feat(crl): add CRL consumption and custom verifier for mTLS revocation enforcement

Implements agent-side CRL consumption for mTLS certificate revocation
checking, as specified in issue #20.

Changes:
- NEW: src/auth/crl.rs - CRL loading, parsing, signature verification,
  in-memory revoked serial index (HashSet), 24h background refresh task
- MODIFY: src/auth/mtls.rs - CrlAwareVerifier wrapping WebPkiClientVerifier
  with post-chain CRL serial lookup; fails closed on invalid signature,
  degrades gracefully when CRL is missing
- MODIFY: src/auth/mod.rs - Register crl module, re-export CrlState/CrlStatus
- MODIFY: src/config/loader.rs - Add crl_path field to TlsConfig
- MODIFY: src/main.rs - Load CRL on startup, spawn refresh task, wire
  SharedCrlState into server and health endpoint
- MODIFY: src/api/handlers/system.rs - Add crl_status and crl_age_seconds
  to health check response
- MODIFY: Cargo.toml - Add arc-swap, base64 deps; enable x509-parser
  verify feature for CRL signature verification

Design decisions:
- ArcSwap for lock-free atomic CRL state swaps on the hot path
- O(1) serial lookup via HashSet<String> of hex-encoded serials
- Stale CRL = continue serving + warn + health reports degraded
- Invalid CRL signature = refuse to start (fail-closed)
- Missing CRL = fall back to WebPKI-only (backward compatible)

Companion to PR #26 in linux-patch-manager (manager-side CRL generation)

Refs: #20

Cargo.lock

@@ -390,6 +390,15 @@ version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
 
+[[package]]
+name = "arc-swap"
+version = "1.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a3a1fd6f75306b68087b831f025c712524bcb19aad54e557b1129cfa0a2b207"
+dependencies = [
+ "rustversion",
+]
+
 [[package]]
 name = "arraydeque"
 version = "0.5.1"
@@ -1925,7 +1934,9 @@ dependencies = [
  "actix-web-actors",
  "addr",
  "anyhow",
+ "arc-swap",
  "async-channel",
+ "base64 0.22.1",
  "chrono",
  "clap",
  "config",
@@ -4271,6 +4282,7 @@ dependencies = [
  "lazy_static",
  "nom",
  "oid-registry",
+ "ring",
  "rusticata-macros",
  "thiserror 1.0.69",
  "time",

Cargo.toml

@@ -23,7 +23,7 @@ tokio = { version = "1", features = ["full"] }
 rustls = { version = "0.23", features = ["aws_lc_rs"] }
 rustls-pemfile = "2"
 tokio-rustls = "0.26"
-x509-parser = "0.16"
+x509-parser = { version = "0.16", features = ["verify"] }
 
 # WebSocket support (actix-web-actors provides WebSocket for Actix-web)
 tokio-tungstenite = "0.21"
@@ -83,6 +83,12 @@ socket2 = { version = "0.5", features = ["all"] }
 # File locking for concurrent-safe whitelist modifications
 fs2 = "0.4"
 
+# Atomic swapping for CRL state updates without rebuilding ServerConfig
+arc-swap = "1"
+
+# Base64 decoding for PEM CRL parsing
+base64 = "0.22"
+
 [dev-dependencies]
 actix-rt = "2"
 tokio-test = "0.4"

src/api/handlers/system.rs

@@ -12,6 +12,7 @@ use tracing::{error, info, warn};
 use uuid::Uuid;
 
 use super::packages::ApiResponse;
+use crate::auth::crl::{CrlStatus, SharedCrlState};
 use crate::jobs::manager::{JobManager, JobOperation, JobStatus};
 use crate::packages::PackageManagerBackend;
 
@@ -47,6 +48,8 @@ pub struct HealthData {
     pub version: String,
     pub last_cache_update: Option<String>, // RFC3339 timestamp
     pub cache_status: String,              // "fresh", "stale", "unknown", "failed"
+    pub crl_status: Option<String>,        // "valid", "expired", "missing", "invalid", "degraded"
+    pub crl_age_seconds: Option<u64>,      // age of on-disk CRL file
 }
 
 /// Service status response data
@@ -113,6 +116,7 @@ pub async fn get_system_info(
 pub async fn health_check(
     backend: web::Data<Box<dyn PackageManagerBackend>>,
     cache_state: web::Data<crate::packages::cache::PackageCacheState>,
+    crl_state: web::Data<SharedCrlState>,
     _req: HttpRequest,
 ) -> impl Responder {
     let _request_id = Uuid::new_v4().to_string();
@@ -134,7 +138,7 @@ pub async fn health_check(
 
     // Check cache status and refresh if stale
     let cache_status_val = cache_state.status();
-    let (status, cache_status_str, last_cache_update) = if cache_state.is_stale() {
+    let (mut status, cache_status_str, last_cache_update) = if cache_state.is_stale() {
         match backend.refresh_package_cache(&cache_state) {
             Ok(_) => {
                 let updated = cache_state.status();
@@ -161,12 +165,31 @@ pub async fn health_check(
         )
     };
 
+    // CRL status from shared state
+    let crl = crl_state.load();
+    let crl_status_str = match crl.status {
+        CrlStatus::Valid
+        | CrlStatus::Expired
+        | CrlStatus::Missing
+        | CrlStatus::Invalid
+        | CrlStatus::Degraded => {
+            // Downgrade overall health if CRL is invalid
+            if crl.status == CrlStatus::Invalid {
+                status = "degraded".to_string();
+            }
+            crl.status.to_string()
+        }
+    };
+    let crl_age = crl.crl_age_seconds();
+
     let response = ApiResponse::success(HealthData {
         status,
         uptime_seconds,
         version,
         last_cache_update,
         cache_status: cache_status_str,
+        crl_status: Some(crl_status_str),
+        crl_age_seconds: crl_age,
     });
 
     HttpResponse::Ok().json(response)
@@ -386,6 +409,8 @@ mod tests {
             version: "0.1.0".to_string(),
             last_cache_update: Some("2026-05-27T14:00:00+00:00".to_string()),
             cache_status: "fresh".to_string(),
+            crl_status: Some("valid".to_string()),
+            crl_age_seconds: Some(3600),
         };
         let json = serde_json::to_string(&health).unwrap();
         assert!(json.contains("healthy"));

src/auth/crl.rs

@@ -0,0 +1,413 @@
+//! CRL (Certificate Revocation List) Loading, Parsing, and Refresh
+//!
+//! Provides CRL consumption for agent-side mTLS revocation enforcement.
+//! Parses CRL from disk, verifies signature against pinned CA,
+//! builds an in-memory revoked-serial index, and refreshes from the manager.
+
+use arc_swap::ArcSwap;
+use std::collections::HashSet;
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use std::time::{Duration, SystemTime};
+use tracing::{debug, error, info, warn};
+use x509_parser::prelude::FromDer;
+use x509_parser::revocation_list::CertificateRevocationList;
+
+/// CRL status reported via the health endpoint.
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum CrlStatus {
+    /// CRL loaded, signature valid, not expired.
+    Valid,
+    /// CRL loaded and signature valid, but nextUpdate has passed.
+    Expired,
+    /// No CRL file found on disk.
+    Missing,
+    /// CRL exists but failed signature verification -- fail-closed.
+    Invalid,
+    /// CRL fetch or load failed; operating in degraded (WebPKI-only) mode.
+    Degraded,
+}
+
+impl std::fmt::Display for CrlStatus {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            CrlStatus::Valid => write!(f, "valid"),
+            CrlStatus::Expired => write!(f, "expired"),
+            CrlStatus::Missing => write!(f, "missing"),
+            CrlStatus::Invalid => write!(f, "invalid"),
+            CrlStatus::Degraded => write!(f, "degraded"),
+        }
+    }
+}
+
+/// In-memory CRL state, atomically swapped on refresh via ArcSwap.
+#[derive(Debug, Clone)]
+pub struct CrlState {
+    /// Hex-encoded serial numbers of revoked certificates (lowercase, no prefix).
+    pub revoked_serials: HashSet<String>,
+    /// CRL status for health reporting.
+    pub status: CrlStatus,
+    /// Time the CRL file was last modified (used to compute age).
+    pub crl_mtime: Option<SystemTime>,
+    /// When this CrlState was loaded into memory.
+    pub loaded_at: SystemTime,
+}
+
+impl Default for CrlState {
+    fn default() -> Self {
+        Self {
+            revoked_serials: HashSet::new(),
+            status: CrlStatus::Missing,
+            crl_mtime: None,
+            loaded_at: SystemTime::now(),
+        }
+    }
+}
+
+impl CrlState {
+    /// Check whether a certificate serial is revoked.
+    pub fn is_revoked(&self, serial_hex: &str) -> bool {
+        self.revoked_serials.contains(serial_hex)
+    }
+
+    /// Age of the on-disk CRL file in seconds.
+    pub fn crl_age_seconds(&self) -> Option<u64> {
+        self.crl_mtime.and_then(|mtime| {
+            SystemTime::now()
+                .duration_since(mtime)
+                .ok()
+                .map(|d| d.as_secs())
+        })
+    }
+}
+
+/// Shared, atomically-swappable CRL handle.
+pub type SharedCrlState = Arc<ArcSwap<CrlState>>;
+
+/// Create a new shared CRL state (initially missing).
+pub fn new_shared_state() -> SharedCrlState {
+    Arc::new(ArcSwap::from_pointee(CrlState::default()))
+}
+
+/// Extract the hex-encoded serial from a DER-encoded X.509 certificate.
+/// Returns lowercase hex with no separators or prefix.
+pub fn cert_serial_hex(cert_der: &[u8]) -> Option<String> {
+    x509_parser::parse_x509_certificate(cert_der)
+        .ok()
+        .map(|(_, cert)| format_serial_hex(&cert.serial))
+}
+
+/// Format a BigUint serial as lowercase hex string (no 0x prefix, no colons).
+fn format_serial_hex(serial: &x509_parser::num_bigint::BigUint) -> String {
+    let bytes = serial.to_bytes_be();
+    bytes.iter().map(|b| format!("{:02x}", b)).collect()
+}
+
+/// Load and validate a CRL from disk.
+///
+/// Steps:
+/// 1. Read PEM file
+/// 2. Parse CRL with x509-parser
+/// 3. Verify CRL signature against the CA certificate
+/// 4. Build in-memory revoked-serial index
+/// 5. Check nextUpdate for staleness
+///
+/// Returns the new CrlState. On signature failure, returns CrlStatus::Invalid (fail-closed).
+/// On missing file, returns CrlStatus::Missing. On parse error, returns CrlStatus::Degraded.
+pub fn load_crl(crl_path: &Path, ca_cert_der: &[u8]) -> CrlState {
+    let crl_bytes = match fs::read(crl_path) {
+        Ok(b) => b,
+        Err(e) => {
+            if e.kind() == std::io::ErrorKind::NotFound {
+                info!(path = %crl_path.display(), "No CRL file found -- operating in WebPKI-only mode");
+                return CrlState {
+                    status: CrlStatus::Missing,
+                    crl_mtime: None,
+                    loaded_at: SystemTime::now(),
+                    revoked_serials: HashSet::new(),
+                };
+            }
+            warn!(path = %crl_path.display(), error = %e, "Failed to read CRL file");
+            return CrlState {
+                status: CrlStatus::Degraded,
+                crl_mtime: None,
+                loaded_at: SystemTime::now(),
+                revoked_serials: HashSet::new(),
+            };
+        }
+    };
+
+    let crl_mtime = fs::metadata(crl_path).ok().and_then(|m| m.modified().ok());
+
+    // Parse PEM: extract the DER block between BEGIN/END X509 CRL markers
+    let crl_der = match extract_pem_crl_der(&crl_bytes) {
+        Some(der) => der,
+        None => {
+            // Try parsing as raw DER
+            crl_bytes.clone()
+        }
+    };
+
+    // Parse CRL
+    let (_, crl) = match CertificateRevocationList::from_der(&crl_der) {
+        Ok(r) => r,
+        Err(e) => {
+            error!(error = %e, "Failed to parse CRL -- marking as invalid");
+            return CrlState {
+                status: CrlStatus::Invalid,
+                crl_mtime,
+                loaded_at: SystemTime::now(),
+                revoked_serials: HashSet::new(),
+            };
+        }
+    };
+
+    // Verify CRL signature against CA
+    let (_, ca_cert) = match x509_parser::parse_x509_certificate(ca_cert_der) {
+        Ok(r) => r,
+        Err(e) => {
+            error!(error = %e, "Failed to parse CA cert for CRL signature verification");
+            return CrlState {
+                status: CrlStatus::Invalid,
+                crl_mtime,
+                loaded_at: SystemTime::now(),
+                revoked_serials: HashSet::new(),
+            };
+        }
+    };
+
+    let verify_result = crl.verify_signature(ca_cert.public_key());
+
+    if let Err(e) = verify_result {
+        error!(error = %e, "CRL signature verification FAILED -- refusing to use this CRL (fail-closed)");
+        return CrlState {
+            status: CrlStatus::Invalid,
+            crl_mtime,
+            loaded_at: SystemTime::now(),
+            revoked_serials: HashSet::new(),
+        };
+    }
+
+    // Build revoked serial index
+    let revoked_serials: HashSet<String> = crl
+        .iter_revoked_certificates()
+        .map(|revoked| format_serial_hex(revoked.serial()))
+        .collect();
+
+    info!(
+        revoked_count = revoked_serials.len(),
+        "CRL loaded and signature verified"
+    );
+
+    // Check nextUpdate for staleness
+    let now = x509_parser::time::ASN1Time::now();
+    let is_expired = crl.next_update().map(|next| next < now).unwrap_or(false);
+
+    let status = if is_expired {
+        warn!("CRL nextUpdate has passed -- CRL is stale, continuing with degraded status");
+        CrlStatus::Expired
+    } else {
+        CrlStatus::Valid
+    };
+
+    CrlState {
+        revoked_serials,
+        status,
+        crl_mtime,
+        loaded_at: SystemTime::now(),
+    }
+}
+
+/// Extract DER bytes from a PEM-encoded CRL.
+/// Looks for `-----BEGIN X509 CRL-----` / `-----END X509 CRL-----` blocks.
+fn extract_pem_crl_der(pem_bytes: &[u8]) -> Option<Vec<u8>> {
+    let pem_str = String::from_utf8_lossy(pem_bytes);
+    let begin_marker = "-----BEGIN X509 CRL-----";
+    let end_marker = "-----END X509 CRL-----";
+
+    let begin_idx = pem_str.find(begin_marker)?;
+    let after_begin = begin_idx + begin_marker.len();
+    let end_idx = pem_str[after_begin..].find(end_marker)?;
+    let b64_block = pem_str[after_begin..after_begin + end_idx].trim();
+
+    use base64::Engine;
+    base64::engine::general_purpose::STANDARD
+        .decode(b64_block)
+        .ok()
+}
+
+/// Fetch the CRL from the manager, verify, persist, and update in-memory state.
+///
+/// The CRL endpoint is public (no auth): GET {manager_url}/api/v1/pki/crl.pem
+pub async fn refresh_crl(
+    manager_url: &str,
+    crl_path: &Path,
+    ca_cert_der: &[u8],
+    shared_state: &SharedCrlState,
+) -> Result<(), String> {
+    let crl_url = format!("{}/api/v1/pki/crl.pem", manager_url.trim_end_matches('/'));
+
+    info!(url = %crl_url, "Fetching CRL from manager");
+
+    let response = reqwest::get(&crl_url)
+        .await
+        .map_err(|e| format!("CRL fetch request failed: {}", e))?;
+
+    if !response.status().is_success() {
+        let status = response.status();
+        return Err(format!("CRL fetch returned HTTP {}", status));
+    }
+
+    let crl_pem = response
+        .text()
+        .await
+        .map_err(|e| format!("Failed to read CRL response body: {}", e))?;
+
+    // Persist to disk (atomic write via temp file)
+    let parent = crl_path.parent().unwrap_or(Path::new("/tmp"));
+    if !parent.exists() {
+        fs::create_dir_all(parent).map_err(|e| format!("Failed to create CRL directory: {}", e))?;
+    }
+
+    let tmp_path = crl_path.with_extension("pem.tmp");
+    fs::write(&tmp_path, &crl_pem).map_err(|e| format!("Failed to write temp CRL file: {}", e))?;
+
+    fs::rename(&tmp_path, crl_path)
+        .map_err(|e| format!("Failed to rename temp CRL file: {}", e))?;
+
+    debug!(path = %crl_path.display(), "CRL persisted to disk");
+
+    // Load the freshly written CRL to get a validated CrlState
+    let new_state = load_crl(crl_path, ca_cert_der);
+
+    if new_state.status == CrlStatus::Invalid {
+        return Err("CRL signature verification failed after fetch".to_string());
+    }
+
+    info!(
+        status = %new_state.status,
+        revoked = new_state.revoked_serials.len(),
+        "CRL refreshed successfully"
+    );
+
+    // Atomically swap the in-memory state
+    shared_state.store(Arc::new(new_state));
+
+    Ok(())
+}
+
+/// Spawn the CRL refresh background task.
+///
+/// Runs on a 24-hour interval. On failure, logs a warning and continues
+/// serving with the existing (possibly stale) CRL.
+pub fn spawn_crl_refresh_task(
+    manager_url: String,
+    crl_path: PathBuf,
+    ca_cert_der: Vec<u8>,
+    shared_state: SharedCrlState,
+) {
+    let interval = Duration::from_secs(24 * 60 * 60); // 24 hours
+
+    tokio::spawn(async move {
+        // Initial small delay to let the server finish binding
+        tokio::time::sleep(Duration::from_secs(30)).await;
+
+        loop {
+            let result = refresh_crl(&manager_url, &crl_path, &ca_cert_der, &shared_state).await;
+
+            match result {
+                Ok(()) => {
+                    info!("CRL background refresh completed successfully");
+                }
+                Err(e) => {
+                    warn!(
+                        error = %e,
+                        "CRL background refresh failed -- continuing with current CRL"
+                    );
+                }
+            }
+
+            tokio::time::sleep(interval).await;
+        }
+    });
+
+    info!(
+        interval_secs = interval.as_secs(),
+        "CRL refresh background task spawned"
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_format_serial_hex() {
+        use x509_parser::num_bigint::BigUint;
+        let serial = BigUint::from(0x0123_abcdu64);
+        let hex = format_serial_hex(&serial);
+        assert_eq!(hex, "0123abcd");
+    }
+
+    #[test]
+    fn test_format_serial_hex_single_byte() {
+        use x509_parser::num_bigint::BigUint;
+        let serial = BigUint::from(0x42u64);
+        let hex = format_serial_hex(&serial);
+        assert_eq!(hex, "42");
+    }
+
+    #[test]
+    fn test_crl_state_default_is_missing() {
+        let state = CrlState::default();
+        assert_eq!(state.status, CrlStatus::Missing);
+        assert!(state.revoked_serials.is_empty());
+        assert!(state.crl_mtime.is_none());
+    }
+
+    #[test]
+    fn test_crl_state_is_revoked() {
+        let mut state = CrlState::default();
+        state.revoked_serials.insert("deadbeef".to_string());
+        assert!(state.is_revoked("deadbeef"));
+        assert!(!state.is_revoked("cafef00d"));
+    }
+
+    #[test]
+    fn test_crl_status_display() {
+        assert_eq!(CrlStatus::Valid.to_string(), "valid");
+        assert_eq!(CrlStatus::Expired.to_string(), "expired");
+        assert_eq!(CrlStatus::Missing.to_string(), "missing");
+        assert_eq!(CrlStatus::Invalid.to_string(), "invalid");
+        assert_eq!(CrlStatus::Degraded.to_string(), "degraded");
+    }
+
+    #[test]
+    fn test_extract_pem_crl_der_invalid() {
+        // Not PEM
+        assert!(extract_pem_crl_der(b"not pem").is_none());
+        // PEM but wrong type
+        assert!(extract_pem_crl_der(
+            b"-----BEGIN CERTIFICATE-----\nAA==\n-----END CERTIFICATE-----"
+        )
+        .is_none());
+    }
+
+    #[test]
+    fn test_shared_crl_state_swap() {
+        let shared = new_shared_state();
+        let initial = shared.load();
+        assert_eq!(initial.status, CrlStatus::Missing);
+
+        let mut new_state = CrlState::default();
+        new_state.status = CrlStatus::Valid;
+        new_state.revoked_serials.insert("abc".to_string());
+        shared.store(Arc::new(new_state));
+
+        let updated = shared.load();
+        assert_eq!(updated.status, CrlStatus::Valid);
+        assert!(updated.is_revoked("abc"));
+    }
+}

src/auth/mod.rs

@@ -6,9 +6,11 @@
 //! - Silent drop for non-compliant connections
 //! - Comprehensive audit logging
 
+pub mod crl;
 pub mod mtls;
 pub mod whitelist;
 
+pub use crl::{new_shared_state, CrlState, CrlStatus, SharedCrlState};
 pub use mtls::{ClientCertInfo, MtlsConfig, MtlsError, MtlsMiddleware};
 pub use whitelist::{WhitelistConfig, WhitelistEntry, WhitelistManager, WhitelistMiddleware};
 

src/auth/mtls.rs

@@ -2,6 +2,7 @@
 //!
 //! Provides mutual TLS authentication middleware for Actix-web.
 //! Non-mTLS connections are silently dropped (no response).
+//! Supports CRL-aware client certificate verification when CRL is available.
 
 use actix_web::{
     dev::{forward_ready, Service, ServiceRequest, ServiceResponse, Transform},
@@ -11,14 +12,21 @@ use actix_web::{
 use chrono::{DateTime, Duration, Utc};
 use futures_util::future::LocalBoxFuture;
 use rustls::{
+    client::danger::HandshakeSignatureValid,
     crypto::aws_lc_rs,
-    server::{ServerConfig, WebPkiClientVerifier},
+    pki_types::{CertificateDer, UnixTime},
+    server::{
+        danger::{ClientCertVerified, ClientCertVerifier},
+        ServerConfig, WebPkiClientVerifier,
+    },
     version::TLS13,
-    RootCertStore,
+    DigitallySignedStruct, DistinguishedName, Error as RustlsError, RootCertStore, SignatureScheme,
 };
 use rustls_pemfile::{certs, private_key};
 use std::{fs::File, io::BufReader, sync::Arc};
-use tracing::{debug, info, warn};
+use tracing::{debug, error, info, warn};
+
+use super::crl::{cert_serial_hex, SharedCrlState};
 
 /// Check for duplicate critical headers (VULN-006)
 /// Returns true if duplicate headers are detected
@@ -45,6 +53,107 @@ fn has_duplicate_critical_headers(req: &ServiceRequest) -> bool {
     false
 }
 
+/// CRL-aware client certificate verifier.
+///
+/// Wraps WebPkiClientVerifier for chain validation, then checks the
+/// end-entity certificate serial against the in-memory CRL index.
+/// If CRL is unavailable (Missing/Degraded), falls back to WebPKI-only.
+#[derive(Debug)]
+struct CrlAwareVerifier {
+    inner: Arc<dyn ClientCertVerifier>,
+    crl_state: SharedCrlState,
+}
+
+impl CrlAwareVerifier {
+    fn new(inner: Arc<dyn ClientCertVerifier>, crl_state: SharedCrlState) -> Self {
+        Self { inner, crl_state }
+    }
+}
+
+impl ClientCertVerifier for CrlAwareVerifier {
+    fn offer_client_auth(&self) -> bool {
+        self.inner.offer_client_auth()
+    }
+
+    fn client_auth_mandatory(&self) -> bool {
+        self.inner.client_auth_mandatory()
+    }
+
+    fn root_hint_subjects(&self) -> &[DistinguishedName] {
+        self.inner.root_hint_subjects()
+    }
+
+    fn verify_client_cert(
+        &self,
+        end_entity: &CertificateDer<'_>,
+        intermediates: &[CertificateDer<'_>],
+        now: UnixTime,
+    ) -> Result<ClientCertVerified, RustlsError> {
+        // 1. Delegate chain validation to WebPKI
+        self.inner
+            .verify_client_cert(end_entity, intermediates, now)?;
+
+        // 2. Check CRL revocation status
+        let crl = self.crl_state.load();
+        match crl.status {
+            super::crl::CrlStatus::Valid | super::crl::CrlStatus::Expired => {
+                // CRL is available -- check serial
+                if let Some(serial_hex) = cert_serial_hex(end_entity.as_ref()) {
+                    if crl.is_revoked(&serial_hex) {
+                        warn!(
+                            serial = %serial_hex,
+                            "Client certificate is revoked per CRL -- rejecting connection"
+                        );
+                        return Err(RustlsError::InvalidCertificate(
+                            rustls::CertificateError::Revoked,
+                        ));
+                    }
+                }
+                Ok(ClientCertVerified::assertion())
+            }
+            super::crl::CrlStatus::Missing | super::crl::CrlStatus::Degraded => {
+                // No CRL available -- fall back to WebPKI-only (already passed above)
+                warn!(
+                    status = %crl.status,
+                    "CRL not available -- allowing connection with WebPKI-only verification"
+                );
+                Ok(ClientCertVerified::assertion())
+            }
+            super::crl::CrlStatus::Invalid => {
+                // Invalid CRL signature -- fail-closed
+                error!(
+                    "CRL signature is invalid -- refusing all client certificates (fail-closed)"
+                );
+                Err(RustlsError::InvalidCertificate(
+                    rustls::CertificateError::Revoked,
+                ))
+            }
+        }
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, RustlsError> {
+        self.inner.verify_tls12_signature(message, cert, dss)
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, RustlsError> {
+        self.inner.verify_tls13_signature(message, cert, dss)
+    }
+
+    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
+        self.inner.supported_verify_schemes()
+    }
+}
+
 /// mTLS Configuration
 #[derive(Debug, Clone)]
 pub struct MtlsConfig {
@@ -71,12 +180,30 @@ impl MtlsMiddleware {
         })
     }
 
-    /// Build rustls server configuration with client certificate verification
-    pub fn build_rustls_config(&self) -> Result<Arc<ServerConfig>, MtlsError> {
-        let client_verifier = WebPkiClientVerifier::builder(self.cert_store.clone())
+    /// Build rustls server configuration with client certificate verification.
+    ///
+    /// When `crl_state` is provided and the CRL is available, wraps the
+    /// WebPkiClientVerifier with CrlAwareVerifier for revocation checking.
+    /// When CRL is missing/degraded, falls back to WebPKI-only verification.
+    pub fn build_rustls_config(
+        &self,
+        crl_state: Option<SharedCrlState>,
+    ) -> Result<Arc<ServerConfig>, MtlsError> {
+        let webpki_verifier = WebPkiClientVerifier::builder(self.cert_store.clone())
             .build()
             .map_err(|e| MtlsError::ClientVerifierError(e.to_string()))?;
 
+        let client_verifier: Arc<dyn ClientCertVerifier> = match crl_state {
+            Some(state) => {
+                info!("CRL-aware client verification enabled");
+                Arc::new(CrlAwareVerifier::new(webpki_verifier, state))
+            }
+            None => {
+                info!("No CRL state provided -- using WebPKI-only client verification");
+                webpki_verifier
+            }
+        };
+
         let server_cert = load_certs(&self.config.server_cert_path)?;
         let server_key = load_private_key(&self.config.server_key_path)?;
 

src/config/loader.rs

@@ -35,6 +35,14 @@ pub struct TlsConfig {
     pub server_key: String,
     #[serde(default = "default_tls_version")]
     pub min_tls_version: String,
+    /// Path to persist the CRL fetched from the manager.
+    /// Defaults to /etc/linux_patch_api/certs/crl.pem
+    #[serde(default = "default_crl_path")]
+    pub crl_path: String,
+}
+
+fn default_crl_path() -> String {
+    "/etc/linux_patch_api/certs/crl.pem".to_string()
 }
 
 fn default_true() -> bool {

src/main.rs

@@ -27,6 +27,7 @@ use std::sync::Arc;
 use tracing::{error, info, warn};
 
 use linux_patch_api::api::{configure_api_routes, configure_health_route};
+use linux_patch_api::auth::crl::{self, CrlStatus};
 use linux_patch_api::auth::{mtls, MtlsMiddleware, WhitelistManager};
 use linux_patch_api::config::loader::{validate_certs, CertStatus};
 use linux_patch_api::enroll;
@@ -297,6 +298,10 @@ async fn main() -> Result<()> {
     let cache_state = web::Data::new(PackageCacheState::new());
     info!("Package cache state initialized");
 
+    // Initialize shared CRL state (available even when TLS is off for health reporting)
+    let shared_crl_state = crl::new_shared_state();
+    let crl_state_data = web::Data::new(shared_crl_state.clone());
+
     // Configure bind address
     let bind_address = format!("{}:{}", config.server.bind, config.server.port);
 
@@ -306,7 +311,8 @@ async fn main() -> Result<()> {
             .wrap(Logger::default())
             .app_data(job_manager_data.clone())
             .app_data(backend_data.clone())
-            .app_data(cache_state.clone());
+            .app_data(cache_state.clone())
+            .app_data(crl_state_data.clone());
 
         // Configure API routes
         app = app.configure(|cfg| {
@@ -345,6 +351,7 @@ async fn main() -> Result<()> {
             server_cert = %tls_config.server_cert,
             server_key = %tls_config.server_key,
             min_tls_version = %tls_config.min_tls_version,
+            crl_path = %tls_config.crl_path,
             "Initializing mTLS authentication with TLS binding"
         );
 
@@ -355,11 +362,50 @@ async fn main() -> Result<()> {
             min_tls_version: tls_config.min_tls_version.clone(),
         };
 
+        // Load CRL from disk into the shared CRL state
+        let crl_path = std::path::PathBuf::from(&tls_config.crl_path);
+        let ca_cert_der = std::fs::read(&tls_config.ca_cert).unwrap_or_default();
+
+        // Load initial CRL from disk (missing is OK -- degraded mode)
+        let initial_crl = crl::load_crl(&crl_path, &ca_cert_der);
+        match initial_crl.status {
+            CrlStatus::Invalid => {
+                error!("CRL signature is invalid -- refusing to start (fail-closed)");
+                std::process::exit(ExitCode::Error as i32);
+            }
+            CrlStatus::Valid | CrlStatus::Expired => {
+                info!(
+                    status = %initial_crl.status,
+                    revoked = initial_crl.revoked_serials.len(),
+                    "CRL loaded from disk"
+                );
+                shared_crl_state.store(std::sync::Arc::new(initial_crl));
+            }
+            CrlStatus::Missing => {
+                info!("No CRL on disk -- starting in WebPKI-only mode");
+            }
+            CrlStatus::Degraded => {
+                warn!("CRL load failed -- starting in degraded (WebPKI-only) mode");
+            }
+        }
+
+        // Spawn CRL refresh background task if manager URL is configured
+        if let Some(manager_url) = config.enrollment_manager_url() {
+            crl::spawn_crl_refresh_task(
+                manager_url.to_string(),
+                crl_path,
+                ca_cert_der,
+                shared_crl_state.clone(),
+            );
+        } else {
+            info!("No manager URL configured -- CRL auto-refresh disabled");
+        }
+
         match MtlsMiddleware::new(mtls_config.clone()) {
             Ok(middleware) => {
-                // Build rustls server configuration
+                // Build rustls server configuration with CRL-aware verifier
                 let rustls_config = middleware
-                    .build_rustls_config()
+                    .build_rustls_config(Some(shared_crl_state.clone()))
                     .map_err(|e| anyhow::anyhow!("Failed to build rustls config: {}", e))?;
 
                 info!("mTLS middleware and rustls config initialized successfully");