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
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
// Copyright 2015-2016 Benjamin Fry <benjaminfry@me.com>
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

use std::borrow::Borrow;
use std::fmt::{self, Display};
use std::io;
use std::marker::PhantomData;
use std::net::SocketAddr;
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};
use std::time::{Duration, SystemTime, UNIX_EPOCH};

use futures::{Future, Stream};
use log::{debug, warn};

use crate::error::ProtoError;
use crate::op::message::NoopMessageFinalizer;
use crate::op::{MessageFinalizer, OpCode};
use crate::udp::udp_stream::{NextRandomUdpSocket, UdpSocket};
use crate::xfer::{DnsRequest, DnsRequestSender, DnsResponse, SerialMessage};
use crate::Time;

/// A UDP client stream of DNS binary packets
///
/// This stream will create a new UDP socket for every request. This is to avoid potential cache
///   poisoning during use by UDP based attacks.
#[must_use = "futures do nothing unless polled"]
pub struct UdpClientStream<S, MF = NoopMessageFinalizer>
where
    S: Send,
    MF: MessageFinalizer,
{
    name_server: SocketAddr,
    timeout: Duration,
    is_shutdown: bool,
    signer: Option<Arc<MF>>,
    marker: PhantomData<S>,
}

impl<S: Send> UdpClientStream<S, NoopMessageFinalizer> {
    /// it is expected that the resolver wrapper will be responsible for creating and managing
    ///  new UdpClients such that each new client would have a random port (reduce chance of cache
    ///  poisoning)
    ///
    /// # Return
    ///
    /// a tuple of a Future Stream which will handle sending and receiving messages, and a
    ///  handle which can be used to send messages into the stream.
    #[allow(clippy::new_ret_no_self)]
    pub fn new(name_server: SocketAddr) -> UdpClientConnect<S, NoopMessageFinalizer> {
        Self::with_timeout(name_server, Duration::from_secs(5))
    }

    /// Constructs a new UdpStream for a client to the specified SocketAddr.
    ///
    /// # Arguments
    ///
    /// * `name_server` - the IP and Port of the DNS server to connect to
    /// * `timeout` - connection timeout
    pub fn with_timeout(
        name_server: SocketAddr,
        timeout: Duration,
    ) -> UdpClientConnect<S, NoopMessageFinalizer> {
        Self::with_timeout_and_signer(name_server, timeout, None)
    }
}

impl<S: Send, MF: MessageFinalizer> UdpClientStream<S, MF> {
    /// Constructs a new TcpStream for a client to the specified SocketAddr.
    ///
    /// # Arguments
    ///
    /// * `name_server` - the IP and Port of the DNS server to connect to
    /// * `timeout` - connection timeout
    pub fn with_timeout_and_signer(
        name_server: SocketAddr,
        timeout: Duration,
        signer: Option<Arc<MF>>,
    ) -> UdpClientConnect<S, MF> {
        UdpClientConnect {
            name_server: Some(name_server),
            timeout,
            signer,
            marker: PhantomData::<S>,
        }
    }
}

impl<S: Send, MF: MessageFinalizer> Display for UdpClientStream<S, MF> {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(formatter, "UDP({})", self.name_server)
    }
}

/// creates random query_id, each socket is unique, no need for global uniqueness
fn random_query_id() -> u16 {
    use rand::distributions::{Distribution, Standard};
    let mut rand = rand::thread_rng();

    Standard.sample(&mut rand)
}

impl<S: UdpSocket + Send + 'static, MF: MessageFinalizer> DnsRequestSender
    for UdpClientStream<S, MF>
{
    type DnsResponseFuture = UdpResponse;

    fn send_message<TE: Time>(
        &mut self,
        mut message: DnsRequest,
        _cx: &mut Context,
    ) -> Self::DnsResponseFuture {
        if self.is_shutdown {
            panic!("can not send messages after stream is shutdown")
        }

        // associated the ID for this request, b/c this connection is unique to socket port, the ID
        //   does not need to be globally unique
        message.set_id(random_query_id());

        let now = match SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map_err(|_| ProtoError::from("Current time is before the Unix epoch."))
        {
            Ok(now) => now.as_secs(),
            Err(err) => {
                let err: ProtoError = err;

                return UdpResponse::complete::<_, TE>(SingleUseUdpSocket::errored(err));
            }
        };

        // TODO: truncates u64 to u32, error on overflow?
        let now = now as u32;

        // TODO: move this logic into Message::finalize?
        if let OpCode::Update = message.op_code() {
            if let Some(ref signer) = self.signer {
                if let Err(e) = message.finalize::<MF>(signer.borrow(), now) {
                    debug!("could not sign message: {}", e);
                    return UdpResponse::complete::<_, TE>(SingleUseUdpSocket::errored(e));
                }
            }
        }

        let bytes = match message.to_vec() {
            Ok(bytes) => bytes,
            Err(err) => {
                return UdpResponse::complete::<_, TE>(SingleUseUdpSocket::errored(err));
            }
        };

        let message_id = message.id();
        let message = SerialMessage::new(bytes, self.name_server);

        UdpResponse::new::<S, TE>(message, message_id, self.timeout)
    }

    fn error_response<TE: Time>(err: ProtoError) -> Self::DnsResponseFuture {
        UdpResponse::complete::<_, TE>(SingleUseUdpSocket::errored(err))
    }

    fn shutdown(&mut self) {
        self.is_shutdown = true;
    }

    fn is_shutdown(&self) -> bool {
        self.is_shutdown
    }
}

// TODO: is this impl necessary? there's nothing being driven here...
impl<S: Send, MF: MessageFinalizer> Stream for UdpClientStream<S, MF> {
    type Item = Result<(), ProtoError>;

    fn poll_next(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Option<Self::Item>> {
        // Technically the Stream doesn't actually do anything.
        if self.is_shutdown {
            Poll::Ready(None)
        } else {
            Poll::Ready(Some(Ok(())))
        }
    }
}

/// A future that resolves to
#[allow(clippy::type_complexity)]
pub struct UdpResponse(
    Pin<Box<dyn Future<Output = Result<Result<DnsResponse, ProtoError>, io::Error>> + Send>>,
);

impl UdpResponse {
    /// creates a new future for the request
    ///
    /// # Arguments
    ///
    /// * `request` - Serialized message being sent
    /// * `message_id` - Id of the message that was encoded in the serial message
    fn new<S: UdpSocket + Send + Unpin + 'static, T: Time>(
        request: SerialMessage,
        message_id: u16,
        timeout: Duration,
    ) -> Self {
        UdpResponse(T::timeout::<
            Pin<Box<dyn Future<Output = Result<DnsResponse, ProtoError>> + Send>>,
        >(
            timeout,
            Box::pin(SingleUseUdpSocket::send_serial_message::<S>(
                request, message_id,
            )),
        ))
    }

    /// ad already completed future
    fn complete<F: Future<Output = Result<DnsResponse, ProtoError>> + Send + 'static, T: Time>(
        f: F,
    ) -> Self {
        // TODO: this constructure isn't really necessary
        UdpResponse(T::timeout::<
            Pin<Box<dyn Future<Output = Result<DnsResponse, ProtoError>> + Send>>,
        >(Duration::from_secs(5), Box::pin(f)))
    }
}

impl Future for UdpResponse {
    type Output = Result<DnsResponse, ProtoError>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
        self.0
            .as_mut()
            .poll(cx)
            .map_err(ProtoError::from)
            .map(|r| r.and_then(|r| r))
    }
}

/// A future that resolves to an UdpClientStream
pub struct UdpClientConnect<S, MF = NoopMessageFinalizer>
where
    S: Send,
    MF: MessageFinalizer,
{
    name_server: Option<SocketAddr>,
    timeout: Duration,
    signer: Option<Arc<MF>>,
    marker: PhantomData<S>,
}

impl<S: Send + Unpin, MF: MessageFinalizer> Future for UdpClientConnect<S, MF> {
    type Output = Result<UdpClientStream<S, MF>, ProtoError>;

    fn poll(mut self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Self::Output> {
        // TODO: this doesn't need to be a future?
        Poll::Ready(Ok(UdpClientStream::<S, MF> {
            name_server: self
                .name_server
                .take()
                .expect("UdpClientConnect invalid state: name_server"),
            is_shutdown: false,
            timeout: self.timeout,
            signer: self.signer.take(),
            marker: PhantomData,
        }))
    }
}

struct SingleUseUdpSocket;

impl SingleUseUdpSocket {
    async fn send_serial_message<S: UdpSocket + Send>(
        msg: SerialMessage,
        msg_id: u16,
    ) -> Result<DnsResponse, ProtoError> {
        let name_server = msg.addr();
        let mut socket: S = NextRandomUdpSocket::new(&name_server).await?;
        let bytes = msg.bytes();
        let addr = &msg.addr();
        let len_sent: usize = socket.send_to(bytes, addr).await?;

        if bytes.len() != len_sent {
            return Err(ProtoError::from(format!(
                "Not all bytes of message sent, {} of {}",
                len_sent,
                bytes.len()
            )));
        }

        // TODO: limit the max number of attempted messages? this relies on a timeout to die...
        loop {
            // TODO: consider making this heap based? need to verify it matches EDNS settings
            let mut recv_buf = [0u8; 2048];

            let (len, src) = socket.recv_from(&mut recv_buf).await?;
            let response = SerialMessage::new(recv_buf.iter().take(len).cloned().collect(), src);

            // compare expected src to received packet
            let request_target = msg.addr();

            if response.addr() != request_target {
                warn!(
                    "ignoring response from {} because it does not match name_server: {}.",
                    response.addr(),
                    request_target,
                );

                // await an answer from the correct NameServer
                continue;
            }

            // TODO: match query strings from request and response?

            match response.to_message() {
                Ok(message) => {
                    if msg_id == message.id() {
                        debug!("received message id: {}", message.id());
                        return Ok(DnsResponse::from(message));
                    } else {
                        // on wrong id, attempted poison?
                        warn!(
                            "expected message id: {} got: {}, dropped",
                            msg_id,
                            message.id()
                        );

                        continue;
                    }
                }
                Err(e) => {
                    // on errors deserializing, continue
                    warn!(
                        "dropped malformed message waiting for id: {} err: {}",
                        msg_id, e
                    );

                    continue;
                }
            }
        }
    }

    // TODO: this is unnecessary
    async fn errored(err: ProtoError) -> Result<DnsResponse, ProtoError> {
        futures::future::err(err).await
    }
}

#[cfg(test)]
#[cfg(feature = "tokio-runtime")]
mod tests {
    #![allow(clippy::dbg_macro, clippy::print_stdout)]
    use crate::tests::udp_client_stream_test;
    use crate::TokioTime;
    #[cfg(not(target_os = "linux"))]
    use std::net::Ipv6Addr;
    use std::net::{IpAddr, Ipv4Addr};
    use tokio::{net::UdpSocket as TokioUdpSocket, runtime::Runtime};

    #[test]
    fn test_udp_client_stream_ipv4() {
        let io_loop = Runtime::new().expect("failed to create tokio runtime");
        udp_client_stream_test::<TokioUdpSocket, Runtime, TokioTime>(
            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
            io_loop,
        )
    }

    #[test]
    #[cfg(not(target_os = "linux"))] // ignored until Travis-CI fixes IPv6
    fn test_udp_client_stream_ipv6() {
        let io_loop = Runtime::new().expect("failed to create tokio runtime");
        udp_client_stream_test::<TokioUdpSocket, Runtime, TokioTime>(
            IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1)),
            io_loop,
        )
    }
}