VyOS restricted-shell Escape and Privilege Escalation

This module exploits command injection vulnerabilities and an insecure
default sudo configuration on VyOS versions 1.0.0 arbitrary system commands as root.

VyOS features a `restricted-shell` system shell intended for use by
low privilege users with operator privileges. This module exploits
a vulnerability in the `telnet` command to break out of the restricted
shell, then uses sudo to exploit a command injection vulnerability in
`/opt/vyatta/bin/sudo-users/vyatta-show-lldp.pl` to execute commands
with root privileges.

This module has been tested successfully on VyOS 1.1.8 amd64 and
VyOS 1.0.0 i386.