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 alloc::sync::Arc;
use alloc::vec::Vec;

use pki_types::{CertificateDer, CertificateRevocationListDer, UnixTime};
use webpki::{CertRevocationList, ExpirationPolicy, RevocationCheckDepth, UnknownStatusPolicy};

use super::{pki_error, VerifierBuilderError};
#[cfg(doc)]
use crate::crypto;
use crate::crypto::{CryptoProvider, WebPkiSupportedAlgorithms};
#[cfg(doc)]
use crate::server::ServerConfig;
use crate::verify::{
    ClientCertVerified, ClientCertVerifier, DigitallySignedStruct, HandshakeSignatureValid,
    NoClientAuth,
};
use crate::webpki::parse_crls;
use crate::webpki::verify::{verify_tls12_signature, verify_tls13_signature, ParsedCertificate};
#[cfg(doc)]
use crate::ConfigBuilder;
use crate::{DistinguishedName, Error, RootCertStore, SignatureScheme};

/// A builder for configuring a `webpki` client certificate verifier.
///
/// For more information, see the [`WebPkiClientVerifier`] documentation.
#[derive(Debug, Clone)]
pub struct ClientCertVerifierBuilder {
    roots: Arc<RootCertStore>,
    root_hint_subjects: Vec<DistinguishedName>,
    crls: Vec<CertificateRevocationListDer<'static>>,
    revocation_check_depth: RevocationCheckDepth,
    unknown_revocation_policy: UnknownStatusPolicy,
    revocation_expiration_policy: ExpirationPolicy,
    anon_policy: AnonymousClientPolicy,
    supported_algs: WebPkiSupportedAlgorithms,
}

impl ClientCertVerifierBuilder {
    pub(crate) fn new(
        roots: Arc<RootCertStore>,
        supported_algs: WebPkiSupportedAlgorithms,
    ) -> Self {
        Self {
            root_hint_subjects: roots.subjects(),
            roots,
            crls: Vec::new(),
            anon_policy: AnonymousClientPolicy::Deny,
            revocation_check_depth: RevocationCheckDepth::Chain,
            unknown_revocation_policy: UnknownStatusPolicy::Deny,
            revocation_expiration_policy: ExpirationPolicy::Ignore,
            supported_algs,
        }
    }

    /// Clear the list of trust anchor hint subjects.
    ///
    /// By default, the client cert verifier will use the subjects provided by the root cert
    /// store configured for client authentication. Calling this function will remove these
    /// hint subjects, indicating the client should make a free choice of which certificate
    /// to send.
    ///
    /// See [`ClientCertVerifier::root_hint_subjects`] for more information on
    /// circumstances where you may want to clear the default hint subjects.
    pub fn clear_root_hint_subjects(mut self) -> Self {
        self.root_hint_subjects = Vec::default();
        self
    }

    /// Add additional [`DistinguishedName`]s to the list of trust anchor hint subjects.
    ///
    /// By default, the client cert verifier will use the subjects provided by the root cert
    /// store configured for client authentication. Calling this function will add to these
    /// existing hint subjects. Calling this function with empty `subjects` will have no
    /// effect.
    ///
    /// See [`ClientCertVerifier::root_hint_subjects`] for more information on
    /// circumstances where you may want to override the default hint subjects.
    pub fn add_root_hint_subjects(
        mut self,
        subjects: impl IntoIterator<Item = DistinguishedName>,
    ) -> Self {
        self.root_hint_subjects.extend(subjects);
        self
    }

    /// Verify the revocation state of presented client certificates against the provided
    /// certificate revocation lists (CRLs). Calling `with_crls` multiple times appends the
    /// given CRLs to the existing collection.
    ///
    /// By default all certificates in the verified chain built from the presented client
    /// certificate to a trust anchor will have their revocation status checked. Calling
    /// [`only_check_end_entity_revocation`][Self::only_check_end_entity_revocation] will
    /// change this behavior to only check the end entity client certificate.
    ///
    /// By default if a certificate's revocation status can not be determined using the
    /// configured CRLs, it will be treated as an error. Calling
    /// [`allow_unknown_revocation_status`][Self::allow_unknown_revocation_status] will change
    /// this behavior to allow unknown revocation status.
    pub fn with_crls(
        mut self,
        crls: impl IntoIterator<Item = CertificateRevocationListDer<'static>>,
    ) -> Self {
        self.crls.extend(crls);
        self
    }

    /// Only check the end entity certificate revocation status when using CRLs.
    ///
    /// If CRLs are provided using [`with_crls`][Self::with_crls] only check the end entity
    /// certificate's revocation status. Overrides the default behavior of checking revocation
    /// status for each certificate in the verified chain built to a trust anchor
    /// (excluding the trust anchor itself).
    ///
    /// If no CRLs are provided then this setting has no effect. Neither the end entity certificate
    /// or any intermediates will have revocation status checked.
    pub fn only_check_end_entity_revocation(mut self) -> Self {
        self.revocation_check_depth = RevocationCheckDepth::EndEntity;
        self
    }

    /// Allow unauthenticated clients to connect.
    ///
    /// Clients that offer a client certificate issued by a trusted root, and clients that offer no
    /// client certificate will be allowed to connect.
    pub fn allow_unauthenticated(mut self) -> Self {
        self.anon_policy = AnonymousClientPolicy::Allow;
        self
    }

    /// Allow unknown certificate revocation status when using CRLs.
    ///
    /// If CRLs are provided with [`with_crls`][Self::with_crls] and it isn't possible to
    /// determine the revocation status of a certificate, do not treat it as an error condition.
    /// Overrides the default behavior where unknown revocation status is considered an error.
    ///
    /// If no CRLs are provided then this setting has no effect as revocation status checks
    /// are not performed.
    pub fn allow_unknown_revocation_status(mut self) -> Self {
        self.unknown_revocation_policy = UnknownStatusPolicy::Allow;
        self
    }

    /// Enforce the CRL nextUpdate field (i.e. expiration)
    ///
    /// If CRLs are provided with [`with_crls`][Self::with_crls] and the verification time is
    /// beyond the time in the CRL nextUpdate field, it is expired and treated as an error condition.
    /// Overrides the default behavior where expired CRLs are not treated as an error condition.
    ///
    /// If no CRLs are provided then this setting has no effect as revocation status checks
    /// are not performed.
    pub fn enforce_revocation_expiration(mut self) -> Self {
        self.revocation_expiration_policy = ExpirationPolicy::Enforce;
        self
    }

    /// Build a client certificate verifier. The built verifier will be used for the server to offer
    /// client certificate authentication, to control how offered client certificates are validated,
    /// and to determine what to do with anonymous clients that do not respond to the client
    /// certificate authentication offer with a client certificate.
    ///
    /// If `with_signature_verification_algorithms` was not called on the builder, a default set of
    /// signature verification algorithms is used, controlled by the selected [`CryptoProvider`].
    ///
    /// Once built, the provided `Arc<dyn ClientCertVerifier>` can be used with a Rustls
    /// [`ServerConfig`] to configure client certificate validation using
    /// [`with_client_cert_verifier`][ConfigBuilder<ClientConfig, WantsVerifier>::with_client_cert_verifier].
    ///
    /// # Errors
    /// This function will return a [`VerifierBuilderError`] if:
    /// 1. No trust anchors have been provided.
    /// 2. DER encoded CRLs have been provided that can not be parsed successfully.
    pub fn build(self) -> Result<Arc<dyn ClientCertVerifier>, VerifierBuilderError> {
        if self.roots.is_empty() {
            return Err(VerifierBuilderError::NoRootAnchors);
        }

        Ok(Arc::new(WebPkiClientVerifier::new(
            self.roots,
            self.root_hint_subjects,
            parse_crls(self.crls)?,
            self.revocation_check_depth,
            self.unknown_revocation_policy,
            self.revocation_expiration_policy,
            self.anon_policy,
            self.supported_algs,
        )))
    }
}

/// A client certificate verifier that uses the `webpki` crate[^1] to perform client certificate
/// validation.
///
/// It must be created via the [`WebPkiClientVerifier::builder()`] or
/// [`WebPkiClientVerifier::builder_with_provider()`] functions.
///
/// Once built, the provided `Arc<dyn ClientCertVerifier>` can be used with a Rustls [`ServerConfig`]
/// to configure client certificate validation using [`with_client_cert_verifier`][ConfigBuilder<ClientConfig, WantsVerifier>::with_client_cert_verifier].
///
/// Example:
///
/// To require all clients present a client certificate issued by a trusted CA:
/// ```no_run
/// # #[cfg(any(feature = "ring", feature = "aws_lc_rs"))] {
/// # use rustls::RootCertStore;
/// # use rustls::server::WebPkiClientVerifier;
/// # let roots = RootCertStore::empty();
/// let client_verifier = WebPkiClientVerifier::builder(roots.into())
///   .build()
///   .unwrap();
/// # }
/// ```
///
/// Or, to allow clients presenting a client certificate authenticated by a trusted CA, or
/// anonymous clients that present no client certificate:
/// ```no_run
/// # #[cfg(any(feature = "ring", feature = "aws_lc_rs"))] {
/// # use rustls::RootCertStore;
/// # use rustls::server::WebPkiClientVerifier;
/// # let roots = RootCertStore::empty();
/// let client_verifier = WebPkiClientVerifier::builder(roots.into())
///   .allow_unauthenticated()
///   .build()
///   .unwrap();
/// # }
/// ```
///
/// If you wish to disable advertising client authentication:
/// ```no_run
/// # use rustls::RootCertStore;
/// # use rustls::server::WebPkiClientVerifier;
/// # let roots = RootCertStore::empty();
/// let client_verifier = WebPkiClientVerifier::no_client_auth();
/// ```
///
/// You can also configure the client verifier to check for certificate revocation with
/// client certificate revocation lists (CRLs):
/// ```no_run
/// # #[cfg(any(feature = "ring", feature = "aws_lc_rs"))] {
/// # use rustls::RootCertStore;
/// # use rustls::server::{WebPkiClientVerifier};
/// # let roots = RootCertStore::empty();
/// # let crls = Vec::new();
/// let client_verifier = WebPkiClientVerifier::builder(roots.into())
///   .with_crls(crls)
///   .build()
///   .unwrap();
/// # }
/// ```
///
/// [^1]: <https://github.com/rustls/webpki>
#[derive(Debug)]
pub struct WebPkiClientVerifier {
    roots: Arc<RootCertStore>,
    root_hint_subjects: Vec<DistinguishedName>,
    crls: Vec<CertRevocationList<'static>>,
    revocation_check_depth: RevocationCheckDepth,
    unknown_revocation_policy: UnknownStatusPolicy,
    revocation_expiration_policy: ExpirationPolicy,
    anonymous_policy: AnonymousClientPolicy,
    supported_algs: WebPkiSupportedAlgorithms,
}

impl WebPkiClientVerifier {
    /// Create a builder for the `webpki` client certificate verifier configuration using
    /// the [process-default `CryptoProvider`][CryptoProvider#using-the-per-process-default-cryptoprovider].
    ///
    /// Client certificate authentication will be offered by the server, and client certificates
    /// will be verified using the trust anchors found in the provided `roots`. If you
    /// wish to disable client authentication use [`WebPkiClientVerifier::no_client_auth()`] instead.
    ///
    /// Use [`Self::builder_with_provider`] if you wish to specify an explicit provider.
    ///
    /// For more information, see the [`ClientCertVerifierBuilder`] documentation.
    pub fn builder(roots: Arc<RootCertStore>) -> ClientCertVerifierBuilder {
        Self::builder_with_provider(
            roots,
            Arc::clone(CryptoProvider::get_default_or_install_from_crate_features()),
        )
    }

    /// Create a builder for the `webpki` client certificate verifier configuration using
    /// a specified [`CryptoProvider`].
    ///
    /// Client certificate authentication will be offered by the server, and client certificates
    /// will be verified using the trust anchors found in the provided `roots`. If you
    /// wish to disable client authentication use [WebPkiClientVerifier::no_client_auth()] instead.
    ///
    /// The cryptography used comes from the specified [`CryptoProvider`].
    ///
    /// For more information, see the [`ClientCertVerifierBuilder`] documentation.
    pub fn builder_with_provider(
        roots: Arc<RootCertStore>,
        provider: Arc<CryptoProvider>,
    ) -> ClientCertVerifierBuilder {
        ClientCertVerifierBuilder::new(roots, provider.signature_verification_algorithms)
    }

    /// Create a new `WebPkiClientVerifier` that disables client authentication. The server will
    /// not offer client authentication and anonymous clients will be accepted.
    ///
    /// This is in contrast to using `WebPkiClientVerifier::builder().allow_unauthenticated().build()`,
    /// which will produce a verifier that will offer client authentication, but not require it.
    pub fn no_client_auth() -> Arc<dyn ClientCertVerifier> {
        Arc::new(NoClientAuth {})
    }

    /// Construct a new `WebpkiClientVerifier`.
    ///
    /// * `roots` is a list of trust anchors to use for certificate validation.
    /// * `root_hint_subjects` is a list of distinguished names to use for hinting acceptable
    ///   certificate authority subjects to a client.
    /// * `crls` is a `Vec` of owned certificate revocation lists (CRLs) to use for
    ///   client certificate validation.
    /// * `revocation_check_depth` controls which certificates have their revocation status checked
    ///   when `crls` are provided.
    /// * `unknown_revocation_policy` controls how certificates with an unknown revocation status
    ///   are handled when `crls` are provided.
    /// * `anonymous_policy` controls whether client authentication is required, or if anonymous
    ///   clients can connect.
    /// * `supported_algs` specifies which signature verification algorithms should be used.
    pub(crate) fn new(
        roots: Arc<RootCertStore>,
        root_hint_subjects: Vec<DistinguishedName>,
        crls: Vec<CertRevocationList<'static>>,
        revocation_check_depth: RevocationCheckDepth,
        unknown_revocation_policy: UnknownStatusPolicy,
        revocation_expiration_policy: ExpirationPolicy,
        anonymous_policy: AnonymousClientPolicy,
        supported_algs: WebPkiSupportedAlgorithms,
    ) -> Self {
        Self {
            roots,
            root_hint_subjects,
            crls,
            revocation_check_depth,
            unknown_revocation_policy,
            revocation_expiration_policy,
            anonymous_policy,
            supported_algs,
        }
    }
}

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

    fn client_auth_mandatory(&self) -> bool {
        match self.anonymous_policy {
            AnonymousClientPolicy::Allow => false,
            AnonymousClientPolicy::Deny => true,
        }
    }

    fn root_hint_subjects(&self) -> &[DistinguishedName] {
        &self.root_hint_subjects
    }

    fn verify_client_cert(
        &self,
        end_entity: &CertificateDer<'_>,
        intermediates: &[CertificateDer<'_>],
        now: UnixTime,
    ) -> Result<ClientCertVerified, Error> {
        let cert = ParsedCertificate::try_from(end_entity)?;

        let crl_refs = self.crls.iter().collect::<Vec<_>>();

        let revocation = if self.crls.is_empty() {
            None
        } else {
            Some(
                webpki::RevocationOptionsBuilder::new(&crl_refs)
                    // Note: safe to unwrap here - new is only fallible if no CRLs are provided
                    //       and we verify this above.
                    .unwrap()
                    .with_depth(self.revocation_check_depth)
                    .with_status_policy(self.unknown_revocation_policy)
                    .with_expiration_policy(self.revocation_expiration_policy)
                    .build(),
            )
        };

        cert.0
            .verify_for_usage(
                self.supported_algs.all,
                &self.roots.roots,
                intermediates,
                now,
                webpki::KeyUsage::client_auth(),
                revocation,
                None,
            )
            .map_err(pki_error)
            .map(|_| ClientCertVerified::assertion())
    }

    fn verify_tls12_signature(
        &self,
        message: &[u8],
        cert: &CertificateDer<'_>,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_tls12_signature(message, cert, dss, &self.supported_algs)
    }

    fn verify_tls13_signature(
        &self,
        message: &[u8],
        cert: &CertificateDer<'_>,
        dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, Error> {
        verify_tls13_signature(message, cert, dss, &self.supported_algs)
    }

    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
        self.supported_algs.supported_schemes()
    }
}

/// Controls how the [WebPkiClientVerifier] handles anonymous clients.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum AnonymousClientPolicy {
    /// Clients that do not present a client certificate are allowed.
    Allow,
    /// Clients that do not present a client certificate are denied.
    Deny,
}

test_for_each_provider! {
    use super::WebPkiClientVerifier;
    use crate::server::VerifierBuilderError;
    use crate::RootCertStore;

    use pki_types::{CertificateDer, CertificateRevocationListDer};

    use std::prelude::v1::*;
    use std::sync::Arc;
    use std::{vec, format, println};

    fn load_crls(crls_der: &[&[u8]]) -> Vec<CertificateRevocationListDer<'static>> {
        crls_der
            .iter()
            .map(|pem_bytes| {
                rustls_pemfile::crls(&mut &pem_bytes[..])
                    .next()
                    .unwrap()
                    .unwrap()
            })
            .collect()
    }

    fn test_crls() -> Vec<CertificateRevocationListDer<'static>> {
        load_crls(&[
            include_bytes!("../../../test-ca/ecdsa-p256/client.revoked.crl.pem").as_slice(),
            include_bytes!("../../../test-ca/rsa-2048/client.revoked.crl.pem").as_slice(),
        ])
    }

    fn load_roots(roots_der: &[&[u8]]) -> Arc<RootCertStore> {
        let mut roots = RootCertStore::empty();
        roots_der.iter().for_each(|der| {
            roots
                .add(CertificateDer::from(der.to_vec()))
                .unwrap()
        });
        roots.into()
    }

    fn test_roots() -> Arc<RootCertStore> {
        load_roots(&[
            include_bytes!("../../../test-ca/ecdsa-p256/ca.der").as_slice(),
            include_bytes!("../../../test-ca/rsa-2048/ca.der").as_slice(),
        ])
    }

    #[test]
    fn test_client_verifier_no_auth() {
        // We should be able to build a verifier that turns off client authentication.
        WebPkiClientVerifier::no_client_auth();
    }

    #[test]
    fn test_client_verifier_required_auth() {
        // We should be able to build a verifier that requires client authentication, and does
        // no revocation checking.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        );
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_optional_auth() {
        // We should be able to build a verifier that allows client authentication, and anonymous
        // access, and does no revocation checking.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .allow_unauthenticated();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_without_crls_required_auth() {
        // We should be able to build a verifier that requires client authentication, and does
        // no revocation checking, that hasn't been configured to determine how to handle
        // unauthenticated clients yet.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        );
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_without_crls_opptional_auth() {
        // We should be able to build a verifier that allows client authentication,
        // and anonymous access, that does no revocation checking.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .allow_unauthenticated();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_with_invalid_crls() {
        // Trying to build a client verifier with invalid CRLs should error at build time.
        let result = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(vec![CertificateRevocationListDer::from(vec![0xFF])])
        .build();
        assert!(matches!(result, Err(VerifierBuilderError::InvalidCrl(_))));
    }

    #[test]
    fn test_with_crls_multiple_calls() {
        // We should be able to call `with_crls` on a client verifier multiple times.
        let initial_crls = test_crls();
        let extra_crls =
            load_crls(&[
                include_bytes!("../../../test-ca/eddsa/client.revoked.crl.pem").as_slice(),
            ]);
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(initial_crls.clone())
        .with_crls(extra_crls.clone());

        // There should be the expected number of crls.
        assert_eq!(builder.crls.len(), initial_crls.len() + extra_crls.len());
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_with_crls_required_auth_implicit() {
        // We should be able to build a verifier that requires client authentication, and that does
        // revocation checking with CRLs, and that does not allow any anonymous access.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(test_crls());
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_with_crls_optional_auth() {
        // We should be able to build a verifier that supports client authentication, that does
        // revocation checking with CRLs, and that allows anonymous access.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(test_crls())
        .allow_unauthenticated();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_ee_only() {
        // We should be able to build a client verifier that only checks EE revocation status.
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(test_crls())
        .only_check_end_entity_revocation();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_allow_unknown() {
        // We should be able to build a client verifier that allows unknown revocation status
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(test_crls())
        .allow_unknown_revocation_status();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_client_verifier_enforce_expiration() {
        // We should be able to build a client verifier that allows unknown revocation status
        let builder = WebPkiClientVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .with_crls(test_crls())
        .enforce_revocation_expiration();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

    #[test]
    fn test_builder_no_roots() {
        // Trying to create a client verifier builder with no trust anchors should fail at build time
        let result = WebPkiClientVerifier::builder_with_provider(
            RootCertStore::empty().into(),
            provider::default_provider().into(),
        )
        .build();
        assert!(matches!(result, Err(VerifierBuilderError::NoRootAnchors)));
    }

    #[test]
    fn smoke() {
        let all = vec![
            VerifierBuilderError::NoRootAnchors,
            VerifierBuilderError::InvalidCrl(crate::CertRevocationListError::ParseError),
        ];

        for err in all {
            let _ = format!("{:?}", err);
            let _ = format!("{}", err);
        }
    }
}