rust-rpxy/README.md

# rpxy: A simple and ultrafast reverse-proxy for multiple host names with TLS termination, written in pure Rust

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> **WIP Project**

## Introduction

`rpxy` [ahr-pik-see] is an implementation of simple and lightweight reverse-proxy with some additional features. The implementation is based on [`hyper`](https://github.com/hyperium/hyper), [`rustls`](https://github.com/rustls/rustls) and [`tokio`](https://github.com/tokio-rs/tokio), i.e., written in pure Rust. Our `rpxy` allows to route multiple host names to appropriate backend application servers while serving TLS connections.

 As default, `rpxy` provides the *TLS connection sanitization* by correctly binding a certificate used to establish secure channel with backend application. Specifically, it always keeps the consistency between the given SNI (server name indication) in `ClientHello` of the underlying TLS and the domain name given by the overlaid HTTP HOST header (or URL in Request line) [^1]. Additionally, as a somewhat unstable feature, our `rpxy` can handle the brand-new HTTP/3 connection thanks to [`quinn`](https://github.com/quinn-rs/quinn) and [`hyperium/h3`](https://github.com/hyperium/h3).

 This project is still *work-in-progress*. But it is already working in some production environments and serves numbers of domain names. Furthermore it *significantly outperforms* NGINX and Caddy, e.g., *1.5x faster than NGINX*, in the setting of very simple HTTP reverse-proxy scenario (See [`bench`](./bench/) directory).

 [^1]: We should note that NGINX doesn't guarantee such a consistency by default. To this end, you have to add `if` statement in the configuration file in NGINX.

## Installing/Building an executable binary of `rpxy`

You can build an executable binary yourself by checking out this Git repository.

```bash
# Cloning the git repository
% git clone https://github.com/junkurihara/rust-rpxy
% cd rust-rpxy

# Update submodule hyperium/h3
% git submodule update --init

# Build
% cargo build --release
```

Then you have an executive binary `rust-rpxy/target/release/rpxy`.

Note that we do not have an option of installation via [`crates.io`](https://crates.io/), i.e., `cargo install`, at this point since some dependencies are not published yet. Alternatively, you can use `docker` image (see below) as the easiest way for `amd64` environment.

## Usage

`rpxy` always refers to a configuration file in TOML format, e.g., `config.toml`. You can find an example of the configuration file, `config-example.toml`, in this repository.

You can run `rpxy` with a configuration file like

```bash
% ./target/release/rpxy --config config.toml
```

That's all!

## Basic Configuration

### First Step: Cleartext HTTP Reverse Proxy

The most basic configuration of `config.toml` is given like the following.

```toml
listen_port = 80

[apps.app1]
server_name = 'app1.example.com'
reverse_proxy = [{ upstream = [{ location = 'app1.local:8080' }] }]
```

In the above setting, `rpxy` listens on port 80 (TCP) and serves incoming cleartext HTTP request including a `app1.example.com` in its HOST header or URL in its Request line.
For example, request messages like the followings.

```http
GET http://app1.example.com/path/to HTTP/1.1\r\n
```

or

```http
GET /path/to HTTP/1.1\r\n
HOST: app1.example.com\r\n
```

Otherwise, say, a request to `other.example.com` is simply rejected with the status code `40x`.

If you want to host multiple and distinct domain names in a single IP address/port, simply create multiple `app."<app_name>"` entries in config file like

```toml
default_application = "app1"

[app.app1]
server_name = "app1.example.com"
#...

[app.app2]
server_name = "app2.example.org"
#...
```

Here we note that by specifying `default_application` entry, *HTTP* requests will be served by the specified application if HOST header or URL in Request line doesn't match any `server_name`s in `reverse_proxy` entries. For HTTPS requests, it will be rejected since the secure connection cannot be established for the unknown server name.

#### HTTPS to Backend Application

The request message will be routed to the backend application specified with the domain name `app1.localdomain:8080` or IP address over cleartext HTTP. If the backend channel needs to serve TLS like forwarding to `https://app1.localdomain:8080`, you need to enable a `tls` option for the location.

```toml
revese_proxy = [
  { location = 'app1.localdomain:8080', tls = true }
]
```

#### Load Balancing

You can specify multiple backend locations in the `reverse_proxy` array for *load-balancing*. Currently it works in the manner of round-robin.

```toml
[apps."app_name"]
server_name = 'app1.example.com'
reverse_proxy = [
  { location = 'app1.local:8080' },
  { location = 'app2.local:8000' }
]
```

### Second Step: Terminating TLS

First of all, you need to specify a port `listen_port_tls` listening the HTTPS traffic, separately from HTTPS port (`listen_port`). Then, serving an HTTPS endpoint can be easily done for your desired application just by specifying TLS certificates and private keys in PEM files.

```toml
listen_port = 80
listen_port_tls = 443
tls = { tls_cert_path = 'localhost.crt',  tls_cert_key_path = 'localhost.key' }

[apps."app_name"]
server_name = 'app1.example.com'
reverse_proxy = [{ upstream = [{ location = 'app1.local:8080' }] }]
```

In the above setting, both cleartext HTTP requests to port 80 and ciphertext HTTPS requests to port 443 are routed to the backend `app1.local:8080` in the same fashion. If you don't need to serve cleartext requests, just remove `listen_port = 80` and specify only `listen_port_tls = 443`.

We should note that the private key specified by `tls_cert_key_path` must be *in PKCS8 format*. (See TIPS to convert PKCS1 formatted private key to PKCS8 one.)

#### Redirecting cleartext HTTP requests to HTTPS

In the current Web, we believe it is common to serve everything through HTTPS rather than HTTP, and hence *https redirection* is often used for HTTP requests. When you specify both `listen_port` and `listen_port_tls`, you can enable an option of such  redirection by making `https_redirection` true.

```toml
tls = { https_redirection = true, tls_cert_path = 'localhost.crt', tls_cert_key_path = 'localhost.key' }
```

If it is true, `rpxy` returns the status code `301` to the cleartext request with new location `https://<requested_host>/<requested_query_and_path>` served over TLS.

### Third Step: More Flexible Routing based on URL Path

`rpxy` can serves, of course, routes requests to multiple backend destination according to the path information. The routing information can be specified for each application (`server_name`) as follows.

```toml
listen_port_tls = 443

[apps.app1]
server_name = 'app1.example.com'
tls = { https_redirection = true, tls_cert_path = 'localhost.crt', tls_cert_key_path = 'localhost.key' }

[[apps.app1.reverse_proxy]]
upstream = [
  { location = 'default.backend.local' }
]

[[apps.app1.reverse_proxy]]
path = '/path'
upstream = [
  { location = 'path.backend.local' }
]

[[apps.app1.reverse_proxy]]
path = '/path/another'
replace_path = '/path'
upstream = [
  { location = 'another.backend.local' }
]
```

In the above example, a request to `https://app1.example.com/path/to?query=ok` matches the second `reverse_proxy` entry in the longest-prefix-matching manner, and will be routed to `path.backend.local` with preserving path and query information, i.e., served as `http://path.backend.local/path/to?query=ok`.

On the other hand, a request to `https://app1.example.com/path/another/xx?query=ng` matching the third entry is routed with *being rewritten its path information* specified by `replace_path` option. Namely, the matched `/path/another` part is rewritten with `/path`, and it is served as `http://another.backend.local/path/xx?query=ng`.

Requests that doesn't match any paths will be routed by the first entry that doesn't have the `path` option, which means the *default destination*. In other words, unless every `reverse_proxy` entry has an explicit `path` option, `rpxy` rejects requests that don't match any paths.

#### Simple Path-based Routing

This path-based routing option would be enough in many cases. For example, you can serve multiple applications with one domain by specifying unique path to each application. More specifically, see an example below.

```toml
[apps.app]
server_name = 'app.example.com'
#...

[[apps.app.reverse_proxy]]
path = '/subapp1'
replace_path = '/'
upstream = [ { location = 'subapp1.local' } ]

[[apps.app.reverse_proxy]]
path = '/subapp2'
replace_path = '/'
upstream = [ { location = 'subapp2.local' } ]

[[apps.app.reverse_proxy]]
path = '/subapp3'
replace_path = '/'
upstream = [ { location = 'subapp3.local' } ]
```

This example configuration explains a very frequent situation of path-based routing. When a request to `app.example.com/subappN` routes to `sbappN.local` by replacing a path part `/subappN` to `/`.

## More Options

Since it is currently a work-in-progress project, we are frequently adding new options. We first add new option entries in the `config-example.toml` as examples. So please refer to it for up-to-date options. We will prepare a comprehensive documentation for all options.

## Using `docker` Image

You can also use [`docker` image](https://hub.docker.com/r/jqtype/rpxy) instead of directly executing the binary. There are only two `docker`-specific environment variables.

- `LOG_LEVEL=debug|info|warn|error`: Log level
- `LOG_TO_FILE=true|false`: Enable logging to the log file `/var/log/rpxy/rpxy.log` using `logrotate`. You should mount `/var/log/rpxy` via `docker` volume option if enabled.

Other than them, all you need is to mount your `config.toml` as `/etc/rpxy.toml` and certificates/private keys as you like through the `docker` volume option. See [`docker-compose.yml`](./docker-compose.yml) for the detailed configuration. Note that the file path of keys and certificates must be ones in your docker container.

## Example

[`./bench`](./bench/) directory could be a very simple example of configuration of `rpxy`. This can also be an example of an example of `docker` use case.

## TIPS

### Using Private Key Issued by Let's Encrypt

If you obtain certificates and private keys from [Let's Encrypt](https://letsencrypt.org/), you have PKCS1-formatted private keys. So you need to convert such retrieved private keys into PKCS8 format to use in `rpxy`.

The most easiest way is to use `openssl` by

```bash
openssl pkcs8 -topk8 -nocrypt \
    -in yoru_domain_from_le.key \
    -inform PEM \
    -out your_domain_pkcs8.key.pem \
    -outform PEM
```

### Other TIPS

todo!

## License

`rpxy` is free, open-source software licensed under MIT License.

You can open issues for bugs you've found or features you think are missing. You can also submit pull requests to this repository.

Contributors are more than welcome!