From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Windows Server 2012R2 64bit and 32bit Cygwin sshd
Date: Wed, 03 Sep 2014 13:26:00 -0000 [thread overview]
Message-ID: <20140903132616.GK6056@calimero.vinschen.de> (raw)
In-Reply-To: <loom.20140903T084528-450@post.gmane.org>
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On Sep 3 07:17, Achim Gratz wrote:
> Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> > Don't use privilege separation, then the non-privileged sshd user won't
> > matter at all. Privsep on Cygwin is only half-useful on Cygwin anyway,
> > if at all.
>
> I've switched privilege separateion off completely, but no dice. The Access
> Denied comes from trying to switch from primary group "MACHINE+None" to
> "Domain Users". That is expected to happen, what I still don't get is why
> the parent process winds up with the exception instead of the originating
> process as on 64bit.
As I wrote, this is a red herring. A failing setgid is no error at
all. It has nothing to do with the exception, except for the debug
output preceeding the exception occurance. Note the
get_logon_server: DC: server: \\SC301
between them. This, and the subsequent seterrno_from_win_error in the
parent sshd are a pretty sure sign that the exception is triggered by
the NetUserXXX calls.
> > As for the local cyg_server account, I'm not sure. Usually,
> > a local machine account has no or only limited access to AD information.
> > As an account which needs AD to get user information it's a bit
> > unfortunate if it doesn't have access.
>
> When the process comes to this point it has already verified the user via AD.
Yes, but this has nothing to do with it. Before calling setuid (which
it calls a couple of times during login), sshd calls initgroups for the
new user, POSIX-like. Initgroups in turn has to call NetUserGetGroups
and NetUserGetLocalGroups on the DC to fetch the full list of groups for
a user. From the strace it *seems* that the call to NetUserGetGroups in
the grand child sshd process results in simply terminating the process.
The fact that there's no more output *at all* from the grand child
points to Windows killing the process hard. Lacking any hint why this
occurs, it's just an assumption, of course.
> > The strace shows that it doesn't even *try* to start bash, but it's
> > entirely unclear why.
>
> Is it possible to run sshd in gdb?
Yes, but Windows/Cygwin gdb don't allow to follow the child process
so it's very tricky.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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next prev parent reply other threads:[~2014-09-03 13:26 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-18 17:26 Achim Gratz
2014-08-19 13:37 ` Achim Gratz
2014-08-19 17:02 ` Corinna Vinschen
2014-08-19 17:21 ` Achim Gratz
2014-08-19 19:09 ` Corinna Vinschen
2014-08-19 19:21 ` Achim Gratz
2014-09-02 11:52 ` Achim Gratz
2014-09-02 14:07 ` Corinna Vinschen
2014-09-02 15:16 ` Achim Gratz
2014-09-02 15:38 ` Corinna Vinschen
2014-09-02 17:32 ` Achim Gratz
2014-09-03 7:17 ` Achim Gratz
2014-09-03 13:03 ` Achim Gratz
2014-09-03 13:37 ` Corinna Vinschen
2014-09-04 11:24 ` Achim Gratz
2014-09-04 12:28 ` Corinna Vinschen
2014-09-04 14:12 ` Achim Gratz
2014-09-04 14:59 ` Achim Gratz
2014-09-05 11:16 ` Corinna Vinschen
2014-09-05 11:56 ` Corinna Vinschen
2014-09-05 18:17 ` Achim Gratz
2014-09-03 13:26 ` Corinna Vinschen [this message]
2014-09-02 16:25 ` Achim Gratz
2014-09-02 19:14 ` Corinna Vinschen
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