0

I am trying to access a university server using putty SSH however I don't have a key, all i have is a username and password. Whenever I try to connect I either get the no supported authentication error (server sent public key). Any advice?

5
  • 1
    sshd (daemon receiving ssh connection) might be configured to refuse key based authentification. 1) try to generate a key and copy it 2) ask university admin if you can use keys instead of password.
    – Archemar
    Oct 11, 2020 at 16:57
  • 2
    "server sent public key" actually means that the server accepts only key authentication. Oct 11, 2020 at 17:01
  • Also keep in mind that putty needs a specific format for the key. There are conversion methods for other formats.
    – dirkt
    Oct 11, 2020 at 17:01
  • thanks guys. I don't have an option for key verification and my supervisor said the server has been set up for password authentification however I haven't found where I can do that on putty. Is my best option using sshd instead of putty?
    – hamzah
    Oct 11, 2020 at 17:51
  • @hamzah your supervisor seems to be wrong. putty would have asked username/password if server had supported it.
    – eis
    Oct 20, 2020 at 19:06

2 Answers 2

2

Whenever I try to connect I either get the no supported authentication error (server sent public key).

The SSH server always sends a list of acceptable auth methods. In this case, it sent a list consisting only of one method – "public key" – so that's the only method PuTTY will try. (Which it cannot try because you don't have a keypair, so it'll just give up.)

my supervisor said the server has been set up for password authentification however I haven't found where I can do that on putty

There is no option for that. If the server allowed password authentication, PuTTY would have attempted to use it automatically.

If an auth method is disabled on the server, there's nothing a client can do to make it work – sure it can try requesting it, but the server will just refuse anyway, for the same reason why it didn't offer that mechanism in the first place. So you probably won't find any client which will bother including an option to try disabled mechanisms.

It's possible that you might have gotten the wrong server address; or that someone else changed its configuration and your supervisor was unaware of that.

Is my best option using sshd instead of putty?

No matter what client you use, it won't be able to use auth mechanisms that the server doesn't offer.

Note that 'sshd' is the OpenSSH server (daemon); the OpenSSH client is 'ssh'.

2
  • My supervisor just changed the authentication to allow for passwords however im still receiving the same message but now with "keyboard interactive" sent aswell as the key Any thoughts as to why?
    – hamzah
    Oct 12, 2020 at 10:58
  • So the supervisor enabled the keyboard interactive authentication, not password authentication. Though the keyboard interactive authentication is often used as an alternative way to implement the password authentication. See superuser.com/q/894608/213663 Oct 12, 2020 at 11:43
1

If the server was truly set to not accept password authentication, you need in this case ask your supervisor the missing authentication key (and how to use it).

If your supervisor is convinced that he has set up access via password to the server, this might be blocked by a wrong setting on the server where password authentication was not fully enabled.

You haven't mentioned your operating system and putty version, so I can't give a detailed answer.

The SSH server configuration file may in most cases be found in Linux inside the file /etc/ssh/sshd_config.

The two important settings here are:

  • PasswordAuthentication to yes
  • ChallengeResponseAuthentication to yes

If changing any of the above, the ssh system service needs restarting (reboot might be simpler).

0

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .