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
764
765
766
767
768
769
770
771
772
773
774
775
776
use std::fmt;

use crate::anchors::{OwnedTrustAnchor, RootCertStore};
use crate::client::ServerName;
use crate::error::Error;
use crate::key::Certificate;
#[cfg(feature = "logging")]
use crate::log::{debug, trace, warn};
use crate::msgs::enums::SignatureScheme;
use crate::msgs::handshake::{DigitallySignedStruct, DistinguishedNames};

use ring::digest::Digest;

use std::convert::TryFrom;
use std::sync::Arc;
use std::time::SystemTime;

type SignatureAlgorithms = &'static [&'static webpki::SignatureAlgorithm];

/// Which signature verification mechanisms we support.  No particular
/// order.
static SUPPORTED_SIG_ALGS: SignatureAlgorithms = &[
    &webpki::ECDSA_P256_SHA256,
    &webpki::ECDSA_P256_SHA384,
    &webpki::ECDSA_P384_SHA256,
    &webpki::ECDSA_P384_SHA384,
    &webpki::ED25519,
    &webpki::RSA_PSS_2048_8192_SHA256_LEGACY_KEY,
    &webpki::RSA_PSS_2048_8192_SHA384_LEGACY_KEY,
    &webpki::RSA_PSS_2048_8192_SHA512_LEGACY_KEY,
    &webpki::RSA_PKCS1_2048_8192_SHA256,
    &webpki::RSA_PKCS1_2048_8192_SHA384,
    &webpki::RSA_PKCS1_2048_8192_SHA512,
    &webpki::RSA_PKCS1_3072_8192_SHA384,
];

// Marker types.  These are used to bind the fact some verification
// (certificate chain or handshake signature) has taken place into
// protocol states.  We use this to have the compiler check that there
// are no 'goto fail'-style elisions of important checks before we
// reach the traffic stage.
//
// These types are public, but cannot be directly constructed.  This
// means their origins can be precisely determined by looking
// for their `assertion` constructors.

/// Zero-sized marker type representing verification of a signature.
#[derive(Debug)]
pub struct HandshakeSignatureValid(());

impl HandshakeSignatureValid {
    /// Make a `HandshakeSignatureValid`
    pub fn assertion() -> Self {
        Self(())
    }
}

#[derive(Debug)]
pub(crate) struct FinishedMessageVerified(());

impl FinishedMessageVerified {
    pub(crate) fn assertion() -> Self {
        Self(())
    }
}

/// Zero-sized marker type representing verification of a server cert chain.
#[allow(unreachable_pub)]
#[derive(Debug)]
pub struct ServerCertVerified(());

#[allow(unreachable_pub)]
impl ServerCertVerified {
    /// Make a `ServerCertVerified`
    pub fn assertion() -> Self {
        Self(())
    }
}

/// Zero-sized marker type representing verification of a client cert chain.
#[derive(Debug)]
pub struct ClientCertVerified(());

impl ClientCertVerified {
    /// Make a `ClientCertVerified`
    pub fn assertion() -> Self {
        Self(())
    }
}

/// Something that can verify a server certificate chain, and verify
/// signatures made by certificates.
#[allow(unreachable_pub)]
pub trait ServerCertVerifier: Send + Sync {
    /// Verify the end-entity certificate `end_entity` is valid for the
    /// hostname `dns_name` and chains to at least one trust anchor.
    ///
    /// `intermediates` contains the intermediate certificates the client sent
    /// along with the end-entity certificate; it is in the same order that the
    /// peer sent them and may be empty.
    ///
    /// `scts` contains the Signed Certificate Timestamps (SCTs) the server
    /// sent with the certificate, if any.
    fn verify_server_cert(
        &self,
        end_entity: &Certificate,
        intermediates: &[Certificate],
        server_name: &ServerName,
        scts: &mut dyn Iterator<Item = &[u8]>,
        ocsp_response: &[u8],
        now: SystemTime,
    ) -> Result<ServerCertVerified, Error>;

    /// Verify a signature allegedly by the given server certificate.
    ///
    /// `message` is not hashed, and needs hashing during the verification.
    /// The signature and algorithm are within `dss`.  `cert` contains the
    /// public key to use.
    ///
    /// `cert` is the same certificate that was previously validated by a
    /// call to `verify_server_cert`.
    ///
    /// If and only if the signature is valid, return HandshakeSignatureValid.
    /// Otherwise, return an error -- rustls will send an alert and abort the
    /// connection.
    ///
    /// This method is only called for TLS1.2 handshakes.  Note that, in TLS1.2,
    /// SignatureSchemes such as `SignatureScheme::ECDSA_NISTP256_SHA256` are not
    /// in fact bound to the specific curve implied in their name.
    ///
    /// This trait method has a default implementation that uses webpki to verify
    /// the signature.
    fn verify_tls12_signature(
        &self,
        message: &[u8],
        cert: &Certificate,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_signed_struct(message, cert, dss)
    }

    /// Verify a signature allegedly by the given server certificate.
    ///
    /// This method is only called for TLS1.3 handshakes.
    ///
    /// This method is very similar to `verify_tls12_signature`: but note the
    /// tighter ECDSA SignatureScheme semantics -- e.g. `SignatureScheme::ECDSA_NISTP256_SHA256`
    /// must only validate signatures using public keys on the right curve --
    /// rustls does not enforce this requirement for you.
    ///
    /// This trait method has a default implementation that uses webpki to verify
    /// the signature.
    fn verify_tls13_signature(
        &self,
        message: &[u8],
        cert: &Certificate,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_tls13(message, cert, dss)
    }

    /// Return the list of SignatureSchemes that this verifier will handle,
    /// in `verify_tls12_signature` and `verify_tls13_signature` calls.
    ///
    /// This should be in priority order, with the most preferred first.
    ///
    /// This trait method has a default implementation that reflects the schemes
    /// supported by webpki.
    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
        WebPkiVerifier::verification_schemes()
    }

    /// Returns `true` if Rustls should ask the server to send SCTs.
    ///
    /// Signed Certificate Timestamps (SCTs) are used for Certificate
    /// Transparency validation.
    ///
    /// The default implementation of this function returns true.
    fn request_scts(&self) -> bool {
        true
    }
}

impl fmt::Debug for dyn ServerCertVerifier {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "dyn ServerCertVerifier")
    }
}

/// A type which encapsulates a string that is a syntactically valid DNS name.
#[derive(Clone, Debug, PartialEq)]
pub struct DnsName(pub(crate) webpki::DnsName);

impl AsRef<str> for DnsName {
    fn as_ref(&self) -> &str {
        AsRef::<str>::as_ref(&self.0)
    }
}

/// Something that can verify a client certificate chain
#[allow(unreachable_pub)]
pub trait ClientCertVerifier: Send + Sync {
    /// Returns `true` to enable the server to request a client certificate and
    /// `false` to skip requesting a client certificate. Defaults to `true`.
    fn offer_client_auth(&self) -> bool {
        true
    }

    /// Return `Some(true)` to require a client certificate and `Some(false)` to make
    /// client authentication optional. Return `None` to abort the connection.
    /// Defaults to `Some(self.offer_client_auth())`.
    fn client_auth_mandatory(&self) -> Option<bool> {
        Some(self.offer_client_auth())
    }

    /// Returns the subject names of the client authentication trust anchors to
    /// share with the client when requesting client authentication.
    ///
    /// Return `None` to abort the connection. Return an empty `Vec` to continue
    /// the handshake without passing a list of CA DNs.
    fn client_auth_root_subjects(&self) -> Option<DistinguishedNames>;

    /// Verify the end-entity certificate `end_entity` is valid for the
    /// and chains to at least one of the trust anchors in `roots`.
    ///
    /// `intermediates` contains the intermediate certificates the
    /// client sent along with the end-entity certificate; it is in the same
    /// order that the peer sent them and may be empty.
    fn verify_client_cert(
        &self,
        end_entity: &Certificate,
        intermediates: &[Certificate],
        now: SystemTime,
    ) -> Result<ClientCertVerified, Error>;

    /// Verify a signature allegedly by the given server certificate.
    ///
    /// `message` is not hashed, and needs hashing during the verification.
    /// The signature and algorithm are within `dss`.  `cert` contains the
    /// public key to use.
    ///
    /// `cert` is the same certificate that was previously validated by a
    /// call to `verify_server_cert`.
    ///
    /// If and only if the signature is valid, return HandshakeSignatureValid.
    /// Otherwise, return an error -- rustls will send an alert and abort the
    /// connection.
    ///
    /// This method is only called for TLS1.2 handshakes.  Note that, in TLS1.2,
    /// SignatureSchemes such as `SignatureScheme::ECDSA_NISTP256_SHA256` are not
    /// in fact bound to the specific curve implied in their name.
    ///
    /// This trait method has a default implementation that uses webpki to verify
    /// the signature.
    fn verify_tls12_signature(
        &self,
        message: &[u8],
        cert: &Certificate,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_signed_struct(message, cert, dss)
    }

    /// Verify a signature allegedly by the given server certificate.
    ///
    /// This method is only called for TLS1.3 handshakes.
    ///
    /// This method is very similar to `verify_tls12_signature`: but note the
    /// tighter ECDSA SignatureScheme semantics -- e.g. `SignatureScheme::ECDSA_NISTP256_SHA256`
    /// must only validate signatures using public keys on the right curve --
    /// rustls does not enforce this requirement for you.
    ///
    /// This trait method has a default implementation that uses webpki to verify
    /// the signature.
    fn verify_tls13_signature(
        &self,
        message: &[u8],
        cert: &Certificate,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_tls13(message, cert, dss)
    }

    /// Return the list of SignatureSchemes that this verifier will handle,
    /// in `verify_tls12_signature` and `verify_tls13_signature` calls.
    ///
    /// This should be in priority order, with the most preferred first.
    ///
    /// This trait method has a default implementation that reflects the schemes
    /// supported by webpki.
    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
        WebPkiVerifier::verification_schemes()
    }
}

impl fmt::Debug for dyn ClientCertVerifier {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "dyn ClientCertVerifier")
    }
}

impl ServerCertVerifier for WebPkiVerifier {
    /// Will verify the certificate is valid in the following ways:
    /// - Signed by a  trusted `RootCertStore` CA
    /// - Not Expired
    /// - Valid for DNS entry
    fn verify_server_cert(
        &self,
        end_entity: &Certificate,
        intermediates: &[Certificate],
        server_name: &ServerName,
        scts: &mut dyn Iterator<Item = &[u8]>,
        ocsp_response: &[u8],
        now: SystemTime,
    ) -> Result<ServerCertVerified, Error> {
        let (cert, chain, trustroots) = prepare(end_entity, intermediates, &self.roots)?;
        let webpki_now = webpki::Time::try_from(now).map_err(|_| Error::FailedToGetCurrentTime)?;

        let dns_name = match server_name {
            ServerName::DnsName(dns_name) => dns_name,
            ServerName::IpAddress(_) => {
                return Err(Error::UnsupportedNameType);
            }
        };

        let cert = cert
            .verify_is_valid_tls_server_cert(
                SUPPORTED_SIG_ALGS,
                &webpki::TlsServerTrustAnchors(&trustroots),
                &chain,
                webpki_now,
            )
            .map_err(pki_error)
            .map(|_| cert)?;

        if let Some(policy) = &self.ct_policy {
            policy.verify(end_entity, now, scts)?;
        }

        if !ocsp_response.is_empty() {
            trace!("Unvalidated OCSP response: {:?}", ocsp_response.to_vec());
        }

        cert.verify_is_valid_for_dns_name(dns_name.0.as_ref())
            .map_err(pki_error)
            .map(|_| ServerCertVerified::assertion())
    }
}

/// Default `ServerCertVerifier`, see the trait impl for more information.
#[allow(unreachable_pub)]
pub struct WebPkiVerifier {
    roots: RootCertStore,
    ct_policy: Option<CertificateTransparencyPolicy>,
}

#[allow(unreachable_pub)]
impl WebPkiVerifier {
    /// Constructs a new `WebPkiVerifier`.
    ///
    /// `roots` is the set of trust anchors to trust for issuing server certs.
    ///
    /// `ct_logs` is the list of logs that are trusted for Certificate
    /// Transparency. Currently CT log enforcement is opportunistic; see
    /// <https://github.com/rustls/rustls/issues/479>.
    pub fn new(roots: RootCertStore, ct_policy: Option<CertificateTransparencyPolicy>) -> Self {
        Self { roots, ct_policy }
    }

    /// Returns the signature verification methods supported by
    /// webpki.
    pub fn verification_schemes() -> Vec<SignatureScheme> {
        vec![
            SignatureScheme::ECDSA_NISTP384_SHA384,
            SignatureScheme::ECDSA_NISTP256_SHA256,
            SignatureScheme::ED25519,
            SignatureScheme::RSA_PSS_SHA512,
            SignatureScheme::RSA_PSS_SHA384,
            SignatureScheme::RSA_PSS_SHA256,
            SignatureScheme::RSA_PKCS1_SHA512,
            SignatureScheme::RSA_PKCS1_SHA384,
            SignatureScheme::RSA_PKCS1_SHA256,
        ]
    }
}

/// Policy for enforcing Certificate Transparency.
///
/// Because Certificate Transparency logs are sharded on a per-year basis and can be trusted or
/// distrusted relatively quickly, rustls stores a validation deadline. Server certificates will
/// be validated against the configured CT logs until the deadline expires. After the deadline,
/// certificates will no longer be validated, and a warning message will be logged. The deadline
/// may vary depending on how often you deploy builds with updated dependencies.
#[allow(unreachable_pub)]
pub struct CertificateTransparencyPolicy {
    logs: &'static [&'static sct::Log<'static>],
    validation_deadline: SystemTime,
}

impl CertificateTransparencyPolicy {
    /// Create a new policy.
    #[allow(unreachable_pub)]
    pub fn new(
        logs: &'static [&'static sct::Log<'static>],
        validation_deadline: SystemTime,
    ) -> Self {
        Self {
            logs,
            validation_deadline,
        }
    }

    fn verify(
        &self,
        cert: &Certificate,
        now: SystemTime,
        scts: &mut dyn Iterator<Item = &[u8]>,
    ) -> Result<(), Error> {
        if self.logs.is_empty() {
            return Ok(());
        } else if self
            .validation_deadline
            .duration_since(now)
            .is_err()
        {
            warn!("certificate transparency logs have expired, validation disabled");
            return Ok(());
        }

        let now = unix_time_millis(now)?;
        let mut last_sct_error = None;
        for sct in scts {
            #[cfg_attr(not(feature = "logging"), allow(unused_variables))]
            match sct::verify_sct(&cert.0, sct, now, self.logs) {
                Ok(index) => {
                    debug!(
                        "Valid SCT signed by {} on {}",
                        self.logs[index].operated_by, self.logs[index].description
                    );
                    return Ok(());
                }
                Err(e) => {
                    if e.should_be_fatal() {
                        return Err(Error::InvalidSct(e));
                    }
                    debug!("SCT ignored because {:?}", e);
                    last_sct_error = Some(e);
                }
            }
        }

        /* If we were supplied with some logs, and some SCTs,
         * but couldn't verify any of them, fail the handshake. */
        if let Some(last_sct_error) = last_sct_error {
            warn!("No valid SCTs provided");
            return Err(Error::InvalidSct(last_sct_error));
        }

        Ok(())
    }
}

type CertChainAndRoots<'a, 'b> = (
    webpki::EndEntityCert<'a>,
    Vec<&'a [u8]>,
    Vec<webpki::TrustAnchor<'b>>,
);

fn prepare<'a, 'b>(
    end_entity: &'a Certificate,
    intermediates: &'a [Certificate],
    roots: &'b RootCertStore,
) -> Result<CertChainAndRoots<'a, 'b>, Error> {
    // EE cert must appear first.
    let cert = webpki::EndEntityCert::try_from(end_entity.0.as_ref()).map_err(pki_error)?;

    let intermediates: Vec<&'a [u8]> = intermediates
        .iter()
        .map(|cert| cert.0.as_ref())
        .collect();

    let trustroots: Vec<webpki::TrustAnchor> = roots
        .roots
        .iter()
        .map(OwnedTrustAnchor::to_trust_anchor)
        .collect();

    Ok((cert, intermediates, trustroots))
}

/// A `ClientCertVerifier` that will ensure that every client provides a trusted
/// certificate, without any name checking.
pub struct AllowAnyAuthenticatedClient {
    roots: RootCertStore,
}

impl AllowAnyAuthenticatedClient {
    /// Construct a new `AllowAnyAuthenticatedClient`.
    ///
    /// `roots` is the list of trust anchors to use for certificate validation.
    pub fn new(roots: RootCertStore) -> Arc<dyn ClientCertVerifier> {
        Arc::new(Self { roots })
    }
}

impl ClientCertVerifier for AllowAnyAuthenticatedClient {
    fn offer_client_auth(&self) -> bool {
        true
    }

    fn client_auth_root_subjects(&self) -> Option<DistinguishedNames> {
        Some(self.roots.subjects())
    }

    fn verify_client_cert(
        &self,
        end_entity: &Certificate,
        intermediates: &[Certificate],
        now: SystemTime,
    ) -> Result<ClientCertVerified, Error> {
        let (cert, chain, trustroots) = prepare(end_entity, intermediates, &self.roots)?;
        let now = webpki::Time::try_from(now).map_err(|_| Error::FailedToGetCurrentTime)?;
        cert.verify_is_valid_tls_client_cert(
            SUPPORTED_SIG_ALGS,
            &webpki::TlsClientTrustAnchors(&trustroots),
            &chain,
            now,
        )
        .map_err(pki_error)
        .map(|_| ClientCertVerified::assertion())
    }
}

/// A `ClientCertVerifier` that will allow both anonymous and authenticated
/// clients, without any name checking.
///
/// Client authentication will be requested during the TLS handshake. If the
/// client offers a certificate then this acts like
/// `AllowAnyAuthenticatedClient`, otherwise this acts like `NoClientAuth`.
pub struct AllowAnyAnonymousOrAuthenticatedClient {
    inner: AllowAnyAuthenticatedClient,
}

impl AllowAnyAnonymousOrAuthenticatedClient {
    /// Construct a new `AllowAnyAnonymousOrAuthenticatedClient`.
    ///
    /// `roots` is the list of trust anchors to use for certificate validation.
    pub fn new(roots: RootCertStore) -> Arc<dyn ClientCertVerifier> {
        Arc::new(Self {
            inner: AllowAnyAuthenticatedClient { roots },
        })
    }
}

impl ClientCertVerifier for AllowAnyAnonymousOrAuthenticatedClient {
    fn offer_client_auth(&self) -> bool {
        self.inner.offer_client_auth()
    }

    fn client_auth_mandatory(&self) -> Option<bool> {
        Some(false)
    }

    fn client_auth_root_subjects(&self) -> Option<DistinguishedNames> {
        self.inner.client_auth_root_subjects()
    }

    fn verify_client_cert(
        &self,
        end_entity: &Certificate,
        intermediates: &[Certificate],
        now: SystemTime,
    ) -> Result<ClientCertVerified, Error> {
        self.inner
            .verify_client_cert(end_entity, intermediates, now)
    }
}

fn pki_error(error: webpki::Error) -> Error {
    use webpki::Error::*;
    match error {
        BadDer | BadDerTime => Error::InvalidCertificateEncoding,
        InvalidSignatureForPublicKey => Error::InvalidCertificateSignature,
        UnsupportedSignatureAlgorithm | UnsupportedSignatureAlgorithmForPublicKey => {
            Error::InvalidCertificateSignatureType
        }
        e => Error::InvalidCertificateData(format!("invalid peer certificate: {}", e)),
    }
}

/// Turns off client authentication.
pub struct NoClientAuth;

impl NoClientAuth {
    /// Constructs a `NoClientAuth` and wraps it in an `Arc`.
    pub fn new() -> Arc<dyn ClientCertVerifier> {
        Arc::new(NoClientAuth)
    }
}

impl ClientCertVerifier for NoClientAuth {
    fn offer_client_auth(&self) -> bool {
        false
    }

    fn client_auth_root_subjects(&self) -> Option<DistinguishedNames> {
        unimplemented!();
    }

    fn verify_client_cert(
        &self,
        _end_entity: &Certificate,
        _intermediates: &[Certificate],
        _now: SystemTime,
    ) -> Result<ClientCertVerified, Error> {
        unimplemented!();
    }
}

static ECDSA_SHA256: SignatureAlgorithms =
    &[&webpki::ECDSA_P256_SHA256, &webpki::ECDSA_P384_SHA256];

static ECDSA_SHA384: SignatureAlgorithms =
    &[&webpki::ECDSA_P256_SHA384, &webpki::ECDSA_P384_SHA384];

static ED25519: SignatureAlgorithms = &[&webpki::ED25519];

static RSA_SHA256: SignatureAlgorithms = &[&webpki::RSA_PKCS1_2048_8192_SHA256];
static RSA_SHA384: SignatureAlgorithms = &[&webpki::RSA_PKCS1_2048_8192_SHA384];
static RSA_SHA512: SignatureAlgorithms = &[&webpki::RSA_PKCS1_2048_8192_SHA512];
static RSA_PSS_SHA256: SignatureAlgorithms = &[&webpki::RSA_PSS_2048_8192_SHA256_LEGACY_KEY];
static RSA_PSS_SHA384: SignatureAlgorithms = &[&webpki::RSA_PSS_2048_8192_SHA384_LEGACY_KEY];
static RSA_PSS_SHA512: SignatureAlgorithms = &[&webpki::RSA_PSS_2048_8192_SHA512_LEGACY_KEY];

fn convert_scheme(scheme: SignatureScheme) -> Result<SignatureAlgorithms, Error> {
    match scheme {
        // nb. for TLS1.2 the curve is not fixed by SignatureScheme.
        SignatureScheme::ECDSA_NISTP256_SHA256 => Ok(ECDSA_SHA256),
        SignatureScheme::ECDSA_NISTP384_SHA384 => Ok(ECDSA_SHA384),

        SignatureScheme::ED25519 => Ok(ED25519),

        SignatureScheme::RSA_PKCS1_SHA256 => Ok(RSA_SHA256),
        SignatureScheme::RSA_PKCS1_SHA384 => Ok(RSA_SHA384),
        SignatureScheme::RSA_PKCS1_SHA512 => Ok(RSA_SHA512),

        SignatureScheme::RSA_PSS_SHA256 => Ok(RSA_PSS_SHA256),
        SignatureScheme::RSA_PSS_SHA384 => Ok(RSA_PSS_SHA384),
        SignatureScheme::RSA_PSS_SHA512 => Ok(RSA_PSS_SHA512),

        _ => {
            let error_msg = format!("received unadvertised sig scheme {:?}", scheme);
            Err(Error::PeerMisbehavedError(error_msg))
        }
    }
}

fn verify_sig_using_any_alg(
    cert: &webpki::EndEntityCert,
    algs: SignatureAlgorithms,
    message: &[u8],
    sig: &[u8],
) -> Result<(), webpki::Error> {
    // TLS doesn't itself give us enough info to map to a single webpki::SignatureAlgorithm.
    // Therefore, convert_algs maps to several and we try them all.
    for alg in algs {
        match cert.verify_signature(alg, message, sig) {
            Err(webpki::Error::UnsupportedSignatureAlgorithmForPublicKey) => continue,
            res => return res,
        }
    }

    Err(webpki::Error::UnsupportedSignatureAlgorithmForPublicKey)
}

fn verify_signed_struct(
    message: &[u8],
    cert: &Certificate,
    dss: &DigitallySignedStruct,
) -> Result<HandshakeSignatureValid, Error> {
    let possible_algs = convert_scheme(dss.scheme)?;
    let cert = webpki::EndEntityCert::try_from(cert.0.as_ref()).map_err(pki_error)?;

    verify_sig_using_any_alg(&cert, possible_algs, message, &dss.sig.0)
        .map_err(pki_error)
        .map(|_| HandshakeSignatureValid::assertion())
}

fn convert_alg_tls13(
    scheme: SignatureScheme,
) -> Result<&'static webpki::SignatureAlgorithm, Error> {
    use crate::msgs::enums::SignatureScheme::*;

    match scheme {
        ECDSA_NISTP256_SHA256 => Ok(&webpki::ECDSA_P256_SHA256),
        ECDSA_NISTP384_SHA384 => Ok(&webpki::ECDSA_P384_SHA384),
        ED25519 => Ok(&webpki::ED25519),
        RSA_PSS_SHA256 => Ok(&webpki::RSA_PSS_2048_8192_SHA256_LEGACY_KEY),
        RSA_PSS_SHA384 => Ok(&webpki::RSA_PSS_2048_8192_SHA384_LEGACY_KEY),
        RSA_PSS_SHA512 => Ok(&webpki::RSA_PSS_2048_8192_SHA512_LEGACY_KEY),
        _ => {
            let error_msg = format!("received unsupported sig scheme {:?}", scheme);
            Err(Error::PeerMisbehavedError(error_msg))
        }
    }
}

/// Constructs the signature message specified in section 4.4.3 of RFC8446.
pub(crate) fn construct_tls13_client_verify_message(handshake_hash: &Digest) -> Vec<u8> {
    construct_tls13_verify_message(handshake_hash, b"TLS 1.3, client CertificateVerify\x00")
}

/// Constructs the signature message specified in section 4.4.3 of RFC8446.
pub(crate) fn construct_tls13_server_verify_message(handshake_hash: &Digest) -> Vec<u8> {
    construct_tls13_verify_message(handshake_hash, b"TLS 1.3, server CertificateVerify\x00")
}

fn construct_tls13_verify_message(
    handshake_hash: &Digest,
    context_string_with_0: &[u8],
) -> Vec<u8> {
    let mut msg = Vec::new();
    msg.resize(64, 0x20u8);
    msg.extend_from_slice(context_string_with_0);
    msg.extend_from_slice(handshake_hash.as_ref());
    msg
}

fn verify_tls13(
    msg: &[u8],
    cert: &Certificate,
    dss: &DigitallySignedStruct,
) -> Result<HandshakeSignatureValid, Error> {
    let alg = convert_alg_tls13(dss.scheme)?;

    let cert = webpki::EndEntityCert::try_from(cert.0.as_ref()).map_err(pki_error)?;

    cert.verify_signature(alg, msg, &dss.sig.0)
        .map_err(pki_error)
        .map(|_| HandshakeSignatureValid::assertion())
}

fn unix_time_millis(now: SystemTime) -> Result<u64, Error> {
    now.duration_since(std::time::UNIX_EPOCH)
        .map(|dur| dur.as_secs())
        .map_err(|_| Error::FailedToGetCurrentTime)
        .and_then(|secs| {
            secs.checked_mul(1000)
                .ok_or(Error::FailedToGetCurrentTime)
        })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn assertions_are_debug() {
        assert_eq!(
            format!("{:?}", ClientCertVerified::assertion()),
            "ClientCertVerified(())"
        );
        assert_eq!(
            format!("{:?}", HandshakeSignatureValid::assertion()),
            "HandshakeSignatureValid(())"
        );
        assert_eq!(
            format!("{:?}", FinishedMessageVerified::assertion()),
            "FinishedMessageVerified(())"
        );
        assert_eq!(
            format!("{:?}", ServerCertVerified::assertion()),
            "ServerCertVerified(())"
        );
    }
}