li_async_h1/server/
decode.rs

1//! Process HTTP connections on the server.
2
3use std::str::FromStr;
4
5use async_dup::{Arc, Mutex};
6use async_std::io::{BufReader, Read, Write};
7use async_std::{prelude::*, task};
8use li_http_types::content::ContentLength;
9use li_http_types::headers::{EXPECT, TRANSFER_ENCODING};
10use li_http_types::{ensure, ensure_eq, format_err};
11use li_http_types::{Body, Method, Request, Url};
12
13use super::body_reader::BodyReader;
14use crate::chunked::ChunkedDecoder;
15use crate::read_notifier::ReadNotifier;
16use crate::{MAX_HEADERS, MAX_HEAD_LENGTH};
17
18const LF: u8 = b'\n';
19
20/// The number returned from httparse when the request is HTTP 1.1
21const HTTP_1_1_VERSION: u8 = 1;
22
23const CONTINUE_HEADER_VALUE: &str = "100-continue";
24const CONTINUE_RESPONSE: &[u8] = b"HTTP/1.1 100 Continue\r\n\r\n";
25
26/// Decode an HTTP request on the server.
27pub async fn decode<IO>(mut io: IO) -> li_http_types::Result<Option<(Request, BodyReader<IO>)>>
28where
29    IO: Read + Write + Clone + Send + Sync + Unpin + 'static,
30{
31    let mut reader = BufReader::new(io.clone());
32    let mut buf = Vec::new();
33    let mut headers = [httparse::EMPTY_HEADER; MAX_HEADERS];
34    let mut httparse_req = httparse::Request::new(&mut headers);
35
36    // Keep reading bytes from the stream until we hit the end of the stream.
37    loop {
38        let bytes_read = reader.read_until(LF, &mut buf).await?;
39        // No more bytes are yielded from the stream.
40        if bytes_read == 0 {
41            return Ok(None);
42        }
43
44        // Prevent CWE-400 DDOS with large HTTP Headers.
45        ensure!(
46            buf.len() < MAX_HEAD_LENGTH,
47            "Head byte length should be less than 8kb"
48        );
49
50        // We've hit the end delimiter of the stream.
51        let idx = buf.len() - 1;
52        if idx >= 3 && &buf[idx - 3..=idx] == b"\r\n\r\n" {
53            break;
54        }
55    }
56
57    // Convert our header buf into an httparse instance, and validate.
58    let status = httparse_req.parse(&buf)?;
59
60    ensure!(!status.is_partial(), "Malformed HTTP head");
61
62    // Convert httparse headers + body into a `li_http_types::Request` type.
63    let method = httparse_req.method;
64    let method = method.ok_or_else(|| format_err!("No method found"))?;
65
66    let version = httparse_req.version;
67    let version = version.ok_or_else(|| format_err!("No version found"))?;
68
69    ensure_eq!(
70        version,
71        HTTP_1_1_VERSION,
72        "Unsupported HTTP version 1.{}",
73        version
74    );
75
76    let url = url_from_httparse_req(&httparse_req)?;
77
78    let mut req = Request::new(Method::from_str(method)?, url);
79
80    req.set_version(Some(li_http_types::Version::Http1_1));
81
82    for header in httparse_req.headers.iter() {
83        req.append_header(header.name, std::str::from_utf8(header.value)?);
84    }
85
86    let content_length = ContentLength::from_headers(&req)?;
87    let transfer_encoding = req.header(TRANSFER_ENCODING);
88
89    // Return a 400 status if both Content-Length and Transfer-Encoding headers
90    // are set to prevent request smuggling attacks.
91    //
92    // https://tools.ietf.org/html/rfc7230#section-3.3.3
93    li_http_types::ensure_status!(
94        content_length.is_none() || transfer_encoding.is_none(),
95        400,
96        "Unexpected Content-Length header"
97    );
98
99    // Establish a channel to wait for the body to be read. This
100    // allows us to avoid sending 100-continue in situations that
101    // respond without reading the body, saving clients from uploading
102    // their body.
103    let (body_read_sender, body_read_receiver) = async_channel::bounded(1);
104
105    if Some(CONTINUE_HEADER_VALUE) == req.header(EXPECT).map(|h| h.as_str()) {
106        task::spawn(async move {
107            // If the client expects a 100-continue header, spawn a
108            // task to wait for the first read attempt on the body.
109            if let Ok(()) = body_read_receiver.recv().await {
110                io.write_all(CONTINUE_RESPONSE).await.ok();
111            };
112            // Since the sender is moved into the Body, this task will
113            // finish when the client disconnects, whether or not
114            // 100-continue was sent.
115        });
116    }
117
118    // Check for Transfer-Encoding
119    if transfer_encoding
120        .map(|te| te.as_str().eq_ignore_ascii_case("chunked"))
121        .unwrap_or(false)
122    {
123        let trailer_sender = req.send_trailers();
124        let reader = ChunkedDecoder::new(reader, trailer_sender);
125        let reader = Arc::new(Mutex::new(reader));
126        let reader_clone = reader.clone();
127        let reader = ReadNotifier::new(reader, body_read_sender);
128        let reader = BufReader::new(reader);
129        req.set_body(Body::from_reader(reader, None));
130        Ok(Some((req, BodyReader::Chunked(reader_clone))))
131    } else if let Some(len) = content_length {
132        let len = len.len();
133        let reader = Arc::new(Mutex::new(reader.take(len)));
134        req.set_body(Body::from_reader(
135            BufReader::new(ReadNotifier::new(reader.clone(), body_read_sender)),
136            Some(len as usize),
137        ));
138        Ok(Some((req, BodyReader::Fixed(reader))))
139    } else {
140        Ok(Some((req, BodyReader::None)))
141    }
142}
143
144fn url_from_httparse_req(req: &httparse::Request<'_, '_>) -> li_http_types::Result<Url> {
145    let path = req.path.ok_or_else(|| format_err!("No uri found"))?;
146
147    let host = req
148        .headers
149        .iter()
150        .find(|x| x.name.eq_ignore_ascii_case("host"))
151        .ok_or_else(|| format_err!("Mandatory Host header missing"))?
152        .value;
153
154    let host = std::str::from_utf8(host)?;
155
156    if path.starts_with("http://") || path.starts_with("https://") {
157        Ok(Url::parse(path)?)
158    } else if path.starts_with('/') {
159        Ok(Url::parse(&format!("http://{}{}", host, path))?)
160    } else if req.method.unwrap().eq_ignore_ascii_case("connect") {
161        Ok(Url::parse(&format!("http://{}/", path))?)
162    } else {
163        Err(format_err!("unexpected uri format"))
164    }
165}
166
167#[cfg(test)]
168mod tests {
169    use super::*;
170
171    fn httparse_req(buf: &str, f: impl Fn(httparse::Request<'_, '_>)) {
172        let mut headers = [httparse::EMPTY_HEADER; MAX_HEADERS];
173        let mut res = httparse::Request::new(&mut headers[..]);
174        res.parse(buf.as_bytes()).unwrap();
175        f(res)
176    }
177
178    #[test]
179    fn url_for_connect() {
180        httparse_req(
181            "CONNECT server.example.com:443 HTTP/1.1\r\nHost: server.example.com:443\r\n",
182            |req| {
183                let url = url_from_httparse_req(&req).unwrap();
184                assert_eq!(url.as_str(), "http://server.example.com:443/");
185            },
186        );
187    }
188
189    #[test]
190    fn url_for_host_plus_path() {
191        httparse_req(
192            "GET /some/resource HTTP/1.1\r\nHost: server.example.com:443\r\n",
193            |req| {
194                let url = url_from_httparse_req(&req).unwrap();
195                assert_eq!(url.as_str(), "http://server.example.com:443/some/resource");
196            },
197        )
198    }
199
200    #[test]
201    fn url_for_host_plus_absolute_url() {
202        httparse_req(
203            "GET http://domain.com/some/resource HTTP/1.1\r\nHost: server.example.com\r\n",
204            |req| {
205                let url = url_from_httparse_req(&req).unwrap();
206                assert_eq!(url.as_str(), "http://domain.com/some/resource"); // host header MUST be ignored according to spec
207            },
208        )
209    }
210
211    #[test]
212    fn url_for_conflicting_connect() {
213        httparse_req(
214            "CONNECT server.example.com:443 HTTP/1.1\r\nHost: conflicting.host\r\n",
215            |req| {
216                let url = url_from_httparse_req(&req).unwrap();
217                assert_eq!(url.as_str(), "http://server.example.com:443/");
218            },
219        )
220    }
221
222    #[test]
223    fn url_for_malformed_resource_path() {
224        httparse_req(
225            "GET not-a-url HTTP/1.1\r\nHost: server.example.com\r\n",
226            |req| {
227                assert!(url_from_httparse_req(&req).is_err());
228            },
229        )
230    }
231
232    #[test]
233    fn url_for_double_slash_path() {
234        httparse_req(
235            "GET //double/slashes HTTP/1.1\r\nHost: server.example.com:443\r\n",
236            |req| {
237                let url = url_from_httparse_req(&req).unwrap();
238                assert_eq!(
239                    url.as_str(),
240                    "http://server.example.com:443//double/slashes"
241                );
242            },
243        )
244    }
245    #[test]
246    fn url_for_triple_slash_path() {
247        httparse_req(
248            "GET ///triple/slashes HTTP/1.1\r\nHost: server.example.com:443\r\n",
249            |req| {
250                let url = url_from_httparse_req(&req).unwrap();
251                assert_eq!(
252                    url.as_str(),
253                    "http://server.example.com:443///triple/slashes"
254                );
255            },
256        )
257    }
258
259    #[test]
260    fn url_for_query() {
261        httparse_req(
262            "GET /foo?bar=1 HTTP/1.1\r\nHost: server.example.com:443\r\n",
263            |req| {
264                let url = url_from_httparse_req(&req).unwrap();
265                assert_eq!(url.as_str(), "http://server.example.com:443/foo?bar=1");
266            },
267        )
268    }
269
270    #[test]
271    fn url_for_anchor() {
272        httparse_req(
273            "GET /foo?bar=1#anchor HTTP/1.1\r\nHost: server.example.com:443\r\n",
274            |req| {
275                let url = url_from_httparse_req(&req).unwrap();
276                assert_eq!(
277                    url.as_str(),
278                    "http://server.example.com:443/foo?bar=1#anchor"
279                );
280            },
281        )
282    }
283}
li_async_h1/server/decode.rs

li_async_h1/server/
decode.rs
