class Google::Auth::ServiceAccountJwtHeaderCredentials

Authenticates requests using Google's Service Account credentials via JWT Header.

This class allows authorizing requests for service accounts directly from credentials from a json key file downloaded from the developer console (via 'Generate new Json Key'). It is not part of any OAuth2 flow, rather it creates a JWT and sends that as a credential.

cf [Application Default Credentials](goo.gl/mkAHpZ)

Constants

AUTH_METADATA_KEY
EXPIRY
JWT_AUD_URI_KEY
SIGNING_ALGORITHM
TOKEN_CRED_URI

Public Class Methods

make_creds(*args) click to toggle source

::make_creds proxies the construction of a credentials instance

::make_creds is used by the methods in CredentialsLoader.

By default, it calls new with 2 args, the second one being an optional scope. Here's the constructor only has one param, so we modify ::make_creds to reflect this.

# File lib/googleauth/service_account.rb, line 137
def self.make_creds(*args)
  new(json_key_io: args[0][:json_key_io])
end
new(options = {}) click to toggle source

Initializes a ServiceAccountJwtHeaderCredentials.

@param json_key_io [IO] an IO from which the JSON key can be read

# File lib/googleauth/service_account.rb, line 144
def initialize(options = {})
  json_key_io = options[:json_key_io]
  if json_key_io
    private_key, client_email = self.class.read_json_key(json_key_io)
  else
    private_key = ENV[CredentialsLoader::PRIVATE_KEY_VAR]
    client_email = ENV[CredentialsLoader::CLIENT_EMAIL_VAR]
  end
  @private_key = private_key
  @issuer = client_email
  @signing_key = OpenSSL::PKey::RSA.new(private_key)
end

Public Instance Methods

apply(a_hash, opts = {}) click to toggle source

Returns a clone of a_hash updated with the authoriation header

# File lib/googleauth/service_account.rb, line 170
def apply(a_hash, opts = {})
  a_copy = a_hash.clone
  apply!(a_copy, opts)
  a_copy
end
apply!(a_hash, opts = {}) click to toggle source

Construct a jwt token if the JWT_AUD_URI key is present in the input hash.

The jwt token is used as the value of a 'Bearer '.

# File lib/googleauth/service_account.rb, line 161
def apply!(a_hash, opts = {})
  jwt_aud_uri = a_hash.delete(JWT_AUD_URI_KEY)
  return a_hash if jwt_aud_uri.nil?
  jwt_token = new_jwt_token(jwt_aud_uri, opts)
  a_hash[AUTH_METADATA_KEY] = "Bearer #{jwt_token}"
  a_hash
end
updater_proc() click to toggle source

Returns a reference to the apply method, suitable for passing as a closure

# File lib/googleauth/service_account.rb, line 178
def updater_proc
  lambda(&method(:apply))
end

Protected Instance Methods

new_jwt_token(jwt_aud_uri, options = {}) click to toggle source

Creates a jwt uri token.

# File lib/googleauth/service_account.rb, line 185
def new_jwt_token(jwt_aud_uri, options = {})
  now = Time.new
  skew = options[:skew] || 60
  assertion = {
    'iss' => @issuer,
    'sub' => @issuer,
    'aud' => jwt_aud_uri,
    'exp' => (now + EXPIRY).to_i,
    'iat' => (now - skew).to_i
  }
  JWT.encode(assertion, @signing_key, SIGNING_ALGORITHM)
end