rls: use channel creds to create resolvingOobChannel

rls/src/main/java/io/grpc/rls/CachingRlsLbClient.java

@@ -139,8 +139,13 @@ final class CachingRlsLbClient {
             timeProvider);
     RlsRequestFactory requestFactory = new RlsRequestFactory(lbPolicyConfig.getRouteLookupConfig());
     rlsPicker = new RlsPicker(requestFactory);
-    ManagedChannelBuilder<?> rlsChannelBuilder =
-        helper.createResolvingOobChannelBuilder(rlsConfig.getLookupService());
+    // It is safe to use helper.getUnsafeChannelCredentials() because the client authenticates the
+    // RLS server using the same authority as the backends, even though the RLS server’s addresses
+    // will be looked up differently than the backends; overrideAuthority(helper.getAuthority()) is
+    // called to impose the authority security restrictions.
+    ManagedChannelBuilder<?> rlsChannelBuilder = helper.createResolvingOobChannelBuilder(
+        rlsConfig.getLookupService(), helper.getUnsafeChannelCredentials());
+    rlsChannelBuilder.overrideAuthority(helper.getAuthority());
     logger = helper.getChannelLogger();
     if (enableOobChannelDirectPath) {
       logger.log(

rls/src/test/java/io/grpc/rls/CachingRlsLbClientTest.java

@@ -34,6 +34,7 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.util.concurrent.SettableFuture;
 import io.grpc.Attributes;
 import io.grpc.CallOptions;
+import io.grpc.ChannelCredentials;
 import io.grpc.ChannelLogger;
 import io.grpc.ConnectivityState;
 import io.grpc.EquivalentAddressGroup;
@@ -536,7 +537,8 @@ public class CachingRlsLbClientTest {
   private final class FakeHelper extends Helper {
 
     @Override
-    public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(String target) {
+    public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(
+        String target, ChannelCredentials creds) {
       try {
         grpcCleanupRule.register(
             InProcessServerBuilder.forName(target)
@@ -579,7 +581,18 @@ public class CachingRlsLbClientTest {
 
     @Override
     public String getAuthority() {
-      throw new UnsupportedOperationException();
+      return DEFAULT_TARGET;
+    }
+
+    @Override
+    public ChannelCredentials getUnsafeChannelCredentials() {
+      // In test we don't do any authentication.
+      return new ChannelCredentials() {
+        @Override
+        public ChannelCredentials withoutBearerTokens() {
+          return this;
+        }
+      };
     }
 
     @Override

rls/src/test/java/io/grpc/rls/RlsLoadBalancerTest.java

@@ -32,6 +32,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import io.grpc.Attributes;
 import io.grpc.CallOptions;
+import io.grpc.ChannelCredentials;
 import io.grpc.ChannelLogger;
 import io.grpc.ConnectivityState;
 import io.grpc.ConnectivityStateInfo;
@@ -376,7 +377,7 @@ public class RlsLoadBalancerTest {
         .setAddresses(ImmutableList.of(new EquivalentAddressGroup(mock(SocketAddress.class))))
         .setLoadBalancingPolicyConfig(parsedConfigOrError.getConfig())
         .build());
-    verify(helper).createResolvingOobChannelBuilder(anyString());
+    verify(helper).createResolvingOobChannelBuilder(anyString(), any(ChannelCredentials.class));
   }
 
   @SuppressWarnings("unchecked")
@@ -429,7 +430,8 @@ public class RlsLoadBalancerTest {
     }
 
     @Override
-    public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(String target) {
+    public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(
+        String target, ChannelCredentials creds) {
       try {
         grpcCleanupRule.register(
             InProcessServerBuilder.forName(target)
@@ -475,6 +477,18 @@ public class RlsLoadBalancerTest {
       return "fake-bigtable.googleapis.com";
     }
 
+    @Override
+    public ChannelCredentials getUnsafeChannelCredentials() {
+      // In test we don't do any authentication.
+      return new ChannelCredentials() {
+        @Override
+        public ChannelCredentials withoutBearerTokens() {
+          return this;
+        }
+      };
+    }
+
+
     @Override
     public ScheduledExecutorService getScheduledExecutorService() {
       return fakeScheduledExecutorService;