Singleton Paymaster

This repository contains an ERC-4337 paymaster implementation that allows users to sponsor their gas fees either with ERC-20 tokens (ERC-20 mode) or with their Pimlico balance (verifying mode).

Features

• ✅ Users paying with ERC-20 tokens for transaction fees
• ✅ Users paying with Pimlico balance
• ✅ Compatible with EntryPoint v0.7 and v0.6
• ✅ Optional ability to fund sender

Paymaster Architecture

This is a permissioned paymaster where the user will have to request sponsorship from Pimlico's API. If sponsorship is granted, the userOperation and all related fields are signed over by a designated signing key, this signature is then checked onchain.

ERC-20 Mode:

• The user (sender) pays for gas with ERC-20 tokens.
• The Pimlico API provides the exchange rate quote.

Verifying Mode:

• The user (sender) pays for gas with their Pimlico balance.

Note: In ERC-20 mode, the paymaster does not take a prefund during the validatePaymasterUserOp phase. This means that a malicious user can bypass the payment in the postOp call. If a user does this, the userOperation will be funded from their Pimlico balance.

MagicSpendPlusMinusHalf Architecture

src/MagicSpendPlusMinusHalf.sol is a simple permissioned implementation of MagicSpend. Users who have a valid signed WithdrawRequest can call the contracts requestWithdraw method to pull funds from. Before and after fulfilling the user's withdraw request, the contract will run pre and post calls. These calls are arbitrary and allow the contract to provide just in time liquidity by doing things such as swapping to the requested token at time of withdraw.

Core Contracts

Contract	Description
BasePaymaster	eth-infinitism's helper class for creating paymaster.
BaseSingletonPaymaster	Helper class with common functions for V6 and V7 implementations.
SingletonPaymasterV6	Singleton paymaster implementation (for EntryPoint v0.6).
SingletonPaymasterV7	Singleton paymaster implementation (for EntryPoint v0.7).

Tests And Coverage

Note: This repo contains two versions of OpenZeppelin Contracts v.5.0.2 (latest version at the time of writing) and v.4.8.3. The latest version is used in all contracts found in src, the older version is only used in tests. This is because EntryPoint v0.6 has OpenZeppelin@v.4.8.3 as a hard dependency.

Run the following

forge coverage --no-match-coverage test/utils