Split ERC-7821 executor into its own contract (#61)

Co-authored-by: Hadrien Croubois <[email protected]>

Author: ernestognw

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 13-01-2025
 
 - Rename `ERC7739Signer` into `ERC7739` to avoid confusion with the `AbstractSigner` family of contracts.
+- Remove `AccountERC7821` in favor of `ERC7821`, an ERC-7821 implementation that doesn't rely on (but is compatible with) `AccountCore`.
 
 ## 23-12-2024
 

contracts/account/Account.sol

@@ -5,17 +5,26 @@ pragma solidity ^0.8.20;
 import {ERC721Holder} from "@openzeppelin/contracts/token/ERC721/utils/ERC721Holder.sol";
 import {ERC1155Holder} from "@openzeppelin/contracts/token/ERC1155/utils/ERC1155Holder.sol";
 import {ERC7739} from "../utils/cryptography/ERC7739.sol";
+import {ERC7821} from "./extensions/ERC7821.sol";
 import {AccountCore} from "./AccountCore.sol";
-import {AccountERC7821} from "./extensions/AccountERC7821.sol";
 
 /**
  * @dev Extension of {AccountCore} with recommended feature that most account abstraction implementation will want:
  *
- * * {AccountERC7821} for performing external calls in batches.
  * * {ERC721Holder} and {ERC1155Holder} to accept ERC-712 and ERC-1155 token transfers transfers.
  * * {ERC7739} for ERC-1271 signature support with ERC-7739 replay protection
+ * * {ERC7821} for performing external calls in batches.
  *
  * NOTE: To use this contract, the {ERC7739-_rawSignatureValidation} function must be
  * implemented using a specific signature verification algorithm. See {SignerECDSA}, {SignerP256} or {SignerRSA}.
  */
-abstract contract Account is AccountCore, AccountERC7821, ERC721Holder, ERC1155Holder, ERC7739 {}
+abstract contract Account is AccountCore, ERC721Holder, ERC1155Holder, ERC7739, ERC7821 {
+    /// @inheritdoc ERC7821
+    function _erc7821AuthorizedExecutor(
+        address caller,
+        bytes32 mode,
+        bytes calldata executionData
+    ) internal view virtual override returns (bool) {
+        return super._erc7821AuthorizedExecutor(caller, mode, executionData) || caller == address(entryPoint());
+    }
+}

contracts/account/README.adoc

@@ -2,7 +2,12 @@
 [.readme-notice]
 NOTE: This document is better viewed at https://docs.openzeppelin.com/community-contracts/api/account
 
-This directory includes contracts to build accounts for ERC-4337.
+This directory includes contracts to build accounts for ERC-4337. These include:
+
+ * {AccountCore}: An ERC-4337 smart account implementation that includes the core logic to process user operations.
+ * {Account}: An extension of `AccountCore` that implements the recommended features for ERC-4337 smart accounts.
+ * {AccountSignerERC7702}: An account implementation with low-level signature validation performed by an EOA.
+ * {ERC7821}: Minimal batch executor implementation contracts. Useful to enable easy batch execution for smart contracts. 
 
 == Core
 
@@ -14,4 +19,4 @@ This directory includes contracts to build accounts for ERC-4337.
 
 {{AccountSignerERC7702}}
 
-{{AccountERC7821}}
+{{ERC7821}}

contracts/account/extensions/AccountERC7821.sol renamed to contracts/account/extensions/ERC7821.sol

@@ -7,15 +7,24 @@ import {IERC7821} from "../../interfaces/IERC7821.sol";
 import {AccountCore} from "../AccountCore.sol";
 
 /**
- * @dev Minimal batch executor following ERC7821. Only supports basic mode (no optional "opData").
+ * @dev Minimal batch executor following ERC-7821. Only supports basic mode (no optional "opData").
  */
-abstract contract AccountERC7821 is AccountCore, IERC7821 {
+abstract contract ERC7821 is IERC7821 {
     using ERC7579Utils for *;
 
     error UnsupportedExecutionMode();
 
-    /// @inheritdoc IERC7821
-    function execute(bytes32 mode, bytes calldata executionData) public payable virtual onlyEntryPointOrSelf {
+    /**
+     * @dev Executes the calls in `executionData` with no optional `opData` support.
+     *
+     * NOTE: Access to this function is controlled by {_erc7821AuthorizedExecutor}. Changing access permissions, for
+     * example to approve calls by the ERC-4337 entrypoint, should be implement by overriding it.
+     *
+     * Reverts and bubbles up error if any call fails.
+     */
+    function execute(bytes32 mode, bytes calldata executionData) public payable virtual {
+        if (!_erc7821AuthorizedExecutor(msg.sender, mode, executionData))
+            revert AccountCore.AccountUnauthorized(msg.sender);
         if (!supportsExecutionMode(mode)) revert UnsupportedExecutionMode();
         executionData.execBatch(ERC7579Utils.EXECTYPE_DEFAULT);
     }
@@ -28,4 +37,15 @@ abstract contract AccountERC7821 is AccountCore, IERC7821 {
             execType == ERC7579Utils.EXECTYPE_DEFAULT &&
             modeSelector == ModeSelector.wrap(0x00000000);
     }
+
+    /**
+     * @dev Access control mechanism for the {execute} function.
+     */
+    function _erc7821AuthorizedExecutor(
+        address caller,
+        bytes32 /* mode */,
+        bytes calldata /* executionData */
+    ) internal view virtual returns (bool) {
+        return caller == address(this);
+    }
 }

foundry.toml

@@ -1,6 +1,8 @@
 [profile.default]
 solc_version = '0.8.27'
 evm_version = 'cancun'
+optimizer = true
+optimizer-runs = 200
 src = 'contracts'
 out = 'out'
 libs = ['node_modules', 'lib']