feat: avs registrar (#484)

**Motivation:**

We want to update the AVS registrar to be minimal & modular. 

**Modifications:**

Add a new `AVSRegistrar` with first class support with the
`KeyRegistrar`. We also have the following modules:
1. `SocketRegistry`
2. `AllowList`

The above modules are _abstract_ and are inherited by `AVSRegistrars` in
the `presets` folder: `AVSRegistrarWithAllowlist` and
`AVSRegistrarWithSocket`.

**Result:**

Simple AVSRegistrar. Note that we are still pending on the
`KeyRegistrar` interface update:
Layr-Labs/eigenlayer-contracts#1421

Author: ypatil12

lib/eigenlayer-contracts

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+interface IAVSRegistrarErrors {
+    /// @notice Thrown when a key is not registered
+    error KeyNotRegistered();
+    /// @notice Thrown when the caller is not the allocation manager
+    error NotAllocationManager();
+}
+
+interface IAVSRegistrarEvents {
+    /// @notice Emitted when a new operator is registered
+    event OperatorRegistered(address indexed operator, uint32[] operatorSetIds);
+
+    /// @notice Emitted when an operator is deregistered
+    event OperatorDeregistered(address indexed operator, uint32[] operatorSetIds);
+}
+
+/// @notice Since we have already defined a public interface, we add the events and errors here
+interface IAVSRegistrarInternal is IAVSRegistrarErrors, IAVSRegistrarEvents {}

src/interfaces/IAVSRegistrarInternal.sol

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity >=0.5.0;
+
+import {OperatorSet} from "eigenlayer-contracts/src/contracts/libraries/OperatorSetLib.sol";
+
+interface IAllowlistErrors {
+    /// @notice Thrown when the operator is already in the allowlist
+    error OperatorAlreadyInAllowlist();
+    /// @notice Thrown when the operator is not in the allowlist
+    error OperatorNotInAllowlist();
+}
+
+interface IAllowlistEvents {
+    /// @notice Emitted when an operator is added to the allowlist
+    event OperatorAddedToAllowlist(OperatorSet indexed operatorSet, address indexed operator);
+    /// @notice Emitted when an operator is removed from the allowlist
+    event OperatorRemovedFromAllowlist(OperatorSet indexed operatorSet, address indexed operator);
+}
+
+interface IAllowlist is IAllowlistErrors, IAllowlistEvents {
+    /**
+     * @notice Adds an operator to the allowlist
+     * @param operatorSet The operator set to add the operator to
+     * @param operator The operator to add to the allowlist
+     * @dev Only callable by the owner
+     */
+    function addOperatorToAllowlist(OperatorSet memory operatorSet, address operator) external;
+
+    /**
+     * @notice Removes an operator from the allowlist
+     * @param operatorSet The operator set to remove the operator from
+     * @param operator The operator to remove from the allowlist
+     * @dev If an operator is removed from the allowlist and is already registered, the avs
+     *      must then handle state changes appropriately (ie. eject the operator)
+     * @dev Only callable by the owner
+     */
+    function removeOperatorFromAllowlist(
+        OperatorSet memory operatorSet,
+        address operator
+    ) external;
+
+    /**
+     * @notice Checks if an operator is in the allowlist
+     * @param operatorSet The operator set to check the operator in
+     * @param operator The operator to check
+     * @return True if the operator is in the allowlist, false otherwise
+     */
+    function isOperatorAllowed(
+        OperatorSet memory operatorSet,
+        address operator
+    ) external view returns (bool);
+
+    /**
+     * @notice Returns all operators in the allowlist
+     * @param operatorSet The operator set to get the allowed operators from
+     * @return An array of all operators in the allowlist
+     * @dev This function should be used with caution, as it can be expensive to call on-chain
+     */
+    function getAllowedOperators(
+        OperatorSet memory operatorSet
+    ) external view returns (address[] memory);
+}

src/interfaces/IAllowlist.sol

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+import "eigenlayer-contracts/src/contracts/libraries/OperatorSetLib.sol";
+
+/// @notice A dummy interface for the KeyRegistrar
+interface IKeyRegistrar {
+    enum CurveType {
+        ECDSA,
+        BN254
+    }
+
+    function checkAndUpdateKey(
+        OperatorSet calldata operatorSet,
+        address operator
+    ) external returns (bool);
+
+    function removeKey(OperatorSet calldata operatorSet, address operator) external;
+
+    function isRegistered(
+        OperatorSet calldata operatorSet,
+        address operator
+    ) external view returns (bool);
+}

src/interfaces/IKeyRegistrar.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+interface ISocketRegistryErrors {
+    /// @notice Thrown when the caller is not the operator
+    error CallerNotOperator();
+
+    /// @notice Thrown when the data length mismatch
+    error DataLengthMismatch();
+}
+
+interface ISocketRegistryEvents {
+    /// @notice Emitted when an operator socket is set
+    event OperatorSocketSet(address indexed operator, string socket);
+}
+
+interface ISocketRegistry is ISocketRegistryErrors, ISocketRegistryEvents {
+    /**
+     * @notice Gets the socket for an operator.
+     * @param operator The operator to get the socket for.
+     * @return The socket for the operator.
+     */
+    function getOperatorSocket(
+        address operator
+    ) external view returns (string memory);
+
+    /**
+     * @notice Updates the socket for an operator.
+     * @param operator The operator to set the socket for.
+     * @param socket The socket to set for the operator.
+     * @dev This function can only be called by the operator themselves.
+     */
+    function updateSocket(address operator, string memory socket) external;
+}

src/interfaces/ISocketRegistryV2.sol

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+import {IAVSRegistrar} from "eigenlayer-contracts/src/contracts/interfaces/IAVSRegistrar.sol";
+import {IAllocationManager} from
+    "eigenlayer-contracts/src/contracts/interfaces/IAllocationManager.sol";
+import {
+    OperatorSetLib,
+    OperatorSet
+} from "eigenlayer-contracts/src/contracts/libraries/OperatorSetLib.sol";
+import {
+    IKeyRegistrarTypes,
+    IKeyRegistrar
+} from "eigenlayer-contracts/src/contracts/interfaces/IKeyRegistrar.sol";
+
+import {AVSRegistrarStorage} from "./AVSRegistrarStorage.sol";
+
+import {Initializable} from "@openzeppelin-upgrades/contracts/proxy/utils/Initializable.sol";
+
+/// @notice A minimal AVSRegistrar contract that is used to register/deregister operators for an AVS
+contract AVSRegistrar is Initializable, AVSRegistrarStorage {
+    using OperatorSetLib for OperatorSet;
+
+    modifier onlyAllocationManager() {
+        require(msg.sender == address(allocationManager), NotAllocationManager());
+        _;
+    }
+
+    constructor(
+        address _avs,
+        IAllocationManager _allocationManager,
+        IKeyRegistrar _keyRegistrar
+    ) AVSRegistrarStorage(_avs, _allocationManager, _keyRegistrar) {
+        _disableInitializers();
+    }
+
+    /// @inheritdoc IAVSRegistrar
+    function registerOperator(
+        address operator,
+        address avs,
+        uint32[] calldata operatorSetIds,
+        bytes calldata data
+    ) external virtual onlyAllocationManager {
+        _beforeRegisterOperator(operator, operatorSetIds, data);
+
+        // Check that the operator has a valid key and update key if needed
+        _validateOperatorKeys(operator, operatorSetIds);
+
+        _afterRegisterOperator(operator, operatorSetIds, data);
+
+        emit OperatorRegistered(operator, operatorSetIds);
+    }
+
+    /// @inheritdoc IAVSRegistrar
+    function deregisterOperator(
+        address operator,
+        address avs,
+        uint32[] calldata operatorSetIds
+    ) external virtual onlyAllocationManager {
+        _beforeDeregisterOperator(operator, operatorSetIds);
+
+        _afterDeregisterOperator(operator, operatorSetIds);
+
+        emit OperatorDeregistered(operator, operatorSetIds);
+    }
+
+    /// @inheritdoc IAVSRegistrar
+    function supportsAVS(
+        address _avs
+    ) public view virtual returns (bool) {
+        return _avs == avs;
+    }
+
+    /*
+     *
+     *                            INTERNAL FUNCTIONS
+     *
+     */
+
+    /**
+     * @notice Validates that the operator has registered a key for the given operator sets
+     * @param operator The operator to validate
+     * @param operatorSetIds The operator sets to validate
+     * @dev This function assumes the operator has already registered a key in the Key Registrar
+     */
+    function _validateOperatorKeys(address operator, uint32[] calldata operatorSetIds) internal {
+        for (uint32 i = 0; i < operatorSetIds.length; i++) {
+            OperatorSet memory operatorSet = OperatorSet({avs: avs, id: operatorSetIds[i]});
+            require(keyRegistrar.checkKey(operatorSet, operator), KeyNotRegistered());
+        }
+    }
+
+    /**
+     * @notice Hook called before the operator is registered
+     * @param operator The operator to register
+     * @param operatorSetIds The operator sets to register
+     * @param data The data to register
+     */
+    function _beforeRegisterOperator(
+        address operator,
+        uint32[] calldata operatorSetIds,
+        bytes calldata data
+    ) internal virtual {}
+
+    /**
+     * @notice Hook called after the operator is registered
+     * @param operator The operator to register
+     * @param operatorSetIds The operator sets to register
+     * @param data The data to register
+     */
+    function _afterRegisterOperator(
+        address operator,
+        uint32[] calldata operatorSetIds,
+        bytes calldata data
+    ) internal virtual {}
+
+    /**
+     * @notice Hook called before the operator is deregistered
+     * @param operator The operator to deregister
+     * @param operatorSetIds The operator sets to deregister
+     */
+    function _beforeDeregisterOperator(
+        address operator,
+        uint32[] calldata operatorSetIds
+    ) internal virtual {}
+
+    /**
+     * @notice Hook called after the operator is deregistered
+     * @param operator The operator to deregister
+     * @param operatorSetIds The operator sets to deregister
+     */
+    function _afterDeregisterOperator(
+        address operator,
+        uint32[] calldata operatorSetIds
+    ) internal virtual {}
+}

src/middlewareV2/registrar/AVSRegistrar.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+import {IAVSRegistrar} from "eigenlayer-contracts/src/contracts/interfaces/IAVSRegistrar.sol";
+import {IKeyRegistrar} from "eigenlayer-contracts/src/contracts/interfaces/IKeyRegistrar.sol";
+import {IAVSRegistrarInternal} from "../../interfaces/IAVSRegistrarInternal.sol";
+import {IAllocationManager} from
+    "eigenlayer-contracts/src/contracts/interfaces/IAllocationManager.sol";
+
+/// @notice A minimal storage contract for the AVSRegistrar
+abstract contract AVSRegistrarStorage is IAVSRegistrar, IAVSRegistrarInternal {
+    /**
+     *
+     *                            CONSTANTS AND IMMUTABLES
+     *
+     */
+
+    /// @notice The AVS that this registrar is for
+    /// @dev In practice, the AVS address in EigenLayer core is address that initialized the Metadata URI.
+    address public immutable avs;
+
+    /// @notice The allocation manager in EigenLayer core
+    IAllocationManager public immutable allocationManager;
+
+    /// @notice Pointer to the EigenLayer core Key Registrar
+    IKeyRegistrar public immutable keyRegistrar;
+
+    constructor(address _avs, IAllocationManager _allocationManager, IKeyRegistrar _keyRegistrar) {
+        avs = _avs;
+        allocationManager = _allocationManager;
+        keyRegistrar = _keyRegistrar;
+    }
+
+    /**
+     * @dev This empty reserved space is put in place to allow future versions to add new
+     * variables without shifting down storage in the inheritance chain.
+     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
+     */
+    uint256[50] private __GAP;
+}

src/middlewareV2/registrar/AVSRegistrarStorage.sol

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.27;
+
+import {IAllowlist} from "../../../interfaces/IAllowlist.sol";
+import {AllowlistStorage} from "./AllowlistStorage.sol";
+
+import {OwnableUpgradeable} from
+    "openzeppelin-contracts-upgradeable/contracts/access/OwnableUpgradeable.sol";
+import {EnumerableSetUpgradeable} from
+    "openzeppelin-contracts-upgradeable/contracts/utils/structs/EnumerableSetUpgradeable.sol";
+
+import {Initializable} from "@openzeppelin-upgrades/contracts/proxy/utils/Initializable.sol";
+import {
+    OperatorSet,
+    OperatorSetLib
+} from "eigenlayer-contracts/src/contracts/libraries/OperatorSetLib.sol";
+
+abstract contract Allowlist is OwnableUpgradeable, AllowlistStorage {
+    using OperatorSetLib for OperatorSet;
+    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.AddressSet;
+
+    function initialize(
+        address _owner
+    ) public virtual initializer {
+        _initializeAllowlist(_owner);
+    }
+
+    function _initializeAllowlist(
+        address _owner
+    ) internal onlyInitializing {
+        __Ownable_init();
+        _transferOwnership(_owner);
+    }
+
+    /// @inheritdoc IAllowlist
+    function addOperatorToAllowlist(
+        OperatorSet memory operatorSet,
+        address operator
+    ) external onlyOwner {
+        require(_allowedOperators[operatorSet.key()].add(operator), OperatorAlreadyInAllowlist());
+        emit OperatorAddedToAllowlist(operatorSet, operator);
+    }
+
+    /// @inheritdoc IAllowlist
+    function removeOperatorFromAllowlist(
+        OperatorSet memory operatorSet,
+        address operator
+    ) external onlyOwner {
+        require(_allowedOperators[operatorSet.key()].remove(operator), OperatorNotInAllowlist());
+        emit OperatorRemovedFromAllowlist(operatorSet, operator);
+    }
+
+    /// @inheritdoc IAllowlist
+    function isOperatorAllowed(
+        OperatorSet memory operatorSet,
+        address operator
+    ) public view returns (bool) {
+        return _allowedOperators[operatorSet.key()].contains(operator);
+    }
+
+    /// @inheritdoc IAllowlist
+    function getAllowedOperators(
+        OperatorSet memory operatorSet
+    ) external view returns (address[] memory) {
+        return _allowedOperators[operatorSet.key()].values();
+    }
+}