SSH Unexpectedly Not Prompting for Password

[Lucas, Brandon]

I also wouldn't expect SSH to work that way but that is indeed the behavior as I have described.  The three "bear" accounts all have the exact same id_rsa.pub file and authorized_keys entries, which list the "teddy" account on the fourth server.  This relationship was set up so that I could push continuous code builds from the "teddy" server to any 3 of the "bear" servers.

The secure log on a server I am connecting to, is showing on successful connection as if there was a key pair set up for the "bear" user between the servers:

May 14 14:06:18 bearServer sshd[4199]: Accepted publickey for bear from xx.xx.xx.xx port 54305 ssh2
May 14 14:06:18 bearServer sshd[4199]: pam_unix(sshd:session): session opened for user bear by (uid=0)

.. but this key pair does not exist.  If I were to look at authorized keys on the server I connected to I see:

ssh-rsa HASH== teddy at teddyServer.domain.com

...with the id_rsa.pub saying the same thing.


The home directory is not NFS mounted, nor did we do an ssh-add.  When connecting I am simply using "ssh bearServer.domain.com" when logged in as the "bear" user on one of the 3 servers, and I get right in.

I found a forum posting where someone online was seeing the exact same behavior but for the life of me I cannot find the forum posting now.  In their case they suggested that AgentForwarding was the cause.


-----Original Message-----
From: redhat-list-bounces at redhat.com [mailto:redhat-list-bounces at redhat.com] On Behalf Of m.roth at 5-cent.us
Sent: Tuesday, May 14, 2013 12:36 PM
To: General Red Hat Linux discussion list
Subject: Re: SSH Unexpectedly Not Prompting for Password

Lucas, Brandon wrote:
>
> I have a question about SSH that I can't seem to figure out.  Here is the
> situation:
>
> 4 servers on RHEL 6.3

You really should update to 6.4, for security reasons if nothing else.
>
> One server has a local account ("teddy").  SSH key pairs have been set up
> between this "teddy" account and the other 3 servers on a different local
> account common to the other 3 servers ("bear"), but not present on the
> "teddy" server.  These 3 servers do not have a "teddy" account.
>
> Now, I am able to ssh without password between the 3 "bear" servers using
> the "bear" account without a password.  This behavior is undesired as it
> bypasses some key controls.
>
> I figure what must be happening here is that since the 3 "bear" servers
> have the same public key that points to the "teddy" server, they must be
> using that fourth server as some type of "witness" to verify the identity
> of the user making the ssh connection, bypassing the password for the
> "bear" account.  I have disabled AgentForwarding on all 4 servers in
> question, as well as X11Forwarding.  This has not helped.
>
> What is going on here and how do I avoid it?

As someone else said, ssh doesn't work that way. Question 1: where's your
home directory - it's not NFS mounted, is it? Second, did you do an
ssh-add on teddy, first? Third, are you doing ssh -A?

      mark

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