Does anyone know a reliable way of fetching price of a token from AMMs, without the interference of flashloan manipulations onto a contract?

Without using an oracle too...

the price at any given time is simply the pair's balance of the token in question divided by the pair's balance of the other token

or vice versa

not balance, but reserves

yes

Which can be manipulated by a flashloan. I know how to get the price from pair, but need some reliability

Aren't flash loans paid back within the same transaction? And even during that, the reserves aren't affected, only the balances. So if you need a correct price even inside a flashloaned transaction, you can still use reserves

Reserves get updated at end of the tx

I have a different usecase

Token price is taken for a reward calculation purpose

Ok I'm unsure why a flash loan happening in one transaction would matter

My attack scenario is
Take bnb flashloan and buy token x
Call a function in my contract
Fetching token x price from manipulated pool
Gets huge amount of reward than normal
Sell x token and repay bnb flashloan

Wanna avoid this

Reserves aren't affected by flash loan during the transaction...only at the end (after the loan is paid back)

Flashloan is not taken in token, rather bnb or some stable coin

Which is then used to purchase the token

Which will affect the reserve

Edited so that it makes more sense

How does 1inch calculate price. If I pull price from their aggregator, will that be more reliable?

Ok that makes more sense. Maybe you need a twap then

Umm what's a twap?

Time weighted average price

I believe uniswap v2 contracts have a simple one built in

Haha that's what I am doing right now

Using 15 data points to average

Or if you want to use reserves, just maybe use reserves from a block in the recent past, then the flash loan attack doesn't seem possible?

Ooh they do? Have some docs pointing to that?

I think so...on mobile right now but I recall seeing it

Which cannot be accessed in solidity unfortunately

Well if you fetch/store it you can...

I.e. piggybacking off some other transactions perhaps

Just a thought, Ive seen similar strategies

Thought of that, but my contract won't have much traffic. Setting up a bot would be costly too

Yeah on eth it will suck for sure

Exactly. Couple 1000 bucks per day

No thanks xD

Other option is setting up a chainlink price feed I suppose

Thought of that too, but I have multiple tokens whose price should be fetched. So I have to pay chainlink to make oracles for each of them...

Don't think that's ideal

I'll look into this more. As of now I'm calculating manually, so if there is an already built in method, I'll just pick that

Thanks for your input @coffeeconverter :)

No prob yeah hopefully that works

Yes

Look at the white paper

They call it out. Might also be in their online docs, bht it’s for sure in their white paper