more efficient calls to DAO functions

[code423n4]

Handle

gpersoon

Vulnerability details

Impact

Sometimes the reference to function calls, that are done via the DAO, are looked up multiple times in one function call.
For example mintSynth calls: ​

• _DAO() 4x
• _DAO().UTILS() 3x

This can be done more efficient by caching the result of _DAO() and _DAO().UTILS()

f## Proof of Concept
// https://github.com/code-423n4/2021-07-spartan/blob/main/contracts/Pool.sol#L229
​function mintSynth(address synthOut, address member) external returns(uint outputAmount, uint fee) {
​require(iSYNTHFACTORY(_DAO().SYNTHFACTORY()).isSynth(synthOut) == true, "!synth"); // Must be a valid Synth
​..
​uint output = iUTILS(_DAO().UTILS()).calcSwapOutput(_actualInputBase, baseAmount, tokenAmount); // Calculate value of swapping SPARTA to the relevant underlying TOKEN
​uint _liquidityUnits = iUTILS(_DAO().UTILS()).calcLiquidityUnitsAsym(_actualInputBase, address(this)); // Calculate LP tokens to be minted
​..
​uint _fee = iUTILS(_DAO().UTILS()).calcSwapFee(_actualInputBase, baseAmount, tokenAmount); // Calc slip fee in TOKEN
​fee = iUTILS(_DAO().UTILS()).calcSpotValueInBase(TOKEN, _fee); // Convert TOKEN fee to SPARTA
​

function _DAO() internal view returns(iDAO) {
​return iBASE(BASE).DAO();
​}

//https://github.com/code-423n4/2021-07-spartan/blob/main/contracts/Dao.sol#L624
​function UTILS() public view returns(iUTILS){
​if(daoHasMoved){
​return Dao(DAO).UTILS();
​} else {
​return _UTILS;
​}
​}

Tools Used

Recommended Mitigation Step

Cache _DAO() and cache the sub functions like: _DAO().UTILS())
If called multiple times from function