+/* ARGSUSED */
+static enum rofferr
+roff_so(ROFF_ARGS)
+{
+ char *name;
+
+ (*r->msg)(MANDOCERR_SO, r->data, ln, ppos, NULL);
+
+ /*
+ * Handle `so'. Be EXTREMELY careful, as we shouldn't be
+ * opening anything that's not in our cwd or anything beneath
+ * it. Thus, explicitly disallow traversing up the file-system
+ * or using absolute paths.
+ */
+
+ name = *bufp + pos;
+ if ('/' == *name || strstr(name, "../") || strstr(name, "/..")) {
+ (*r->msg)(MANDOCERR_SOPATH, r->data, ln, pos, NULL);
+ return(ROFF_ERR);
+ }
+
+ *offs = pos;
+ return(ROFF_SO);
+}