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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