Error in maxMint calculation

[c4-bot-8]

Lines of code

https://github.com/code-423n4/2024-04-panoptic/blob/833312ebd600665b577fbd9c03ffa0daf250ed24/contracts/CollateralTracker.sol#L446

Vulnerability details

The calculation of the maximum shares received for a deposit in CollateralTracker.sol is incorrect.

In the mint() function, the assets received for a mint are being calculated using the previewMint() function, which has a mismatch with the current maxMint() function in the scenario in which the max possible assets are being deposited for the mint.

Impact

Detailed description of the impact of this finding.

Proof of Concept

Currently the maxMint() function calculates the max shares as follows :

 maxShares = (((type(uint104).max)*totalSupply()/totalAssets())*DECIMALS)/(DECIMALS+COMMISSION_FEE)

and previewMint() calculates the assets received as :

assets = (shares*DECIMALS*totalAssets())/(totalSupply*(DECIMALS-COMISSION_FEE))

In the max mint scenario, let's assume the assets required are maximum, i.e, type(uint104).max :

type(uint104).max = (maxShares*DECIMALS*totalAssets())/(totalSupply*(DECIMALS-COMISSION_FEE))

Simplifying, we get : 

maxShares = (type(uint104).ma0x)*totalSupply*(DECIMALS-COMISSION_FEE)/DECIMALS*totalAssets()

The derived formula does not match the formula used in maxMint() leading to incorrect calculation of shares.

Tools Used

Manual Review

Recommended Mitigation Steps

-            return (convertToShares(type(uint104).max) * DECIMALS) / (DECIMALS + COMMISSION_FEE);
+            return (convertToShares(type(uint104).max) * (DECIMALS - COMMISSION_FEE)) / DECIMALS;


## Assessed type

Error

[c4-judge]

Picodes marked the issue as duplicate of #553

[c4-judge]

Picodes marked the issue as not a duplicate

[c4-judge]

Picodes marked the issue as primary issue

[dyedm1]

actually is dup #553 , conf'd there

[c4-judge]

Picodes marked the issue as duplicate of #553

[c4-judge]

Picodes marked the issue as satisfactory

[c4-judge]

Picodes changed the severity to QA (Quality Assurance)

[c4-judge]

Picodes marked the issue as grade-b