RebateFi Hook

Description

• For a sell transaction the ReFiSwapRebateHook contract only applies a static 3_000 fee to each transaction irrespective of transaction size rather than the documented 0.3% sell fee.

Impacted Code:

• The fee calculation should be based on a dynamic calculation not a flat 3_000 fee irrespective of transaction size.

Risk

Likelihood:

• Likelihood is High - All sell transactions will have the incorrect over/under-charged fees applied.

• Rather than charging the documented 0.3%, the protocol is charging 3_000 per sell transaction.

Impact:

• Impact is High - The protocol documents a standard 0.3% fee, but instead charges 3_000 per transaction.

• Should a transaction be less than 3_000, the customer is likely to get nothing in return as the fee amount takes everything.

• Similarly for large transactions the protocol would undercharge fees.

Proof of Concept

The following is currently occurring:

Example 1:

1. A customer wants to swap 10_000.

2. They expect a fee of 30 (10_000 * 0.3%), but is instead charged 3_000

3. They are now out of pocket by a substantial amount.

Example 2:

1. A customer wants to swap 1_000.

2. They expect a fee of 3 (1_000 * 0.3%), but is instead charged a fee of 3_000, which is more than the transaction value.

3. They get nothing back as the fee has taken all.

Example 3:

1. A customer wants to swap 10_000_000.

2. They expect a fee of 30_000 (10_000_000 * 0.3%), but is instead charged a lower fee of 3_000.

3. The customer is able to receive more than they should.

Recommended Mitigation

To ensure the protocol applies the correct fee the below code change should be applied.