Add Google auth validation and fix the case where no config is specified at all for Google auth or Github auth

util/oauth.py

@@ -70,7 +70,7 @@ class GithubOAuthConfig(OAuthConfig):
     # First: Verify that the github endpoint is actually Github by checking for the
     # X-GitHub-Request-Id here.
     api_endpoint = self._api_endpoint()
-    result = http_client.get(api_endpoint, auth=(self.client_id(), self.client_secret()))
+    result = http_client.get(api_endpoint, auth=(self.client_id(), self.client_secret()), timeout=5)
     if not 'X-GitHub-Request-Id' in result.headers:
       raise Exception('Endpoint is not a Github (Enterprise) installation')
 
@@ -87,7 +87,8 @@ class GithubOAuthConfig(OAuthConfig):
     #   - If the {client_id, client_secret} pair is invalid in some way, we get a 401 error.
     #   - If the pair is valid, then we get a 404 because the 'foo' token does not exists.
     validate_endpoint = self._get_url(api_endpoint, 'applications/%s/tokens/foo' % self.client_id())
-    result = http_client.get(validate_endpoint, auth=(self.client_id(), self.client_secret()))
+    result = http_client.get(validate_endpoint, auth=(self.client_id(), self.client_secret()),
+                                                timeout=5)
     return result.status_code == 404
 
   def get_public_config(self):
@@ -116,8 +117,21 @@ class GoogleOAuthConfig(OAuthConfig):
     return 'https://www.googleapis.com/oauth2/v1/userinfo'
 
   def validate_client_id_and_secret(self, http_client):
-    # No validation supported at this time.
-    return None
+    # To verify the Google client ID and secret, we hit the
+    # https://www.googleapis.com/oauth2/v3/token endpoint with an invalid request. If the client
+    # ID or secret are invalid, we get returned a 403 Unauthorized. Otherwise, we get returned
+    # another response code.
+    url = 'https://www.googleapis.com/oauth2/v3/token'
+    data = {
+      'code': 'fakecode',
+      'client_id': self.client_id(),
+      'client_secret': self.client_secret(),
+      'grant_type': 'authorization_code',
+      'redirect_uri': 'http://example.com'
+    }
+
+    result = http_client.post(url, data=data, timeout=5)
+    return result.status_code != 401
 
   def get_public_config(self):
     return  {