ERC20 Token Locker Smart Contract 🔒

This Solidity smart contract provides a secure and owner-controlled mechanism for locking ERC-20 tokens for a fixed period of 6 months. It's designed to be a single-file contract, embedding necessary OpenZeppelin functionalities for Ownable access control and SafeERC20 token interactions.

📄 Contract Overview

The ERC20Locker contract allows its owner to manage the vesting of various ERC-20 tokens. Once a vesting period is initiated for a specific token, all existing and newly direct-transferred balances of that token within the contract become locked for 6 months. After this period, the owner can withdraw the tokens. The contract also includes a safeguard to recover accidentally sent native currency (ETH).

✨ Features

• Owner-Controlled: Only the contract's deployer (the owner) can initiate token locks and withdraw funds.

• Flexible Token Inflow:

  • Push Mechanism (vest function): The owner can explicitly vest tokens by approving the contract and then calling the vest function. This initiates a new 6-month lock for the specified token.

  • Direct Transfers: Any ERC-20 tokens sent directly to the contract's address will be held. When the vest function is subsequently called for that token type, these directly transferred tokens are included in the total balance subject to the new 6-month lock.

• Unified 6-Month Lock: When vest is called for an ERC-20 token, it sets a 6-month lock-up period for all tokens of that type currently held by the contract. This means if a token was previously vested and new tokens are added (either by vest or direct transfer), calling vest again for that token will restart the 6-month timer for the entire balance.

• Time-Based Release: Tokens can only be withdrawn by the owner after their respective 6-month lock-up period (from the last vest call) has expired.

• ETH Recovery: A dedicated withdrawStuckETH function allows the owner to recover any native currency (ETH) that might be accidentally sent to the contract address.

• Gas Efficiency: Uses uint252 for timestamps where possible to optimize storage and gas costs.

• Embedded OpenZeppelin Libraries:

  • IERC20: Standard interface for ERC-20 tokens.

  • SafeERC20: Provides safe wrappers for ERC-20 token operations, mitigating common pitfalls and reentrancy risks.

  • SafeMathUpgradeable: Prevents integer overflow/underflow (though Solidity 0.8.0+ has built-in checks, it's included for robustness).

  • Context: Base contract providing _msgSender() and _msgData().

  • Ownable: Implements a simple access control mechanism, granting a single address (the owner) privileged functions.

🛠️ How to Use

Deployment

Deploy the ERC20Locker contract to Base Chain (or any EVM-compatible network) using tools like Remix, Hardhat, or Truffle. The address that deploys the contract will automatically become its owner.

Vesting Tokens

To vest ERC-20 tokens:

1. Approve the Locker Contract: The owner must first call the approve function on the specific ERC-20 token contract, granting the ERC20Locker contract permission to transfer a certain amount of tokens on their behalf.

   • Token Contract: IERC20_TOKEN_ADDRESS.approve(ERC20_LOCKER_CONTRACT_ADDRESS, AMOUNT_TO_APPROVE)

2. Call vest: The owner then calls the vest function on the ERC20Locker contract.

   • Locker Contract: ERC20_LOCKER_CONTRACT_ADDRESS.vest(IERC20_TOKEN_ADDRESS, AMOUNT_TO_VEST)

   • Note: AMOUNT_TO_VEST should be less than or equal to the AMOUNT_TO_APPROVE.

   • This will transfer AMOUNT_TO_VEST from the owner's balance to the locker contract and set a 6-month lock on the entire balance of that token currently held by the locker.

Releasing Vested Tokens

To withdraw vested tokens after the lock-up period:

1. Check Release Date: The owner can query getReleaseDate(IERC20_TOKEN_ADDRESS) to see when a specific token becomes available.

2. Call release: Once block.timestamp is greater than or equal to the releaseDate for a token, the owner can call the release function.

   • Locker Contract: ERC20_LOCKER_CONTRACT_ADDRESS.release(IERC20_TOKEN_ADDRESS)

   • This will transfer all tokens of that type from the contract to the owner's address and reset the releaseDate for that token to 0.

Withdrawing Stuck ETH

If native currency (ETH) is accidentally sent to the contract:

• Call withdrawStuckETH: The owner can call this function to retrieve all ETH held by the contract.

  • Locker Contract: ERC20_LOCKER_CONTRACT_ADDRESS.withdrawStuckETH()

Querying Contract State

• tokenBalance(IERC20_TOKEN_ADDRESS): Returns the current balance of a specific ERC-20 token held by the contract.

• getReleaseDate(IERC20_TOKEN_ADDRESS): Returns the Unix timestamp when a specific ERC-20 token becomes releasable. Returns 0 if no vesting period is currently set.

• owner(): Returns the address of the current contract owner.

• LOCK_DURATION: A public constant showing the lock duration in seconds.

⚠️ Security Considerations

• Owner Centralization: This contract relies heavily on the owner's address. If the owner's private key is compromised, the funds in the contract are at risk. Consider using a multi-signature wallet (e.g., Gnosis Safe) as the owner for enhanced security in a production environment.

• Single-Point-of-Failure for Vesting: The design where calling vest for a token restarts the 6-month timer for all of that token's balance (including previously direct-transferred amounts) means that a new vest call effectively delays the release of all existing tokens of that type. This is an intentional design choice for simplicity but should be understood.

• Gas Costs: While optimized, complex interactions on the blockchain always incur gas costs. Users should be aware of transaction fees on Base Chain.

• No Reentrancy: The release function follows the Checks-Effects-Interactions pattern and internally utilizes OpenZeppelin's SafeERC20 library to prevent common reentrancy vulnerabilities.

• Auditing: For any production deployment, a professional security audit of this contract is highly recommended to identify and mitigate potential vulnerabilities.

📜 Base Chain Ccontract 4 Airdrops

1 Month

6 Month

• 0x5f24CA85A2d00F51d32a2a4CA3e8587740dA76bc
• 0x4AeA93dB1697746723fFEa63d4a2175A6d4c2448
• 0x01Ea23e1640F7759Cd95CF4F7E6CA81a04B42dB6
• 0xE70D1D67A36d2eb51AA75CF8A37A495EFed96585
• 0x9200991Ab56ddc082b6b662fBb3794D119e66A02

1 Year

4 Years