What is an SSH Key and How to Add One in Oracle

An SSH key is a pair of cryptographic keys used for secure communication between a client and a server over the SSH (Secure Shell) protocol. It is commonly used to log into servers and execute commands remotely without needing to manually enter a password each time.

There are two main types of SSH keys:

Public Key: This key can be shared openly with any system or server you want to connect to. It is used to verify the identity of the person trying to authenticate.
Private Key: This key is kept private and secure on the client machine. It should never be shared. The private key is used to decrypt the data that the server encrypts using the public key during the authentication process.

How SSH Keys Work:

When you attempt to connect to a server using SSH, the following steps occur:

Server Checks for Public Key: The server checks whether your public key is listed in its authorized_keys file (usually located in the .ssh folder in the user’s home directory).
Challenge and Response: If the public key matches, the server challenges the client to prove it has the private key by encrypting a random message with the server’s public key.
Authentication: The client decrypts this challenge with its private key and sends the response back to the server. If the response is correct, the server grants access, allowing the client to log in without a password.

Advantages of Using SSH Keys:

Security: SSH keys are much more secure than using traditional passwords. The private key is never transmitted over the network, reducing the risk of interception.
Convenience: Once set up, SSH key authentication allows for password-less login, making it easier to manage multiple servers or remote systems.
Protection Against Brute Force Attacks: Passwords are vulnerable to brute-force attacks, whereas SSH keys are practically impossible to guess due to the complexity of the key’s cryptographic nature.

Use Cases:

Remote Server Access: SSH keys are often used to log into remote servers securely.
Automated Scripts: They are also used in automation and DevOps environments to run scripts that interact with remote servers without requiring user interaction.
Version Control Systems: SSH keys are used in services like GitHub, GitLab, and Bitbucket to securely push and pull code from repositories.

By using SSH keys, you ensure secure and efficient remote access to systems without compromising security.

Steps to Add SSH key

If you’re working with Oracle servers, managing your SSH keys efficiently can save you a lot of time and make your system more secure. In this guide, we’ll walk you through the steps to add an SSH key to your Oracle server, as well as the best practices to backup the configuration before making any changes.

Step 1: Prepare Your SSH Key

Before you can add your SSH key to your Oracle server, you need to have an SSH key pair ready. If you don’t already have one, you can generate it using the following command on your local machine:

ssh-keygen -t rsa -b 2048

This will generate a private key (id_rsa) and a public key (id_rsa.pub). Keep the private key safe and secure on your local machine. You’ll use the public key to authenticate with your Oracle server.

Step 2: Backup Your Existing Authorized Keys File

It’s always a good idea to back up important configuration files before making any changes. This helps prevent any potential errors or data loss. To back up the authorized_keys file, follow these steps:

Open a terminal session and navigate to your .ssh directory:

cd ~/.ssh

Create a backup of the existing authorized_keys file:

cp authorized_keys authorized_keys.bak

This command will create a backup file named authorized_keys.bak in the same directory.

Step 3: Edit the authorized_keys File

Now that you’ve backed up your configuration, you can proceed to add your SSH public key to the authorized_keys file. Follow these steps:

Open the authorized_keys file in your preferred text editor. If you’re using vim, you can open the file like this:

vim authorized_keys

Once the file is open, press Shift + G to move the cursor to the bottom of the file.
Press Shift + A to go to the end of the current line and start adding your SSH key.
Paste your SSH public key (from id_rsa.pub) into the file. Here’s an example of what a key might look like:

ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAhTzjndgaYs0BfQqD0F9NumodYOUfd38wQIO7QdVsYjeKatubmo61CN023sDzktST8EsclxTBweJPrnk4mvWw9/DQViFiGU+OZV5fYhzdHbkyJlRJZkFkZ0iDgUeS1T7Bnkc/3cEVBikvdvz7PZDnNSTDTvYIcPg0ehVdfzyPbVt/aF0cjH/bUAgxStkWYMl3TNAw1IlL1xxjoh2csiRvWhg3SClVMWTuhyGO50l3bft92URwj1aIs7shUN17iJTLQJb9tWI3eOA4xWhcXn4yFEfxNrr0BDnRrFHmJU4kHYnyX7AXn/XH4fFNv4HOSQrY3JSaSvcd7ZmJVeOwbBkKBs==  A122324

Once you’ve pasted the key, press Shift + G again to move the cursor to the end of the file, and then press Shift + $ to go to the end of the line.
Save and exit the editor by typing :wq (write and quit).

Step 4: Adjust Terminal Settings (If Needed)

If your terminal is too wide, you might encounter an error when trying to view or edit the file. If this happens, you can run the following command to adjust the terminal width:

This will reset the terminal to a more manageable width, preventing overflow issues when working with large files.

Step 5: Test Your SSH Key

Now that your SSH key is added to the authorized_keys file, you should test that it works by attempting to connect to your Oracle server via SSH:

ssh username@oracle_server_ip

If everything is configured correctly, you should be able to log in without needing to enter a password, as the SSH key authentication will handle the login process.

Step 6: Restore from Backup (If Necessary)

In case you encounter any issues or want to undo the changes, you can restore the authorized_keys file from your backup:

Navigate to your .ssh directory:

cd ~/.ssh

Restore the backup file:

cp authorized_keys.bak authorized_keys

Verify the contents of the file to ensure everything is back to the previous state.

By following these steps, you can securely add an SSH key to your Oracle server and ensure that your server remains protected and accessible only to authorized users. Backing up your configuration files before making any edits is a crucial step that can save you from potential errors and downtime.