sahand12/overtls

A simple proxy tunnel, minimalist tool for bypassing the GFW.

overtls

中文版

overtls is SOCKS5 type proxy software, which realizes data transmission through TLS inside the software and supports TCP and UDP traffic forwarding at the same time.

The function is complete and the code is concise, and the core function is 1200 lines of code in total.

OverTLS is a Rust implementation of SSRoT without SSR and SS, only retaining oT, which is fast and stable.

    fun isOverTLS() : Boolean =
        over_tls_enable && method == "none" && obfs == "plain" && protocol == "origin"

Principle

In order to effectively deceive GFW, directly using TLS as a proxy protocol is the simplest way. TLS protocol is an encryption protocol, which is symmetric encryption, i.e. the client and server use the same key for encryption and decryption.

We can take advantage of this feature to encapsulate the encryption and decryption process on the client and server sides as a proxy service, so that encrypted TCP and UDP proxies can be performed under GFW surveillance.

The overtls client first establishes a TLS connection with the overtls server, and then the data exchange between the overtls client and the overtls server is encrypted.

We simply agree that the overtls client accessing a unique resource uri is considered to be a proxy, and the server will forward the packets containing this uri to the specified destination address.

This is how our proxy is achieved.

Thus, the data exchange between the overtls server and the overtls client is encrypted, while the data exchange between the overtls server and the target server is in plaintext.

In summary, we need to prepare the following things

• A VPS host with a public IP, which must be purchased by yourself.
• A domain name, which can be purchased or applied for free, and resolve the domain name to the IP of the VPS host.
• A pair of https certificates/private keys, which can be purchased or applied for free at Let's Encrypt .
• an http server software (such as nginx ), and provide site resources for masquerading purposes or acting as a front reverse proxy.

Installation

Can be compiled directly from the source code, or you can download the pre-compiled binary file from the Release page.

To compile from source code, you need to install the Rust programming language environment first, and then run the following command to compile the software.

git clone https://github.com/shadowsocksr-live/overtls.git
cd overtls
cargo build --release

Server-side one-click installation script

Before installation, please prepare a VPS host with a public IP and a domain name, and resolve the domain name to this host IP, then run the following command and follow the prompts, if everything goes smoothly, the result will be overtls server and nginx front proxy installed on your host, and apply for a certificate.

Currently only 3 CPU architectures of Linux machines are supported: x86_64, armv7 and arm64.

sudo apt install -y wget # Debian/Ubuntu
sudo yum install -y wget # CentOS
wget https://raw.githubusercontent.com/shadowsocksr-live/overtls/master/install/overtls-install.sh
chmod +x overtls-install.sh
./overtls-install.sh
sudo systemctl start overtls

Usage

Server

overtls -r server -c config.json

Client

overtls -r client -c config.json

If you want to see log info, you can create a .env file in current dir (pwd) with RUST_LOG=overtls=trace as content.

Configuration file

{
    "tunnel_path": "/secret-tunnel-path/",

    "server_settings": {
        "certfile": "/etc/mysite_cert/fullchain.pem",
        "keyfile": "/etc/mysite_cert/privkey.pem",
        "forward_addr": "http://127.0.0.1:80",
        "listen_host": "0.0.0.0",
        "listen_port": 443
    },

    "client_settings": {
        "server_host": "123.45.67.89",
        "server_port": 443,
        "server_domain": "example.com",
        "listen_host": "127.0.0.1",
        "listen_port": 1080
    }
}

The configuration file is very simple. It is common to both server and client.

• When the application is running as a server, the server_settings section is valid and the client_settings section is ignored.
• When the program is run as a client, the client_settings section is valid and the server_settings section is ignored.

The certfile and keyfile are optional, and the software will become https protocol server after the correct pairing, and the non-flip traffic will be forwarded directly to the forward_addr destination. If the certfile and keyfile are incorrectly matched or simply do not exist, you will need the help of a previous reverse proxy such as nginx to work.

If the forward_addr option does not exist, the default value is http://127.0.0.1:80, which is the port 80 on which the local nginx listens to http.

Note the tunnel_path configuration, please make sure to change it to your own unique complex string, otherwise GFW will block you immediately.

For testing purposes, the disable_tls option is provided to have the ability to disable TLS; that is, if this option exists and is true, the software will transmit traffic in plain text; for security reasons, please do not use it on official occasions.

This example shows the configuration file of the least entry, the complete configuration file can refer to config.json.

Building iOS framework

Install Rust build tools

• Install Xcode Command Line Tools: xcode-select --install
• Install Rust programming language: curl https://sh.rustup.rs -sSf | sh
• Install iOS target support: rustup target add aarch64-apple-ios aarch64-apple-ios-sim x86_64-apple-ios
• Install cbindgen tool: cargo install cbindgen

Building iOS framework

Due to an unknown reason at present, compiling Rust code from Xcode fails, so you have to manually compile it. Please run the following command in zsh (or bash):

cd overtls

cargo build --release --target aarch64-apple-ios
cargo build --release --target x86_64-apple-ios
lipo -create target/aarch64-apple-ios/release/libovertls.a target/x86_64-apple-ios/release/libovertls.a -output target/libovertls.a
cbindgen --config cbindgen.toml -l C -o target/overtls-ios.h