From: Houder <houder@xs4all.nl>
To: cygwin@cygwin.com
Subject: Re: openssh: privilege separation no longer supported on Cygwin? SURPRISE!
Date: Mon, 29 May 2017 17:45:00 -0000 [thread overview]
Message-ID: <b16023ad6735108510ae351a8378a420@xs4all.nl> (raw)
In-Reply-To: <20e2702ca3837f5d54c558f8e786c717@xs4all.nl>
On 2017-05-29 11:48, Houder wrote:
> On 2017-05-29 10:39, Marco Atzeri wrote:
>> On 29/05/2017 07:23, Houder wrote:
>
> [snip]
>>> ... because, that is, I think, what I am seeing:
>>>
>>> - the userid of child sshd is still 'cyg_server' ...
>>> - and I get an elevated shell when I login ...
>>>
>>> Not what I expected ...
>>>
>>> Gr. Henri
>>>
>>
>> Hi Houder,
>> please read the last Announcement
>>
>> https://sourceware.org/ml/cygwin-announce/2017-03/msg00028.html
>
> [snip]
>> It seems you misunderstood the communication:
>> - the possibility to NOT use "privilege separation" is deprecated
>> - "privilege separation" will became mandatory
>
> Hi Marco,
>
> Sorry for the misunderstanding. Yes, to my knowledge, PS, privilege
> separation, is now mandatory (using a new mechanism under Linux [1]).
>
> [1] sandboxing?
>
> Because of PS, I expect to see an UNprivileged sshd process talking
> to the user process (where the ssh command has been executed).
>
> But above all, I expect an UNelevated shell when I login in ...
>
> However, what I get after login (after providing my credentials) is
> an ELEVATED shell (yes, Administrators is part of the group set).
>
> Now I wonder if this happens because I do NOT observe PS.
>
> Look below, please ... After executing the ssh command, ssh asks for
> my credentials ... in stead of providing my credentials, I execute
> the ps command in a second terminal. To my surprise, the grandchild
> of the listener is executed using "cyg_server" and not "sshd" ...
>
> Currently, I am looking at:
>
> https://cygwin.com/cygwin-ug-net/ntsec.html#ntsec-setuid-overview
... and read it MULTIPLE times! (and tried, well, about anything)
However, I found a clue here:
https://sourceware.org/ml/cygwin/2011-10/msg00035.html
(Re: admin privileges when logging in by ssh? -- by Corinna)
The thread starts here:
https://cygwin.com/ml/cygwin/2011-09/msg00138.html
(admin privileges when logging in by ssh? -- by Andrew Schulman)
Above Corinna writes:
"In all cases, password auth and passwordless auth, you should get a
full
admin token. In case of password auth and in the passwordless methods
2 and 3, the OS returns a restricted token under UAC, but ...
that token has a _reference_ to the full admin token attached.
Cygwin
fetches this token and uses that when switching the user context.
=================================================================
Oh? Ah!
The account (Henri) from which I executed the ssh command, is - yes, I
forgot to tell - , a privileged account ...
However when I login to that account, it "normally" starts an UNelevated
shell ... Not so if one executes the ssh command ... apparently.
And that is a bit of a SURPRISE ... to say the least !!!!!
Even more surprising is when I execute the ssh command from an account
that is NOT privileged (using another account, named jvdwater).
- yes. this time I get an UNelevated shell (using ssh)
- however, the userid of the grandchild of the sshd listener, is STILL
cyg_server ... NOT sshd!
As if the "sshd" account is NEVER, NEVER used during the _whole_ process
(that is, there is NO privilege separation, as far as I can tell).
Regards,
Henri
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next prev parent reply other threads:[~2017-05-29 17:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-29 6:40 openssh: privilege separation no longer supported on Cygwin? Houder
2017-05-29 9:22 ` Marco Atzeri
2017-05-29 11:39 ` Houder
2017-05-29 11:44 ` openssh: privilege separation no longer supported on Cygwin? -- example only Houder
2017-05-29 14:29 ` openssh: privilege separation no longer supported on Cygwin? Houder
2017-05-29 17:45 ` Houder [this message]
2017-05-29 20:30 ` openssh: privilege separation no longer supported on Cygwin? SURPRISE! Andrey Repin
2017-05-30 3:49 ` Houder
2017-05-30 16:16 ` Houder
2017-05-31 4:58 ` Larry Hall (Cygwin)
2017-05-31 10:51 ` Houder
2017-05-31 14:46 ` cyg Simple
2017-05-31 14:57 ` Houder
2017-05-31 14:59 ` openssh: privilege separation no longer supported on Cygwin? SURPRISE! -- minor correction Houder
2017-05-31 16:34 ` openssh: privilege separation no longer supported on Cygwin? SURPRISE! cyg Simple
2017-05-31 19:52 ` Houder
2017-05-31 20:16 ` cyg Simple
2017-06-01 2:27 ` Larry Hall (Cygwin)
2017-05-31 20:20 ` openssh: privilege separation no longer supported on Cygwin? Marco Atzeri
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