NFT marketplace auctions - expiration date function trigger

[MarkizOrias]

Hey Guys!
I'm trying to build something similar to what OpenSea is offering. I would like to spice up a bit the NFT marketplace project from lesson 15 and add the auctioning functionality, apart from the plain sell/buy.

What I've learned is that using block.timestamp value can be manipulated by nodes and is exposing the smart contract to vulnerabilities. So the best practice would be integrating the counter till auction's expiry directly in the Front-end.

But at the very end of the auction, an ownable function (only by auctioning contract's owner) should be called in order to:

1. Change the state of the NFT from OPEN to CLOSED for auctioning.
2. Transfer the NFT token to the highest bidder.
3. Withdraw the auctioning contract's balance to the owner.

I have a trouble understanding how that can be arranged in the most efficient and secure way, especially the point 2 & 3. Front-end is using only contract's ABIs, so how it can authorize triggering ownable function, without having an access to the private key?

Would appreciate your designing hints, folks ;)

[alymurtazamemon]

@MarkizOrias You should use Chainlink's Keepers to automatically call the smart contract functions after the expiration.