Snowman Merkle Airdrop
AI First Flight #10
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Submission Details
Severity: high
Valid

[M-1] The MESSAGE_TYPEHASH contains a typo causing non-standard EIP-712 implementation and integration fragility

marina_ciuperca

Root + Impact

Description

  • The MESSAGE_TYPEHASH constant in SnowmanAirdrop.sol contains a typo: addres instead of address. While the contract will still function internally, this creates a non-standard EIP-712 type hash that deviates from the expected format.

bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(addres receiver, uint256 amount)");
//^^^^^^^ TYPO!

Risk

Likelihood - High:

  • Every user attempting to claim will encounter this issue when using standard EIP-712 tooling

100% reproducible with any properly implemented off-chain signing library

  • Will immediately break integration attempts

Impact - Medium:

  • Off-chain tools and integrations expecting standard EIP-712 types will fail

Frontend developers must implement the same typo in their signing logic

  • Wallet interfaces may display confusing or incorrect type information to users

  • Any third-party integration attempting to verify signatures will fail unless they replicate the exact typo

Proof of Concept

  1. Deploy the contract with the current typo

  2. Attempt to generate a signature using standard EIP-712 libraries with correct spelling.

  3. The signature will be invalid because the type hash computed off-chain won't match the contract's type hash

  4. Only by replicating the typo (type: 'addres') will signatures validate correctly.


​
const types = {
SnowmanClaim: [
{ name: 'receiver', type: 'address' }, // Correct spelling
{ name: 'amount', type: 'uint256' }
]
};

Recommended Mitigation

Fix the typo to use the standard address type:

- bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(addres receiver, uint256 amount)");
+ bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(address receiver, uint256 amount)");
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 5 hours ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-02] Unconsistent `MESSAGE_TYPEHASH` with standart EIP-712 declaration on contract `SnowmanAirdrop`

# Root + Impact ## Description * Little typo on `MESSAGE_TYPEHASH` Declaration on `SnowmanAirdrop` contract ```Solidity // src/SnowmanAirdrop.sol 49: bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(addres receiver, uint256 amount)"); ``` **Impact**: * `function claimSnowman` never be `TRUE` condition ## Proof of Concept Applying this function at the end of /test/TestSnowmanAirdrop.t.sol to know what the correct and wrong digest output HASH. Ran with command: `forge test --match-test testFrontendSignatureVerification -vvvv` ```Solidity function testFrontendSignatureVerification() public { // Setup Alice for the test vm.startPrank(alice); snow.approve(address(airdrop), 1); vm.stopPrank(); // Simulate frontend using the correct format bytes32 FRONTEND_MESSAGE_TYPEHASH = keccak256("SnowmanClaim(address receiver, uint256 amount)"); // Domain separator used by frontend (per EIP-712) bytes32 DOMAIN_SEPARATOR = keccak256( abi.encode( keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"), keccak256("Snowman Airdrop"), keccak256("1"), block.chainid, address(airdrop) ) ); // Get Alice's token amount uint256 amount = snow.balanceOf(alice); // Frontend creates hash using the correct format bytes32 structHash = keccak256( abi.encode( FRONTEND_MESSAGE_TYPEHASH, alice, amount ) ); // Frontend creates the final digest (per EIP-712) bytes32 frontendDigest = keccak256( abi.encodePacked( "\x19\x01", DOMAIN_SEPARATOR, structHash ) ); // Alice signs the digest created by the frontend (uint8 v, bytes32 r, bytes32 s) = vm.sign(alKey, frontendDigest); // Digest created by the contract (with typo) bytes32 contractDigest = airdrop.getMessageHash(alice); // Display both digests for comparison console2.log("Frontend Digest (correct format):"); console2.logBytes32(frontendDigest); console2.log("Contract Digest (with typo):"); console2.logBytes32(contractDigest); // Compare the digests - they should differ due to the typo assertFalse( frontendDigest == contractDigest, "Digests should differ due to typo in MESSAGE_TYPEHASH" ); // Attempt to claim with the signature - should fail vm.prank(satoshi); vm.expectRevert(SnowmanAirdrop.SA__InvalidSignature.selector); airdrop.claimSnowman(alice, AL_PROOF, v, r, s); assertEq(nft.balanceOf(alice), 0); } ``` ## Recommended Mitigation on contract `SnowmanAirdrop` Line 49 applying this: ```diff - bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(addres receiver, uint256 amount)"); + bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(address receiver, uint256 amount)"); ```

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