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

LikeRegistry Fails To Credit User Deposits Resulting In Permanent Reward Loss

yashkhare9815

High: LikeRegistry Fails To Credit User Deposits Resulting In Permanent Reward Loss

Description

  • The intended protocol behavior is that users deposit ETH while liking another profile, and matched users later receive pooled rewards through a multisig wallet after protocol fees are deducted.

  • However, the deposited ETH is never credited to userBalances[msg.sender].

  • During matching, the protocol reads balances from userBalances, which remain zero for all users.

  • As a result, matched users receive zero rewards while all deposited ETH remains trapped inside the contract.

// Root cause in the codebase with @> marks to highlight the relevant section
​
function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
​
// @> Missing accounting of deposited ETH
// userBalances[msg.sender] += msg.value;
​
likes[msg.sender][liked] = true;
​
if (likes[liked][msg.sender]) {
matchRewards(liked, msg.sender);
}
}
​
function matchRewards(address from, address to) internal {
// @> Always reads zero balances
uint256 matchUserOne = userBalances[from];
uint256 matchUserTwo = userBalances[to];
​
uint256 totalRewards = matchUserOne + matchUserTwo;
}

Risk

Likelihood:

  • Every successful likeUser() call accepts ETH deposits.

  • Every successful match executes reward distribution using zero-valued balances.

Impact:

  • Matched users receive zero rewards.

  • Deposited ETH becomes permanently trapped in the registry contract.

  • Protocol reward logic and fee distribution become non-functional.

Proof of Concept

By adding the a test case to simulate the likeRegistry we can , see that the user1 and user2 balance are zero.

function setUp() public {
soulboundNFT = new SoulboundProfileNFT();
vm.prank(owner);
likeRegistry = new LikeRegistry(address(soulboundNFT));
}
​
function testMatchedUsersReceiveZeroRewards() public {
vm.deal(user, 2 ether);
vm.deal(user2, 2 ether);
​
vm.prank(user);
soulboundNFT.mintProfile("Alice", 25, "ipfs://alice");
​
vm.prank(user2);
soulboundNFT.mintProfile("Bob", 26, "ipfs://bob");
​
vm.prank(user);
likeRegistry.likeUser{value: 1 ether}(user2);
​
vm.prank(user2);
likeRegistry.likeUser{value: 1 ether}(user);
​
// Entire 2 ETH remains trapped inside registry
assertEq(address(likeRegistry).balance, 2 ether);
​
// User balances were never credited
assertEq(likeRegistry.userBalances(user), 0);
assertEq(likeRegistry.userBalances(user2), 0);
}

Recommended Mitigation

By updating the userBalance in likeUser we can mitigate this issue.

function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
​
+ userBalances[msg.sender] += msg.value;
​
likes[msg.sender][liked] = true;
}
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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