shootback is a reverse TCP tunnel let you access target behind NAT or firewall
反向TCP隧道, 使得NAT或防火墙后的内网机器可以被外网访问.
Consumes less than 1% CPU and 8MB memory under 800 concurrency.
slaver is single file and only depends on python(2.7/3.4+) standard library.

1. Access company/school computer(no internet IP) from home
   从家里连接公司或学校里没有独立外网IP的电脑
2. Make private network/site public.
   使内网或内网站点能从公网访问
3. Help private network penetration.
   辅助内网渗透
4. Help CTF offline competitions.
   辅助CTF线下赛, 使场外选手也获得比赛网络环境
5. Connect to device with dynamic IP, such as ADSL
   连接动态IP的设备, 如ADSL

1. requirement:

   • Master: Python3.4+, OS independent
   • Slaver: Python2.7/3.4+, OS independent
   • no external dependencies, only python std lib

2. download git clone https://github.com/aploium/shootback

3. (optional) if you need a single-file slaver.py, run python3 build_singlefile_slaver.py

4. run these command

   # master listen :10000 for slaver, :10080 for you
   python3 master.py -m 0.0.0.0:10000 -c 127.0.0.1:10080
   
   # slaver connect to master, and use example.com as tunnel target
   # ps: you can use python2 in slaver, not only py3
   python3 slaver.py -m 127.0.0.1:10000 -t example.com:80
   
   # doing request to master
   curl -v -H "host: example.com" 127.0.0.1:10080
   # -- some HTML content from example.com --
   # -- some HTML content from example.com --
   # -- some HTML content from example.com --

5. a more reality example:
   assume your master is 22.33.44.55 (just like the graph above)

   # slaver_local_ssh <---> slaver <--> master(22.33.44.55) <--> You
   
   # ---- master ----
   python3 master.py -m 0.0.0.0:10000 -c 0.0.0.0:10022
   
   # ---- slaver ----
   python(or python3) slaver.py -m 22.33.44.55:10000 -t 127.0.0.1:22
   
   # ---- YOU ----
   ssh 22.33.44.55 -p 10022

6. for more help, please see python3 master.py --help and python3 slaver.py --help

1. run in daemon:
   nohup python(or python3) slaver.py -m host:port -t host:port -q &
   or:

   # screen is a linux command
   screen
   python(or python3) slaver.py -m host:port -t host:port
   # press  ctrl-a d  to detach screen
   # and if necessary, use "screen -r" to reattach

2. ANY service using TCP is shootback-able. HTTP/FTP/Proxy/SSH/VNC/...

3. shootback itself just do the transmission job, do not handle encrypt or proxy.
   however you can use a 3rd party proxy (eg: shadowsocks) as slaver target.
   for example:
   shadowsocks_server<-->shootback_slaver<-->shootback_master<-->shadowsocks_client(socks5)

1. in windows, due to the limit of CPython select.select(), shootback can NOT handle more than 512 concurrency, you may meet
   ValueError: too many file descriptors in select()
   If you have to handle such high concurrency in windows, Anaconda-Python3 is recommend, it's limit in windows is 2048

1. in my laptop of intel I7-4710MQ, win10 x64:
   • 1.6Gbits/s of loopback transfer (using iperf), with about 5% CPU occupation.
   • 800 thread ApacheBench, with less than 1% CPU and 8MB memory consume