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
// Copyright 2015 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

use core::fmt;
use core::ops::ControlFlow;

/// An error that occurs during certificate validation or name validation.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
#[non_exhaustive]
pub enum Error {
    /// The encoding of some ASN.1 DER-encoded item is invalid.
    BadDer,

    /// The encoding of an ASN.1 DER-encoded time is invalid.
    BadDerTime,

    /// A CA certificate is being used as an end-entity certificate.
    CaUsedAsEndEntity,

    /// The certificate is expired; i.e. the time it is being validated for is
    /// later than the certificate's notAfter time.
    CertExpired,

    /// The certificate is not valid for the name it is being validated for.
    CertNotValidForName,

    /// The certificate is not valid yet; i.e. the time it is being validated
    /// for is earlier than the certificate's notBefore time.
    CertNotValidYet,

    /// The certificate, or one of its issuers, has been revoked.
    CertRevoked,

    /// The CRL is expired; i.e. the verification time is not before the time
    /// in the CRL nextUpdate field.
    CrlExpired,

    /// An end-entity certificate is being used as a CA certificate.
    EndEntityUsedAsCa,

    /// An X.509 extension is invalid.
    ExtensionValueInvalid,

    /// The certificate validity period (notBefore, notAfter) is invalid; e.g.
    /// the notAfter time is earlier than the notBefore time.
    InvalidCertValidity,

    /// A CRL number extension was invalid:
    ///  - it was mis-encoded
    ///  - it was negative
    ///  - it was too long
    InvalidCrlNumber,

    /// A iPAddress name constraint was invalid:
    /// - it had a sparse network mask (ie, cannot be written in CIDR form).
    /// - it was too long or short
    InvalidNetworkMaskConstraint,

    /// A serial number was invalid:
    ///  - it was misencoded
    ///  - it was negative
    ///  - it was too long
    InvalidSerialNumber,

    /// The CRL signature is invalid for the issuer's public key.
    InvalidCrlSignatureForPublicKey,

    /// The signature is invalid for the given public key.
    InvalidSignatureForPublicKey,

    /// A CRL was signed by an issuer that has a KeyUsage bitstring that does not include
    /// the cRLSign key usage bit.
    IssuerNotCrlSigner,

    /// A presented or reference DNS identifier was malformed, potentially
    /// containing invalid characters or invalid labels.
    MalformedDnsIdentifier,

    /// The certificate extensions are malformed.
    ///
    /// In particular, webpki requires the DNS name(s) be in the subjectAltName
    /// extension as required by the CA/Browser Forum Baseline Requirements
    /// and as recommended by RFC6125.
    MalformedExtensions,

    /// A name constraint was malformed, potentially containing invalid characters or
    /// invalid labels.
    MalformedNameConstraint,

    /// The maximum number of name constraint comparisons has been reached.
    MaximumNameConstraintComparisonsExceeded,

    /// The maximum number of internal path building calls has been reached. Path complexity is too great.
    MaximumPathBuildCallsExceeded,

    /// The path search was terminated because it became too deep.
    MaximumPathDepthExceeded,

    /// The maximum number of signature checks has been reached. Path complexity is too great.
    MaximumSignatureChecksExceeded,

    /// The certificate violates one or more name constraints.
    NameConstraintViolation,

    /// The certificate violates one or more path length constraints.
    PathLenConstraintViolated,

    /// The certificate is not valid for the Extended Key Usage for which it is
    /// being validated.
    RequiredEkuNotFound,

    /// The algorithm in the TBSCertificate "signature" field of a certificate
    /// does not match the algorithm in the signature of the certificate.
    SignatureAlgorithmMismatch,

    /// Trailing data was found while parsing DER-encoded input for the named type.
    TrailingData(DerTypeId),

    /// A valid issuer for the certificate could not be found.
    UnknownIssuer,

    /// The certificate's revocation status could not be determined.
    UnknownRevocationStatus,

    /// The certificate is not a v3 X.509 certificate.
    ///
    /// This error may be also reported if the certificate version field
    /// is malformed.
    UnsupportedCertVersion,

    /// The certificate contains an unsupported critical extension.
    UnsupportedCriticalExtension,

    /// The CRL contains an issuing distribution point with no distribution point name,
    /// or a distribution point name relative to an issuer.
    UnsupportedCrlIssuingDistributionPoint,

    /// The CRL is not a v2 X.509 CRL.
    ///
    /// The RFC 5280 web PKI profile mandates only version 2 be used. See section
    /// 5.1.2.1 for more information.
    ///
    /// This error may also be reported if the CRL version field is malformed.
    UnsupportedCrlVersion,

    /// The CRL is an unsupported "delta" CRL.
    UnsupportedDeltaCrl,

    /// The CRL contains unsupported "indirect" entries.
    UnsupportedIndirectCrl,

    /// The `ServerName` contained an unsupported type of value.
    UnsupportedNameType,

    /// The revocation reason is not in the set of supported revocation reasons.
    UnsupportedRevocationReason,

    /// The CRL is partitioned by revocation reasons.
    UnsupportedRevocationReasonsPartitioning,

    /// The signature algorithm for a signature over a CRL is not in the set of supported
    /// signature algorithms given.
    UnsupportedCrlSignatureAlgorithm,

    /// The signature algorithm for a signature is not in the set of supported
    /// signature algorithms given.
    UnsupportedSignatureAlgorithm,

    /// The CRL signature's algorithm does not match the algorithm of the issuer
    /// public key it is being validated for. This may be because the public key
    /// algorithm's OID isn't recognized (e.g. DSA), or the public key
    /// algorithm's parameters don't match the supported parameters for that
    /// algorithm (e.g. ECC keys for unsupported curves), or the public key
    /// algorithm and the signature algorithm simply don't match (e.g.
    /// verifying an RSA signature with an ECC public key).
    UnsupportedCrlSignatureAlgorithmForPublicKey,

    /// The signature's algorithm does not match the algorithm of the public
    /// key it is being validated for. This may be because the public key
    /// algorithm's OID isn't recognized (e.g. DSA), or the public key
    /// algorithm's parameters don't match the supported parameters for that
    /// algorithm (e.g. ECC keys for unsupported curves), or the public key
    /// algorithm and the signature algorithm simply don't match (e.g.
    /// verifying an RSA signature with an ECC public key).
    UnsupportedSignatureAlgorithmForPublicKey,
}

impl Error {
    // Compare the Error with the new error by rank, returning the higher rank of the two as
    // the most specific error.
    pub(crate) fn most_specific(self, new: Self) -> Self {
        // Assign an error a numeric value ranking it by specificity.
        if self.rank() >= new.rank() {
            self
        } else {
            new
        }
    }

    // Return a numeric indication of how specific the error is, where an error with a higher rank
    // is considered more useful to an end user than an error with a lower rank. This is used by
    // Error::most_specific to compare two errors in order to return which is more specific.
    #[allow(clippy::as_conversions)] // We won't exceed u32 errors.
    pub(crate) fn rank(&self) -> u32 {
        match &self {
            // Errors related to certificate validity
            Self::CertNotValidYet | Self::CertExpired => 290,
            Self::CertNotValidForName => 280,
            Self::CertRevoked | Self::UnknownRevocationStatus | Self::CrlExpired => 270,
            Self::InvalidCrlSignatureForPublicKey | Self::InvalidSignatureForPublicKey => 260,
            Self::SignatureAlgorithmMismatch => 250,
            Self::RequiredEkuNotFound => 240,
            Self::NameConstraintViolation => 230,
            Self::PathLenConstraintViolated => 220,
            Self::CaUsedAsEndEntity | Self::EndEntityUsedAsCa => 210,
            Self::IssuerNotCrlSigner => 200,

            // Errors related to supported features used in an invalid way.
            Self::InvalidCertValidity => 190,
            Self::InvalidNetworkMaskConstraint => 180,
            Self::InvalidSerialNumber => 170,
            Self::InvalidCrlNumber => 160,

            // Errors related to unsupported features.
            Self::UnsupportedCrlSignatureAlgorithmForPublicKey
            | Self::UnsupportedSignatureAlgorithmForPublicKey => 150,
            Self::UnsupportedCrlSignatureAlgorithm | Self::UnsupportedSignatureAlgorithm => 140,
            Self::UnsupportedCriticalExtension => 130,
            Self::UnsupportedCertVersion => 130,
            Self::UnsupportedCrlVersion => 120,
            Self::UnsupportedDeltaCrl => 110,
            Self::UnsupportedIndirectCrl => 100,
            Self::UnsupportedNameType => 95,
            Self::UnsupportedRevocationReason => 90,
            Self::UnsupportedRevocationReasonsPartitioning => 80,
            Self::UnsupportedCrlIssuingDistributionPoint => 70,
            Self::MaximumPathDepthExceeded => 61,

            // Errors related to malformed data.
            Self::MalformedDnsIdentifier => 60,
            Self::MalformedNameConstraint => 50,
            Self::MalformedExtensions | Self::TrailingData(_) => 40,
            Self::ExtensionValueInvalid => 30,

            // Generic DER errors.
            Self::BadDerTime => 20,
            Self::BadDer => 10,

            // Special case errors - not subject to ranking.
            Self::MaximumSignatureChecksExceeded => 0,
            Self::MaximumPathBuildCallsExceeded => 0,
            Self::MaximumNameConstraintComparisonsExceeded => 0,

            // Default catch all error - should be renamed in the future.
            Self::UnknownIssuer => 0,
        }
    }

    /// Returns true for errors that should be considered fatal during path building. Errors of
    /// this class should halt any further path building and be returned immediately.
    #[inline]
    pub(crate) fn is_fatal(&self) -> bool {
        matches!(
            self,
            Self::MaximumSignatureChecksExceeded
                | Self::MaximumPathBuildCallsExceeded
                | Self::MaximumNameConstraintComparisonsExceeded
        )
    }
}

impl From<Error> for ControlFlow<Error, Error> {
    fn from(value: Error) -> Self {
        match value {
            // If an error is fatal, we've exhausted the potential for continued search.
            err if err.is_fatal() => Self::Break(err),
            // Otherwise we've rejected one candidate chain, but may continue to search for others.
            err => Self::Continue(err),
        }
    }
}

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

#[cfg(feature = "std")]
impl ::std::error::Error for Error {}

/// Trailing data was found while parsing DER-encoded input for the named type.
#[allow(missing_docs)]
#[non_exhaustive]
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum DerTypeId {
    BitString,
    Bool,
    Certificate,
    CertificateExtensions,
    CertificateTbsCertificate,
    CertRevocationList,
    CertRevocationListExtension,
    CrlDistributionPoint,
    CommonNameInner,
    CommonNameOuter,
    DistributionPointName,
    Extension,
    GeneralName,
    RevocationReason,
    Signature,
    SignatureAlgorithm,
    SignedData,
    SubjectPublicKeyInfo,
    Time,
    TrustAnchorV1,
    TrustAnchorV1TbsCertificate,
    U8,
    RevokedCertificate,
    RevokedCertificateExtension,
    RevokedCertEntry,
    IssuingDistributionPoint,
}