Short-circuit credentials path check

Author: cacheflow

lib/fcm.rb

@@ -302,14 +302,21 @@ def credentials_error_msg(param)
     raise InvalidCredentialError, error_msg
   end
 
-  def filename_or_io_like?(path)
-    (path.is_a?(String) || path.respond_to?(:open)) && File.file?(path)
+  def open_json_key_path?(path)
+    valid_io_object = path.respond_to?(:open)
+    if valid_io_object && File.file?(path)
+      return true
+    end
+
+    max_path_len = 1024
+    valid_path = path.is_a?(String) && path.length <= max_path_len
+    valid_path && File.file?(path)
   end
 
   def json_key
     @json_key ||= if @json_key_path.respond_to?(:read)
                     @json_key_path
-                  elsif filename_or_io_like?(@json_key_path)
+                  elsif open_json_key_path?(@json_key_path)
                     File.open(@json_key_path)
                   else
                     credentials_error_msg(@json_key_path)

spec/fcm_spec.rb

@@ -24,6 +24,12 @@
     'c7f234d487c8%40developer.gserviceaccount.com'
   end
 
+  let(:large_file_name) do
+    1021.times.map do |el|
+      "a"
+    end.join('') + '.txt'
+  end
+
   let(:creds_error) do
     FCM::InvalidCredentialError
   end
@@ -33,7 +39,7 @@
       "type": 'service_account',
       "project_id": 'example',
       "private_key_id": 'c09c4593eee53707ca9f4208fbd6fe72b29fc7ab',
-      "private_key": OpenSSL::PKey::RSA.new(2048),
+      "private_key": OpenSSL::PKey::RSA.new(2048).to_s,
       "client_email": client_email,
       "client_id": 'acedc3c0a63b3562376386f0.apps.googleusercontent.com',
       "auth_uri": 'https://accounts.google.com/o/oauth2/auth',
@@ -62,6 +68,12 @@
       expect(fcm.__send__(:json_key).class).to eq(File)
     end
 
+    it 'raises an error when passed a large path' do
+      expect do 
+        FCM.new(large_file_name).__send__(:json_key)
+      end.to raise_error(creds_error)
+    end
+
     it 'can be an IO object' do
       fcm = FCM.new(StringIO.new('hey'))
       expect(fcm.__send__(:json_key).class).to eq(StringIO)