March 10, 2023

Setting up SSH keys for personal and company work on Github

In my current company I cannot use my private Github account for working on the comapny’s private repositories. I need to have a dedicated account for this case. This is an understandable approach. A company would like to keep a strict access to its organization’s resources and avoid any issues with copyrights.

I would like to use different keys for different repositories and avoid using Personal Access Tokens completely.

First a personal key needs to be created. From the command line the ssh-keygen needs to be used:

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

or in a system that supports an newer algorithm like Ed25519:

$ ssh-keygen -t ed25519 -C "your_email@example.com"

After running the command it will prompt for two things:

to enter the path (and filename) for the newly created key
to enter a passphrase that will be used for the key

I want to distinguish both keys by naming them:

personalkey
companykey

An example output when creating a key:

Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa): /home/username/.ssh/personalkey
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/username/.ssh/personalkey
Your public key has been saved in /home/username/.ssh/personalkey.pub
The key fingerprint is:
SHA256:finger print will be here user.name@mail.com

Key creation has to be done for both keys, in each case different emails can be used. For personal key a personal email, for company’s key a company’s email.

Next step is to check if the ssh-agent is running:

$ eval $(ssh-agent -s)

The -s option is generating commands. The generated commands look like:

SSH_AUTH_SOCK=/tmp/ssh-163sf3GT082P/agent.3234581; export SSH_AUTH_SOCK;
SSH_AGENT_PID=3234591; export SSH_AGENT_PID;
echo Agent pid 3234591;

So after using Bash eval, SSH_AUTH_SOCK and SSH_AGENT_PID will be added to the environment variables.

$ eval $(ssh-agent -s)
Agent pid 3234591
$ env | grep SSH
SSH_AUTH_SOCK=/tmp/ssh-163sf3GT082P/agent.3234581
SSH_AGENT_PID=3234591

The generated keys should all be located in the specified directory, in most cases it will be ~/.ssh/

ls -la ~/.ssh/
total 28
drwx------  2 user user 4096 Mar  5 08:51 .
drwxr-xr-x 55 user user 4096 Mar  9 11:01 ..
-rw-------  1 user user 3454 Dec  9  2021 companykey
-rw-r--r--  1 user user  752 Dec  9  2021 companykey.pub
-rw-r--r--  1 user user 2442 Jan 23 15:11 known_hosts
-rw-------  1 user user 3434 Mar  5 08:47 personalkey
-rw-r--r--  1 user user  751 Mar  5 08:47 personalkey.pub

Next step is to add the generated keys to the ssh-agent:

$ ssh-add ~/.ssh/personalkey
Enter passphrase for /home/username/.ssh/personalkey: 
Identity added: /home/username/.ssh/personalkey (user.name@mail.com)
$ ssh-add ~/.ssh/companykey
Enter passphrase for /home/username/.ssh/companykey: 
Identity added: /home/username/.ssh/companykey (user.name@companymail.com)

Each key should be added to corresponding Github accounts. Adding a key is simple.

Log into the account
Go to Settings
Go to SSH and GPG keys
Choose New SSH key
Add a title (can be anything)
Choose key type to be Authentication Key
Put the public key in the Key section
Click Add SSH key button

Depending on the organization and the company configuring SSO (Single SignOn) might be needed for the added key.

The last step would be to clone a repository and assign a key to it.

$ git clone git@github.com:ajoz/ajoz.github.io.git

and after it is cloned:

$ git config --local core.sshCommand "ssh -i ~/.ssh/personalkey -F /dev/null"

Ofcourse personalkey should be used for a personal repository, companykey should be used for company’s repository.

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Setting up SSH keys for personal and company work on Github

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