Test SSH connection to GitHub

This repository is used to test the SSH connection to GitHub without using the ssh-agent as recommended in GitHub Docs. Some of the reasons are exposed here and they're serious enough to be worth finding a way to overcome these possible security holes.

For connecting GitHub I was using a dedicated generated ssh key named rubincced25519 which used ed25519 digital signature scheme and the key was correctly registered in GitHub.

In many cases I have solved the complex connectivity problems through ssh using the ssh client configuration file: ~/.ssh/config.

A single host section in this file looks like this:

Host firezila
    HostName firezila.example.com
    User chefman
    ServerAliveInterval 60
    ServerAliveCountMax 10
    IdentityFile ~/.ssh/chefmaned25519

So I added a new Host section in my ~/.ssh/config file:

Host github.com
     HostName github.com
     User git
     ServerAliveInterval 60
     ServerAliveCountMax 10
     IdentityFile ~/.ssh/rubincced25519

After running the connectivity test comand

$ ssh -T git@github.com
git@github.com: Permission denied (publickey).

I ended up with the same error message that indicates the connection is still not working as expected even if I pointed directly to the correct key file.

After retesting with more verbose output it seemed that the ssh client still tried to connect using standard rsa key.

Finally the working host section looks like this:

Host github.com
#     HostName github.com
#     User git
#     ServerAliveInterval 60
#     ServerAliveCountMax 10
    IdentityFile ~/.ssh/rubincced25519
    IdentitiesOnly yes

I intentionally left the commented lines to illustrate that they were of no importance in this case.

Hope that helps. Cheers!