owner

AddedOwner

approvedHash

ApproveHash

handler

ChangedFallbackHandler

guard

ChangedGuard

threshold

ChangedThreshold

module

DisabledModule

EnabledModule

txHash

payment

ExecutionFailure

ExecutionFromModuleFailure

ExecutionFromModuleSuccess

ExecutionSuccess

RemovedOwner

sender

value

SafeReceived

initiator

owners

initializer

fallbackHandler

SafeSetup

msgHash

SignMsg

VERSION

_threshold

addOwnerWithThreshold

hashToApprove

approveHash

approvedHashes

changeThreshold

dataHash

data

signatures

requiredSignatures

checkNSignatures

checkSignatures

prevModule

disableModule

domainSeparator

enableModule

operation

safeTxGas

baseGas

gasPrice

gasToken

refundReceiver

_nonce

encodeTransactionData

execTransaction

success

execTransactionFromModule

execTransactionFromModuleReturnData

returnData

getChainId

start

pageSize

getModulesPaginated

array

getOwners

offset

length

getStorageAt

getThreshold

getTransactionHash

isModuleEnabled

isOwner

nonce

prevOwner

removeOwner

setFallbackHandler

setGuard

_owners

paymentToken

paymentReceiver

setup

signedMessages

targetContract

calldataPayload

simulateAndRevert

oldOwner

newOwner

swapOwner

The Safe contract is a multi-signature wallet that allows multiple owners to collectively manage and execute transactions. It supports features such as setting up the wallet, executing transactions with gas payment, handling signatures, and checking the validity of signatures. It also includes various modules for additional functionality and security.

Safe

Safe - A multisignature wallet with support for confirmations using signed messages based on EIP-712.

SafeModuleTransaction

additionalInfo

SafeMultiSigTransaction

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "./Safe.sol";

/**
 * @title SafeL2 - An implementation of the Safe contract that emits additional events on transaction executions.
 * @notice For a more complete description of the Safe contract, please refer to the main Safe contract `Safe.sol`.
 * @author Stefan George - @Georgi87
 * @author Richard Meissner - @rmeissner
 */
contract SafeL2 is Safe {
    event SafeMultiSigTransaction(
        address to,
        uint256 value,
        bytes data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver,
        bytes signatures,
        // We combine nonce, sender and threshold into one to avoid stack too deep
        // Dev note: additionalInfo should not contain `bytes`, as this complicates decoding
        bytes additionalInfo
    );

    event SafeModuleTransaction(address module, address to, uint256 value, bytes data, Enum.Operation operation);

    // @inheritdoc Safe
    function execTransaction(
        address to,
        uint256 value,
        bytes calldata data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver,
        bytes memory signatures
    ) public payable override returns (bool) {
        bytes memory additionalInfo;
        {
            additionalInfo = abi.encode(nonce, msg.sender, threshold);
        }
        emit SafeMultiSigTransaction(
            to,
            value,
            data,
            operation,
            safeTxGas,
            baseGas,
            gasPrice,
            gasToken,
            refundReceiver,
            signatures,
            additionalInfo
        );
        return super.execTransaction(to, value, data, operation, safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, signatures);
    }

    // @inheritdoc Safe
    function execTransactionFromModule(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation
    ) public override returns (bool success) {
        emit SafeModuleTransaction(msg.sender, to, value, data, operation);
        success = super.execTransactionFromModule(to, value, data, operation);
    }
}


The SafeL2 contract extends the Safe contract and adds events for multi-signature transactions and module transactions. It overrides the execTransaction and execTransactionFromModule functions to emit the respective events and call the parent contract's functions.

SafeL2

SafeL2 - An implementation of the Safe contract that emits additional events on transaction executions.

simulate

estimate

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../base/Executor.sol";

/**
 * @title Simulate Transaction Accessor.
 * @notice Can be used with StorageAccessible to simulate Safe transactions.
 * @author Richard Meissner - @rmeissner
 */
contract SimulateTxAccessor is Executor {
    address private immutable accessorSingleton;

    constructor() {
        accessorSingleton = address(this);
    }

    /**
     * @notice Modifier to make a function callable via delegatecall only.
     * If the function is called via a regular call, it will revert.
     */
    modifier onlyDelegateCall() {
        require(address(this) != accessorSingleton, "SimulateTxAccessor should only be called via delegatecall");
        _;
    }

    /**
     * @notice Simulates a Safe transaction and returns the used gas, success boolean and the return data.
     * @dev Executes the specified operation {Call, DelegateCall} and returns operation-specific data.
     *      Has to be called via delegatecall.
     *      This returns the data equal to `abi.encode(uint256(etimate), bool(success), bytes(returnData))`.
     *      Specifically, the returndata will be:
     *      `estimate:uint256 || success:bool || returnData.length:uint256 || returnData:bytes`.
     * @param to Destination address .
     * @param value Native token value.
     * @param data Data payload.
     * @param operation Operation type {Call, DelegateCall}.
     * @return estimate Gas used.
     * @return success Success boolean value.
     * @return returnData Return data.
     */
    function simulate(
        address to,
        uint256 value,
        bytes calldata data,
        Enum.Operation operation
    ) external onlyDelegateCall returns (uint256 estimate, bool success, bytes memory returnData) {
        uint256 startGas = gasleft();
        success = execute(to, value, data, operation, gasleft());
        estimate = startGas - gasleft();
        // solhint-disable-next-line no-inline-assembly
        assembly {
            // Load free memory location
            let ptr := mload(0x40)
            // We allocate memory for the return data by setting the free memory location to
            // current free memory location + data size + 32 bytes for data size value
            mstore(0x40, add(ptr, add(returndatasize(), 0x20)))
            // Store the size
            mstore(ptr, returndatasize())
            // Store the data
            returndatacopy(add(ptr, 0x20), 0, returndatasize())
            // Point the return data to the correct memory location
            returnData := ptr
        }
    }
}


SimulateTxAccessor

Simulate Transaction Accessor.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;
import "../common/Enum.sol";

/**
 * @title Executor - A contract that can execute transactions
 * @author Richard Meissner - @rmeissner
 */
abstract contract Executor {
    /**
     * @notice Executes either a delegatecall or a call with provided parameters.
     * @dev This method doesn't perform any sanity check of the transaction, such as:
     *      - if the contract at `to` address has code or not
     *      It is the responsibility of the caller to perform such checks.
     * @param to Destination address.
     * @param value Ether value.
     * @param data Data payload.
     * @param operation Operation type.
     * @return success boolean flag indicating if the call succeeded.
     */
    function execute(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation,
        uint256 txGas
    ) internal returns (bool success) {
        if (operation == Enum.Operation.DelegateCall) {
            // solhint-disable-next-line no-inline-assembly
            assembly {
                success := delegatecall(txGas, to, add(data, 0x20), mload(data), 0, 0)
            }
        } else {
            // solhint-disable-next-line no-inline-assembly
            assembly {
                success := call(txGas, to, value, add(data, 0x20), mload(data), 0, 0)
            }
        }
    }
}


Executor

Executor - A contract that can execute transactions

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../common/SelfAuthorized.sol";

/**
 * @title Fallback Manager - A contract managing fallback calls made to this contract
 * @author Richard Meissner - @rmeissner
 */
abstract contract FallbackManager is SelfAuthorized {
    event ChangedFallbackHandler(address indexed handler);

    // keccak256("fallback_manager.handler.address")
    bytes32 internal constant FALLBACK_HANDLER_STORAGE_SLOT = 0x6c9a6c4a39284e37ed1cf53d337577d14212a4870fb976a4366c693b939918d5;

    /**
     *  @notice Internal function to set the fallback handler.
     *  @param handler contract to handle fallback calls.
     */
    function internalSetFallbackHandler(address handler) internal {
        /*
            If a fallback handler is set to self, then the following attack vector is opened:
            Imagine we have a function like this:
            function withdraw() internal authorized {
                withdrawalAddress.call.value(address(this).balance)("");
            }

            If the fallback method is triggered, the fallback handler appends the msg.sender address to the calldata and calls the fallback handler.
            A potential attacker could call a Safe with the 3 bytes signature of a withdraw function. Since 3 bytes do not create a valid signature,
            the call would end in a fallback handler. Since it appends the msg.sender address to the calldata, the attacker could craft an address 
            where the first 3 bytes of the previous calldata + the first byte of the address make up a valid function signature. The subsequent call would result in unsanctioned access to Safe's internal protected methods.
            For some reason, solidity matches the first 4 bytes of the calldata to a function signature, regardless if more data follow these 4 bytes.
        */
        require(handler != address(this), "GS400");

        bytes32 slot = FALLBACK_HANDLER_STORAGE_SLOT;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(slot, handler)
        }
    }

    /**
     * @notice Set Fallback Handler to `handler` for the Safe.
     * @dev Only fallback calls without value and with data will be forwarded.
     *      This can only be done via a Safe transaction.
     *      Cannot be set to the Safe itself.
     * @param handler contract to handle fallback calls.
     */
    function setFallbackHandler(address handler) public authorized {
        internalSetFallbackHandler(handler);
        emit ChangedFallbackHandler(handler);
    }

    // @notice Forwards all calls to the fallback handler if set. Returns 0 if no handler is set.
    // @dev Appends the non-padded caller address to the calldata to be optionally used in the handler
    //      The handler can make us of `HandlerContext.sol` to extract the address.
    //      This is done because in the next call frame the `msg.sender` will be FallbackManager's address
    //      and having the original caller address may enable additional verification scenarios.
    // solhint-disable-next-line payable-fallback,no-complex-fallback
    fallback() external {
        bytes32 slot = FALLBACK_HANDLER_STORAGE_SLOT;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            let handler := sload(slot)
            if iszero(handler) {
                return(0, 0)
            }
            calldatacopy(0, 0, calldatasize())
            // The msg.sender address is shifted to the left by 12 bytes to remove the padding
            // Then the address without padding is stored right after the calldata
            mstore(calldatasize(), shl(96, caller()))
            // Add 20 bytes for the address appended add the end
            let success := call(gas(), handler, 0, 0, add(calldatasize(), 20), 0, 0)
            returndatacopy(0, 0, returndatasize())
            if iszero(success) {
                revert(0, returndatasize())
            }
            return(0, returndatasize())
        }
    }
}


FallbackManager

Fallback Manager - A contract managing fallback calls made to this contract

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../common/Enum.sol";
import "../common/SelfAuthorized.sol";
import "../interfaces/IERC165.sol";

interface Guard is IERC165 {
    function checkTransaction(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver,
        bytes memory signatures,
        address msgSender
    ) external;

    function checkAfterExecution(bytes32 txHash, bool success) external;
}

abstract contract BaseGuard is Guard {
    function supportsInterface(bytes4 interfaceId) external view virtual override returns (bool) {
        return
            interfaceId == type(Guard).interfaceId || // 0xe6d7a83a
            interfaceId == type(IERC165).interfaceId; // 0x01ffc9a7
    }
}

/**
 * @title Guard Manager - A contract managing transaction guards which perform pre and post-checks on Safe transactions.
 * @author Richard Meissner - @rmeissner
 */
abstract contract GuardManager is SelfAuthorized {
    event ChangedGuard(address indexed guard);

    // keccak256("guard_manager.guard.address")
    bytes32 internal constant GUARD_STORAGE_SLOT = 0x4a204f620c8c5ccdca3fd54d003badd85ba500436a431f0cbda4f558c93c34c8;

    /**
     * @dev Set a guard that checks transactions before execution
     *      This can only be done via a Safe transaction.
     *      ⚠️ IMPORTANT: Since a guard has full power to block Safe transaction execution,
     *        a broken guard can cause a denial of service for the Safe. Make sure to carefully
     *        audit the guard code and design recovery mechanisms.
     * @notice Set Transaction Guard `guard` for the Safe. Make sure you trust the guard.
     * @param guard The address of the guard to be used or the 0 address to disable the guard
     */
    function setGuard(address guard) external authorized {
        if (guard != address(0)) {
            require(Guard(guard).supportsInterface(type(Guard).interfaceId), "GS300");
        }
        bytes32 slot = GUARD_STORAGE_SLOT;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(slot, guard)
        }
        emit ChangedGuard(guard);
    }

    /**
     * @dev Internal method to retrieve the current guard
     *      We do not have a public method because we're short on bytecode size limit,
     *      to retrieve the guard address, one can use `getStorageAt` from `StorageAccessible` contract
     *      with the slot `GUARD_STORAGE_SLOT`
     * @return guard The address of the guard
     */
    function getGuard() internal view returns (address guard) {
        bytes32 slot = GUARD_STORAGE_SLOT;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            guard := sload(slot)
        }
    }
}


GuardManager

Guard Manager - A contract managing transaction guards which perform pre and post-checks on Safe transactions.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;
import "../common/Enum.sol";
import "../common/SelfAuthorized.sol";
import "./Executor.sol";

/**
 * @title Module Manager - A contract managing Safe modules
 * @notice Modules are extensions with unlimited access to a Safe that can be added to a Safe by its owners.
           ⚠️ WARNING: Modules are a security risk since they can execute arbitrary transactions, 
           so only trusted and audited modules should be added to a Safe. A malicious module can
           completely takeover a Safe.
 * @author Stefan George - @Georgi87
 * @author Richard Meissner - @rmeissner
 */
abstract contract ModuleManager is SelfAuthorized, Executor {
    event EnabledModule(address indexed module);
    event DisabledModule(address indexed module);
    event ExecutionFromModuleSuccess(address indexed module);
    event ExecutionFromModuleFailure(address indexed module);

    address internal constant SENTINEL_MODULES = address(0x1);

    mapping(address => address) internal modules;

    /**
     * @notice Setup function sets the initial storage of the contract.
     *         Optionally executes a delegate call to another contract to setup the modules.
     * @param to Optional destination address of call to execute.
     * @param data Optional data of call to execute.
     */
    function setupModules(address to, bytes memory data) internal {
        require(modules[SENTINEL_MODULES] == address(0), "GS100");
        modules[SENTINEL_MODULES] = SENTINEL_MODULES;
        if (to != address(0)) {
            require(isContract(to), "GS002");
            // Setup has to complete successfully or transaction fails.
            require(execute(to, 0, data, Enum.Operation.DelegateCall, type(uint256).max), "GS000");
        }
    }

    /**
     * @notice Enables the module `module` for the Safe.
     * @dev This can only be done via a Safe transaction.
     * @param module Module to be whitelisted.
     */
    function enableModule(address module) public authorized {
        // Module address cannot be null or sentinel.
        require(module != address(0) && module != SENTINEL_MODULES, "GS101");
        // Module cannot be added twice.
        require(modules[module] == address(0), "GS102");
        modules[module] = modules[SENTINEL_MODULES];
        modules[SENTINEL_MODULES] = module;
        emit EnabledModule(module);
    }

    /**
     * @notice Disables the module `module` for the Safe.
     * @dev This can only be done via a Safe transaction.
     * @param prevModule Previous module in the modules linked list.
     * @param module Module to be removed.
     */
    function disableModule(address prevModule, address module) public authorized {
        // Validate module address and check that it corresponds to module index.
        require(module != address(0) && module != SENTINEL_MODULES, "GS101");
        require(modules[prevModule] == module, "GS103");
        modules[prevModule] = modules[module];
        modules[module] = address(0);
        emit DisabledModule(module);
    }

    /**
     * @notice Execute `operation` (0: Call, 1: DelegateCall) to `to` with `value` (Native Token)
     * @dev Function is virtual to allow overriding for L2 singleton to emit an event for indexing.
     * @param to Destination address of module transaction.
     * @param value Ether value of module transaction.
     * @param data Data payload of module transaction.
     * @param operation Operation type of module transaction.
     * @return success Boolean flag indicating if the call succeeded.
     */
    function execTransactionFromModule(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation
    ) public virtual returns (bool success) {
        // Only whitelisted modules are allowed.
        require(msg.sender != SENTINEL_MODULES && modules[msg.sender] != address(0), "GS104");
        // Execute transaction without further confirmations.
        success = execute(to, value, data, operation, type(uint256).max);
        if (success) emit ExecutionFromModuleSuccess(msg.sender);
        else emit ExecutionFromModuleFailure(msg.sender);
    }

    /**
     * @notice Execute `operation` (0: Call, 1: DelegateCall) to `to` with `value` (Native Token) and return data
     * @param to Destination address of module transaction.
     * @param value Ether value of module transaction.
     * @param data Data payload of module transaction.
     * @param operation Operation type of module transaction.
     * @return success Boolean flag indicating if the call succeeded.
     * @return returnData Data returned by the call.
     */
    function execTransactionFromModuleReturnData(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation
    ) public returns (bool success, bytes memory returnData) {
        success = execTransactionFromModule(to, value, data, operation);
        // solhint-disable-next-line no-inline-assembly
        assembly {
            // Load free memory location
            let ptr := mload(0x40)
            // We allocate memory for the return data by setting the free memory location to
            // current free memory location + data size + 32 bytes for data size value
            mstore(0x40, add(ptr, add(returndatasize(), 0x20)))
            // Store the size
            mstore(ptr, returndatasize())
            // Store the data
            returndatacopy(add(ptr, 0x20), 0, returndatasize())
            // Point the return data to the correct memory location
            returnData := ptr
        }
    }

    /**
     * @notice Returns if an module is enabled
     * @return True if the module is enabled
     */
    function isModuleEnabled(address module) public view returns (bool) {
        return SENTINEL_MODULES != module && modules[module] != address(0);
    }

    /**
     * @notice Returns an array of modules.
     *         If all entries fit into a single page, the next pointer will be 0x1.
     *         If another page is present, next will be the last element of the returned array.
     * @param start Start of the page. Has to be a module or start pointer (0x1 address)
     * @param pageSize Maximum number of modules that should be returned. Has to be > 0
     * @return array Array of modules.
     * @return next Start of the next page.
     */
    function getModulesPaginated(address start, uint256 pageSize) external view returns (address[] memory array, address next) {
        require(start == SENTINEL_MODULES || isModuleEnabled(start), "GS105");
        require(pageSize > 0, "GS106");
        // Init array with max page size
        array = new address[](pageSize);

        // Populate return array
        uint256 moduleCount = 0;
        next = modules[start];
        while (next != address(0) && next != SENTINEL_MODULES && moduleCount < pageSize) {
            array[moduleCount] = next;
            next = modules[next];
            moduleCount++;
        }

        /**
          Because of the argument validation, we can assume that the loop will always iterate over the valid module list values
          and the `next` variable will either be an enabled module or a sentinel address (signalling the end). 
          
          If we haven't reached the end inside the loop, we need to set the next pointer to the last element of the modules array
          because the `next` variable (which is a module by itself) acting as a pointer to the start of the next page is neither 
          included to the current page, nor will it be included in the next one if you pass it as a start.
        */
        if (next != SENTINEL_MODULES) {
            next = array[moduleCount - 1];
        }
        // Set correct size of returned array
        // solhint-disable-next-line no-inline-assembly
        assembly {
            mstore(array, moduleCount)
        }
    }

    /**
     * @notice Returns true if `account` is a contract.
     * @dev This function will return false if invoked during the constructor of a contract,
     *      as the code is not actually created until after the constructor finishes.
     * @param account The address being queried
     */
    function isContract(address account) internal view returns (bool) {
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }
}


ModuleManager

Module Manager - A contract managing Safe modules

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;
import "../common/SelfAuthorized.sol";

/**
 * @title OwnerManager - Manages Safe owners and a threshold to authorize transactions.
 * @dev Uses a linked list to store the owners because the code generate by the solidity compiler
 *      is more efficient than using a dynamic array.
 * @author Stefan George - @Georgi87
 * @author Richard Meissner - @rmeissner
 */
abstract contract OwnerManager is SelfAuthorized {
    event AddedOwner(address indexed owner);
    event RemovedOwner(address indexed owner);
    event ChangedThreshold(uint256 threshold);

    address internal constant SENTINEL_OWNERS = address(0x1);

    mapping(address => address) internal owners;
    uint256 internal ownerCount;
    uint256 internal threshold;

    /**
     * @notice Sets the initial storage of the contract.
     * @param _owners List of Safe owners.
     * @param _threshold Number of required confirmations for a Safe transaction.
     */
    function setupOwners(address[] memory _owners, uint256 _threshold) internal {
        // Threshold can only be 0 at initialization.
        // Check ensures that setup function can only be called once.
        require(threshold == 0, "GS200");
        // Validate that threshold is smaller than number of added owners.
        require(_threshold <= _owners.length, "GS201");
        // There has to be at least one Safe owner.
        require(_threshold >= 1, "GS202");
        // Initializing Safe owners.
        address currentOwner = SENTINEL_OWNERS;
        for (uint256 i = 0; i < _owners.length; i++) {
            // Owner address cannot be null.
            address owner = _owners[i];
            require(owner != address(0) && owner != SENTINEL_OWNERS && owner != address(this) && currentOwner != owner, "GS203");
            // No duplicate owners allowed.
            require(owners[owner] == address(0), "GS204");
            owners[currentOwner] = owner;
            currentOwner = owner;
        }
        owners[currentOwner] = SENTINEL_OWNERS;
        ownerCount = _owners.length;
        threshold = _threshold;
    }

    /**
     * @notice Adds the owner `owner` to the Safe and updates the threshold to `_threshold`.
     * @dev This can only be done via a Safe transaction.
     * @param owner New owner address.
     * @param _threshold New threshold.
     */
    function addOwnerWithThreshold(address owner, uint256 _threshold) public authorized {
        // Owner address cannot be null, the sentinel or the Safe itself.
        require(owner != address(0) && owner != SENTINEL_OWNERS && owner != address(this), "GS203");
        // No duplicate owners allowed.
        require(owners[owner] == address(0), "GS204");
        owners[owner] = owners[SENTINEL_OWNERS];
        owners[SENTINEL_OWNERS] = owner;
        ownerCount++;
        emit AddedOwner(owner);
        // Change threshold if threshold was changed.
        if (threshold != _threshold) changeThreshold(_threshold);
    }

    /**
     * @notice Removes the owner `owner` from the Safe and updates the threshold to `_threshold`.
     * @dev This can only be done via a Safe transaction.
     * @param prevOwner Owner that pointed to the owner to be removed in the linked list
     * @param owner Owner address to be removed.
     * @param _threshold New threshold.
     */
    function removeOwner(address prevOwner, address owner, uint256 _threshold) public authorized {
        // Only allow to remove an owner, if threshold can still be reached.
        require(ownerCount - 1 >= _threshold, "GS201");
        // Validate owner address and check that it corresponds to owner index.
        require(owner != address(0) && owner != SENTINEL_OWNERS, "GS203");
        require(owners[prevOwner] == owner, "GS205");
        owners[prevOwner] = owners[owner];
        owners[owner] = address(0);
        ownerCount--;
        emit RemovedOwner(owner);
        // Change threshold if threshold was changed.
        if (threshold != _threshold) changeThreshold(_threshold);
    }

    /**
     * @notice Replaces the owner `oldOwner` in the Safe with `newOwner`.
     * @dev This can only be done via a Safe transaction.
     * @param prevOwner Owner that pointed to the owner to be replaced in the linked list
     * @param oldOwner Owner address to be replaced.
     * @param newOwner New owner address.
     */
    function swapOwner(address prevOwner, address oldOwner, address newOwner) public authorized {
        // Owner address cannot be null, the sentinel or the Safe itself.
        require(newOwner != address(0) && newOwner != SENTINEL_OWNERS && newOwner != address(this), "GS203");
        // No duplicate owners allowed.
        require(owners[newOwner] == address(0), "GS204");
        // Validate oldOwner address and check that it corresponds to owner index.
        require(oldOwner != address(0) && oldOwner != SENTINEL_OWNERS, "GS203");
        require(owners[prevOwner] == oldOwner, "GS205");
        owners[newOwner] = owners[oldOwner];
        owners[prevOwner] = newOwner;
        owners[oldOwner] = address(0);
        emit RemovedOwner(oldOwner);
        emit AddedOwner(newOwner);
    }

    /**
     * @notice Changes the threshold of the Safe to `_threshold`.
     * @dev This can only be done via a Safe transaction.
     * @param _threshold New threshold.
     */
    function changeThreshold(uint256 _threshold) public authorized {
        // Validate that threshold is smaller than number of owners.
        require(_threshold <= ownerCount, "GS201");
        // There has to be at least one Safe owner.
        require(_threshold >= 1, "GS202");
        threshold = _threshold;
        emit ChangedThreshold(threshold);
    }

    /**
     * @notice Returns the number of required confirmations for a Safe transaction aka the threshold.
     * @return Threshold number.
     */
    function getThreshold() public view returns (uint256) {
        return threshold;
    }

    /**
     * @notice Returns if `owner` is an owner of the Safe.
     * @return Boolean if owner is an owner of the Safe.
     */
    function isOwner(address owner) public view returns (bool) {
        return owner != SENTINEL_OWNERS && owners[owner] != address(0);
    }

    /**
     * @notice Returns a list of Safe owners.
     * @return Array of Safe owners.
     */
    function getOwners() public view returns (address[] memory) {
        address[] memory array = new address[](ownerCount);

        // populate return array
        uint256 index = 0;
        address currentOwner = owners[SENTINEL_OWNERS];
        while (currentOwner != SENTINEL_OWNERS) {
            array[index] = currentOwner;
            currentOwner = owners[currentOwner];
            index++;
        }
        return array;
    }
}


OwnerManager

OwnerManager - Manages Safe owners and a threshold to authorize transactions.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title Enum - Collection of enums used in Safe contracts.
 * @author Richard Meissner - @rmeissner
 */
abstract contract Enum {
    enum Operation {
        Call,
        DelegateCall
    }
}


Enum

Enum - Collection of enums used in Safe contracts.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title NativeCurrencyPaymentFallback - A contract that has a fallback to accept native currency payments.
 * @author Richard Meissner - @rmeissner
 */
abstract contract NativeCurrencyPaymentFallback {
    event SafeReceived(address indexed sender, uint256 value);

    /**
     * @notice Receive function accepts native currency transactions.
     * @dev Emits an event with sender and received value.
     */
    receive() external payable {
        emit SafeReceived(msg.sender, msg.value);
    }
}


NativeCurrencyPaymentFallback

NativeCurrencyPaymentFallback - A contract that has a fallback to accept native currency payments.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title SecuredTokenTransfer - Secure token transfer.
 * @author Richard Meissner - @rmeissner
 */
abstract contract SecuredTokenTransfer {
    /**
     * @notice Transfers a token and returns a boolean if it was a success
     * @dev It checks the return data of the transfer call and returns true if the transfer was successful.
     *      It doesn't check if the `token` address is a contract or not.
     * @param token Token that should be transferred
     * @param receiver Receiver to whom the token should be transferred
     * @param amount The amount of tokens that should be transferred
     * @return transferred Returns true if the transfer was successful
     */
    function transferToken(address token, address receiver, uint256 amount) internal returns (bool transferred) {
        // 0xa9059cbb - keccack("transfer(address,uint256)")
        bytes memory data = abi.encodeWithSelector(0xa9059cbb, receiver, amount);
        // solhint-disable-next-line no-inline-assembly
        assembly {
            // We write the return value to scratch space.
            // See https://docs.soliditylang.org/en/v0.7.6/internals/layout_in_memory.html#layout-in-memory
            let success := call(sub(gas(), 10000), token, 0, add(data, 0x20), mload(data), 0, 0x20)
            switch returndatasize()
            case 0 {
                transferred := success
            }
            case 0x20 {
                transferred := iszero(or(iszero(success), iszero(mload(0))))
            }
            default {
                transferred := 0
            }
        }
    }
}


SecuredTokenTransfer

SecuredTokenTransfer - Secure token transfer.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title SelfAuthorized - Authorizes current contract to perform actions to itself.
 * @author Richard Meissner - @rmeissner
 */
abstract contract SelfAuthorized {
    function requireSelfCall() private view {
        require(msg.sender == address(this), "GS031");
    }

    modifier authorized() {
        // Modifiers are copied around during compilation. This is a function call as it minimized the bytecode size
        requireSelfCall();
        _;
    }
}


SelfAuthorized

SelfAuthorized - Authorizes current contract to perform actions to itself.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title SignatureDecoder - Decodes signatures encoded as bytes
 * @author Richard Meissner - @rmeissner
 */
abstract contract SignatureDecoder {
    /**
     * @notice Splits signature bytes into `uint8 v, bytes32 r, bytes32 s`.
     * @dev Make sure to perform a bounds check for @param pos, to avoid out of bounds access on @param signatures
     *      The signature format is a compact form of {bytes32 r}{bytes32 s}{uint8 v}
     *      Compact means uint8 is not padded to 32 bytes.
     * @param pos Which signature to read.
     *            A prior bounds check of this parameter should be performed, to avoid out of bounds access.
     * @param signatures Concatenated {r, s, v} signatures.
     * @return v Recovery ID or Safe signature type.
     * @return r Output value r of the signature.
     * @return s Output value s of the signature.
     */
    function signatureSplit(bytes memory signatures, uint256 pos) internal pure returns (uint8 v, bytes32 r, bytes32 s) {
        // solhint-disable-next-line no-inline-assembly
        assembly {
            let signaturePos := mul(0x41, pos)
            r := mload(add(signatures, add(signaturePos, 0x20)))
            s := mload(add(signatures, add(signaturePos, 0x40)))
            /**
             * Here we are loading the last 32 bytes, including 31 bytes
             * of 's'. There is no 'mload8' to do this.
             * 'byte' is not working due to the Solidity parser, so lets
             * use the second best option, 'and'
             */
            v := and(mload(add(signatures, add(signaturePos, 0x41))), 0xff)
        }
    }
}


SignatureDecoder

SignatureDecoder - Decodes signatures encoded as bytes

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title Singleton - Base for singleton contracts (should always be the first super contract)
 *        This contract is tightly coupled to our proxy contract (see `proxies/SafeProxy.sol`)
 * @author Richard Meissner - @rmeissner
 */
abstract contract Singleton {
    // singleton always has to be the first declared variable to ensure the same location as in the Proxy contract.
    // It should also always be ensured the address is stored alone (uses a full word)
    address private singleton;
}


Singleton

Singleton - Base for singleton contracts (should always be the first super contract)        This contract is tightly coupled to our proxy contract (see `proxies/SafeProxy.sol`)

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title StorageAccessible - A generic base contract that allows callers to access all internal storage.
 * @notice See https://github.com/gnosis/util-contracts/blob/bb5fe5fb5df6d8400998094fb1b32a178a47c3a1/contracts/StorageAccessible.sol
 *         It removes a method from the original contract not needed for the Safe contracts.
 * @author Gnosis Developers
 */
abstract contract StorageAccessible {
    /**
     * @notice Reads `length` bytes of storage in the currents contract
     * @param offset - the offset in the current contract's storage in words to start reading from
     * @param length - the number of words (32 bytes) of data to read
     * @return the bytes that were read.
     */
    function getStorageAt(uint256 offset, uint256 length) public view returns (bytes memory) {
        bytes memory result = new bytes(length * 32);
        for (uint256 index = 0; index < length; index++) {
            // solhint-disable-next-line no-inline-assembly
            assembly {
                let word := sload(add(offset, index))
                mstore(add(add(result, 0x20), mul(index, 0x20)), word)
            }
        }
        return result;
    }

    /**
     * @dev Performs a delegatecall on a targetContract in the context of self.
     * Internally reverts execution to avoid side effects (making it static).
     *
     * This method reverts with data equal to `abi.encode(bool(success), bytes(response))`.
     * Specifically, the `returndata` after a call to this method will be:
     * `success:bool || response.length:uint256 || response:bytes`.
     *
     * @param targetContract Address of the contract containing the code to execute.
     * @param calldataPayload Calldata that should be sent to the target contract (encoded method name and arguments).
     */
    function simulateAndRevert(address targetContract, bytes memory calldataPayload) external {
        // solhint-disable-next-line no-inline-assembly
        assembly {
            let success := delegatecall(gas(), targetContract, add(calldataPayload, 0x20), mload(calldataPayload), 0, 0)

            mstore(0x00, success)
            mstore(0x20, returndatasize())
            returndatacopy(0x40, 0, returndatasize())
            revert(0, add(returndatasize(), 0x40))
        }
    }
}


StorageAccessible

StorageAccessible - A generic base contract that allows callers to access all internal storage.

safe

GasUsage

usesRefund

executor

TransactionDetails

checkAfterExecution

checkTransaction

interfaceId

supportsInterface

txNonces

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../../common/Enum.sol";
import "../../base/GuardManager.sol";
import "../../Safe.sol";

/**
 * @title Debug Transaction Guard - Emits transaction events with extended information.
 * @dev This guard is only meant as a development tool and example
 * @author Richard Meissner - @rmeissner
 */
contract DebugTransactionGuard is BaseGuard {
    // solhint-disable-next-line payable-fallback
    fallback() external {
        // We don't revert on fallback to avoid issues in case of a Safe upgrade
        // E.g. The expected check method might change and then the Safe would be locked.
    }

    event TransactionDetails(
        address indexed safe,
        bytes32 indexed txHash,
        address to,
        uint256 value,
        bytes data,
        Enum.Operation operation,
        uint256 safeTxGas,
        bool usesRefund,
        uint256 nonce,
        bytes signatures,
        address executor
    );

    event GasUsage(address indexed safe, bytes32 indexed txHash, uint256 indexed nonce, bool success);

    mapping(bytes32 => uint256) public txNonces;

    /**
     * @notice Called by the Safe contract before a transaction is executed.
     * @param to Destination address of Safe transaction.
     * @param value Ether value of Safe transaction.
     * @param data Data payload of Safe transaction.
     * @param operation Operation type of Safe transaction.
     * @param safeTxGas Gas that should be used for the Safe transaction.
     * @param baseGas Gas costs that are independent of the transaction execution (e.g. base transaction fee, signature check, payment of the refund)
     * @param gasPrice Gas price that should be used for the payment calculation.
     * @param gasToken Token address (or 0 if ETH) that is used for the payment.
     * @param refundReceiver Address of receiver of gas payment (or 0 if tx.origin).
     * @param signatures Signature data that should be verified. Can be packed ECDSA signature ({bytes32 r}{bytes32 s}{uint8 v}), contract signature (EIP-1271) or approved hash.
     * @param executor Account executing the transaction.
     */
    function checkTransaction(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        // solhint-disable-next-line no-unused-vars
        address payable refundReceiver,
        bytes memory signatures,
        address executor
    ) external override {
        uint256 nonce;
        bytes32 txHash;
        {
            Safe safe = Safe(payable(msg.sender));
            nonce = safe.nonce() - 1;
            txHash = safe.getTransactionHash(to, value, data, operation, safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, nonce);
        }
        emit TransactionDetails(msg.sender, txHash, to, value, data, operation, safeTxGas, gasPrice > 0, nonce, signatures, executor);
        txNonces[txHash] = nonce;
    }

    /**
     * @notice Called by the Safe contract after a transaction is executed.
     * @param txHash Hash of the executed transaction.
     * @param success True if the transaction was successful.
     */
    function checkAfterExecution(bytes32 txHash, bool success) external override {
        uint256 nonce = txNonces[txHash];
        require(nonce != 0, "Could not get nonce");
        txNonces[txHash] = 0;
        emit GasUsage(msg.sender, txHash, nonce, success);
    }
}


DebugTransactionGuard

Debug Transaction Guard - Emits transaction events with extended information.

target

allowedTarget

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../../common/Enum.sol";
import "../../base/GuardManager.sol";
import "../../Safe.sol";

/**
 * @title DelegateCallTransactionGuard - Limits delegate calls to a specific target.
 * @author Richard Meissner - @rmeissner
 */
contract DelegateCallTransactionGuard is BaseGuard {
    address public immutable allowedTarget;

    constructor(address target) {
        allowedTarget = target;
    }

    // solhint-disable-next-line payable-fallback
    fallback() external {
        // We don't revert on fallback to avoid issues in case of a Safe upgrade
        // E.g. The expected check method might change and then the Safe would be locked.
    }

    /**
     * @notice Called by the Safe contract before a transaction is executed.
     * @dev  Reverts if the transaction is a delegate call to contract other than the allowed one.
     * @param to Destination address of Safe transaction.
     * @param operation Operation type of Safe transaction.
     */
    function checkTransaction(
        address to,
        uint256,
        bytes memory,
        Enum.Operation operation,
        uint256,
        uint256,
        uint256,
        address,
        // solhint-disable-next-line no-unused-vars
        address payable,
        bytes memory,
        address
    ) external view override {
        require(operation != Enum.Operation.DelegateCall || to == allowedTarget, "This call is restricted");
    }

    function checkAfterExecution(bytes32, bool) external view override {}
}


DelegateCallTransactionGuard

DelegateCallTransactionGuard - Limits delegate calls to a specific target.

msgSender

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../../common/Enum.sol";
import "../../base/GuardManager.sol";
import "../../Safe.sol";

interface ISafe {
    function getOwners() external view returns (address[] memory);
}

/**
 * @title OnlyOwnersGuard - Only allows owners to execute transactions.
 * @author Richard Meissner - @rmeissner
 */
contract OnlyOwnersGuard is BaseGuard {
    ISafe public safe;

    constructor() {}

    // solhint-disable-next-line payable-fallback
    fallback() external {
        // We don't revert on fallback to avoid issues in case of a Safe upgrade
        // E.g. The expected check method might change and then the Safe would be locked.
    }

    /**
     * @notice Called by the Safe contract before a transaction is executed.
     * @dev Reverts if the transaction is not executed by an owner.
     * @param msgSender Executor of the transaction.
     */
    function checkTransaction(
        address,
        uint256,
        bytes memory,
        Enum.Operation,
        uint256,
        uint256,
        uint256,
        address,
        // solhint-disable-next-line no-unused-vars
        address payable,
        bytes memory,
        address msgSender
    ) external view override {
        // Only owners can exec
        address[] memory owners = ISafe(msg.sender).getOwners();
        for (uint256 i = 0; i < owners.length; i++) {
            if (owners[i] == msgSender) {
                return;
            }
        }

        // msg sender is not an owner
        revert("msg sender is not allowed to exec");
    }

    function checkAfterExecution(bytes32, bool) external view override {}
}


OnlyOwnersGuard

OnlyOwnersGuard - Only allows owners to execute transactions.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../../common/Enum.sol";
import "../../base/GuardManager.sol";
import "../../Safe.sol";

/**
 * @title ReentrancyTransactionGuard - Prevents reentrancy into the transaction execution function.
 * @author Richard Meissner - @rmeissner
 */
contract ReentrancyTransactionGuard is BaseGuard {
    bytes32 internal constant GUARD_STORAGE_SLOT = keccak256("reentrancy_guard.guard.struct");

    struct GuardValue {
        bool active;
    }

    // solhint-disable-next-line payable-fallback
    fallback() external {
        // We don't revert on fallback to avoid issues in case of a Safe upgrade
        // E.g. The expected check method might change and then the Safe would be locked.
    }

    /**
     * @notice Returns the guard value for the current context.
     * @dev The guard value is stored in a slot that is unique to the contract instance and the function in which it is called.
     * @return guard The guard value.
     */
    function getGuard() internal pure returns (GuardValue storage guard) {
        bytes32 slot = GUARD_STORAGE_SLOT;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            guard.slot := slot
        }
    }

    /**
     * @notice Called by the Safe contract before a transaction is executed.
     * @dev Reverts if reentrancy is detected.
     */
    function checkTransaction(
        address,
        uint256,
        bytes memory,
        Enum.Operation,
        uint256,
        uint256,
        uint256,
        address,
        // solhint-disable-next-line no-unused-vars
        address payable,
        bytes memory,
        address
    ) external override {
        GuardValue storage guard = getGuard();
        require(!guard.active, "Reentrancy detected");
        guard.active = true;
    }

    /**
     * @notice Called by the Safe contract after a transaction is executed.
     * @dev Resets the guard value.
     */
    function checkAfterExecution(bytes32, bool) external override {
        getGuard().active = false;
    }
}


ReentrancyTransactionGuard

ReentrancyTransactionGuard - Prevents reentrancy into the transaction execution function.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;
import "../../libraries/SafeStorage.sol";

/**
 * @title Migration - Migrates a Safe contract from 1.3.0 to 1.2.0
 * @author Richard Meissner - @rmeissner
 */
contract Migration is SafeStorage {
    bytes32 private constant DOMAIN_SEPARATOR_TYPEHASH = 0x035aff83d86937d35b32e04f0ddc6ff469290eef2f1b692d8a815c89404d4749;

    address public immutable migrationSingleton;
    address public immutable safe120Singleton;

    constructor(address targetSingleton) {
        // Singleton address cannot be zero address.
        require(targetSingleton != address(0), "Invalid singleton address provided");
        safe120Singleton = targetSingleton;
        migrationSingleton = address(this);
    }

    event ChangedMasterCopy(address singleton);

    /**
     * @notice Migrates the Safe to the Singleton contract at `migrationSingleton`.
     * @dev This can only be called via a delegatecall.
     */
    function migrate() public {
        require(address(this) != migrationSingleton, "Migration should only be called via delegatecall");

        singleton = safe120Singleton;
        _deprecatedDomainSeparator = keccak256(abi.encode(DOMAIN_SEPARATOR_TYPEHASH, this));
        emit ChangedMasterCopy(singleton);
    }
}


// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title SafeMath
 * @notice Math operations with safety checks that revert on error (overflow/underflow)
 */
library SafeMath {
    /**
     * @notice Multiplies two numbers, reverts on overflow.
     * @param a First number
     * @param b Second number
     * @return Product of a and b
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
     * @notice Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
     * @param a First number
     * @param b Second number
     * @return Difference of a and b
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
     * @notice Adds two numbers, reverts on overflow.
     * @param a First number
     * @param b Second number
     * @return Sum of a and b
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
     * @notice Returns the largest of two numbers.
     * @param a First number
     * @param b Second number
     * @return Largest of a and b
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }
}


SafeMath

message

encodeMessageDataForSafe

getMessageHash

getMessageHashForSafe

getModules

_dataHash

_signature

isValidSignature

_data

onERC1155BatchReceived

onERC1155Received

onERC721Received

response

tokensReceived

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "./TokenCallbackHandler.sol";
import "../interfaces/ISignatureValidator.sol";
import "../Safe.sol";

/**
 * @title Compatibility Fallback Handler - Provides compatibility between pre 1.3.0 and 1.3.0+ Safe contracts.
 * @author Richard Meissner - @rmeissner
 */
contract CompatibilityFallbackHandler is TokenCallbackHandler, ISignatureValidator {
    // keccak256("SafeMessage(bytes message)");
    bytes32 private constant SAFE_MSG_TYPEHASH = 0x60b3cbf8b4a223d68d641b3b6ddf9a298e7f33710cf3d3a9d1146b5a6150fbca;

    bytes4 internal constant SIMULATE_SELECTOR = bytes4(keccak256("simulate(address,bytes)"));

    address internal constant SENTINEL_MODULES = address(0x1);
    bytes4 internal constant UPDATED_MAGIC_VALUE = 0x1626ba7e;

    /**
     * @notice Legacy EIP-1271 signature validation method.
     * @dev Implementation of ISignatureValidator (see `interfaces/ISignatureValidator.sol`)
     * @param _data Arbitrary length data signed on the behalf of address(msg.sender).
     * @param _signature Signature byte array associated with _data.
     * @return The EIP-1271 magic value.
     */
    function isValidSignature(bytes memory _data, bytes memory _signature) public view override returns (bytes4) {
        // Caller should be a Safe
        Safe safe = Safe(payable(msg.sender));
        bytes memory messageData = encodeMessageDataForSafe(safe, _data);
        bytes32 messageHash = keccak256(messageData);
        if (_signature.length == 0) {
            require(safe.signedMessages(messageHash) != 0, "Hash not approved");
        } else {
            safe.checkSignatures(messageHash, messageData, _signature);
        }
        return EIP1271_MAGIC_VALUE;
    }

    /**
     * @dev Returns the hash of a message to be signed by owners.
     * @param message Raw message bytes.
     * @return Message hash.
     */
    function getMessageHash(bytes memory message) public view returns (bytes32) {
        return getMessageHashForSafe(Safe(payable(msg.sender)), message);
    }

    /**
     * @dev Returns the pre-image of the message hash (see getMessageHashForSafe).
     * @param safe Safe to which the message is targeted.
     * @param message Message that should be encoded.
     * @return Encoded message.
     */
    function encodeMessageDataForSafe(Safe safe, bytes memory message) public view returns (bytes memory) {
        bytes32 safeMessageHash = keccak256(abi.encode(SAFE_MSG_TYPEHASH, keccak256(message)));
        return abi.encodePacked(bytes1(0x19), bytes1(0x01), safe.domainSeparator(), safeMessageHash);
    }

    /**
     * @dev Returns hash of a message that can be signed by owners.
     * @param safe Safe to which the message is targeted.
     * @param message Message that should be hashed.
     * @return Message hash.
     */
    function getMessageHashForSafe(Safe safe, bytes memory message) public view returns (bytes32) {
        return keccak256(encodeMessageDataForSafe(safe, message));
    }

    /**
     * @notice Implementation of updated EIP-1271 signature validation method.
     * @param _dataHash Hash of the data signed on the behalf of address(msg.sender)
     * @param _signature Signature byte array associated with _dataHash
     * @return Updated EIP1271 magic value if signature is valid, otherwise 0x0
     */
    function isValidSignature(bytes32 _dataHash, bytes calldata _signature) external view returns (bytes4) {
        ISignatureValidator validator = ISignatureValidator(msg.sender);
        bytes4 value = validator.isValidSignature(abi.encode(_dataHash), _signature);
        return (value == EIP1271_MAGIC_VALUE) ? UPDATED_MAGIC_VALUE : bytes4(0);
    }

    /**
     * @dev Returns array of first 10 modules.
     * @return Array of modules.
     */
    function getModules() external view returns (address[] memory) {
        // Caller should be a Safe
        Safe safe = Safe(payable(msg.sender));
        (address[] memory array, ) = safe.getModulesPaginated(SENTINEL_MODULES, 10);
        return array;
    }

    /**
     * @dev Performs a delegatecall on a targetContract in the context of self.
     * Internally reverts execution to avoid side effects (making it static). Catches revert and returns encoded result as bytes.
     * @dev Inspired by https://github.com/gnosis/util-contracts/blob/bb5fe5fb5df6d8400998094fb1b32a178a47c3a1/contracts/StorageAccessible.sol
     * @param targetContract Address of the contract containing the code to execute.
     * @param calldataPayload Calldata that should be sent to the target contract (encoded method name and arguments).
     */
    function simulate(address targetContract, bytes calldata calldataPayload) external returns (bytes memory response) {
        /**
         * Suppress compiler warnings about not using parameters, while allowing
         * parameters to keep names for documentation purposes. This does not
         * generate code.
         */
        targetContract;
        calldataPayload;

        // solhint-disable-next-line no-inline-assembly
        assembly {
            let internalCalldata := mload(0x40)
            /**
             * Store `simulateAndRevert.selector`.
             * String representation is used to force right padding
             */
            mstore(internalCalldata, "\xb4\xfa\xba\x09")
            /**
             * Abuse the fact that both this and the internal methods have the
             * same signature, and differ only in symbol name (and therefore,
             * selector) and copy calldata directly. This saves us approximately
             * 250 bytes of code and 300 gas at runtime over the
             * `abi.encodeWithSelector` builtin.
             */
            calldatacopy(add(internalCalldata, 0x04), 0x04, sub(calldatasize(), 0x04))

            /**
             * `pop` is required here by the compiler, as top level expressions
             * can't have return values in inline assembly. `call` typically
             * returns a 0 or 1 value indicated whether or not it reverted, but
             * since we know it will always revert, we can safely ignore it.
             */
            pop(
                call(
                    gas(),
                    // address() has been changed to caller() to use the implementation of the Safe
                    caller(),
                    0,
                    internalCalldata,
                    calldatasize(),
                    /**
                     * The `simulateAndRevert` call always reverts, and
                     * instead encodes whether or not it was successful in the return
                     * data. The first 32-byte word of the return data contains the
                     * `success` value, so write it to memory address 0x00 (which is
                     * reserved Solidity scratch space and OK to use).
                     */
                    0x00,
                    0x20
                )
            )

            /**
             * Allocate and copy the response bytes, making sure to increment
             * the free memory pointer accordingly (in case this method is
             * called as an internal function). The remaining `returndata[0x20:]`
             * contains the ABI encoded response bytes, so we can just write it
             * as is to memory.
             */
            let responseSize := sub(returndatasize(), 0x20)
            response := mload(0x40)
            mstore(0x40, add(response, responseSize))
            returndatacopy(response, 0x20, responseSize)

            if iszero(mload(0x00)) {
                revert(add(response, 0x20), mload(response))
            }
        }
    }
}


CompatibilityFallbackHandler

Compatibility Fallback Handler - Provides compatibility between pre 1.3.0 and 1.3.0+ Safe contracts.

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/**
 * @title Handler Context - Allows the fallback handler to extract addition context from the calldata
 * @dev The fallback manager appends the following context to the calldata:
 *      1. Fallback manager caller address (non-padded)
 * based on https://github.com/OpenZeppelin/openzeppelin-contracts/blob/f8cc8b844a9f92f63dc55aa581f7d643a1bc5ac1/contracts/metatx/ERC2771Context.sol
 * @author Richard Meissner - @rmeissner
 */
abstract contract HandlerContext {
    /**
     * @notice Allows fetching the original caller address.
     * @dev This is only reliable in combination with a FallbackManager that supports this (e.g. Safe contract >=1.3.0).
     *      When using this functionality make sure that the linked _manager (aka msg.sender) supports this.
     *      This function does not rely on a trusted forwarder. Use the returned value only to
     *      check information against the calling manager.
     * @return sender Original caller address.
     */
    function _msgSender() internal pure returns (address sender) {
        // The assembly code is more direct than the Solidity version using `abi.decode`.
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sender := shr(96, calldataload(sub(calldatasize(), 20)))
        }
    }

    /**
     * @notice Returns the FallbackManager address
     * @return Fallback manager address
     */
    function _manager() internal view returns (address) {
        return msg.sender;
    }
}


HandlerContext

Handler Context - Allows the fallback handler to extract addition context from the calldata

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

import "../interfaces/ERC1155TokenReceiver.sol";
import "../interfaces/ERC721TokenReceiver.sol";
import "../interfaces/ERC777TokensRecipient.sol";
import "../interfaces/IERC165.sol";

/**
 * @title Default Callback Handler - Handles supported tokens' callbacks, allowing Safes receiving these tokens.
 * @author Richard Meissner - @rmeissner
 */
contract TokenCallbackHandler is ERC1155TokenReceiver, ERC777TokensRecipient, ERC721TokenReceiver, IERC165 {
    /**
     * @notice Handles ERC1155 Token callback.
     * return Standardized onERC1155Received return value.
     */
    function onERC1155Received(address, address, uint256, uint256, bytes calldata) external pure override returns (bytes4) {
        return 0xf23a6e61;
    }

    /**
     * @notice Handles ERC1155 Token batch callback.
     * return Standardized onERC1155BatchReceived return value.
     */
    function onERC1155BatchReceived(
        address,
        address,
        uint256[] calldata,
        uint256[] calldata,
        bytes calldata
    ) external pure override returns (bytes4) {
        return 0xbc197c81;
    }

    /**
     * @notice Handles ERC721 Token callback.
     *  return Standardized onERC721Received return value.
     */
    function onERC721Received(address, address, uint256, bytes calldata) external pure override returns (bytes4) {
        return 0x150b7a02;
    }

    /**
     * @notice Handles ERC777 Token callback.
     * return nothing (not standardized)
     */
    function tokensReceived(address, address, address, uint256, bytes calldata, bytes calldata) external pure override {
        // We implement this for completeness, doesn't really have any value
    }

    /**
     * @notice Implements ERC165 interface support for ERC1155TokenReceiver, ERC721TokenReceiver and IERC165.
     * @param interfaceId Id of the interface.
     * @return if the interface is supported.
     */
    function supportsInterface(bytes4 interfaceId) external view virtual override returns (bool) {
        return
            interfaceId == type(ERC1155TokenReceiver).interfaceId ||
            interfaceId == type(ERC721TokenReceiver).interfaceId ||
            interfaceId == type(IERC165).interfaceId;
    }
}


TokenCallbackHandler

Default Callback Handler - Handles supported tokens' callbacks, allowing Safes receiving these tokens.

_operator

_from

_ids

_values

_value

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

// Note: The ERC-165 identifier for this interface is 0x4e2312e0.
interface ERC1155TokenReceiver {
    /**
     * @notice Handle the receipt of a single ERC1155 token type.
     * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeTransferFrom` after the balance has been updated.
     *      This function MUST return `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))` (i.e. 0xf23a6e61) if it accepts the transfer.
     *      This function MUST revert if it rejects the transfer.
     *      Return of any other value than the prescribed keccak256 generated value MUST result in the transaction being reverted by the caller.
     * @param _operator  The address which initiated the transfer (i.e. msg.sender).
     * @param _from      The address which previously owned the token.
     * @param _id        The ID of the token being transferred.
     * @param _value     The amount of tokens being transferred.
     * @param _data      Additional data with no specified format.
     * @return           `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`.
     */
    function onERC1155Received(
        address _operator,
        address _from,
        uint256 _id,
        uint256 _value,
        bytes calldata _data
    ) external returns (bytes4);

    /**
     * @notice Handle the receipt of multiple ERC1155 token types.
     * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeBatchTransferFrom` after the balances have been updated.
     *      This function MUST return `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))` (i.e. 0xbc197c81) if it accepts the transfer(s).
     *      This function MUST revert if it rejects the transfer(s).
     *      Return of any other value than the prescribed keccak256 generated value MUST result in the transaction being reverted by the caller.
     * @param _operator  The address which initiated the batch transfer (i.e. msg.sender).
     * @param _from      The address which previously owned the token.
     * @param _ids       An array containing ids of each token being transferred (order and length must match _values array).
     * @param _values    An array containing amounts of each token being transferred (order and length must match _ids array).
     * @param _data      Additional data with no specified format.
     * @return           `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`.
     */
    function onERC1155BatchReceived(
        address _operator,
        address _from,
        uint256[] calldata _ids,
        uint256[] calldata _values,
        bytes calldata _data
    ) external returns (bytes4);
}


ERC1155TokenReceiver

_tokenId

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/// @dev Note: the ERC-165 identifier for this interface is 0x150b7a02.
interface ERC721TokenReceiver {
    /**
     * @notice Handle the receipt of an NFT
     * @dev The ERC721 smart contract calls this function on the recipient
     *  after a `transfer`. This function MAY throw to revert and reject the
     *  transfer. Return of other than the magic value MUST result in the
     *  transaction being reverted.
     *  Note: the contract address is always the message sender.
     * @param _operator The address which called `safeTransferFrom` function.
     * @param _from The address which previously owned the token.
     * @param _tokenId The NFT identifier which is being transferred.
     * @param _data Additional data with no specified format.
     * @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
     *  unless throwing
     */
    function onERC721Received(address _operator, address _from, uint256 _tokenId, bytes calldata _data) external returns (bytes4);
}


Collection of production code that is used in the Safe Ecosystem