject: Re: symbolic link curiousity in 3.6.0
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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Hi Bruno,

On Mar 29 15:02, Bruno Haible via Cygwin wrote:
> Corinna Vinschen wrote:
> > > Regarding what acl_extended_file() does, there is the man page by
> > > Andreas Grünbacher:
> > > https://www.kernel.org/doc/man-pages/online/pages/man3/acl_extended_file.3.html
> > > Gnulib is not the only user of acl_extended_file(); therefore I would
> > > suggest that Cygwin should follow that man page — regardless of Gnulib.
> > 
> > It already does!  The acl_extended_file() change for directories we just
> > talked about will actually be a deviation from Andreas' man page.
> 
> OK, then Cygwin's acl_extended_file should not change.

I'm not entirely sure here...

The three default perm entries are only effective outside Cygwin, so from
a POSIX point of view it's not really an extended ACL...

Btw., there's still a small bug in test-file-has-acl.sh.  It tries to
create an entry with gid 0:

  setfacl -m group:0:1 tmpfile0

But that's not possible, because there's no Windows group mapped to
uid or gid 0, unless you create your own /etc/passwd and /etc/group
files.

There's deliberately no default mapping from any Windows SID to user or
group 0, i.e., root, because there's no equivalent Windows account.
Administrator, Administrators, SYSTEM, Domain Admins, Backup Operators,
etc, etc... there's just no direct match possible, but the uid/gid must
map to a valid Windows SID.

What you can do is use group 1.  This group always exists, because
it maps to the group NT AUTHORITY\DIALUP, SID S-1-5-1.


Thanks,
Corinna


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