Fix/chainlight 006 Unused Gas Penalty

[filmakarov]

Fix this.

-SponsorshipPaymaster now charges maxPenalty = (mUserOp.callGasLimit + mUserOp.paymasterPostOpGasLimit) * 10 / 100 * maxFeePerGas at _validatePaymasterUserOp.

• SponsorshipPaymaster now emits the actual gas cost (A+U) before applying it's own fee. This value can be used on the backend to calculate the refund , which is needed to be executed to paymasterId in regards of the difference b/w maxPenalty and actual penalty.
• Refund would be calculated in a following way:

let's define the EP.actualGasCost emitted here as EPAGC.

Then EPAGC = A + P + actualPenalty, where A is actualGasCost passed to Paymaster.postOp here.
P is component brought by preGas - gasleft() from here , which you reference above as postOpCost I believe.
actualPenalty is the component added here

The amount deducted by Paymaster (leaving Paymaster premium coming from priceMarkup aside) is
PC = A + U + MaxPenalty.
Where U is (unaccountedGasCatched * actualUserOpFeePerGas) from here
And maxPenalty is as discussed above.

Assuming MaxPenalty >= actualPenalty && U >= P is true for all maxPenalty, actualPenalty, U, P

on backend we do amountToRefund = PC - EPAGC = (U - P) + (MaxPenalty - actualPenalty) which will reflect the exact amount overcharged by Paymaster.

• We do not account for Q = priceMarkup / _PRICE_DENOMINATOR when calculating the refund.
  EP emits AGC w/o Q, Paymaster also emits it's gas cost (A+U) before applying Q.

[livingrockrises]

it will take lower 128?

[filmakarov]

yes

[livingrockrises]

What does the backend service do then with this event?