[cisco-voip] cygwin as sftp server

[Charles Goldsmith]

I was helping a customer out today to get their backups going on a new
install and from the TAC supported choices, they chose cygwin.  It's
been a few years since I've worked with it, but tested ssh/sftp to it
from putty, but when trying to add a backup device in CUCM DRS, we
were getting the standard failed message:

 - Unable to save Backup Device successfully. Update failed : Unable
to access SFTP server. Please ensure the username and password are
correct.

doing some debugs on the cygwin ssh, I saw that we were getting this :

 - ssh_dispatch_run_fatal: no matching key exchange method found

I'm no ssh expert, and even with the highest verbosity on the debugs,
I couldn't figure out which one of these was the culprit, but these
lines resolved it in the /etc/sshd_config

KexAlgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc

My guess is that the latest cygwin comes with a newer version of
openssh that by default, doesn't allow an older method to come from
CUCM.

The customer's environment is 10.5.2, and I was testing with 9.1.2 in
my lab.  Both environments was using cygwin 1.7.35 and OpenSSH 6.8p1

Let me know if you have any questions