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
// Copyright 2023 Daniel McCarney.
//
// 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 pki_types::{SignatureVerificationAlgorithm, UnixTime};
use crate::error::Error;
use crate::verify_cert::{Budget, PathNode, Role};
use crate::{der, public_values_eq};
use core::fmt::Debug;
mod types;
pub use types::{
BorrowedCertRevocationList, BorrowedRevokedCert, CertRevocationList, RevocationReason,
};
#[cfg(feature = "alloc")]
pub use types::{OwnedCertRevocationList, OwnedRevokedCert};
/// Builds a RevocationOptions instance to control how revocation checking is performed.
#[derive(Debug, Copy, Clone)]
pub struct RevocationOptionsBuilder<'a> {
crls: &'a [&'a CertRevocationList<'a>],
depth: RevocationCheckDepth,
status_policy: UnknownStatusPolicy,
expiration_policy: ExpirationPolicy,
}
impl<'a> RevocationOptionsBuilder<'a> {
/// Create a builder that will perform revocation checking using the provided certificate
/// revocation lists (CRLs). At least one CRL must be provided.
///
/// Use [RevocationOptionsBuilder::build] to create a [RevocationOptions] instance.
///
/// By default revocation checking will be performed on both the end-entity (leaf) certificate
/// and intermediate certificates. This can be customized using the
/// [RevocationOptionsBuilder::with_depth] method.
///
/// By default revocation checking will fail if the revocation status of a certificate cannot
/// be determined. This can be customized using the
/// [RevocationOptionsBuilder::with_status_policy] method.
///
/// By default revocation checking will *not* fail if the verification time is beyond the time
/// in the CRL nextUpdate field. This can be customized using the
/// [RevocationOptionsBuilder::with_expiration_policy] method.
pub fn new(crls: &'a [&'a CertRevocationList<'a>]) -> Result<Self, CrlsRequired> {
if crls.is_empty() {
return Err(CrlsRequired(()));
}
Ok(Self {
crls,
depth: RevocationCheckDepth::Chain,
status_policy: UnknownStatusPolicy::Deny,
expiration_policy: ExpirationPolicy::Ignore,
})
}
/// Customize the depth at which revocation checking will be performed, controlling
/// whether only the end-entity (leaf) certificate in the chain to a trust anchor will
/// have its revocation status checked, or whether the intermediate certificates will as well.
pub fn with_depth(mut self, depth: RevocationCheckDepth) -> Self {
self.depth = depth;
self
}
/// Customize whether unknown revocation status is an error, or permitted.
pub fn with_status_policy(mut self, policy: UnknownStatusPolicy) -> Self {
self.status_policy = policy;
self
}
/// Customize whether the CRL nextUpdate field (i.e. expiration) is enforced.
pub fn with_expiration_policy(mut self, policy: ExpirationPolicy) -> Self {
self.expiration_policy = policy;
self
}
/// Construct a [RevocationOptions] instance based on the builder's configuration.
pub fn build(self) -> RevocationOptions<'a> {
RevocationOptions {
crls: self.crls,
depth: self.depth,
status_policy: self.status_policy,
expiration_policy: self.expiration_policy,
}
}
}
/// Describes how revocation checking is performed, if at all. Can be constructed with a
/// [RevocationOptionsBuilder] instance.
#[derive(Debug, Copy, Clone)]
pub struct RevocationOptions<'a> {
pub(crate) crls: &'a [&'a CertRevocationList<'a>],
pub(crate) depth: RevocationCheckDepth,
pub(crate) status_policy: UnknownStatusPolicy,
pub(crate) expiration_policy: ExpirationPolicy,
}
impl<'a> RevocationOptions<'a> {
#[allow(clippy::too_many_arguments)]
pub(crate) fn check(
&self,
path: &PathNode<'_>,
issuer_subject: untrusted::Input<'_>,
issuer_spki: untrusted::Input<'_>,
issuer_ku: Option<untrusted::Input<'_>>,
supported_sig_algs: &[&dyn SignatureVerificationAlgorithm],
budget: &mut Budget,
time: UnixTime,
) -> Result<Option<CertNotRevoked>, Error> {
assert!(public_values_eq(path.cert.issuer, issuer_subject));
// If the policy only specifies checking EndEntity revocation state and we're looking at an
// issuer certificate, return early without considering the certificate's revocation state.
if let (RevocationCheckDepth::EndEntity, Role::Issuer) = (self.depth, path.role()) {
return Ok(None);
}
let crl = self
.crls
.iter()
.find(|candidate_crl| candidate_crl.authoritative(path));
use UnknownStatusPolicy::*;
let crl = match (crl, self.status_policy) {
(Some(crl), _) => crl,
// If the policy allows unknown, return Ok(None) to indicate that the certificate
// was not confirmed as CertNotRevoked, but that this isn't an error condition.
(None, Allow) => return Ok(None),
// Otherwise, this is an error condition based on the provided policy.
(None, _) => return Err(Error::UnknownRevocationStatus),
};
// Verify the CRL signature with the issuer SPKI.
// TODO(XXX): consider whether we can refactor so this happens once up-front, instead
// of per-lookup.
// https://github.com/rustls/webpki/issues/81
crl.verify_signature(supported_sig_algs, issuer_spki, budget)
.map_err(crl_signature_err)?;
if self.expiration_policy == ExpirationPolicy::Enforce {
crl.check_expiration(time)?;
}
// Verify that if the issuer has a KeyUsage bitstring it asserts cRLSign.
KeyUsageMode::CrlSign.check(issuer_ku)?;
// Try to find the cert serial in the verified CRL contents.
let cert_serial = path.cert.serial.as_slice_less_safe();
match crl.find_serial(cert_serial)? {
None => Ok(Some(CertNotRevoked::assertion())),
Some(_) => Err(Error::CertRevoked),
}
}
}
// https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.3
#[repr(u8)]
#[derive(Clone, Copy)]
enum KeyUsageMode {
// DigitalSignature = 0,
// ContentCommitment = 1,
// KeyEncipherment = 2,
// DataEncipherment = 3,
// KeyAgreement = 4,
// CertSign = 5,
CrlSign = 6,
// EncipherOnly = 7,
// DecipherOnly = 8,
}
impl KeyUsageMode {
// https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.3
fn check(self, input: Option<untrusted::Input<'_>>) -> Result<(), Error> {
let bit_string = match input {
Some(input) => {
der::expect_tag(&mut untrusted::Reader::new(input), der::Tag::BitString)?
}
// While RFC 5280 requires KeyUsage be present, historically the absence of a KeyUsage
// has been treated as "Any Usage". We follow that convention here and assume the absence
// of KeyUsage implies the required_ku_bit_if_present we're checking for.
None => return Ok(()),
};
let flags = der::bit_string_flags(bit_string)?;
#[allow(clippy::as_conversions)] // u8 always fits in usize.
match flags.bit_set(self as usize) {
true => Ok(()),
false => Err(Error::IssuerNotCrlSigner),
}
}
}
// When verifying CRL signed data we want to disambiguate the context of possible errors by mapping
// them to CRL specific variants that a consumer can use to tell the issue was with the CRL's
// signature, not a certificate.
fn crl_signature_err(err: Error) -> Error {
match err {
Error::UnsupportedSignatureAlgorithm => Error::UnsupportedCrlSignatureAlgorithm,
Error::UnsupportedSignatureAlgorithmForPublicKey => {
Error::UnsupportedCrlSignatureAlgorithmForPublicKey
}
Error::InvalidSignatureForPublicKey => Error::InvalidCrlSignatureForPublicKey,
_ => err,
}
}
/// Describes how much of a certificate chain is checked for revocation status.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum RevocationCheckDepth {
/// Only check the end entity (leaf) certificate's revocation status.
EndEntity,
/// Check the revocation status of the end entity (leaf) and all intermediates.
Chain,
}
/// Describes how to handle the case where a certificate's revocation status is unknown.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum UnknownStatusPolicy {
/// Treat unknown revocation status permissively, acting as if the certificate were
/// not revoked.
Allow,
/// Treat unknown revocation status as an error condition, yielding
/// [Error::UnknownRevocationStatus].
Deny,
}
/// Describes how to handle the nextUpdate field of the CRL (i.e. expiration).
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum ExpirationPolicy {
/// Enforce the verification time is before the time in the nextUpdate field.
/// Treats an expired CRL as an error condition yielding [Error::CrlExpired].
Enforce,
/// Ignore the CRL nextUpdate field.
Ignore,
}
// Zero-sized marker type representing positive assertion that revocation status was checked
// for a certificate and the result was that the certificate is not revoked.
pub(crate) struct CertNotRevoked(());
impl CertNotRevoked {
// Construct a CertNotRevoked marker.
fn assertion() -> Self {
Self(())
}
}
#[derive(Debug, Copy, Clone)]
/// An opaque error indicating the caller must provide at least one CRL when building a
/// [RevocationOptions] instance.
pub struct CrlsRequired(pub(crate) ());
#[cfg(test)]
mod tests {
use super::*;
#[test]
// redundant clone, clone_on_copy allowed to verify derived traits.
#[allow(clippy::redundant_clone, clippy::clone_on_copy)]
fn test_revocation_opts_builder() {
// Trying to build a RevocationOptionsBuilder w/o CRLs should err.
let result = RevocationOptionsBuilder::new(&[]);
assert!(matches!(result, Err(CrlsRequired(_))));
// The CrlsRequired error should be debug and clone when alloc is enabled.
#[cfg(feature = "alloc")]
{
let err = result.unwrap_err();
std::println!("{:?}", err.clone());
}
// It should be possible to build a revocation options builder with defaults.
let crl = include_bytes!("../../tests/crls/crl.valid.der");
let crl = BorrowedCertRevocationList::from_der(&crl[..])
.unwrap()
.into();
let crls = [&crl];
let builder = RevocationOptionsBuilder::new(&crls).unwrap();
#[cfg(feature = "alloc")]
{
// The builder should be debug, and clone when alloc is enabled
std::println!("{:?}", builder);
_ = builder.clone();
}
let opts = builder.build();
assert_eq!(opts.depth, RevocationCheckDepth::Chain);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Deny);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Ignore);
assert_eq!(opts.crls.len(), 1);
// It should be possible to build a revocation options builder with custom depth.
let opts = RevocationOptionsBuilder::new(&crls)
.unwrap()
.with_depth(RevocationCheckDepth::EndEntity)
.build();
assert_eq!(opts.depth, RevocationCheckDepth::EndEntity);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Deny);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Ignore);
assert_eq!(opts.crls.len(), 1);
// It should be possible to build a revocation options builder that allows unknown
// revocation status.
let opts = RevocationOptionsBuilder::new(&crls)
.unwrap()
.with_status_policy(UnknownStatusPolicy::Allow)
.build();
assert_eq!(opts.depth, RevocationCheckDepth::Chain);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Allow);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Ignore);
assert_eq!(opts.crls.len(), 1);
// It should be possible to specify both depth and unknown status policy together.
let opts = RevocationOptionsBuilder::new(&crls)
.unwrap()
.with_status_policy(UnknownStatusPolicy::Allow)
.with_depth(RevocationCheckDepth::EndEntity)
.build();
assert_eq!(opts.depth, RevocationCheckDepth::EndEntity);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Allow);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Ignore);
assert_eq!(opts.crls.len(), 1);
// The same should be true for explicitly forbidding unknown status.
let opts = RevocationOptionsBuilder::new(&crls)
.unwrap()
.with_status_policy(UnknownStatusPolicy::Deny)
.with_depth(RevocationCheckDepth::EndEntity)
.build();
assert_eq!(opts.depth, RevocationCheckDepth::EndEntity);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Deny);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Ignore);
assert_eq!(opts.crls.len(), 1);
// It should be possible to build a revocation options builder that allows unknown
// revocation status.
let opts = RevocationOptionsBuilder::new(&crls)
.unwrap()
.with_expiration_policy(ExpirationPolicy::Enforce)
.build();
assert_eq!(opts.depth, RevocationCheckDepth::Chain);
assert_eq!(opts.status_policy, UnknownStatusPolicy::Deny);
assert_eq!(opts.expiration_policy, ExpirationPolicy::Enforce);
assert_eq!(opts.crls.len(), 1);
// Built revocation options should be debug and clone when alloc is enabled.
#[cfg(feature = "alloc")]
{
std::println!("{:?}", opts.clone());
}
}
}