feat: support Permit (ERC-2612)

Author: heueristik

.solhint.other.json

@@ -37,7 +37,7 @@
     "gas-indexed-events": "warn",
     "gas-multitoken1155": "warn",
     "gas-named-return-values": "warn",
-    "gas-small-strings": "warn",
+    "gas-small-strings": "off",
     "gas-struct-packing": "warn",
 
     "quotes": "error",
@@ -49,13 +49,13 @@
     "avoid-tx-origin": "error",
     "check-send-result": "error",
     "compiler-version": ["error", "^0.8.24"],
-    "func-visibility": ["error", { "ignoreConstructors": true }],
+    "func-visibility": ["error", {"ignoreConstructors": true}],
 
     "multiple-sends": "error",
     "no-complex-fallback": "error",
     "no-inline-assembly": "error",
     "not-rely-on-block-hash": "error",
-    "not-rely-on-time": "error",
+    "not-rely-on-time": "off",
     "reentrancy": "error",
     "state-visibility": "error"
   }

lib/openzeppelin-foundry-upgrades

@@ -3,18 +3,28 @@ pragma solidity ^0.8.30;
 
 import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
 import {UUPSUpgradeable} from "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
-
 import {ERC20Upgradeable} from "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
 import {ERC20BurnableUpgradeable} from
     "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20BurnableUpgradeable.sol";
+import {ERC20PermitUpgradeable} from
+    "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20PermitUpgradeable.sol";
+import {EIP712Upgradeable} from "@openzeppelin/contracts-upgradeable/utils/cryptography/EIP712Upgradeable.sol";
 import {ERC1967Utils} from "@openzeppelin/contracts/proxy/ERC1967/ERC1967Utils.sol";
+
 import {Time} from "@openzeppelin/contracts/utils/types/Time.sol";
 
 import {IXanV1} from "./interfaces/IXanV1.sol";
 import {Parameters} from "./libs/Parameters.sol";
 import {Ranking} from "./libs/Ranking.sol";
 
-contract XanV1 is IXanV1, Initializable, ERC20Upgradeable, ERC20BurnableUpgradeable, UUPSUpgradeable {
+contract XanV1 is
+    IXanV1,
+    Initializable,
+    ERC20Upgradeable,
+    ERC20PermitUpgradeable,
+    ERC20BurnableUpgradeable,
+    UUPSUpgradeable
+{
     using Ranking for Ranking.ProposedUpgrades;
 
     /// @notice The [ERC-7201](https://eips.ethereum.org/EIPS/eip-7201) storage of the contract.
@@ -243,7 +253,11 @@ contract XanV1 is IXanV1, Initializable, ERC20Upgradeable, ERC20BurnableUpgradea
     function __XanV1_init(address initialMintRecipient) internal onlyInitializing {
         // Initialize inherited contracts
         __Context_init_unchained();
+
         __ERC20_init_unchained({name_: Parameters.NAME, symbol_: Parameters.SYMBOL});
+        __ERC20Permit_init(Parameters.NAME); // TODO! Revisit OZ
+        //__ERC20Permit_init_unchained(tokenName);
+        //__EIP712_init_unchained({name: tokenName, version: "1"});
         __ERC20Burnable_init_unchained();
         __UUPSUpgradeable_init_unchained();
 

src/XanV1.sol

@@ -21,7 +21,6 @@ contract XanV1UnitTest is Test {
     function setUp() public {
         (, _defaultSender,) = vm.readCallers();
 
-        vm.prank(_defaultSender);
         _xanProxy = XanV1(
             Upgrades.deployUUPSProxy({
                 contractName: "XanV1.sol:XanV1",
@@ -626,6 +625,46 @@ contract XanV1UnitTest is Test {
         assertEq(_xanProxy.lockedSupply(), 3 * valueToLock);
     }
 
+    function test_permits_spending_given_an_EIP712_signature() public {
+        uint256 alicePrivKey = 0xA11CE;
+        address aliceAddr = vm.addr(alicePrivKey);
+        address spender = address(uint160(4));
+
+        // Give funds to Alice
+        vm.prank(_defaultSender);
+        _xanProxy.transfer({to: aliceAddr, value: 1_000});
+
+        // Sign message
+        uint256 nonce = _xanProxy.nonces(aliceAddr);
+        uint256 deadline = block.timestamp + 1 hours;
+        uint256 value = 500;
+
+        bytes32 structHash = keccak256(
+            abi.encode(
+                keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"),
+                aliceAddr,
+                spender,
+                value,
+                nonce,
+                deadline
+            )
+        );
+
+        bytes32 domainSeparator = _xanProxy.DOMAIN_SEPARATOR();
+        bytes32 digest = keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
+        (uint8 v, bytes32 r, bytes32 s) = vm.sign(alicePrivKey, digest);
+
+        // Check that the spender is allowed to spend 0 XAN of Alice before the `permit` call.
+        assertEq(_xanProxy.allowance({owner: aliceAddr, spender: spender}), 0);
+
+        // Given the signature, anyone (here `_defaultSender`) can set the allowance.
+        vm.prank(_defaultSender);
+        _xanProxy.permit({owner: aliceAddr, spender: spender, value: value, deadline: deadline, v: v, r: r, s: s});
+
+        // Check that the spender is allowed to spend `value` XAN of Alice after the `permit` call.
+        assertEq(_xanProxy.allowance({owner: aliceAddr, spender: spender}), value);
+    }
+
     function test_initialize_mints_the_expected_supply_amounting_to_1_billion_tokens() public view {
         uint256 expectedTokens = 10 ** 9;