FishnetWallet Contract API

Contract Overview

The FishnetWallet contract is a permit-gated smart wallet that executes on-chain actions authorized by EIP-712 signed permits. Source: contracts/src/FishnetWallet.sol License: MIT Solidity Version: ^0.8.19

State Variables

Public State

owner

address

Wallet owner. Can update signer, pause/unpause, and withdraw funds.

paused

bool

Pause status. When true, all execute() calls revert.

fishnetSigner

address

Address authorized to sign permits. Signatures are verified against this address.

usedNonces

mapping(uint256 => bool)

Tracks used nonces to prevent replay attacks. Each nonce can only be used once.

Immutable State

_CACHED_DOMAIN_SEPARATOR

bytes32

Cached EIP-712 domain separator for the original chain ID.

_CACHED_CHAIN_ID

uint256

Original chain ID at deployment. Used to detect forks.

Constants

FishnetWallet.sol:29-33

bytes32 internal constant PERMIT_TYPEHASH = keccak256(
    "FishnetPermit(address wallet,uint64 chainId,uint256 nonce,"
    "uint48 expiry,address target,uint256 value,"
    "bytes32 calldataHash,bytes32 policyHash)"
);

The permit typehash defines the EIP-712 structure. Note the use of uint64 chainId and uint48 expiry instead of uint256.

Structs

FishnetPermit

FishnetWallet.sol:35-44

struct FishnetPermit {
    address wallet;      // This wallet's address
    uint64  chainId;     // Target chain ID
    uint256 nonce;       // Unique nonce
    uint48  expiry;      // Expiration timestamp
    address target;      // Contract to call
    uint256 value;       // ETH to send
    bytes32 calldataHash;// keccak256 of calldata
    bytes32 policyHash;  // Policy identifier
}

wallet

address

required

Must match address(this). Prevents permit reuse across wallets.

chainId

uint64

required

Must match block.chainid. Prevents cross-chain replay attacks.

nonce

uint256

required

Unique identifier. Can be any unused value (not necessarily sequential).

expiry

uint48

required

UNIX timestamp. Permit reverts if block.timestamp > expiry.

target

address

required

The contract that will receive the call. Must match the target parameter in execute().

value

uint256

required

Amount of ETH to send. Must match the value parameter in execute().

calldataHash

bytes32

required

keccak256(data) where data is the calldata. Must match keccak256(data) in execute().

policyHash

bytes32

required

Identifier for the policy that approved this action. Emitted in events for audit trails.

Constructor

FishnetWallet.sol:62-69

constructor(address _fishnetSigner) {
    if (_fishnetSigner == address(0)) revert ZeroAddress();
    owner = msg.sender;
    fishnetSigner = _fishnetSigner;

    _CACHED_CHAIN_ID = block.chainid;
    _CACHED_DOMAIN_SEPARATOR = _computeDomainSeparator();
}

_fishnetSigner

address

required

Address of the backend signer. Reverts if address(0).

Effects:

Sets msg.sender as owner
Caches the domain separator for the deployment chain

Core Functions

execute

FishnetWallet.sol:90-112

function execute(
    address target,
    uint256 value,
    bytes calldata data,
    FishnetPermit calldata permit,
    bytes calldata signature
) external whenNotPaused

Executes an on-chain action if a valid permit and signature are provided.

target

address

required

Contract to call. Must match permit.target.

value

uint256

required

ETH to send (in wei). Must match permit.value.

data

bytes

required

Calldata to pass to target. keccak256(data) must match permit.calldataHash.

permit

FishnetPermit

required

The signed permit structure.

signature

bytes

required

65-byte ECDSA signature in r || s || v format.

Validation Checks (in order):

block.timestamp <= permit.expiry → reverts PermitExpired()
permit.chainId == block.chainid → reverts WrongChain()
!usedNonces[permit.nonce] → reverts NonceUsed()
permit.target == target → reverts TargetMismatch()
permit.value == value → reverts ValueMismatch()
permit.calldataHash == keccak256(data) → reverts CalldataMismatch()
permit.wallet == address(this) → reverts WalletMismatch()
_verifySignature(permit, signature) → reverts InvalidSignature()

Effects:

Marks nonce as used: usedNonces[permit.nonce] = true
Calls target.call{value: value}(data)
Emits ActionExecuted(target, value, permit.nonce, permit.policyHash)

Reverts:

WalletPaused() if paused
ExecutionFailed() if the target call fails

Example:

// Swap 1 ETH for USDC on Uniswap
bytes memory swapData = abi.encodeWithSelector(
    ISwapRouter.exactInputSingle.selector,
    SwapParams({
        tokenIn: WETH,
        tokenOut: USDC,
        fee: 3000,
        recipient: address(wallet),
        deadline: block.timestamp + 300,
        amountIn: 1 ether,
        amountOutMinimum: 2000e6,
        sqrtPriceLimitX96: 0
    })
);

FishnetPermit memory permit = FishnetPermit({
    wallet: address(wallet),
    chainId: uint64(block.chainid),
    nonce: 42,
    expiry: uint48(block.timestamp + 600),
    target: UNISWAP_ROUTER,
    value: 0,
    calldataHash: keccak256(swapData),
    policyHash: keccak256("swap-policy-v1")
});

bytes memory signature = /* get from Fishnet backend */;

wallet.execute(UNISWAP_ROUTER, 0, swapData, permit, signature);

setSigner

FishnetWallet.sol:152-157

function setSigner(address _signer) external onlyOwner {
    if (_signer == address(0)) revert ZeroAddress();
    address oldSigner = fishnetSigner;
    fishnetSigner = _signer;
    emit SignerUpdated(oldSigner, _signer);
}

Updates the authorized signer address.

_signer

address

required

New signer address. Reverts if address(0).

Restrictions: Only callable by owner. Effects: Emits SignerUpdated(oldSigner, newSigner).

withdraw

FishnetWallet.sol:159-164

function withdraw(address to) external onlyOwner {
    uint256 balance = address(this).balance;
    (bool success, ) = to.call{value: balance}("");
    if (!success) revert WithdrawFailed();
    emit Withdrawn(to, balance);
}

Withdraws all ETH from the wallet.

address

required

Recipient address.

Restrictions: Only callable by owner. Effects: Transfers entire balance and emits Withdrawn(to, amount).

pause

FishnetWallet.sol:166-169

function pause() external onlyOwner {
    paused = true;
    emit Paused(msg.sender);
}

Pauses all execute() calls. Restrictions: Only callable by owner. Effects: Sets paused = true and emits Paused(account).

unpause

FishnetWallet.sol:171-174

function unpause() external onlyOwner {
    paused = false;
    emit Unpaused(msg.sender);
}

Resumes execution after a pause. Restrictions: Only callable by owner. Effects: Sets paused = false and emits Unpaused(account).

View Functions

DOMAIN_SEPARATOR

FishnetWallet.sol:71-76

function DOMAIN_SEPARATOR() public view returns (bytes32) {
    if (block.chainid == _CACHED_CHAIN_ID) {
        return _CACHED_DOMAIN_SEPARATOR;
    }
    return _computeDomainSeparator();
}

Returns the EIP-712 domain separator. Recomputes if chain ID has changed (e.g., after a fork). Returns: bytes32 domain separator.

Events

ActionExecuted

FishnetWallet.sol:46

event ActionExecuted(address indexed target, uint256 value, uint256 nonce, bytes32 policyHash);

Emitted when a permit is successfully executed.

target

address

The contract that was called.

value

uint256

Amount of ETH sent.

nonce

uint256

Nonce of the executed permit.

policyHash

bytes32

Policy that authorized this action.

SignerUpdated

FishnetWallet.sol:47

event SignerUpdated(address indexed oldSigner, address indexed newSigner);

Emitted when the signer address is changed.

Paused / Unpaused

FishnetWallet.sol:48-49

event Paused(address account);
event Unpaused(address account);

Emitted when the wallet is paused or unpaused.

Withdrawn

FishnetWallet.sol:50

event Withdrawn(address indexed to, uint256 amount);

Emitted when ETH is withdrawn.

Custom Errors

FishnetWallet.sol:5-18

error PermitExpired();         // block.timestamp > permit.expiry
error WrongChain();            // permit.chainId != block.chainid
error NonceUsed();             // Nonce already consumed
error TargetMismatch();        // permit.target != target
error ValueMismatch();         // permit.value != value
error CalldataMismatch();      // permit.calldataHash != keccak256(data)
error WalletMismatch();        // permit.wallet != address(this)
error InvalidSignature();      // ecrecover didn't return fishnetSigner
error InvalidSignatureLength();// signature.length != 65
error ExecutionFailed();       // Target call reverted
error NotOwner();              // msg.sender != owner
error WalletPaused();          // paused == true
error ZeroAddress();           // Attempted to set address(0)
error WithdrawFailed();        // ETH transfer failed

All errors are custom errors (gas-efficient, descriptive).

Security Considerations

Nonce Management: Nonces do NOT need to be sequential. The backend should generate random nonces to prevent front-running attacks.

Expiry Bounds: expiry is uint48 (max value: 281474976710655, ~year 8921). Rust signer validates this range.

Signature Malleability: The contract does NOT check for signature malleability (high-s values). This is acceptable because each nonce can only be used once.

Reentrancy: The contract marks nonces as used BEFORE making external calls, providing reentrancy protection.

Receive Function

FishnetWallet.sol:176

receive() external payable {}

The wallet can receive ETH directly.

Overview

Development

FishnetWallet Contract API

Contract Overview

State Variables

Public State

Immutable State

Constants

Structs

FishnetPermit

Constructor

Core Functions

execute

setSigner

withdraw

pause

unpause

View Functions

DOMAIN_SEPARATOR

Events

ActionExecuted

SignerUpdated

Paused / Unpaused

Withdrawn

Custom Errors

Security Considerations

Receive Function

Build docs developers (and LLMs) love

Overview

Development

​Contract Overview

​State Variables

​Public State

​Immutable State

​Constants

​Structs

​FishnetPermit

​Constructor

​Core Functions

​execute

​setSigner

​withdraw

​pause

​unpause

​View Functions

​DOMAIN_SEPARATOR

​Events

​ActionExecuted

​SignerUpdated

​Paused / Unpaused

​Withdrawn

​Custom Errors

​Security Considerations

​Receive Function

Build docs developers (and LLMs) love

Contract Overview

State Variables

Public State

Immutable State

Constants

Structs

FishnetPermit

Constructor

Core Functions

execute

setSigner

withdraw

pause

unpause

View Functions

DOMAIN_SEPARATOR

Events

ActionExecuted

SignerUpdated

Paused / Unpaused

Withdrawn

Custom Errors

Security Considerations

Receive Function