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

Critical: User Balances Never Updated - Funds Lost on Match

paktiko

Root + Impact

Description

The likeUser function accepts ETH payments but never updates the userBalances mapping. When users match, the matchRewards function reads from userBalances which will always be 0, resulting in no funds being transferred to the MultiSig wallet. The ETH sent by users remains stuck in the LikeRegistry contract with no way to recover it except through the owner's withdrawFees function (which only withdraws fees, not user funds).

function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
require(!likes[msg.sender][liked], "Already liked");
require(msg.sender != liked, "Cannot like yourself");
require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT");
require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT");
​
likes[msg.sender][liked] = true;
emit Liked(msg.sender, liked);
// MISSING: userBalances[msg.sender] += msg.value;
​
// Check if mutual like
if (likes[liked][msg.sender]) {
matches[msg.sender].push(liked);
matches[liked].push(msg.sender);
emit Matched(msg.sender, liked);
matchRewards(liked, msg.sender);
}
}

Risk

Impact:
All ETH sent by users when liking others becomes permanently locked in the contract. When users match, they receive an empty MultiSig wallet with 0 funds, while their actual ETH remains inaccessible in the LikeRegistry contract. This affects every user of the platform and results in 100% loss of user funds.

Proof of Concept

// Step 1: Alice and Bob create profiles
alice.mintProfile("Alice", 25, "ipfs://alice");
bob.mintProfile("Bob", 28, "ipfs://bob");
​
// Step 2: Alice likes Bob with 1 ETH
alice.likeUser{value: 1 ether}(bob);
// userBalances[alice] is still 0, but contract has 1 ETH
​
// Step 3: Bob likes Alice with 1 ETH
bob.likeUser{value: 1 ether}(alice);
// userBalances[bob] is still 0, but contract has 2 ETH
// Match occurs, matchRewards is called
​
// Step 4: In matchRewards:
// matchUserOne = userBalances[alice] = 0
// matchUserTwo = userBalances[bob] = 0
// totalRewards = 0 + 0 = 0
// MultiSig wallet receives 0 ETH
​
// Result: 2 ETH stuck in LikeRegistry, users have empty MultiSig

Recommended Mitigation

function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
require(!likes[msg.sender][liked], "Already liked");
require(msg.sender != liked, "Cannot like yourself");
require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT");
require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT");
​
// FIX: Update user balance with the sent ETH
userBalances[msg.sender] += msg.value;
likes[msg.sender][liked] = true;
emit Liked(msg.sender, liked);
​
// Check if mutual like
if (likes[liked][msg.sender]) {
matches[msg.sender].push(liked);
matches[liked].push(msg.sender);
emit Matched(msg.sender, liked);
matchRewards(liked, msg.sender);
}
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 1 day ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-01] After the user calls the `likeUser` function, the userBalance does not increase by the corresponding value.

## Description User A calls `likeUser` and sends `value > 1` ETH. According to the design of DatingDapp, the amount for user A should be accumulated by `userBalances`. Otherwise, in the subsequent calculations, the balance for each user will be 0. ## Vulnerability Details When User A calls `likeUser`, the accumulation of `userBalances` is not performed. ```solidity function likeUser( address liked ) external payable { require(msg.value >= 1 ether, "Must send at least 1 ETH"); require(!likes[msg.sender][liked], "Already liked"); require(msg.sender != liked, "Cannot like yourself"); require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT"); require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT"); likes[msg.sender][liked] = true; emit Liked(msg.sender, liked); // Check if mutual like if (likes[liked][msg.sender]) { matches[msg.sender].push(liked); matches[liked].push(msg.sender); emit Matched(msg.sender, liked); matchRewards(liked, msg.sender); } } ``` This will result in `totalRewards` always being 0, affecting all subsequent calculations: ```solidity uint256 totalRewards = matchUserOne + matchUserTwo; uint256 matchingFees = (totalRewards * FIXEDFEE ) / 100; uint256 rewards = totalRewards - matchingFees; totalFees += matchingFees; ``` ## POC ```solidity function testUserBalanceshouldIncreaseAfterLike() public { vm.prank(user1); likeRegistry.likeUser{value: 20 ether}(user2); assertEq(likeRegistry.userBalances(user1), 20 ether, "User1 balance should be 20 ether"); } ``` Then we will get an error: ```shell [FAIL: User1 balance should be 20 ether: 0 != 20000000000000000000] ``` ## Impact - Users will be unable to receive rewards. - The contract owner will also be unable to withdraw ETH from the contract. ## Recommendations Add processing for `userBalances` in the `likeUser` function: ```diff function likeUser( address liked ) external payable { require(msg.value >= 1 ether, "Must send at least 1 ETH"); require(!likes[msg.sender][liked], "Already liked"); require(msg.sender != liked, "Cannot like yourself"); require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT"); require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT"); likes[msg.sender][liked] = true; + userBalances[msg.sender] += msg.value; emit Liked(msg.sender, liked); [...] } ```

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