Add EIP 1271 support to smart accounts. (#385)

* Add ERC-1271

* Add EIP 1271 support to smart accounts

Author: nkrishang

contracts/eip/ERC1271.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache 2.0
+pragma solidity ^0.8.0;
+
+abstract contract ERC1271 {
+    // bytes4(keccak256("isValidSignature(bytes32,bytes)")
+    bytes4 internal constant MAGICVALUE = 0x1626ba7e;
+
+    /**
+     * @dev Should return whether the signature provided is valid for the provided hash
+     * @param _hash      Hash of the data to be signed
+     * @param _signature Signature byte array associated with _hash
+     *
+     * MUST return the bytes4 magic value 0x1626ba7e when function passes.
+     * MUST NOT modify state (using STATICCALL for solc < 0.5, view modifier for solc > 0.5)
+     * MUST allow external calls
+     */
+    function isValidSignature(bytes32 _hash, bytes memory _signature) public view virtual returns (bytes4 magicValue);
+}

contracts/smart-wallet/non-upgradeable/Account.sol

@@ -15,6 +15,7 @@ import "../../dynamic-contracts/extension/PermissionsEnumerable.sol";
 import "../../dynamic-contracts/extension/ContractMetadata.sol";
 import "../../openzeppelin-presets/token/ERC721/utils/ERC721Holder.sol";
 import "../../openzeppelin-presets/token/ERC1155/utils/ERC1155Holder.sol";
+import "../../eip/ERC1271.sol";
 
 // Utils
 import "../../openzeppelin-presets/utils/cryptography/ECDSA.sol";
@@ -31,6 +32,7 @@ import "./AccountFactory.sol";
 
 contract Account is
     Initializable,
+    ERC1271,
     Multicall,
     BaseAccount,
     ContractMetadata,
@@ -106,6 +108,20 @@ contract Account is
         return hasRole(SIGNER_ROLE, _signer) || hasRole(DEFAULT_ADMIN_ROLE, _signer);
     }
 
+    /// @notice See EIP-1271
+    function isValidSignature(bytes32 _hash, bytes memory _signature)
+        public
+        view
+        virtual
+        override
+        returns (bytes4 magicValue)
+    {
+        address signer = _hash.recover(_signature);
+        if (isValidSigner(signer)) {
+            magicValue = MAGICVALUE;
+        }
+    }
+
     /*///////////////////////////////////////////////////////////////
                             External functions
     //////////////////////////////////////////////////////////////*/

contracts/smart-wallet/utils/AccountCore.sol

@@ -11,6 +11,7 @@ import "./../utils/BaseAccount.sol";
 // Fixed Extensions
 import "../../extension/Multicall.sol";
 import "../../dynamic-contracts/extension/Initializable.sol";
+import "../../eip/ERC1271.sol";
 
 // Utils
 import "../../openzeppelin-presets/utils/cryptography/ECDSA.sol";
@@ -25,7 +26,7 @@ import "../../dynamic-contracts/extension/PermissionsEnumerable.sol";
 //   \$$$$  |$$ |  $$ |$$ |$$ |      \$$$$$$$ |\$$$$$\$$$$  |\$$$$$$$\ $$$$$$$  |
 //    \____/ \__|  \__|\__|\__|       \_______| \_____\____/  \_______|\_______/
 
-contract AccountCore is Initializable, Multicall, BaseAccount {
+contract AccountCore is Initializable, Multicall, BaseAccount, ERC1271 {
     using ECDSA for bytes32;
 
     /*///////////////////////////////////////////////////////////////
@@ -73,6 +74,20 @@ contract AccountCore is Initializable, Multicall, BaseAccount {
         return _hasRole(SIGNER_ROLE, _signer) || _hasRole(DEFAULT_ADMIN_ROLE, _signer);
     }
 
+    /// @notice See EIP-1271
+    function isValidSignature(bytes32 _hash, bytes memory _signature)
+        public
+        view
+        virtual
+        override
+        returns (bytes4 magicValue)
+    {
+        address signer = _hash.recover(_signature);
+        if (isValidSigner(signer)) {
+            magicValue = MAGICVALUE;
+        }
+    }
+
     /*///////////////////////////////////////////////////////////////
                             External functions
     //////////////////////////////////////////////////////////////*/