Tunneler

This repo contains client and server that allow you to tunnel TCP traffic via other network protocols.

Currently, supported tunnels are: * DNS tunneling * TCP proxy

Main tool is writen in Rust and end-to-end tests are written in Python.

Installation

Option 1: client and server docker images

sh docker pull ghcr.io/dlemel8/tunneler-server:main docker pull ghcr.io/dlemel8/tunneler-client:main

Option 2: compile from source code

sh cargo --version || curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh cargo build --release There is also a docker file if you prefer to build a local docker image

Usage

Option 1: client and server docker images

sh docker run -e LOCAL_PORT=45301 \ -e REMOTE_PORT=5201 \ -e REMOTE_ADDRESS=localhost \ --rm -p 45301:45301 ghcr.io/dlemel8/tunneler-server:main tcp

Option 2: locally compiled binary

sh READ_TIMEOUT_IN_MILLISECONDS=100 \ IDLE_CLIENT_TIMEOUT_IN_MILLISECONDS=30000 \ LOG_LEVEL=debug \ ./target/debug/client 127.0.0.1 53 dns Run docker image or compiled binary with --help for more information

Deployment Example

This repo contains a docker compose file with the following services: * speed test, based on iperf3 server, exporting port tcp/45201 to host * speed test tcp proxy, based on tunneler server, exporting port tcp/45301 to host * speed test dns tunnel, based on tunneler server, exporting port udp/53 to host

Architecture

Protocols

DNS tunneling

We have a few challenges here: * DNS Untunneler translates UDP packets to TCP, so we need a way to identify existing clients to continue their sessions. * DNS payload must be alphanumeric. * Every message requires a response before we can send next message.

To solve those challenges, each client session starts with generating a random Client ID. Client reads data to tunnel and run it via a composition of encoders: * Data is encoded in hex. * Client ID is appended to encoded data.

Final data is then embedded in a DNS query name, requesting TXT record.

Server extracts original data and get or create Client ID in an in-memory Clients Cache. Clients Cache maps Client ID into in-memory reader and writer. Original data is then forwarded using TCP to target service.

In order to handle large server responses and empty TCP ACKs, read timeout is used in both client and server. If read timeout is expired, empty message will be sent. Both client and server use idle timeout to stop forwarding and cleanup local resources.

TCP proxy

Currently, only TCP listener and forwarder are supported, so nothing is special here.

Testing

Run Unit Tests

sh cargo test --all-targets

Run End-to-End Tests

sh python3 -m pip install -r e2e_tests/requirements.txt PYTHONPATH=. python3 -m pytest -v