Users can mint more tokens compared to what its allowed to mint

[c4-submissions]

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/smart-contracts/MinterContract.sol#L234-L237

Vulnerability details

Impact

An allowlist address can mint more tokens than what it is allowed to mint and any address during the public phase can mint more tokens compared to what its allowed to mint (maxCollectionPurchases) due to reentrancy into the NextGenMinterContract.mint function.

Proof of Concept

Suppose a user is allowed to mint 3 tokens. Then the user calls the NextGenMinterContract.mint function with _numberOfTokens equals 3. When the protocol makes the onERC721Received invoke from the _safeMint the user reenters into the NextGenMinterContract.mint function with _numberOfTokens equals 2 and on the next step 1. The condition will be true for every call:

213                require(_maxAllowance >= gencore.retrieveTokensMintedALPerAddress(col, _delegator) + _numberOfTokens, "AL limit");

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/smart-contracts/MinterContract.sol#L213
After the last reentrance call is executed the previous call continues minting remaining tokens in the loop:

        for(uint256 i = 0; i < _numberOfTokens; i++) {
            uint256 mintIndex = gencore.viewTokensIndexMin(col) + gencore.viewCirSupply(col);
            gencore.mint(mintIndex, mintingAddress, _mintTo, tokData, _saltfun_o, col, phase);
        }

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/smart-contracts/MinterContract.sol#L234-L237
This way the user receives 6 tokens instead of allowed 3.

The same attack can be provided to mint more tokens during the public phase.

Tools Used

Manual review

Recommended Mitigation Steps

Consider using the nonReentrant modifier to prevent reentrancy in the mint function.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
contract ReEntrancyGuard {
    bool internal locked;
    modifier noReentrant() {
        require(!locked, "No re-entrancy");
        locked = true;
        _;
        locked = false;
    }
}

Assessed type

Reentrancy

[c4-pre-sort]

141345 marked the issue as duplicate of #51

[c4-pre-sort]

141345 marked the issue as duplicate of #1742

[c4-judge]

alex-ppg marked the issue as satisfactory

[c4-judge]

alex-ppg marked the issue as partial-50

[c4-judge]

alex-ppg marked the issue as satisfactory