S-162 Prevent frontrunning permit DOSing intent

.gas-snapshot

@@ -6,47 +6,48 @@ DelegatecallGuardTest:test_direct_call_reverts_NotDelegateCall() (gas: 8420)
 DelegatecallGuardTest:test_multiple_delegatecall_guards() (gas: 298825)
 DelegatecallGuardTest:test_onlyDelegatecall_modifier_usage() (gas: 98867)
 DelegatecallGuardTest:test_self_address_immutable() (gas: 2877)
-TrailsIntentEntrypointDeploymentTest:test_DeployIntentEntrypoint_SameAddress() (gas: 839567)
-TrailsIntentEntrypointDeploymentTest:test_DeployIntentEntrypoint_Success() (gas: 832067)
-TrailsIntentEntrypointDeploymentTest:test_DeployedIntentEntrypoint_HasCorrectConfiguration() (gas: 834866)
-TrailsIntentEntrypointTest:testAssemblyCodeExecution() (gas: 89228)
-TrailsIntentEntrypointTest:testConstructor() (gas: 3287)
-TrailsIntentEntrypointTest:testConstructorAndDomainSeparator() (gas: 7684)
+TrailsIntentEntrypointDeploymentTest:test_DeployIntentEntrypoint_SameAddress() (gas: 833102)
+TrailsIntentEntrypointDeploymentTest:test_DeployIntentEntrypoint_Success() (gas: 825615)
+TrailsIntentEntrypointDeploymentTest:test_DeployedIntentEntrypoint_HasCorrectConfiguration() (gas: 828414)
+TrailsIntentEntrypointTest:testAssemblyCodeExecution() (gas: 89250)
+TrailsIntentEntrypointTest:testConstructor() (gas: 3309)
+TrailsIntentEntrypointTest:testConstructorAndDomainSeparator() (gas: 7706)
 TrailsIntentEntrypointTest:testDepositToIntentAlreadyUsed() (gas: 114117)
-TrailsIntentEntrypointTest:testDepositToIntentCannotReuseDigest() (gas: 94757)
-TrailsIntentEntrypointTest:testDepositToIntentExpiredDeadline() (gas: 56029)
+TrailsIntentEntrypointTest:testDepositToIntentCannotReuseDigest() (gas: 94779)
+TrailsIntentEntrypointTest:testDepositToIntentExpiredDeadline() (gas: 56051)
 TrailsIntentEntrypointTest:testDepositToIntentReentrancyProtection() (gas: 114095)
-TrailsIntentEntrypointTest:testDepositToIntentRequiresNonZeroAmount() (gas: 27371)
-TrailsIntentEntrypointTest:testDepositToIntentRequiresValidToken() (gas: 30754)
-TrailsIntentEntrypointTest:testDepositToIntentTransferFromFails() (gas: 58387)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitAlreadyUsed() (gas: 132693)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitExpiredDeadline() (gas: 36459)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitReentrancyProtection() (gas: 124115)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresNonZeroAmount() (gas: 35173)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresPermitAmount() (gas: 60742)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresValidToken() (gas: 35899)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitTransferFromFails() (gas: 59993)
-TrailsIntentEntrypointTest:testDepositToIntentWithPermitWrongSigner() (gas: 40450)
-TrailsIntentEntrypointTest:testDepositToIntentWithoutPermit_RequiresIntentAddress() (gas: 31441)
+TrailsIntentEntrypointTest:testDepositToIntentRequiresNonZeroAmount() (gas: 27393)
+TrailsIntentEntrypointTest:testDepositToIntentRequiresValidToken() (gas: 30776)
+TrailsIntentEntrypointTest:testDepositToIntentTransferFromFails() (gas: 58409)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitAlreadyUsed() (gas: 132684)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitExpiredDeadline() (gas: 36472)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitReentrancyProtection() (gas: 124106)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresNonZeroAmount() (gas: 35186)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresPermitAmount() (gas: 60755)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitRequiresValidToken() (gas: 35912)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitTransferFromFails() (gas: 59984)
+TrailsIntentEntrypointTest:testDepositToIntentWithPermitWrongSigner() (gas: 40463)
+TrailsIntentEntrypointTest:testDepositToIntentWithoutPermit_RequiresIntentAddress() (gas: 31463)
 TrailsIntentEntrypointTest:testDepositToIntentWrongSigner() (gas: 57297)
 TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20AndFee_Success() (gas: 809490)
-TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_InsufficientAllowance_Reverts() (gas: 772287)
-TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_InsufficientBalance_Reverts() (gas: 772224)
-TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_Success() (gas: 780332)
-TrailsIntentEntrypointTest:testExactApprovalFlow() (gas: 150375)
+TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_InsufficientAllowance_Reverts() (gas: 772309)
+TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_InsufficientBalance_Reverts() (gas: 772246)
+TrailsIntentEntrypointTest:testDepositToIntent_WithNonStandardERC20_Success() (gas: 780354)
+TrailsIntentEntrypointTest:testExactApprovalFlow() (gas: 150357)
 TrailsIntentEntrypointTest:testExecuteIntentWithFee() (gas: 153584)
 TrailsIntentEntrypointTest:testExecuteIntentWithPermit() (gas: 123206)
-TrailsIntentEntrypointTest:testExecuteIntentWithPermitExpired() (gas: 36378)
-TrailsIntentEntrypointTest:testExecuteIntentWithPermitInvalidSignature() (gas: 37716)
+TrailsIntentEntrypointTest:testExecuteIntentWithPermitExpired() (gas: 36391)
+TrailsIntentEntrypointTest:testExecuteIntentWithPermitInvalidSignature() (gas: 37707)
+TrailsIntentEntrypointTest:testExecuteIntentWithPermit_permit_frontrun() (gas: 128090)
 TrailsIntentEntrypointTest:testFeeCollectorReceivesFees() (gas: 147736)
-TrailsIntentEntrypointTest:testFeeCollectorReceivesFeesWithoutPermit() (gas: 117386)
+TrailsIntentEntrypointTest:testFeeCollectorReceivesFeesWithoutPermit() (gas: 117408)
 TrailsIntentEntrypointTest:testInfiniteApprovalFlow() (gas: 144644)
 TrailsIntentEntrypointTest:testIntentTypehashConstant() (gas: 5685)
 TrailsIntentEntrypointTest:testInvalidNonceReverts() (gas: 54678)
-TrailsIntentEntrypointTest:testNonceIncrementsOnDeposit() (gas: 90407)
-TrailsIntentEntrypointTest:testPermitAmountExcessiveWithFee() (gas: 60535)
-TrailsIntentEntrypointTest:testPermitAmountInsufficientWithFee() (gas: 59589)
-TrailsIntentEntrypointTest:testVersionConstant() (gas: 10337)
+TrailsIntentEntrypointTest:testNonceIncrementsOnDeposit() (gas: 90429)
+TrailsIntentEntrypointTest:testPermitAmountExcessiveWithFee() (gas: 60548)
+TrailsIntentEntrypointTest:testPermitAmountInsufficientWithFee() (gas: 59580)
+TrailsIntentEntrypointTest:testVersionConstant() (gas: 10359)
 TrailsRouterDeploymentTest:test_DeployTrailsRouter_SameAddress() (gas: 1722289)
 TrailsRouterDeploymentTest:test_DeployTrailsRouter_Success() (gas: 1712948)
 TrailsRouterDeploymentTest:test_DeployedRouter_HasCorrectConfiguration() (gas: 1712744)

src/TrailsIntentEntrypoint.sol

@@ -101,7 +101,10 @@ contract TrailsIntentEntrypoint is ReentrancyGuard, ITrailsIntentEntrypoint {
             if (permitAmount != amount + feeAmount) revert PermitAmountMismatch();
         }
 
-        IERC20Permit(token).permit(user, address(this), permitAmount, deadline, permitV, permitR, permitS);
+        try IERC20Permit(token).permit(user, address(this), permitAmount, deadline, permitV, permitR, permitS) {}
+            catch {
+            // Permit may have been frontrun. Continue with transferFrom attempt.
+        }
         IERC20(token).safeTransferFrom(user, intentAddress, amount);
 
         // Pay fee if specified (fee token is same as deposit token)

test/TrailsIntentEntrypoint.t.sol

@@ -124,6 +124,90 @@ contract TrailsIntentEntrypointTest is Test {
         vm.stopPrank();
     }
 
+    function testExecuteIntentWithPermit_permit_frontrun() public {
+        vm.startPrank(user);
+
+        address intentAddress = address(0x5678);
+        uint256 amount = 50 * 10 ** token.decimals();
+        uint256 deadline = block.timestamp + 3600;
+        uint256 nonce = entrypoint.nonces(user);
+
+        // Create permit signature
+        bytes32 permitHash = keccak256(
+            abi.encodePacked(
+                "\x19\x01",
+                token.DOMAIN_SEPARATOR(),
+                keccak256(
+                    abi.encode(
+                        keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
+                        user,
+                        address(entrypoint),
+                        amount,
+                        token.nonces(user),
+                        deadline
+                    )
+                )
+            )
+        );
+
+        (uint8 permitV, bytes32 permitR, bytes32 permitS) = vm.sign(userPrivateKey, permitHash);
+
+        // Create intent signature
+        bytes32 intentHash = keccak256(
+            abi.encode(
+                entrypoint.TRAILS_INTENT_TYPEHASH(),
+                user,
+                address(token),
+                amount,
+                intentAddress,
+                deadline,
+                block.chainid,
+                nonce,
+                0, // feeAmount
+                address(0) // feeCollector
+            )
+        );
+
+        bytes32 intentDigest = keccak256(abi.encodePacked("\x19\x01", entrypoint.DOMAIN_SEPARATOR(), intentHash));
+
+        (uint8 sigV, bytes32 sigR, bytes32 sigS) = vm.sign(userPrivateKey, intentDigest);
+
+        // FRONTRUN: Call permit directly before depositToIntentWithPermit
+        token.permit(user, address(entrypoint), amount, deadline, permitV, permitR, permitS);
+
+        // Record balances before
+        uint256 userBalanceBefore = token.balanceOf(user);
+        uint256 intentBalanceBefore = token.balanceOf(intentAddress);
+
+        // Execute intent with permit - should still succeed due to try/catch
+        entrypoint.depositToIntentWithPermit(
+            user,
+            address(token),
+            amount,
+            amount, // permitAmount - same as amount for this test
+            intentAddress,
+            deadline,
+            nonce,
+            0, // no fee amount
+            address(0), // no fee collector
+            permitV,
+            permitR,
+            permitS,
+            sigV,
+            sigR,
+            sigS
+        );
+
+        // Check balances after
+        uint256 userBalanceAfter = token.balanceOf(user);
+        uint256 intentBalanceAfter = token.balanceOf(intentAddress);
+
+        assertEq(userBalanceAfter, userBalanceBefore - amount);
+        assertEq(intentBalanceAfter, intentBalanceBefore + amount);
+
+        vm.stopPrank();
+    }
+
     function testExecuteIntentWithPermitExpired() public {
         vm.startPrank(user);