socks5-callback-server

The purpose of this server is to enable quickly create Internet servers which allow software to automatically check if a public port needed for operation is open from the Internet.

For example, what if Caddy had an option -check-public-ports that told users if the necessary ports are open or not when running an HTTP server. This can dramatically simplify the life of end-users who are not good at using Firewalls, port-forwarding, telnet and curl for checking whether TCP services are properly presenting outside the firewall.

This server is restricted to limit it's usefulness for hackers: it only permits proxying TCP to same IP address as request is coming from. It really can't be used for much beyond checking if my firewall has a port forwarded, and there is a listening TCP service on that port.

You would general run this server on an affordable $5 or $10 virtual machine, that has a direct routable IP address on it's interfaces.

It's Dockerfied to make it simple to get going.

Default port is 60000

Docker build and rust run

Build:

docker build -t x186k/socks5-callback-server .

For non-detached testing:

docker run -p 60000:60000 x186k/socks5-callback-server

Upload to dockerhub:

docker login
docker push x186k/socks5-callback-server:latest

Run using Docker in production for ipv4 only

For 24x7 service on a cloud provider instance:

ufw allow 60000/tcp
docker run --name socks -p 60000:60000 -d --restart unless-stopped x186k/socks5-callback-server

Run using Docker in production for ipv4 and ipv6

For 24x7 service on a cloud provider instance: using host networking

ufw allow 60000/tcp
docker run --network host --name socks -d --restart unless-stopped x186k/socks5-callback-server

You may be able to get ipv4,ipv6 working without using host networking, but you have to Enable ipv6 for the Docker daemon

I've haven't tested this method of ipv6 support. Just host networking.

Testing

Test proxy is hittable. Run from outside proxy.

# replace 1.1.1.1 with proxy ip
# this should connect to proxy
curl -v telnet://1.1.1.1:60000

Make sure you can't use proxy as general proxy. Run from anywhere.

# replace 1.1.1.1 with proxy ip
# this should fail to connect to google
curl -x socks5://1.1.1.1:60000 -v http://google.com:80

Test the proxy for it's intended function. Run from outside proxy, on a box with 22/ssh open.

# replace 1.1.1.1 with proxy ip
# replace 2.2.2.2 with ip of box you are testing from, with 22 open
# this should connect
curl -x socks5://1.1.1.1:60000 -v telnet://1.1.1.1:22