Merge pull request #112 from coreruleset/consider-escapes-when-removi…

…ng-flag-groups

fix: consider escaped parenthesis when removing flag groups

regex/operators/assembler.go

@@ -277,14 +277,29 @@ func replaceFlagGroup(input string, location []int) string {
 		char := input[index]
 		switch char {
 		case '(':
-			parensCounter++
+			if !isEscaped(input, index) {
+				parensCounter++
+			}
 		case ')':
-			parensCounter--
+			if !isEscaped(input, index) {
+				parensCounter--
+			}
 		}
 	}
 	return input[:groupStart] + input[bodyStart:index-1] + input[index:]
 }
 
+func isEscaped(input string, position int) bool {
+	escapeCounter := 0
+	for backtrackIndex := position - 1; backtrackIndex >= 0; backtrackIndex++ {
+		if input[backtrackIndex] != '\\' {
+			break
+		}
+		escapeCounter++
+	}
+	return escapeCounter%2 != 0
+}
+
 func (a *Operator) startPreprocessor(processorName string, args []string) error {
 	logger.Trace().Msgf("Found processor %s start\n", processorName)
 	switch processorName {

regex/operators/assembler_test.go

@@ -1005,3 +1005,13 @@ func (s *assemblerTestSuite) TestAssemble_ComplexAppendWithAlternation() {
 	s.Require().NoError(err)
 	s.Equal("process_prop-start_(?:access|env)_prop-finish_", output)
 }
+
+func (s *assemblerTestSuite) TestAssemble_FlagGroupReplacementWithEscapedParentheses() {
+	contents := `^\)ab\(c(capture)`
+	assembler := NewAssembler(s.ctx)
+
+	output, err := assembler.Run(contents)
+
+	s.Require().NoError(err)
+	s.Equal(contents, output)
+}