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Please tell me, is there a ssh server with this unusual capability? Or I would have to edit the source code of openssh-server and recompile?

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Something smells fishy. Is this what you really want to do or is it towards some other end. For example, do you really want anyone to connect, or is it the "without authentication" part that you want? Why? See: XY problem – user235731 Jul 19 '13 at 10:37
Why not just use public key authentication? Just add everyone's keys to the authorized keys list (ridiculously easy with ssh-copy-id). They'll have password-less login from then on (as long as their ssh key has been added to their user agent, which should be automatic in Ubuntu). – user235731 Jul 19 '13 at 10:44
And have you tried setting all *Authentication options to "no" in /etc/ssh/sshd_config? – user235731 Jul 19 '13 at 10:49
I only know of one alternative to openssh and that's lsh, but I doubt that will do it either. You're taking the "secure" out of "secure shell", so I doubt any would support it. I think the correct solution, and the thing you should have been pursuing all along, is getting public key authentication to work, since that is a supported feature of an SSH server. – user235731 Jul 19 '13 at 12:12
You are mistaken. It includes lshd, an SSH server. You can try to combine its --no-password and --no-publickey options. It also has an experimental option --login-auth-mode to disable authentication altogether. See my updated answer below. – user235731 Jul 19 '13 at 13:03
up vote 1 down vote accepted

Have all the users run this from their local machines:

([ -f ~/.ssh/ ] || ssh-keygen -t rsa ) && (ssh "([ -d ~/.ssh ]||mkdir -m 700 ~/.ssh) && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys" < ~/.ssh/

Replacing "user@example" with their username and the board's hostname or IP address.

Since you're having troubles with public key authentication, you can try lsh. lshd, the lsh SSH server, has an experimental option --login-auth-mode to bypass user authentication. See the manual for more information.

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Unfortunately, I have a major problem with authorized keys: they simply do not work for this board, no matter what I do. The solution is still unknown, so I would like to disable ssh security at all for a while – Jake Badlands Jul 19 '13 at 10:47
Sorry, I posted this answer before your comment arrived in the question above. – user235731 Jul 19 '13 at 10:49
Edited to include info on lsh, though I still think that the original problem that you should have been pursuing is the inability to use public key authentication; hence, this was an XY problem afterall. – user235731 Jul 19 '13 at 13:10

Assuming you're using some sort of unix that relies on PAM, removing all the auth entries for the PAM configuration that ssh uses should do this. Remember to set UsePAM to "yes" in your sshd_config.

But this is a really bad idea; no matter what your justifications are.

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authentication without password is a choice ( rather poor one ) that you make and would be achieved by tweaking the config file of your server (ssh openssh or ....) I will recommend you to use MOSH; which is a new generation openSSH. you can read all about it at mosh-disc

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From the comments under the question it seems that it is not possible to disable authentication on the OpenSSH daemon by tweaking the configuration. Are you sure that MOSH allows this? If yes could you please add more details? ------ It seems that the major benefits of MOSH are a new protocol running on UDP and a predictive local echo. ------- I have not noticed any changes in user authentication in MOSH. In fact it seems that MOSH uses standard SSH for user authentication. Please see . – pabouk Dec 10 '13 at 9:00
pabouk; I don't now what you exaclty mean when you say "disable authentication". if you mean what i think you mean just set PasswordAuthentication no in your sshd_config file and you are golden. – r004 Dec 11 '13 at 13:32
"disable authentication" - Is not it what is the question about - to configure sshd to not require authentication? --- It is always good to check the comments and other answers before answering. Here is the relevant comment for the PasswordAuthentication option:… If PasswordAuthentication no works for you then please let us know. – pabouk Dec 11 '13 at 14:20

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