# Copyright 2015 Google, Inc. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. require "faraday" require "googleauth/signet" require "memoist" module Google # Module Auth provides classes that provide Google-specific authorization # used to access Google APIs. module Auth NO_METADATA_SERVER_ERROR = <<~ERROR.freeze Error code 404 trying to get security access token from Compute Engine metadata for the default service account. This may be because the virtual machine instance does not have permission scopes specified. ERROR UNEXPECTED_ERROR_SUFFIX = <<~ERROR.freeze trying to get security access token from Compute Engine metadata for the default service account ERROR # Extends Signet::OAuth2::Client so that the auth token is obtained from # the GCE metadata server. class GCECredentials < Signet::OAuth2::Client # The IP Address is used in the URIs to speed up failures on non-GCE # systems. DEFAULT_METADATA_HOST = "169.254.169.254".freeze # @private Unused and deprecated COMPUTE_AUTH_TOKEN_URI = "http://169.254.169.254/computeMetadata/v1/instance/service-accounts/default/token".freeze # @private Unused and deprecated COMPUTE_ID_TOKEN_URI = "http://169.254.169.254/computeMetadata/v1/instance/service-accounts/default/identity".freeze # @private Unused and deprecated COMPUTE_CHECK_URI = "http://169.254.169.254".freeze class << self extend Memoist def metadata_host ENV.fetch "GCE_METADATA_HOST", DEFAULT_METADATA_HOST end def compute_check_uri "http://#{metadata_host}".freeze end def compute_auth_token_uri "#{compute_check_uri}/computeMetadata/v1/instance/service-accounts/default/token".freeze end def compute_id_token_uri "#{compute_check_uri}/computeMetadata/v1/instance/service-accounts/default/identity".freeze end # Detect if this appear to be a GCE instance, by checking if metadata # is available. def on_gce? options = {} # TODO: This should use google-cloud-env instead. c = options[:connection] || Faraday.default_connection headers = { "Metadata-Flavor" => "Google" } resp = c.get compute_check_uri, nil, headers do |req| req.options.timeout = 1.0 req.options.open_timeout = 0.1 end return false unless resp.status == 200 resp.headers["Metadata-Flavor"] == "Google" rescue Faraday::TimeoutError, Faraday::ConnectionFailed false end memoize :on_gce? end # Overrides the super class method to change how access tokens are # fetched. def fetch_access_token options = {} c = options[:connection] || Faraday.default_connection retry_with_error do uri = target_audience ? GCECredentials.compute_id_token_uri : GCECredentials.compute_auth_token_uri query = target_audience ? { "audience" => target_audience, "format" => "full" } : {} query[:scopes] = Array(scope).join "," if scope resp = c.get uri, query, "Metadata-Flavor" => "Google" case resp.status when 200 content_type = resp.headers["content-type"] if ["text/html", "application/text"].include? content_type { (target_audience ? "id_token" : "access_token") => resp.body } else Signet::OAuth2.parse_credentials resp.body, content_type end when 403, 500 msg = "Unexpected error code #{resp.status} #{UNEXPECTED_ERROR_SUFFIX}" raise Signet::UnexpectedStatusError, msg when 404 raise Signet::AuthorizationError, NO_METADATA_SERVER_ERROR else msg = "Unexpected error code #{resp.status} #{UNEXPECTED_ERROR_SUFFIX}" raise Signet::AuthorizationError, msg end end end end end end