1 files changed, 66 insertions, 0 deletions
diff --git a/lib/gitlab/middleware/compressed_json.rb b/lib/gitlab/middleware/compressed_json.rb
new file mode 100644
index 00000000000..ef6e0db5673
--- /dev/null
+++ b/lib/gitlab/middleware/compressed_json.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Middleware
+    class CompressedJson
+      COLLECTOR_PATH = '/api/v4/error_tracking/collector'
+      MAXIMUM_BODY_SIZE = 200.kilobytes.to_i
+
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        if compressed_et_request?(env)
+          input = extract(env['rack.input'])
+
+          if input.length > MAXIMUM_BODY_SIZE
+            return too_large
+          end
+
+          env.delete('HTTP_CONTENT_ENCODING')
+          env['CONTENT_LENGTH'] = input.length
+          env['rack.input'] = StringIO.new(input)
+        end
+
+        @app.call(env)
+      end
+
+      def compressed_et_request?(env)
+        post_request?(env) &&
+          gzip_encoding?(env) &&
+          match_content_type?(env) &&
+          match_path?(env)
+      end
+
+      def too_large
+        [413, { 'Content-Type' => 'text/plain' }, ['Payload Too Large']]
+      end
+
+      def relative_url
+        File.join('', Gitlab.config.gitlab.relative_url_root).chomp('/')
+      end
+
+      def extract(input)
+        Zlib::GzipReader.new(input).read(MAXIMUM_BODY_SIZE + 1)
+      end
+
+      def post_request?(env)
+        env['REQUEST_METHOD'] == 'POST'
+      end
+
+      def gzip_encoding?(env)
+        env['HTTP_CONTENT_ENCODING'] == 'gzip'
+      end
+
+      def match_content_type?(env)
+        env['CONTENT_TYPE'] == 'application/json' ||
+          env['CONTENT_TYPE'] == 'application/x-sentry-envelope'
+      end
+
+      def match_path?(env)
+        env['PATH_INFO'].start_with?((File.join(relative_url, COLLECTOR_PATH)))
+      end
+    end
+  end
+end