1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217

//!
//! A simple reverse proxy, to be used with [Hyper].
//!
//! The implementation ensures that [Hop-by-hop headers] are stripped correctly in both directions,
//! and adds the client's IP address to a comma-space-separated list of forwarding addresses in the
//! `X-Forwarded-For` header.
//!
//! The implementation is based on Go's [`httputil.ReverseProxy`].
//!
//! [Hyper]: http://hyper.rs/
//! [Hop-by-hop headers]: http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
//! [`httputil.ReverseProxy`]: https://golang.org/pkg/net/http/httputil/#ReverseProxy
//!
//! # Example
//!
//! Add these dependencies to your `Cargo.toml` file.
//!
//! ```toml
//! [dependencies]
//! hyper-reverse-proxy = "0.5"
//! hyper = { version = "0.14", features = ["full"] }
//! tokio = { version = "1", features = ["full"] }
//! ```
//!
//! The following example will set up a reverse proxy listening on `127.0.0.1:13900`,
//! and will proxy these calls:
//!
//! * `"/target/first"` will be proxied to `http://127.0.0.1:13901`
//!
//! * `"/target/second"` will be proxied to `http://127.0.0.1:13902`
//!
//! * All other URLs will be handled by `debug_request` function, that will display request information.
//!
//! ```rust,no_run
//! use hyper::server::conn::AddrStream;
//! use hyper::{Body, Request, Response, Server, StatusCode};
//! use hyper::service::{service_fn, make_service_fn};
//! use std::{convert::Infallible, net::SocketAddr};
//! use std::net::IpAddr;
//!
//! fn debug_request(req: Request<Body>) -> Result<Response<Body>, Infallible>  {
//!     let body_str = format!("{:?}", req);
//!     Ok(Response::new(Body::from(body_str)))
//! }
//!
//! async fn handle(client_ip: IpAddr, req: Request<Body>) -> Result<Response<Body>, Infallible> {
//!     if req.uri().path().starts_with("/target/first") {
//!         // will forward requests to port 13901
//!         match hyper_reverse_proxy::call(client_ip, "http://127.0.0.1:13901", req).await {
//!             Ok(response) => {Ok(response)}
//!             Err(_error) => {Ok(Response::builder()
//!                                   .status(StatusCode::INTERNAL_SERVER_ERROR)
//!                                   .body(Body::empty())
//!                                   .unwrap())}
//!         }
//!     } else if req.uri().path().starts_with("/target/second") {
//!         // will forward requests to port 13902
//!         match hyper_reverse_proxy::call(client_ip, "http://127.0.0.1:13902", req).await {
//!             Ok(response) => {Ok(response)}
//!             Err(_error) => {Ok(Response::builder()
//!                                   .status(StatusCode::INTERNAL_SERVER_ERROR)
//!                                   .body(Body::empty())
//!                                   .unwrap())}
//!         }
//!     } else {
//!         debug_request(req)
//!     }
//! }
//!
//! #[tokio::main]
//! async fn main() {
//!     let bind_addr = "127.0.0.1:8000";
//!     let addr:SocketAddr = bind_addr.parse().expect("Could not parse ip:port.");
//!
//!     let make_svc = make_service_fn(|conn: &AddrStream| {
//!         let remote_addr = conn.remote_addr().ip();
//!         async move {
//!             Ok::<_, Infallible>(service_fn(move |req| handle(remote_addr, req)))
//!         }
//!     });
//!
//!     let server = Server::bind(&addr).serve(make_svc);
//!
//!     println!("Running server on {:?}", addr);
//!
//!     if let Err(e) = server.await {
//!         eprintln!("server error: {}", e);
//!     }
//! }
//! ```
//!

use hyper::header::{HeaderMap, HeaderValue};
use hyper::http::header::{InvalidHeaderValue, ToStrError};
use hyper::http::uri::InvalidUri;
use hyper::{Body, Client, Error, Request, Response, Uri};
use lazy_static::lazy_static;
use std::net::IpAddr;
use std::str::FromStr;

#[derive(Debug)]
pub enum ProxyError {
    InvalidUri(InvalidUri),
    HyperError(Error),
    ForwardHeaderError,
}

impl From<Error> for ProxyError {
    fn from(err: Error) -> ProxyError {
        ProxyError::HyperError(err)
    }
}

impl From<InvalidUri> for ProxyError {
    fn from(err: InvalidUri) -> ProxyError {
        ProxyError::InvalidUri(err)
    }
}

impl From<ToStrError> for ProxyError {
    fn from(_err: ToStrError) -> ProxyError {
        ProxyError::ForwardHeaderError
    }
}

impl From<InvalidHeaderValue> for ProxyError {
    fn from(_err: InvalidHeaderValue) -> ProxyError {
        ProxyError::ForwardHeaderError
    }
}

fn is_hop_header(name: &str) -> bool {
    use unicase::Ascii;

    // A list of the headers, using `unicase` to help us compare without
    // worrying about the case, and `lazy_static!` to prevent reallocation
    // of the vector.
    lazy_static! {
        static ref HOP_HEADERS: Vec<Ascii<&'static str>> = vec![
            Ascii::new("Connection"),
            Ascii::new("Keep-Alive"),
            Ascii::new("Proxy-Authenticate"),
            Ascii::new("Proxy-Authorization"),
            Ascii::new("Te"),
            Ascii::new("Trailers"),
            Ascii::new("Transfer-Encoding"),
            Ascii::new("Upgrade"),
        ];
    }

    HOP_HEADERS.iter().any(|h| h == &name)
}

/// Returns a clone of the headers without the [hop-by-hop headers].
///
/// [hop-by-hop headers]: http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
fn remove_hop_headers(headers: &HeaderMap<HeaderValue>) -> HeaderMap<HeaderValue> {
    let mut result = HeaderMap::new();
    for (k, v) in headers.iter() {
        if !is_hop_header(k.as_str()) {
            result.insert(k.clone(), v.clone());
        }
    }
    result
}

fn create_proxied_response<B>(mut response: Response<B>) -> Response<B> {
    *response.headers_mut() = remove_hop_headers(response.headers());
    response
}

fn forward_uri<B>(forward_url: &str, req: &Request<B>) -> Result<Uri, InvalidUri> {
    let forward_uri = match req.uri().query() {
        Some(query) => format!("{}{}?{}", forward_url, req.uri().path(), query),
        None => format!("{}{}", forward_url, req.uri().path()),
    };

    Uri::from_str(forward_uri.as_str())
}

fn create_proxied_request<B>(
    client_ip: IpAddr,
    forward_url: &str,
    mut request: Request<B>,
) -> Result<Request<B>, ProxyError> {
    *request.headers_mut() = remove_hop_headers(request.headers());
    *request.uri_mut() = forward_uri(forward_url, &request)?;

    let x_forwarded_for_header_name = "x-forwarded-for";

    // Add forwarding information in the headers
    match request.headers_mut().entry(x_forwarded_for_header_name) {
        hyper::header::Entry::Vacant(entry) => {
            entry.insert(client_ip.to_string().parse()?);
        }

        hyper::header::Entry::Occupied(mut entry) => {
            let addr = format!("{}, {}", entry.get().to_str()?, client_ip);
            entry.insert(addr.parse()?);
        }
    }

    Ok(request)
}

pub async fn call(
    client_ip: IpAddr,
    forward_uri: &str,
    request: Request<Body>,
) -> Result<Response<Body>, ProxyError> {
    let proxied_request = create_proxied_request(client_ip, &forward_uri, request)?;

    let client = Client::new();
    let response = client.request(proxied_request).await?;
    let proxied_response = create_proxied_response(response);
    Ok(proxied_response)
}