Assuming Oracle price feed precision can lead to incorrect value calculation

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Assuming Oracle price feed precision can lead to incorrect value calculation

Severity

Medium Risk

Relevant GitHub Links

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L70

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L347

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L366

Summary

Assuming that all x/usd Oracle price feeds return in 8 decimal places can lead to incorrect price calculation for x/usd price feeds which return in 18 decimal places.

Vulnerability Details

Although btc/usd, eth/usd & many x/usd price feeds return the answer in 8 decimal places, there are also price feeds such as ampl/usd which return the answer in 18 decimal places.

This project aims to allow others to setup their own collateral tokens, however due to the hard-coded assumption that all price feeds will return in 8 decimal places this will result in incorrect value calculation for price feeds that return in decimals other than 8.

Impact

Incorrect calculation of token amount & usd value for prices feeds that return with decimal precision != 8 can result in losses to users and to the protocol.

Tools Used

Manual

Recommendations

Read the decimal precision from the price feed and dynamically calculate the required adjustment (ADDITIONAL_FEED_PRECISION) to multiply by.