1 files changed, 64 insertions, 0 deletions
diff --git a/lib/gitlab/config/loader/multi_doc_yaml.rb b/lib/gitlab/config/loader/multi_doc_yaml.rb
new file mode 100644
index 00000000000..346adc79896
--- /dev/null
+++ b/lib/gitlab/config/loader/multi_doc_yaml.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Config
+    module Loader
+      class MultiDocYaml
+        TooManyDocumentsError = Class.new(Loader::FormatError)
+        DataTooLargeError = Class.new(Loader::FormatError)
+        NotHashError = Class.new(Loader::FormatError)
+
+        MULTI_DOC_DIVIDER = /^---$/.freeze
+
+        def initialize(config, max_documents:, additional_permitted_classes: [])
+          @max_documents = max_documents
+          @safe_config = load_config(config, additional_permitted_classes)
+        end
+
+        def load!
+          raise TooManyDocumentsError, 'The parsed YAML has too many documents' if too_many_documents?
+          raise DataTooLargeError, 'The parsed YAML is too big' if too_big?
+          raise NotHashError, 'Invalid configuration format' unless all_hashes?
+
+          safe_config.map(&:deep_symbolize_keys)
+        end
+
+        private
+
+        attr_reader :safe_config, :max_documents
+
+        def load_config(config, additional_permitted_classes)
+          config.split(MULTI_DOC_DIVIDER).filter_map do |document|
+            YAML.safe_load(document,
+              permitted_classes: [Symbol, *additional_permitted_classes],
+              permitted_symbols: [],
+              aliases: true
+            )
+          end
+        rescue Psych::Exception => e
+          raise Loader::FormatError, e.message
+        end
+
+        def all_hashes?
+          safe_config.all?(Hash)
+        end
+
+        def too_many_documents?
+          safe_config.count > max_documents
+        end
+
+        def too_big?
+          !deep_sizes.all?(&:valid?)
+        end
+
+        def deep_sizes
+          safe_config.map do |config|
+            Gitlab::Utils::DeepSize.new(config,
+              max_size: Gitlab::CurrentSettings.current_application_settings.max_yaml_size_bytes,
+              max_depth: Gitlab::CurrentSettings.current_application_settings.max_yaml_depth)
+          end
+        end
+      end
+    end
+  end
+end