Snowman Merkle Airdrop
AI First Flight #10
Beginner FriendlyFoundrySolidityNFT
EXP
View results
Previous Next
Submission Details
Severity: high
Valid

SnowmanAirdrop::MESSAGE_TYPEHASH has typo "addres" instead of "address" - all EIP-712 signatures always fail

palsudhanshuxcodes

Root + Impact: // src/SnowmanAirdrop.sol:49
bytes32 private constant MESSAGE_TYPEHASH =
@> keccak256("AirdropClaim(address account,uint256 amount)");
@> // BUG: Actually code has "addres" - missing one 's'
@> // Real code: keccak256("AirdropClaim(addres account,uint256 amount)");

Description: MESSAGE_TYPEHASH typo breaks EIP-712 signature verification for all users

// Root cause in the codebase with @> marks to highlight the relevant section
EIP-712 typehash must exactly match the type string used by off-chain signer. Here contract uses "addres" instead of "address".
​
Because of this one-letter typo, keccak256 hash is completely different. Any signature created by a correct wallet / frontend using "address" will NEVER match the contract's digest. So claimSnowman() will always revert on signature check.
​
Result: No legit user can ever claim. Whole airdrop is bricked / DoS.
EIP-712 typehash must exactly match the type string used by off-chain signer. Here contract uses "addres" instead of "address".
​
Because of this one-letter typo, keccak256 hash is completely different. Any signature created by a correct wallet / frontend using "address" will NEVER match the contract's digest. So claimSnowman() will always revert on signature check.
​
Result: No legit user can ever claim. Whole airdrop is bricked / DoS.

Risk

Likelihood:High - Typo is in constant code, it will trigger for 100% of claims. Every single user who tries to claim with a correctly formed EIP-712 signature will fail. Not a rare edge case.

Impact:High - Core protocol function claimSnowman is completely broken. Users cannot claim NFTs, their Snow remains locked / unusable, airdrop distribution fails. Protocol needs redeploy to fix.

Proof of Concept:PoC: Correct EIP-712 signature always reverts due to MESSAGE_TYPEHASH typo

## Proof of Concept - Explanation
​
Flow:
1. User signs off-chain with correct type: "AirdropClaim(address account,uint256 amount)"
2. Contract computes digest with wrong type: "AirdropClaim(addres account,uint256 amount)"
3. ECDSA.recover returns wrong signer because digest is different
4. require(signer == receiver) fails -> claim reverts
​
How to run:
- Sign message with correct EIP-712 domain in test
- Call claimSnowman with that valid signature
- Expected: Should succeed, but it REVERTS
​
Supporting Code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
import {Test} from "forge-std/Test.sol";
import {SnowmanAirdrop} from "../src/SnowmanAirdrop.sol";
import {Snowman} from "../src/Snowman.sol";
import {Snow} from "../src/Snow.sol";
​
contract TypoTest is Test {
function test_SignatureAlwaysFailsDueToTypo() public {
bytes32 correctTypehash = keccak256("AirdropClaim(address account,uint256 amount)");
bytes32 contractTypehash = keccak256("AirdropClaim(addres account,uint256 amount)");
assertTrue(correctTypehash != contractTypehash);
// Hashes are different, so signatures will never match
}
}

Recommended Mitigation:Mitigation: Fix typo "addres" -> "address" in MESSAGE_TYPEHASH and redeploy

- remove this code
+ add this code
## Recommended Mitigation - Detailed Explanation
​
Root Cause: Single letter typo in MESSAGE_TYPEHASH string - "addres" instead of "address".
​
Why this fix works: EIP-712 requires exact string match between signer and verifier. Fixing typo makes contract hash identical to wallet hash, so ECDSA recovery returns correct signer.
​
Step 1 - Fix the typo in SnowmanAirdrop.sol:
Change keccak256("AirdropClaim(addres account,uint256 amount)") to keccak256("AirdropClaim(address account,uint256 amount)")
​
Step 2 - Add test for EIP-712:
Add a test that signs with correct domain and calls claimSnowman, it should succeed after fix. Before fix it reverts.
​
Step 3 - Redeploy:
Typehash is a constant, it cannot be changed after deployment. So fixed contract must be redeployed and Merkle root + Snow token must be re-linked.
​
After Fix Verification:
- User signs with "address" type -> claimSnowman succeeds
- Attacker with wrong signature still reverts
​
Supporting Code for Fix:
// Before:
bytes32 private constant MESSAGE_TYPEHASH = keccak256("AirdropClaim(addres account,uint256 amount)");
// After:
bytes32 private constant MESSAGE_TYPEHASH = keccak256("AirdropClaim(address account,uint256 amount)");
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 24 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)"); ```

Support

FAQs

Can't find an answer? Chat with us on Discord, Twitter or Linkedin.

Give us feedback!