fix: removes multiline from default regex modifiers [breaking]

internal/operators/rx.go

@@ -24,10 +24,10 @@ type rx struct {
 var _ plugintypes.Operator = (*rx)(nil)
 
 func newRX(options plugintypes.OperatorOptions) (plugintypes.Operator, error) {
-	// (?sm) enables multiline and dotall mode, required by some CRS rules and matching ModSec behavior, see
-	// - https://stackoverflow.com/a/27680233
-	// - https://groups.google.com/g/golang-nuts/c/jiVdamGFU9E
-	data := fmt.Sprintf("(?sm)%s", options.Arguments)
+	// (?s) enables dotall mode, required by some CRS rules and matching ModSec behavior, see
+	// - https://github.com/google/re2/wiki/Syntax
+	// - Flag usage: https://groups.google.com/g/golang-nuts/c/jiVdamGFU9E
+	data := fmt.Sprintf("(?s)%s", options.Arguments)
 
 	if matchesArbitraryBytes(data) {
 		// Use binary regex matcher if expression matches non-utf8 bytes. The binary matcher does

internal/operators/rx_test.go

@@ -55,22 +55,42 @@ func TestRx(t *testing.T) {
 			want:    true,
 		},
 		{
-			// Requires multiline
+			// Requires multiline disabled by default
 			pattern: `^hello.*world`,
 			input:   "test\nhello\nworld",
+			want:    false,
+		},
+		{
+			// Makes sure multiline can be enabled by the user
+			pattern: `(?m)^hello.*world`,
+			input:   "test\nhello\nworld",
 			want:    true,
 		},
 		{
-			// Makes sure, (?sm) passed by the user does not
+			// Makes sure, (?s) passed by the user does not
 			// break the regex.
-			pattern: `(?sm)hello.*world`,
+			pattern: `(?s)hello.*world`,
 			input:   "hello\nworld",
 			want:    true,
 		},
 		{
 			// Make sure user flags are also applied
-			pattern: `(?i)^hello.*world`,
-			input:   "test\nHELLO\nworld",
+			pattern: `(?i)hello.*world`,
+			input:   "testHELLO\nworld",
+			want:    true,
+		},
+		{
+			// The so called DOLLAR_ENDONLY modifier in PCRE2 is meant to tweak the meaning of dollar '$'
+			// so that it matches only at the very end of the string (see: https://www.pcre.org/current/doc/html/pcre2pattern.html#SEC6)
+			// It seems that re2 already behaves like that by default.
+			pattern: `123$`,
+			input:   "123\n",
+			want:    false,
+		},
+		{
+			// Dollar endonly match
+			pattern: `123$`,
+			input:   "test123",
 			want:    true,
 		},
 	}