Verify Google JWT tokens without Google libraries

2 files changed, 71 insertions, 17 deletions

diff --git a/src/main/java/com/github/scribejava/apis/GoogleTokenVerifier.java b/src/main/java/com/github/scribejava/apis/GoogleTokenVerifier.java
new file mode 100644
index 00000000..35a9d832
--- /dev/null
+++ b/src/main/java/com/github/scribejava/apis/GoogleTokenVerifier.java
@@ -0,0 +1,66 @@
+package com.github.scribejava.apis;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.text.ParseException;
+import java.util.Map;
+import java.util.Optional;
+
+import com.nimbusds.jose.JOSEException;
+import com.nimbusds.jose.JWSAlgorithm;
+import com.nimbusds.jose.jwk.source.JWKSource;
+import com.nimbusds.jose.jwk.source.RemoteJWKSet;
+import com.nimbusds.jose.proc.BadJOSEException;
+import com.nimbusds.jose.proc.JWSKeySelector;
+import com.nimbusds.jose.proc.JWSVerificationKeySelector;
+import com.nimbusds.jose.proc.SecurityContext;
+import com.nimbusds.jwt.proc.ConfigurableJWTProcessor;
+import com.nimbusds.jwt.proc.DefaultJWTClaimsVerifier;
+import com.nimbusds.jwt.proc.DefaultJWTProcessor;
+
+public class GoogleTokenVerifier {
+
+    public static Optional<String> validateToken(String idToken) {
+
+        // Create a JWT processor for the access tokens
+                ConfigurableJWTProcessor<SecurityContext> jwtProcessor =
+                        new DefaultJWTProcessor<>();
+        
+        // The public RSA keys to validate the signatures will be sourced from the
+        // OAuth 2.0 server's JWK set, published at a well-known URL. The RemoteJWKSet
+        // object caches the retrieved keys to speed up subsequent look-ups and can
+        // also handle key-rollover
+                JWKSource<SecurityContext> keySource =
+                        null;
+                try {
+                    keySource = new RemoteJWKSet<>(new URL("https://www.googleapis.com/oauth2/v3/certs"));
+                } catch (MalformedURLException e) {
+                    return Optional.empty();
+                }
+        
+        // The expected JWS algorithm of the access tokens (agreed out-of-band)
+                JWSAlgorithm expectedJWSAlg = JWSAlgorithm.RS256;
+        
+        // Configure the JWT processor with a key selector to feed matching public
+        // RSA keys sourced from the JWK set URL
+                JWSKeySelector<SecurityContext> keySelector =
+                        new JWSVerificationKeySelector<>(expectedJWSAlg, keySource);
+        
+                jwtProcessor.setJWSKeySelector(keySelector);
+        
+        // Set the required JWT claims for access tokens issued by the server
+                jwtProcessor.setJWTClaimsSetVerifier(new DefaultJWTClaimsVerifier<>());
+        
+        // Process the token
+                Map<String, Object> claimsSet;
+                try {
+                    claimsSet = jwtProcessor.process(idToken, null).toJSONObject();
+                } catch (BadJOSEException | JOSEException | ParseException e) {
+                    return Optional.empty();
+                }
+        
+                String email = (String)claimsSet.get("email");
+                boolean verified = claimsSet.get("email_verified").equals(true);
+                return verified ? Optional.of(email) : Optional.empty();
+            }    
+}
diff --git a/src/main/java/com/juick/www/api/ApiSocialLogin.java b/src/main/java/com/juick/www/api/ApiSocialLogin.java
index 43de04bb..e6116173 100644
--- a/src/main/java/com/juick/www/api/ApiSocialLogin.java
+++ b/src/main/java/com/juick/www/api/ApiSocialLogin.java
@@ -20,18 +20,13 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.scribejava.apis.AppleClientSecretGenerator;
 import com.github.scribejava.apis.AppleSignInApi;
 import com.github.scribejava.apis.FacebookApi;
+import com.github.scribejava.apis.GoogleTokenVerifier;
 import com.github.scribejava.apis.VkontakteApi;
 import com.github.scribejava.core.builder.ServiceBuilder;
 import com.github.scribejava.core.model.OAuth2AccessToken;
 import com.github.scribejava.core.model.OAuthRequest;
 import com.github.scribejava.core.model.Verb;
 import com.github.scribejava.core.oauth.OAuth20Service;
-import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
-import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
-import com.google.api.client.http.HttpTransport;
-import com.google.api.client.http.javanet.NetHttpTransport;
-import com.google.api.client.json.JsonFactory;
-import com.google.api.client.json.jackson2.JacksonFactory;
 import com.juick.model.AuthResponse;
 import com.juick.model.ext.facebook.User;
 import com.juick.model.ext.vk.UsersResponse;
@@ -58,8 +53,8 @@ import javax.annotation.PostConstruct;
 import javax.inject.Inject;
 import java.io.IOException;
 import java.security.GeneralSecurityException;
-import java.util.Collections;
 import java.util.Map;
+import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.ExecutionException;
 
@@ -109,18 +104,11 @@ public class ApiSocialLogin {
     @Inject
     private Users users;
 
-    private final HttpTransport transport = new NetHttpTransport();
-    private final JsonFactory jsonFactory = new JacksonFactory();
-    private GoogleIdTokenVerifier verifier;
-
     @PostConstruct
     public void init() {
         ServiceBuilder facebookBuilder = new ServiceBuilder(FACEBOOK_APPID);
         ServiceBuilder twitterBuilder = new ServiceBuilder(twitterConsumerKey);
         ServiceBuilder vkBuilder = new ServiceBuilder(VK_APPID);
-        verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory)
-                .setAudience(Collections.singletonList(googleClientId))
-                .build();
         facebookAuthService = facebookBuilder
                 .apiSecret(FACEBOOK_SECRET)
                 .callback(FACEBOOK_REDIRECT)
@@ -246,9 +234,9 @@ public class ApiSocialLogin {
             throws GeneralSecurityException, IOException {
         logger.info("Token: {}", idTokenString);
         logger.info("Client: {}", googleClientId);
-        GoogleIdToken idToken = verifier.verify(idTokenString);
-        if (idToken != null) {
-            String email = idToken.getPayload().getEmail();
+        Optional<String> verifiedEmail = GoogleTokenVerifier.validateToken(idTokenString);
+        if (verifiedEmail.isPresent()) {
+            String email = verifiedEmail.get();
             com.juick.model.User visitor = userService.getUserByEmail(email);
             if (visitor.isAnonymous()) {
                 String verificationCode = RandomStringUtils.randomAlphanumeric(8).toUpperCase();