There’s no such thing. Peergos implemented block-level access control so perhaps it gives you inspiration: Release the BATs (block level access control in IPFS)
IPFS offers serveral ways of “accessing the data”, so depending on them the problem can be attacked at different layers (not necessarily block-layer level). For example, Bitswap has WithPeerBlockRequestFilter() which can be used to only allow bitswap retrievals to specific peers (this is used on Rainbow):