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jeklund
Asked: 2017-08-24 18:49:32 +0800 CST

ssh login using ssh keys only works once after on site login

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I have an interesting problem with ssh. Here is the setup.

My client (running Ubuntu 17.04) has public and private ssh keys. I copied over the public key to the server (running Ubuntu Server 16.04.3 LTS) using the ssh-copy-id command. I verified this worked by looking at the authorized_keys file on the server; my client's public key is the only one listed.

Now onto the problem. I am able to login to the server from the client through ssh, using my private ssh-key. But after I logout and attempt to ssh again, I get the following error:

Permission denied (publickey).

When I login to the server at the console, I use my password to login and it works fine. Then when I try to SSH again from my client, it works again. And I can logout and login as many times as I want. As soon as I logout from the console on the server (like I'm physically at the server logged in before this), I can SSH from my client exactly ONE more time. Then as soon as that session is ended, I get the Permission denied (publickey).error again on all subsequent SSH attempts. Any ideas?

Here is my ssh config file on my client:

Host sauron
        HostName 192.168.1.191
        User joe
        PubKeyAuthentication yes
        IdentityFile id_rsa

One more thing to mention is I do have the entire SSD on the server encrypted. I have to unlock it whenever I boot the server with an encryption password. Not sure if that's relevant. I suspect it could be a permissions issue, though I'm not sure of that either. Suggestions would be much appreciated, and please ask if you need clarification on anything.

server

1 Answers

  1. Thanks to @muru comment about encrypted home directories, I was led to this article about how to deal with this.

    The TLDR; of that article is as follows and fixed my problem:

    1. Create a directory in /etc/ssh/ with the same name as the login user you are using. In my case: /etc/ssh/joe.

    2. Copy the authorized_keys file to this directory.

    3. Set correct permissions of this file and directory to the user.

    4. Add the following line to the sshd_config file:

    AuthorizedKeysFile /etc/ssh/%u/authorized_keys

    1. Restart SSH.

    All fixed!

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