Add ERC7821 to Account.sol

contracts/account/Account.sol

@@ -6,14 +6,16 @@ import {ERC721Holder} from "@openzeppelin/contracts/token/ERC721/utils/ERC721Hol
 import {ERC1155Holder} from "@openzeppelin/contracts/token/ERC1155/utils/ERC1155Holder.sol";
 import {ERC7739Signer} from "../utils/cryptography/ERC7739Signer.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.
  * * {ERC7739Signer} for ERC-1271 signature support with ERC-7739 replay protection
  *
  * NOTE: To use this contract, the {ERC7739Signer-_rawSignatureValidation} function must be
  * implemented using a specific signature verification algorithm. See {SignerECDSA}, {SignerP256} or {SignerRSA}.
  */
-abstract contract Account is AccountCore, ERC721Holder, ERC1155Holder, ERC7739Signer {}
+abstract contract Account is AccountCore, AccountERC7821, ERC721Holder, ERC1155Holder, ERC7739Signer {}

contracts/account/AccountCore.sol

@@ -15,6 +15,10 @@ import {AbstractSigner} from "../utils/cryptography/AbstractSigner.sol";
  *
  * Developers must implement the {AbstractSigner-_rawSignatureValidation} function to define the account's validation logic.
  *
+ * NOTE: This core account doesn't include any mechanism for performing arbitrary external calls. This is an essential
+ * feature that all Account should have. We leave it up to the developers to implement the mechanism of their choice.
+ * Common choices include ERC-6900, ERC-7579 and ERC-7821 (among others).
+ *
  * IMPORTANT: Implementing a mechanism to validate signatures is a security-sensitive operation as it may allow an
  * attacker to bypass the account's security measures. Check out {SignerECDSA}, {SignerP256}, or {SignerRSA} for
  * digital signature validation implementations.
@@ -91,14 +95,7 @@ abstract contract AccountCore is AbstractSigner, EIP712, IAccount, IAccountExecu
         PackedUserOperation calldata userOp,
         bytes32 /*userOpHash*/
     ) public virtual onlyEntryPointOrSelf {
-        // decode packed calldata
-        address target = address(bytes20(userOp.callData[4:24]));
-        uint256 value = uint256(bytes32(userOp.callData[24:56]));
-        bytes calldata data = userOp.callData[56:];
-
-        // we cannot use `Address.functionCallWithValue` here as it would revert on EOA targets
-        (bool success, bytes memory returndata) = target.call{value: value}(data);
-        Address.verifyCallResult(success, returndata);
+        Address.functionDelegateCall(address(this), userOp.callData[4:]);
     }
 
     /**

contracts/account/extensions/AccountERC7821.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {ERC7579Utils, Mode, CallType, ExecType, ModeSelector} from "@openzeppelin/contracts/account/utils/draft-ERC7579Utils.sol";
+import {IERC7821} from "../../interfaces/IERC7821.sol";
+import {AccountCore} from "../AccountCore.sol";
+
+/**
+ * @dev Minimal batch executor following ERC7821. Only supports basic mode (no optional "opData").
+ */
+abstract contract AccountERC7821 is AccountCore, IERC7821 {
+    using ERC7579Utils for *;
+
+    error UnsupportedExecutionMode();
+
+    /// @inheritdoc IERC7821
+    function execute(bytes32 mode, bytes calldata executionData) public payable virtual onlyEntryPointOrSelf {
+        if (!supportsExecutionMode(mode)) revert UnsupportedExecutionMode();
+        executionData.execBatch(ERC7579Utils.EXECTYPE_DEFAULT);
+    }
+
+    /// @inheritdoc IERC7821
+    function supportsExecutionMode(bytes32 mode) public view virtual returns (bool result) {
+        (CallType callType, ExecType execType, ModeSelector modeSelector, ) = Mode.wrap(mode).decodeMode();
+        return
+            callType == ERC7579Utils.CALLTYPE_BATCH &&
+            execType == ERC7579Utils.EXECTYPE_DEFAULT &&
+            modeSelector == ModeSelector.wrap(0x00000000);
+    }
+}

contracts/interfaces/IERC7821.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Interface for minimal batch executor.
+ */
+interface IERC7821 {
+    /**
+     * @dev Executes the calls in `executionData`.
+     * Reverts and bubbles up error if any call fails.
+     *
+     * `executionData` encoding:
+     * - If `opData` is empty, `executionData` is simply `abi.encode(calls)`.
+     * - Else, `executionData` is `abi.encode(calls, opData)`.
+     *   See: https://eips.ethereum.org/EIPS/eip-7579
+     *
+     * Supported modes:
+     * - `bytes32(0x01000000000000000000...)`: does not support optional `opData`.
+     * - `bytes32(0x01000000000078210001...)`: supports optional `opData`.
+     *
+     * Authorization checks:
+     * - If `opData` is empty, the implementation SHOULD require that
+     *   `msg.sender == address(this)`.
+     * - If `opData` is not empty, the implementation SHOULD use the signature
+     *   encoded in `opData` to determine if the caller can perform the execution.
+     *
+     * `opData` may be used to store additional data for authentication,
+     * paymaster data, gas limits, etc.
+     */
+    function execute(bytes32 mode, bytes calldata executionData) external payable;
+
+    /**
+     * @dev This function is provided for frontends to detect support.
+     * Only returns true for:
+     * - `bytes32(0x01000000000000000000...)`: does not support optional `opData`.
+     * - `bytes32(0x01000000000078210001...)`: supports optional `opData`.
+     */
+    function supportsExecutionMode(bytes32 mode) external view returns (bool);
+}

test/account/Account.behavior.js

@@ -4,6 +4,7 @@ const { setBalance } = require('@nomicfoundation/hardhat-network-helpers');
 
 const { impersonate } = require('@openzeppelin/contracts/test/helpers/account');
 const { SIG_VALIDATION_SUCCESS, SIG_VALIDATION_FAILURE } = require('@openzeppelin/contracts/test/helpers/erc4337');
+const { CALL_TYPE_BATCH, encodeMode, encodeBatch } = require('@openzeppelin/contracts/test/helpers/erc7579');
 const {
   shouldSupportInterfaces,
 } = require('@openzeppelin/contracts/test/utils/introspection/SupportsInterface.behavior');
@@ -148,7 +149,7 @@ function shouldBehaveLikeAccountHolder() {
   });
 }
 
-function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
+function shouldBehaveLikeAccountERC7821({ deployable = true } = {}) {
   describe('executeUserOp', function () {
     beforeEach(async function () {
       // give eth to the account (before deployment)
@@ -157,13 +158,10 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
       // account is not initially deployed
       expect(ethers.provider.getCode(this.mock)).to.eventually.equal('0x');
 
-      this.encodeUserOpCalldata = (to, value, calldata) =>
-        ethers.concat([
-          this.mock.interface.getFunction('executeUserOp').selector,
-          ethers.solidityPacked(
-            ['address', 'uint256', 'bytes'],
-            [to.target ?? to.address ?? to, value ?? 0, calldata ?? '0x'],
-          ),
+      this.encodeUserOpCalldata = (...calls) =>
+        this.mock.interface.encodeFunctionData('execute', [
+          encodeMode({ callType: CALL_TYPE_BATCH }),
+          encodeBatch(...calls),
         ]);
     });
 
@@ -172,11 +170,10 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
 
       const operation = await this.mock
         .createUserOp({
-          callData: this.encodeUserOpCalldata(
-            this.target,
-            0,
-            this.target.interface.encodeFunctionData('mockFunctionExtra'),
-          ),
+          callData: this.encodeUserOpCalldata({
+            target: this.target,
+            data: this.target.interface.encodeFunctionData('mockFunctionExtra'),
+          }),
         })
         .then(op => this.signUserOp(op));
 
@@ -190,11 +187,11 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
         it('should be created with handleOps and increase nonce', async function () {
           const operation = await this.mock
             .createUserOp({
-              callData: this.encodeUserOpCalldata(
-                this.target,
-                17,
-                this.target.interface.encodeFunctionData('mockFunctionExtra'),
-              ),
+              callData: this.encodeUserOpCalldata({
+                target: this.target,
+                value: 17,
+                data: this.target.interface.encodeFunctionData('mockFunctionExtra'),
+              }),
             })
             .then(op => op.addInitCode())
             .then(op => this.signUserOp(op));
@@ -211,11 +208,11 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
         it('should revert if the signature is invalid', async function () {
           const operation = await this.mock
             .createUserOp({
-              callData: this.encodeUserOpCalldata(
-                this.target,
-                17,
-                this.target.interface.encodeFunctionData('mockFunctionExtra'),
-              ),
+              callData: this.encodeUserOpCalldata({
+                target: this.target,
+                value: 17,
+                data: this.target.interface.encodeFunctionData('mockFunctionExtra'),
+              }),
             })
             .then(op => op.addInitCode());
 
@@ -234,11 +231,11 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
       it('should increase nonce and call target', async function () {
         const operation = await this.mock
           .createUserOp({
-            callData: this.encodeUserOpCalldata(
-              this.target,
-              42,
-              this.target.interface.encodeFunctionData('mockFunctionExtra'),
-            ),
+            callData: this.encodeUserOpCalldata({
+              target: this.target,
+              value: 42,
+              data: this.target.interface.encodeFunctionData('mockFunctionExtra'),
+            }),
           })
           .then(op => this.signUserOp(op));
 
@@ -251,7 +248,7 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
 
       it('should support sending eth to an EOA', async function () {
         const operation = await this.mock
-          .createUserOp({ callData: this.encodeUserOpCalldata(this.other, value) })
+          .createUserOp({ callData: this.encodeUserOpCalldata({ target: this.other, value }) })
           .then(op => this.signUserOp(op));
 
         expect(this.mock.getNonce()).to.eventually.equal(0);
@@ -261,12 +258,36 @@ function shouldBehaveLikeAccountExecutor({ deployable = true } = {}) {
         );
         expect(this.mock.getNonce()).to.eventually.equal(1);
       });
+
+      it('should support batch execution', async function () {
+        const value1 = 43374337n;
+        const value2 = 69420n;
+
+        const operation = await this.mock
+          .createUserOp({
+            callData: this.encodeUserOpCalldata(
+              { target: this.other, value: value1 },
+              {
+                target: this.target,
+                value: value2,
+                data: this.target.interface.encodeFunctionData('mockFunctionExtra'),
+              },
+            ),
+          })
+          .then(op => this.signUserOp(op));
+
+        expect(this.mock.getNonce()).to.eventually.equal(0);
+        const tx = entrypoint.handleOps([operation.packed], this.beneficiary);
+        await expect(tx).to.changeEtherBalances([this.other, this.target], [value1, value2]);
+        await expect(tx).to.emit(this.target, 'MockFunctionCalledExtra').withArgs(this.mock, value2);
+        expect(this.mock.getNonce()).to.eventually.equal(1);
+      });
     });
   });
 }
 
 module.exports = {
   shouldBehaveLikeAccountCore,
   shouldBehaveLikeAccountHolder,
-  shouldBehaveLikeAccountExecutor,
+  shouldBehaveLikeAccountERC7821,
 };

test/account/AccountBase.test.js

@@ -3,7 +3,7 @@ const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 const { ERC4337Helper } = require('../helpers/erc4337');
 const { NonNativeSigner } = require('../helpers/signers');
 
-const { shouldBehaveLikeAccountCore, shouldBehaveLikeAccountExecutor } = require('./Account.behavior');
+const { shouldBehaveLikeAccountCore, shouldBehaveLikeAccountERC7821 } = require('./Account.behavior');
 
 async function fixture() {
   // EOAs and environment
@@ -32,5 +32,5 @@ describe('AccountBase', function () {
   });
 
   shouldBehaveLikeAccountCore();
-  shouldBehaveLikeAccountExecutor();
+  shouldBehaveLikeAccountERC7821();
 });

test/account/AccountECDSA.test.js

@@ -5,7 +5,7 @@ const { PackedUserOperation } = require('../helpers/eip712-types');
 
 const {
   shouldBehaveLikeAccountCore,
-  shouldBehaveLikeAccountExecutor,
+  shouldBehaveLikeAccountERC7821,
   shouldBehaveLikeAccountHolder,
 } = require('./Account.behavior');
 const { shouldBehaveLikeERC7739Signer } = require('../utils/cryptography/ERC7739Signer.behavior');
@@ -45,7 +45,7 @@ describe('AccountECDSA', function () {
   });
 
   shouldBehaveLikeAccountCore();
-  shouldBehaveLikeAccountExecutor();
+  shouldBehaveLikeAccountERC7821();
   shouldBehaveLikeAccountHolder();
 
   describe('ERC7739Signer', function () {

test/account/AccountERC7702.test.js

@@ -5,7 +5,7 @@ const { PackedUserOperation } = require('../helpers/eip712-types');
 
 const {
   shouldBehaveLikeAccountCore,
-  shouldBehaveLikeAccountExecutor,
+  shouldBehaveLikeAccountERC7821,
   shouldBehaveLikeAccountHolder,
 } = require('./Account.behavior');
 const { shouldBehaveLikeERC7739Signer } = require('../utils/cryptography/ERC7739Signer.behavior');
@@ -45,7 +45,7 @@ describe('AccountERC7702', function () {
   });
 
   shouldBehaveLikeAccountCore();
-  shouldBehaveLikeAccountExecutor({ deployable: false });
+  shouldBehaveLikeAccountERC7821({ deployable: false });
   shouldBehaveLikeAccountHolder();
 
   describe('ERC7739Signer', function () {

test/account/AccountP256.test.js

@@ -6,7 +6,7 @@ const { PackedUserOperation } = require('../helpers/eip712-types');
 
 const {
   shouldBehaveLikeAccountCore,
-  shouldBehaveLikeAccountExecutor,
+  shouldBehaveLikeAccountERC7821,
   shouldBehaveLikeAccountHolder,
 } = require('./Account.behavior');
 const { shouldBehaveLikeERC7739Signer } = require('../utils/cryptography/ERC7739Signer.behavior');
@@ -51,7 +51,7 @@ describe('AccountP256', function () {
   });
 
   shouldBehaveLikeAccountCore();
-  shouldBehaveLikeAccountExecutor();
+  shouldBehaveLikeAccountERC7821();
   shouldBehaveLikeAccountHolder();
 
   describe('ERC7739Signer', function () {

test/account/AccountRSA.test.js

@@ -6,7 +6,7 @@ const { PackedUserOperation } = require('../helpers/eip712-types');
 
 const {
   shouldBehaveLikeAccountCore,
-  shouldBehaveLikeAccountExecutor,
+  shouldBehaveLikeAccountERC7821,
   shouldBehaveLikeAccountHolder,
 } = require('./Account.behavior');
 const { shouldBehaveLikeERC7739Signer } = require('../utils/cryptography/ERC7739Signer.behavior');
@@ -51,7 +51,7 @@ describe('AccountRSA', function () {
   });
 
   shouldBehaveLikeAccountCore();
-  shouldBehaveLikeAccountExecutor();
+  shouldBehaveLikeAccountERC7821();
   shouldBehaveLikeAccountHolder();
 
   describe('ERC7739Signer', function () {