gost - GO Simple Tunnel
======
 
### A simple security tunnel written in Golang

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Features
------
* Listening on multiple ports
* Multi-level forward proxy - proxy chain
* Standard HTTP/HTTPS/HTTP2/SOCKS4(A)/SOCKS5 proxy protocols support
* [Support multiple tunnel types](https://docs.ginuerzh.xyz/gost/en/configuration/)
* [TLS encryption via negotiation support for SOCKS5 proxy](https://docs.ginuerzh.xyz/gost/en/socks/)
* [Tunnel UDP over TCP](https://docs.ginuerzh.xyz/gost/en/socks/)
* [Transparent TCP proxy](https://docs.ginuerzh.xyz/gost/en/redirect/)
* [Local/remote TCP/UDP port forwarding](https://docs.ginuerzh.xyz/gost/en/port-forwarding/)
* [Shadowsocks protocol](https://docs.ginuerzh.xyz/gost/en/ss/)
* [SNI proxy](https://docs.ginuerzh.xyz/gost/en/sni/)
* [Permission control](https://docs.ginuerzh.xyz/gost/en/permission/)
* [Load balancing](https://docs.ginuerzh.xyz/gost/en/load-balancing/)

Wiki: https://docs.ginuerzh.xyz/gost/en/

Google group: https://groups.google.com/d/forum/go-gost

Getting started
------

#### No forward proxy

<img src="https://ginuerzh.github.io/images/gost_01.png" />

* Standard HTTP/SOCKS5 proxy

```bash
gost -L=:8080
```

* Proxy authentication

```bash
gost -L=admin:123456@localhost:8080
```

* Multiple sets of authentication information

```bash
gost -L=localhost:8080?secrets=secrets.txt
```

The secrets parameter allows you to set multiple authentication information for HTTP/SOCKS5 proxies, the format is:

```plain
# username password

test001 123456
test002 12345678
```

* Listen on multiple ports

```bash
gost -L=http2://:443 -L=socks5://:1080 -L=ss://aes-128-cfb:123456@:8338
```

#### Forward proxy

<img src="https://ginuerzh.github.io/images/gost_02.png" />

```bash
gost -L=:8080 -F=192.168.1.1:8081
```

* Forward proxy authentication

```bash
gost -L=:8080 -F=http://admin:123456@192.168.1.1:8081
```

#### Multi-level forward proxy

<img src="https://ginuerzh.github.io/images/gost_03.png" />

```bash
gost -L=:8080 -F=quic://192.168.1.1:6121 -F=socks5+wss://192.168.1.2:1080 -F=http2://192.168.1.3:443 ... -F=a.b.c.d:NNNN
```

Gost forwards the request to a.b.c.d:NNNN through the proxy chain in the order set by -F, 
each forward proxy can be any HTTP/HTTPS/HTTP2/SOCKS4/SOCKS5/Shadowsocks type.

#### Local TCP port forwarding

```bash
gost -L=tcp://:2222/192.168.1.1:22 [-F=...]
```

The data on the local TCP port 2222 is forwarded to 192.168.1.1:22 (through the proxy chain). If the last node of the chain (the last -F parameter) is a SSH forwad tunnel, then gost will use the local port forwarding function of SSH directly:

```bash
gost -L=tcp://:2222/192.168.1.1:22 -F forward+ssh://:2222
```

#### Local UDP port forwarding

```bash
gost -L=udp://:5353/192.168.1.1:53?ttl=60 [-F=...]
```

The data on the local UDP port 5353 is forwarded to 192.168.1.1:53 (through the proxy chain). 
Each forwarding channel has a timeout period. When this time is exceeded and there is no data interaction during this time period, the channel will be closed. The timeout value can be set by the `ttl` parameter. The default value is 60 seconds.

**NOTE:** When forwarding UDP data, if there is a proxy chain, the end of the chain (the last -F parameter) must be gost SOCKS5 proxy, gost will use UDP-over-TCP to forward data.

#### Remote TCP port forwarding

```bash
gost -L=rtcp://:2222/192.168.1.1:22 [-F=... -F=socks5://172.24.10.1:1080]
```

The data on 172.24.10.1:2222 is forwarded to 192.168.1.1:22 (through the proxy chain). If the last node of the chain (the last -F parameter) is a SSH tunnel, then gost will use the remote port forwarding function of SSH directly:

```bash
gost -L=rtcp://:2222/192.168.1.1:22 -F forward+ssh://:2222
```

#### Remote UDP port forwarding

```bash
gost -L=rudp://:5353/192.168.1.1:53?ttl=60 [-F=... -F=socks5://172.24.10.1:1080]
```

The data on 172.24.10.1:5353 is forwarded to 192.168.1.1:53 (through the proxy chain).
Each forwarding channel has a timeout period. When this time is exceeded and there is no data interaction during this time period, the channel will be closed. The timeout value can be set by the `ttl` parameter. The default value is 60 seconds.

**NOTE:** When forwarding UDP data, if there is a proxy chain, the end of the chain (the last -F parameter) must be gost SOCKS5 proxy, gost will use UDP-over-TCP to forward data.

#### HTTP2

Gost HTTP2 supports two modes:

* As a standard HTTP2 proxy, and backwards-compatible with the HTTPS proxy.

* As a transport tunnel.

##### Standard proxy

Server:

```bash
gost -L=http2://:443
```

Client:

```bash
gost -L=:8080 -F=http2://server_ip:443?ping=30
```

##### Tunnel 

Server:

```bash
gost -L=h2://:443
```

Client:

```bash
gost -L=:8080 -F=h2://server_ip:443
```

#### QUIC

Support for QUIC is based on library [quic-go](https://github.com/lucas-clemente/quic-go).

Server:

```bash
gost -L=quic://:6121
```

Client:

```bash
gost -L=:8080 -F=quic://server_ip:6121
```

**NOTE:** QUIC node can only be used as the first node of the proxy chain.

#### KCP
Support for KCP is based on libraries [kcp-go](https://github.com/xtaci/kcp-go) and [kcptun](https://github.com/xtaci/kcptun).

Server:

```bash
gost -L=kcp://:8388
```

Client:

```bash
gost -L=:8080 -F=kcp://server_ip:8388
```

Gost will automatically load kcp.json configuration file from current working directory if exists, 
or you can use the parameter to specify the path to the file.

```bash
gost -L=kcp://:8388?c=/path/to/conf/file
```

**NOTE:** KCP node can only be used as the first node of the proxy chain.

#### SSH

Gost SSH supports two modes:

* As a forward tunnel, used by local/remote TCP port forwarding.

* As a transport tunnel.


##### Forward tunnel

Server:

```bash
gost -L=forward+ssh://:2222
```

Client:

```bash
gost -L=rtcp://:1222/:22 -F=forward+ssh://server_ip:2222
```

##### Transport tunnel
Server:

```bash
gost -L=ssh://:2222
```
Client:

```bash
gost -L=:8080 -F=ssh://server_ip:2222?ping=60
```

The client supports the ping parameter to enable heartbeat detection (which is disabled by default). Parameter value represents heartbeat interval seconds.

#### Transparent proxy
Iptables-based transparent proxy

```bash
gost -L=redirect://:12345 -F=http2://server_ip:443
```


#### obfs4
Contributed by [@isofew](https://github.com/isofew).

Server:

```bash
gost -L=obfs4://:443
```

When the server is running normally, the console prints out the connection address for the client to use:

```bash
obfs4://:443/?cert=4UbQjIfjJEQHPOs8vs5sagrSXx1gfrDCGdVh2hpIPSKH0nklv1e4f29r7jb91VIrq4q5Jw&iat-mode=0
```

Client:

```bash
gost -L=:8888 -F='obfs4://server_ip:443?cert=4UbQjIfjJEQHPOs8vs5sagrSXx1gfrDCGdVh2hpIPSKH0nklv1e4f29r7jb91VIrq4q5Jw&iat-mode=0'
```

Encryption Mechanism
------

#### HTTP

For HTTP, you can use TLS to encrypt the entire communication process, the HTTPS proxy:

Server:

```bash
gost -L=http+tls://:443
```

Client:

```bash
gost -L=:8080 -F=http+tls://server_ip:443
```

#### HTTP2

Gost HTTP2 proxy mode only supports the use of TLS encrypted HTTP2 protocol, does not support plaintext HTTP2.

Gost HTTP2 tunnel mode supports both encryption (h2) and plaintext (h2c) modes.

#### SOCKS5

Gost supports the standard SOCKS5 protocol methods: no-auth (0x00) and user/pass (0x02), 
and extends two methods for data encryption: tls(0x80) and tls-auth(0x82).

Server:

```bash
gost -L=socks://:1080
```

Client:

```bash
gost -L=:8080 -F=socks://server_ip:1080
```

If both ends are gosts (as example above), the data transfer will be encrypted (using tls or tls-auth). 
Otherwise, use standard SOCKS5 for communication (no-auth or user/pass).

#### Shadowsocks
Support for shadowsocks is based on library [shadowsocks-go](https://github.com/shadowsocks/shadowsocks-go).

Server:

```bash
gost -L=ss://aes-128-cfb:123456@:8338
```

Client:

```bash
gost -L=:8080 -F=ss://aes-128-cfb:123456@server_ip:8338
```

##### Shadowsocks UDP relay

Currently, only the server supports UDP Relay.

Server:

```bash
gost -L=ssu://aes-128-cfb:123456@:8338
```

#### TLS
There is built-in TLS certificate in gost, if you need to use other TLS certificate, there are two ways:

* Place two files cert.pem (public key) and key.pem (private key) in the current working directory, gost will automatically load them.

* Use the parameter to specify the path to the certificate file:

```bash
gost -L="http2://:443?cert=/path/to/my/cert/file&key=/path/to/my/key/file"
```

Client can specify `secure` parameter to perform server's certificate chain and host name verification:

```bash
gost -L=:8080 -F="http2://server_domain_name:443?secure=true"
```

Client can specify a CA certificate to allow for [Certificate Pinning](https://en.wikipedia.org/wiki/Transport_Layer_Security#Certificate_pinning):

```bash
gost -L=:8080 -F="http2://:443?ca=ca.pem"
```

Certificate Pinning is contributed by [@sheerun](https://github.com/sheerun).
