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To:	"'cygwin AT cygwin DOT com'" <cygwin AT cygwin DOT com>
Subject:	Issue with seteuid and openssh
Thread-Topic:	Issue with seteuid and openssh
Thread-Index:	Adhvtv02KbP6OJaqT2yFog+Hy47J/g==
Date:	Tue, 24 May 2022 22:15:05 +0000
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From:	Dale Lobb via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Dale Lobb <Dale DOT Lobb AT bryanhealth DOT org>
Sender:	"Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

Greetings All,

  Has anyone seen an issue similar to this?

  I have a VMWare virtual machine loaded with Windows Server 2016 OS and a Cygwin installation.  Cygwin runs an installed SSHD service via cygrunsrv.exe.  A data gateway engine on a different machine makes regular programmatic connections via SFTP to the server throughout the day.  This setup was established in 2021 and has run without issue for almost a year.

  Last night, the server rebooted automatically after windows updates.  After the reboot, the data gateway was then no longer able to connect to the server.  This condition persisted until I was informed of the issue this morning and connected to the Windows server using RDP to take a look at the issue, at which point the SSH connection suddenly started working.  Further tests showed this to be entirely repeatable.  After rebooting the server, the SSHD daemon does not allow connections, neither with password nor public key authorization, until someone connects to the server via RDP, at which time the SSH connections suddenly starts working again.

  The server's Windows application event log shows numerous errors from the SSHD daemon stating "sshd: PID <####>: fatal: seteuid 197108: No such device or address" during the time frame when SSH connection were not working.  The errors stop immediately when the RDP connection is recorded in the same event log.

  A google search for the error message turned up something somewhat similar from this mailing list back in March of 2019, bit there is no mention of RDP in that exchange.  Also, the advice given, to convert the SSHD service from running under the cyg_server account to LocalSystem, does not apply here, because the Cygwin installation is recent enough that it is already running under LocalSystem.

  When this issue started, the server was running openssh-8.7p1-1.  The server was subsequently updated to the latest, openssh-9.0p1-1, but there has been no change in the observed behavior.

Best Regards,

Dale Lobb



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