SHOULD CHECK RETURN DATA FROM CHAINLINK AGGREGATORS

[code423n4]

Lines of code

https://github.com/code-423n4/2022-02-hubble/blob/main/contracts/Oracle.sol#L33
https://github.com/code-423n4/2022-02-hubble/blob/8c157f519bc32e552f8cc832ecc75dc381faa91e/contracts/MarginAccount.sol#L465
https://github.com/code-423n4/2022-02-hubble/blob/8c157f519bc32e552f8cc832ecc75dc381faa91e/contracts/MarginAccount.sol#L524

Vulnerability details

Impact

The getUnderlyingPrice function in the contract Oracle.sol fetches the asset price from a Chainlink aggregator using the latestRoundData function. However, there are no checks on roundID nor timeStamp, resulting in stale prices. The oracle wrapper calls out to a chainlink oracle receiving the latestRoundData(). It then checks freshness by verifying that the answer is indeed for the last known round. The returned updatedAt timestamp is not checked.

If there is a problem with chainlink starting a new round and finding consensus on the new value for the oracle (e.g. chainlink nodes abandon the oracle, chain congestion, vulnerability/attacks on the chainlink system) consumers of this contract may continue using outdated stale data (if oracles are unable to submit no new round is started)

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-hubble/blob/8c157f519bc32e552f8cc832ecc75dc381faa91e/contracts/MarginAccount.sol#L465

2. getUnderlyingPrice function has been used without validation of the return data. Oracle contract has getUnderlyingTwapPrice but the above contract does not use it.

3. Stale prices could put funds at risk. According to Chainlink's documentation, This function does not error if no answer has been reached but returns 0, causing an incorrect price fed to the PriceOracle. The external Chainlink oracle, which provides index price information to the system, introduces risk inherent to any dependency on third-party data sources. For example, the oracle could fall behind or otherwise fail to be maintained, resulting in outdated data being fed to the index price calculations of the AMM. Oracle reliance has historically resulted in crippled on-chain systems, and complications that lead to these outcomes can arise from things as simple as network congestion.

Medium Severity Issue From The FEI Protocol : https://consensys.net/diligence/audits/2021/09/fei-protocol-v2-phase-1/#chainlinkoraclewrapper-latestrounddata-might-return-stale-results

Tools Used

Code review

Recommended Mitigation Steps

Consider checking the oracle responses updatedAt value after calling out to chainlinkOracle.latestRoundData() verifying that the result is within an allowed margin of freshness.

(uint80 roundID, int256 price, , uint256 timeStamp, uint80 answeredInRound) = ETH_CHAINLINK.latestRoundData();
require(price > 0, "Chainlink price <= 0"); 
require(answeredInRound >= roundID, "...");
require(timeStamp != 0, "...");

[atvanguard]

Duplicate of #46