xds: implement requireClientCertificate semantics

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

@@ -234,9 +234,7 @@ private void updateSslContext() {
                 tlsCertificate.hasPassword()
                     ? tlsCertificate.getPassword().getInlineString()
                     : null);
-        if (localCertValidationContext != null) {
-          sslContextBuilder.trustManager(new SdsTrustManagerFactory(localCertValidationContext));
-        }
+        setClientAuthValues(sslContextBuilder, localCertValidationContext);
       } else {
         logger.log(Level.FINEST, "for client");
         sslContextBuilder =

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

@@ -205,9 +205,7 @@ SslContext buildSslContextFromSecrets()
       sslContextBuilder =
           GrpcSslContexts.forServer(
               new File(certificateChain), new File(privateKey), privateKeyPassword);
-      if (certContext != null) {
-        sslContextBuilder.trustManager(new SdsTrustManagerFactory(certContext));
-      }
+      setClientAuthValues(sslContextBuilder, certContext);
     } else {
       sslContextBuilder =
           GrpcSslContexts.forClient().trustManager(new SdsTrustManagerFactory(certContext));

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

@@ -16,12 +16,21 @@
 
 package io.grpc.xds.internal.sds;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkState;
 
+import io.envoyproxy.envoy.api.v2.auth.CertificateValidationContext;
 import io.envoyproxy.envoy.api.v2.auth.CommonTlsContext;
 import io.envoyproxy.envoy.api.v2.auth.DownstreamTlsContext;
 import io.envoyproxy.envoy.api.v2.auth.UpstreamTlsContext;
+import io.grpc.xds.internal.sds.trust.SdsTrustManagerFactory;
+import io.netty.handler.ssl.ClientAuth;
 import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import java.io.IOException;
+import java.security.cert.CertStoreException;
+import java.security.cert.CertificateException;
 import java.util.concurrent.Executor;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -32,6 +41,8 @@
  * stream that is receiving the requested secret(s) or it could represent file-system based
  * secret(s) that are dynamic.
  */
+// TODO(sanjaypujare): replace generic K with DownstreamTlsContext & UpstreamTlsContext in
+// separate client&server classes
 public abstract class SslContextProvider<K> {
 
   private static final Logger logger = Logger.getLogger(SslContextProvider.class.getName());
@@ -48,7 +59,11 @@ public interface Callback {
   }
 
   protected SslContextProvider(K source, boolean server) {
-    checkNotNull(source, "source");
+    if (server) {
+      checkArgument(source instanceof DownstreamTlsContext, "expecting DownstreamTlsContext");
+    } else {
+      checkArgument(source instanceof UpstreamTlsContext, "expecting UpstreamTlsContext");
+    }
     this.source = source;
     this.server = server;
   }
@@ -66,6 +81,22 @@ CommonTlsContext getCommonTlsContext() {
     return null;
   }
 
+  protected void setClientAuthValues(
+      SslContextBuilder sslContextBuilder, CertificateValidationContext localCertValidationContext)
+      throws CertificateException, IOException, CertStoreException {
+    checkState(server, "server side SslContextProvider expected");
+    if (localCertValidationContext != null) {
+      sslContextBuilder.trustManager(new SdsTrustManagerFactory(localCertValidationContext));
+      DownstreamTlsContext downstreamTlsContext = (DownstreamTlsContext)getSource();
+      sslContextBuilder.clientAuth(
+          downstreamTlsContext.hasRequireClientCertificate()
+              ? ClientAuth.REQUIRE
+              : ClientAuth.OPTIONAL);
+    } else {
+      sslContextBuilder.clientAuth(ClientAuth.NONE);
+    }
+  }
+
   /** Closes this provider and releases any resources. */
   void close() {}
 

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

@@ -18,6 +18,8 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static io.grpc.xds.XdsClientWrapperForServerSdsTest.buildFilterChainMatch;
+import static io.grpc.xds.internal.sds.CommonTlsContextTestsUtil.BAD_CLIENT_KEY_FILE;
+import static io.grpc.xds.internal.sds.CommonTlsContextTestsUtil.BAD_CLIENT_PEM_FILE;
 import static io.grpc.xds.internal.sds.CommonTlsContextTestsUtil.BAD_SERVER_KEY_FILE;
 import static io.grpc.xds.internal.sds.CommonTlsContextTestsUtil.BAD_SERVER_PEM_FILE;
 import static io.grpc.xds.internal.sds.CommonTlsContextTestsUtil.CA_PEM_FILE;
@@ -103,6 +105,60 @@ public void tlsClientServer_noClientAuthentication() throws IOException, URISynt
     assertThat(unaryRpc(/* requestMessage= */ "buddy", blockingStub)).isEqualTo("Hello buddy");
   }
 
+  @Test
+  public void requireClientAuth_noClientCert_expectException()
+      throws IOException, URISyntaxException {
+    DownstreamTlsContext downstreamTlsContext =
+        CommonTlsContextTestsUtil.buildDownstreamTlsContextFromFilenamesWithClientCertRequired(
+            SERVER_1_KEY_FILE, SERVER_1_PEM_FILE, CA_PEM_FILE);
+    buildServerWithTlsContext(downstreamTlsContext);
+
+    // for TLS, client only uses trustCa
+    UpstreamTlsContext upstreamTlsContext =
+        CommonTlsContextTestsUtil.buildUpstreamTlsContextFromFilenames(
+            /* privateKey= */ null, /* certChain= */ null, CA_PEM_FILE);
+
+    SimpleServiceGrpc.SimpleServiceBlockingStub blockingStub =
+        getBlockingStub(upstreamTlsContext, /* overrideAuthority= */ "foo.test.google.fr");
+    try {
+      unaryRpc(/* requestMessage= */ "buddy", blockingStub);
+      fail("exception expected");
+    } catch (StatusRuntimeException sre) {
+      assertThat(sre).hasCauseThat().isInstanceOf(SSLHandshakeException.class);
+      assertThat(sre).hasCauseThat().hasMessageThat().contains("HANDSHAKE_FAILURE");
+    }
+  }
+
+  @Test
+  public void noClientAuth_sendBadClientCert_passes() throws IOException, URISyntaxException {
+    DownstreamTlsContext downstreamTlsContext =
+        CommonTlsContextTestsUtil.buildDownstreamTlsContextFromFilenames(
+            SERVER_1_KEY_FILE, SERVER_1_PEM_FILE, /* trustCa= */ null);
+    buildServerWithTlsContext(downstreamTlsContext);
+
+    UpstreamTlsContext upstreamTlsContext =
+        CommonTlsContextTestsUtil.buildUpstreamTlsContextFromFilenames(
+            BAD_CLIENT_KEY_FILE, BAD_CLIENT_PEM_FILE, CA_PEM_FILE);
+
+    SimpleServiceGrpc.SimpleServiceBlockingStub blockingStub =
+        getBlockingStub(upstreamTlsContext, /* overrideAuthority= */ "foo.test.google.fr");
+    assertThat(unaryRpc("buddy", blockingStub)).isEqualTo("Hello buddy");
+  }
+
+  @Test
+  public void mtls_badClientCert_expectException() throws IOException, URISyntaxException {
+    UpstreamTlsContext upstreamTlsContext =
+        CommonTlsContextTestsUtil.buildUpstreamTlsContextFromFilenames(
+            BAD_CLIENT_KEY_FILE, BAD_CLIENT_PEM_FILE, CA_PEM_FILE);
+    try {
+      XdsClient.ListenerWatcher unused = performMtlsTestAndGetListenerWatcher(upstreamTlsContext);
+      fail("exception expected");
+    } catch (StatusRuntimeException sre) {
+      assertThat(sre).hasCauseThat().isInstanceOf(SSLHandshakeException.class);
+      assertThat(sre).hasCauseThat().hasMessageThat().contains("HANDSHAKE_FAILURE");
+    }
+  }
+
   /** mTLS - client auth enabled. */
   @Test
   public void mtlsClientServer_withClientAuthentication() throws IOException, URISyntaxException {
@@ -178,7 +234,7 @@ public void mtlsClientServer_changeServerContext_expectException()
   private XdsClient.ListenerWatcher performMtlsTestAndGetListenerWatcher(
       UpstreamTlsContext upstreamTlsContext) throws IOException, URISyntaxException {
     DownstreamTlsContext downstreamTlsContext =
-        CommonTlsContextTestsUtil.buildDownstreamTlsContextFromFilenames(
+        CommonTlsContextTestsUtil.buildDownstreamTlsContextFromFilenamesWithClientCertRequired(
             SERVER_1_KEY_FILE, SERVER_1_PEM_FILE, CA_PEM_FILE);
 
     final XdsClientWrapperForServerSds xdsClientWrapperForServerSds =

xds/src/test/java/io/grpc/xds/internal/sds/CommonTlsContextTestsUtil.java

@@ -17,6 +17,7 @@
 package io.grpc.xds.internal.sds;
 
 import com.google.common.base.Strings;
+import com.google.protobuf.BoolValue;
 import io.envoyproxy.envoy.api.v2.auth.CertificateValidationContext;
 import io.envoyproxy.envoy.api.v2.auth.CommonTlsContext;
 import io.envoyproxy.envoy.api.v2.auth.CommonTlsContext.CombinedCertificateValidationContext;
@@ -134,12 +135,14 @@ static CommonTlsContext buildCommonTlsContextWithAdditionalValues(
     return builder.build();
   }
 
-  /**
-   * Helper method to build DownstreamTlsContext for multiple test classes.
-   */
-  static DownstreamTlsContext buildDownstreamTlsContext(CommonTlsContext commonTlsContext) {
+  /** Helper method to build DownstreamTlsContext for multiple test classes. */
+  static DownstreamTlsContext buildDownstreamTlsContext(
+      CommonTlsContext commonTlsContext, boolean requireClientCert) {
     DownstreamTlsContext downstreamTlsContext =
-        DownstreamTlsContext.newBuilder().setCommonTlsContext(commonTlsContext).build();
+        DownstreamTlsContext.newBuilder()
+            .setCommonTlsContext(commonTlsContext)
+            .setRequireClientCertificate(BoolValue.of(requireClientCert))
+            .build();
     return downstreamTlsContext;
   }
 
@@ -159,7 +162,8 @@ public static DownstreamTlsContext buildTestDownstreamTlsContext(
             "unix:/var/run/sds/uds_path",
             Arrays.asList("spiffe://grpc-sds-testing.svc.id.goog/ns/default/sa/bob"),
             Arrays.asList("managed-tls"),
-            null));
+            null),
+        /* requireClientCert= */ false);
   }
 
   static String getTempFileNameForResourcesFile(String resFile) throws IOException {
@@ -171,6 +175,27 @@ static String getTempFileNameForResourcesFile(String resFile) throws IOException
    */
   public static DownstreamTlsContext buildDownstreamTlsContextFromFilenames(
       @Nullable String privateKey, @Nullable String certChain, @Nullable String trustCa) {
+    return buildDownstreamTlsContextFromFilenamesWithClientAuth(privateKey, certChain, trustCa,
+        false);
+  }
+
+  /**
+   * Helper method to build DownstreamTlsContext for above tests. Called from other classes as well.
+   */
+  public static DownstreamTlsContext buildDownstreamTlsContextFromFilenamesWithClientCertRequired(
+      @Nullable String privateKey,
+      @Nullable String certChain,
+      @Nullable String trustCa) {
+
+    return buildDownstreamTlsContextFromFilenamesWithClientAuth(privateKey, certChain, trustCa,
+        true);
+  }
+
+  private static DownstreamTlsContext buildDownstreamTlsContextFromFilenamesWithClientAuth(
+      @Nullable String privateKey,
+      @Nullable String certChain,
+      @Nullable String trustCa,
+      boolean requireClientCert) {
     // get temp file for each file
     try {
       if (certChain != null) {
@@ -186,7 +211,7 @@ public static DownstreamTlsContext buildDownstreamTlsContextFromFilenames(
       throw new RuntimeException(ioe);
     }
     return buildDownstreamTlsContext(
-        buildCommonTlsContextFromFilenames(privateKey, certChain, trustCa));
+        buildCommonTlsContextFromFilenames(privateKey, certChain, trustCa), requireClientCert);
   }
 
   /**

xds/src/test/java/io/grpc/xds/internal/sds/SdsSslContextProviderTest.java

@@ -79,7 +79,8 @@ private SdsSslContextProvider<?> getSdsSslContextProvider(
 
     return server
         ? SdsSslContextProvider.getProviderForServer(
-            CommonTlsContextTestsUtil.buildDownstreamTlsContext(commonTlsContext),
+            CommonTlsContextTestsUtil.buildDownstreamTlsContext(
+                commonTlsContext, /* requireClientCert= */ false),
             node,
             MoreExecutors.directExecutor(),
             MoreExecutors.directExecutor())

xds/src/test/java/io/grpc/xds/internal/sds/SecretVolumeSslContextProviderTest.java

@@ -274,7 +274,8 @@ public void getProviderForServer_defaultTlsCertificate_throwsException() {
     try {
       SecretVolumeSslContextProvider.getProviderForServer(
           CommonTlsContextTestsUtil.buildDownstreamTlsContext(
-              CommonTlsContextTestsUtil.getCommonTlsContext(tlsCert, /* certContext= */ null)));
+              CommonTlsContextTestsUtil.getCommonTlsContext(tlsCert, /* certContext= */ null),
+              /* requireClientCert= */ false));
       Assert.fail("no exception thrown");
     } catch (IllegalArgumentException expected) {
       assertThat(expected).hasMessageThat().isEqualTo("filename expected");
@@ -295,7 +296,8 @@ public void getProviderForServer_certContextWithInlineString_throwsException() {
     try {
       SecretVolumeSslContextProvider.getProviderForServer(
           CommonTlsContextTestsUtil.buildDownstreamTlsContext(
-              CommonTlsContextTestsUtil.getCommonTlsContext(tlsCert, certContext)));
+              CommonTlsContextTestsUtil.getCommonTlsContext(tlsCert, certContext),
+              /* requireClientCert= */ false));
       Assert.fail("no exception thrown");
     } catch (IllegalArgumentException expected) {
       assertThat(expected.getMessage()).isEqualTo("filename expected");

xds/src/test/java/io/grpc/xds/internal/sds/ServerSslContextProviderFactoryTest.java

@@ -52,7 +52,8 @@ public void createSslContextProvider_sdsConfigForTlsCert_expectException() {
         CommonTlsContextTestsUtil.buildCommonTlsContextFromSdsConfigForTlsCertificate(
             "name", "unix:/tmp/sds/path", CA_PEM_FILE);
     DownstreamTlsContext downstreamTlsContext =
-        CommonTlsContextTestsUtil.buildDownstreamTlsContext(commonTlsContext);
+        CommonTlsContextTestsUtil.buildDownstreamTlsContext(
+            commonTlsContext, /* requireClientCert= */ false);
 
     try {
       SslContextProvider<DownstreamTlsContext> unused =
@@ -71,7 +72,8 @@ public void createSslContextProvider_sdsConfigForCertValidationContext_expectExc
         CommonTlsContextTestsUtil.buildCommonTlsContextFromSdsConfigForValidationContext(
             "name", "unix:/tmp/sds/path", SERVER_1_KEY_FILE, SERVER_1_PEM_FILE);
     DownstreamTlsContext downstreamTlsContext =
-        CommonTlsContextTestsUtil.buildDownstreamTlsContext(commonTlsContext);
+        CommonTlsContextTestsUtil.buildDownstreamTlsContext(
+            commonTlsContext, /* requireClientCert= */ false);
 
     try {
       SslContextProvider<DownstreamTlsContext> unused =