OGG… How can I set up ssh connection to GitHub repository?

ssh
Author

Ryo Nakagami

Published

2024-12-17

Problem

  • I want to set up an SSH connection for a GitHub repository with my macOS

Solution

Steps

  1. Generate a new ssh key
  2. Add the SSH Key to the SSH Agent
  3. Register the public key to GitHub
  4. test ssh connection
  5. update the ssh config file

Setup

1. Generate a new ssh key
ssh-keygen -t ed25519 -C "hoshinokirby@gmail.com" -f ~/.ssh/kirby_github_key

Option -t specifies the type of key to generate. ed25519 is faster and more secure than older algorithms like RSA and produces shorter keys while maintaining strong security.

Option -C adds a comment to the key for identification purposes.

-f specifies the filename and location for the generated key pair. This will generate two files

  • kirby_github_key: The private key (keep this secure! do not share!).
  • kirby_github_key.pub: The public key (you upload this to GitHub).
2. Add the SSH Key to the SSH Agent
eval "$(ssh-agent -s)"
ssh-add ./.ssh/kirby_github_key

The ssh-add command adds your private SSH key to the SSH authentication agent (ssh-agent) so it can be used for SSH connections without repeatedly asking for the key’s passphrase. If the key (kirby_github_key) isn’t added to ssh-agent, SSH won’t know to use it. You might encounter the error like this;

Permission denied (publickey).
3. Register the public key to GitHub
cat ~/.ssh/kirby_github_key.pub

After opening the file, copy the strings and register it at the Github at Settings > SSH and GPG keys > New SSH key

Then, test your connection by

4. test ssh connection
$ ssh -T git@github.com

if connection established successfully, the following message will pop up

Enter passphrase for key '/Users/hosinokkirby/.ssh/kirby_github_key': 
Hi Kirby! You've successfully authenticated, but GitHub does not provide shell access.

Update the ssh config file

Running ssh-add munally evewrytime will be troublesome. To avoid it, you can configure SSH to use the key automatically by editing your ~/.ssh/config file:

~/.ssh/config
Host github github.com
  HostName github.com
  User git
  Port 22
  IdentityFile ~/.ssh/kirby_github_key
  IdentitiesOnly yes
  TCPKeepAlive yes

Appendix: ❗ Trouble Connecting via SSH with a Private Key

summary
  • SSH is strict about private key security to protect against unauthorized access.
  • Always keep your private keys readable only by you.
  • Use chmod 600 your_key_file to ensure proper permission settings.

Trouble

When trying to connect using a SSH command, You might encounter an error like:

WARNING: UNPROTECTED PRIVATE KEY FILE!
It is required that your private key files are NOT accessible by others.
This private key will be ignored.

As a result, the SSH connection fails.

Root Cause

  • This error happens because the file permissions of the private key file are too loose.
  • For example, if the file permissions are set to 666 (readable and writable by everyone), SSH refuses to use the key for security reasons.

Solution

You can fix the issue by restricting the file’s permissions so that only the owner can read/write the file:

% chmod 600 <your-private-key-path>

After changing the permissions, try running the same SSH command again.