Since update cannot ssh Ubuntu server (permission denied) from Ubuntu client but Windows client can

Asked by sam on 2018-11-01

After an update (both on server and client side) I wasn't able to access my servers remotely as sysadmin. Both the servers and my laptop have Ubuntu installed. I was always able to connect remotely without a problem but since an update (it is an assumption the update screwed up something), either on the server side or on my laptop, I constantly receive a permission denied message, despite the fact that I didn't change anything to the configuration. I even generated new keys but no success. If it helps I can send you the output of "ssh -vvv server", my "config" file on the client side, my "ssh_config" and "shhd_config" files on the server side, as well as the "auth.log" output from the server.
Thanks for your help! Any advice would be greatly appreciated.

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Last query:
12 hours ago
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12 hours ago

If you remove the keys and use password authentication, is it OK?

sam (samenkov2018) said : #2

Hi Andrew,

Thanks for your suggestion! I haven't tried this yet.. will only be able to test that on Monday when I'm back at work as those servers are shared with a few colleagues of mine for scientific simulations. I'm the "manager" of the servers and the only one to use ubuntu. All the other users connect with PuTTY and WinSCP for file transfer. They can still access without a problem, while I'm the only one that's kicked out when I attempt to login.

This is the output of the auth.log on the one server (replaced server name with host01 and my ip with xxx.xxx.xxx.xxx)

Sep 27 15:19:36 host01 sshd[852]: error: Could not load host certificate "/etc/ssh/ssh_host_rsa_key-cert.pub": No such file or directory
Sep 27 15:19:36 host01 sshd[852]: userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedKeyTypes [preauth]
Sep 27 15:19:36 host01 sshd[852]: Connection closed by authenticating user sysadmin xxx.xxx.xxx.xxx port 58208 [preauth]

These messages make no sense because when sshd_config file reads:

PubkeyAcceptedKeyTypes <email address hidden>, ssh-rsa

I can try connecting to the server with a password but that won't be the most convenient solution (in case it works) as all the other users can connect just fine right now with their ssh keys.

Thanks again for your answer and suggestion!

Cheers,

Sami

sam (samenkov2018) said : #3

Hi Andrew,

I tested the password authentication and it works but this is more of a temporary solution and less safe than with ssh-keys.
Does the fact the it works with password authentication give you any hint to what the issue could be?

Thanks for your help!

Cheers,

Sami

Well you now know where the issue lies. I suggest you recreate the key pairs or check ownership and access on the existing key files. Check they are correct.

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