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Date: Mon, 12 May 2008 19:20:26 -0400 (EDT)
From: Igor Peshansky <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: "Schutter, Thomas A." <tschutter AT proxix DOT com>
cc: cygwin AT cygwin DOT com
Subject: RE: Unable to run sshd under a domain sshd_server account [SOLVED]
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On Mon, 12 May 2008, Schutter, Thomas A. wrote:

> > -----Original Message-----
> > From: Igor Peshansky
> > Sent: Monday, May 12, 2008 4:30 PM
> > To: Schutter, Thomas A.
> > Subject: RE: Unable to run sshd under a domain sshd_server account
> [SOLVED]
> >
> > On Mon, 12 May 2008, Schutter, Thomas A. wrote:
> >
> > > > -----Original Message-----
> > > > From: Schutter, Thomas A.
> > > > Sent: Monday, May 12, 2008 9:52 AM
> > > > To: 'cygwin AT XXXXXX DOT XXX'
> >
> > <http://cygwin.com/acronyms/#PCYMTNQREAIYR>.
> >
> > > > Subject: Unable to run sshd under a domain sshd_server account
> > > >
> > > > I am having problems setting up sshd to run under a domain
> > sshd_server
> > > > account instead of a local sshd_server account.
> > > > [snip]
> > > > But when I login via ssh:
> > > >   $ echo $USER
> > > >   tschutter
> > > >   $ echo $USERNAME
> > > >   sshd_server
> >
> > Yes -- Windows does not understand user impersonation and does not
> > allow real user switching.  So what sshd does is invoke processes with
> > the appropriate token privileges for the user it's impersonating,
> > while updating internal Cygwin data structures, but still running as
> > sshd_server.  So Cygwin sees the right user (in its internal state),
> > but Windows processes, of course, don't.
>
> Interesting.  I suspected this, but this is the first time that I have
> seen this explicitly stated.

Well, at least Windows processes don't understand the Cygwin notion of
effective UID, which is why $USERNAME and $USER don't match (one is set by
Windows, and the other by a Cygwin process -- bash).

> > > > The application event log has this error message:
> > > >   The description for Event ID ( 0 ) in Source ( sshd ) cannot be
> > > > found. The local computer may not have the necessary registry
> > > > information or message DLL files to display messages from a remote
> > > > computer. You may be able to use the /AUXSOURCE= flag to retrieve
> > > > this description; see Help and Support for details. The following
> > > > information is part of the event: sshd: PID 2068: service `sshd'
> > > > failed: signal 11 raised.
> >
> > Oops -- a segfault.  This is definitely a bug somewhere -- no matter
> > what, sshd should not segfault.
>
> Agreed.

Those problems are usually very hard to reproduce.  If you're set up to
build a debug version of sshd and run it under gdb to reproduce the fault,
a stack backtrace would be helpful.

> > > In the other thread, Larry Hall pointed me to the FAQ
> > > http://cygwin.com/faq/faq-nochunks.html#faq.using.shares. One of the
> > > suggestions was to "provide your password to a net use command".  I
> > > was unable to make that work, because "net use" never asks for my
> > > password:
> > >   $ net use \\other\f$
> > >   System error 67 has occurred.
> > >
> > >   The network name cannot be found.
> >
> > See "net help use":
> >   The syntax of this command is:
> >   NET USE
> >   [devicename | *] [\\computername\sharename[\volume] [password | *]]
> > ...
> >   password         Is the password needed to access the shared
> > resource.
> >   *                Produces a prompt for the password. The password is
> >                    not displayed when you type it at the password
> > prompt.
> >
> > So, you need to type "net use '\\other\f$' \*" (note the
> escaped/quoted
> > '*'), and it'll prompt you for the password.
>
> OK.  So on a console cygwin shell:
>   $ net use '\\other\f$'
>   The command completed successfully.
>
> But when run in a ssh shell (using the sshd_server account):
>   $ net use '\\other\f$' \*
>   Type the password for \\zoom\f$: System error 1326 has occurred.
>
>   Logon failure: unknown user name or bad password.

Umm, yes.  Sorry.  I forgot that sshd runs in a pty, which is a pipe as
far as Windows is concerned.  And 'net' cannot read the password from a
pipe...

> Same thing happens with:
>   $ net use '\\other\f$' '*'
>   $ net use '\\other\f$' "*"

Actually supplying the password instead of '*' should work.
	Igor
-- 
				http://cs.nyu.edu/~pechtcha/
      |\      _,,,---,,_	    pechtcha AT cs DOT nyu DOT edu | igor AT watson DOT ibm DOT com
ZZZzz /,`.-'`'    -.  ;-;;,_		Igor Peshansky, Ph.D. (name changed!)
     |,4-  ) )-,_. ,\ (  `'-'		old name: Igor Pechtchanski
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

"That which is hateful to you, do not do to your neighbor.  That is the whole
Torah; the rest is commentary.  Go and study it." -- Rabbi Hillel

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