0xmic / SafeERC20

SafeERC20

In the Ethereum ecosystem, as token standards evolved and became more complex, developers encountered numerous edge cases and inconsistencies when integrating different tokens. SafeERC20 is a library designed to help address these issues, specifically those related to the ERC20 standard.

• OpenZeppelin Documentation
• OpenZeppelin Code

SafeERC20 Functions:

• safeTransfer(token, to, value)
• safeTransferFrom(token, from, to, value)
• safeApprove(token, spender, value)
• safeIncreaseAllowance(token, spender, value)
• safeDecreaseAllowance(token, spender, value)

Why SafeERC20 Exists

1. Inconsistent ERC20 Implementations: Not all ERC20 tokens strictly follow the standard. Some revert on failure while others return false. This inconsistency makes it challenging to write general-purpose code that could interact with any ERC20 token.

2. Lack of Return Values in Early ERC20: The original ERC20 standard didn't mandate transfer, transferFrom, and approve functions to return a boolean value indicating success or failure. Some tokens implemented these functions without return values, leading to potential silent failures.

3. Over-approval Issue: Calling approve with a non-zero value for the same spender more than once can expose users to an attack where the approved allowance can be manipulated by the spender in between the two approve calls.

Features of SafeERC20

1. Standardized Interface: SafeERC20 offers a consistent interface to interact with any ERC20 token, irrespective of its specific implementation.

2. Checks Return Value: SafeERC20 checks the return value of transfer, transferFrom, and approve. If a token doesn't return a value, it doesn't revert but handles appropriately. For tokens that return a value, it ensures that the value is true.

3. Safe Approve: To address the over-approval issue, the library first sets the allowance to 0 before setting it to a new value. This ensures that there's no risk of the double-spend problem in the gap between two approval operations.

When to Use SafeERC20

1. Broad Compatibility: If you're writing a contract that needs to interact with multiple ERC20 tokens, especially those not well-known or audited, using SafeERC20 can help ensure that your contract behaves correctly regardless of any peculiarities in the token's implementation.

2. Avoiding Edge Cases: When you want to avoid unexpected behavior or errors due to the inconsistent implementations of ERC20 tokens.

3. Security: If you want to ensure the best practices when calling approve and prevent potential attacks related to token allowances.

Summary

SafeERC20 emerged as a solution to real-world problems developers faced with inconsistent ERC20 token implementations. Using SafeERC20 is recommended when building applications or smart contracts that interact with a variety of ERC20 tokens to ensure consistent behavior, security, and to handle potential edge cases appropriately.