[SOLVED]: SSH Host Key Verification Failed

If you've ever encountered the "Host Key Verification Failed" error while connecting to a remote server via SSH, you're not alone. This error can be quite frustrating, but fear not – in this article, we'll explore what it means and provide step-by-step solutions to resolve it. Whether you're a seasoned system administrator or a novice user, this guide will help you get past this common SSH hurdle.

Before diving into the solutions, let's understand what this error means. When you connect to a remote server using SSH, the server sends its public key to your SSH client to establish a secure connection. Your SSH client stores this key in a known_hosts file. The next time you connect to the same server, your client checks if the server's public key matches the one stored in the known_hosts file. If they don't match, you get the "Host Key Verification Failed" error, which is a security feature to prevent potential man-in-the-middle attacks.

Now, let's explore some common scenarios that can trigger this error and how to fix them. Pls follow through the article, as the root cause for this can be due to multiple reason, which requires respective solutions. Here i have identified and provided all the possible solution for this problem

Solved: SSH Host Key Verification Failed

Changing Server’s SSH Key

If the remote server has changed its SSH key for any reason, your client will detect a mismatch and throw the error.

Solution: Remove the old key from your known_hosts file and re-establish trust with the server. Use the ssh-keygen -R hostname command, where "hostname" is the server's IP address or domain name.

Known Hosts File Corruption

In some cases, your known_hosts file might become corrupted, leading to this error.

Solution:  Rename or delete the known_hosts file in your local ~/.ssh directory. SSH will create a new one the next time you connect to a server or Edit the know_hosts file and remove the entry for the server which you are trying to reach

 StrictHostKeyChecking Configuration

If your SSH client is set to strict host key checking, it will reject any key changes.

Solution: Temporarily disable strict host key checking using the -o StrictHostKeyChecking=no flag while connecting to the server. Remember to re-enable it once trust is re-established.

/dev/tty file issue

This may  caused by a udev problem .i.e, there will be  no /dev/tty device node or may be having wrong permission

Solution:

Execute the below command on the client machine.

#If file is missing execute below command
sudo mknod -m 666 /dev/tty c 5 0

#If file is present execute below command
chmod 666 /dev/tty

Conclusion

Encountering the "Host Key Verification Failed" error is a common part of SSH security protocols, designed to protect your connections from potential threats. By understanding the error and following the appropriate solutions outlined in this guide, you can confidently resolve this issue and continue to use SSH for secure remote access. Remember to always exercise caution when verifying host keys and ensuring the security of your SSH connections.

Reference

https://askubuntu.com/questions/45679/ssh-connection-problem-with-host-key-verification-failed-error