First Flight #9: Soulmate
First Flight #9
Beginner FriendlyFoundryNFT
100 EXP
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Submission Details
Severity: medium
Valid

A user can mint a soulbound token with its same address as soulmate

ceseshi

Summary

A user can mint a soulbound token with the same address as soulmate1 and soulmate2.

Vulnerability Details

The mintSoulmateToken() function does not check if the user is already minting as soulmate1, so if he calls mintSoulmateToken() again, he will mint a soulbound token with the same address as soulmate2.

This test mints a soulbound token with the same address as soulmate1 and soulmate2.

function testMintSoulmateTokenSameAddress() public {
vm.startPrank(soulmate1);
soulmateContract.mintSoulmateToken();
soulmateContract.mintSoulmateToken();
​
console2.log(soulmate1);
console2.log(soulmateContract.soulmateOf(soulmate1));
}

soulmate1 and soulmateOf(soulmate1) are the same.

Running 1 test for test/unit/AuditTest1.t.sol:AuditTest1
[PASS] testMintSoulmateTokenSameAddress() (gas: 181670)
Logs:
0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f
0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f

Impact

Users can mint soulbound tokens as singles and alter the functionality of the contract.

Tools Used

Foundry, Manual review

Recommendations

Fix mintSoulmateToken() in Soulmate.sol

+error Soulmate__alreadyMinting();
...
​
function mintSoulmateToken() public returns (uint256) {
// Check if people already have a soulmate, which means already have a token
address soulmate = soulmateOf[msg.sender];
if (soulmate != address(0))
revert Soulmate__alreadyHaveASoulmate(soulmate);
​
address soulmate1 = idToOwners[nextID][0];
address soulmate2 = idToOwners[nextID][1];
if (soulmate1 == address(0)) {
idToOwners[nextID][0] = msg.sender;
ownerToId[msg.sender] = nextID;
emit SoulmateIsWaiting(msg.sender);
} else if (soulmate2 == address(0)) {
+ if(soulmate1 == msg.sender) revert Soulmate__alreadyMinting();
idToOwners[nextID][1] = msg.sender;
// Once 2 soulmates are reunited, the token is minted
ownerToId[msg.sender] = nextID;
soulmateOf[msg.sender] = soulmate1;
soulmateOf[soulmate1] = msg.sender;
idToCreationTimestamp[nextID] = block.timestamp;
​
emit SoulmateAreReunited(soulmate1, soulmate2, nextID);
​
_mint(msg.sender, nextID++);
}
Updates

Lead Judging Commences

0xnevi Lead Judge over 1 year ago
Submission Judgement Published
Validated
Assigned finding tags:

finding-self-soulmate

- Given the native anonymous nature of blockchain in general, this issue cannot be avoided unless an explicit whitelist is implemented. Even then we can only confirm soulmates are distinct individuals via kyc. I believe finding a soulmate is intended to be permisionless. - However, even though sufficient (500_000_000e18 in each vault) tokens are minted to claim staking and airdrop rewards, it would take 500_000_000 / 2 combined weeks for airdrop vault to be drained which is not unreasonable given there are [80+ million existing wallets](https://coinweb.com/trends/how-many-crypto-wallets-are-there/). Given there is no option to mint new love tokens, this would actually ruin the functionality of the protocol of finding soulmates and shift the focus to abusing a sybil attack to farming airdrops instead. Assigning medium severity for now but am open for appeals otherwise, since most if not all issues lack indepth analysis of the issue.

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