ivcained/paymaster

Base paymaster

This repo contains a verifying paymaster contract that can be used for gas subsidies for ERC-4337 transactions. It contains a clone of the eth-infinitism VerifyingPaymaster with an additional receive() function for simple deposits.

Deployments

(More coming soon)

Network	Address
Base Goerli	0x88Ad254d5b1a95C9Bd2ae5F87E2BE27d95d86c2f

Obtaining a signature for use with the paymaster contract

If you'd like to use the paymaster to sponsor your 4337 user operations, follow these steps:

1. Construct your user operation, without a paymaster set.
2. (optional) Call estimate gas on your bundler of choice.
3. Add some headroom to make room for the paymaster verification gas. In our testing we've found the following values work, but it would depend on your bundler:
   1. op.PreVerificationGas = estimate.PreVerificationGas + 2600
   2. op.VerificationGasLimit = estimate.VerificationGasLimit + 16000
4. Call eth_paymasterAndDataForUserOperation JSON-RPC method on https://paymaster.base.org. Parameters:
   1. Object - the unsigned user operation
   2. string - the address of the entrypoint contract
   3. string - the chain ID, in hexadecimal

curl "https://paymaster.base.org" \
     -H 'content-type: application/json' \
     -d '
{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "eth_paymasterAndDataForUserOperation",
  "params": [
    {
      "sender": "0x0000000000000000000000000000000000000000",
      "nonce": "0x2a",
      "initCode": "0x",
      "callData": "0x",
      "callGasLimit": "0x1",
      "verificationGasLimit": "0x1",
      "preVerificationGas": "0x1",
      "maxFeePerGas": "0x1",
      "maxPriorityFeePerGas": "0x1"
    },
    "0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789",
    "0x14A33"
  ]
}
'

5. If the request is successful and the response contains a hex-encoded byte array, use that as the paymasterAndData field in the userOp. If an error is returned or the result is empty, the paymaster is not available for the given operation or chain. You can choose to proceed with another paymaster or self-funding the user operation.
6. Sign the user operation, and submit to your bundler of choice.

Note that the paymasterAndData returned in step 4 contains a signature of the provided userOp, so any modification of the userOp post step 4 (except for the sig field) will result in the paymaster rejecting the operation.