ssh – How to Force SSH Client to Use Only Password Authentication

key-authenticationpasswordssh

If I use pubkey auth from e.g.: an Ubuntu 11.04 how can I set the ssh client to use only password auth to a server? (just needed because of testing passwords on a server, where I default log in with key)

I found a way:

mv ~/.ssh/id_rsa ~/.ssh/id_rsa.backup
mv ~/.ssh/id_rsa.pub ~/.ssh/id_rsa.pub.backup

and now I get prompted for password, but are there any offical ways?

Best Answer

I recently needed this too, and came up with this:

ssh -o PreferredAuthentications=password -o PubkeyAuthentication=no example.com

You need to make sure that the client isn't configured to disallow password authentication.

Related Solutions

SSH – SSH Passwordless Authentication Doesn’t Work

In CentOS 6, there is a bug that prevents ssh RSA authentication from working as desired if selinux is in Enforcing mode.

You can disable selinux, or you can try the workaround below:

restorecon -R -v ~$USER/.ssh

Ssh – Expired password and SSH key based login with UsePAM yes

The order of operations that causes the expired password prompt is as follows:

SSH runs the PAM account stage, which verifies that the account exists and is valid. The account stage notices that the password has expired, and lets SSH know.
SSH performs key-based authentication. It doesn't need PAM for this, so it doesn't run the auth stage. It then sets up the SSH login session and runs the PAM session stage.
Next, SSH remembers that PAM told it the password had expired, prints a warning message, and asks PAM to have the user change the password. SSH then disconnects.

All of this is SSH's doing, and I don't see any SSH options to configure this behavior. So unless you want to build a custom version of SSH and/or PAM, the only option I see is to prevent PAM from reporting the expired password to SSH. If you do this, it will disable expired password checks over SSH entirely, even if the user is logging in over SSH with a password. Other (non-SSH) methods of login will still check password expiration.

Your current pam.d/sshd file has a account include common-account entry. I presume there's a common-account file which contains a reference to pam_unix.so. This is the line that checks for an expired password.

You probably don't want to touch the common-account file itself, since it's used for other login methods. Instead, you want to remove the include from your pam.d/sshd file. If there are other functions in common-account besides pam_unix.so, you probably want to put them directly into pam.d/sshd.

Finally, remember that this is a modification to the security of your system and you shouldn't just blindly trust me to give you good advice. Read up on how PAM works if you're unfamiliar with it. Some starting places might be man 7 PAM, man 5 pam.conf, and man 8 pam_unix.

Best Answer

Related Solutions

SSH – SSH Passwordless Authentication Doesn’t Work

Ssh – Expired password and SSH key based login with UsePAM yes

Related Question