How can I accept all SSH requests?

Question

I would like to have a VM accept all SSH requests. That is, anyone on the network (namely, the host) can SSH into the shell without password checking, public key, etc. I know this is largely against the premise of SSH, but is it possible?

Criterion: It should not be a VM hack; I want this to simulate two computers on the same network, one with 'swiss-cheese' security.

In summary: ssh user_name@host_machine should work, regardless of the nature of the ssh'ing machine, settings, RSA keys, etc.

Answer 1

Two options:

• Recompile SSH to always accept no matter what the password (probably no more than a line or two needs to change)
• Modify your PAM stack to always accept for authentication. You can make this for all services, or you can specify an alternate PAM stack just for inbound SSH.

Note that I'm a bit rusty on PAM rules, and these are (obviously) not tested. So you may have to tweak things a bit to make it work. Feel free to edit if you get it working.

But for example to allow if the attempted username is listed in a file:

# in /etc/pam.d/sshd
auth sufficient pam_listfile.so item=user sense=allow file=/etc/sshd_allowed_users onerr=fail

Or just permit everything:

# in /etc/pam.d/sshd
auth sufficient pam_permit.so

Presumably a user would have to pick the username of a valid account. But I'm not 100% certain as to what will happen.