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[M-03] DoS Attack on Swapping via Permit2 Possible #1016

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[M-03] DoS Attack on Swapping via Permit2 Possible #1016

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4 changes: 4 additions & 0 deletions contracts/SpokePoolPeriphery.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ contract SwapProxy is Lockable {
// Errors
error SwapFailed();
error UnsupportedTransferType();
error InvalidExchange();

/**
* @notice Constructs a new SwapProxy.
Expand Down Expand Up @@ -72,6 +73,9 @@ contract SwapProxy is Lockable {
SpokePoolPeripheryInterface.TransferType transferType,
bytes calldata routerCalldata
) external nonReentrant returns (uint256 outputAmount) {
// Prevent nonce invalidation attack by disallowing exchange to be the permit2 address
if (exchange == address(permit2)) revert InvalidExchange();

// We'll return the final balance of output tokens

// The exchange will either receive funds from this contract via:
Expand Down
29 changes: 28 additions & 1 deletion test/evm/foundry/local/SpokePoolPeriphery.t.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ pragma solidity ^0.8.0;
import { Test } from "forge-std/Test.sol";

import { SpokePoolVerifier } from "../../../../contracts/SpokePoolVerifier.sol";
import { SpokePoolPeriphery } from "../../../../contracts/SpokePoolPeriphery.sol";
import { SpokePoolPeriphery, SwapProxy } from "../../../../contracts/SpokePoolPeriphery.sol";
import { Ethereum_SpokePool } from "../../../../contracts/Ethereum_SpokePool.sol";
import { V3SpokePoolInterface } from "../../../../contracts/interfaces/V3SpokePoolInterface.sol";
import { SpokePoolPeripheryInterface } from "../../../../contracts/interfaces/SpokePoolPeripheryInterface.sol";
Expand Down Expand Up @@ -1277,6 +1277,33 @@ contract SpokePoolPeripheryTest is Test {
);
}

/**
* Security tests
*/
function testSwapAndBridgeBlocksPermit2AsExchange() public {
// This test verifies that the fix prevents using permit2 as the exchange address
// which would allow DoS attacks via invalidateNonces
vm.startPrank(depositor);

// Attempt to use permit2 as the exchange - this should fail with InvalidExchange
vm.expectRevert(SwapProxy.InvalidExchange.selector);
spokePoolPeriphery.swapAndBridge(
_defaultSwapAndDepositData(
address(mockWETH),
mintAmount,
0,
address(0),
Exchange(address(permit2)), // Using permit2 as exchange should fail
SpokePoolPeripheryInterface.TransferType.Permit2Approval,
address(mockERC20),
depositAmount,
depositor,
true
)
);
vm.stopPrank();
}

/**
* Helper functions
*/
Expand Down
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