This is a second part of OpenSSH Server configuration for Windows. In this part I am generating private and public keys, which will be used to login into Windows OpenSSH server. When using key based authentication on OpenSSH, you don't need to provide a password to connect Windows Server over OpenSSH (This is for Linux SSH server as well).
To start configuring password less OpenSSH server on Windows system, locate and open file C:\ProgramData\ssh\sshd_config. After opening sshd_config file, search below settings and configure them as shown.
Remove comment # in the line. PubkeyAuthentication yes Disable Password Authentication and set to no PasswordAuthentication no
Part 1: OpenSSH Server configuration for Windows
Part 2: Key based passwordless authentication to Microsoft Windows OpenSSH Server
Part 3: Configuring Ansible to Manage Windows Servers via OpenSSH
After making changes to file sshd_config, Restart OpenSSH SSH server (sshd) service.
Now login to Linux system and run command ssh-keygen which will generate public/private key pair. For further setup I pressing enter without giving any input, which will all use defaults. Key pair files will be created in default location inside .ssh folder in the user profile. I am not providing any passphrase to keys. As shown in the below screenshot.
Just to be noted here on your system generated key pair file names might be different. Next see the content of .pub extension file, I am using putty so I can copy the public key content, which will be used in next step.
Next go to windows OpenSSH server, create a new file administrators_authorized_keys under folder C:\ProgramData\ssh on Windows Server. (When creating new file make sure you enable file name extensions to unhide extension of file, if extension exists remove it from file)
Open file administrators_authorized_keys and copy public key, earlier copied from Linux system and paste in the administrators_authorized_keys file.
Next is crucial step of changing the file security permissions of administrators_authorized_keys. By running below commands you can provide correct permission in one go. At the moment of testing only one user can have access to file and login through ssh.
icacls C:\ProgramData\ssh\administrators_authorized_keys /inheritance:r icacls C:\ProgramData\ssh\administrators_authorized_keys /grant SYSTEM:F icacls C:\ProgramData\ssh\administrators_authorized_keys /grant "$(($env:USERNAME).tolower()):F"
After assigning security permissions, you can check what kind permission is assigned under Advanced Security Settings to administratos_authorized_keys. First it Disable inheritance and Provide full control access to System and Administrator (logged in user) and make Owner to Administrator user (logged in user).
Windows OpenSSH server is setup and configured for password less login. You can test it as shown in the below screenshot with ssh command on Linux
(I am using the user who has sole security permission on administrators_authorized_keys file, in my case it is administrator). While login it doesn't prompt or ask for any password. Authentication is happening using public/private keys pair.
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