transferFromWithSignature

buidler.config.ts

@@ -7,7 +7,7 @@ usePlugin("buidler-gas-reporter");
 export default {
     defaultNetwork: "buidlerevm",
     solc: {
-        version: "0.6.10",
+        version: "0.8.0",
         optimizer: {
             enabled: true,
             runs: 200

contracts/ERC20Permit.sol

@@ -1,23 +1,20 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/53516bc555a454862470e7860a9b5254db4d00f5/contracts/token/ERC20/ERC20Permit.sol
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
-import "./IERC2612.sol";
+import "acc-erc20/contracts/ERC20.sol";
 
 /**
- * @author Georgios Konstantopoulos
- * @dev Extension of {ERC20} that allows token holders to use their tokens
- * without sending any transactions by setting {IERC20-allowance} with a
- * signature using the {permit} method, and then spend them via
- * {IERC20-transferFrom}.
+ * @author Alberto Cuesta Cañada
+ * @dev Extension of {ERC20} that allows token holders set allowances or approve a single `transferFrom` using off-chain signatures.
  *
- * The {permit} signature mechanism conforms to the {IERC2612} interface.
+ * The mechanisms don't conform to the {IERC2612} interface.
  */
-abstract contract ERC20Permit is ERC20, IERC2612 {
-    mapping (address => uint256) public override nonces;
+abstract contract ERC20Permit is ERC20 {
+    mapping (address => uint256) public nonces;
 
     bytes32 public immutable PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+    bytes32 public immutable TRANSFERFROM_TYPEHASH = keccak256("TransferFrom(address sender,address recipient,uint256 value,uint256 nonce,uint256 deadline)");
     bytes32 public immutable DOMAIN_SEPARATOR;
 
     constructor(string memory name_, string memory symbol_) internal ERC20(name_, symbol_) {
@@ -38,12 +35,18 @@ abstract contract ERC20Permit is ERC20, IERC2612 {
     }
 
     /**
-     * @dev See {IERC2612-permit}.
+     * @dev Similar to {IERC2612-permit}, but with a packed signature.
      *
      * In cases where the free option is not a concern, deadline can simply be
-     * set to uint(-1), so it should be seen as an optional parameter
+     * set to uint(-1), so it should be seen as an optional parameter.
      */
-    function permit(address owner, address spender, uint256 amount, uint256 deadline, uint8 v, bytes32 r, bytes32 s) public virtual override {
+    function permit(
+        address owner,
+        address spender,
+        uint256 amount,
+        uint256 deadline,
+        bytes memory signature
+    ) public virtual {
         require(deadline >= block.timestamp, "ERC20Permit: expired deadline");
 
         bytes32 hashStruct = keccak256(
@@ -65,12 +68,68 @@ abstract contract ERC20Permit is ERC20, IERC2612 {
             )
         );
 
+        (bytes32 r, bytes32 s, uint8 v) = unpack(signature);
         address signer = ecrecover(hash, v, r, s);
         require(
             signer != address(0) && signer == owner,
-            "ERC20Permit: invalid signature"
+            "ERC20Permit::permit: invalid signature"
         );
 
         _approve(owner, spender, amount);
     }
+
+    /**
+     * @dev Similar to {IERC20-transferFrom}, but with a packed signature. It doesn't check or change allowances.
+     *
+     * In cases where the free option is not a concern, deadline can simply be
+     * set to uint(-1), so it should be seen as an optional parameter.
+     */
+    function transferFromWithSignature(
+        address sender,
+        address recipient,
+        uint256 amount,
+        uint256 deadline,
+        bytes memory signature
+    ) public virtual returns(bool) {
+        require(deadline >= block.timestamp, "ERC20Permit: expired deadline");
+
+        bytes32 hashStruct = keccak256(
+            abi.encode(
+                TRANSFERFROM_TYPEHASH,
+                sender,
+                recipient,
+                amount,
+                nonces[sender]++,
+                deadline
+            )
+        );
+
+        bytes32 hash = keccak256(
+            abi.encodePacked(
+                '\x19\x01',
+                DOMAIN_SEPARATOR,
+                hashStruct
+            )
+        );
+
+        (bytes32 r, bytes32 s, uint8 v) = unpack(signature);
+        address signer = ecrecover(hash, v, r, s);
+        require(
+            signer != address(0) && signer == sender,
+            "ERC20Permit::transferFrom: invalid signature"
+        );
+
+        _transfer(sender, recipient, amount);
+        return true;
+    }
+
+    /// @dev Unpack r, s and v from a `bytes` signature.
+    /// @param signature A packed signature.
+    function unpack(bytes memory signature) internal pure returns (bytes32 r, bytes32 s, uint8 v) {
+        assembly {
+            r := mload(add(signature, 0x20))
+            s := mload(add(signature, 0x40))
+            v := byte(0, mload(add(signature, 0x60)))
+        }
+    }
 }

contracts/IERC2612.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Code adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Interface of the ERC2612 standard as defined in the EIP.

contracts/TestERC20.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-pragma solidity ^0.6.10;
+pragma solidity ^0.8.0;
 
 import "./ERC20Permit.sol";
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "erc20permit",
-  "version": "0.0.4",
+  "version": "0.0.5",
   "description": "Solidity contracts implementing ERC2612",
   "author": "Alberto Cuesta Cañada",
   "engines": {
@@ -30,16 +30,16 @@
     "lint:sol": "solhint -f table contracts/**/*.sol"
   },
   "dependencies": {
-    "@openzeppelin/contracts": "3.1.0"
+    "acc-erc20": "^0.5.1"
   },
   "devDependencies": {
     "@nomiclabs/buidler": "^1.3.8",
     "@nomiclabs/buidler-truffle5": "^1.3.4",
     "@nomiclabs/buidler-web3": "^1.3.4",
-    "@openzeppelin/contracts": "3.1.0",
     "@openzeppelin/test-helpers": "^0.5.6",
     "@truffle/hdwallet-provider": "^1.0.40",
     "@types/mocha": "^8.0.0",
+    "acc-erc20": "^0.5.1",
     "buidler-gas-reporter": "0.1.4-beta.4",
     "chai": "4.2.0",
     "ethereumjs-util": "^7.0.3",

yarn.lock

@@ -639,11 +639,6 @@
     fs-extra "^8.1.0"
     try-require "^1.2.1"
 
-"@openzeppelin/contracts@3.1.0":
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-3.1.0.tgz#bcea457ef89069fbe5a617f50b25b6a8272895d5"
-  integrity sha512-dVXDnUKxrAKLzPdCRkz+N8qsVkK1XxJ6kk3zuI6zaQmcKxN7CkizoDP7lXxcs/Mi2I0mxceTRjJBqlzFffLJrQ==
-
 "@openzeppelin/test-helpers@^0.5.6":
   version "0.5.6"
   resolved "https://registry.yarnpkg.com/@openzeppelin/test-helpers/-/test-helpers-0.5.6.tgz#cafa3fdb741be9e3ff525916257d6cdce45ed86a"
@@ -1115,6 +1110,11 @@ abstract-leveldown@~2.7.1:
   dependencies:
     xtend "~4.0.0"
 
+acc-erc20@^0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/acc-erc20/-/acc-erc20-0.5.0.tgz#01aef88ba75b5401998925179eae586da34d8b8e"
+  integrity sha512-+LpOR2SvvNtoTVBxw0VuRIEkiS7nibe1mBmhNb/x8k0YhRK/Y7XYe+sKjnf33sjIlbyu8Xj5V8rj1p3sz/zHEA==
+
 accepts@~1.3.7:
   version "1.3.7"
   resolved "https://registry.yarnpkg.com/accepts/-/accepts-1.3.7.tgz#531bc726517a3b2b41f850021c6cc15eaab507cd"