authModule_

InvalidAuthModule

InvalidChainId

InvalidCommands

InvalidOwner

NotOwner

NotSelf

sender

destinationChain

destinationContractAddress

payloadHash

payload

ContractCall

commandId

sourceChain

sourceAddress

contractAddress

sourceTxHash

sourceEventIndex

ContractCallApproved

Executed

newOperatorsData

OperatorshipTransferred

previousOwner

newOwner

OwnershipTransferred

params

approveContractCall

authModule

callContract

input

execute

getBool

isCommandExecuted

isContractCallApproved

owner

owner_

transferOperatorship

transferOwnership

validateContractCall

valid

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

import { IAxelarGateway } from './interfaces/IAxelarGateway.sol';
import { IAxelarAuth } from './interfaces/IAxelarAuth.sol';

import { ECDSA } from './auth/ECDSA.sol';
import { EternalStorage } from './util/EternalStorage.sol';
import { Ownable } from './util/Ownable.sol';

contract AxelarGateway is EternalStorage, Ownable, IAxelarGateway {
    bytes32 internal constant PREFIX_COMMAND_EXECUTED = keccak256('command-executed');
    bytes32 internal constant PREFIX_CONTRACT_CALL_APPROVED = keccak256('contract-call-approved');

    bytes32 internal constant SELECTOR_APPROVE_CONTRACT_CALL = keccak256('approveContractCall');
    bytes32 internal constant SELECTOR_TRANSFER_OPERATORSHIP = keccak256('transferOperatorship');

    // solhint-disable-next-line var-name-mixedcase
    IAxelarAuth internal immutable AUTH_MODULE;

    constructor(address authModule_) {
        if (authModule_.code.length == 0) revert InvalidAuthModule();

        AUTH_MODULE = IAxelarAuth(authModule_);
    }

    modifier onlySelf() {
        if (msg.sender != address(this)) revert NotSelf();

        _;
    }

    /******************\
    |* Public Methods *|
    \******************/

    function callContract(string calldata destinationChain, string calldata destinationContractAddress, bytes calldata payload) external {
        emit ContractCall(msg.sender, destinationChain, destinationContractAddress, keccak256(payload), payload);
    }

    function isContractCallApproved(
        bytes32 commandId,
        string calldata sourceChain,
        string calldata sourceAddress,
        address contractAddress,
        bytes32 payloadHash
    ) external view override returns (bool) {
        return getBool(_getIsContractCallApprovedKey(commandId, sourceChain, sourceAddress, contractAddress, payloadHash));
    }

    function validateContractCall(
        bytes32 commandId,
        string calldata sourceChain,
        string calldata sourceAddress,
        bytes32 payloadHash
    ) external override returns (bool valid) {
        bytes32 key = _getIsContractCallApprovedKey(commandId, sourceChain, sourceAddress, msg.sender, payloadHash);
        valid = getBool(key);
        if (valid) _setBool(key, false);
    }

    /***********\
    |* Getters *|
    \***********/

    function authModule() public view returns (address) {
        return address(AUTH_MODULE);
    }

    function isCommandExecuted(bytes32 commandId) public view override returns (bool) {
        return getBool(_getIsCommandExecutedKey(commandId));
    }

    /**********************\
    |* External Functions *|
    \**********************/

    function execute(bytes calldata input) external override {
        (bytes memory data, bytes memory proof) = abi.decode(input, (bytes, bytes));

        bytes32 messageHash = ECDSA.toEthSignedMessageHash(keccak256(data));

        // returns true for current operators
        bool allowOperatorshipTransfer = AUTH_MODULE.validateProof(messageHash, proof);

        uint256 chainId;
        bytes32[] memory commandIds;
        string[] memory commands;
        bytes[] memory params;

        (chainId, commandIds, commands, params) = abi.decode(data, (uint256, bytes32[], string[], bytes[]));

        if (chainId != block.chainid) revert InvalidChainId();

        uint256 commandsLength = commandIds.length;

        if (commandsLength != commands.length || commandsLength != params.length) revert InvalidCommands();

        for (uint256 i; i < commandsLength; ++i) {
            bytes32 commandId = commandIds[i];

            if (isCommandExecuted(commandId)) continue; /* Ignore if duplicate commandId received */

            bytes4 commandSelector;
            bytes32 commandHash = keccak256(abi.encodePacked(commands[i]));

            if (commandHash == SELECTOR_APPROVE_CONTRACT_CALL) {
                commandSelector = AxelarGateway.approveContractCall.selector;
            } else if (commandHash == SELECTOR_TRANSFER_OPERATORSHIP) {
                if (!allowOperatorshipTransfer) continue;

                allowOperatorshipTransfer = false;
                commandSelector = AxelarGateway.transferOperatorship.selector;
            } else {
                continue; /* Ignore if unknown command received */
            }

            // Prevent a re-entrancy from executing this command before it can be marked as successful.
            _setCommandExecuted(commandId, true);
            // solhint-disable-next-line avoid-low-level-calls
            (bool success, ) = address(this).call(abi.encodeWithSelector(commandSelector, params[i], commandId));

            if (success) emit Executed(commandId);
            else _setCommandExecuted(commandId, false);
        }
    }

    /******************\
    |* Self Functions *|
    \******************/

    function approveContractCall(bytes calldata params, bytes32 commandId) external onlySelf {
        (
            string memory sourceChain,
            string memory sourceAddress,
            address contractAddress,
            bytes32 payloadHash,
            bytes32 sourceTxHash,
            uint256 sourceEventIndex
        ) = abi.decode(params, (string, string, address, bytes32, bytes32, uint256));

        _setContractCallApproved(commandId, sourceChain, sourceAddress, contractAddress, payloadHash);
        emit ContractCallApproved(commandId, sourceChain, sourceAddress, contractAddress, payloadHash, sourceTxHash, sourceEventIndex);
    }

    function transferOperatorship(bytes calldata newOperatorsData, bytes32) external onlySelf {
        AUTH_MODULE.transferOperatorship(newOperatorsData);

        emit OperatorshipTransferred(newOperatorsData);
    }

    /********************\
    |* Pure Key Getters *|
    \********************/

    function _getIsCommandExecutedKey(bytes32 commandId) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked(PREFIX_COMMAND_EXECUTED, commandId));
    }

    function _getIsContractCallApprovedKey(
        bytes32 commandId,
        string memory sourceChain,
        string memory sourceAddress,
        address contractAddress,
        bytes32 payloadHash
    ) internal pure returns (bytes32) {
        return keccak256(abi.encode(PREFIX_CONTRACT_CALL_APPROVED, commandId, sourceChain, sourceAddress, contractAddress, payloadHash));
    }

    /********************\
    |* Internal Setters *|
    \********************/

    function _setCommandExecuted(bytes32 commandId, bool executed) internal {
        _setBool(_getIsCommandExecutedKey(commandId), executed);
    }

    function _setContractCallApproved(
        bytes32 commandId,
        string memory sourceChain,
        string memory sourceAddress,
        address contractAddress,
        bytes32 payloadHash
    ) internal {
        _setBool(_getIsContractCallApprovedKey(commandId, sourceChain, sourceAddress, contractAddress, payloadHash), true);
    }
}


AxelarGateway

recentOperators

DuplicateOperators

InvalidOperators

InvalidS

InvalidSignature

InvalidSignatureLength

InvalidThreshold

InvalidV

InvalidWeights

LowSignaturesWeight

MalformedSigners

newOperators

newWeights

newThreshold

currentEpoch

epochForHash

hashForEpoch

messageHash

proof

validateProof

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

import { IAxelarAuthWeighted } from '../interfaces/IAxelarAuthWeighted.sol';
import { ECDSA } from './ECDSA.sol';
import { Ownable } from '../util/Ownable.sol';

contract AxelarAuthWeighted is Ownable, IAxelarAuthWeighted {
    uint256 public currentEpoch;
    mapping(uint256 => bytes32) public hashForEpoch;
    mapping(bytes32 => uint256) public epochForHash;

    // @dev Number of recent operator sets to be tracked.
    // solhint-disable-next-line var-name-mixedcase
    uint256 internal constant OLD_KEY_RETENTION = 16;

    constructor(bytes[] memory recentOperators) {
        uint256 length = recentOperators.length;

        for (uint256 i; i < length; ++i) {
            _transferOperatorship(recentOperators[i]);
        }
    }

    /**************************\
    |* External Functionality *|
    \**************************/

    /// @dev This function takes messageHash and proof data and reverts if proof is invalid
    /// @return True if provided operators are the current ones
    function validateProof(bytes32 messageHash, bytes calldata proof) external view returns (bool) {
        (address[] memory operators, uint256[] memory weights, uint256 threshold, bytes[] memory signatures) = abi.decode(
            proof,
            (address[], uint256[], uint256, bytes[])
        );

        bytes32 operatorsHash = keccak256(abi.encode(operators, weights, threshold));
        uint256 operatorsEpoch = epochForHash[operatorsHash];
        uint256 epoch = currentEpoch;

        if (operatorsEpoch == 0 || epoch - operatorsEpoch >= OLD_KEY_RETENTION) revert InvalidOperators();

        _validateSignatures(messageHash, operators, weights, threshold, signatures);

        return operatorsEpoch == epoch;
    }

    /***********************\
    |* Owner Functionality *|
    \***********************/

    function transferOperatorship(bytes calldata params) external onlyOwner {
        _transferOperatorship(params);
    }

    /**************************\
    |* Internal Functionality *|
    \**************************/

    function _transferOperatorship(bytes memory params) internal {
        (address[] memory newOperators, uint256[] memory newWeights, uint256 newThreshold) = abi.decode(
            params,
            (address[], uint256[], uint256)
        );
        uint256 operatorsLength = newOperators.length;
        uint256 weightsLength = newWeights.length;

        // operators must be sorted binary or alphabetically in lower case
        if (operatorsLength == 0 || !_isSortedAscAndContainsNoDuplicate(newOperators)) revert InvalidOperators();

        if (weightsLength != operatorsLength) revert InvalidWeights();

        uint256 totalWeight;
        for (uint256 i; i < weightsLength; ++i) {
            totalWeight = totalWeight + newWeights[i];
        }
        if (newThreshold == 0 || totalWeight < newThreshold) revert InvalidThreshold();

        bytes32 newOperatorsHash = keccak256(params);

        if (epochForHash[newOperatorsHash] != 0) revert DuplicateOperators();

        uint256 epoch = currentEpoch + 1;
        currentEpoch = epoch;
        hashForEpoch[epoch] = newOperatorsHash;
        epochForHash[newOperatorsHash] = epoch;

        emit OperatorshipTransferred(newOperators, newWeights, newThreshold);
    }

    function _validateSignatures(
        bytes32 messageHash,
        address[] memory operators,
        uint256[] memory weights,
        uint256 threshold,
        bytes[] memory signatures
    ) internal pure {
        uint256 operatorsLength = operators.length;
        uint256 signaturesLength = signatures.length;
        uint256 operatorIndex;
        uint256 weight;
        // looking for signers within operators
        // assuming that both operators and signatures are sorted
        for (uint256 i; i < signaturesLength; ++i) {
            address signer = ECDSA.recover(messageHash, signatures[i]);
            // looping through remaining operators to find a match
            for (; operatorIndex < operatorsLength && signer != operators[operatorIndex]; ++operatorIndex) {}
            // checking if we are out of operators
            if (operatorIndex == operatorsLength) revert MalformedSigners();
            // accumulating signatures weight
            weight = weight + weights[operatorIndex];
            // weight needs to reach or surpass threshold
            if (weight >= threshold) return;
            // increasing operators index if match was found
            ++operatorIndex;
        }
        // if weight sum below threshold
        revert LowSignaturesWeight();
    }

    function _isSortedAscAndContainsNoDuplicate(address[] memory accounts) internal pure returns (bool) {
        uint256 accountsLength = accounts.length;
        address prevAccount = accounts[0];

        if (prevAccount == address(0)) return false;

        for (uint256 i = 1; i < accountsLength; ++i) {
            address currAccount = accounts[i];

            if (prevAccount >= currAccount) {
                return false;
            }

            prevAccount = currAccount;
        }

        return true;
    }
}


AxelarAuthWeighted

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    error InvalidSignatureLength();
    error InvalidS();
    error InvalidV();
    error InvalidSignature();

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address signer) {
        // Check the signature length
        if (signature.length != 65) revert InvalidSignatureLength();

        // Divide the signature in r, s and v variables
        bytes32 r;
        bytes32 s;
        uint8 v;

        // ecrecover takes the signature parameters, and the only way to get them
        // currently is to use assembly.
        // solhint-disable-next-line no-inline-assembly
        assembly {
            r := mload(add(signature, 0x20))
            s := mload(add(signature, 0x40))
            v := byte(0, mload(add(signature, 0x60)))
        }

        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) revert InvalidS();

        if (v != 27 && v != 28) revert InvalidV();

        // If the signature is valid (and not malleable), return the signer address
        if ((signer = ecrecover(hash, v, r, s)) == address(0)) revert InvalidSignature();
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * replicates the behavior of the
     * https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign[`eth_sign`]
     * JSON-RPC method.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked('\x19Ethereum Signed Message:\n32', hash));
    }
}


ECDSA

gateway_

InvalidAddress

NotApprovedByGateway

gateway

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import { IAxelarGateway } from '../interfaces/IAxelarGateway.sol';
import { IAxelarExecutable } from '../interfaces/IAxelarExecutable.sol';

contract AxelarExecutable is IAxelarExecutable {
    IAxelarGateway public immutable gateway;

    constructor(address gateway_) {
        if (gateway_ == address(0)) revert InvalidAddress();

        gateway = IAxelarGateway(gateway_);
    }

    /// @dev Execute an interchain contract call after validating that an approval for it is recorded at the gateway
    function execute(bytes32 commandId, string calldata sourceChain, string calldata sourceAddress, bytes calldata payload) external {
        bytes32 payloadHash = keccak256(payload);

        if (!gateway.validateContractCall(commandId, sourceChain, sourceAddress, payloadHash)) revert NotApprovedByGateway();

        _execute(sourceChain, sourceAddress, payload);
    }

    /// @dev To be overidden by the app
    function _execute(string calldata sourceChain, string calldata sourceAddress, bytes calldata payload) internal virtual {}
}


AxelarExecutable

currentOperators

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

import { IOwnable } from './IOwnable.sol';

interface IAxelarAuth is IOwnable {
    function validateProof(bytes32 messageHash, bytes calldata proof) external returns (bool currentOperators);

    function transferOperatorship(bytes calldata params) external;
}


IAxelarAuth

hash

epoch

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

import { IAxelarAuth } from './IAxelarAuth.sol';

interface IAxelarAuthWeighted is IAxelarAuth {
    error InvalidOperators();
    error InvalidThreshold();
    error DuplicateOperators();
    error MalformedSigners();
    error LowSignaturesWeight();
    error InvalidWeights();

    event OperatorshipTransferred(address[] newOperators, uint256[] newWeights, uint256 newThreshold);

    function currentEpoch() external view returns (uint256);

    function hashForEpoch(uint256 epoch) external view returns (bytes32);

    function epochForHash(bytes32 hash) external view returns (uint256);
}


IAxelarAuthWeighted

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import { IAxelarGateway } from './IAxelarGateway.sol';

interface IAxelarExecutable {
    error InvalidAddress();
    error NotApprovedByGateway();

    function gateway() external view returns (IAxelarGateway);

    function execute(bytes32 commandId, string calldata sourceChain, string calldata sourceAddress, bytes calldata payload) external;
}


IAxelarExecutable

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

interface IAxelarGateway {
    /**********\
    |* Errors *|
    \**********/

    error NotSelf();
    error InvalidAuthModule();
    error InvalidChainId();
    error InvalidCommands();

    /**********\
    |* Events *|
    \**********/

    event ContractCall(
        address indexed sender,
        string destinationChain,
        string destinationContractAddress,
        bytes32 indexed payloadHash,
        bytes payload
    );

    event Executed(bytes32 indexed commandId);

    event ContractCallApproved(
        bytes32 indexed commandId,
        string sourceChain,
        string sourceAddress,
        address indexed contractAddress,
        bytes32 indexed payloadHash,
        bytes32 sourceTxHash,
        uint256 sourceEventIndex
    );

    event OperatorshipTransferred(bytes newOperatorsData);

    /********************\
    |* Public Functions *|
    \********************/

    function callContract(string calldata destinationChain, string calldata contractAddress, bytes calldata payload) external;

    function isContractCallApproved(
        bytes32 commandId,
        string calldata sourceChain,
        string calldata sourceAddress,
        address contractAddress,
        bytes32 payloadHash
    ) external view returns (bool);

    function validateContractCall(
        bytes32 commandId,
        string calldata sourceChain,
        string calldata sourceAddress,
        bytes32 payloadHash
    ) external returns (bool);

    /***********\
    |* Getters *|
    \***********/

    function authModule() external view returns (address);

    function isCommandExecuted(bytes32 commandId) external view returns (bool);

    /**********************\
    |* External Functions *|
    \**********************/

    function execute(bytes calldata input) external;
}


IAxelarGateway

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IOwnable {
    error NotOwner();
    error InvalidOwner();

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function owner() external view returns (address);

    function transferOwnership(address newOwner) external;
}


IOwnable

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.9;

/**
 * @title EternalStorage
 * @dev This contract holds all the necessary state variables to carry out the storage of any contract.
 */
contract EternalStorage {
    mapping(bytes32 => bool) private _boolStorage;

    // *** Getter Methods ***
    function getBool(bytes32 key) public view returns (bool) {
        return _boolStorage[key];
    }

    // *** Setter Methods ***
    function _setBool(bytes32 key, bool value) internal {
        _boolStorage[key] = value;
    }

    // *** Delete Methods ***
    function _deleteBool(bytes32 key) internal {
        delete _boolStorage[key];
    }
}


EternalStorage

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import { IOwnable } from '../interfaces/IOwnable.sol';

abstract contract Ownable is IOwnable {
    // keccak256('owner')
    bytes32 internal constant _OWNER_SLOT = 0x02016836a56b71f0d02689e69e326f4f4c1b9057164ef592671cf0d37c8040c0;

    constructor() {
        address newOwner = msg.sender;

        emit OwnershipTransferred(address(0), newOwner);

        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(_OWNER_SLOT, newOwner)
        }
    }

    modifier onlyOwner() {
        if (owner() != msg.sender) revert NotOwner();

        _;
    }

    function owner() public view returns (address owner_) {
        // solhint-disable-next-line no-inline-assembly
        assembly {
            owner_ := sload(_OWNER_SLOT)
        }
    }

    function transferOwnership(address newOwner) external virtual onlyOwner {
        emit OwnershipTransferred(owner(), newOwner);

        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(_OWNER_SLOT, newOwner)
        }
    }
}


Ownable

Axelar delivers secure cross-chain communication for Web3. Our infrastructure enables dApp users to interact with any asset or application, on any chain, with one click.

Axelar delivers secure cross-chain communication for Web3. Our infrastructure enables dApp users to interact with any asset or application, on any chain, with one click.

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Get Cookin'

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Cross-Chain Gateway Protocol Specifications