KexAlgorithms [email protected] on Windows

[hdatma]

"OpenSSH for Windows" version
0.0.17.0

Server OperatingSystem
Windows 10 Pro
Windows Server 2012 Foundation

Client OperatingSystem
MacOS 10.12.5 with custom OpenSSH 7.5p1

What is failing

Two SSH servers, with exactly the same OpenSSH software version and sshd_conf.

On Windows Server: no matching key exchange method found
On Windows 10: all is well.

This is the log on Windows Server:

"3540 15:41:03:562 Connection from port 55883 on 192.168.1.15 port 22
3540 15:41:04:000 Unable to negotiate with port 55883: no matching key exchange method found. Their offer: diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1"

[bagajjal]

Kex negotiation will be initiated by both client and server.. In client it picks either from ssh_config or through command line arguments.. In sshd it picks from sshd_config or command line arguments if you start as non-service process or default kex algorithms.. Could you please check this configuration in both the systems and compare both the ssh logs (ssh.exe -vvv user@ip) and sshd log with debug3 enabled.. If you still have questions then please share both ssh and sshd logs and configuration..

[manojampalam]

Reopen once you have the logs ready.

[hdatma]

1. I see errors from sshd at start-up.

2. I usually write own keys using "ssh-keygen -t ed25519 -o -a 100".
   The command works on Windows 10 Pro, but fails on Windows Server 2012 Foundation.

`---> starting sshd...

6472 20:21:52:909 debug1: sshd version OpenSSH_7.5, LibreSSL 2.5.3
6472 20:21:52:909 debug3: socket:0, socktype:1, io:000000F3159D0860, fd:3
6472 20:21:52:909 debug3: close - io:000000F3159D0860, type:2, fd:3, table_index:3
6472 20:21:52:909 debug3: open - handle:00000000000000F4, io:000000F3159D0BE0, fd:3
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: close - io:000000F3159D0BE0, type:2, fd:3, table_index:3
6472 20:21:52:909 debug1: private host key #0: ssh-rsa SHA256:bCCuyJvd6le8bfIoZh9xudAWQ7ga36nmJLjtY6zXUqk
6472 20:21:52:909 debug3: open - handle:00000000000000F4, io:000000F3159D0BE0, fd:3
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: close - io:000000F3159D0BE0, type:2, fd:3, table_index:3
6472 20:21:52:909 debug1: private host key #1: ssh-dss SHA256:NYTII3zVccEcEGaG0JEtGbqko/z57PzHB1MuEbXdK4U
6472 20:21:52:909 debug3: open - handle:00000000000000F4, io:000000F3159D0BE0, fd:3
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: close - io:000000F3159D0BE0, type:2, fd:3, table_index:3
6472 20:21:52:909 debug1: private host key #2: ecdsa-sha2-nistp256 SHA256:Ak0Do+Pu82XFj0kHf+9IcX3wLIbGeeybSYwx7xAEtFI
6472 20:21:52:909 debug3: open - handle:00000000000000F4, io:000000F3159D0BE0, fd:3
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: ReadFileEx() ERROR:38, io:000000F3159D0BE0
6472 20:21:52:909 debug3: read - no more data, io:000000F3159D0BE0
6472 20:21:52:909 debug3: close - io:000000F3159D0BE0, type:2, fd:3, table_index:3
6472 20:21:52:909 debug1: private host key #3: ssh-ed25519 SHA256:BhQkyRplazLCfbGeh0EoKOhSYLL+AcL6GNm53lfkgDA
6472 20:21:52:909 debug3: socket:228, socktype:1, io:000000F3159D0BE0, fd:3
6472 20:21:52:909 debug2: fd 3 setting O_NONBLOCK
6472 20:21:52:909 debug3: sock_set_v6only: set socket 3 IPV6_V6ONLY
6472 20:21:52:909 debug1: Bind to port 22 on ::.
6472 20:21:52:909 Server listening on :: port 22.
6472 20:21:52:909 debug3: socket:300, socktype:1, io:000000F3159D0E20, fd:4
6472 20:21:52:909 debug2: fd 4 setting O_NONBLOCK
6472 20:21:52:909 debug1: Bind to port 22 on 0.0.0.0.
6472 20:21:52:909 Server listening on 0.0.0.0 port 22.