Account

This directory includes contracts to build accounts for ERC-4337. These include:

  • Account: An ERC-4337 smart account implementation that includes the core logic to process user operations.

  • AccountERC7579: An extension of Account that implements support for ERC-7579 modules.

  • AccountERC7579Hooked: An extension of AccountERC7579 with support for a single hook module (type 4).

  • ERC7821: Minimal batch executor implementation contracts. Useful to enable easy batch execution for smart contracts.

  • ERC4337Utils: Utility functions for working with ERC-4337 user operations.

  • ERC7579Utils: Utility functions for working with ERC-7579 modules and account modularity.

  • Paymaster: An ERC-4337 paymaster implementation that includes the core logic to validate and pay for user operations.

  • PaymasterERC20: A paymaster that allows users to pay for user operations using ERC-20 tokens.

  • PaymasterERC20Guarantor: A paymaster that enables third parties to guarantee user operations by pre-funding gas costs, with the option for users to repay or for guarantors to absorb the cost.

  • PaymasterERC721Owner: A paymaster that sponsors user operations for ERC-721 token holders, covering gas costs based on NFT ownership.

  • PaymasterSigner: A paymaster that sponsors user operations authorized by a signature.

Core

Account 

import "@openzeppelin/contracts/account/Account.sol";

A simple ERC4337 account implementation. This base implementation only includes the minimal logic to process user operations.

Developers must implement the AbstractSigner._rawSignatureValidation function to define the account’s validation logic.

This core account doesn’t include any mechanism for performing arbitrary external calls. This is an essential feature that all Account should have. We leave it up to the developers to implement the mechanism of their choice. Common choices include ERC-6900, ERC-7579 and ERC-7821 (among others).
Implementing a mechanism to validate signatures is a security-sensitive operation as it may allow an attacker to bypass the account’s security measures. Check out SignerECDSA, SignerP256, or SignerRSA for digital signature validation implementations.

@custom:stateless

Modifiers
Functions
AbstractSigner
Errors

onlyEntryPointOrSelf() modifier

Revert if the caller is not the entry point or the account itself.

onlyEntryPoint() modifier

Revert if the caller is not the entry point.

entryPoint() → contract IEntryPoint public

Canonical entry point for the account that forwards and validates user operations.

getNonce() → uint256 public

Return the account nonce for the canonical sequence.

getNonce(uint192 key) → uint256 public

Return the account nonce for a given sequence (key).

validateUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, uint256 missingAccountFunds) → uint256 public

Validates a user operation.

  • MUST validate the caller is a trusted EntryPoint

  • MUST validate that the signature is a valid signature of the userOpHash, and SHOULD return SIG_VALIDATION_FAILED (and not revert) on signature mismatch. Any other error MUST revert.

  • MUST pay the entryPoint (caller) at least the “missingAccountFunds” (which might be zero, in case the current account’s deposit is high enough)

Returns an encoded packed validation data that is composed of the following elements:

  • authorizer (address): 0 for success, 1 for failure, otherwise the address of an authorizer contract

  • validUntil (uint48): The UserOp is valid only up to this time. Zero for “infinite”.

  • validAfter (uint48): The UserOp is valid only after this time.

_validateUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, bytes signature) → uint256 internal

Returns the validationData for a given user operation. By default, this checks the signature of the signable hash (produced by _signableUserOpHash) using the abstract signer (AbstractSigner._rawSignatureValidation).

The signature parameter is taken directly from the user operation’s signature field. This design enables derived contracts to implement custom signature handling logic, such as embedding additional data within the signature and processing it by overriding this function and optionally invoking super.

The userOpHash is assumed to be correct. Calling this function with a userOpHash that does not match the userOp will result in undefined behavior.

_signableUserOpHash(struct PackedUserOperation, bytes32 userOpHash) → bytes32 internal

Virtual function that returns the signable hash for a user operations. Since v0.8.0 of the entrypoint, userOpHash is an EIP-712 hash that can be signed directly.

_payPrefund(uint256 missingAccountFunds) internal

Sends the missing funds for executing the user operation to the entryPoint. The missingAccountFunds must be defined by the entrypoint when calling validateUserOp.

_checkEntryPoint() internal

Ensures the caller is the entryPoint.

_checkEntryPointOrSelf() internal

Ensures the caller is the entryPoint or the account itself.

receive() external

Receive Ether.

AccountUnauthorized(address sender) error

Unauthorized call to the account.

Extensions

AccountERC7579 

import "@openzeppelin/contracts/account/extensions/draft-AccountERC7579.sol";

Extension of Account that implements support for ERC-7579 modules.

To comply with the ERC-1271 support requirement, this contract defers signature validation to installed validator modules by calling IERC7579Validator.isValidSignatureWithSender.

This contract does not implement validation logic for user operations since this functionality is often delegated to self-contained validation modules. Developers must install a validator module upon initialization (or any other mechanism to enable execution from the account):

contract MyAccountERC7579 is AccountERC7579, Initializable {
  function initializeAccount(address validator, bytes calldata validatorData) public initializer {
    _installModule(MODULE_TYPE_VALIDATOR, validator, validatorData);
  }
}

  • Hook support is not included. See AccountERC7579Hooked for a version that hooks to execution.

  • Validator selection, when verifying either ERC-1271 signature or ERC-4337 UserOperation is implemented in internal virtual functions _extractUserOpValidator and _extractSignatureValidator. Both are implemented following common practices. However, this part is not standardized in ERC-7579 (or in any follow-up ERC). Some accounts may want to override these internal functions.

  • When combined with ERC7739, resolution ordering of isValidSignature may have an impact (ERC7739 does not call super). Manual resolution might be necessary.

  • Static calls (using callType 0xfe) are currently NOT supported.
Removing all validator modules will render the account inoperable, as no user operations can be validated thereafter.
Modifiers
Functions
Account
Events
IERC7579ModuleConfig
Errors
Account

onlyModule(uint256 moduleTypeId, bytes additionalContext) modifier

Modifier that checks if the caller is an installed module of the given type.

fallback(bytes) → bytes external

See _fallback.

accountId() → string public

Returns the account id of the smart account

supportsExecutionMode(bytes32 encodedMode) → bool public

Supported call types: * Single (0x00): A single transaction execution. * Batch (0x01): A batch of transactions execution. * Delegate (0xff): A delegate call execution.

Supported exec types: * Default (0x00): Default execution type (revert on failure). * Try (0x01): Try execution type (emits ERC7579TryExecuteFail on failure).

supportsModule(uint256 moduleTypeId) → bool public

Supported module types:

  • Validator: A module used during the validation phase to determine if a transaction is valid and should be executed on the account.

  • Executor: A module that can execute transactions on behalf of the smart account via a callback.

  • Fallback Handler: A module that can extend the fallback functionality of a smart account.

installModule(uint256 moduleTypeId, address module, bytes initData) public

Installs a Module of a certain type on the smart account

uninstallModule(uint256 moduleTypeId, address module, bytes deInitData) public

Uninstalls a Module of a certain type on the smart account

isModuleInstalled(uint256 moduleTypeId, address module, bytes additionalContext) → bool public

Returns whether a module is installed on the smart account

execute(bytes32 mode, bytes executionCalldata) public

Executes a transaction on behalf of the account.

executeFromExecutor(bytes32 mode, bytes executionCalldata) → bytes[] returnData public

Executes a transaction on behalf of the account. This function is intended to be called by Executor Modules

isValidSignature(bytes32 hash, bytes signature) → bytes4 public

Implement ERC-1271 through IERC7579Validator modules. If module based validation fails, fallback to "native" validation by the abstract signer.

when combined with ERC7739, resolution ordering may have an impact (ERC7739 does not call super). Manual resolution might be necessary.

_validateUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, bytes signature) → uint256 internal

Validates a user operation with _signableUserOpHash and returns the validation data if the module specified by the first 20 bytes of the nonce key is installed. Falls back to Account._validateUserOp otherwise.

See _extractUserOpValidator for the module extraction logic.

_execute(Mode mode, bytes executionCalldata) → bytes[] returnData internal

ERC-7579 execution logic. See supportsExecutionMode for supported modes.

Reverts if the call type is not supported.

_installModule(uint256 moduleTypeId, address module, bytes initData) internal

Installs a module of the given type with the given initialization data.

For the fallback module type, the initData is expected to be the (packed) concatenation of a 4-byte selector and the rest of the data to be sent to the handler when calling IERC7579Module.onInstall.

Requirements:

Emits a IERC7579ModuleConfig.ModuleInstalled event.

_uninstallModule(uint256 moduleTypeId, address module, bytes deInitData) internal

Uninstalls a module of the given type with the given de-initialization data.

For the fallback module type, the deInitData is expected to be the (packed) concatenation of a 4-byte selector and the rest of the data to be sent to the handler when calling IERC7579Module.onUninstall.

Requirements:

_fallback() → bytes internal

Fallback function that delegates the call to the installed handler for the given selector.

Reverts with ERC7579MissingFallbackHandler if the handler is not installed.

Calls the handler with the original msg.sender appended at the end of the calldata following the ERC-2771 format.

_fallbackHandler(bytes4 selector) → address internal

Returns the fallback handler for the given selector. Returns address(0) if not installed.

_checkModule(uint256 moduleTypeId, address module, bytes additionalContext) internal

Checks if the module is installed. Reverts if the module is not installed.

_extractUserOpValidator(struct PackedUserOperation userOp) → address internal

Extracts the nonce validator from the user operation.

To construct a nonce key, set nonce as follows:

<module address (20 bytes)> | <key (4 bytes)> | <nonce (8 bytes)>
The default behavior of this function replicates the behavior of Safe adapter, Etherspot’s Prime Account, and ERC7579 reference implementation.

This is not standardized in ERC-7579 (or in any follow-up ERC). Some accounts may want to override these internal functions.

For example, Biconomy’s Nexus uses a similar yet incompatible approach (the validator address is also part of the nonce, but not at the same location)

_extractSignatureValidator(bytes signature) → address module, bytes innerSignature internal

Extracts the signature validator from the signature.

To construct a signature, set the first 20 bytes as the module address and the remaining bytes as the signature data:

<module address (20 bytes)> | <signature data>
The default behavior of this function replicates the behavior of Safe adapter, Biconomy’s Nexus, Etherspot’s Prime Account, and ERC7579 reference implementation.

This is not standardized in ERC-7579 (or in any follow-up ERC). Some accounts may want to override these internal functions.

This function expects the signature to be at least 20 bytes long. Panics with Panic.ARRAY_OUT_OF_BOUNDS (0x32) otherwise.

_decodeFallbackData(bytes data) → bytes4 selector, bytes remaining internal

Extract the function selector from initData/deInitData for MODULE_TYPE_FALLBACK

If we had calldata here, we could use calldata slice which are cheaper to manipulate and don’t require actual copy. However, this would require _installModule to get a calldata bytes object instead of a memory bytes object. This would prevent calling _installModule from a contract constructor and would force the use of external initializers. That may change in the future, as most accounts will probably be deployed as clones/proxy/EIP-7702 delegates and therefore rely on initializers anyway.

_rawSignatureValidation(bytes32, bytes) → bool internal

By default, only use the modules for validation of userOp and signature. Disable raw signatures.

ERC7579MissingFallbackHandler(bytes4 selector) error

The account’s fallback was called with a selector that doesn’t have an installed handler.

ERC7579CannotDecodeFallbackData() error

The provided initData/deInitData for a fallback module is too short to extract a selector.

AccountERC7579Hooked 

import "@openzeppelin/contracts/account/extensions/draft-AccountERC7579Hooked.sol";

Extension of AccountERC7579 with support for a single hook module (type 4).

If installed, this extension will call the hook module’s IERC7579Hook.preCheck before executing any operation with _execute (including execute and executeFromExecutor by default) and IERC7579Hook.postCheck thereafter.

Hook modules break the check-effect-interaction pattern. In particular, the IERC7579Hook.preCheck hook can lead to potentially dangerous reentrancy. Using the withHook() modifier is safe if no effect is performed before the preHook or after the postHook. That is the case on all functions here, but it may not be the case if functions that have this modifier are overridden. Developers should be extremely careful when implementing hook modules or further overriding functions that involve hooks.
Modifiers
Functions
AccountERC7579
Account
Events
IERC7579ModuleConfig
Errors
AccountERC7579
Account

withHook() modifier

Calls IERC7579Hook.preCheck before executing the modified function and IERC7579Hook.postCheck thereafter.

accountId() → string public

Returns the account id of the smart account

hook() → address public

Returns the hook module address if installed, or address(0) otherwise.

supportsModule(uint256 moduleTypeId) → bool public

Supports hook modules. See AccountERC7579.supportsModule

isModuleInstalled(uint256 moduleTypeId, address module, bytes data) → bool public

Returns whether a module is installed on the smart account

_installModule(uint256 moduleTypeId, address module, bytes initData) internal

Installs a module with support for hook modules. See AccountERC7579._installModule

_uninstallModule(uint256 moduleTypeId, address module, bytes deInitData) internal

Uninstalls a module with support for hook modules. See AccountERC7579._uninstallModule

_execute(Mode mode, bytes executionCalldata) → bytes[] internal

Hooked version of AccountERC7579._execute.

_fallback() → bytes internal

Hooked version of AccountERC7579._fallback.

ERC7579HookModuleAlreadyPresent(address hook) error

A hook module is already present. This contract only supports one hook module.

ERC7821 

import "@openzeppelin/contracts/account/extensions/draft-ERC7821.sol";

Minimal batch executor following ERC-7821.

Only supports single batch mode (0x01000000000000000000). Does not support optional "opData".

@custom:stateless

Functions
Errors

execute(bytes32 mode, bytes executionData) public

Executes the calls in executionData with no optional opData support.

Access to this function is controlled by _erc7821AuthorizedExecutor. Changing access permissions, for example to approve calls by the ERC-4337 entrypoint, should be implemented by overriding it.

Reverts and bubbles up error if any call fails.

supportsExecutionMode(bytes32 mode) → bool result public

This function is provided for frontends to detect support. Only returns true for: - bytes32(0x01000000000000000000…​): does not support optional opData. - bytes32(0x01000000000078210001…​): supports optional opData.

_erc7821AuthorizedExecutor(address caller, bytes32, bytes) → bool internal

Access control mechanism for the execute function. By default, only the contract itself is allowed to execute.

Override this function to implement custom access control, for example to allow the ERC-4337 entrypoint to execute.

function _erc7821AuthorizedExecutor(
  address caller,
  bytes32 mode,
  bytes calldata executionData
) internal view virtual override returns (bool) {
  return caller == address(entryPoint()) || super._erc7821AuthorizedExecutor(caller, mode, executionData);
}

UnsupportedExecutionMode() error

Paymasters

Paymaster 

import "@openzeppelin/contracts/account/paymaster/Paymaster.sol";

A simple ERC4337 paymaster implementation. This base implementation only includes the minimal logic to validate and pay for user operations.

Developers must implement the Paymaster._validatePaymasterUserOp function to define the paymaster’s validation and payment logic, and Paymaster._postOp function to define the post-operation logic. The context parameter is used to pass data between the validation and post execution phases.

The paymaster includes support to call the IEntryPointStake interface to manage the paymaster’s deposits and stakes through the internal functions _deposit, _withdraw, _addStake, _unlockStake and _withdrawStake.

  • Deposits are used to pay for user operations.

  • Stakes are used to guarantee the paymaster’s reputation and obtain more flexibility in accessing storage.

The deposit and stake functions are internal so that developers can expose them under the public interface and authorization mechanism of their choice. Public versions of _withdraw, _unlockStake and _withdrawStake MUST be exposed and properly authorized, otherwise the deposit and stake will be permanently locked.

Example implementation exposing the deposit and stake functions using AccessControl:

contract MyPaymaster is Paymaster, AccessControl {
    bytes32 private constant WITHDRAWER_ROLE = keccak256("WITHDRAWER_ROLE");
    bytes32 private constant UNSTAKER_ROLE = keccak256("UNSTAKER_ROLE");

    constructor() {
        _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
    }

    function deposit() public payable virtual {
        _deposit(msg.value);
    }

    function withdraw(address payable to, uint256 value) public virtual onlyRole(WITHDRAWER_ROLE) {
        _withdraw(to, value);
    }

    function addStake(uint32 unstakeDelaySec) public payable virtual {
        _addStake(msg.value, unstakeDelaySec);
    }

    function unlockStake() public virtual onlyRole(UNSTAKER_ROLE) {
        _unlockStake();
    }

    function withdrawStake(address payable to) public virtual onlyRole(UNSTAKER_ROLE) {
        _withdrawStake(to);
    }

    function _validatePaymasterUserOp(
        PackedUserOperation calldata userOp,
        bytes32 userOpHash,
        uint256 requiredPreFund
    ) internal virtual override returns (bytes memory context, uint256 validationData) {
        // validation logic
    }
}
See [Paymaster’s unstaked reputation rules](https://eips.ethereum.org/EIPS/eip-7562#unstaked-paymasters-reputation-rules)  for more details on the paymaster’s storage access limitations.
Modifiers
Functions
Errors

onlyEntryPoint() modifier

Revert if the caller is not the entry point.

entryPoint() → contract IEntryPoint public

Canonical entry point for the account that forwards and validates user operations.

validatePaymasterUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, uint256 maxCost) → bytes context, uint256 validationData public

Validates whether the paymaster is willing to pay for the user operation. See IAccount.validateUserOp for additional information on the return value.

Bundlers will reject this method if it modifies the state, unless it’s whitelisted.

postOp(enum IPaymaster.PostOpMode mode, bytes context, uint256 actualGasCost, uint256 actualUserOpFeePerGas) public

Verifies the sender is the entrypoint.

_validatePaymasterUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, uint256 requiredPreFund) → bytes context, uint256 validationData internal

Internal validation of whether the paymaster is willing to pay for the user operation. Returns the context to be passed to postOp and the validation data.

The requiredPreFund is the amount the paymaster has to pay (in native tokens). It’s calculated as requiredGas * userOp.maxFeePerGas, where required gas can be calculated from the user operation as verificationGasLimit + callGasLimit + paymasterVerificationGasLimit + paymasterPostOpGasLimit + preVerificationGas

_postOp(enum IPaymaster.PostOpMode, bytes, uint256, uint256) internal

Handles post user operation execution logic. The caller must be the entry point.

It receives the context returned by _validatePaymasterUserOp. Function is not called if no context is returned by validatePaymasterUserOp.

The actualUserOpFeePerGas is not tx.gasprice. A user operation can be bundled with other transactions making the gas price of the user operation to differ.

_checkEntryPoint() internal

Ensures the caller is the entryPoint.

_deposit(uint256 value) internal

Calls IEntryPointStake.depositTo.

_withdraw(address payable to, uint256 value) internal

Calls IEntryPointStake.withdrawTo.

_addStake(uint256 value, uint32 unstakeDelaySec) internal

Calls IEntryPointStake.addStake.

_unlockStake() internal

Calls IEntryPointStake.unlockStake.

_withdrawStake(address payable to) internal

Calls IEntryPointStake.withdrawStake.

PaymasterUnauthorized(address sender) error

Unauthorized call to the paymaster.

PaymasterERC20 

import "@openzeppelin/contracts/account/paymaster/extensions/PaymasterERC20.sol";

Extension of Paymaster that enables users to pay gas with ERC-20 tokens.

To enable this feature, developers must implement the _fetchDetails function:

function _fetchDetails(
    PackedUserOperation calldata userOp,
    bytes32 userOpHash
) internal view override returns (uint256 validationData, IERC20 token, uint256 tokenPerNative) {
    // Implement logic to fetch the token, and token price from the userOp
}

The contract follows a pre-charge and refund model: 1. During validation, it pre-charges the maximum possible gas cost 2. After execution, it refunds any unused gas back to the user

_prefund performs a transferFrom during the validation phase, writing to the token contract’s storage. ERC-7562 restricts unstaked paymasters from such accesses, and public mempool bundlers will reject these operations. Stake the paymaster (see Paymaster._addStake) when deploying against a public mempool.

The _withdrawTokens function is internal so that developers can expose it under the public interface and authorization mechanism of their choice. Public versions of _withdrawTokens MUST be exposed and properly authorized, otherwise the tokens will be permanently stuck in the paymaster.

Example implementation exposing the _withdrawTokens function using AccessControl:

contract MyPaymaster is Paymaster, AccessControl {
    bytes32 private constant WITHDRAWER_ROLE = keccak256("WITHDRAWER_ROLE");

    constructor() {
        _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
    }

    function withdrawTokens(IERC20 token, address recipient, uint256 amount) public virtual onlyRole(WITHDRAWER_ROLE) {
        _withdrawTokens(token, recipient, amount);
    }

    ...
}
Functions
Paymaster
Events
Errors
Paymaster

_validatePaymasterUserOp(struct PackedUserOperation userOp, bytes32 userOpHash, uint256 maxCost) → bytes context, uint256 validationData internal

See Paymaster._validatePaymasterUserOp.

Attempts to retrieve the token and tokenPerNative from the user operation (see _fetchDetails) and prefund the user operation using these values and the maxCost argument (see _prefund).

Returns abi.encodePacked(userOpHash, token, tokenPerNative, prefundAmount, prefunder, prefundContext) in context if the prefund is successful. Otherwise, it returns empty bytes.

_prefund(struct PackedUserOperation, bytes32, contract IERC20 token, uint256, address prefunder_, uint256 prefundAmount_) → bool success, address prefunder, uint256 prefundAmount, bytes prefundContext internal

Charges prefundAmount of token from prefunder_ and returns the effective prefund actually pulled.

The base implementation pulls exactly the requested prefundAmount. Extensions may inflate the amount (e.g. a guarantor adds the cost of the extra postOp work it performs) and must return the effective value.

Returns (success, prefunder, effectivePrefundAmount, prefundContext). prefundContext is forwarded to _postOp through its context argument and may be used by overrides to carry data into _refund.

Consider not reverting if the prefund fails when overriding this function. This is to avoid reverting during the validation phase of the user operation, which may penalize the paymaster’s reputation according to ERC-7562 validation rules.

_postOp(enum IPaymaster.PostOpMode, bytes context, uint256 actualGasCost, uint256 actualUserOpFeePerGas) internal

Attempts to refund the user operation after execution. See _refund.

Reverts with PaymasterERC20FailedRefund if the refund fails.

This function may revert after the user operation has been executed without reverting the user operation itself. Consider implementing a mechanism to handle this case gracefully.

_refund(contract IERC20 token, uint256, uint256 actualAmount_, uint256, address prefunder, uint256 prefundAmount, bytes) → bool success, uint256 actualAmount internal

Refunds prefundAmount - actualAmount of token back to prefunder and returns the actualAmount actually charged.

actualAmount is pre-computed by _postOp via _erc20Cost. Extensions may change it (e.g. a guarantor adds its extra postOp cost or zeroes it out after pulling from the user) and must return the value that was effectively charged.

Requirements:

  • actualAmount ⇐ prefundAmount.

_fetchDetails(struct PackedUserOperation userOp, bytes32 userOpHash) → uint256 validationData, contract IERC20 token, uint256 tokenPerNative internal

Retrieves payment details for a user operation.

The values returned by this internal function are:

  • validationData: ERC-4337 validation data, indicating success/failure and optional time validity (validAfter, validUntil).

  • token: Address of the ERC-20 token used for payment to the paymaster.

  • tokenPerNative: Token units charged per unit of native currency. This is scaled by _tokenPerNativeDenominator() which defaults to 1e18 (wei per eth), making it effectively a number of token units per eth, and not per wei.

Calculating the token price

tokenPerNative is the multiplier _erc20Cost applies to a native-currency gas cost to produce a token amount: tokenAmount = (nativeCost * tokenPerNative) / _tokenPerNativeDenominator(). Each elements is denominated as follows:

  • tokenAmount: token units.

  • nativeCost: wei.

  • tokenPerNative: token units per eth.

  • _tokenPerNativeDenominator(): wei per native coin (1e18 on EVM chains).

For a token priced from USD oracles, derive tokenPerNative from the inverse exchange rate:

tokenPerNative = (<Native token price in $> / 1e18) / (<ERC-20 token price in $> / 10**<ERC-20 decimals>) * _tokenPerNativeDenominator()

For example, suppose the token is USDC ($1 with 6 decimals) and the native currency is ETH ($2524.86 with 18 decimals). Then 1 wei of gas costs (2524.86 / 1e18) / (1 / 1e6) = 2.52486e-9 USDC units, so with _tokenPerNativeDenominator() = 1e18 we have tokenPerNative = 2_524_860_000 (i.e. 2.52486e-9 * 1e18). Charging actualGasCost wei yields actualGasCost * 2_524_860_000 / 1e18 USDC units.

_postOpCost() → uint256 internal

Over-estimates the cost of the post-operation logic.

_tokenPerNativeDenominator() → uint256 internal

Denominator used for interpreting the tokenPerNative returned by _fetchDetails as "fixed point" in _erc20Cost.

_minTokensPerNative() → uint256 internal

Lower bound on tokenPerNative (see _fetchDetails for units). Operations whose tokenPerNative is strictly below this value are rejected with SIG_VALIDATION_FAILED before _prefund runs.

To pick a value, decide:

  • minCharge: smallest token amount you want to bill per op (e.g. 0.01 USDC = 10_000 units).

  • minGasCost: smallest actualGasCost + _postOpCost() * actualUserOpFeePerGas you expect, in wei (= minGas * minFeePerGas; minFeePerGas can be as low as 1 wei on some L2s).

Then set _minTokensPerNative() >= minCharge * _tokenPerNativeDenominator() / minGasCost.

Example: a USDC (6 decimals) paymaster on a chain with minFeePerGas = 1 gwei, sponsoring ops of at least 100_000 gas and charging at least 0.01 USDC per op:

function _minTokensPerNative() internal view override returns (uint256) {
    return 100e6; // = 1e4 (0.01 USDC) * 1e18 / 1e14 (100_000 gas * 1 gwei) = 100 USDC/ETH
}
Setting _minTokensPerNative() below minCharge * _tokenPerNativeDenominator() / minGasCost lets _erc20Cost round to zero or to dust for the cheapest ops the paymaster accepts, sponsoring them at a low (or zero) price.

_erc20Cost(uint256 nativeCost, uint256 tokenPerNative) → uint256 internal

Calculates native currency cost to ERC-20 token cost.

Returns type(uint256).max if computation overflows.

_withdrawTokens(contract IERC20 token, address recipient, uint256 amount) internal

Internal function that allows the withdrawer to extract ERC-20 tokens resulting from gas payments.

UserOperationSponsored(bytes32 indexed userOpHash, address indexed token, uint256 tokenAmount, uint256 tokenPerNative) event

Emitted when a user operation identified by userOpHash is sponsored by this paymaster using the specified ERC-20 token. The tokenAmount is the amount charged for the operation, and tokenPerNative is the valuation of the token in units of token per native currency (e.g., ETH).

PaymasterERC20FailedRefund(contract IERC20 token, uint256 prefundAmount, uint256 actualAmount, bytes prefundContext) error

Thrown when the paymaster fails to refund the difference between the prefundAmount and the actualAmount of token.

PaymasterERC20Guarantor 

import "@openzeppelin/contracts/account/paymaster/extensions/PaymasterERC20Guarantor.sol";

Extension of PaymasterERC20 that enables third parties to guarantee user operations.

This contract allows a guarantor to pre-fund user operations on behalf of users. The guarantor pays the maximum possible gas cost upfront, and after execution: 1. If the user repays the guarantor, the guarantor gets their funds back 2. If the user fails to repay, the guarantor absorbs the cost

A common use case is for guarantors to pay for the operations of users claiming airdrops. In this scenario:

  • The guarantor pays the gas fees upfront

  • The user claims their airdrop tokens

  • The user repays the guarantor from the claimed tokens

  • If the user fails to repay, the guarantor absorbs the cost

The guarantor is identified through the _fetchGuarantor function, which must be implemented by developers to determine who can guarantee operations. This allows for flexible guarantor selection logic based on the specific requirements of the application.

Functions
PaymasterERC20
Paymaster
Events
PaymasterERC20
Errors
PaymasterERC20
Paymaster

_prefund(struct PackedUserOperation userOp, bytes32 userOpHash, contract IERC20 token, uint256 tokenPrice, address prefunder_, uint256 prefundAmount_) → bool success, address prefunder, uint256 prefundAmount, bytes prefundContext internal

Prefunds the user operation using either the guarantor or the default prefunder, and appends userOp.sender to the tail of prefundContext so the refund process can identify the user operation sender.

For guaranteed ops, prefundAmount is inflated by _guaranteedPostOpCost worth of tokens so the prefund pulled from the guarantor covers the extra postOp work done in _refund (SafeERC20.trySafeTransferFrom from the user + SafeERC20.trySafeTransfer to the guarantor).

_refund(contract IERC20 token, uint256 tokenPrice, uint256 actualAmount, uint256 actualUserOpFeePerGas, address prefunder, uint256 prefundAmount, bytes prefundContext) → bool refunded, uint256 effectiveAmount internal

Handles the refund process for guaranteed operations.

  • Non-guaranteed (prefunder == userOp.sender): pass the base actualAmount through to PaymasterERC20._refund.

  • Guaranteed: augment actualAmount by _guaranteedPostOpCost * actualUserOpFeePerGas (priced in tokens), pull it from userOp.sender, and call PaymasterERC20._refund with actualAmount = 0 so the guarantor gets the full prefundAmount back. If the user fails to pay, the guarantor absorbs the GUARANTEED cost (not the base cost).

_fetchGuarantor(struct PackedUserOperation userOp) → address guarantor internal

Fetches the guarantor address and validation data from the user operation.

Return address(0) to disable the guarantor feature. If supported, ensure explicit consent (e.g., signature verification) to prevent unauthorized use.

_guaranteedPostOpCost() → uint256 internal

Over-estimates the cost of the post-operation logic. Added on top of PaymasterERC20._postOpCost for guaranteed userOps.

UserOperationGuaranteed(bytes32 indexed userOpHash, address indexed guarantor, uint256 prefundAmount) event

Emitted when a user operation identified by userOpHash is guaranteed by a guarantor for prefundAmount.

PaymasterERC721Owner 

import "@openzeppelin/contracts/account/paymaster/extensions/PaymasterERC721Owner.sol";

Extension of Paymaster that supports account based on ownership of an ERC-721 token.

This paymaster will sponsor user operations if the user has at least 1 token of the token specified during construction.

_validatePaymasterUserOp reads token.balanceOf during the validation phase, accessing storage in an external contract. ERC-7562 restricts unstaked paymasters from such accesses, and public mempool bundlers will reject these operations when the token contract is proxied or upgradeable. Stake the paymaster (see Paymaster._addStake) when deploying against a public mempool.
Functions
Paymaster
Errors
Paymaster

constructor(contract IERC721 token_) internal

token() → contract IERC721 public

ERC-721 token used to validate the user operation.

_validatePaymasterUserOp(struct PackedUserOperation userOp, bytes32, uint256) → bytes context, uint256 validationData internal

Internal validation of whether the paymaster is willing to pay for the user operation. Returns the context to be passed to postOp and the validation data.

The default context is bytes(0). Developers that add a context when overriding this function MUST also override _postOp to process the context passed along.

PaymasterSigner 

import "@openzeppelin/contracts/account/paymaster/extensions/PaymasterSigner.sol";

Extension of Paymaster that adds signature validation. See SignerECDSA, SignerP256 or SignerRSA.

Example of usage:

contract MyPaymasterECDSASigner is PaymasterSigner, SignerECDSA {
    constructor(address signerAddr) EIP712("MyPaymasterECDSASigner", "1") SignerECDSA(signerAddr) {}
}
Functions
Paymaster
EIP712
AbstractSigner
Events
IERC5267
Errors
Paymaster

_signableUserOpHash(struct PackedUserOperation userOp, uint48 validAfter, uint48 validUntil) → bytes32 internal

Virtual function that returns the signable hash for a user operations. Given the userOpHash contains the paymasterAndData itself, it’s not possible to sign that value directly. Instead, this function must be used to provide a custom mechanism to authorize an user operation.

_validatePaymasterUserOp(struct PackedUserOperation userOp, bytes32, uint256) → bytes context, uint256 validationData internal

Internal validation of whether the paymaster is willing to pay for the user operation. Returns the context to be passed to postOp and the validation data.

The context returned is bytes(0). Developers overriding this function MUST override _postOp to process the context passed along.

_decodePaymasterUserOp(struct PackedUserOperation userOp) → uint48 validAfter, uint48 validUntil, bytes signature internal

Decodes the user operation’s data from paymasterAndData.

Utilities

ERC4337Utils 

import "@openzeppelin/contracts/account/utils/ERC4337Utils.sol";

Library with common ERC-4337 utility functions.

See ERC-4337.

Functions
Internal Variables

parseValidationData(uint256 validationData) → address aggregator, uint48 validAfter, uint48 validUntil, enum ERC4337Utils.ValidationRange range internal

Parses the validation data into its components and the validity range. See packValidationData. Strips away the highest bit flag from the validAfter and validUntil fields.

packValidationData(address aggregator, uint48 validAfter, uint48 validUntil) → uint256 internal

Packs the validation data into a single uint256. See parseValidationData.

packValidationData(address aggregator, uint48 validAfter, uint48 validUntil, enum ERC4337Utils.ValidationRange range) → uint256 internal

Variant of packValidationData that forces which validity range to use. This overwrites the presence of flags in validAfter and validUntil).

packValidationData(bool sigSuccess, uint48 validAfter, uint48 validUntil) → uint256 internal

Variant of packValidationData that uses a boolean success flag instead of an aggregator address.

packValidationData(bool sigSuccess, uint48 validAfter, uint48 validUntil, enum ERC4337Utils.ValidationRange range) → uint256 internal

Variant of packValidationData that uses a boolean success flag instead of an aggregator address and that forces which validity range to use. This overwrites the presence of flags in validAfter and validUntil).

combineValidationData(uint256 validationData1, uint256 validationData2) → uint256 internal

Combines two validation data into a single one.

The aggregator is set to SIG_VALIDATION_SUCCESS if both are successful, while the validAfter is the maximum and the validUntil is the minimum of both.

Returns SIG_VALIDATION_FAILED if the validation ranges differ.

getValidationData(uint256 validationData) → address aggregator, bool outOfTimeRange internal

Returns the aggregator of the validationData and whether it is out of time range.

hash(struct PackedUserOperation self, address entrypoint) → bytes32 internal

Get the hash of a user operation for a given entrypoint

factory(struct PackedUserOperation self) → address internal

Returns factory from the PackedUserOperation, or address(0) if the initCode is empty or not properly formatted.

factoryData(struct PackedUserOperation self) → bytes internal

Returns factoryData from the PackedUserOperation, or empty bytes if the initCode is empty or not properly formatted.

verificationGasLimit(struct PackedUserOperation self) → uint256 internal

Returns verificationGasLimit from the PackedUserOperation.

callGasLimit(struct PackedUserOperation self) → uint256 internal

Returns callGasLimit from the PackedUserOperation.

maxPriorityFeePerGas(struct PackedUserOperation self) → uint256 internal

Returns the first section of gasFees from the PackedUserOperation.

maxFeePerGas(struct PackedUserOperation self) → uint256 internal

Returns the second section of gasFees from the PackedUserOperation.

gasPrice(struct PackedUserOperation self) → uint256 internal

Returns the total gas price for the PackedUserOperation (ie. maxFeePerGas or maxPriorityFeePerGas + basefee).

paymaster(struct PackedUserOperation self) → address internal

Returns the first section of paymasterAndData from the PackedUserOperation.

paymasterVerificationGasLimit(struct PackedUserOperation self) → uint256 internal

Returns the second section of paymasterAndData from the PackedUserOperation.

paymasterPostOpGasLimit(struct PackedUserOperation self) → uint256 internal

Returns the third section of paymasterAndData from the PackedUserOperation.

paymasterData(struct PackedUserOperation self) → bytes internal

Returns the fourth section of paymasterAndData from the PackedUserOperation. If a paymaster signature is present, it is excluded from the returned data.

paymasterSignature(struct PackedUserOperation self) → bytes internal

Returns the paymaster signature from paymasterAndData (EntryPoint v0.9+). Returns empty bytes if no paymaster signature is present.

contract IEntryPoint ENTRYPOINT_V07 internal constant

Address of the entrypoint v0.7.0

contract IEntryPoint ENTRYPOINT_V08 internal constant

Address of the entrypoint v0.8.0

contract IEntryPoint ENTRYPOINT_V09 internal constant

Address of the entrypoint v0.9.0

uint256 SIG_VALIDATION_SUCCESS internal constant

For simulation purposes, validateUserOp (and validatePaymasterUserOp) return this value on success.

uint256 SIG_VALIDATION_FAILED internal constant

For simulation purposes, validateUserOp (and validatePaymasterUserOp) must return this value in case of signature failure, instead of revert.

bytes8 PAYMASTER_SIG_MAGIC internal constant

Magic value used in EntryPoint v0.9+ to detect the presence of a paymaster signature in paymasterAndData.

uint48 BLOCK_RANGE_FLAG internal constant

Highest bit set to 1 in a 6-bytes field.

uint48 BLOCK_RANGE_MASK internal constant

Mask for the lower 47 bits of a 6-bytes field (equivalent to uint48(~BLOCK_RANGE_FLAG)).

ERC7579Utils 

import "@openzeppelin/contracts/account/utils/draft-ERC7579Utils.sol";

Library with common ERC-7579 utility functions.

See ERC-7579.

Functions
Events
Errors
Internal Variables

execSingle(bytes executionCalldata, ExecType execType) → bytes[] returnData internal

Executes a single call.

execBatch(bytes executionCalldata, ExecType execType) → bytes[] returnData internal

Executes a batch of calls.

execDelegateCall(bytes executionCalldata, ExecType execType) → bytes[] returnData internal

Executes a delegate call.

encodeMode(CallType callType, ExecType execType, ModeSelector selector, ModePayload payload) → Mode mode internal

Encodes the mode with the provided parameters. See decodeMode.

decodeMode(Mode mode) → CallType callType, ExecType execType, ModeSelector selector, ModePayload payload internal

Decodes the mode into its parameters. See encodeMode.

encodeSingle(address target, uint256 value, bytes callData) → bytes executionCalldata internal

Encodes a single call execution. See decodeSingle.

decodeSingle(bytes executionCalldata) → address target, uint256 value, bytes callData internal

Decodes a single call execution. See encodeSingle.

encodeDelegate(address target, bytes callData) → bytes executionCalldata internal

Encodes a delegate call execution. See decodeDelegate.

decodeDelegate(bytes executionCalldata) → address target, bytes callData internal

Decodes a delegate call execution. See encodeDelegate.

encodeBatch(struct Execution[] executionBatch) → bytes executionCalldata internal

Encodes a batch of executions. See decodeBatch.

decodeBatch(bytes executionCalldata) → struct Execution[] executionBatch internal

Decodes a batch of executions. See encodeBatch.

This function runs some checks and will throw a ERC7579DecodingError if the input is not properly formatted.

ERC7579TryExecuteFail(uint256 batchExecutionIndex, bytes returndata) event

Emits when an EXECTYPE_TRY execution fails.

ERC7579UnsupportedCallType(CallType callType) error

The provided CallType is not supported.

ERC7579UnsupportedExecType(ExecType execType) error

The provided ExecType is not supported.

ERC7579MismatchedModuleTypeId(uint256 moduleTypeId, address module) error

The provided module doesn’t match the provided module type.

ERC7579UninstalledModule(uint256 moduleTypeId, address module) error

The module is not installed.

ERC7579AlreadyInstalledModule(uint256 moduleTypeId, address module) error

The module is already installed.

ERC7579UnsupportedModuleType(uint256 moduleTypeId) error

The module type is not supported.

ERC7579DecodingError() error

Input calldata not properly formatted and possibly malicious.

CallType CALLTYPE_SINGLE internal constant

A single call execution.

CallType CALLTYPE_BATCH internal constant

A batch of call executions.

CallType CALLTYPE_DELEGATECALL internal constant

A delegatecall execution.

ExecType EXECTYPE_DEFAULT internal constant

Default execution type that reverts on failure.

ExecType EXECTYPE_TRY internal constant

Execution type that does not revert on failure.

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