server: let callback return HTTP error messages

Signed-off-by: Alexey Galakhov <agalakhov@snapview.de>

Cargo.toml

@@ -19,6 +19,7 @@ tls = ["native-tls"]
 base64 = "0.10.0"
 byteorder = "1.2.3"
 bytes = "0.4.8"
+http = "0.1.17"
 httparse = "1.3.1"
 input_buffer = "0.2.0"
 log = "0.4.2"

examples/callback-error.rs

@@ -0,0 +1,24 @@
+extern crate tungstenite;
+
+use std::thread::spawn;
+use std::net::TcpListener;
+
+use tungstenite::accept_hdr;
+use tungstenite::handshake::server::{Request, ErrorResponse};
+use tungstenite::http::StatusCode;
+
+fn main() {
+    let server = TcpListener::bind("127.0.0.1:3012").unwrap();
+    for stream in server.incoming() {
+        spawn(move || {
+            let callback = |_req: &Request| {
+                Err(ErrorResponse {
+                    error_code: StatusCode::FORBIDDEN,
+                    headers: None,
+                    body: Some("Access denied".into()),
+                })
+            };
+            accept_hdr(stream.unwrap(), callback).unwrap_err();
+        });
+    }
+}

src/handshake/server.rs

@@ -3,9 +3,11 @@
 use std::fmt::Write as FmtWrite;
 use std::io::{Read, Write};
 use std::marker::PhantomData;
+use std::result::Result as StdResult;
 
 use httparse;
 use httparse::Status;
+use http::StatusCode;
 
 use error::{Error, Result};
 use protocol::{WebSocket, WebSocketConfig, Role};
@@ -35,16 +37,21 @@ impl Request {
             Sec-WebSocket-Accept: {}\r\n",
             convert_key(key)?
         );
-        if let Some(eh) = extra_headers {
-            for (k, v) in eh {
-                write!(reply, "{}: {}\r\n", k, v).unwrap();
-            }
-        }
-        write!(reply, "\r\n").unwrap();
+        add_headers(&mut reply, extra_headers);
         Ok(reply.into())
     }
 }
 
+fn add_headers(reply: &mut impl FmtWrite, extra_headers: Option<ExtraHeaders>) {
+    if let Some(eh) = extra_headers {
+        for (k, v) in eh {
+            write!(reply, "{}: {}\r\n", k, v).unwrap();
+        }
+    }
+    write!(reply, "\r\n").unwrap();
+}
+
+
 impl TryParse for Request {
     fn try_parse(buf: &[u8]) -> Result<Option<(usize, Self)>> {
         let mut hbuffer = [httparse::EMPTY_HEADER; MAX_HEADERS];
@@ -71,6 +78,30 @@ impl<'h, 'b: 'h> FromHttparse<httparse::Request<'h, 'b>> for Request {
     }
 }
 
+/// Extra headers for responses.
+pub type ExtraHeaders = Vec<(String, String)>;
+
+/// An error response sent to the client.
+#[derive(Debug)]
+pub struct ErrorResponse {
+    /// HTTP error code.
+    pub error_code: StatusCode,
+    /// Extra response headers, if any.
+    pub headers: Option<ExtraHeaders>,
+    /// REsponse body, if any.
+    pub body: Option<String>,
+}
+
+impl From<StatusCode> for ErrorResponse {
+    fn from(error_code: StatusCode) -> Self {
+        ErrorResponse {
+            error_code,
+            headers: None,
+            body: None,
+        }
+    }
+}
+
 /// The callback trait.
 ///
 /// The callback is called when the server receives an incoming WebSocket
@@ -81,11 +112,11 @@ pub trait Callback: Sized {
     /// Called whenever the server read the request from the client and is ready to reply to it.
     /// May return additional reply headers.
     /// Returning an error resulting in rejecting the incoming connection.
-    fn on_request(self, request: &Request) -> Result<Option<Vec<(String, String)>>>;
+    fn on_request(self, request: &Request) -> StdResult<Option<ExtraHeaders>, ErrorResponse>;
 }
 
-impl<F> Callback for F where F: FnOnce(&Request) -> Result<Option<Vec<(String, String)>>> {
-    fn on_request(self, request: &Request) -> Result<Option<Vec<(String, String)>>> {
+impl<F> Callback for F where F: FnOnce(&Request) -> StdResult<Option<ExtraHeaders>, ErrorResponse> {
+    fn on_request(self, request: &Request) -> StdResult<Option<ExtraHeaders>, ErrorResponse> {
         self(request)
     }
 }
@@ -95,7 +126,7 @@ impl<F> Callback for F where F: FnOnce(&Request) -> Result<Option<Vec<(String, S
 pub struct NoCallback;
 
 impl Callback for NoCallback {
-    fn on_request(self, _request: &Request) -> Result<Option<Vec<(String, String)>>> {
+    fn on_request(self, _request: &Request) -> StdResult<Option<ExtraHeaders>, ErrorResponse> {
         Ok(None)
     }
 }
@@ -110,6 +141,8 @@ pub struct ServerHandshake<S, C> {
     callback: Option<C>,
     /// WebSocket configuration.
     config: Option<WebSocketConfig>,
+    /// Error code/flag. If set, an error will be returned after sending response to the client.
+    error_code: Option<u16>,
     /// Internal stream type.
     _marker: PhantomData<S>,
 }
@@ -123,7 +156,12 @@ impl<S: Read + Write, C: Callback> ServerHandshake<S, C> {
         trace!("Server handshake initiated.");
         MidHandshake {
             machine: HandshakeMachine::start_read(stream),
-            role: ServerHandshake { callback: Some(callback), config, _marker: PhantomData },
+            role: ServerHandshake {
+                callback: Some(callback),
+                config,
+                error_code: None,
+                _marker: PhantomData
+            },
         }
     }
 }
@@ -141,24 +179,48 @@ impl<S: Read + Write, C: Callback> HandshakeRole for ServerHandshake<S, C> {
                 if !tail.is_empty() {
                     return Err(Error::Protocol("Junk after client request".into()))
                 }
-                let extra_headers = {
-                    if let Some(callback) = self.callback.take() {
-                        callback.on_request(&result)?
-                    } else {
-                        None
-                    }
+
+                let callback_result = if let Some(callback) = self.callback.take() {
+                    callback.on_request(&result)
+                } else {
+                    Ok(None)
                 };
-                let response = result.reply(extra_headers)?;
-                ProcessingResult::Continue(HandshakeMachine::start_write(stream, response))
+
+                match callback_result {
+                    Ok(extra_headers) => {
+                        let response = result.reply(extra_headers)?;
+                        ProcessingResult::Continue(HandshakeMachine::start_write(stream, response))
+                    }
+
+                    Err(ErrorResponse { error_code, headers, body }) => {
+                        self.error_code= Some(error_code.as_u16());
+                        let mut response = format!(
+                            "HTTP/1.1 {} {}\r\n",
+                            error_code.as_str(),
+                            error_code.canonical_reason().unwrap_or("")
+                        );
+                        add_headers(&mut response, headers);
+                        if let Some(body) = body {
+                            response += &body;
+                        }
+                        ProcessingResult::Continue(HandshakeMachine::start_write(stream, response))
+                    }
+                }
             }
+
             StageResult::DoneWriting(stream) => {
-                debug!("Server handshake done.");
-                let websocket = WebSocket::from_raw_socket(
-                    stream,
-                    Role::Server,
-                    self.config.clone(),
-                );
-                ProcessingResult::Done(websocket)
+                if let Some(err) = self.error_code.take() {
+                    debug!("Server handshake failed.");
+                    return Err(Error::Http(err));
+                } else {
+                    debug!("Server handshake done.");
+                    let websocket = WebSocket::from_raw_socket(
+                        stream,
+                        Role::Server,
+                        self.config.clone(),
+                    );
+                    ProcessingResult::Done(websocket)
+                }
             }
         })
     }

src/lib.rs

@@ -22,6 +22,8 @@ extern crate url;
 extern crate utf8;
 #[cfg(feature="tls")] extern crate native_tls;
 
+pub extern crate http;
+
 pub mod error;
 pub mod protocol;
 pub mod client;