// SPDX-License-Identifier: MIT pragma solidity 0.8.16; import { AssetReceiver } from "../AssetReceiver.sol"; import { IDripCheck } from "./IDripCheck.sol"; /** * @title Drippie * @notice Drippie is a system for managing automated contract interactions. A specific interaction * is called a "drip" and can be executed according to some condition (called a dripcheck) * and an execution interval. Drips cannot be executed faster than the execution interval. * Drips can trigger arbitrary contract calls where the calling contract is this contract * address. Drips can also send ETH value, which makes them ideal for keeping addresses * sufficiently funded with ETH. Drippie is designed to be connected with smart contract * automation services so that drips can be executed automatically. However, Drippie is * specifically designed to be separated from these services so that trust assumptions are * better compartmentalized. */ contract Drippie is AssetReceiver { /** * @notice Enum representing different status options for a given drip. * * @custom:value NONE Drip does not exist. * @custom:value PAUSED Drip is paused and cannot be executed until reactivated. * @custom:value ACTIVE Drip is active and can be executed. * @custom:value ARCHIVED Drip is archived and can no longer be executed or reactivated. */ enum DripStatus { NONE, PAUSED, ACTIVE, ARCHIVED } /** * @notice Represents a drip action. */ struct DripAction { address payable target; bytes data; uint256 value; } /** * @notice Represents the configuration for a given drip. */ struct DripConfig { bool reentrant; uint256 interval; IDripCheck dripcheck; bytes checkparams; DripAction[] actions; } /** * @notice Represents the state of an active drip. */ struct DripState { DripStatus status; DripConfig config; uint256 last; uint256 count; } /** * @notice Emitted when a new drip is created. * * @param nameref Indexed name parameter (hashed). * @param name Unindexed name parameter (unhashed). * @param config Config for the created drip. */ event DripCreated( // Emit name twice because indexed version is hashed. string indexed nameref, string name, DripConfig config ); /** * @notice Emitted when a drip status is updated. * * @param nameref Indexed name parameter (hashed). * @param name Unindexed name parameter (unhashed). * @param status New drip status. */ event DripStatusUpdated( // Emit name twice because indexed version is hashed. string indexed nameref, string name, DripStatus status ); /** * @notice Emitted when a drip is executed. * * @param nameref Indexed name parameter (hashed). * @param name Unindexed name parameter (unhashed). * @param executor Address that executed the drip. * @param timestamp Time when the drip was executed. */ event DripExecuted( // Emit name twice because indexed version is hashed. string indexed nameref, string name, address executor, uint256 timestamp ); /** * @notice Maps from drip names to drip states. */ mapping(string => DripState) public drips; /** * @param _owner Initial contract owner. */ constructor(address _owner) AssetReceiver(_owner) {} /** * @notice Creates a new drip with the given name and configuration. Once created, drips cannot * be modified in any way (this is a security measure). If you want to update a drip, * simply pause (and potentially archive) the existing drip and create a new one. * * @param _name Name of the drip. * @param _config Configuration for the drip. */ function create(string calldata _name, DripConfig calldata _config) external onlyOwner { // Make sure this drip doesn't already exist. We *must* guarantee that no other function // will ever set the status of a drip back to NONE after it's been created. This is why // archival is a separate status. require( drips[_name].status == DripStatus.NONE, "Drippie: drip with that name already exists" ); // Validate the drip interval, only allowing an interval of zero if the drip has explicitly // been marked as reentrant. Prevents client-side bugs making a drip infinitely executable // within the same block (of course, restricted by gas limits). if (_config.reentrant) { require( _config.interval == 0, "Drippie: if allowing reentrant drip, must set interval to zero" ); } else { require( _config.interval > 0, "Drippie: interval must be greater than zero if drip is not reentrant" ); } // We initialize this way because Solidity won't let us copy arrays into storage yet. DripState storage state = drips[_name]; state.status = DripStatus.PAUSED; state.config.reentrant = _config.reentrant; state.config.interval = _config.interval; state.config.dripcheck = _config.dripcheck; state.config.checkparams = _config.checkparams; // Solidity doesn't let us copy arrays into storage, so we push each array one by one. for (uint256 i = 0; i < _config.actions.length; i++) { state.config.actions.push(_config.actions[i]); } // Tell the world! emit DripCreated(_name, _name, _config); } /** * @notice Sets the status for a given drip. The behavior of this function depends on the * status that the user is trying to set. A drip can always move between ACTIVE and * PAUSED, but it can never move back to NONE and once ARCHIVED, it can never move back * to ACTIVE or PAUSED. * * @param _name Name of the drip to update. * @param _status New drip status. */ function status(string calldata _name, DripStatus _status) external onlyOwner { // Make sure we can never set drip status back to NONE. A simple security measure to // prevent accidental overwrites if this code is ever updated down the line. require( _status != DripStatus.NONE, "Drippie: drip status can never be set back to NONE after creation" ); // Load the drip status once to avoid unnecessary SLOADs. DripStatus curr = drips[_name].status; // Make sure the drip in question actually exists. Not strictly necessary but there doesn't // seem to be any clear reason why you would want to do this, and it may save some gas in // the case of a front-end bug. require( curr != DripStatus.NONE, "Drippie: drip with that name does not exist and cannot be updated" ); // Once a drip has been archived, it cannot be un-archived. This is, after all, the entire // point of archiving a drip. require( curr != DripStatus.ARCHIVED, "Drippie: drip with that name has been archived and cannot be updated" ); // Although not strictly necessary, we make sure that the status here is actually changing. // This may save the client some gas if there's a front-end bug and the user accidentally // tries to "change" the status to the same value as before. require( curr != _status, "Drippie: cannot set drip status to the same status as its current status" ); // If the user is trying to archive this drip, make sure the drip has been paused. We do // not allow users to archive active drips so that the effects of this action are more // abundantly clear. if (_status == DripStatus.ARCHIVED) { require( curr == DripStatus.PAUSED, "Drippie: drip must first be paused before being archived" ); } // If we made it here then we can safely update the status. drips[_name].status = _status; emit DripStatusUpdated(_name, _name, _status); } /** * @notice Checks if a given drip is executable. * * @param _name Drip to check. * * @return True if the drip is executable, reverts otherwise. */ function executable(string calldata _name) public view returns (bool) { DripState storage state = drips[_name]; // Only allow active drips to be executed, an obvious security measure. require( state.status == DripStatus.ACTIVE, "Drippie: selected drip does not exist or is not currently active" ); // Don't drip if the drip interval has not yet elapsed since the last time we dripped. This // is a safety measure that prevents a malicious recipient from, e.g., spending all of // their funds and repeatedly requesting new drips. Limits the potential impact of a // compromised recipient to just a single drip interval, after which the drip can be paused // by the owner address. require( state.last + state.config.interval <= block.timestamp, "Drippie: drip interval has not elapsed since last drip" ); // Make sure we're allowed to execute this drip. require( state.config.dripcheck.check(state.config.checkparams), "Drippie: dripcheck failed so drip is not yet ready to be triggered" ); // Alright, we're good to execute. return true; } /** * @notice Triggers a drip. This function is deliberately left as a public function because the * assumption being made here is that setting the drip to ACTIVE is an affirmative * signal that the drip should be executable according to the drip parameters, drip * check, and drip interval. Note that drip parameters are read entirely from the state * and are not supplied as user input, so there should not be any way for a * non-authorized user to influence the behavior of the drip. Note that the drip check * is executed only **once** at the beginning of the call to the drip function and will * not be executed again between the drip actions within this call. * * @param _name Name of the drip to trigger. */ function drip(string calldata _name) external { DripState storage state = drips[_name]; // Make sure the drip can be executed. Since executable reverts if the drip is not ready to // be executed, we don't need to do an assertion that the returned value is true. executable(_name); // Update the last execution time for this drip before the call. Note that it's entirely // possible for a drip to be executed multiple times per block or even multiple times // within the same transaction (via re-entrancy) if the drip interval is set to zero. Users // should set a drip interval of 1 if they'd like the drip to be executed only once per // block (since this will then prevent re-entrancy). state.last = block.timestamp; // Update the number of times this drip has been executed. Although this increases the cost // of using Drippie, it slightly simplifies the client-side by not having to worry about // counting drips via events. Useful for monitoring the rate of drip execution. state.count++; // Execute each action in the drip. We allow drips to have multiple actions because there // are scenarios in which a contract must do multiple things atomically. For example, the // contract may need to withdraw ETH from one account and then deposit that ETH into // another account within the same transaction. uint256 len = state.config.actions.length; for (uint256 i = 0; i < len; i++) { // Must be marked as "storage" because copying structs into memory is not yet supported // by Solidity. Won't significantly reduce gas costs but at least makes it easier to // read what the rest of this section is doing. DripAction storage action = state.config.actions[i]; // Actually execute the action. We could use ExcessivelySafeCall here but not strictly // necessary (worst case, a drip gets bricked IFF the target is malicious, doubt this // will ever happen in practice). Could save a marginal amount of gas to ignore the // returndata. // slither-disable-next-line calls-loop (bool success, ) = action.target.call{ value: action.value }(action.data); // Generally should not happen, but could if there's a misconfiguration (e.g., passing // the wrong data to the target contract), the recipient is not payable, or // insufficient gas was supplied to this transaction. We revert so the drip can be // fixed and triggered again later. Means we cannot emit an event to alert of the // failure, but can reasonably be detected by off-chain services even without an event. // Note that this forces the drip executor to supply sufficient gas to the call // (assuming there is some sufficient gas limit that exists, otherwise the drip will // not execute). require( success, "Drippie: drip was unsuccessful, please check your configuration for mistakes" ); } emit DripExecuted(_name, _name, msg.sender, block.timestamp); } }