Synchronize reads and writes in Spiffe SVID Manager

Signed-off-by: Max Lambrecht <maxlambrecht@gmail.com>

src/main/java/spiffe/api/svid/X509SVIDFetcher.java

@@ -69,7 +69,7 @@ public final class X509SVIDFetcher implements Fetcher<List<X509SVID>> {
         StreamObserver<X509SVIDResponse> observer = new StreamObserver<X509SVIDResponse>() {
             @Override
             public void onNext(X509SVIDResponse value) {
-                LOGGER.log(Level.INFO, "New SVID received ");
+                LOGGER.log(Level.FINE, "New SVID received ");
                 listener.accept(value.getSvidsList());
                 retryHandler.reset();
             }

src/main/java/spiffe/provider/FunctionalReadWriteLock.java

@@ -0,0 +1,31 @@
+package spiffe.provider;
+
+import java.util.concurrent.locks.StampedLock;
+import java.util.function.Supplier;
+
+public class FunctionalReadWriteLock {
+
+    private final StampedLock lock;
+
+    public FunctionalReadWriteLock() {
+        this.lock = new StampedLock();
+    }
+
+    public <T> T read(Supplier<T> supplier) {
+        long stamp = lock.readLock();
+        try {
+            return supplier.get();
+        } finally {
+            lock.unlockRead(stamp);
+        }
+    }
+
+    public void write(Runnable runnable) {
+        long stamp = lock.writeLock();
+        try {
+            runnable.run();
+        } finally {
+            lock.unlockWrite(stamp);
+        }
+    }
+}

src/main/java/spiffe/provider/SpiffeIdManager.java

@@ -8,7 +8,6 @@ import java.security.PrivateKey;
 import java.security.cert.X509Certificate;
 import java.util.List;
 import java.util.Set;
-import java.util.function.Consumer;
 
 import static java.util.Collections.EMPTY_SET;
 
@@ -26,8 +25,16 @@ class SpiffeIdManager {
         return INSTANCE;
     }
 
+    /**
+     * The Spiffe SVID handled by this manager
+     */
     private SpiffeSVID spiffeSVID;
 
+    /**
+     * Used to synchronize spiffeSVID writes and reads
+     */
+    private final FunctionalReadWriteLock guard;
+
     /**
      * Private Constructor
      *
@@ -35,33 +42,30 @@ class SpiffeIdManager {
      *
      */
     private SpiffeIdManager() {
-        Consumer<List<X509SVID>> certificateUpdater = certs -> {
+        guard = new FunctionalReadWriteLock();
-            X509SVID svid  = certs.get(0);
-            spiffeSVID = new SpiffeSVID(svid);
-        };
         Fetcher<List<X509SVID>> svidFetcher = new X509SVIDFetcher();
-        svidFetcher.registerListener(certificateUpdater);
+        svidFetcher.registerListener(this::updateSVID);
+    }
+
+    /**
+     * Method used as callback that gets executed whenever an SVID update is pushed by the Workload API
+     * Uses a write lock to synchronize access to spiffeSVID
+     */
+    private void updateSVID(List<X509SVID> certs) {
+        X509SVID svid  = certs.get(0);
+        guard.write(() -> spiffeSVID = new SpiffeSVID(svid));
     }
 
     X509Certificate getCertificate() {
-        if (spiffeSVID != null) {
+        return guard.read(() -> spiffeSVID != null ? spiffeSVID.getCertificate() : null);
-            return spiffeSVID.getCertificate();
-        }
-        return null;
     }
 
     PrivateKey getPrivateKey() {
-        if (spiffeSVID != null) {
+        return guard.read(() -> spiffeSVID != null ? spiffeSVID.getPrivateKey() : null);
-            return spiffeSVID.getPrivateKey();
-        }
-        return null;
     }
 
     @SuppressWarnings("unchecked")
     Set<X509Certificate> getTrustedCerts() {
-        if (spiffeSVID != null) {
+        return guard.read(() -> spiffeSVID != null ? spiffeSVID.getBundle() : EMPTY_SET);
-            return spiffeSVID.getBundle();
-        }
-        return EMPTY_SET;
     }
 }

src/main/java/spiffe/provider/SpiffeTrustManager.java

@@ -15,7 +15,6 @@ import static spiffe.provider.CertificateUtils.validate;
  */
 public class SpiffeTrustManager extends X509ExtendedTrustManager {
 
-
     private final SpiffeIdManager spiffeIdManager;
 
     SpiffeTrustManager() {
@@ -85,7 +84,7 @@ public class SpiffeTrustManager extends X509ExtendedTrustManager {
      *
      * @param chain an array of X509Certificate that contains the Peer's SVID to be validated
      * @throws CertificateException when either the Peer's certificate doesn't chain to any Trusted CA
-     * or the SPIFFE ID is not authorized.
+     *
      */
     private void checkPeer(X509Certificate[] chain) throws CertificateException {
         validate(chain, spiffeIdManager.getTrustedCerts());