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

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

use crate::crypto::{CryptoProvider, WebPkiSupportedAlgorithms};
use crate::log::trace;
use crate::verify::{
    DigitallySignedStruct, HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier,
};
use crate::webpki::verify::{
    verify_server_cert_signed_by_trust_anchor_impl, verify_tls12_signature, verify_tls13_signature,
    ParsedCertificate,
};
use crate::webpki::{parse_crls, verify_server_name, VerifierBuilderError};
#[cfg(doc)]
use crate::{crypto, ConfigBuilder, ServerConfig};
use crate::{Error, RootCertStore, SignatureScheme};

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

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

    /// 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.
    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 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 server certificate verifier, allowing control over the root certificates to use as
    /// trust anchors, and to control how server certificate revocation checking is performed.
    ///
    /// If `with_signature_verification_algorithms` was not called on the builder, a default set of
    /// signature verification algorithms is used, controlled by the selected [`crypto::CryptoProvider`].
    ///
    /// Once built, the provided `Arc<dyn ServerCertVerifier>` 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<WebPkiServerVerifier>, VerifierBuilderError> {
        if self.roots.is_empty() {
            return Err(VerifierBuilderError::NoRootAnchors);
        }

        Ok(WebPkiServerVerifier::new(
            self.roots,
            parse_crls(self.crls)?,
            self.revocation_check_depth,
            self.unknown_revocation_policy,
            self.revocation_expiration_policy,
            self.supported_algs,
        )
        .into())
    }
}

/// Default `ServerCertVerifier`, see the trait impl for more information.
#[allow(unreachable_pub)]
#[derive(Debug)]
pub struct WebPkiServerVerifier {
    roots: Arc<RootCertStore>,
    crls: Vec<CertRevocationList<'static>>,
    revocation_check_depth: RevocationCheckDepth,
    unknown_revocation_policy: UnknownStatusPolicy,
    revocation_expiration_policy: ExpirationPolicy,
    supported: WebPkiSupportedAlgorithms,
}

#[allow(unreachable_pub)]
impl WebPkiServerVerifier {
    /// Create a builder for the `webpki` server certificate verifier configuration using
    /// the [process-default `CryptoProvider`][CryptoProvider#using-the-per-process-default-cryptoprovider].
    ///
    /// Server certificates will be verified using the trust anchors found in the provided `roots`.
    ///
    /// Use [`Self::builder_with_provider`] if you wish to specify an explicit provider.
    ///
    /// For more information, see the [`ServerCertVerifierBuilder`] documentation.
    pub fn builder(roots: Arc<RootCertStore>) -> ServerCertVerifierBuilder {
        Self::builder_with_provider(
            roots,
            Arc::clone(CryptoProvider::get_default_or_install_from_crate_features()),
        )
    }

    /// Create a builder for the `webpki` server certificate verifier configuration using
    /// a specified [`CryptoProvider`].
    ///
    /// Server certificates will be verified using the trust anchors found in the provided `roots`.
    ///
    /// The cryptography used comes from the specified [`CryptoProvider`].
    ///
    /// For more information, see the [`ServerCertVerifierBuilder`] documentation.
    pub fn builder_with_provider(
        roots: Arc<RootCertStore>,
        provider: Arc<CryptoProvider>,
    ) -> ServerCertVerifierBuilder {
        ServerCertVerifierBuilder::new(roots, provider.signature_verification_algorithms)
    }

    /// Short-cut for creating a `WebPkiServerVerifier` that does not perform certificate revocation
    /// checking, avoiding the need to use a builder.
    pub(crate) fn new_without_revocation(
        roots: impl Into<Arc<RootCertStore>>,
        supported_algs: WebPkiSupportedAlgorithms,
    ) -> Self {
        Self::new(
            roots,
            Vec::default(),
            RevocationCheckDepth::Chain,
            UnknownStatusPolicy::Allow,
            ExpirationPolicy::Ignore,
            supported_algs,
        )
    }

    /// Constructs a new `WebPkiServerVerifier`.
    ///
    /// * `roots` is the set of trust anchors to trust for issuing server certs.
    /// * `crls` are 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.
    /// * `supported` is the set of supported algorithms that will be used for
    ///   certificate verification and TLS handshake signature verification.
    pub(crate) fn new(
        roots: impl Into<Arc<RootCertStore>>,
        crls: Vec<CertRevocationList<'static>>,
        revocation_check_depth: RevocationCheckDepth,
        unknown_revocation_policy: UnknownStatusPolicy,
        revocation_expiration_policy: ExpirationPolicy,
        supported: WebPkiSupportedAlgorithms,
    ) -> Self {
        Self {
            roots: roots.into(),
            crls,
            revocation_check_depth,
            unknown_revocation_policy,
            revocation_expiration_policy,
            supported,
        }
    }
}

impl ServerCertVerifier for WebPkiServerVerifier {
    /// Will verify the certificate is valid in the following ways:
    /// - Signed by a trusted `RootCertStore` CA
    /// - Not Expired
    /// - Valid for DNS entry
    /// - Valid revocation status (if applicable).
    ///
    /// Depending on the verifier's configuration revocation status checking may be performed for
    /// each certificate in the chain to a root CA (excluding the root itself), or only the
    /// end entity certificate. Similarly, unknown revocation status may be treated as an error
    /// or allowed based on configuration.
    fn verify_server_cert(
        &self,
        end_entity: &CertificateDer<'_>,
        intermediates: &[CertificateDer<'_>],
        server_name: &ServerName<'_>,
        ocsp_response: &[u8],
        now: UnixTime,
    ) -> Result<ServerCertVerified, 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 {
            // Note: unwrap here is safe because RevocationOptionsBuilder only errors when given
            //       empty CRLs.
            Some(
                webpki::RevocationOptionsBuilder::new(crl_refs.as_slice())
                    // 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(),
            )
        };

        // Note: we use the crate-internal `_impl` fn here in order to provide revocation
        // checking information, if applicable.
        verify_server_cert_signed_by_trust_anchor_impl(
            &cert,
            &self.roots,
            intermediates,
            revocation,
            now,
            self.supported.all,
        )?;

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

        verify_server_name(&cert, server_name)?;
        Ok(ServerCertVerified::assertion())
    }

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

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

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

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

    use pki_types::{CertificateDer, CertificateRevocationListDer};

    use super::{VerifierBuilderError, WebPkiServerVerifier};
    use crate::RootCertStore;

    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_with_invalid_crls() {
        // Trying to build a server verifier with invalid CRLs should error at build time.
        let result = WebPkiServerVerifier::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 server 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 = WebPkiServerVerifier::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_builder_no_roots() {
        // Trying to create a server verifier builder with no trust anchors should fail at build time
        let result = WebPkiServerVerifier::builder_with_provider(
            RootCertStore::empty().into(),
            provider::default_provider().into(),
        )
        .build();
        assert!(matches!(result, Err(VerifierBuilderError::NoRootAnchors)));
    }

    #[test]
    fn test_server_verifier_ee_only() {
        // We should be able to build a server cert. verifier that only checks the EE cert.
        let builder = WebPkiServerVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .only_check_end_entity_revocation();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

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

    #[test]
    fn test_server_verifier_allow_unknown_ee_only() {
        // We should be able to build a server cert. verifier that allows unknown revocation
        // status and only checks the EE cert.
        let builder = WebPkiServerVerifier::builder_with_provider(
            test_roots(),
            provider::default_provider().into(),
        )
        .allow_unknown_revocation_status()
        .only_check_end_entity_revocation();
        // The builder should be Debug.
        println!("{:?}", builder);
        builder.build().unwrap();
    }

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