function sponsor not allways present

[code423n4]

Handle

gpersoon

Vulnerability details

Impact

The function sponsor is implemented in 3 of the 5 yield sources (ATokenYieldSource.sol, IdleYieldSource.sol, YearnV2YieldSource.sol)
However 2 of the 5 yield sources don't have the function sponsor ( BadgerYieldSource.sol and SushiYieldSource.sol)

Note it isn't part of the official spec: https://github.com/pooltogether/yield-source-interface/blob/main/contracts/IYieldSource.sol
It isn't consistent that not all sources have the same function.

Proof of Concept

.\contracts\yield-source\ATokenYieldSource.sol: function sponsor(uint256 amount) external override {
.\contracts\yield-source\IdleYieldSource.sol: function sponsor(uint256 amount) external override {
.\contracts\yield-source\YearnV2YieldSource.sol: function sponsor(uint256 amount) external nonReentrant {

Tools Used

Consider adding the function sponsor to BadgerYieldSource.sol and SushiYieldSource.sol.

Recommended Mitigation Steps