Unnecessary indirection to access block.timestamp value

[code423n4]

Handle

0xRajeev

Vulnerability details

Impact

_currentTime() returns the block.timestamp value to multiple call sites in PrizePool contract. This internal call only to get value of block.timestamp seems unnecessary because there isn’t any other way of getting current time on the blockchain which justifies moving this to a separate function for modularity.

Impact: Adds an additional jump and other supporting bytecode of making the internal call which increase gas usage unnecessarily.

Proof of Concept

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L1019-L1023

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L381

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L409

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L654

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L840

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/PrizePool.sol#L880

Tools Used

Manual Analysis

Recommended Mitigation Steps

Use block.timestamp directly to save a little gas by avoiding this unnecessary indirection.

[asselstine]

We need to manipulate the time for testing, and changing the EVM time via _increaseTime wasn't working consistently.