addons/purchase/security/ir.model.access.csv

   1 id,name,model_id:id,group_id:id,perm_read,perm_write,perm_create,perm_unlink
   2 access_purchase_order,purchase.order,model_purchase_order,purchase.group_purchase_user,1,1,1,1
   3 access_purchase_order_line,purchase.order.line,model_purchase_order_line,purchase.group_purchase_user,1,1,1,1