
import Meta from '../../components/Meta';	

<Meta title='Authenticating to Github' />

# Updating a Cert from CLI

In case you are getting a cert not valid error or the like, make sure you have these tools.

What you'll need
- openssl
- keytool

## What is a Cert anyways?

A 'cert' is a X.509 digital certificate. These are maintained by publicly-trusted Certificate Authority (CA). 

### 1 Download the Cert

Pull down your cert from the url using the following command

```sh
openssl s_client -showcerts -connect NETWORK_PATH_REFERENCE:PORT > CERT_FILE_NAME.pem
```

network-path reference is the subdomain.domain.top level domain
It is basically a url without the path or scheme.

### 2 Convert your Cert (Optional)
Since java keytool can only take in binary formats, we need to convert the plain text format of the PEM to a DER.
Der is just a binary representation of the cert.

```sh
openssl x509 -outform der -in CERT_FILE_NAME.pem -out CERT_FILE_NAME.der
```

### 3 Import your Cert

You need to make sure your alias does not already existing in the key store. 
If there is already a key imported with the alias you are using, you will get an error and you can either change the alias on the existing key or delete it and replace it with your new key.

```sh
keytool -import -alias name_of_your_cert \ 
-keystore ./keystore_file.jks -file CERT_FILE_NAME.der
```

Or if you don't want to convert it 

```sh
keytool -import -alias name_of_your_cert \ 
-keystore ./keystore_file.jks -file CERT_FILE_NAME.pem
```

Over the last year, many certs have become defunct. If just want to update a JKS with a PEM pulled right from your URL, I'll show you how!

Updating a Cert from CLI


import Meta from '../../components/Meta';

<Meta title='Authenticating to Github' />

# Github and SSH

Github is incredibly popular 'Git repository hosting service'<sup>[1](https://www.simplilearn.com/tutorials/git-tutorial/what-is-github#what_is_github)</sup>, where **over 83 million developers** ([by their own admission](https://github.com/)) choose to store their code.
This level of popularity easily lands Github in the industry standard category of software development tooling.


If you've used github for more than a few years, you probably remember when November 13, 2020 rolled around and Github discontinued password authentication.
This took me a few weeks to understand how the heck I'm supposed to push my code
But that's what we are here to overcome. 


Now of course, you could take the [OAth approach](https://docs.github.com/en/rest/overview/other-authentication-methods#authenticating-for-saml-sso) but then you have to store that token, keep updating when it expires, etc. But I'm here to *show you a still more excellent way*, **SSH Keys**

## SSH Keys

Github provides an [excellent walk through](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent#generating-a-new-ssh-key) on how to setup github and your local git cli with a ssh key. Which, I've read multiple times, and followed step by step to great success. What it *does not show* is how to handle multiple ssh keys for authenticating with more than one repo.

This is actually much easier than it might sound. But a little background is necessary first. When you configure your git cli with a SSH Key, you are actually giving a ssh-agent a specific private key. Git then leverages the ssh-agent to authenticate you. What we need to do, is tell git to use a specific key when you are using git from a specific directory.

We will need to edit the ~/.gitconfig, open this file with your favorite text editor (mine is vi). Here is where the magic happens. Similarly to how you originally configured your ssh-agent, we are going to setup git to run a sshCommand depending on your current directory. Lets start with the 

Before we begin, you need to have both **private** ssh keys saved somewhere. Then you need to create a new config file, something like **.gitconfig-company1** and add this to it.

#### ~/.gitconfig-company1
```yaml
...
[core]
sshCommand = ssh -i ~/.ssh/path_to_your_key
...
```

You can create however many of these you want! Go wild. Next we need to setup git to use these specific config files depending on a path. Luckily, git makes that easy.


#### ~/.gitconfig
```yaml
...
[includeIf "gitdir:/directory1/"]
  path = .gitconfig-company1
[includeIf "gitdir:/directory2/"]
  path = .gitconfig-company2
...
```

Note, the `includeIf` just needs the root path, it will apply this configuration to anything nested in the directory provided. 

Having multiple authentications to github can be a pain, but git can make it a little less painful with this quick and easy tip...