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

People can choose themselves as their own Soulmate.

shaflow01

Summary

People can choose themselves as their own Soulmate.

Vulnerability Details

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)) {
require(soulmate1!=msg.sender);
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++);
}
​
return ownerToId[msg.sender];
}

After a person successfully sets soulmate1, they can immediately call again to set themselves as soulmate2.

The reason for this is a lack of checks

require(soulmate1!=msg.sender);

This would result in an inaccurate calculation of totalSouls().

function totalSouls() external view returns (uint256) {
return nextID * 2;
}

Impact

People can choose themselves as their own Soulmate.
POC

function test_MintNewToken() public {
uint tokenIdMinted = 0;
​
vm.startPrank(soulmate1);
soulmateContract.mintSoulmateToken();
soulmateContract.mintSoulmateToken();
assertTrue(soulmateContract.totalSupply() == 1);
assertTrue(soulmateContract.soulmateOf(soulmate1) == soulmate1);
assertTrue(soulmateContract.ownerToId(soulmate1) == tokenIdMinted);
vm.stopPrank();
​
}
​

result

[PASS] test_MintNewToken() (gas: 180912)
Traces:
[180912] SoulmateTest::test_MintNewToken()
├─ [0] VM::startPrank(soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f])
│ └─ ← ()
├─ [33015] Soulmate::mintSoulmateToken()
│ ├─ emit SoulmateIsWaiting(soulmate: soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f])
│ └─ ← 0
├─ [133343] Soulmate::mintSoulmateToken()
│ ├─ emit SoulmateAreReunited(soulmate1: soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f], soulmate2: 0x0000000000000000000000000000000000000000, tokenId: 0)
│ ├─ emit Transfer(from: 0x0000000000000000000000000000000000000000, to: soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f], id: 0)
│ └─ ← 0
├─ [393] Soulmate::totalSupply() [staticcall]
│ └─ ← 1
├─ [624] Soulmate::soulmateOf(soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f]) [staticcall]
│ └─ ← soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f]
├─ [607] Soulmate::ownerToId(soulmate1: [0x65629adcc2F9C857Aeb285100Cc00Fb41E78DC2f]) [staticcall]
│ └─ ← 0
├─ [0] VM::stopPrank()
│ └─ ← ()
└─ ← ()
​
Test result: ok. 1 passed; 0 failed; 0 skipped; finished in 1.76ms

Tools Used

Manual Review

Recommendations

else if (soulmate2 == address(0)) {
​
require(soulmate1!=msg.sender);
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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