ABridge

Overview

License: MIT

abstract contract ABridge is IBridge, Initializable

The Bridge module

The Bridge contract facilitates the permissioned transfer of assets and/or arbitrary messages between two (or more) EVM blockchains.

To utilize the Bridge effectively, instances of this contract must be deployed on both base and destination chains, accompanied by the setup of trusted back ends to act as signers. The back end signatures are checked only upon redemption.

Each asset type is mapped to a handler (ERC-20, Native, Message) contract. Handlers implement the specific dispatch/redeem logic.

During redeem, handlers may forward execution to the IBatcher contract for multi-step operations. The bridge never executes batches directly and does this via a designated batcher contract that can be overridden. Users are advised to construct tx batches in a way that they are not front-runnable. E.g., USDT approve should be reset first.

IMPORTANT: All signer addresses must differ in their first (most significant) 8 bits in order to pass bloom (uniqueness) filtering.

Structs info

ABridgeStorage

struct ABridgeStorage {
    string network;
    IBatcher batcher;
    EnumerableMap.UintToAddressMap handlers;
    EnumerableSet.AddressSet signers;
    uint256 signaturesThreshold;
    mapping(bytes32 => bool) usedNonce;
}

Functions info

dispatch (0x553fd9ba)

function dispatch(
    uint256 assetType_,
    bytes calldata dispatchDetails_
) external payable virtual

A function to dispatch assets or messages to another chain.

Parameters:

Name	Type	Description
assetType_	uint256	the asset type identifier linked to a handler.
dispatchDetails_	bytes	encoded handler-specific dispatch data.

redeem (0xcf3d88c1)

function redeem(
    uint256 assetType_,
    bytes calldata redeemDetails_,
    bytes calldata proof_
) external virtual

A function to redeem an incoming cross-chain operation.

Requires enough valid signer approvals to pass threshold checks.

Parameters:

Name	Type	Description
assetType_	uint256	the asset type identifier linked to a handler.
redeemDetails_	bytes	encoded handler-specific redeem data.
proof_	bytes	a proof of signer approvals authorizing the redemption.

getHandlers (0x3801a828)

function getHandlers()
    external
    view
    returns (uint256[] memory assetTypes_, address[] memory handlers_)

Returns the list of supported asset types and a list of their corresponding handlers

getNetwork (0x07e4b7e9)

function getNetwork() external view returns (string memory)

Returns the network name

getBatcher (0xb63b5a2b)

function getBatcher() external view returns (address)

Returns the address of the batcher used

getSigners (0x94cf795e)

function getSigners() external view returns (address[] memory)

Returns the list of current bridge signers

getSignaturesThreshold (0x4f2c65a5)

function getSignaturesThreshold() external view returns (uint256)

Returns the number of signatures for the redemption to be accepted

nonceUsed (0x61a4422b)

function nonceUsed(bytes32 nonce_) external view returns (bool)

Checks if the dispatch event exists in the contract

assetTypeSupported (0xefe39fc8)

function assetTypeSupported(uint256 assetType_) public view returns (bool)

Checks if the asset type is linked to the handler