From a805102dd844932e9b51446f9200065104b29152 Mon Sep 17 00:00:00 2001
From: shifter <shifter@axoflow.com>
Date: Thu, 28 Nov 2024 09:12:29 +0100
Subject: [PATCH] filterx: performance and safe code fix for regex_subst match
 groups + additional unit test for enabled but unused 'group' feature

Signed-off-by: shifter <shifter@axoflow.com>
---
 lib/filterx/expr-regexp.c            | 26 +++++++++++++++++---------
 lib/filterx/tests/test_expr_regexp.c | 10 ++++++++++
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/lib/filterx/expr-regexp.c b/lib/filterx/expr-regexp.c
index c8ddb28b4..fe88776b9 100644
--- a/lib/filterx/expr-regexp.c
+++ b/lib/filterx/expr-regexp.c
@@ -49,6 +49,7 @@ typedef struct FilterXReMatchState_
   FilterXObject *lhs_obj;
   const gchar *lhs_str;
   gsize lhs_str_len;
+  gint rc;
 } FilterXReMatchState;
 
 static void
@@ -113,6 +114,7 @@ _match_inner(FilterXReMatchState *state, pcre2_code_8 *pattern, gint start_offse
   gint rc = pcre2_match(pattern, (PCRE2_SPTR) state->lhs_str, (PCRE2_SIZE) state->lhs_str_len, (PCRE2_SIZE) start_offset,
                         0,
                         state->match_data, NULL);
+  state->rc = rc;
   if (rc < 0)
     {
       switch (rc)
@@ -551,6 +553,8 @@ _build_replacement_stirng_with_match_groups(const FilterXFuncRegexpSubst *self,
   PCRE2_SIZE *ovector = pcre2_get_ovector_pointer(state->match_data);
   g_string_set_size(replacement_string, 0);
   const gchar *rep_ptr = self->replacement;
+  const gchar *last_ptr = rep_ptr;
+  gint num_grps = state->rc;
 
   while (*rep_ptr)
     {
@@ -559,22 +563,26 @@ _build_replacement_stirng_with_match_groups(const FilterXFuncRegexpSubst *self,
           rep_ptr++;
           if (*rep_ptr >= '1' && *rep_ptr <= '9')
             {
-              gint grp_num = *rep_ptr - '0';
-              PCRE2_SIZE start = ovector[2 * grp_num];
-              PCRE2_SIZE end = ovector[2 * grp_num + 1];
-              if (start != PCRE2_UNSET)
+              gint grp_idx = *rep_ptr - '0';
+              if (grp_idx < num_grps)
                 {
-                  size_t group_len = end - start;
-                  g_string_append_len_inline(replacement_string, state->lhs_str + start, group_len);
+                  PCRE2_SIZE start = ovector[2 * grp_idx];
+                  PCRE2_SIZE end = ovector[2 * grp_idx + 1];
+                  if (start != PCRE2_UNSET)
+                    {
+                      g_string_append_len(replacement_string, last_ptr, rep_ptr - last_ptr - 1);
+                      last_ptr = rep_ptr + 1;
+                      size_t group_len = end - start;
+                      g_string_append_len(replacement_string, state->lhs_str + start, group_len);
+                    }
                 }
             }
           rep_ptr++;
         }
       else
-        {
-          g_string_append_c_inline(replacement_string, *rep_ptr++);
-        }
+        rep_ptr++;
     }
+  g_string_append_len(replacement_string, last_ptr, rep_ptr - last_ptr);
   return TRUE;
 }
 
diff --git a/lib/filterx/tests/test_expr_regexp.c b/lib/filterx/tests/test_expr_regexp.c
index d4c38f021..3447b0e40 100644
--- a/lib/filterx/tests/test_expr_regexp.c
+++ b/lib/filterx/tests/test_expr_regexp.c
@@ -547,6 +547,16 @@ Test(filterx_expr_regexp, regexp_subst_group_subst)
   filterx_object_unref(result_alt);
 }
 
+Test(filterx_expr_regexp, regexp_subst_group_subst_without_ref)
+{
+  FilterXFuncRegexpSubstOpts opts = {.groups = TRUE};
+  FilterXObject *result = _sub("(\\d{2})-(\\d{2})-(\\d{4})", "group without ref", "25-02-2022", opts);
+  cr_assert(filterx_object_is_type(result, &FILTERX_TYPE_NAME(string)));
+  const gchar *res = filterx_string_get_value_ref(result, NULL);
+  cr_assert_str_eq(res, "group without ref");
+  filterx_object_unref(result);
+}
+
 static void
 setup(void)
 {