feat: permit (#22)

src/Membership.sol

@@ -4,6 +4,7 @@ pragma solidity 0.8.24;
 import { IPriceCalculator } from "./IPriceCalculator.sol";
 import { IERC20 } from "openzeppelin-contracts/contracts/token/ERC20/IERC20.sol";
 import { SafeERC20 } from "openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol";
+import { ERC20Permit } from "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";
 import { Initializable } from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
 
 // The rate limit is outside the expected limits
@@ -208,6 +209,63 @@ abstract contract MembershipUpgradeable is Initializable {
         IERC20(token).safeTransferFrom(_sender, address(this), depositAmount);
     }
 
+    /// @dev acquire a membership and transfer the deposit to the contract
+    /// Uses the RC20 Permit extension allowing approvals to be made via signatures, as defined in
+    /// [EIP-2612](https://eips.ethereum.org/EIPS/eip-2612).
+    /// @param _owner The address of the token owner who is giving permission and will own the membership.
+    /// @param _deadline The timestamp until when the permit is valid.
+    /// @param _v The recovery byte of the signature.
+    /// @param _r Half of the ECDSA signature pair.
+    /// @param _s Half of the ECDSA signature pair.
+    /// @param _idCommitment the idCommitment of the new membership
+    /// @param _rateLimit the membership rate limit
+    /// @return index the index of the new membership in the membership set
+    /// @return indexReused true if the index was reused, false otherwise
+    function _acquireMembershipWithPermit(
+        address _owner,
+        uint256 _deadline,
+        uint8 _v,
+        bytes32 _r,
+        bytes32 _s,
+        uint256 _idCommitment,
+        uint32 _rateLimit
+    )
+        internal
+        returns (uint32 index, bool indexReused)
+    {
+        // Check if the rate limit is valid
+        if (!isValidMembershipRateLimit(_rateLimit)) {
+            revert InvalidMembershipRateLimit();
+        }
+
+        currentTotalRateLimit += _rateLimit;
+
+        // Determine if we exceed the total rate limit
+        if (currentTotalRateLimit > maxTotalRateLimit) {
+            revert CannotExceedMaxTotalRateLimit();
+        }
+
+        (address token, uint256 depositAmount) = priceCalculator.calculate(_rateLimit);
+
+        ERC20Permit(token).permit(_owner, address(this), depositAmount, _deadline, _v, _r, _s);
+
+        // Possibly reuse an index of an erased membership
+        (index, indexReused) = _getFreeIndex();
+
+        memberships[_idCommitment] = MembershipInfo({
+            holder: _owner,
+            activeDuration: activeDurationForNewMemberships,
+            gracePeriodStartTimestamp: block.timestamp + uint256(activeDurationForNewMemberships),
+            gracePeriodDuration: gracePeriodDurationForNewMemberships,
+            token: token,
+            depositAmount: depositAmount,
+            rateLimit: _rateLimit,
+            index: index
+        });
+
+        IERC20(token).safeTransferFrom(_owner, address(this), depositAmount);
+    }
+
     /// @notice Checks if a rate limit is within the allowed bounds
     /// @param rateLimit The rate limit
     /// @return true if the rate limit is within the allowed bounds, false otherwise
@@ -233,7 +291,7 @@ abstract contract MembershipUpgradeable is Initializable {
     /// @dev Extend a grace-period membership
     /// @param _sender the address of the transaction sender
     /// @param _idCommitment the idCommitment of the membership
-    function _extendMembership(address _sender, uint256 _idCommitment) public {
+    function _extendMembership(address _sender, uint256 _idCommitment) internal {
         MembershipInfo storage membership = memberships[_idCommitment];
 
         if (!_isInPeriod(membership.gracePeriodStartTimestamp, membership.gracePeriodDuration)) {

src/WakuRlnV2.sol

@@ -170,23 +170,62 @@ contract WakuRlnV2 is Initializable, OwnableUpgradeable, UUPSUpgradeable, Member
     {
         // erase memberships without overwriting membership set data to zero (save gas)
         _eraseMemberships(idCommitmentsToErase, false);
-        _register(idCommitment, rateLimit);
+
+        (uint32 index, bool indexReused) = _acquireMembership(_msgSender(), idCommitment, rateLimit);
+
+        _upsertInTree(idCommitment, rateLimit, index, indexReused);
+
+        emit MembershipRegistered(idCommitment, rateLimit, index);
+    }
+
+    /// @notice Register a membership while erasing some expired memberships to reuse their rate limit.
+    /// Uses the RC20 Permit extension allowing approvals to be made via signatures, as defined in
+    /// [EIP-2612](https://eips.ethereum.org/EIPS/eip-2612).
+    /// @param owner The address of the token owner who is giving permission and will own the membership.
+    /// @param deadline The timestamp until when the permit is valid.
+    /// @param v The recovery byte of the signature.
+    /// @param r Half of the ECDSA signature pair.
+    /// @param s Half of the ECDSA signature pair.
+    /// @param idCommitment The idCommitment of the new membership
+    /// @param rateLimit The rate limit of the new membership
+    /// @param idCommitmentsToErase The list of idCommitments of expired memberships to erase
+    function registerWithPermit(
+        address owner,
+        uint256 deadline,
+        uint8 v,
+        bytes32 r,
+        bytes32 s,
+        uint256 idCommitment,
+        uint32 rateLimit,
+        uint256[] calldata idCommitmentsToErase
+    )
+        external
+        onlyValidIdCommitment(idCommitment)
+        noDuplicateMembership(idCommitment)
+        membershipSetNotFull
+    {
+        // erase memberships without overwriting membership set data to zero (save gas)
+        _eraseMemberships(idCommitmentsToErase, false);
+
+        (uint32 index, bool indexReused) =
+            _acquireMembershipWithPermit(owner, deadline, v, r, s, idCommitment, rateLimit);
+
+        _upsertInTree(idCommitment, rateLimit, index, indexReused);
+
+        emit MembershipRegistered(idCommitment, rateLimit, index);
     }
 
     /// @dev Register a membership (internal function)
     /// @param idCommitment The idCommitment of the membership
     /// @param rateLimit The rate limit of the membership
-    function _register(uint256 idCommitment, uint32 rateLimit) internal {
-        (uint32 index, bool indexReused) = _acquireMembership(_msgSender(), idCommitment, rateLimit);
+    function _upsertInTree(uint256 idCommitment, uint32 rateLimit, uint32 index, bool indexReused) internal {
         uint256 rateCommitment = PoseidonT3.hash([idCommitment, rateLimit]);
         if (indexReused) {
             LazyIMT.update(merkleTree, rateCommitment, index);
         } else {
             LazyIMT.insert(merkleTree, rateCommitment);
             nextFreeIndex += 1;
         }
-
-        emit MembershipRegistered(idCommitment, rateLimit, index);
     }
 
     /// @notice Returns the root of the Merkle tree that stores rate commitments of memberships

test/TestToken.sol

@@ -3,9 +3,10 @@ pragma solidity >=0.8.19 <0.9.0;
 
 import { BaseScript } from "../script/Base.s.sol";
 import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { ERC20Permit } from "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";
 
-contract TestToken is ERC20 {
-    constructor() ERC20("TestToken", "TTT") { }
+contract TestToken is ERC20, ERC20Permit {
+    constructor() ERC20("TestToken", "TTT") ERC20Permit("TestToken") { }
 
     function mint(address to, uint256 amount) public {
         _mint(to, amount);

test/WakuRlnV2.t.sol

@@ -11,6 +11,7 @@ import { TestToken } from "./TestToken.sol";
 import { PoseidonT3 } from "poseidon-solidity/PoseidonT3.sol";
 import { UUPSUpgradeable } from "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
 import { ERC1967Proxy } from "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";
+import { ECDSA } from "@openzeppelin/contracts/utils/cryptography/ECDSA.sol"; // For signature manipulation
 import "forge-std/console.sol";
 
 contract WakuRlnV2Test is Test {
@@ -121,6 +122,48 @@ contract WakuRlnV2Test is Test {
         assertEq(w.currentTotalRateLimit(), membershipRateLimit);
     }
 
+    function test__ValidRegistrationWithPermit() external {
+        vm.pauseGasMetering();
+        uint256 idCommitment = 2;
+        uint32 membershipRateLimit = w.minMembershipRateLimit();
+        (, uint256 price) = w.priceCalculator().calculate(membershipRateLimit);
+
+        // Creating an owner for a membership (Alice)
+        uint256 alicePrivK = 0xA11CE;
+        address aliceAddr = vm.addr(alicePrivK);
+
+        // Minting some tokens so Alice can register a membership
+        token.mint(aliceAddr, price);
+
+        // Prepare the permit parameters
+        bytes32 permitHash = keccak256(
+            abi.encode(
+                keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
+                aliceAddr, // Owner of the membership
+                address(w), // Spender (The rln proxy contract)
+                price,
+                token.nonces(aliceAddr),
+                block.timestamp + 1 hours // Deadline
+            )
+        );
+
+        // Sign the permit hash using the owner's private key
+        (uint8 v, bytes32 r, bytes32 s) =
+            vm.sign(alicePrivK, ECDSA.toTypedDataHash(token.DOMAIN_SEPARATOR(), permitHash));
+
+        vm.resumeGasMetering();
+
+        // Call the function on-chain using the generated signature
+        w.registerWithPermit(
+            aliceAddr, block.timestamp + 1 hours, v, r, s, idCommitment, membershipRateLimit, noIdCommitmentsToErase
+        );
+
+        (,,,, uint32 fetchedMembershipRateLimit,, address holder,) = w.memberships(idCommitment);
+        assertEq(fetchedMembershipRateLimit, membershipRateLimit);
+        assertEq(holder, aliceAddr);
+        assertEq(token.balanceOf(address(w)), price);
+    }
+
     function test__LinearPriceCalculation(uint32 membershipRateLimit) external view {
         IPriceCalculator priceCalculator = w.priceCalculator();
         uint256 pricePerMessagePerPeriod = LinearPriceCalculator(address(priceCalculator)).pricePerMessagePerEpoch();