Our lab's compute cluster has a two-interface 'gateway' machine which we use to access the cluster nodes. Call this gateway1.publicdomain.com. Normally I access this machine from my laptop, laptop.anydomain.com like this:

ssh joe@gateway1.publicdomain.com

I have set up a public key in .ssh/id_rsa.pub on laptop, and copied that to .ssh/authorized_keys on gateway1. Ordinarily this works fine.

Today I am using a public access point rather than my usual work connection. When I do

ssh joe@gateway1.publicdomain.com

I get the response:

Permission denied (publickey,gssapi-with-mic).

Apparently it won't accept my id_rsa credentials (Problem 1) and I am not prompted for a password (Problem 2) even though ordinarily when I log in from a previously unknown host I am prompted for a password.

I am still able to ssh to gateway1 from another machine (call it otherhost.otherdomain.com) without problem, either with password or (after setting up the relevant id_rsa* files) with publickey authentication. I can also log into otherhost itself using publickey credentials from laptop, so I know there's nothing fundamentally broken about laptop's ssh setup.

Finally, even when I delete my public key form .ssh/authorized_keys on gateway1, I still get the same "Permission denied" message and no password prompt.

So I guess my question is, what can cause gateway1 to reject my publickey credentials from my laptop, and prevent password login, but not from another host? I have confirmed that the id_rsa.pub on laptop and authorized_keys on gateway1 are in sync.

EDIT: I haven't been able to duplicate the problem since I originally posted, because it only happened when I was connected to a particular wireless access point (not belonging to me or to my lab). I still don't know how this could occur.


Someone might be using the AllowUsers directive in the configuration of the server, or you might be using the wrong version of the SSH protocol.

Try adding -v (or two of them) to step up the verbosity; you might find something more helpful than simply denied.

Similarly, you can initiate ssh without a key exchange, rather than removing it on the server's authorized keys list. Read about it on the man page for ssh.

| improve this answer | |

Are you running debian? Might this be caused by blacklisted SSH keys?

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy