OIDs are just numbers in the format 1.2.3.4.5.6.7.8.9... Short names are alphanumeric, contiguous descriptions (no spaces, hyphens allowed) Long names can be basically everything (sometimes even UTF-8!)

Sometimes, organisations providing the list of 'their' OIDs might reverse the order, for listing a directory reference (look up the name, then figure out what OID it is being assigned to). This regexp captures this 'reverse directory' scheme and rewrites everything properly for OpenSSL.