impersonated_credential.rb in googleauth-extras-0.3.0

- old
+ new
@@ -3,78 +3,150 @@
 module Google
   module Auth
     module Extras
       # This credential impersonates a service account.
       class ImpersonatedCredential < Signet::OAuth2::Client
-        class MissingScope < StandardError; end
+        include IdentityCredentialRefreshPatch
 
         # A credential that impersonates a service account.
         #
+        # The `email_address` of the service account to impersonate may be the exact
+        # same as the one represented in `base_credentials` for any desired situation
+        # but a handy usage is for going from and access token to an ID token (aka
+        # using `target_audience`).
+        #
         # @param base_credentials [Hash, String, Signet::OAuth2::Client]
         #   Credentials to use to impersonate the provided email address.
         #
         # @param delegate_email_addresses [String, Array<String>]
         #   The list of email address if there are intermediate service accounts that
         #   need to be impersonated using delegation.
         #
         # @param email_address [String]
         #   Email of the service account to impersonate.
         #
+        # @param include_email [Boolean]
+        #   Include the service account email in the token. If set to true, the token will
+        #   contain email and email_verified claims.
+        #   Only supported when using a target_audience.
+        #
         # @param lifetime [String]
         #   The desired lifetime (in seconds) of the token before needing to be refreshed.
         #   Defaults to 1h, adjust as needed given a refresh is automatically performed
         #   when the token less than 60s of remaining life and refresh requires an
         #   additional API call.
+        #   Only supported when not using a target_audience.
         #
         # @param scope [String, Array<String>]
         #   The OAuth 2 scopes to request. Can either be formatted as a comma seperated string or array.
+        #   Only supported when not using a target_audience.
         #
+        # @param target_audience [String]
+        #   The audience for the token, such as the API or account that this token grants access to.
+        #
         # @see https://cloud.google.com/iam/docs/reference/credentials/rest/v1/projects.serviceAccounts/generateAccessToken
+        # @see https://cloud.google.com/iam/docs/reference/credentials/rest/v1/projects.serviceAccounts/generateIdToken
         # @see https://cloud.google.com/iam/docs/create-short-lived-credentials-delegated#sa-credentials-permissions
+        # @see https://developers.google.com/identity/protocols/oauth2/scopes
         #
-        def initialize(email_address:, scope:, base_credentials: nil, delegate_email_addresses: nil, lifetime: nil)
-          super(scope: scope)
+        def initialize(
+          email_address:,
+          base_credentials: nil,
+          delegate_email_addresses: nil,
+          include_email: nil,
+          lifetime: nil,
+          scope: nil,
+          target_audience: nil
+        )
+          super(client_id: target_audience, scope: scope, target_audience: target_audience)
 
-          raise MissingScope if self.scope.nil? || self.scope.empty?
+          if self.target_audience.nil? || self.target_audience.empty?
+            raise(ArgumentError, 'Must provide scope or target_audience') if self.scope.nil? || self.scope.empty?
+          elsif self.scope.nil? || self.scope.empty?
+            # no-op
+          else
+            raise ArgumentError, 'Must provide scope or target_audience, not both'
+          end
 
           @iam_credentials_service = Google::Apis::IamcredentialsV1::IAMCredentialsService.new.tap do |ics|
             ics.authorization = base_credentials if base_credentials
           end
 
           @impersonate_delegates = Array(delegate_email_addresses).map do |email|
             transform_email_to_name(email)
           end
 
-          @impersonate_lifetime = lifetime
+          # This is true when target_audience is passed
+          if token_type == :id_token
+            @impersonate_include_email = include_email
+          elsif !include_email.nil?
+            raise ArgumentError, 'Can only provide include_email when using target_audience'
+          end
 
+          # This is true when scope is passed
+          if token_type == :access_token
+            @impersonate_lifetime = lifetime
+          elsif !lifetime.nil?
+            raise ArgumentError, 'Cannot provide lifetime when using target_audience'
+          end
+
           @impersonate_name = transform_email_to_name(email_address)
         end
 
         def fetch_access_token(*)
-          access_token_request = Google::Apis::IamcredentialsV1::GenerateAccessTokenRequest.new(
-            scope: scope,
-          )
+          token_request = if token_type == :id_token
+                            Google::Apis::IamcredentialsV1::GenerateIdTokenRequest.new(
+                              audience: target_audience,
+                            )
+                          else
+                            Google::Apis::IamcredentialsV1::GenerateAccessTokenRequest.new(
+                              scope: scope,
+                            )
+                          end
 
           # The Google SDK doesn't like nil repeated values, but be careful with others as well.
-          access_token_request.delegates = @impersonate_delegates unless @impersonate_delegates.empty?
-          access_token_request.lifetime = @impersonate_lifetime unless @impersonate_lifetime.nil?
+          token_request.delegates = @impersonate_delegates unless @impersonate_delegates.empty?
+          if token_type == :id_token
+            token_request.include_email = @impersonate_include_email unless @impersonate_include_email.nil?
+          else
+            token_request.lifetime = @impersonate_lifetime unless @impersonate_lifetime.nil?
+          end
 
-          access_token_response = @iam_credentials_service.generate_service_account_access_token(@impersonate_name, access_token_request)
+          if token_type == :id_token
+            id_token_response = @iam_credentials_service.generate_service_account_id_token(@impersonate_name, token_request)
 
-          {
-            access_token: access_token_response.access_token,
-            expires_at: DateTime.rfc3339(access_token_response.expire_time).to_time,
-          }
+            {
+              id_token: id_token_response.token,
+            }
+          else
+            access_token_response = @iam_credentials_service.generate_service_account_access_token(@impersonate_name, token_request)
+
+            {
+              access_token: access_token_response.access_token,
+              expires_at: DateTime.rfc3339(access_token_response.expire_time).to_time,
+            }
+          end
         end
 
         def inspect
-          "#<#{self.class.name}" \
-            " @access_token=#{@access_token ? '[REDACTED]' : 'nil'}" \
-            " @expires_at=#{expires_at.inspect}" \
-            " @impersonate_delegates=#{@impersonate_delegates.inspect}" \
-            " @impersonate_lifetime=#{@impersonate_lifetime.inspect}" \
-            " @impersonate_name=#{@impersonate_name.inspect}" \
-            '>'
+          if token_type == :id_token
+            "#<#{self.class.name}" \
+              " @expires_at=#{expires_at.inspect}" \
+              " @id_token=#{@id_token ? '[REDACTED]' : 'nil'}" \
+              " @impersonate_delegates=#{@impersonate_delegates.inspect}" \
+              " @impersonate_include_email=#{@impersonate_include_email.inspect}" \
+              " @impersonate_name=#{@impersonate_name.inspect}" \
+              " @target_audience=#{@target_audience.inspect}" \
+              '>'
+          else
+            "#<#{self.class.name}" \
+              " @access_token=#{@access_token ? '[REDACTED]' : 'nil'}" \
+              " @expires_at=#{expires_at.inspect}" \
+              " @impersonate_delegates=#{@impersonate_delegates.inspect}" \
+              " @impersonate_lifetime=#{@impersonate_lifetime.inspect}" \
+              " @impersonate_name=#{@impersonate_name.inspect}" \
+              '>'
+          end
         end
 
         private
 
         def transform_email_to_name(email)