QA Report

[code423n4]

Some tokens require the approval to be zero before calling approve with a non-zero value

Summary: some ERC20 tokens require approving to 0 first

Details: Some tokens (such as USDT) do not work when changing the allowance from an existing non-zero allowance value.

Mitigation: In L50 of TopUpAction.sol change the code to

IERC20(token).safeApprove(stakerVaultAddress, 0);
IERC20(token).safeApprove(stakerVaultAddress, depositAmount);

The same pattern should be applied to the following lines mutatis mutandis:

• L847 of TopUpAction.sol
• L908 of TopUpAction.sol
• L209 of StrategySwapper.sol
• L21 of Erc20Vault.sol
• L22 of Erc20Vault.sol

Impact: Low, depending which tokens will be integrated in backd

Misleading Error message

Summary: misleading error message could potentially confuse developers when debugging code

Details:

On L86 of Preparable.sol, if deadlines[key] is zero then the return message will be Error.DEADLINE_NOT_ZERO, which is the opposite condition of the error (cf. L28 of Preparable.sol for the same error but with the correct context).

The same can be said of L98 of Preparable.sol.

Impact: Code QA

Typos

• palce instead of place in Preparable.sol

TODOs left in the code

• L4 of ConvexStrategyBase.sol
• L5 of ConvexStrategyBase.sol
• L713 of TopUpAction.sol: this one is essential for not underestimating gas costs in user´s gas bank