From: "Chris J. Breisch" <chris.ml@breisch.org>
To: cygwin@cygwin.com
Subject: Re: Microsoft Accounts (was Re: Problem with "None" Group on Non-Domain Members)
Date: Wed, 07 May 2014 14:05:00 -0000 [thread overview]
Message-ID: <536A3DA3.8060508@breisch.org> (raw)
In-Reply-To: <20140507115730.GE30918@calimero.vinschen.de>
Corinna Vinschen wrote:
> On May 6 14:22, Chris J. Breisch wrote:
>> Corinna Vinschen wrote:
>>> On Windows, users and groups are identified not by uid/gid, but by
>>> their SID. The SID is a unique value, but other than that, a SID can
>>> be a user or a group and in lots of cases Windows doesn't care.
>>> A group can be owner of a file and a user can be the group of the file,
>>> it just doesn't matter to Windows.
>>>
>>> The permission "problem" you're seeing is a result of that. Your user
>>> *and* your primary group are both your user's SID. Therefore the same
>>> account is user and primary group at the same time. Therefore, if
>>> the file is created, it gets created with an ACL with user and group
>>> being the same account. Therefore the POSIX translation of the user
>>> and group permissions on the file are always the same.
>>>
>>> Does this clear it up?
>> Yes, that makes complete sense. Thank you again.
>
> I toyed around with the Microsoft Account a bit more. And here's why
> the primary group SID being identical to the user SID is not a good
> idea:
>
> Security checks.
>
> For instance:
>
> $ echo $USER
> VMBERT8164+local_000
> $ screen
> Directory /tmp/uscreens/S-VMBERT8164+local_000 must have mode 700.
>
> Huh?
>
> $ ls -l /tmp/uscreens/
> total 0
> drwxrwx---+ 1 VMBERT8164+local_000 VMBERT8164+local_000 0 May 7 12:44 S-VMBERT8164+local_000
>
> Uh Oh.
>
> This will be a problem with other security sensitive applications, too.
> Sshd comes to mind.
>
Yes, it was when dealing with ssh that I discovered this issue, and was
the reason I brought it up. Ssh wants many of its files to be only
accessible by the owner, and not any group.
> So I guess we really should make sure the primary group SID is some
> valid group, not the user's SID.
>
> "None" is not an option since it's not in the user token group list.
>
> "Users" seems to be the best choice at first sight.
>
That's what I've thought from the beginning.
> Alternatively we could use the S-1-11-xxx SID of the Microsoft Account.
> That would be in line with the idea to have a user-specific primary
> group.
>
I'm not sure how that helps or even would work. Are you talking about
creating a group just for Cygwin purposes that wouldn't map to an actual
group on the box? Seems like I need to get some more caffeine and go
back and reread your attached document from several messages ago.
> Thoughts?
>
>
> Corinna
>
--
Chris J. Breisch
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next prev parent reply other threads:[~2014-05-07 14:05 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-05 13:49 Problem with "None" Group on Non-Domain Members Chris J. Breisch
2014-05-05 13:59 ` Corinna Vinschen
2014-05-05 14:17 ` Chris J. Breisch
2014-05-05 14:47 ` Corinna Vinschen
2014-05-05 15:23 ` Chris J. Breisch
2014-05-05 15:42 ` Corinna Vinschen
2014-05-05 16:17 ` Chris J. Breisch
2014-05-05 16:57 ` Corinna Vinschen
2014-05-05 18:52 ` Robert Pendell
2014-05-06 13:02 ` Corinna Vinschen
2014-05-05 18:56 ` Chris J. Breisch
2014-05-05 19:44 ` Larry Hall (Cygwin)
2014-05-05 21:57 ` Chris J. Breisch
2014-05-05 22:07 ` Chris J. Breisch
2014-05-05 22:29 ` Larry Hall (Cygwin)
2014-05-05 22:39 ` Chris J. Breisch
2014-05-06 0:43 ` Larry Hall (Cygwin)
2014-05-06 12:23 ` Chris J. Breisch
2014-05-05 22:09 ` Larry Hall (Cygwin)
2014-05-06 12:52 ` Microsoft Accounts (was Re: Problem with "None" Group on Non-Domain Members) Corinna Vinschen
2014-05-06 12:55 ` Corinna Vinschen
2014-05-06 13:01 ` Corinna Vinschen
2014-05-07 12:26 ` vlado99
2014-05-07 12:43 ` Corinna Vinschen
2014-05-06 17:01 ` Chris J. Breisch
2014-05-06 17:16 ` Corinna Vinschen
2014-05-06 18:22 ` Chris J. Breisch
2014-05-07 11:57 ` Corinna Vinschen
2014-05-07 12:40 ` Corinna Vinschen
2014-05-07 14:09 ` Chris J. Breisch
2014-05-07 14:46 ` Corinna Vinschen
2014-05-08 20:09 ` Corinna Vinschen
2014-05-08 23:18 ` Robert Pendell
2014-05-09 0:12 ` Ken Brown
2014-05-09 1:34 ` Robert Pendell
2014-05-09 6:11 ` Achim Gratz
2014-05-09 7:42 ` Corinna Vinschen
2014-05-07 14:05 ` Chris J. Breisch [this message]
2014-05-07 14:35 ` Corinna Vinschen
2014-05-07 14:05 ` Andrey Repin
2014-05-07 14:20 ` Corinna Vinschen
2014-05-07 14:43 ` Corinna Vinschen
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