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
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
use crate::common_state::{CommonState, Context, IoState, State};
use crate::enums::{AlertDescription, ContentType};
use crate::error::{Error, PeerMisbehaved};
#[cfg(feature = "logging")]
use crate::log::trace;
use crate::msgs::deframer::{Deframed, MessageDeframer};
use crate::msgs::handshake::Random;
use crate::msgs::message::{Message, MessagePayload, PlainMessage};
#[cfg(feature = "secret_extraction")]
use crate::suites::{ExtractedSecrets, PartiallyExtractedSecrets};
use crate::vecbuf::ChunkVecBuffer;

use std::fmt::Debug;
use std::io;
use std::mem;
use std::ops::{Deref, DerefMut};

/// A client or server connection.
#[derive(Debug)]
pub enum Connection {
    /// A client connection
    Client(crate::client::ClientConnection),
    /// A server connection
    Server(crate::server::ServerConnection),
}

impl Connection {
    /// Read TLS content from `rd`.
    ///
    /// See [`ConnectionCommon::read_tls()`] for more information.
    pub fn read_tls(&mut self, rd: &mut dyn io::Read) -> Result<usize, io::Error> {
        match self {
            Self::Client(conn) => conn.read_tls(rd),
            Self::Server(conn) => conn.read_tls(rd),
        }
    }

    /// Writes TLS messages to `wr`.
    ///
    /// See [`ConnectionCommon::write_tls()`] for more information.
    pub fn write_tls(&mut self, wr: &mut dyn io::Write) -> Result<usize, io::Error> {
        self.sendable_tls.write_to(wr)
    }

    /// Returns an object that allows reading plaintext.
    pub fn reader(&mut self) -> Reader {
        match self {
            Self::Client(conn) => conn.reader(),
            Self::Server(conn) => conn.reader(),
        }
    }

    /// Returns an object that allows writing plaintext.
    pub fn writer(&mut self) -> Writer {
        match self {
            Self::Client(conn) => Writer::new(&mut **conn),
            Self::Server(conn) => Writer::new(&mut **conn),
        }
    }

    /// Processes any new packets read by a previous call to [`Connection::read_tls`].
    ///
    /// See [`ConnectionCommon::process_new_packets()`] for more information.
    pub fn process_new_packets(&mut self) -> Result<IoState, Error> {
        match self {
            Self::Client(conn) => conn.process_new_packets(),
            Self::Server(conn) => conn.process_new_packets(),
        }
    }

    /// Derives key material from the agreed connection secrets.
    ///
    /// See [`ConnectionCommon::export_keying_material()`] for more information.
    pub fn export_keying_material<T: AsMut<[u8]>>(
        &self,
        output: T,
        label: &[u8],
        context: Option<&[u8]>,
    ) -> Result<T, Error> {
        match self {
            Self::Client(conn) => conn.export_keying_material(output, label, context),
            Self::Server(conn) => conn.export_keying_material(output, label, context),
        }
    }

    /// Extract secrets, to set up kTLS for example
    #[cfg(feature = "secret_extraction")]
    #[cfg_attr(docsrs, doc(cfg(feature = "secret_extraction")))]
    pub fn extract_secrets(self) -> Result<ExtractedSecrets, Error> {
        match self {
            Self::Client(conn) => conn.extract_secrets(),
            Self::Server(conn) => conn.extract_secrets(),
        }
    }

    /// This function uses `io` to complete any outstanding IO for this connection.
    ///
    /// See [`ConnectionCommon::complete_io()`] for more information.
    pub fn complete_io<T>(&mut self, io: &mut T) -> Result<(usize, usize), io::Error>
    where
        Self: Sized,
        T: io::Read + io::Write,
    {
        match self {
            Self::Client(conn) => conn.complete_io(io),
            Self::Server(conn) => conn.complete_io(io),
        }
    }
}

impl Deref for Connection {
    type Target = CommonState;

    fn deref(&self) -> &Self::Target {
        match self {
            Self::Client(conn) => &conn.core.common_state,
            Self::Server(conn) => &conn.core.common_state,
        }
    }
}

impl DerefMut for Connection {
    fn deref_mut(&mut self) -> &mut Self::Target {
        match self {
            Self::Client(conn) => &mut conn.core.common_state,
            Self::Server(conn) => &mut conn.core.common_state,
        }
    }
}

/// A structure that implements [`std::io::Read`] for reading plaintext.
pub struct Reader<'a> {
    received_plaintext: &'a mut ChunkVecBuffer,
    peer_cleanly_closed: bool,
    has_seen_eof: bool,
}

impl<'a> io::Read for Reader<'a> {
    /// Obtain plaintext data received from the peer over this TLS connection.
    ///
    /// If the peer closes the TLS session cleanly, this returns `Ok(0)`  once all
    /// the pending data has been read. No further data can be received on that
    /// connection, so the underlying TCP connection should be half-closed too.
    ///
    /// If the peer closes the TLS session uncleanly (a TCP EOF without sending a
    /// `close_notify` alert) this function returns `Err(ErrorKind::UnexpectedEof.into())`
    /// once any pending data has been read.
    ///
    /// Note that support for `close_notify` varies in peer TLS libraries: many do not
    /// support it and uncleanly close the TCP connection (this might be
    /// vulnerable to truncation attacks depending on the application protocol).
    /// This means applications using rustls must both handle EOF
    /// from this function, *and* unexpected EOF of the underlying TCP connection.
    ///
    /// If there are no bytes to read, this returns `Err(ErrorKind::WouldBlock.into())`.
    ///
    /// You may learn the number of bytes available at any time by inspecting
    /// the return of [`Connection::process_new_packets`].
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let len = self.received_plaintext.read(buf)?;

        if len == 0 && !buf.is_empty() {
            // No bytes available:
            match (self.peer_cleanly_closed, self.has_seen_eof) {
                // cleanly closed; don't care about TCP EOF: express this as Ok(0)
                (true, _) => {}
                // unclean closure
                (false, true) => return Err(io::ErrorKind::UnexpectedEof.into()),
                // connection still going, but need more data: signal `WouldBlock` so that
                // the caller knows this
                (false, false) => return Err(io::ErrorKind::WouldBlock.into()),
            }
        }

        Ok(len)
    }

    /// Obtain plaintext data received from the peer over this TLS connection.
    ///
    /// If the peer closes the TLS session, this returns `Ok(())` without filling
    /// any more of the buffer once all the pending data has been read. No further
    /// data can be received on that connection, so the underlying TCP connection
    /// should be half-closed too.
    ///
    /// If the peer closes the TLS session uncleanly (a TCP EOF without sending a
    /// `close_notify` alert) this function returns `Err(ErrorKind::UnexpectedEof.into())`
    /// once any pending data has been read.
    ///
    /// Note that support for `close_notify` varies in peer TLS libraries: many do not
    /// support it and uncleanly close the TCP connection (this might be
    /// vulnerable to truncation attacks depending on the application protocol).
    /// This means applications using rustls must both handle EOF
    /// from this function, *and* unexpected EOF of the underlying TCP connection.
    ///
    /// If there are no bytes to read, this returns `Err(ErrorKind::WouldBlock.into())`.
    ///
    /// You may learn the number of bytes available at any time by inspecting
    /// the return of [`Connection::process_new_packets`].
    #[cfg(read_buf)]
    fn read_buf(&mut self, mut cursor: core::io::BorrowedCursor<'_>) -> io::Result<()> {
        let before = cursor.written();
        self.received_plaintext
            .read_buf(cursor.reborrow())?;
        let len = cursor.written() - before;

        if len == 0 && cursor.capacity() > 0 {
            // No bytes available:
            match (self.peer_cleanly_closed, self.has_seen_eof) {
                // cleanly closed; don't care about TCP EOF: express this as Ok(0)
                (true, _) => {}
                // unclean closure
                (false, true) => return Err(io::ErrorKind::UnexpectedEof.into()),
                // connection still going, but need more data: signal `WouldBlock` so that
                // the caller knows this
                (false, false) => return Err(io::ErrorKind::WouldBlock.into()),
            }
        }

        Ok(())
    }
}

/// Internal trait implemented by the [`ServerConnection`]/[`ClientConnection`]
/// allowing them to be the subject of a [`Writer`].
pub(crate) trait PlaintextSink {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize>;
    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize>;
    fn flush(&mut self) -> io::Result<()>;
}

impl<T> PlaintextSink for ConnectionCommon<T> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        Ok(self.send_some_plaintext(buf))
    }

    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
        let mut sz = 0;
        for buf in bufs {
            sz += self.send_some_plaintext(buf);
        }
        Ok(sz)
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

/// A structure that implements [`std::io::Write`] for writing plaintext.
pub struct Writer<'a> {
    sink: &'a mut dyn PlaintextSink,
}

impl<'a> Writer<'a> {
    /// Create a new Writer.
    ///
    /// This is not an external interface.  Get one of these objects
    /// from [`Connection::writer`].
    pub(crate) fn new(sink: &'a mut dyn PlaintextSink) -> Self {
        Writer { sink }
    }
}

impl<'a> io::Write for Writer<'a> {
    /// Send the plaintext `buf` to the peer, encrypting
    /// and authenticating it.  Once this function succeeds
    /// you should call [`Connection::write_tls`] which will output the
    /// corresponding TLS records.
    ///
    /// This function buffers plaintext sent before the
    /// TLS handshake completes, and sends it as soon
    /// as it can.  See [`CommonState::set_buffer_limit`] to control
    /// the size of this buffer.
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.sink.write(buf)
    }

    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
        self.sink.write_vectored(bufs)
    }

    fn flush(&mut self) -> io::Result<()> {
        self.sink.flush()
    }
}

#[derive(Debug)]
pub(crate) struct ConnectionRandoms {
    pub(crate) client: [u8; 32],
    pub(crate) server: [u8; 32],
}

/// How many ChangeCipherSpec messages we accept and drop in TLS1.3 handshakes.
/// The spec says 1, but implementations (namely the boringssl test suite) get
/// this wrong.  BoringSSL itself accepts up to 32.
static TLS13_MAX_DROPPED_CCS: u8 = 2u8;

impl ConnectionRandoms {
    pub(crate) fn new(client: Random, server: Random) -> Self {
        Self {
            client: client.0,
            server: server.0,
        }
    }
}

// --- Common (to client and server) connection functions ---

fn is_valid_ccs(msg: &PlainMessage) -> bool {
    // We passthrough ChangeCipherSpec messages in the deframer without decrypting them.
    // nb. this is prior to the record layer, so is unencrypted. see
    // third paragraph of section 5 in RFC8446.
    msg.typ == ContentType::ChangeCipherSpec && msg.payload.0 == [0x01]
}

/// Interface shared by client and server connections.
pub struct ConnectionCommon<Data> {
    pub(crate) core: ConnectionCore<Data>,
}

impl<Data> ConnectionCommon<Data> {
    /// Returns an object that allows reading plaintext.
    pub fn reader(&mut self) -> Reader {
        let common = &mut self.core.common_state;
        Reader {
            received_plaintext: &mut common.received_plaintext,
            // Are we done? i.e., have we processed all received messages, and received a
            // close_notify to indicate that no new messages will arrive?
            peer_cleanly_closed: common.has_received_close_notify
                && !self.core.message_deframer.has_pending(),
            has_seen_eof: common.has_seen_eof,
        }
    }

    /// Returns an object that allows writing plaintext.
    pub fn writer(&mut self) -> Writer {
        Writer::new(self)
    }

    /// This function uses `io` to complete any outstanding IO for
    /// this connection.
    ///
    /// This is a convenience function which solely uses other parts
    /// of the public API.
    ///
    /// What this means depends on the connection  state:
    ///
    /// - If the connection [`is_handshaking`], then IO is performed until
    ///   the handshake is complete.
    /// - Otherwise, if [`wants_write`] is true, [`write_tls`] is invoked
    ///   until it is all written.
    /// - Otherwise, if [`wants_read`] is true, [`read_tls`] is invoked
    ///   once.
    ///
    /// The return value is the number of bytes read from and written
    /// to `io`, respectively.
    ///
    /// This function will block if `io` blocks.
    ///
    /// Errors from TLS record handling (i.e., from [`process_new_packets`])
    /// are wrapped in an `io::ErrorKind::InvalidData`-kind error.
    ///
    /// [`is_handshaking`]: CommonState::is_handshaking
    /// [`wants_read`]: CommonState::wants_read
    /// [`wants_write`]: CommonState::wants_write
    /// [`write_tls`]: ConnectionCommon::write_tls
    /// [`read_tls`]: ConnectionCommon::read_tls
    /// [`process_new_packets`]: ConnectionCommon::process_new_packets
    pub fn complete_io<T>(&mut self, io: &mut T) -> Result<(usize, usize), io::Error>
    where
        Self: Sized,
        T: io::Read + io::Write,
    {
        let mut eof = false;
        let mut wrlen = 0;
        let mut rdlen = 0;

        loop {
            let until_handshaked = self.is_handshaking();

            if !self.wants_write() && !self.wants_read() {
                // We will make no further progress.
                return Ok((rdlen, wrlen));
            }

            while self.wants_write() {
                wrlen += self.write_tls(io)?;
            }
            io.flush()?;

            if !until_handshaked && wrlen > 0 {
                return Ok((rdlen, wrlen));
            }

            while !eof && self.wants_read() {
                let read_size = match self.read_tls(io) {
                    Ok(0) => {
                        eof = true;
                        Some(0)
                    }
                    Ok(n) => {
                        rdlen += n;
                        Some(n)
                    }
                    Err(ref err) if err.kind() == io::ErrorKind::Interrupted => None, // nothing to do
                    Err(err) => return Err(err),
                };
                if read_size.is_some() {
                    break;
                }
            }

            match self.process_new_packets() {
                Ok(_) => {}
                Err(e) => {
                    // In case we have an alert to send describing this error,
                    // try a last-gasp write -- but don't predate the primary
                    // error.
                    let _ignored = self.write_tls(io);
                    let _ignored = io.flush();

                    return Err(io::Error::new(io::ErrorKind::InvalidData, e));
                }
            };

            // if we're doing IO until handshaked, and we believe we've finished handshaking,
            // but process_new_packets() has queued TLS data to send, loop around again to write
            // the queued messages.
            if until_handshaked && !self.is_handshaking() && self.wants_write() {
                continue;
            }

            match (eof, until_handshaked, self.is_handshaking()) {
                (_, true, false) => return Ok((rdlen, wrlen)),
                (_, false, _) => return Ok((rdlen, wrlen)),
                (true, true, true) => return Err(io::Error::from(io::ErrorKind::UnexpectedEof)),
                (..) => {}
            }
        }
    }

    /// Extract the first handshake message.
    ///
    /// This is a shortcut to the `process_new_packets()` -> `process_msg()` ->
    /// `process_handshake_messages()` path, specialized for the first handshake message.
    pub(crate) fn first_handshake_message(&mut self) -> Result<Option<Message>, Error> {
        match self
            .core
            .deframe(None)?
            .map(Message::try_from)
        {
            Some(Ok(msg)) => Ok(Some(msg)),
            Some(Err(err)) => Err(self.send_fatal_alert(AlertDescription::DecodeError, err)),
            None => Ok(None),
        }
    }

    pub(crate) fn replace_state(&mut self, new: Box<dyn State<Data>>) {
        self.core.state = Ok(new);
    }

    /// Processes any new packets read by a previous call to
    /// [`Connection::read_tls`].
    ///
    /// Errors from this function relate to TLS protocol errors, and
    /// are fatal to the connection.  Future calls after an error will do
    /// no new work and will return the same error. After an error is
    /// received from [`process_new_packets`], you should not call [`read_tls`]
    /// any more (it will fill up buffers to no purpose). However, you
    /// may call the other methods on the connection, including `write`,
    /// `send_close_notify`, and `write_tls`. Most likely you will want to
    /// call `write_tls` to send any alerts queued by the error and then
    /// close the underlying connection.
    ///
    /// Success from this function comes with some sundry state data
    /// about the connection.
    ///
    /// [`read_tls`]: Connection::read_tls
    /// [`process_new_packets`]: Connection::process_new_packets
    #[inline]
    pub fn process_new_packets(&mut self) -> Result<IoState, Error> {
        self.core.process_new_packets()
    }

    /// Read TLS content from `rd` into the internal buffer.
    ///
    /// Due to the internal buffering, `rd` can supply TLS messages in arbitrary-sized chunks (like
    /// a socket or pipe might).
    ///
    /// You should call [`process_new_packets()`] each time a call to this function succeeds in order
    /// to empty the incoming TLS data buffer.
    ///
    /// This function returns `Ok(0)` when the underlying `rd` does so. This typically happens when
    /// a socket is cleanly closed, or a file is at EOF. Errors may result from the IO done through
    /// `rd`; additionally, errors of `ErrorKind::Other` are emitted to signal backpressure:
    ///
    /// * In order to empty the incoming TLS data buffer, you should call [`process_new_packets()`]
    ///   each time a call to this function succeeds.
    /// * In order to empty the incoming plaintext data buffer, you should empty it through
    ///   the [`reader()`] after the call to [`process_new_packets()`].
    ///
    /// [`process_new_packets()`]: ConnectionCommon::process_new_packets
    /// [`reader()`]: ConnectionCommon::reader
    pub fn read_tls(&mut self, rd: &mut dyn io::Read) -> Result<usize, io::Error> {
        if self.received_plaintext.is_full() {
            return Err(io::Error::new(
                io::ErrorKind::Other,
                "received plaintext buffer full",
            ));
        }

        let res = self.core.message_deframer.read(rd);
        if let Ok(0) = res {
            self.has_seen_eof = true;
        }
        res
    }

    /// Writes TLS messages to `wr`.
    ///
    /// On success, this function returns `Ok(n)` where `n` is a number of bytes written to `wr`
    /// (after encoding and encryption).
    ///
    /// After this function returns, the connection buffer may not yet be fully flushed. The
    /// [`CommonState::wants_write`] function can be used to check if the output buffer is empty.
    pub fn write_tls(&mut self, wr: &mut dyn io::Write) -> Result<usize, io::Error> {
        self.sendable_tls.write_to(wr)
    }

    /// Derives key material from the agreed connection secrets.
    ///
    /// This function fills in `output` with `output.len()` bytes of key
    /// material derived from the master session secret using `label`
    /// and `context` for diversification. Ownership of the buffer is taken
    /// by the function and returned via the Ok result to ensure no key
    /// material leaks if the function fails.
    ///
    /// See RFC5705 for more details on what this does and is for.
    ///
    /// For TLS1.3 connections, this function does not use the
    /// "early" exporter at any point.
    ///
    /// This function fails if called prior to the handshake completing;
    /// check with [`CommonState::is_handshaking`] first.
    #[inline]
    pub fn export_keying_material<T: AsMut<[u8]>>(
        &self,
        output: T,
        label: &[u8],
        context: Option<&[u8]>,
    ) -> Result<T, Error> {
        self.core
            .export_keying_material(output, label, context)
    }

    /// Extract secrets, so they can be used when configuring kTLS, for example.
    #[cfg(feature = "secret_extraction")]
    #[cfg_attr(docsrs, doc(cfg(feature = "secret_extraction")))]
    pub fn extract_secrets(self) -> Result<ExtractedSecrets, Error> {
        if !self.enable_secret_extraction {
            return Err(Error::General("Secret extraction is disabled".into()));
        }

        let st = self.core.state?;

        let record_layer = self.core.common_state.record_layer;
        let PartiallyExtractedSecrets { tx, rx } = st.extract_secrets()?;
        Ok(ExtractedSecrets {
            tx: (record_layer.write_seq(), tx),
            rx: (record_layer.read_seq(), rx),
        })
    }
}

impl<'a, Data> From<&'a mut ConnectionCommon<Data>> for Context<'a, Data> {
    fn from(conn: &'a mut ConnectionCommon<Data>) -> Self {
        Self {
            common: &mut conn.core.common_state,
            data: &mut conn.core.data,
        }
    }
}

impl<T> Deref for ConnectionCommon<T> {
    type Target = CommonState;

    fn deref(&self) -> &Self::Target {
        &self.core.common_state
    }
}

impl<T> DerefMut for ConnectionCommon<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.core.common_state
    }
}

impl<Data> From<ConnectionCore<Data>> for ConnectionCommon<Data> {
    fn from(core: ConnectionCore<Data>) -> Self {
        Self { core }
    }
}

pub(crate) struct ConnectionCore<Data> {
    pub(crate) state: Result<Box<dyn State<Data>>, Error>,
    pub(crate) data: Data,
    pub(crate) common_state: CommonState,
    pub(crate) message_deframer: MessageDeframer,
}

impl<Data> ConnectionCore<Data> {
    pub(crate) fn new(state: Box<dyn State<Data>>, data: Data, common_state: CommonState) -> Self {
        Self {
            state: Ok(state),
            data,
            common_state,
            message_deframer: MessageDeframer::default(),
        }
    }

    pub(crate) fn process_new_packets(&mut self) -> Result<IoState, Error> {
        let mut state = match mem::replace(&mut self.state, Err(Error::HandshakeNotComplete)) {
            Ok(state) => state,
            Err(e) => {
                self.state = Err(e.clone());
                return Err(e);
            }
        };

        while let Some(msg) = self.deframe(Some(&*state))? {
            match self.process_msg(msg, state) {
                Ok(new) => state = new,
                Err(e) => {
                    self.state = Err(e.clone());
                    return Err(e);
                }
            }
        }

        self.state = Ok(state);
        Ok(self.common_state.current_io_state())
    }

    /// Pull a message out of the deframer and send any messages that need to be sent as a result.
    fn deframe(&mut self, state: Option<&dyn State<Data>>) -> Result<Option<PlainMessage>, Error> {
        match self
            .message_deframer
            .pop(&mut self.common_state.record_layer)
        {
            Ok(Some(Deframed {
                want_close_before_decrypt,
                aligned,
                trial_decryption_finished,
                message,
            })) => {
                if want_close_before_decrypt {
                    self.common_state.send_close_notify();
                }

                if trial_decryption_finished {
                    self.common_state
                        .record_layer
                        .finish_trial_decryption();
                }

                self.common_state.aligned_handshake = aligned;
                Ok(Some(message))
            }
            Ok(None) => Ok(None),
            Err(err @ Error::InvalidMessage(_)) => {
                #[cfg(feature = "quic")]
                if self.common_state.is_quic() {
                    self.common_state.quic.alert = Some(AlertDescription::DecodeError);
                }

                Err(if !self.common_state.is_quic() {
                    self.common_state
                        .send_fatal_alert(AlertDescription::DecodeError, err)
                } else {
                    err
                })
            }
            Err(err @ Error::PeerSentOversizedRecord) => Err(self
                .common_state
                .send_fatal_alert(AlertDescription::RecordOverflow, err)),
            Err(err @ Error::DecryptError) => {
                if let Some(state) = state {
                    state.handle_decrypt_error();
                }
                Err(self
                    .common_state
                    .send_fatal_alert(AlertDescription::BadRecordMac, err))
            }
            Err(e) => Err(e),
        }
    }

    fn process_msg(
        &mut self,
        msg: PlainMessage,
        state: Box<dyn State<Data>>,
    ) -> Result<Box<dyn State<Data>>, Error> {
        // Drop CCS messages during handshake in TLS1.3
        if msg.typ == ContentType::ChangeCipherSpec
            && !self
                .common_state
                .may_receive_application_data
            && self.common_state.is_tls13()
        {
            if !is_valid_ccs(&msg)
                || self.common_state.received_middlebox_ccs > TLS13_MAX_DROPPED_CCS
            {
                // "An implementation which receives any other change_cipher_spec value or
                //  which receives a protected change_cipher_spec record MUST abort the
                //  handshake with an "unexpected_message" alert."
                return Err(self.common_state.send_fatal_alert(
                    AlertDescription::UnexpectedMessage,
                    PeerMisbehaved::IllegalMiddleboxChangeCipherSpec,
                ));
            } else {
                self.common_state.received_middlebox_ccs += 1;
                trace!("Dropping CCS");
                return Ok(state);
            }
        }

        // Now we can fully parse the message payload.
        let msg = match Message::try_from(msg) {
            Ok(msg) => msg,
            Err(err) => {
                return Err(self
                    .common_state
                    .send_fatal_alert(AlertDescription::DecodeError, err));
            }
        };

        // For alerts, we have separate logic.
        if let MessagePayload::Alert(alert) = &msg.payload {
            self.common_state.process_alert(alert)?;
            return Ok(state);
        }

        self.common_state
            .process_main_protocol(msg, state, &mut self.data)
    }

    pub(crate) fn export_keying_material<T: AsMut<[u8]>>(
        &self,
        mut output: T,
        label: &[u8],
        context: Option<&[u8]>,
    ) -> Result<T, Error> {
        match self.state.as_ref() {
            Ok(st) => st
                .export_keying_material(output.as_mut(), label, context)
                .map(|_| output),
            Err(e) => Err(e.clone()),
        }
    }
}

/// Data specific to the peer's side (client or server).
pub trait SideData {}