fix xss on error page

html/error_test.go

@@ -0,0 +1,38 @@
+package html
+
+import (
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func TestValidMessage(t *testing.T) {
+	testString := "requested blacklisted path"
+	statusCode := http.StatusForbidden
+
+	expected := strings.ReplaceAll(
+		strings.ReplaceAll(ErrorPage, "%message%", testString),
+		"%status%",
+		http.StatusText(statusCode))
+	actual := generateResponse(testString, statusCode)
+
+	if expected != actual {
+		t.Errorf("generated response did not match: expected: '%s', got: '%s'", expected, actual)
+	}
+}
+
+func TestMessageWithHtml(t *testing.T) {
+	testString := `abc<img src=1 onerror=alert("xss");`
+	escapedString := "abc&lt;img src=1 onerror=alert(&#34;xss&#34;);"
+	statusCode := http.StatusNotFound
+
+	expected := strings.ReplaceAll(
+		strings.ReplaceAll(ErrorPage, "%message%", escapedString),
+		"%status%",
+		http.StatusText(statusCode))
+	actual := generateResponse(testString, statusCode)
+
+	if expected != actual {
+		t.Errorf("generated response did not match: expected: '%s', got: '%s'", expected, actual)
+	}
+}