xds: extend SslContextProviderSupplier to DowmstreamTlsContext for server side (#8146)

xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java

@@ -264,7 +264,7 @@ final class ClusterImplLoadBalancer extends LoadBalancer {
     private void updateSslContextProviderSupplier(@Nullable UpstreamTlsContext tlsContext) {
       UpstreamTlsContext currentTlsContext =
           sslContextProviderSupplier != null
-              ? sslContextProviderSupplier.getUpstreamTlsContext()
+              ? (UpstreamTlsContext)sslContextProviderSupplier.getTlsContext()
               : null;
       if (Objects.equals(currentTlsContext,  tlsContext)) {
         return;

xds/src/main/java/io/grpc/xds/internal/sds/SslContextProviderSupplier.java

@@ -19,31 +19,33 @@ package io.grpc.xds.internal.sds;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 
+import io.grpc.xds.EnvoyServerProtoData.BaseTlsContext;
+import io.grpc.xds.EnvoyServerProtoData.DownstreamTlsContext;
 import io.grpc.xds.EnvoyServerProtoData.UpstreamTlsContext;
 import io.netty.handler.ssl.SslContext;
 
 /**
- * Enables the CDS policy to initialize this object with the received {@link UpstreamTlsContext} &
- * communicate it to the consumer i.e. {@link SdsProtocolNegotiators.ClientSdsProtocolNegotiator}
+ * Enables Client or server side to initialize this object with the received {@link BaseTlsContext}
+ * and communicate it to the consumer i.e. {@link SdsProtocolNegotiators}
  * to lazily evaluate the {@link SslContextProvider}. The supplier prevents credentials leakage in
- * cases where the user is not using xDS credentials but the CDS policy contains a non-default
- * {@link UpstreamTlsContext}.
+ * cases where the user is not using xDS credentials but the client/server contains a non-default
+ * {@link BaseTlsContext}.
  */
 public final class SslContextProviderSupplier implements Closeable {
 
-  private final UpstreamTlsContext upstreamTlsContext;
+  private final BaseTlsContext tlsContext;
   private final TlsContextManager tlsContextManager;
   private SslContextProvider sslContextProvider;
   private boolean shutdown;
 
   public SslContextProviderSupplier(
-      UpstreamTlsContext upstreamTlsContext, TlsContextManager tlsContextManager) {
-    this.upstreamTlsContext = upstreamTlsContext;
+      BaseTlsContext tlsContext, TlsContextManager tlsContextManager) {
+    this.tlsContext = tlsContext;
     this.tlsContextManager = tlsContextManager;
   }
 
-  public UpstreamTlsContext getUpstreamTlsContext() {
-    return upstreamTlsContext;
+  public BaseTlsContext getTlsContext() {
+    return tlsContext;
   }
 
   /** Updates SslContext via the passed callback. */
@@ -51,34 +53,48 @@ public final class SslContextProviderSupplier implements Closeable {
     checkNotNull(callback, "callback");
     checkState(!shutdown, "Supplier is shutdown!");
     if (sslContextProvider == null) {
-      sslContextProvider =
-          tlsContextManager.findOrCreateClientSslContextProvider(upstreamTlsContext);
+      sslContextProvider = getSslContextProvider();
     }
     // we want to increment the ref-count so call findOrCreate again...
-    final SslContextProvider toRelease =
-        tlsContextManager.findOrCreateClientSslContextProvider(upstreamTlsContext);
+    final SslContextProvider toRelease = getSslContextProvider();
     sslContextProvider.addCallback(
         new SslContextProvider.Callback(callback.getExecutor()) {
 
           @Override
           public void updateSecret(SslContext sslContext) {
             callback.updateSecret(sslContext);
-            tlsContextManager.releaseClientSslContextProvider(toRelease);
+            releaseSslContextProvider(toRelease);
           }
 
           @Override
           public void onException(Throwable throwable) {
             callback.onException(throwable);
-            tlsContextManager.releaseClientSslContextProvider(toRelease);
+            releaseSslContextProvider(toRelease);
           }
         });
   }
 
-  /** Called by {@link io.grpc.xds.CdsLoadBalancer} when upstreamTlsContext changes. */
+  private void releaseSslContextProvider(SslContextProvider toRelease) {
+    if (tlsContext instanceof UpstreamTlsContext) {
+      tlsContextManager.releaseClientSslContextProvider(toRelease);
+    } else {
+      tlsContextManager.releaseServerSslContextProvider(toRelease);
+    }
+  }
+
+  private SslContextProvider getSslContextProvider() {
+    return tlsContext instanceof UpstreamTlsContext
+        ? tlsContextManager.findOrCreateClientSslContextProvider((UpstreamTlsContext) tlsContext)
+        : tlsContextManager.findOrCreateServerSslContextProvider((DownstreamTlsContext) tlsContext);
+  }
+
+  /** Called by consumer when tlsContext changes. */
   @Override
   public synchronized void close() {
-    if (sslContextProvider != null) {
+    if (tlsContext instanceof UpstreamTlsContext) {
       tlsContextManager.releaseClientSslContextProvider(sslContextProvider);
+    } else {
+      tlsContextManager.releaseServerSslContextProvider(sslContextProvider);
     }
     shutdown = true;
   }

xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java

@@ -520,7 +520,7 @@ public class ClusterImplLoadBalancerTest {
       SslContextProviderSupplier supplier =
           eag.getAttributes().get(InternalXdsAttributes.ATTR_SSL_CONTEXT_PROVIDER_SUPPLIER);
       if (enableSecurity) {
-        assertThat(supplier.getUpstreamTlsContext()).isEqualTo(upstreamTlsContext);
+        assertThat(supplier.getTlsContext()).isEqualTo(upstreamTlsContext);
       } else {
         assertThat(supplier).isNull();
       }
@@ -554,7 +554,7 @@ public class ClusterImplLoadBalancerTest {
       SslContextProviderSupplier supplier =
           eag.getAttributes().get(InternalXdsAttributes.ATTR_SSL_CONTEXT_PROVIDER_SUPPLIER);
       if (enableSecurity) {
-        assertThat(supplier.getUpstreamTlsContext()).isEqualTo(upstreamTlsContext);
+        assertThat(supplier.getTlsContext()).isEqualTo(upstreamTlsContext);
       } else {
         assertThat(supplier).isNull();
       }