How to Get Known Host Key from SFTP Server

Hello Dev, have you ever encountered a warning message when connecting to an SFTP server stating that the server’s host key is unknown? This message can be quite alarming if you are not familiar with the process of acquiring the server’s known host key. In this article, we will guide you through the steps on how to get the known host key from an SFTP server in a relaxed and easy-to-understand language.

What is a Host Key?

Before we delve into the process of getting a known host key, it is essential to understand what a host key is. A host key is a unique identifier that is used to authenticate a server’s identity when a client connects to it through SSH (Secure Shell) or SFTP (Secure File Transfer Protocol). It is usually a cryptographic key that is generated by the server and saved in a file called the host key file.

When a client connects to a server for the first time, it checks the server’s host key against the one saved in its known host key file. If the keys match, the client proceeds with the connection. However, if the keys do not match, the client will issue a warning message, indicating that the server’s identity is not verified, and the user could be at risk of connecting to an impersonated server.

Methods of Obtaining Known Host Key

There are several ways to get the known host key from an SFTP server. Some of the ways are:

Method 1: Contact the Server Administrator

The easiest way to obtain a known host key is to contact the server administrator and request that they provide you with it. The server administrator should be able to provide you with the server’s host key file or the specific key that you need to add to your known host key file.

If you are unsure about who the server administrator is, you can contact your hosting service provider, who should be able to assist you with this process.

Method 2: Obtain the Host Key from the Server Console

If you have direct access to the server console, you can obtain the server’s host key directly from the console. The host key file is usually located in the /etc/ssh/ directory and can be accessed using a text editor such as Vim or Nano.

Once you have opened the host key file, look for the line that begins with “ssh-rsa” or “ssh-dss.” This line contains the server’s public key, which you can copy and add to your known host key file.

Method 3: Obtain the Host Key from a Running SSH Client

If you have previously connected to the server using an SSH client, you can obtain the server’s host key from the client’s known host key file. The known host key file is usually located in the ~/.ssh/ directory and can be accessed using a text editor.

Once you have opened the known host key file, look for the line that corresponds to the server’s hostname or IP address. This line contains the server’s public key, which you can copy and add to your known host key file.

How to Add a Known Host Key to Your System

Now that you have obtained the server’s host key, you need to add it to your known host key file to verify the server’s identity when connecting to it. To add the known host key to your system, follow these steps:

Step 1: Open Your Terminal

Open your terminal application on your local machine. You can access your terminal by searching for “Terminal” in your Operating System’s search bar or by using the shortcut keys (Ctrl + Alt + T).

Step 2: Create Your Known Host Key File

If you do not already have a known host key file, you will need to create one. The known host key file is usually located in the ~/.ssh/ directory and can be created using the following command:

Once you have created the known host key file, you can proceed to the next step.

Step 3: Add the Host Key to Your Known Host Key File

To add the host key to your known host key file, use the following command:

You should replace [server IP or hostname] with the actual IP address or hostname of the server. If the server uses a non-standard port, you can specify the port number using the -p flag followed by the port number.

Once you have entered the command, press Enter. You will be prompted to confirm that you want to add the host key to your known host key file. Type “yes” and press Enter to add the key.

Frequently Asked Questions

1. What is a known host key?

A known host key is a unique identifier that is used to authenticate a server’s identity when a client connects to it through SSH or SFTP.

2. Why do I need to add a known host key?

You need to add a known host key to verify the server’s identity when connecting to it. This ensures that you are not connecting to an impersonated server and that your data is secure.

3. How do I obtain a known host key?

You can obtain a known host key by contacting the server administrator, obtaining the host key from the server console, or obtaining the host key from a running SSH client.

4. How do I add a known host key to my system?

To add a known host key to your system, you need to create a known host key file and add the host key to the file. This can be done using the ssh-keygen and ssh-keyscan commands.

5. What is the location of the known host key file?

The known host key file is usually located in the ~/.ssh/ directory.

Conclusion

Obtaining a known host key from an SFTP server is an essential step in ensuring the security of your data when connecting to the server. By following the steps outlined in this article, you can obtain the server’s known host key and add it to your known host key file, ensuring that your connection to the server is safe and secure.