Fix X-GFE header search bug

The current code fails if there's no X-* header even if there is a X-GFE-*
header, although just having one of them should be enough.

Bug was introduced in []

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=166091723

javatests/google/registry/flows/TlsCredentialsTest.java

@@ -0,0 +1,66 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.flows;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import google.registry.request.HttpException.BadRequestException;
+import google.registry.testing.ExceptionRule;
+import javax.servlet.http.HttpServletRequest;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link TlsCredentials}. */
+@RunWith(JUnit4.class)
+public final class TlsCredentialsTest {
+
+  @Rule public final ExceptionRule thrown = new ExceptionRule();
+
+  @Test
+  public void testProvideClientCertificateHash() {
+    HttpServletRequest req = mock(HttpServletRequest.class);
+    when(req.getHeader("X-SSL-Certificate")).thenReturn("data");
+    assertThat(TlsCredentials.EppTlsModule.provideClientCertificateHash(req))
+        .isEqualTo("data");
+  }
+
+  @Test
+  public void testProvideClientCertificateHash_missing() {
+    thrown.expect(BadRequestException.class, "Missing header: X-SSL-Certificate");
+    HttpServletRequest req = mock(HttpServletRequest.class);
+    TlsCredentials.EppTlsModule.provideClientCertificateHash(req);
+  }
+
+  @Test
+  public void testProvideRequestedServername() {
+    HttpServletRequest req = mock(HttpServletRequest.class);
+    when(req.getHeader("X-Requested-Servername-SNI")).thenReturn("data");
+    assertThat(TlsCredentials.EppTlsModule.provideRequestedServername(req))
+        .isEqualTo("data");
+  }
+
+  @Test
+  public void testProvideRequestedServername_missing() {
+    thrown.expect(BadRequestException.class, "Missing header: X-Requested-Servername-SNI");
+    HttpServletRequest req = mock(HttpServletRequest.class);
+    TlsCredentials.EppTlsModule.provideRequestedServername(req);
+  }
+
+}