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Submission Details
Severity: medium
Valid

Chainlink's `latestRoundData` might return stale or incorrect results

klaus

Summary

Can use stale prices

Vulnerability Details

OracleLib uses Chainlink’s latestRoundData, but there is no check if the return value indicates stale data.

function staleCheckLatestRoundData(AggregatorV3Interface priceFeed)
public
view
returns (uint80, int256, uint256, uint256, uint80)
{
(uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound) =
priceFeed.latestRoundData();
​
uint256 secondsSince = block.timestamp - updatedAt;
if (secondsSince > TIMEOUT) revert OracleLib__StalePrice();
​
return (roundId, answer, startedAt, updatedAt, answeredInRound);
}

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/d1c5501aa79320ca0aeaa73f47f0dbc88c7b77e2/src/libraries/OracleLib.sol#L21-L33

It also doesn't check return value at the caller of OracleLib.staleCheckLatestRoundData function.

(, int256 price,,,) = priceFeed.staleCheckLatestRoundData();

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/d1c5501aa79320ca0aeaa73f47f0dbc88c7b77e2/src/DSCEngine.sol#L345

(, int256 price,,,) = priceFeed.staleCheckLatestRoundData();

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/d1c5501aa79320ca0aeaa73f47f0dbc88c7b77e2/src/DSCEngine.sol#L363

Impact

This could lead to stale prices according to the Chainlink documentation

Tools Used

vscode

Recommendations

Add checks on the return data with proper revert messages if the price is stale or the round is uncomplete.

(uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound) =
priceFeed.latestRoundData();
require(answeredInRound >= roundId, "Stale price");
require(updatedAt != 0, "Round not complete");
require(answer > 0,"Chainlink answer reporting 0");

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