Kuiper contest - Meta0xNull's results

Handle

Meta0xNull

Vulnerability details

Impact

There are many Functions loops that follows this for-each pattern: for (uint256 i = 0; i < weights.length; i++) { // do something }

In such for loops, the weights.length is read from Storage on every iteration, instead of caching it once in a local variable and read it again using the local variable.

Storage reads are a bit more expensive than reading local variables.

Proof of Concept

https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L275 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L282 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L290

Tools Used

Manual Review

Recommended Mitigation Steps

Read these values from storage once, cache them in local variables and then read them again using the local variables. For example:

uint256 weights_temp = weights; for (uint256 i = 0; i < weights_temp.length; i++) { // do something // Replace weights[i] to weights_temp[i] }

Handle

Meta0xNull

Vulnerability details

Impact

The local variable used as for loop index need not be initialized to 0 because the default value is 0. Avoiding this anti-pattern can save a few opcodes and therefore a tiny bit of gas.

Proof of Concept

https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L75 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L79 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L275 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L282 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Basket.sol#L289 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Factory.sol#L109 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Auction.sol#L88 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Auction.sol#L92 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Auction.sol#L105 https://github.com/code-423n4/2021-12-defiprotocol/blob/main/contracts/contracts/Auction.sol#L152

Tools Used

Manual Review

Recommended Mitigation Steps

Remove explicit 0 initialization of for loop index variable.

Before: for (uint256 i = 0; After for (uint256 i;