[Feature] Detect URLs with suspicious omographs

rules/misc.lua

@@ -756,4 +756,28 @@ local freemail_reply_neq_from_id = rspamd_config:register_symbol({
   score = 3.0
 })
 rspamd_config:register_dependency(freemail_reply_neq_from_id, 'FREEMAIL_REPLYTO')
-rspamd_config:register_dependency(freemail_reply_neq_from_id, 'FREEMAIL_FROM')
+rspamd_config:register_dependency(freemail_reply_neq_from_id, 'FREEMAIL_FROM')
+
+rspamd_config.OMOGRAPH_URL = {
+  callback = function(task)
+    local urls = task:get_urls()
+
+    if urls then
+      for _,u in ipairs(urls) do
+        local h = u:get_host()
+
+        if h then
+          local non_latin,total = util.count_non_ascii(h)
+
+          if non_latin ~= total and non_latin > 0 then
+            return true, 1.0, h
+          end
+        end
+      end
+    end
+
+    return false
+  end,
+  score = 5.0,
+  description = 'Url contains both latin and non-latin characters'
+}

src/lua/lua_util.c

@@ -362,6 +362,13 @@ LUA_FUNCTION_DEF (util, zstd_decompress);
  * @return {number} normalized number
  */
 LUA_FUNCTION_DEF (util, normalize_prob);
+/***
+ * @function util.count_non_ascii(str)
+ * Returns number of non ascii characters in a specified string counting merely alpha
+ * characters. A string can be in non-utf form.
+ * @return {number,number} number of non-ascii alphas and total number of alphas
+ */
+LUA_FUNCTION_DEF (util, count_non_ascii);
 
 /***
  * @function util.pack(fmt, ...)
@@ -485,6 +492,7 @@ static const struct luaL_reg utillib_f[] = {
 	LUA_INTERFACE_DEF (util, zstd_decompress),
 	LUA_INTERFACE_DEF (util, normalize_prob),
 	LUA_INTERFACE_DEF (util, caseless_hash),
+	LUA_INTERFACE_DEF (util, count_non_ascii),
 	LUA_INTERFACE_DEF (util, pack),
 	LUA_INTERFACE_DEF (util, unpack),
 	LUA_INTERFACE_DEF (util, packsize),
@@ -1825,6 +1833,40 @@ lua_util_caseless_hash (lua_State *L)
 	return 1;
 }
 
+static gint
+lua_util_count_non_ascii (lua_State *L)
+{
+	gsize len;
+	const gchar *str = lua_tolstring (L, 1, &len);
+	const gchar *p, *end;
+	gint ret = 0, total = 0;
+
+	if (str != NULL) {
+		end = str + len;
+		p = str;
+
+		while (p < end) {
+			if (*p & 0x80) {
+				ret ++;
+				total ++;
+			}
+			else if (g_ascii_isalpha (*p)) {
+				total ++;
+			}
+
+			p ++;
+		}
+
+		lua_pushnumber (L, ret);
+		lua_pushnumber (L, total);
+	}
+	else {
+		return luaL_error (L, "invalid arguments");
+	}
+
+	return 2;
+}
+
 /* Backport from Lua 5.3 */
 
 /******************************************************************************