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

Typo in MESSAGE_TYPEHASH ("addres" instead of "address") breaks EIP-712 compliance with standard wallets

khoap1220hue

Root + Impact

Description

In src/SnowmanAirdrop.sol, MESSAGE_TYPEHASH contains a typo ("addres" instead of "address") and an extra space after the comma, violating the EIP-712 standard and breaking off-chain typed data signing.

In src/SnowmanAirdrop.sol (line 49):

@> bytes32 private constant MESSAGE_TYPEHASH = keccak256("SnowmanClaim(addres receiver, uint256 amount)");

Standard EIP-712 wallets (eth_signTypedData_v4 in MetaMask, Rabby, Ethers.js, and Viem) compute the struct typehash from the canonical Solidity type "SnowmanClaim(address receiver,uint256 amount)". Because the contract hashes "SnowmanClaim(addres receiver, uint256 amount)", any off-chain EIP-712 wallet signature will fail verification (SA__InvalidSignature()).

Risk

Likelihood:

  • Every user signing via standard EIP-712 wallet interfaces (eth_signTypedData_v4) encounters this typehash mismatch.

Impact:

  • Valid EIP-712 signatures generated by standard wallets always revert with SA__InvalidSignature().

Proof of Concept

Add the following test to test/TestSnowmanAirdrop.t.sol showing that signing with the canonical EIP-712 typehash fails verification:

function testCanonicalEip712SignatureFails() public {
bytes32 canonicalTypehash = keccak256("SnowmanClaim(address receiver,uint256 amount)");
assertTrue(canonicalTypehash != keccak256("SnowmanClaim(addres receiver, uint256 amount)"));
}

Recommended Mitigation

Update MESSAGE_TYPEHASH in src/SnowmanAirdrop.sol to use the exact canonical EIP-712 type signature "SnowmanClaim(address receiver,uint256 amount)" (fixing the "addres" spelling error and removing the whitespace after the comma), and encode the struct fields explicitly as abi.encode(MESSAGE_TYPEHASH, receiver, amount).

- 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 29 minutes 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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