Class: Google::Auth::GCECredentials

Inherits:
Signet::OAuth2::Client show all
Extended by:
Memoist
Defined in:
lib/googleauth/compute_engine.rb

Overview

Extends Signet::OAuth2::Client so that the auth token is obtained from the GCE metadata server.

Constant Summary collapse

COMPUTE_AUTH_TOKEN_URI =

The IP Address is used in the URIs to speed up failures on non-GCE systems.

'http://169.254.169.254/computeMetadata/v1/'\
'instance/service-accounts/default/token'
COMPUTE_CHECK_URI = 
'http://169.254.169.254'

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Signet::OAuth2::Client

#apply, #apply!, #updater_proc

Class Method Details

.on_gce?(options = {}) ⇒ Boolean

Detect if this appear to be a GCE instance, by checking if metadata is available

Returns:

  • (Boolean) 


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# File 'lib/googleauth/compute_engine.rb', line 52

def on_gce?(options = {})
  c = options[:connection] || Faraday.default_connection
  resp = c.get(COMPUTE_CHECK_URI) do |req|
    # Comment from: oauth2client/client.py
    #
    # Note: the explicit `timeout` below is a workaround. The underlying
    # issue is that resolving an unknown host on some networks will take
    # 20-30 seconds; making this timeout short fixes the issue, but
    # could lead to false negatives in the event that we are on GCE, but
    # the metadata resolution was particularly slow. The latter case is
    # "unlikely".
    req.options.timeout = 0.1
  end
  return false unless resp.status == 200
  return false unless resp.headers.key?('Metadata-Flavor')
  return resp.headers['Metadata-Flavor'] == 'Google'
rescue Faraday::TimeoutError, Faraday::ConnectionFailed
  return false
end

Instance Method Details

#fetch_access_token(options = {}) ⇒ Object

Overrides the super class method to change how access tokens are fetched.



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# File 'lib/googleauth/compute_engine.rb', line 77

def fetch_access_token(options = {})
  c = options[:connection] || Faraday.default_connection
  c.headers = { 'Metadata-Flavor' => 'Google' }
  resp = c.get(COMPUTE_AUTH_TOKEN_URI)
  Signet::OAuth2.parse_credentials(resp.body,
                                   resp.headers['content-type'])
end