1 files changed, 30 insertions, 0 deletions
diff --git a/lib/gitlab/utils.rb b/lib/gitlab/utils.rb
index e2d93e7cd29..3df54e74b4f 100644
--- a/lib/gitlab/utils.rb
+++ b/lib/gitlab/utils.rb
@@ -10,6 +10,8 @@ module Gitlab
     # Also see https://gitlab.com/gitlab-org/gitlab/-/merge_requests/24223#note_284122580
     # It also checks for ALT_SEPARATOR aka '\' (forward slash)
     def check_path_traversal!(path)
+      return unless path.is_a?(String)
+
       path = decode_path(path)
       path_regex = /(\A(\.{1,2})\z|\A\.\.[\/\\]|[\/\\]\.\.\z|[\/\\]\.\.[\/\\]|\n)/
 
@@ -208,5 +210,33 @@ module Gitlab
     def stable_sort_by(list)
       list.sort_by.with_index { |x, idx| [yield(x), idx] }
     end
+
+    # Check for valid brackets (`[` and `]`) in a string using this aspects:
+    # * open brackets count == closed brackets count
+    # * (optionally) reject nested brackets via `allow_nested: false`
+    # * open / close brackets coherence, eg. ][[] -> invalid
+    def valid_brackets?(string = '', allow_nested: true)
+      # remove everything except brackets
+      brackets = string.remove(/[^\[\]]/)
+
+      return true if brackets.empty?
+      # balanced counts check
+      return false if brackets.size.odd?
+
+      unless allow_nested
+        # nested brackets check
+        return false if brackets.include?('[[') || brackets.include?(']]')
+      end
+
+      # open / close brackets coherence check
+      untrimmed = brackets
+      loop do
+        trimmed = untrimmed.gsub('[]', '')
+        return true if trimmed.empty?
+        return false if trimmed == untrimmed
+
+        untrimmed = trimmed
+      end
+    end
   end
 end