Use of constant keccak variables results in extra hashing (and so gas).

[code423n4]

Handle

TomFrench

Vulnerability details

Impact

Increase gas costs on all onlyAdmin operations

Proof of Concept

The SLINGSHOT_ADMIN_ROLE variable is marked as constant:
https://github.com/code-423n4/2021-10-slingshot/blob/f6e7a0a39e3267bbe3c7fe60d6074cbf54f5750f/contracts/Adminable.sol#L11

This results in the keccak operation being performed whenever the variable is used, increasing gas costs relative to just storing the output hash. Changing to immutable will only perform hashing on contract deployment which will save gas.

See: ethereum/solidity#9232 (comment)

Recommended Mitigation Steps

Change the variable to be immutable rather than constant