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
use crate::builder::{ConfigBuilder, WantsCipherSuites};
use crate::conn::{CommonState, ConnectionCommon, Protocol, Side};
use crate::enums::{CipherSuite, ProtocolVersion, SignatureScheme};
use crate::error::Error;
use crate::kx::SupportedKxGroup;
#[cfg(feature = "logging")]
use crate::log::trace;
#[cfg(feature = "quic")]
use crate::msgs::enums::AlertDescription;
use crate::msgs::handshake::ClientExtension;
use crate::sign;
use crate::suites::SupportedCipherSuite;
use crate::verify;
use crate::versions;
#[cfg(feature = "secret_extraction")]
use crate::ExtractedSecrets;
use crate::KeyLog;

use super::hs;
#[cfg(feature = "quic")]
use crate::quic;

use std::convert::TryFrom;
use std::error::Error as StdError;
use std::marker::PhantomData;
use std::net::IpAddr;
use std::ops::{Deref, DerefMut};
use std::sync::Arc;
use std::{fmt, io, mem};

/// A trait for the ability to store client session data.
/// The keys and values are opaque.
///
/// Both the keys and values should be treated as
/// **highly sensitive data**, containing enough key material
/// to break all security of the corresponding session.
///
/// `put` is a mutating operation; this isn't expressed
/// in the type system to allow implementations freedom in
/// how to achieve interior mutability.  `Mutex` is a common
/// choice.
pub trait StoresClientSessions: Send + Sync {
    /// Stores a new `value` for `key`.  Returns `true`
    /// if the value was stored.
    fn put(&self, key: Vec<u8>, value: Vec<u8>) -> bool;

    /// Returns the latest value for `key`.  Returns `None`
    /// if there's no such value.
    fn get(&self, key: &[u8]) -> Option<Vec<u8>>;
}

/// A trait for the ability to choose a certificate chain and
/// private key for the purposes of client authentication.
pub trait ResolvesClientCert: Send + Sync {
    /// With the server-supplied acceptable issuers in `acceptable_issuers`,
    /// the server's supported signature schemes in `sigschemes`,
    /// return a certificate chain and signing key to authenticate.
    ///
    /// `acceptable_issuers` is undecoded and unverified by the rustls
    /// library, but it should be expected to contain a DER encodings
    /// of X501 NAMEs.
    ///
    /// Return None to continue the handshake without any client
    /// authentication.  The server may reject the handshake later
    /// if it requires authentication.
    fn resolve(
        &self,
        acceptable_issuers: &[&[u8]],
        sigschemes: &[SignatureScheme],
    ) -> Option<Arc<sign::CertifiedKey>>;

    /// Return true if any certificates at all are available.
    fn has_certs(&self) -> bool;
}

/// Common configuration for (typically) all connections made by
/// a program.
///
/// Making one of these can be expensive, and should be
/// once per process rather than once per connection.
///
/// These must be created via the [`ClientConfig::builder()`] function.
///
/// # Defaults
///
/// * [`ClientConfig::max_fragment_size`]: the default is `None`: TLS packets are not fragmented to a specific size.
/// * [`ClientConfig::session_storage`]: the default stores 256 sessions in memory.
/// * [`ClientConfig::alpn_protocols`]: the default is empty -- no ALPN protocol is negotiated.
/// * [`ClientConfig::key_log`]: key material is not logged.
#[derive(Clone)]
pub struct ClientConfig {
    /// List of ciphersuites, in preference order.
    pub(super) cipher_suites: Vec<SupportedCipherSuite>,

    /// List of supported key exchange algorithms, in preference order -- the
    /// first element is the highest priority.
    ///
    /// The first element in this list is the _default key share algorithm_,
    /// and in TLS1.3 a key share for it is sent in the client hello.
    pub(super) kx_groups: Vec<&'static SupportedKxGroup>,

    /// Which ALPN protocols we include in our client hello.
    /// If empty, no ALPN extension is sent.
    pub alpn_protocols: Vec<Vec<u8>>,

    /// How we store session data or tickets.
    pub session_storage: Arc<dyn StoresClientSessions>,

    /// The maximum size of TLS message we'll emit.  If None, we don't limit TLS
    /// message lengths except to the 2**16 limit specified in the standard.
    ///
    /// rustls enforces an arbitrary minimum of 32 bytes for this field.
    /// Out of range values are reported as errors from ClientConnection::new.
    ///
    /// Setting this value to the TCP MSS may improve latency for stream-y workloads.
    pub max_fragment_size: Option<usize>,

    /// How to decide what client auth certificate/keys to use.
    pub client_auth_cert_resolver: Arc<dyn ResolvesClientCert>,

    /// Whether to support RFC5077 tickets.  You must provide a working
    /// `session_storage` member for this to have any meaningful
    /// effect.
    ///
    /// The default is true.
    pub enable_tickets: bool,

    /// Supported versions, in no particular order.  The default
    /// is all supported versions.
    pub(super) versions: versions::EnabledVersions,

    /// Whether to send the Server Name Indication (SNI) extension
    /// during the client handshake.
    ///
    /// The default is true.
    pub enable_sni: bool,

    /// How to verify the server certificate chain.
    pub(super) verifier: Arc<dyn verify::ServerCertVerifier>,

    /// How to output key material for debugging.  The default
    /// does nothing.
    pub key_log: Arc<dyn KeyLog>,

    /// Allows traffic secrets to be extracted after the handshake,
    /// e.g. for kTLS setup.
    #[cfg(feature = "secret_extraction")]
    pub enable_secret_extraction: bool,

    /// Whether to send data on the first flight ("early data") in
    /// TLS 1.3 handshakes.
    ///
    /// The default is false.
    pub enable_early_data: bool,
}

impl fmt::Debug for ClientConfig {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("ClientConfig")
            .field("alpn_protocols", &self.alpn_protocols)
            .field("max_fragment_size", &self.max_fragment_size)
            .field("enable_tickets", &self.enable_tickets)
            .field("enable_sni", &self.enable_sni)
            .field("enable_early_data", &self.enable_early_data)
            .finish_non_exhaustive()
    }
}

impl ClientConfig {
    /// Create a builder to build up the client configuration.
    ///
    /// For more information, see the [`ConfigBuilder`] documentation.
    pub fn builder() -> ConfigBuilder<Self, WantsCipherSuites> {
        ConfigBuilder {
            state: WantsCipherSuites(()),
            side: PhantomData::default(),
        }
    }

    #[doc(hidden)]
    /// We support a given TLS version if it's quoted in the configured
    /// versions *and* at least one ciphersuite for this version is
    /// also configured.
    pub fn supports_version(&self, v: ProtocolVersion) -> bool {
        self.versions.contains(v)
            && self
                .cipher_suites
                .iter()
                .any(|cs| cs.version().version == v)
    }

    /// Access configuration options whose use is dangerous and requires
    /// extra care.
    #[cfg(feature = "dangerous_configuration")]
    pub fn dangerous(&mut self) -> danger::DangerousClientConfig {
        danger::DangerousClientConfig { cfg: self }
    }

    pub(super) fn find_cipher_suite(&self, suite: CipherSuite) -> Option<SupportedCipherSuite> {
        self.cipher_suites
            .iter()
            .copied()
            .find(|&scs| scs.suite() == suite)
    }
}

/// Encodes ways a client can know the expected name of the server.
///
/// This currently covers knowing the DNS name of the server, but
/// will be extended in the future to supporting privacy-preserving names
/// for the server ("ECH").  For this reason this enum is `non_exhaustive`.
///
/// # Making one
///
/// If you have a DNS name as a `&str`, this type implements `TryFrom<&str>`,
/// so you can do:
///
/// ```
/// # use std::convert::{TryInto, TryFrom};
/// # use rustls::ServerName;
/// ServerName::try_from("example.com").expect("invalid DNS name");
///
/// // or, alternatively...
///
/// let x = "example.com".try_into().expect("invalid DNS name");
/// # let _: ServerName = x;
/// ```
#[non_exhaustive]
#[derive(Clone, Debug, Eq, Hash, PartialEq)]
pub enum ServerName {
    /// The server is identified by a DNS name.  The name
    /// is sent in the TLS Server Name Indication (SNI)
    /// extension.
    DnsName(verify::DnsName),

    /// The server is identified by an IP address. SNI is not
    /// done.
    IpAddress(IpAddr),
}

impl ServerName {
    /// Return the name that should go in the SNI extension.
    /// If [`None`] is returned, the SNI extension is not included
    /// in the handshake.
    pub(crate) fn for_sni(&self) -> Option<webpki::DnsNameRef> {
        match self {
            Self::DnsName(dns_name) => Some(dns_name.0.as_ref()),
            Self::IpAddress(_) => None,
        }
    }

    /// Return a prefix-free, unique encoding for the name.
    pub(crate) fn encode(&self) -> Vec<u8> {
        enum UniqueTypeCode {
            DnsName = 0x01,
            IpAddr = 0x02,
        }

        match self {
            Self::DnsName(dns_name) => {
                let bytes = dns_name.0.as_ref();

                let mut r = Vec::with_capacity(2 + bytes.as_ref().len());
                r.push(UniqueTypeCode::DnsName as u8);
                r.push(bytes.as_ref().len() as u8);
                r.extend_from_slice(bytes.as_ref());

                r
            }
            Self::IpAddress(address) => {
                let string = address.to_string();
                let bytes = string.as_bytes();

                let mut r = Vec::with_capacity(2 + bytes.len());
                r.push(UniqueTypeCode::IpAddr as u8);
                r.push(bytes.len() as u8);
                r.extend_from_slice(bytes);

                r
            }
        }
    }
}

/// Attempt to make a ServerName from a string by parsing
/// it as a DNS name.
impl TryFrom<&str> for ServerName {
    type Error = InvalidDnsNameError;
    fn try_from(s: &str) -> Result<Self, Self::Error> {
        match webpki::DnsNameRef::try_from_ascii_str(s) {
            Ok(dns) => Ok(Self::DnsName(verify::DnsName(dns.into()))),
            Err(webpki::InvalidDnsNameError) => match s.parse() {
                Ok(ip) => Ok(Self::IpAddress(ip)),
                Err(_) => Err(InvalidDnsNameError),
            },
        }
    }
}

/// The provided input could not be parsed because
/// it is not a syntactically-valid DNS Name.
#[derive(Debug)]
pub struct InvalidDnsNameError;

impl fmt::Display for InvalidDnsNameError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("invalid dns name")
    }
}

impl StdError for InvalidDnsNameError {}

/// Container for unsafe APIs
#[cfg(feature = "dangerous_configuration")]
pub(super) mod danger {
    use std::sync::Arc;

    use super::verify::ServerCertVerifier;
    use super::ClientConfig;

    /// Accessor for dangerous configuration options.
    #[derive(Debug)]
    #[cfg_attr(docsrs, doc(cfg(feature = "dangerous_configuration")))]
    pub struct DangerousClientConfig<'a> {
        /// The underlying ClientConfig
        pub cfg: &'a mut ClientConfig,
    }

    impl<'a> DangerousClientConfig<'a> {
        /// Overrides the default `ServerCertVerifier` with something else.
        pub fn set_certificate_verifier(&mut self, verifier: Arc<dyn ServerCertVerifier>) {
            self.cfg.verifier = verifier;
        }
    }
}

#[derive(Debug, PartialEq)]
enum EarlyDataState {
    Disabled,
    Ready,
    Accepted,
    AcceptedFinished,
    Rejected,
}

pub(super) struct EarlyData {
    state: EarlyDataState,
    left: usize,
}

impl EarlyData {
    fn new() -> Self {
        Self {
            left: 0,
            state: EarlyDataState::Disabled,
        }
    }

    pub(super) fn is_enabled(&self) -> bool {
        matches!(self.state, EarlyDataState::Ready | EarlyDataState::Accepted)
    }

    fn is_accepted(&self) -> bool {
        matches!(
            self.state,
            EarlyDataState::Accepted | EarlyDataState::AcceptedFinished
        )
    }

    pub(super) fn enable(&mut self, max_data: usize) {
        assert_eq!(self.state, EarlyDataState::Disabled);
        self.state = EarlyDataState::Ready;
        self.left = max_data;
    }

    pub(super) fn rejected(&mut self) {
        trace!("EarlyData rejected");
        self.state = EarlyDataState::Rejected;
    }

    pub(super) fn accepted(&mut self) {
        trace!("EarlyData accepted");
        assert_eq!(self.state, EarlyDataState::Ready);
        self.state = EarlyDataState::Accepted;
    }

    pub(super) fn finished(&mut self) {
        trace!("EarlyData finished");
        self.state = match self.state {
            EarlyDataState::Accepted => EarlyDataState::AcceptedFinished,
            _ => panic!("bad EarlyData state"),
        }
    }

    fn check_write(&mut self, sz: usize) -> io::Result<usize> {
        match self.state {
            EarlyDataState::Disabled => unreachable!(),
            EarlyDataState::Ready | EarlyDataState::Accepted => {
                let take = if self.left < sz {
                    mem::replace(&mut self.left, 0)
                } else {
                    self.left -= sz;
                    sz
                };

                Ok(take)
            }
            EarlyDataState::Rejected | EarlyDataState::AcceptedFinished => {
                Err(io::Error::from(io::ErrorKind::InvalidInput))
            }
        }
    }

    fn bytes_left(&self) -> usize {
        self.left
    }
}

/// Stub that implements io::Write and dispatches to `write_early_data`.
pub struct WriteEarlyData<'a> {
    sess: &'a mut ClientConnection,
}

impl<'a> WriteEarlyData<'a> {
    fn new(sess: &'a mut ClientConnection) -> WriteEarlyData<'a> {
        WriteEarlyData { sess }
    }

    /// How many bytes you may send.  Writes will become short
    /// once this reaches zero.
    pub fn bytes_left(&self) -> usize {
        self.sess
            .inner
            .data
            .early_data
            .bytes_left()
    }
}

impl<'a> io::Write for WriteEarlyData<'a> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.sess.write_early_data(buf)
    }

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

/// This represents a single TLS client connection.
pub struct ClientConnection {
    inner: ConnectionCommon<ClientConnectionData>,
}

impl fmt::Debug for ClientConnection {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("ClientConnection")
            .finish()
    }
}

impl ClientConnection {
    /// Make a new ClientConnection.  `config` controls how
    /// we behave in the TLS protocol, `name` is the
    /// name of the server we want to talk to.
    pub fn new(config: Arc<ClientConfig>, name: ServerName) -> Result<Self, Error> {
        Self::new_inner(config, name, Vec::new(), Protocol::Tcp)
    }

    fn new_inner(
        config: Arc<ClientConfig>,
        name: ServerName,
        extra_exts: Vec<ClientExtension>,
        proto: Protocol,
    ) -> Result<Self, Error> {
        let mut common_state = CommonState::new(Side::Client);
        common_state.set_max_fragment_size(config.max_fragment_size)?;
        common_state.protocol = proto;
        #[cfg(feature = "secret_extraction")]
        {
            common_state.enable_secret_extraction = config.enable_secret_extraction;
        }
        let mut data = ClientConnectionData::new();

        let mut cx = hs::ClientContext {
            common: &mut common_state,
            data: &mut data,
        };

        let state = hs::start_handshake(name, extra_exts, config, &mut cx)?;
        let inner = ConnectionCommon::new(state, data, common_state);

        Ok(Self { inner })
    }

    /// Returns an `io::Write` implementer you can write bytes to
    /// to send TLS1.3 early data (a.k.a. "0-RTT data") to the server.
    ///
    /// This returns None in many circumstances when the capability to
    /// send early data is not available, including but not limited to:
    ///
    /// - The server hasn't been talked to previously.
    /// - The server does not support resumption.
    /// - The server does not support early data.
    /// - The resumption data for the server has expired.
    ///
    /// The server specifies a maximum amount of early data.  You can
    /// learn this limit through the returned object, and writes through
    /// it will process only this many bytes.
    ///
    /// The server can choose not to accept any sent early data --
    /// in this case the data is lost but the connection continues.  You
    /// can tell this happened using `is_early_data_accepted`.
    pub fn early_data(&mut self) -> Option<WriteEarlyData> {
        if self.inner.data.early_data.is_enabled() {
            Some(WriteEarlyData::new(self))
        } else {
            None
        }
    }

    /// Returns True if the server signalled it will process early data.
    ///
    /// If you sent early data and this returns false at the end of the
    /// handshake then the server will not process the data.  This
    /// is not an error, but you may wish to resend the data.
    pub fn is_early_data_accepted(&self) -> bool {
        self.inner.data.early_data.is_accepted()
    }

    fn write_early_data(&mut self, data: &[u8]) -> io::Result<usize> {
        self.inner
            .data
            .early_data
            .check_write(data.len())
            .map(|sz| {
                self.inner
                    .common_state
                    .send_early_plaintext(&data[..sz])
            })
    }

    /// Extract secrets, so they can be used when configuring kTLS, for example.
    #[cfg(feature = "secret_extraction")]
    pub fn extract_secrets(self) -> Result<ExtractedSecrets, Error> {
        self.inner.extract_secrets()
    }
}

impl Deref for ClientConnection {
    type Target = ConnectionCommon<ClientConnectionData>;

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

impl DerefMut for ClientConnection {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.inner
    }
}

#[doc(hidden)]
impl<'a> TryFrom<&'a mut crate::Connection> for &'a mut ClientConnection {
    type Error = ();

    fn try_from(value: &'a mut crate::Connection) -> Result<Self, Self::Error> {
        use crate::Connection::*;
        match value {
            Client(conn) => Ok(conn),
            Server(_) => Err(()),
        }
    }
}

impl From<ClientConnection> for crate::Connection {
    fn from(conn: ClientConnection) -> Self {
        Self::Client(conn)
    }
}

/// State associated with a client connection.
pub struct ClientConnectionData {
    pub(super) early_data: EarlyData,
    pub(super) resumption_ciphersuite: Option<SupportedCipherSuite>,
}

impl ClientConnectionData {
    fn new() -> Self {
        Self {
            early_data: EarlyData::new(),
            resumption_ciphersuite: None,
        }
    }
}

impl crate::conn::SideData for ClientConnectionData {}

#[cfg(feature = "quic")]
impl quic::QuicExt for ClientConnection {
    fn quic_transport_parameters(&self) -> Option<&[u8]> {
        self.inner
            .common_state
            .quic
            .params
            .as_ref()
            .map(|v| v.as_ref())
    }

    fn zero_rtt_keys(&self) -> Option<quic::DirectionalKeys> {
        Some(quic::DirectionalKeys::new(
            self.inner
                .data
                .resumption_ciphersuite
                .and_then(|suite| suite.tls13())?,
            self.inner
                .common_state
                .quic
                .early_secret
                .as_ref()?,
        ))
    }

    fn read_hs(&mut self, plaintext: &[u8]) -> Result<(), Error> {
        self.inner.read_quic_hs(plaintext)
    }

    fn write_hs(&mut self, buf: &mut Vec<u8>) -> Option<quic::KeyChange> {
        quic::write_hs(&mut self.inner.common_state, buf)
    }

    fn alert(&self) -> Option<AlertDescription> {
        self.inner.common_state.quic.alert
    }
}

/// Methods specific to QUIC client sessions
#[cfg(feature = "quic")]
#[cfg_attr(docsrs, doc(cfg(feature = "quic")))]
pub trait ClientQuicExt {
    /// Make a new QUIC ClientConnection. This differs from `ClientConnection::new()`
    /// in that it takes an extra argument, `params`, which contains the
    /// TLS-encoded transport parameters to send.
    fn new_quic(
        config: Arc<ClientConfig>,
        quic_version: quic::Version,
        name: ServerName,
        params: Vec<u8>,
    ) -> Result<ClientConnection, Error> {
        if !config.supports_version(ProtocolVersion::TLSv1_3) {
            return Err(Error::General(
                "TLS 1.3 support is required for QUIC".into(),
            ));
        }

        let ext = match quic_version {
            quic::Version::V1Draft => ClientExtension::TransportParametersDraft(params),
            quic::Version::V1 => ClientExtension::TransportParameters(params),
        };

        ClientConnection::new_inner(config, name, vec![ext], Protocol::Quic)
    }
}

#[cfg(feature = "quic")]
impl ClientQuicExt for ClientConnection {}