Refactor (reduce) linux/x64/shell_bind_tcp_random_port

[geyslan]

This pull request modifies modules/payloads/singles/linux/x64/shell_bind_tcp_random_port.rb reducing its size in 4 bytes and refactoring it to easily embed nasm assembly.

Verification

• Start msfconsole
• use payload/linux/x64/shell_bind_tcp_random_port
• generate

[geyslan]

Please let me know if I can help explaining or fixing the proposal. Thank you.

[bwatters-r7]

Honestly, you had me at metasm.

[bwatters-r7]

msf6 > use payload/linux/x64/shell_bind_tcp_random_port 
msf6 payload(linux/x64/shell_bind_tcp_random_port) > show options

Module options (payload/linux/x64/shell_bind_tcp_random_port):

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

msf6 payload(linux/x64/shell_bind_tcp_random_port) > generate -f elf -o shellbindx64.elf
[*] Writing 173 bytes to shellbindx64.elf...
msf6 payload(linux/x64/shell_bind_tcp_random_port) > 

tmoose@ubuntu:~$ netstat -antp
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
...
tcp        0      0 0.0.0.0:34989           0.0.0.0:*               LISTEN      5767/./shellbindx64 
...
tmoose@ubuntu:~$ nc 127.0.0.1 34989
dir
CODE_OF_CONDUCT.md
CONTRIBUTING.md
COPYING
CURRENT.md
Dockerfile
Gemfile
Gemfile.local.example
Gemfile.lock
Gemfile.lock.orig
LICENSE
LICENSE_GEMS
README.md
Rakefile
Vagrantfile
app
b64
client.rb
comments.txt

[bwatters-r7]

Release notes

Reduced the size of the linux/x64/shell_bind_tcp_random_port payload while maintaining the functionality.