Add sample for asserting identity to third-party services

appengine/appidentity/src/main/java/com/example/appengine/appidentity/SignForAppServlet.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2016 Google Inc. 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 com.example.appengine.appidentity;
+
+import com.google.appengine.api.appidentity.AppIdentityService;
+import com.google.appengine.api.appidentity.AppIdentityServiceFactory;
+import com.google.appengine.api.appidentity.PublicCertificate;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UnsupportedEncodingException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateException;
+import java.security.cert.CertificateFactory;
+import java.util.Arrays;
+import java.util.Collection;
+
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@SuppressWarnings("serial")
+public class SignForAppServlet extends HttpServlet {
+  private final AppIdentityService appIdentity;
+
+  public SignForAppServlet() {
+    appIdentity = AppIdentityServiceFactory.getAppIdentityService();
+  }
+
+  // [START asserting_identity_to_other_services]
+  // Note that the algorithm used by AppIdentity.signForApp() and
+  // getPublicCertificatesForApp() is "SHA256withRSA"
+
+  private byte[] signBlob(byte[] blob) {
+    AppIdentityService.SigningResult result = appIdentity.signForApp(blob);
+    return result.getSignature();
+  }
+
+  private byte[] getPublicCertificate() throws UnsupportedEncodingException {
+    Collection<PublicCertificate> certs = appIdentity.getPublicCertificatesForApp();
+    PublicCertificate publicCert = certs.iterator().next();
+    return publicCert.getX509CertificateInPemFormat().getBytes("UTF-8");
+  }
+
+  private Certificate parsePublicCertificate(byte[] publicCert)
+      throws CertificateException, NoSuchAlgorithmException {
+    InputStream stream = new ByteArrayInputStream(publicCert);
+    CertificateFactory cf = CertificateFactory.getInstance("X.509");
+    return cf.generateCertificate(stream);
+  }
+
+  private boolean verifySignature(byte[] blob, byte[] blobSignature, PublicKey pk)
+      throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
+    Signature signature = Signature.getInstance("SHA256withRSA");
+    signature.initVerify(pk);
+    signature.update(blob);
+    return signature.verify(blobSignature);
+  }
+
+  private String simulateIdentityAssertion()
+      throws CertificateException, UnsupportedEncodingException, NoSuchAlgorithmException,
+             InvalidKeyException, SignatureException {
+    // Simulate the sending app.
+    String message = "abcdefg";
+    byte[] blob = message.getBytes();
+    byte[] blobSignature = signBlob(blob);
+    byte[] publicCert = getPublicCertificate();
+
+    // Simulate the receiving app, which gets the certificate, blob, and signature.
+    Certificate cert = parsePublicCertificate(publicCert);
+    PublicKey pk = cert.getPublicKey();
+    boolean isValid = verifySignature(blob, blobSignature, pk);
+
+    return String.format(
+        "isValid=%b for message: %s\n\tsignature: %s\n\tpublic cert: %s",
+        isValid,
+        message,
+        Arrays.toString(blobSignature),
+        Arrays.toString(publicCert));
+  }
+  // [END asserting_identity_to_other_services]
+
+  @Override
+  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("text/plain");
+    try {
+      resp.getWriter().println(simulateIdentityAssertion());
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+}

appengine/appidentity/src/main/webapp/WEB-INF/web.xml

@@ -7,6 +7,10 @@
     <servlet-name>appidentity</servlet-name>
     <servlet-class>com.example.appengine.appidentity.IdentityServlet</servlet-class>
   </servlet>
+  <servlet>
+    <servlet-name>signforapp</servlet-name>
+    <servlet-class>com.example.appengine.appidentity.SignForAppServlet</servlet-class>
+  </servlet>
   <servlet>
     <servlet-name>urlshortener</servlet-name>
     <servlet-class>com.example.appengine.appidentity.UrlShortenerServlet</servlet-class>
@@ -15,6 +19,10 @@
     <servlet-name>appidentity</servlet-name>
     <url-pattern>/</url-pattern>
   </servlet-mapping>
+  <servlet-mapping>
+    <servlet-name>signforapp</servlet-name>
+    <url-pattern>/sign</url-pattern>
+  </servlet-mapping>
   <servlet-mapping>
     <servlet-name>urlshortener</servlet-name>
     <url-pattern>/shorten</url-pattern>

appengine/appidentity/src/test/java/com/example/appengine/appidentity/IdentityServletTest.java

@@ -1,4 +1,4 @@
-/**
+/*
  * Copyright 2015 Google Inc. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -13,25 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package com.example.appengine.appidentity;
 
 import static com.google.common.truth.Truth.assertThat;
-import static org.junit.Assert.fail;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
-import com.google.appengine.tools.development.ApiProxyLocal;
 import com.google.appengine.tools.development.testing.LocalServiceTestHelper;
-import com.google.apphosting.api.ApiProxy;
 import org.mockito.Mock;
-import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-import java.io.File;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 
@@ -62,6 +58,10 @@ public void setUp() throws Exception {
     servletUnderTest = new IdentityServlet();
   }
 
+  @After public void tearDown() {
+    helper.tearDown();
+  }
+
   @Test
   public void doGet_defaultEnvironment_writesResponse() throws Exception {
     servletUnderTest.doGet(mockRequest, mockResponse);

appengine/appidentity/src/test/java/com/example/appengine/appidentity/SignForAppServletTest.java

@@ -0,0 +1,69 @@
+/**
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * <p>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
+ *
+ * <p>http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * <p>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 com.example.appengine.appidentity;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.when;
+
+import com.google.appengine.tools.development.testing.LocalServiceTestHelper;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/** Unit tests for {@link SignForAppServlet}. */
+@RunWith(JUnit4.class)
+public class SignForAppServletTest {
+
+  private final LocalServiceTestHelper helper = new LocalServiceTestHelper();
+
+  @Mock private HttpServletRequest mockRequest;
+  @Mock private HttpServletResponse mockResponse;
+  private StringWriter responseWriter;
+  private SignForAppServlet servletUnderTest;
+
+  @Before public void setUp() throws Exception {
+    MockitoAnnotations.initMocks(this);
+    helper.setUp();
+
+    // Set up a fake HTTP response.
+    responseWriter = new StringWriter();
+    when(mockResponse.getWriter()).thenReturn(new PrintWriter(responseWriter));
+
+    servletUnderTest = new SignForAppServlet();
+  }
+
+  @After public void tearDown() {
+    helper.tearDown();
+  }
+
+  @Test public void doGet_defaultEnvironment_successfullyVerifiesSignature() throws Exception {
+    servletUnderTest.doGet(mockRequest, mockResponse);
+
+    assertThat(responseWriter.toString())
+        .named("SignForAppServlet response")
+        .contains("isValid=true for message: abcdefg");
+  }
+}