pkix-revocation

Certificate revocation checking for pkix-path and pkix-chain.

Provides the [RevocationChecker] trait and three implementations:

Design: offline by default

All checkers are offline — the caller supplies pre-fetched DER bytes. There is no network I/O in this crate. This keeps the core no_std-compatible and lets you control fetching (cache, rate-limit, pre-fetch at startup).

For online fetching from CRL Distribution Points and OCSP URLs found in certificates, see [pkix-revocation-http].

Usage

No revocation (offline/embedded)

use pkix_revocation::NoRevocation;
// Pass to pkix_chain::verify_chain as the revocation argument.
// Always returns Ok(()); suitable for closed networks, short-lived certs,
// hardware attestation where issuance is the control.

CRL checking

use pkix_revocation::{CrlChecker, RevocationChecker};
use pkix_path::DefaultVerifier;

let crl_der = std::fs::read("issuing-ca.crl")?;
let checker = CrlChecker::new(crl_der, now_unix, DefaultVerifier);

// Called once per certificate by pkix_chain::verify_chain,
// or directly:
checker.check_revocation(&leaf_cert, &issuer_cert)?;

OCSP checking

use pkix_revocation::{OcspChecker, RevocationChecker};
use pkix_path::DefaultVerifier;

let ocsp_response_der = fetch_ocsp_response(...);
let checker = OcspChecker::new(ocsp_response_der, now_unix, DefaultVerifier);
checker.check_revocation(&leaf_cert, &issuer_cert)?;

Custom revocation

use pkix_revocation::RevocationChecker;
use x509_cert::Certificate;

struct MyRevocationChecker;

impl RevocationChecker for MyRevocationChecker {
    fn check_revocation(
        &self,
        cert: &Certificate,
        issuer: &Certificate,
    ) -> pkix_revocation::Result<()> {
        // consult your own database, HSM, or policy
        Ok(())
    }
}

How CRL checking works

CrlChecker::check_revocation:

1. Parses the DER-encoded CertificateList (RFC 5280 §5).
2. Verifies the CRL signature against the issuer's SPKI.
3. Checks the CRL's issuer field matches the certificate's issuer.
4. Checks thisUpdate ≤ now ≤ nextUpdate (absent nextUpdate → fail).
5. Searches revokedCertificates for the certificate's serial number.
6. Returns Err(Revoked { serial, reason_code }) if found, Ok(()) if not.

How OCSP checking works

OcspChecker::check_revocation:

1. Parses the DER-encoded OCSPResponse (RFC 6960 §4.2).
2. Requires responseStatus == successful.
3. Verifies the signature on BasicOCSPResponse against the issuer's SPKI.
4. Finds the SingleResponse matching the certificate's serial number.
5. Checks producedAt ≤ now, thisUpdate ≤ now, now ≤ nextUpdate.
6. Returns based on certStatus: good → Ok(()), revoked → Err(Revoked), unknown → Err(OcspStatusUnknown).

v0.1 limitations

• CRL checking does not follow CRL Distribution Points — caller supplies the CRL.
• Delta CRLs are not supported.
• OCSP checking only supports issuer-signed (direct) responses; delegated responder certificates are not supported.
• SingleResponse matching is by serial number only; issuerNameHash and issuerKeyHash are not verified.

Standards

• [RFC 5280] §5 — CRL Profile
• [RFC 5280] §4.2.1.13 — CRL Distribution Points
• [RFC 6960] — Online Certificate Status Protocol (OCSP)

License

Apache-2.0 OR MIT