RabbitHole Quest Protocol contest - __141345__'s results

Lines of code

https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/QuestFactory.sol#L219-L229

Vulnerability details

Impact

If the some quest is created for multiple chain, the signature could be replayed. When the task requires certain amount of resources such as staking, the signature replay could trick the system, getting the rewards without doing the work and spending the cost.

Proof of Concept

Imagine, some quest is created for multiple chain, Ethereum, Polygon and BSC, and the task is similar on each chain, staking 1000 USDC for 3 month. As soon as the user finishes the task on Ethereum by taking 1000 USDC, the signature could be generated by the claimSigner/indexer. Then even if no USDC is staked on Polygon and BSC, the same signature could still be applied to mint the receipt and claim the rewards.

In mintReceipt(), the chainid is not included, only the msg.sender and questId. Which means the same signature could be used for different chains multiple times, without the quest being performed.

File: quest-protocol/contracts/QuestFactory.sol
219:     function mintReceipt(string memory questId_, bytes32 hash_, bytes memory signature_) public {
220:         if (quests[questId_].numberMinted + 1 > quests[questId_].totalParticipants) revert OverMaxAllowedToMint();
221:         if (quests[questId_].addressMinted[msg.sender] == true) revert AddressAlreadyMinted();
222:         if (keccak256(abi.encodePacked(msg.sender, questId_)) != hash_) revert InvalidHash();
223:         if (recoverSigner(hash_, signature_) != claimSignerAddress) revert AddressNotSigned();
224: 
225:         quests[questId_].addressMinted[msg.sender] = true;
226:         quests[questId_].numberMinted++;
227:         emit ReceiptMinted(msg.sender, questId_);
228:         rabbitholeReceiptContract.mint(msg.sender, questId_);
229:     }

Tools Used

Manual analysis.

Recommended Mitigation Steps

Include the chain id in the signed hash in mintReceipt(). And the signature from the claimSigner/indexer need to add this info also.

File: quest-protocol/contracts/QuestFactory.sol
219:     function mintReceipt(string memory questId_, bytes32 hash_, bytes memory signature_) public {

-222:         if (keccak256(abi.encodePacked(msg.sender, questId_)) != hash_) revert InvalidHash();
+222:         if (keccak256(abi.encodePacked(msg.sender, chainid(), questId_)) != hash_) revert InvalidHash();