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

likeUser never updates balance

wilddream402

Root + Impact

Description

  • When users send a Like to another user they also pay at least 1 ETH which accumulates in userBalances so they can receive it later as part of their multisig wallet.

  • userBalances is never updated when the ETH is received so it's always zero, if two people match they will get a multisig wallet with 0 funds.

// Function marked as payable
@> 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 accepted but ETH is never added to userBalance
@> 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);
}
}

Risk

Likelihood:

  • This is a main functionality of the Smart Contract so the likelihood is very high.

Impact:

  • The impact is high as the users will always get a zero fund multisig wallet.

  • The impact is high as the contract owner depends userBalances to take a 10% fee and be able to withdraw the ETH on the contract.

Proof of Concept

The proof of concept provided is a test that fails on the assert of the userBalances being equal or greater than 1 Ether immediately after liking a profile, showing that the userBalance is not being updated at any time.

function testLikeUserBalance() public {
vm.prank(user);
soulboundNFT.mintProfile("Alice", 25, "ipfs://profileImage");
​
vm.prank(user2);
soulboundNFT.mintProfile("Bob", 26, "ipfs://profileImage");
​
vm.deal(user, 1 ether);
vm.prank(user);
likes.likeUser{value: 1 ether}(user2);
assertTrue(likes.userBalances(user) >= 1 ether);
​
vm.deal(user2, 1 ether);
vm.prank(user2);
likes.likeUser{value: 1 ether}(user);
assertTrue(likes.userBalances(user2) >= 1 ether);
}

Recommended Mitigation

The mitigation would consist of adding a line of code adding the msg.value to the userBalances.

// Function marked as payable
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 accepted but ETH is never added to userBalance
likes[msg.sender][liked] = true;
emit Liked(msg.sender, liked);
​
+ 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);
}
}
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 2 hours 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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