gentoo-overlay/sys-apps/shadow/files/shadow-4.1.3-dots-in-usernames.patch

--- shadow-4.1.3/libmisc/chkname.c
+++ shadow-4.1.3/libmisc/chkname.c
@@ -66,6 +66,7 @@
 		      ( ('0' <= *name) && ('9' >= *name) ) ||
 		      ('_' == *name) ||
 		      ('-' == *name) ||
+		      ('.' == *name) ||
 		      ( ('$' == *name) && ('\0' == *(name + 1)) )
 		     )) {
 			return false;