Refactor

java/advanced/APIDemo/app/src/main/java/com/google/android/gms/example/apidemo/DFPPPIDFragment.java

@@ -26,6 +26,7 @@
 import android.widget.Toast;
 import com.google.android.gms.ads.doubleclick.PublisherAdRequest;
 import com.google.android.gms.ads.doubleclick.PublisherAdView;
+import com.google.security.annotations.SuppressInsecureCipherModeCheckerNoReview;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 
@@ -75,14 +76,15 @@ public void onClick(View view) {
         });
     }
 
-    // This is a simple method to generate a hash of a sample username to use as a PPID. It's being
-    // used here as a convenient stand-in for a true Publisher-Provided Identifier. In your own
-    // apps, you can decide for yourself how to generate the PPID value, though there are some
-    // restrictions on what the values can be. For details, see:
-    //
-    // https://support.google.com/dfp_premium/answer/2880055
+  // This is a simple method to generate a hash of a sample username to use as a PPID. It's being
+  // used here as a convenient stand-in for a true Publisher-Provided Identifier. In your own
+  // apps, you can decide for yourself how to generate the PPID value, though there are some
+  // restrictions on what the values can be. For details, see:
+  //
+  // https://support.google.com/dfp_premium/answer/2880055
 
-    private String generatePPID(String username) {
+  @SuppressInsecureCipherModeCheckerNoReview
+  private String generatePPID(String username) {
         StringBuilder ppid = new StringBuilder();
 
         try {

java/advanced/RewardedSSVExample/Dockerfile

@@ -0,0 +1,7 @@
+FROM openjdk:8-jdk-stretch
+
+RUN apt-get update --fix-missing
+RUN apt-get install -y vim
+COPY ./ /var/www
+WORKDIR /var/www
+EXPOSE 8080

java/advanced/RewardedSSVExample/README.md

@@ -0,0 +1,48 @@
+# Google AdMob Rewarded Ads Server Side Verification
+
+Server-side verification callbacks are URL requests, with query parameters
+expanded by Google, that are sent by Google to an external system to notify it
+that a user should be rewarded for interacting with a rewarded video ad.
+Rewarded video SSV (server-side verification) callbacks provide an extra layer
+of protection against spoofing of client-side callbacks to reward users.
+
+## Description
+
+This project is developed in Java spring-boot framework as an example to verify
+rewarded video SSV callbacks by using the Tink third-party cryptographic library
+to ensure that the query parameters in the callback are legitimate values.
+
+## How to use
+
+1.  Deploy this project on your preferred web service provider.
+2.  Follow the
+    [Set up and test server-sideverification](https://support.google.com/admob/answer/9603226)
+    instructions to create an ad unit and configure/test your server-side
+    verification endpoint.
+
+## Local Development
+
+To start with Java:
+
+1 `cd RewardedSSVExample` 2 `./gradlew bootRun`
+
+To start with Docker:
+
+`docker-compose up --build`
+
+## Local testing
+
+To test a signature and message, send a `GET` request to
+`localhost:8080/verify?<dataToVerify>&signature=<signature>&key_id=<key_id>`.
+
+A successful response looks like this:
+
+```
+{
+  "sig": "ME...Z1c",
+  "payload": "ad_network=54...55&ad_unit=12345678&reward_amount=10&reward_item=coins &timestamp=150777823&transaction_id=12...DEF&user_id=1234567",
+  "key_id": "1268887",
+  "verified": "true"
+}
+```
+

java/advanced/RewardedSSVExample/build.gradle

@@ -0,0 +1,31 @@
+plugins {
+    id 'org.springframework.boot' version '2.2.2.RELEASE'
+    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
+    id 'java'
+}
+
+group = 'com.example.rewardedssv'
+version = '1.0.0'
+sourceCompatibility = '1.8'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation 'com.vaadin.external.google:android-json:0.0.20131108.vaadin1'
+    implementation 'com.google.crypto.tink:tink-android:1.4.0-rc1'
+    // tag::actuator[]
+    implementation 'org.springframework.boot:spring-boot-starter-actuator'
+    // end::actuator[]
+    implementation 'org.springframework.boot:spring-boot-starter-web'
+    // tag::tests[]
+    testImplementation('org.springframework.boot:spring-boot-starter-test') {
+        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
+    }
+    // end::tests[]
+}
+
+test {
+    useJUnitPlatform()
+}

java/advanced/RewardedSSVExample/docker-compose.yml

@@ -0,0 +1,18 @@
+version: '3'
+
+services:
+  ssv:
+    image: ssv
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: ssv
+    ports:
+    - 8080:8080
+        volumes:
+          - .:/var/www
+    command: ./gradlew bootRun
+    networks: ['stack']
+networks:
+  stack:
+    driver: bridge

java/advanced/RewardedSSVExample/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Thu May 14 12:27:25 IST 2020
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.3-all.zip
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStorePath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME

java/advanced/RewardedSSVExample/pom.xml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.2.2.RELEASE</version>
+        <relativePath/> <!-- lookup parent from repository -->
+    </parent>
+    <groupId>com.example</groupId>
+    <artifactId>rewardedssv</artifactId>
+    <version>1.0.0</version>
+    <name>spring-boot</name>
+    <description>Demo project for Spring Boot</description>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <!-- tag::actuator[] -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-actuator</artifactId>
+        </dependency>
+        <!-- end::actuator[] -->
+
+        <!-- tag::tests[] -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.junit.vintage</groupId>
+                    <artifactId>junit-vintage-engine</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <!-- end::tests[] -->
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

java/advanced/RewardedSSVExample/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'rewarded-ssv'

java/advanced/RewardedSSVExample/src/main/java/com/example/rewardedssv/Application.java

@@ -0,0 +1,21 @@
+package com.example.rewardedssv;
+
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+
+/** Application entry point */
+@SpringBootApplication
+public class Application {
+
+  public static void main(String[] args) {
+    SpringApplication.run(Application.class, args);
+  }
+
+  @Bean
+  public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
+    return args -> {};
+  }
+}

java/advanced/RewardedSSVExample/src/main/java/com/example/rewardedssv/SSVController.java

@@ -0,0 +1,122 @@
+package com.example.rewardedssv;
+
+import com.google.crypto.tink.subtle.Base64;
+import com.google.crypto.tink.subtle.EcdsaVerifyJce;
+import com.google.crypto.tink.subtle.EllipticCurves;
+import com.google.crypto.tink.subtle.EllipticCurves.EcdsaEncoding;
+import com.google.crypto.tink.subtle.Enums.HashType;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.nio.charset.Charset;
+import java.security.GeneralSecurityException;
+import java.security.interfaces.ECPublicKey;
+import java.util.Enumeration;
+import java.util.HashMap;
+import java.util.Map;
+import javax.servlet.http.HttpServletRequest;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/** SSV REST Controller */
+@RestController
+public class SSVController {
+  private static final String SIGNATURE_PARAM_KEY = "signature";
+  private static final String KEY_ID_PARAM_KEY = "key_id";
+  private static final String REWARD_VERIFIER_KEYS_URL =
+      "https://www.gstatic.com/admob/reward/verifier-keys.json";
+
+  private static Map<Long, ECPublicKey> parsePublicKeysJson()
+      throws GeneralSecurityException, IOException, JSONException {
+    URL url = new URL(REWARD_VERIFIER_KEYS_URL);
+    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
+    connection.setRequestMethod("GET");
+    BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
+    String inputLine;
+    StringBuffer content = new StringBuffer();
+    while ((inputLine = reader.readLine()) != null) {
+      content.append(inputLine);
+    }
+    reader.close();
+    connection.disconnect();
+    String publicKeysJson = content.toString();
+    JSONArray keys = new JSONObject(publicKeysJson).getJSONArray("keys");
+    Map<Long, ECPublicKey> publicKeys = new HashMap<>();
+    for (int i = 0; i < keys.length(); i++) {
+      JSONObject key = keys.getJSONObject(i);
+      publicKeys.put(
+          key.getLong("keyId"),
+          EllipticCurves.getEcPublicKey(Base64.decode(key.getString("base64"))));
+    }
+    if (publicKeys.isEmpty()) {
+      throw new GeneralSecurityException("No trusted keys are available for this protocol version");
+    }
+    return publicKeys;
+  }
+
+  private void verify(final byte[] dataToVerify, Long keyId, final byte[] signature)
+      throws GeneralSecurityException {
+    try {
+      Map<Long, ECPublicKey> publicKeys = parsePublicKeysJson();
+      if (publicKeys.containsKey(keyId)) {
+        ECPublicKey publicKey = publicKeys.get(keyId);
+        EcdsaVerifyJce verifier = new EcdsaVerifyJce(publicKey, HashType.SHA256, EcdsaEncoding.DER);
+        verifier.verify(signature, dataToVerify);
+      } else {
+        throw new GeneralSecurityException(
+            String.format("Cannot find verifying key with key id: %s.", keyId));
+      }
+    } catch (JSONException exception) {
+      throw new GeneralSecurityException(exception);
+    } catch (IOException exception) {
+      throw new GeneralSecurityException(exception);
+    }
+  }
+
+  @GetMapping(value = "/verify")
+  public ResponseEntity<?> index(HttpServletRequest request) {
+
+    Enumeration enumeration = request.getParameterNames();
+    Map<String, String[]> parameters = request.getParameterMap();
+
+    Map<String, String> response = new HashMap<>();
+    if (!parameters.containsKey(KEY_ID_PARAM_KEY) || !parameters.containsKey(SIGNATURE_PARAM_KEY)) {
+      response.put("verified", Boolean.FALSE.toString());
+      response.put("error", "Missing key_id and/or signature parameters.");
+      return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);
+    }
+
+    Long keyId = Long.valueOf(parameters.get(KEY_ID_PARAM_KEY)[0]);
+    String signature = parameters.get(SIGNATURE_PARAM_KEY)[0];
+    String queryString = request.getQueryString();
+    /* The last two query parameters of rewarded video
+      SSV callbacks are always signature and key_id
+      https://developers.google.com/admob/android/rewarded-video-ssv#get_content_to_be_verified
+    */
+    byte[] payload =
+        queryString
+            .substring(0, queryString.indexOf(SIGNATURE_PARAM_KEY) - 1)
+            .getBytes(Charset.forName("UTF-8"));
+
+    response.put("payload", new String(payload));
+    response.put("key_id", keyId.toString());
+    response.put("sig", signature);
+    HttpStatus status = HttpStatus.OK;
+    try {
+      verify(payload, keyId, Base64.urlSafeDecode(signature));
+      response.put("verified", Boolean.TRUE.toString());
+    } catch (GeneralSecurityException exception) {
+      status = HttpStatus.BAD_REQUEST;
+      response.put("verified", Boolean.FALSE.toString());
+      response.put("error", exception.getMessage());
+    }
+    return new ResponseEntity<>(response, status);
+  }
+}