1 files changed, 62 insertions, 0 deletions
diff --git a/lib/gitlab/encoding_helper.rb b/lib/gitlab/encoding_helper.rb
new file mode 100644
index 00000000000..dbe28e6bb93
--- /dev/null
+++ b/lib/gitlab/encoding_helper.rb
@@ -0,0 +1,62 @@
+module Gitlab
+  module EncodingHelper
+    extend self
+
+    # This threshold is carefully tweaked to prevent usage of encodings detected
+    # by CharlockHolmes with low confidence. If CharlockHolmes confidence is low,
+    # we're better off sticking with utf8 encoding.
+    # Reason: git diff can return strings with invalid utf8 byte sequences if it
+    # truncates a diff in the middle of a multibyte character. In this case
+    # CharlockHolmes will try to guess the encoding and will likely suggest an
+    # obscure encoding with low confidence.
+    # There is a lot more info with this merge request:
+    # https://gitlab.com/gitlab-org/gitlab_git/merge_requests/77#note_4754193
+    ENCODING_CONFIDENCE_THRESHOLD = 40
+
+    def encode!(message)
+      return nil unless message.respond_to? :force_encoding
+
+      # if message is utf-8 encoding, just return it
+      message.force_encoding("UTF-8")
+      return message if message.valid_encoding?
+
+      # return message if message type is binary
+      detect = CharlockHolmes::EncodingDetector.detect(message)
+      return message.force_encoding("BINARY") if detect && detect[:type] == :binary
+
+      # force detected encoding if we have sufficient confidence.
+      if detect && detect[:encoding] && detect[:confidence] > ENCODING_CONFIDENCE_THRESHOLD
+        message.force_encoding(detect[:encoding])
+      end
+
+      # encode and clean the bad chars
+      message.replace clean(message)
+    rescue
+      encoding = detect ? detect[:encoding] : "unknown"
+      "--broken encoding: #{encoding}"
+    end
+
+    def encode_utf8(message)
+      detect = CharlockHolmes::EncodingDetector.detect(message)
+      if detect
+        begin
+          CharlockHolmes::Converter.convert(message, detect[:encoding], 'UTF-8')
+        rescue ArgumentError => e
+          Rails.logger.warn("Ignoring error converting #{detect[:encoding]} into UTF8: #{e.message}")
+
+          ''
+        end
+      else
+        clean(message)
+      end
+    end
+
+    private
+
+    def clean(message)
+      message.encode("UTF-16BE", undef: :replace, invalid: :replace, replace: "")
+        .encode("UTF-8")
+        .gsub("\0".encode("UTF-8"), "")
+    end
+  end
+end