Attacker can grift syndicate staking by staking a small amount

[code423n4]

Lines of code

https://github.com/code-423n4/2022-11-stakehouse/blob/a0558ed7b12e1ace1fe5c07970c7fc07eb00eebd/contracts/liquid-staking/LiquidStakingManager.sol#L882
https://github.com/code-423n4/2022-11-stakehouse/blob/23c3cf65975cada7fd2255a141b359a6b31c2f9c/contracts/syndicate/Syndicate.sol#L22

Vulnerability details

Impact

LiquidStakingManager._autoStakeWithSyndicate always stakes a fixed amount of 12 ETH. However, Syndicate.stake only allows a total staking amount of 12 ETH and reverts otherwise:

if (_sETHAmount + totalStaked > 12 ether) revert InvalidStakeAmount();

An attacker can abuse this and front-run calls to mintDerivatives (which call _autoStakeWithSyndicate internally). Because Syndicate.stake can be called by everyone, he can stake the minimum amount (1 gwei) such that the mintDerivatives call fails.

Proof Of Concept

As soon as there is a mintDerivatives call in the mempool, an attacker (that owns sETH) calls Syndicate.stake with an amount of 1 gwei. _autoStakeWithSyndicate will still call Syndicate.stake with 12 ether. However, _sETHAmount + totalStaked > 12 ether will then be true, meaning that the call will revert.

Recommended Mitigation Steps

Only allow staking through the LiquidStakingManager, i.e. add access control to Syndicate.stake.

[c4-judge]

dmvt marked the issue as primary issue

[c4-sponsor]

vince0656 marked the issue as sponsor confirmed

[c4-judge]

dmvt marked the issue as selected for report

[c4-judge]

dmvt marked the issue as satisfactory

[trust1995]

Classic Lambda find, awesome as usual.