Moving from Windows 1809's OpenSSH to OpenSSH Portable

by Frank Fu

I'm using Git for Windows and have configured the git client to use a custom ssh command via core.sshCommand to look for the ssh binary that has been installed as part of Windows 10's 1809's Optional Feature this has been working well but recently when I'm trying to use git against Github as a remote repo (Bitbucket worked fine) it has been giving me warning messages

warning: agent returned different signature type ssh-rsa (expected rsa-sha2-512)

After performing the obligatory google search, I stumbled across several threads but still couldn't find a solution. This annoyed me enough to look for other alternatives and discovered a Windows port of OpenSSH Portable. So since I didn't want (probably not even possible) to have both binaries (and ssh-agents) running side by side. I decided it would be best that I remove Window's 1809's installed version first then install OpenSSH Portable

Uninstall Windows' OpenSSH

This basically removes the binaries installed in C:\Windows\System32\OpenSSH


Remove-WindowsCapability -Online -Name "OpenSSH.Client~~~~0.0.1.0"
Remove-WindowsCapability -Online -Name "OpenSSH.Server~~~~0.0.1.0"

Stop and delete the existing Windows Service

Get-Service ssh-agent | Stop-Service
sc.exe delete ssh-agent

Install OpenSSH Portable

I'm using Chocolatey's openssh package but you can download and install the binaries yourself here. This installs the binaries into C:\Program Files\OpenSSH-Win64 . The /SSHAgentFeature flag ensures that the SSH Agent Service gets installed too.

choco install openssh --package-parameters="/SSHAgentFeature"

Note version 7.9.0.1 was the last good working version for me. 8.0.0.1 was complaining about my ssh key being in an invalid format.

Check that you have the binaries installed

Get-Command ssh*exe
    
    CommandType Name              Version Source
    ----------- ----              ------- ------
    Application ssh.exe           7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh.exe
    Application ssh-add.exe       7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh-add.exe
    Application ssh-agent.exe     7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh-agent.exe
    Application sshd.exe          7.9.0.0 C:\Program Files\OpenSSH-Win64\sshd.exe
    Application ssh-keygen.exe    7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh-keygen.exe
    Application ssh-keyscan.exe   7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh-keyscan.exe
    Application ssh-shellhost.exe 7.9.0.0 C:\Program Files\OpenSSH-Win64\ssh-shellhost.exe

Check that you have the ssh-agent running

Get-Service ssh-agent

Status   Name               DisplayName
------   ----               -----------
Running  ssh-agent          ssh-agent

Configure our git client to use our newly installed binaries for ssh

git config --global core.sshCommand "'C:\Program Files\OpenSSH-Win64\ssh.exe'"

Ensure that it has been configured properly

Get-Content $env:USERPROFILE\.gitconfig | Select-String sshCommand -Context 6

[core]
        excludesfile = ~/.gitignore_global
        sshCommand = 'C:\\Program Files\\OpenSSH-Win64\\ssh.exe'

I wanted to remove any existing identities (but this could be optional)

ssh-add -D

Add new identites

ssh-add

Then we should be good to go ;)