Merge branch 'security-fp-prevent-billion-laughs-attack-12-0' into '12-0-stable'

Prevent Billion Laughs attack

See merge request gitlab/gitlabhq!3146

3 files changed, 112 insertions, 4 deletions

diff --git a/lib/gitlab/ci/config.rb b/lib/gitlab/ci/config.rb
index f187e456993..a7e4eb47dbb 100644
--- a/lib/gitlab/ci/config.rb
+++ b/lib/gitlab/ci/config.rb
@@ -15,6 +15,9 @@ module Gitlab
 
         @global = Entry::Global.new(@config)
         @global.compose!
+      rescue Gitlab::Config::Loader::Yaml::DataTooLargeError => e
+        Gitlab::Sentry.track_exception(e, extra: { user: user.inspect, project: project.inspect })
+        raise Config::ConfigError, e.message
       rescue Gitlab::Config::Loader::FormatError,
              Extendable::ExtensionError,
              External::Processor::IncludeError => e
diff --git a/lib/gitlab/config/loader/yaml.rb b/lib/gitlab/config/loader/yaml.rb
index 8159f8b8026..4cedab1545c 100644
--- a/lib/gitlab/config/loader/yaml.rb
+++ b/lib/gitlab/config/loader/yaml.rb
@@ -4,6 +4,13 @@ module Gitlab
   module Config
     module Loader
       class Yaml
+        DataTooLargeError = Class.new(Loader::FormatError)
+
+        include Gitlab::Utils::StrongMemoize
+
+        MAX_YAML_SIZE = 1.megabyte
+        MAX_YAML_DEPTH = 100
+
         def initialize(config)
           @config = YAML.safe_load(config, [Symbol], [], true)
         rescue Psych::Exception => e
@@ -11,16 +18,35 @@ module Gitlab
         end
 
         def valid?
-          @config.is_a?(Hash)
+          hash? && !too_big?
         end
 
         def load!
-          unless valid?
-            raise Loader::FormatError, 'Invalid configuration format'
-          end
+          raise DataTooLargeError, 'The parsed YAML is too big' if too_big?
+          raise Loader::FormatError, 'Invalid configuration format' unless hash?
 
           @config.deep_symbolize_keys
         end
+
+        private
+
+        def hash?
+          @config.is_a?(Hash)
+        end
+
+        def too_big?
+          return false unless Feature.enabled?(:ci_yaml_limit_size, default_enabled: true)
+
+          !deep_size.valid?
+        end
+
+        def deep_size
+          strong_memoize(:deep_size) do
+            Gitlab::Utils::DeepSize.new(@config,
+              max_size: MAX_YAML_SIZE,
+              max_depth: MAX_YAML_DEPTH)
+          end
+        end
       end
     end
   end
diff --git a/lib/gitlab/utils/deep_size.rb b/lib/gitlab/utils/deep_size.rb
new file mode 100644
index 00000000000..562cf09e249
--- /dev/null
+++ b/lib/gitlab/utils/deep_size.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+require 'objspace'
+
+module Gitlab
+  module Utils
+    class DeepSize
+      Error = Class.new(StandardError)
+      TooMuchDataError = Class.new(Error)
+
+      DEFAULT_MAX_SIZE = 1.megabyte
+      DEFAULT_MAX_DEPTH = 100
+
+      def initialize(root, max_size: DEFAULT_MAX_SIZE, max_depth: DEFAULT_MAX_DEPTH)
+        @root = root
+        @max_size = max_size
+        @max_depth = max_depth
+        @size = 0
+        @depth = 0
+
+        evaluate
+      end
+
+      def valid?
+        !too_big? && !too_deep?
+      end
+
+      private
+
+      def evaluate
+        add_object(@root)
+      rescue Error
+        # NOOP
+      end
+
+      def too_big?
+        @size > @max_size
+      end
+
+      def too_deep?
+        @depth > @max_depth
+      end
+
+      def add_object(object)
+        @size += ObjectSpace.memsize_of(object)
+        raise TooMuchDataError if @size > @max_size
+
+        add_array(object) if object.is_a?(Array)
+        add_hash(object) if object.is_a?(Hash)
+      end
+
+      def add_array(object)
+        with_nesting do
+          object.each do |n|
+            add_object(n)
+          end
+        end
+      end
+
+      def add_hash(object)
+        with_nesting do
+          object.each do |key, value|
+            add_object(key)
+            add_object(value)
+          end
+        end
+      end
+
+      def with_nesting
+        @depth += 1
+        raise TooMuchDataError if too_deep?
+
+        yield
+
+        @depth -= 1
+      end
+    end
+  end
+end