OpenSSH: SSHD daemon (as SYSTEM) is partially broken

OpenSSH: SSHD daemon (as SYSTEM) is partially broken

[n0nc3]

It appears Cygwin SSHD's functionality is partially broke in the later
versions, where SSHD runs as SYSTEM (no longer cyg_server).

On reboot, any attempt to SSH into the server *before* any previous logon
attempt (RDP/locally/etc) is quickly denied:

   debug1: Offering public key: /home/<user>/.ssh/id_rsa
   debug3: send_pubkey_test
   debug2: we sent a publickey packet, wait for reply
   Connection closed by <server_addr>
   
Once an RDP/local login is attempted, regardless of success/failure,
subsequent ssh attempts will progress to the password prompt which
eventually gets us in.

The Event Viewer shows the attached error message, relating to a NULL SID
and 0xC00000BB status.
ssh_as_first_login.txt
<http://cygwin.1069669.n5.nabble.com/file/t11987/ssh_as_first_login.txt>  

It was a rather vanilla 'ssh-host-config' run to get it installed: strict
modes = no, no special ssh_/sshd_config settings at this point.

Running latest cygwin packages on Windows Server 2016 Standard:
CYGWIN_NT-10.0 <server_name> 3.1.4(0.340/5/3) 2020-02-19 08:49 x86_64 Cygwin
...
openssh              8.2p1-1            OK



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Re: OpenSSH: SSHD daemon (as SYSTEM) is partially broken

[Bill Stewart]

On Thu, Feb 27, 2020 at 11:09 AM n0nc3 <pkoshar@compunetix.com> wrote:

It appears Cygwin SSHD's functionality is partially broke in the later
> versions, where SSHD runs as SYSTEM (no longer cyg_server).
>
> On reboot, any attempt to SSH into the server *before* any previous logon
> attempt (RDP/locally/etc) is quickly denied:
>
>    debug1: Offering public key: /home/<user>/.ssh/id_rsa
>    debug3: send_pubkey_test
>    debug2: we sent a publickey packet, wait for reply
>    Connection closed by <server_addr>
>
> Once an RDP/local login is attempted, regardless of success/failure,
> subsequent ssh attempts will progress to the password prompt which
> eventually gets us in.
>

This is a known issue on OS versions older than 8.1.

See thread starting with this message:

https://cygwin.com/ml/cygwin/2019-03/msg00087.html

My proposed workaround is this:

https://cygwin.com/ml/cygwin/2019-03/msg00113.html

Bill

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Re: OpenSSH: SSHD daemon (as SYSTEM) is partially broken

[TestUser1]

So is this expected to work fine in my environment, Windows Server 2016 (OS
Version 10.0.14393), without the workaround?

Thanks!



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Re: OpenSSH: SSHD daemon (as SYSTEM) is partially broken

[Bill Stewart]

On Thu, Feb 27, 2020 at 4:10 PM TestUser1 wrote:

So is this expected to work fine in my environment, Windows Server 2016 (OS
> Version 10.0.14393), without the workaround?
>

 I can't reproduce on Windows Server 8.1/Server 2012 R2 or later.

But you can certainly try the workaround.

Bill

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