Passwordless SSH (Windows --> CentOS)

Question

I am trying to get passwordless SSH authentication to work from a Windows 7 machine to local server.

1. Windows machine: My login name in this machine is MY_LOGIN_NAME. I am using Cygwin as the command line.

2. CentOS 5.5 Server: I have admin privileges on this server; logged in as root.

Here is what I have done so far:

1. Logged into MY_LOGIN_NAME on the Windows machine, I ssh-config-usered from the Cygwin command line. This created (at least) RSA public and private keys in C:/Users/MY_LOGIN_NAME/.ssh

2. I copied the public key over to the server to the .ssh directory using scp.

   scp id-rsa.pub [email protected]:.ssh/id-rsa.pub

3. Then I tried to log into the server using ssh like so:

   ssh -i id_rsa [email protected]

But it still asks me for my password. What am I missing?

Answer 1

The problem is your step 2. You overwrote [email protected] public key with your Cygwin public key. That's not what you want.

You should, instead, add your public key to [email protected] authorized keys. This can be done manually appending your id-rsa.pub to /root/.ssh/autorized_keys (on CentOS), or automagically running ssh-copy-id on Cygwin.

ssh-copy-id [email protected]

It will prompt for your password and then you should be fine.

Also, you should recover [email protected] public key, or generate a new pair, if it's not inconvenient.

Answer 2

Also, be aware of the PermitRootLogin option available in the server-side /etc/ssh/sshd_config file, which is described,

PermitRootLogin
Specifies whether root can log in using ssh(1). The argument must be "yes",
"without-password", "forced-commands-only", or "no". The default is "yes".

If this option is set to "without-password", password authentication is
disabled for root.  

Setting it to "without-password" has the effect of only allowing root to log in through ssh by having an authorized public key in place, which keeps Mallory from attempting to brute-force root's password. However, failure to authenticate via authorized public key manifests as repeated password prompts, which can be confusing.