xds: honor requested_server_name from TLS SNI

xds/src/main/java/io/grpc/xds/internal/rbac/engine/GrpcAuthorizationEngine.java

@@ -41,8 +41,11 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
+import javax.net.ssl.ExtendedSSLSession;
 import javax.net.ssl.SSLPeerUnverifiedException;
 import javax.net.ssl.SSLSession;
+import javax.net.ssl.SNIHostName;
+import javax.net.ssl.SNIServerName;
 
 /**
  * Implementation of gRPC server access control based on envoy RBAC protocol:
@@ -411,6 +414,20 @@ private int getDestinationPort() {
     }
 
     private String getRequestedServerName() {
+      SSLSession sslSession = serverCall.getAttributes().get(Grpc.TRANSPORT_ATTR_SSL_SESSION);
+      if (!(sslSession instanceof ExtendedSSLSession)) {
+        return "";
+      }
+      List<SNIServerName> requestedServerNames =
+          ((ExtendedSSLSession) sslSession).getRequestedServerNames();
+      if (requestedServerNames == null) {
+        return "";
+      }
+      for (SNIServerName requestedServerName : requestedServerNames) {
+        if (requestedServerName instanceof SNIHostName) {
+          return ((SNIHostName) requestedServerName).getAsciiName();
+        }
+      }
       return "";
     }
   }

xds/src/test/java/io/grpc/xds/internal/rbac/engine/GrpcAuthorizationEngineTest.java

@@ -55,8 +55,10 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import javax.net.ssl.ExtendedSSLSession;
 import javax.net.ssl.SSLPeerUnverifiedException;
-import javax.net.ssl.SSLSession;
+import javax.net.ssl.SNIHostName;
+import javax.net.ssl.SNIServerName;
 import javax.security.auth.x500.X500Principal;
 import org.junit.Before;
 import org.junit.Rule;
@@ -85,12 +87,13 @@ public class GrpcAuthorizationEngineTest {
   @Mock
   private ServerCall<Void,Void> serverCall;
   @Mock
-  private SSLSession sslSession;
+  private ExtendedSSLSession sslSession;
 
   @Before
   public void setUp() throws Exception {
     X509Certificate[] certs = {TestUtils.loadX509Cert("server1.pem")};
     when(sslSession.getPeerCertificates()).thenReturn(certs);
+    when(sslSession.getRequestedServerNames()).thenReturn(Collections.<SNIServerName>emptyList());
     Attributes attributes = Attributes.newBuilder()
         .set(Grpc.TRANSPORT_ATTR_REMOTE_ADDR, new InetSocketAddress(IP_ADDR2, PORT))
         .set(Grpc.TRANSPORT_ATTR_LOCAL_ADDR, new InetSocketAddress(IP_ADDR1, PORT))
@@ -354,6 +357,24 @@ public void multiplePolicies() throws Exception {
     assertThat(decision.matchingPolicyName()).isEqualTo(POLICY_NAME);
   }
 
+  @Test
+  public void requestedServerNameMatcher_matchesTlsSni() {
+    when(sslSession.getRequestedServerNames()).thenReturn(
+        Collections.<SNIServerName>singletonList(new SNIHostName("blocked.example")));
+    GrpcAuthorizationEngine.RequestedServerNameMatcher requestedServerNameMatcher =
+        GrpcAuthorizationEngine.RequestedServerNameMatcher.create(
+            StringMatcher.forExact("blocked.example", false));
+    OrMatcher permission = OrMatcher.create(requestedServerNameMatcher);
+    OrMatcher principal = OrMatcher.create(AlwaysTrueMatcher.INSTANCE);
+    PolicyMatcher policyMatcher = PolicyMatcher.create("deny-sni", permission, principal);
+
+    GrpcAuthorizationEngine engine = new GrpcAuthorizationEngine(
+        AuthConfig.create(Collections.singletonList(policyMatcher), Action.DENY));
+    AuthDecision decision = engine.evaluate(new Metadata(), serverCall);
+    assertThat(decision.decision()).isEqualTo(Action.DENY);
+    assertThat(decision.matchingPolicyName()).isEqualTo("deny-sni");
+  }
+
   @Test
   public void matchersEqualHashcode() throws Exception {
     PathMatcher pathMatcher = PathMatcher.create(STRING_MATCHER);