Refactoring: move the credentials load into its own class

lib/googleauth/credentials_loader.rb

@@ -0,0 +1,85 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+require 'memoist'
+require 'rbconfig'
+
+module Google
+  # Module Auth provides classes that provide Google-specific authorization
+  # used to access Google APIs.
+  module Auth
+    # CredentialsLoader contains the behaviour used to locate and find default
+    # credentials files on the file system.
+    module CredentialsLoader
+      extend Memoist
+      ENV_VAR = 'GOOGLE_APPLICATION_CREDENTIALS'
+      NOT_FOUND_ERROR =
+        "Unable to read the credential file specified by #{ENV_VAR}"
+      WELL_KNOWN_PATH = 'gcloud/application_default_credentials.json'
+      WELL_KNOWN_ERROR = 'Unable to read the default credential file'
+
+      # determines if the current OS is windows
+      def windows?
+        RbConfig::CONFIG['host_os'] =~ /Windows|mswin/
+      end
+      memoize :windows?
+
+      # Creates an instance from the path specified in an environment
+      # variable.
+      #
+      # @param scope [string|array] the scope(s) to access
+      def from_env(scope)
+        return nil unless ENV.key?(ENV_VAR)
+        path = ENV[ENV_VAR]
+        fail 'file #{path} does not exist' unless File.exist?(path)
+        File.open(path) do |f|
+          return new(scope, f)
+        end
+      rescue StandardError => e
+        raise "#{NOT_FOUND_ERROR}: #{e}"
+      end
+
+      # Creates an instance from a well known path.
+      #
+      # @param scope [string|array] the scope(s) to access
+      def from_well_known_path(scope)
+        home_var, base = windows? ? 'APPDATA' : 'HOME', WELL_KNOWN_PATH
+        root = ENV[home_var].nil? ? '' : ENV[home_var]
+        base = File.join('.config', base) unless windows?
+        path = File.join(root, base)
+        return nil unless File.exist?(path)
+        File.open(path) do |f|
+          return new(scope, f)
+        end
+      rescue StandardError => e
+        raise "#{WELL_KNOWN_ERROR}: #{e}"
+      end
+    end
+  end
+end

lib/googleauth/service_account.rb

@@ -28,18 +28,8 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 require 'googleauth/signet'
-require 'memoist'
+require 'googleauth/credentials_loader'
 require 'multi_json'
-require 'openssl'
-require 'rbconfig'
-
-# Reads the private key and client email fields from service account JSON key.
-def read_json_key(json_key_io)
-  json_key = MultiJson.load(json_key_io.read)
-  fail 'missing client_email' unless json_key.key?('client_email')
-  fail 'missing private_key' unless json_key.key?('private_key')
-  [json_key['private_key'], json_key['client_email']]
-end
 
 module Google
   # Module Auth provides classes that provide Google-specific authorization
@@ -53,52 +43,16 @@ module Google
     #
     # cf [Application Default Credentials](http://goo.gl/mkAHpZ)
     class ServiceAccountCredentials < Signet::OAuth2::Client
-      ENV_VAR = 'GOOGLE_APPLICATION_CREDENTIALS'
-      NOT_FOUND_ERROR =
-        "Unable to read the credential file specified by #{ENV_VAR}"
       TOKEN_CRED_URI = 'https://www.googleapis.com/oauth2/v3/token'
-      WELL_KNOWN_PATH = 'gcloud/application_default_credentials.json'
+      extend CredentialsLoader
-      WELL_KNOWN_ERROR = 'Unable to read the default credential file'
 
-      class << self
+      # Reads the private key and client email fields from the service account
-        extend Memoist
+      # JSON key.
-
+      def self.read_json_key(json_key_io)
-        # determines if the current OS is windows
+        json_key = MultiJson.load(json_key_io.read)
-        def windows?
+        fail 'missing client_email' unless json_key.key?('client_email')
-          RbConfig::CONFIG['host_os'] =~ /Windows|mswin/
+        fail 'missing private_key' unless json_key.key?('private_key')
-        end
+        [json_key['private_key'], json_key['client_email']]
-        memoize :windows?
-
-        # Creates an instance from the path specified in an environment
-        # variable.
-        #
-        # @param scope [string|array] the scope(s) to access
-        def from_env(scope)
-          return nil unless ENV.key?(ENV_VAR)
-          path = ENV[ENV_VAR]
-          fail 'file #{path} does not exist' unless File.exist?(path)
-          File.open(path) do |f|
-            return new(scope, f)
-          end
-        rescue StandardError => e
-          raise "#{NOT_FOUND_ERROR}: #{e}"
-        end
-
-        # Creates an instance from a well known path.
-        #
-        # @param scope [string|array] the scope(s) to access
-        def from_well_known_path(scope)
-          home_var, base = windows? ? 'APPDATA' : 'HOME', WELL_KNOWN_PATH
-          root = ENV[home_var].nil? ? '' : ENV[home_var]
-          base = File.join('.config', base) unless windows?
-          path = File.join(root, base)
-          return nil unless File.exist?(path)
-          File.open(path) do |f|
-            return new(scope, f)
-          end
-        rescue StandardError => e
-          raise "#{WELL_KNOWN_ERROR}: #{e}"
-        end
       end
 
       # Initializes a ServiceAccountCredentials.
@@ -106,9 +60,9 @@ module Google
       # @param scope [string|array] the scope(s) to access
       # @param json_key_io [IO] an IO from which the JSON key can be read
       def initialize(scope, json_key_io)
-        private_key, client_email = read_json_key(json_key_io)
+        private_key, client_email = self.class.read_json_key(json_key_io)
         super(token_credential_uri: TOKEN_CRED_URI,
-              audience: TOKEN_CRED_URI,  # TODO: confirm this
+              audience: TOKEN_CRED_URI,
               scope: scope,
               issuer: client_email,
               signing_key: OpenSSL::PKey::RSA.new(private_key))

spec/googleauth/get_application_default_spec.rb

@@ -38,7 +38,7 @@ require 'spec_helper'
 describe '#get_application_default' do
   before(:example) do
     @key = OpenSSL::PKey::RSA.new(2048)
-    @var_name = ServiceAccountCredentials::ENV_VAR
+    @var_name = CredentialsLoader::ENV_VAR
     @orig = ENV[@var_name]
     @home = ENV['HOME']
     @scope = 'https://www.googleapis.com/auth/userinfo.profile'
@@ -82,7 +82,7 @@ describe '#get_application_default' do
     ENV.delete(@var_name) unless ENV[@var_name].nil?
     Dir.mktmpdir do |dir|
       key_path = File.join(dir, '.config',
-                           ServiceAccountCredentials::WELL_KNOWN_PATH)
+                           CredentialsLoader::WELL_KNOWN_PATH)
       FileUtils.mkdir_p(File.dirname(key_path))
       File.write(key_path, cred_json_text)
       ENV['HOME'] = dir

spec/googleauth/service_account_spec.rb

@@ -42,6 +42,7 @@ require 'tmpdir'
 
 describe Google::Auth::ServiceAccountCredentials do
   ServiceAccountCredentials = Google::Auth::ServiceAccountCredentials
+  CredentialsLoader = Google::Auth::CredentialsLoader
 
   before(:example) do
     @key = OpenSSL::PKey::RSA.new(2048)
@@ -79,9 +80,10 @@ describe Google::Auth::ServiceAccountCredentials do
 
   describe '#from_env' do
     before(:example) do
-      @var_name = ServiceAccountCredentials::ENV_VAR
+      @var_name = CredentialsLoader::ENV_VAR
       @orig = ENV[@var_name]
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
+      @clz = ServiceAccountCredentials
     end
 
     after(:example) do
@@ -99,18 +101,17 @@ describe Google::Auth::ServiceAccountCredentials do
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, 'does-not-exist')
         ENV[@var_name] = key_path
-        expect { sac.from_env(@scope) }.to raise_error
+        expect { @clz.from_env(@scope) }.to raise_error
       end
     end
 
     it 'succeeds when the GOOGLE_APPLICATION_CREDENTIALS file is valid' do
-      sac = ServiceAccountCredentials  # shortens name
       Dir.mktmpdir do |dir|
         key_path = File.join(dir, 'my_cert_file')
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV[@var_name] = key_path
-        expect(sac.from_env(@scope)).to_not be_nil
+        expect(@clz.from_env(@scope)).to_not be_nil
       end
     end
   end
@@ -119,6 +120,8 @@ describe Google::Auth::ServiceAccountCredentials do
     before(:example) do
       @home = ENV['HOME']
       @scope = 'https://www.googleapis.com/auth/userinfo.profile'
+      @known_path = CredentialsLoader::WELL_KNOWN_PATH
+      @clz = ServiceAccountCredentials
     end
 
     after(:example) do
@@ -131,13 +134,12 @@ describe Google::Auth::ServiceAccountCredentials do
     end
 
     it 'successfully loads the file when it is present' do
-      sac = ServiceAccountCredentials  # shortens name
       Dir.mktmpdir do |dir|
-        key_path = File.join(dir, '.config', sac::WELL_KNOWN_PATH)
+        key_path = File.join(dir, '.config', @known_path)
         FileUtils.mkdir_p(File.dirname(key_path))
         File.write(key_path, cred_json_text)
         ENV['HOME'] = dir
-        expect(sac.from_well_known_path(@scope)).to_not be_nil
+        expect(@clz.from_well_known_path(@scope)).to_not be_nil
       end
     end
   end