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

ETH Is Collected but Never Credited to userBalances

cryptostellar5

Root + Impact

Description

Users send ETH when liking another user, but the contract never records this ETH in userBalances. As a result, all ETH sent is permanently lost and never distributed as rewards.

function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
...
// userBalances[msg.sender] is never incremented
}
​

likeUser() is payable, but never updates userBalances[msg.sender].

Risk

Likelihood:

This happens on every single call to likeUser().

Impact:

  • All ETH sent by users is lost

  • matchRewards() distributes 0 ETH

  • Protocol cannot function economically

  • Users permanently lose funds

Proof of Concept

Add the following setup

contract SoulboundProfileNFTTest is Test {
SoulboundProfileNFT soulboundNFT;
+ LikeRegistry likeregistry;
address user = address(0x123);
address user2 = address(0x456);
address owner = address(this); // Test contract acts as the owner
​
function setUp() public {
soulboundNFT = new SoulboundProfileNFT();
+ likeregistry = new LikeRegistry(address(soulboundNFT));
}
..
}
​

The following POC confirms that the user balance is reduced and the contract receives the ETH, however the userbalances mapping is not updated

function testETHNotCredited() public {
​
vm.prank(user);
soulboundNFT.mintProfile("Alice", 25, "ipfs://profileImage");
​
vm.prank(user2);
soulboundNFT.mintProfile("Bob", 25, "ipfs://profileImage");
​
uint256 tokenId = soulboundNFT.profileToToken(user);
vm.deal(user, 2 ether);
vm.deal(user2, 2 ether);
​
vm.prank(user);
likeregistry.likeUser{value: 1 ether}(user2);
​
assertEq(likeregistry.userBalances(user), 0);
assertEq(address(likeregistry).balance, 1 ether);
}
​

Recommended Mitigation

  • Use per-pair escrow:
    mapping(address => mapping(address => uint256)) stakes;

  • Track ETH per like, not globally

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);
}
}
+ userBalances[msg.sender] += msg.value;
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 2 days 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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