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code-423n4 / 2021-05-yield-findings

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Constants "chi" and "rate" #13

Open code423n4 opened 3 years ago

code423n4 commented 3 years ago

Handle

gpersoon

Vulnerability details

Impact

Several implementations of the value of "chi" and "rate" are used, sometimes as constant and sometimes the direct value is used, see proof of concept below. The risk is that if it is changed in one place if might not be changed in another place, leading to bugs.

Proof of Concept

// https://github.com/code-423n4/2021-05-yield/blob/main/contracts/Wand.sol#L26 bytes6 public constant CHI = "chi"; bytes6 public constant RATE = "rate";

// https://github.com/code-423n4/2021-05-yield/blob/main/contracts/FYToken.sol#L27 bytes32 constant CHI = "chi";

//https://github.com/code-423n4/2021-05-yield/blob/main/contracts/oracles/compound/CompoundMultiOracle.sol#L40 function _peek(bytes6 base, bytes6 kind) private view returns (uint price, uint updateTime) { ... if (kind == "rate") rawPrice = CTokenInterface(source).borrowIndex(); else if (kind == "chi") rawPrice = CTokenInterface(source).exchangeRateStored();

Tools Used

grep

Recommended Mitigation Steps

Define the constants for "chi" and "rate" on one location and include this where required.

alcueca commented 3 years ago

We can create a Constants.sol contract, for others to inherit to. The downside is code readability, but it is probably an acceptable trade-off.

However, I can't think of an scenario in which we would want to change these constants, and as a matter of fact we can't because they are included in Cauldron, and this contract is not upgradable. I would downgrade the risk to 0.