bughuntoor - Whale LP providers can open positions on both sides to force users into high fees.

[sherlock-admin3]

bughuntoor

High

Whale LP providers can open positions on both sides to force users into high fees.

Summary

Whale LP providers can open positions on both sides to force users into high fees.

Vulnerability Detail

LP fees within the protocol are based on utilization percentage of the total funds in the pool. The problem is that this could easily be abused by LP providers in the following way.

Consider a pool where the majority of the liquidity is provided by a single user.

1. Users have opened positions at a relatively low utilization ratio
2. The whale LP provider opens same size positions in both directions at 1 leverage.
3. This increases everyone's fees. Given that the LP provider holds majority of the liquidity, most of the new fees will go towards them, making them a profit.

As long as the whale can maintain majority of the liquidity provided, attack remains profitable. If at any point they can no longer afford maintaining majority, they can simply close their positions without taking a loss, so this is basically risk-free.

Impact

Loss of funds

Code Snippet

https://github.com/sherlock-audit/2024-08-velar-artha/blob/main/gl-sherlock/contracts/params.vy#L33

Tool used

Manual Review

Recommendation

Consider a different way to calculate fees

[msheikhattari]

Escalate
Invalid. Quoting a valid point from your own comment:

Issue should be low/info. Ultimately, all LPs would want is fees and this would give them the highest fees possible. Furthermore, the attack is extremely costly, as it would require user to lock up hundreds of thousands/ millions, losing a significant % of them. Any user would have an incentive to add liquidity at extremely high APY, which would allow for both new positions opens and LP withdraws.

This attack inflates borrow fees, but the high APY will attract other LP depositors which would drive the utilization back down to normal levels, reducing the fee. Unlike the issue that you were escalating, this one has no such time sensitivity - the market would naturally tend towards rebalance within the next several days / weeks. It's not reasonable to assume that the existing positions would remain open despite high fees and other LPs would not enter the market over the coming days/weeks.

Not only that, the other assumptions of this issue are incorrect:

If at any point they can no longer afford maintaining majority, they can simply close their positions without taking a loss, so this is basically risk-free.

Wrong. Each opened long AND short position must pay a fixed fee, so the whale is taking a risk. He is betting that the current positions will not close, and his stake will not get diluted, just long enough to eke out a net profit. And this is assuming he had a majority stake to begin with, which for the more liquid pools where the attack is most profitable due to a large amount of open interest, is a highly questionable assumption.

The game theory makes it unlikely that the whale would be able to extract enough extra fees to even make a profit net of the operating fees of such an attack.

[sherlock-admin3]

Escalate
Invalid. Quoting a valid point from your own comment:

Issue should be low/info. Ultimately, all LPs would want is fees and this would give them the highest fees possible. Furthermore, the attack is extremely costly, as it would require user to lock up hundreds of thousands/ millions, losing a significant % of them. Any user would have an incentive to add liquidity at extremely high APY, which would allow for both new positions opens and LP withdraws.

This attack inflates borrow fees, but the high APY will attract other LP depositors which would drive the utilization back down to normal levels, reducing the fee. Unlike the issue that you were escalating, this one has no such time sensitivity - the market would naturally tend towards rebalance within the next several days / weeks. It's not reasonable to assume that the existing positions would remain open despite high fees and other LPs would not enter the market over the coming days/weeks.

Not only that, the other assumptions of this issue are incorrect:

If at any point they can no longer afford maintaining majority, they can simply close their positions without taking a loss, so this is basically risk-free.

Wrong. Each opened long AND short position must pay a fixed fee, so the whale is taking a risk. He is betting that the current positions will not close, and his stake will not get diluted, just long enough to eke out a net profit. And this is assuming he had a majority stake to begin with, which for the more liquid pools where the attack is most profitable due to a large amount of open interest, is a highly questionable assumption.

The game theory makes it unlikely that the whale would be able to extract enough extra fees to even make a profit net of the operating fees of such an attack.

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[WangSecurity]

@spacegliderrrr do you have any counterarguments?

[spacegliderrrr]

@WangSecurity Issue above showcases a real issue which could occur if a whale decides to attack a pool.

Each opened long AND short position must pay a fixed fee, so the whale is taking a risk. He is betting that the current positions will not close, and his stake will not get diluted, just long enough to eke out a net profit.

True, there's some risk, though most of it can be mitigated. For example if the attack is performed when most opened positions are at negative PnL (which would mean closing them is profitable to the LP providers), most of the risk is mitigated as users have 2 choices - close early at a loss or keep the position open at high fees (either way, profitable for the LP provider).

the market would naturally tend towards rebalance within the next several days / weeks.

True, though as mentioned, it would take days/ weeks in which the whale could profit.

The issue does involve some game theory, but nonetheless shows an actual risk to honest users.

[WangSecurity]

I also agree there are lots of risks, with this scenario. But, it's still possible to pose losses on other users in a way of arbitrary increasing fees. The market would rebalance, but it can even take less than a day to cause losses to users. Hence, I agree that this issue should remain medium severity, because even though the issue has high constraints, still can cause losses. Planning to reject the escalation.

[WangSecurity]

Result:
Medium
Unique

[sherlock-admin4]

Escalations have been resolved successfully!

Escalation status:

• msheikhattari: rejected