The IETF provides official BibTeXs to download. They work for RFCs, BCPs, and drafts.
The BibTeXs for BCPs work, but only, if the BCP consists of a single RFC. If the BCP consists of multiple RFCs, the BibTeX will only show the first one.
For drafts, the draft version number, the last two digits, have to be removed from the URL.