libssh Authentication Bypass Scanner

This module exploits an authentication bypass in libssh server code
where a USERAUTH_SUCCESS message is sent in place of the expected
USERAUTH_REQUEST message. libssh versions 0.6.0 through 0.7.5 and
0.8.0 through 0.8.3 are vulnerable.

Note that this module's success depends on whether the server code
can trigger the correct (shell/exec) callbacks despite only the state
machine's authenticated state being set.

Therefore, you may or may not get a shell if the server requires
additional code paths to be followed.