So in my example I'd use it like this: $ ssh-keygen -R Resolve Using ssh-keygenĪnother solution would be to use the ssh-keygen utility to delete the offending key from your known_hosts file, which can be done with the following command: $ ssh-keygen -R Once done, you'll have a new fingerprint in our known_hosts file for this server, and the warning will be gone. Delete the line specified in the warning messageīy deleting this line, your SSH client won't have an ECDSA key fingerprint to compare to, and thus will ask you again to verify the authenticity of the server the next time you connect.Open the known_hosts file specified in the warning message.In my example this line said "Offending ECDSA key in /Users/scott/.ssh/known_hosts:47", which refers to line 47. In the warning message find the line that tells you where the offending ECDSA key is located in the known_hosts file.The easiest ways I've found to fix this problem is the following two solutions. If you are 100% sure that this was expected behavior and that there is no potential security issue, you'll need to fix the issue before continuing. The IP address and hostname I was connecting to were the same, but the underlying server was different, which is what tripped the SSH client to issue this warning. In my case, I had an elastic IP address on AWS and assigned it to a different server after redeploying our application. Of course, this isn't always the case, and there are many reasons for the ECDSA key fingerprint to change for a server. This scenario is exactly what the "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" message is trying to warn you about. This is called a man-in-the-middle attack. If this new server is malicious then it would be able to view all data sent to and from your connection, which could be used by whoever set up the server. If you enter 'yes', then the fingerprint is saved to the known_hosts file, which SSH then consults every time you connect to that server.īut what happens if a server's ECDSA key has changed since you last connected to it? This is alarming because it could actually mean that you're connecting to a different server without knowing it. The authenticity of host ' (192.168.1.1)' can 't be established.ĮCDSA key fingerprint is SHA256:hotsxb/qVi1/ycUU2wXF6mfGH++Yk7WYZv0r+tIhg4I.Īre you sure you want to continue connecting (yes/no)? This is done after first connecting to the server, and will prompt you with a message like this: $ ssh When you connect to a server via SSH, it gets a fingerprint for the ECDSA key, which it then saves to your home directory under ~/.ssh/known_hosts. Offending ECDSA key in /Users/scott/.ssh/known_hosts:47ĮCDSA host key for has changed and you have requested strict checking. Please contact your system administrator.Īdd correct host key in /Users/scott/.ssh/known_hosts to get rid of this message. SHA256:hotsxb/qVi1/ycUU2wXF6mfGH++Yk7WYZv0r+tIhg4I. The fingerprint for the ECDSA key sent by the remote host is It is also possible that a host key has just been changed. Someone could be eavesdropping on you right now (man-in-the-middle attack)! Because of this, there are quite a few checks built-in to the popular SSH clients, like OpenSSH, that ensure your connection can't be compromised.Īn example of one of these checks is the following, which identifies when the fingerprint of a server has changed: $ ssh WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! #Change host key virtualbox mac freeIt aims at ensuring that your connection, and therefore all data passed, is free from eavesdropping. SSH, or Secure Shell, is a very common way to securely access remote machines, typically via the command line.
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