Add merkle proof hash generation

coinbase · Oct 9, 2024 · 24cd653 · 24cd653
1 parent 9670fb0
commit 24cd653
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Showing 4 changed files with 54 additions and 16 deletions.
diff --git a/src/SpendPermissions.sol b/src/SpendPermissions.sol
@@ -31,6 +31,16 @@ contract SpendPermissions {
         uint160 allowance;
     }
 
+    /// @notice A signed permit to approve a recurring allowance.
+    struct SignedPermit {
+        /// @dev Recurring allowance parameters.
+        RecurringAllowance recurringAllowance;
+        /// @dev User signature to validate via EIP-1271.
+        bytes signature;
+        /// @dev Optional Merkle proof from batch signing of many recurring allowances.
+        bytes32[] proof;
+    }
+
     /// @notice Cycle parameters and spend usage.
     struct CycleUsage {
         /// @dev Start time of the cycle (unix seconds).
@@ -150,26 +160,25 @@ contract SpendPermissions {
     /// @param recipient Address to withdraw tokens to.
     /// @param value Amount of token attempting to withdraw (wei).
     function withdraw(bytes calldata context, address recipient, uint160 value) external {
-        (RecurringAllowance memory recurringAllowance, bytes memory signature) =
-            abi.decode(context, (RecurringAllowance, bytes));
-        permit(recurringAllowance, signature);
-        withdraw(recurringAllowance, recipient, value);
+        SignedPermit memory signedPermit = abi.decode(context, (SignedPermit));
+        permit(signedPermit);
+        withdraw(signedPermit.recurringAllowance, recipient, value);
     }
 
     /// @notice Approve a recurring allowance via a signature from the account.
     ///
-    /// @param recurringAllowance Details of the recurring allowance.
-    /// @param signature Signed hash of the recurring allowance data.
-    function permit(RecurringAllowance memory recurringAllowance, bytes memory signature) public {
+    /// @param signedPermit user-approved recurring allowance with optional Merkle proof if batch signed.
+    function permit(SignedPermit memory signedPermit) public {
         // validate signature over recurring allowance data
         if (
-            IERC1271(recurringAllowance.account).isValidSignature(getHash(recurringAllowance), signature)
-                != IERC1271.isValidSignature.selector
+            IERC1271(signedPermit.recurringAllowance.account).isValidSignature(
+                getRoot(signedPermit.recurringAllowance, signedPermit.proof), signedPermit.signature
+            ) != IERC1271.isValidSignature.selector
         ) {
             revert UnauthorizedRecurringAllowance();
         }
 
-        _approve(recurringAllowance);
+        _approve(signedPermit.recurringAllowance);
     }
 
     /// @notice Withdraw tokens using a recurring allowance.
@@ -197,6 +206,27 @@ contract SpendPermissions {
         return keccak256(abi.encode(recurringAllowance, block.chainid, address(this)));
     }
 
+    /// @notice Hash a RecurringAllowance struct for signing.
+    ///
+    /// @dev Prevent phishing permits by making the hash incompatible with EIP-191/712.
+    /// @dev Include chainId and contract address in hash for cross-chain and cross-contract replay protection.
+    ///
+    /// @param recurringAllowance Details of the recurring allowance.
+    /// @param proof Merkle branch matching this recurring allowance to reconstruct root.
+    ///
+    /// @return root Merkle root of a batch of recurring allowances.
+    function getRoot(RecurringAllowance memory recurringAllowance, bytes32[] memory proof)
+        public
+        view
+        returns (bytes32 root)
+    {
+        root = getHash(recurringAllowance);
+        uint256 len = proof.length;
+        for (uint256 i = 0; i < len; i++) {
+            root = keccak256(abi.encode(root, proof[i]));
+        }
+    }
+
     /// @notice Return if recurring allowance is authorized i.e. approved and not revoked.
     ///
     /// @param recurringAllowance Details of the recurring allowance.

diff --git a/src/SpendPermissionsPaymaster.sol b/src/SpendPermissionsPaymaster.sol
@@ -55,8 +55,10 @@ contract SpendPermissionsPaymaster is SpendPermissions, Ownable2Step, IPaymaster
         requireSender(entryPoint())
         returns (bytes memory postOpContext, uint256 validationData)
     {
-        (RecurringAllowance memory recurringAllowance, bytes memory signature, uint256 withdrawAmount) =
-            abi.decode(userOp.paymasterAndData[20:], (RecurringAllowance, bytes, uint256));
+        // todo allow passing signature for first-time allowance use
+        (SignedPermit memory signedPermit, uint256 withdrawAmount) =
+            abi.decode(userOp.paymasterAndData[20:], (SignedPermit, uint256));
+        RecurringAllowance memory recurringAllowance = signedPermit.recurringAllowance;
 
         // require withdraw amount not less than max gas cost
         if (withdrawAmount < maxGasCost) {
@@ -74,8 +76,8 @@ contract SpendPermissionsPaymaster is SpendPermissions, Ownable2Step, IPaymaster
         }
 
         // apply permit if signature length non-zero
-        if (signature.length > 0) {
-            permit(recurringAllowance, signature);
+        if (signedPermit.signature.length > 0) {
+            permit(signedPermit);
         }
 
         // check total spend value does not overflow max value

diff --git a/test/src/SpendPermissions/Debug.t.sol b/test/src/SpendPermissions/Debug.t.sol
@@ -29,6 +29,7 @@ contract DebugTest is Test, Base {
     }
 
     function test_withdraw(address recipient) public {
+        vm.assume(recipient != address(spendPermissions));
         SpendPermissions.RecurringAllowance memory recurringAllowance = _createRecurringAllowance();
 
         vm.prank(address(account));

diff --git a/test/src/SpendPermissionsPaymaster/Debug.t.sol b/test/src/SpendPermissionsPaymaster/Debug.t.sol
@@ -49,7 +49,9 @@ contract DebugTest is Test, Base {
 
         vm.assertEq(account.isValidSignature(hash, signature), IERC1271.isValidSignature.selector);
 
-        bytes memory paymasterData = abi.encode(recurringAllowance, signature, allowance);
+        SpendPermissions.SignedPermit memory signedPermit =
+            SpendPermissions.SignedPermit(recurringAllowance, signature, new bytes32[](0));
+        bytes memory paymasterData = abi.encode(signedPermit, allowance);
 
         userOp.paymasterAndData = abi.encodePacked(address(spendPermissions), paymasterData);
 
@@ -79,7 +81,10 @@ contract DebugTest is Test, Base {
 
         vm.assertEq(account.isValidSignature(hash, signature), IERC1271.isValidSignature.selector);
 
-        spendPermissions.permit(recurringAllowance, signature);
+        SpendPermissions.SignedPermit memory signedPermit =
+            SpendPermissions.SignedPermit(recurringAllowance, signature, new bytes32[](0));
+
+        spendPermissions.permit(signedPermit);
 
         vm.assertTrue(spendPermissions.isAuthorized(recurringAllowance));