poanetwork
/
parity-bridge-research
mirror of https://github.com/poanetwork/parity-bridge-research.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Optimized deposit and withdraw_confirm operations of ForeignBridge contract

This commit is contained in:
Alexander Kolotov 2018-01-22 01:08:59 +03:00
parent 20acfe0c04
commit ee3b9fe746
1 changed files with 430 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

430
bridge.orig/contracts/bridge_foreign_optimized.sol Normal file
View File

@ -0,0 +1,430 @@
pragma solidity ^0.4.17;
/// general helpers.
/// `internal` so they get compiled into contracts using them.
library Helpers {
/// returns whether `array` contains `value`.
function addressArrayContains(address[] array, address value) internal pure returns (bool) {
for (uint i = 0; i < array.length; i++) {
if (array[i] == value) {
return true;
}
}
return false;
}
// returns the digits of `inputValue` as a string.
// example: `uintToString(12345678)` returns `"12345678"`
function uintToString(uint inputValue) internal pure returns (string) {
// figure out the length of the resulting string
uint length = 0;
uint currentValue = inputValue;
do {
length++;
currentValue /= 10;
} while (currentValue != 0);
// allocate enough memory
bytes memory result = new bytes(length);
// construct the string backwards
uint i = length - 1;
currentValue = inputValue;
do {
result[i--] = byte(48 + currentValue % 10);
currentValue /= 10;
} while (currentValue != 0);
return string(result);
}
}
/// Library used only to test Helpers library via rpc calls
library HelpersTest {
function addressArrayContains(address[] array, address value) public pure returns (bool) {
return Helpers.addressArrayContains(array, value);
}
function uintToString(uint256 inputValue) public pure returns (string str) {
return Helpers.uintToString(inputValue);
}
}
// helpers for message signing.
// `internal` so they get compiled into contracts using them.
library MessageSigning {
function recoverAddressFromSignedMessage(bytes signature, bytes message) internal pure returns (address) {
require(signature.length == 65);
bytes32 r;
bytes32 s;
bytes1 v;
// solium-disable-next-line security/no-inline-assembly
assembly {
r := mload(add(signature, 0x20))
s := mload(add(signature, 0x40))
v := mload(add(signature, 0x60))
}
return ecrecover(hashMessage(message), uint8(v), r, s);
}
function hashMessage(bytes message) internal pure returns (bytes32) {
bytes memory prefix = "\x19Ethereum Signed Message:\n";
return keccak256(prefix, Helpers.uintToString(message.length), message);
}
}
/// Library used only to test MessageSigning library via rpc calls
library MessageSigningTest {
function recoverAddressFromSignedMessage(bytes signature, bytes message) public pure returns (address) {
return MessageSigning.recoverAddressFromSignedMessage(signature, message);
}
}
library Message {
// layout of message :: bytes:
// offset 0: 32 bytes :: uint (little endian) - message length
// offset 32: 20 bytes :: address - recipient address
// offset 52: 32 bytes :: uint (little endian) - value
// offset 84: 32 bytes :: bytes32 - transaction hash
// bytes 1 to 32 are 0 because message length is stored as little endian.
// mload always reads 32 bytes.
// so we can and have to start reading recipient at offset 20 instead of 32.
// if we were to read at 32 the address would contain part of value and be corrupted.
// when reading from offset 20 mload will read 12 zero bytes followed
// by the 20 recipient address bytes and correctly convert it into an address.
// this saves some storage/gas over the alternative solution
// which is padding address to 32 bytes and reading recipient at offset 32.
// for more details see discussion in:
// https://github.com/paritytech/parity-bridge/issues/61
function getRecipient(bytes message) internal pure returns (address) {
address recipient;
// solium-disable-next-line security/no-inline-assembly
assembly {
recipient := mload(add(message, 20))
}
return recipient;
}
function getValue(bytes message) internal pure returns (uint) {
uint value;
// solium-disable-next-line security/no-inline-assembly
assembly {
value := mload(add(message, 52))
}
return value;
}
function getTransactionHash(bytes message) internal pure returns (bytes32) {
bytes32 hash;
// solium-disable-next-line security/no-inline-assembly
assembly {
hash := mload(add(message, 84))
}
return hash;
}
}
/// Library used only to test Message library via rpc calls
library MessageTest {
function getRecipient(bytes message) public pure returns (address) {
return Message.getRecipient(message);
}
function getValue(bytes message) public pure returns (uint) {
return Message.getValue(message);
}
function getTransactionHash(bytes message) public pure returns (bytes32) {
return Message.getTransactionHash(message);
}
}
contract HomeBridge {
/// Number of authorities signatures required to withdraw the money.
///
/// Must be lesser than number of authorities.
uint public requiredSignatures;
/// The gas cost of calling `HomeBridge.withdraw`.
///
/// Is subtracted from `value` on withdraw.
/// recipient pays the relaying authority for withdraw.
/// this shuts down attacks that exhaust authorities funds on home chain.
uint public estimatedGasCostOfWithdraw;
/// Contract authorities.
address[] public authorities;
/// Used foreign transaction hashes.
mapping (bytes32 => bool) withdraws;
/// Event created on money deposit.
event Deposit (address recipient, uint value);
/// Event created on money withdraw.
event Withdraw (address recipient, uint value);
/// Multisig authority validation
modifier allAuthorities(uint8[] v, bytes32[] r, bytes32[] s, bytes message) {
var hash = MessageSigning.hashMessage(message);
var used = new address[](requiredSignatures);
require(requiredSignatures <= v.length);
for (uint i = 0; i < requiredSignatures; i++) {
var a = ecrecover(hash, v[i], r[i], s[i]);
require(Helpers.addressArrayContains(authorities, a));
require(!Helpers.addressArrayContains(used, a));
used[i] = a;
}
_;
}
/// Constructor.
function HomeBridge(
uint requiredSignaturesParam,
address[] authoritiesParam,
uint estimatedGasCostOfWithdrawParam
) public
{
require(requiredSignaturesParam != 0);
require(requiredSignaturesParam <= authoritiesParam.length);
requiredSignatures = requiredSignaturesParam;
authorities = authoritiesParam;
estimatedGasCostOfWithdraw = estimatedGasCostOfWithdrawParam;
}
/// Should be used to deposit money.
function () public payable {
Deposit(msg.sender, msg.value);
}
/// to be called by authorities to check
/// whether they withdraw message should be relayed or whether it
/// is too low to cover the cost of calling withdraw and can be ignored
function isMessageValueSufficientToCoverRelay(bytes message) public view returns (bool) {
return Message.getValue(message) > getWithdrawRelayCost();
}
/// an upper bound to the cost of relaying a withdraw by calling HomeBridge.withdraw
function getWithdrawRelayCost() public view returns (uint) {
return estimatedGasCostOfWithdraw * tx.gasprice;
}
/// Used to withdraw money from the contract.
///
/// message contains:
/// withdrawal recipient (bytes20)
/// withdrawal value (uint)
/// foreign transaction hash (bytes32) // to avoid transaction duplication
///
/// NOTE that anyone can call withdraw provided they have the message and required signatures!
function withdraw(uint8[] v, bytes32[] r, bytes32[] s, bytes message) public allAuthorities(v, r, s, message) {
require(message.length == 84);
address recipient = Message.getRecipient(message);
uint value = Message.getValue(message);
bytes32 hash = Message.getTransactionHash(message);
// The following two statements guard against reentry into this function.
// Duplicated withdraw or reentry.
require(!withdraws[hash]);
// Order of operations below is critical to avoid TheDAO-like re-entry bug
withdraws[hash] = true;
// this fails if `value` is not even enough to cover the relay cost.
// Authorities simply IGNORE withdraws where `value` can’t relay cost.
// Think of it as `value` getting burned entirely on the relay with no value left to pay out the recipient.
require(isMessageValueSufficientToCoverRelay(message));
uint estimatedWeiCostOfWithdraw = getWithdrawRelayCost();
// charge recipient for relay cost
uint valueRemainingAfterSubtractingCost = value - estimatedWeiCostOfWithdraw;
// pay out recipient
recipient.transfer(valueRemainingAfterSubtractingCost);
// refund relay cost to relaying authority
msg.sender.transfer(estimatedWeiCostOfWithdraw);
Withdraw(recipient, valueRemainingAfterSubtractingCost);
}
}
contract ForeignBridge {
/// Number of authorities signatures required to withdraw the money.
///
/// Must be lesser than number of authorities.
uint public requiredSignatures;
/// Contract authorities.
mapping (address => bool) authorities;
/// Pending mesages
mapping (bytes32 => bytes) messages;
/// ???
mapping (bytes32 => bytes) signatures;
/// Pending deposits and authorities who confirmed them
mapping (bytes32 => bool) messages_signed;
mapping (bytes32 => uint) num_messages_signed;
/// Ether balances
mapping (address => uint) public balances;
/// Pending deposits and authorities who confirmed them
mapping (bytes32 => bool) deposits_signed;
mapping (bytes32 => uint) num_deposits_signed;
/// Event created on money deposit.
event Deposit(address recipient, uint value);
/// Event created on money withdraw.
event Withdraw(address recipient, uint value);
/// Event created on money transfer
event Transfer(address from, address to, uint value);
/// Collected signatures which should be relayed to home chain.
event CollectedSignatures(address authority, bytes32 messageHash);
/// Constructor.
function ForeignBridge(
uint requiredSignaturesParam,
address[] authoritiesParam
) public
{
require(requiredSignaturesParam != 0);
require(requiredSignaturesParam <= authoritiesParam.length);
requiredSignatures = requiredSignaturesParam;
for (uint i = 0; i < authoritiesParam.length; i++) {
authorities[authoritiesParam[i]] = true;
}
}
/// Multisig authority validation
modifier onlyAuthority() {
require(authorities[msg.sender]);
_;
}
/// Used to deposit money to the contract.
///
/// Usage maps instead of arrey allows to reduce gas consumption
/// from 91169 to 89348 (solc 0.4.19).
///
/// deposit recipient (bytes20)
/// deposit value (uint)
/// mainnet transaction hash (bytes32) // to avoid transaction duplication
function deposit(address recipient, uint value, bytes32 transactionHash) public onlyAuthority() {
// Protection from misbehaing authority
bytes32 hash_msg = keccak256(recipient, value, transactionHash);
bytes32 hash_sender = keccak256(msg.sender, hash_msg);
// Duplicated deposits
require(!deposits_signed[hash_sender]);
deposits_signed[hash_sender]= true;
uint signed = num_deposits_signed[hash_msg] + 1;
num_deposits_signed[hash_msg] = signed;
// TODO: this may cause troubles if requriedSignatures len is changed
if (signed == requiredSignatures) {
balances[recipient] += value;
Deposit(recipient, value);
}
}
/// Transfer `value` from `msg.sender`s local balance (on `foreign` chain) to `recipient` on `home` chain.
///
/// immediately decreases `msg.sender`s local balance.
/// emits a `Withdraw` event which will be picked up by the bridge authorities.
/// bridge authorities will then sign off (by calling `submitSignature`) on a message containing `value`,
/// `recipient` and the `hash` of the transaction on `foreign` containing the `Withdraw` event.
/// once `requiredSignatures` are collected a `CollectedSignatures` event will be emitted.
/// an authority will pick up `CollectedSignatures` an call `HomeBridge.withdraw`
/// which transfers `value - relayCost` to `recipient` completing the transfer.
function transferHomeViaRelay(address recipient, uint value) public {
require(balances[msg.sender] >= value);
balances[msg.sender] -= value;
Withdraw(recipient, value);
}
/// Transfer `value` to `recipient` on this `foreign` chain.
///
/// does not affect `home` chain. does not do a relay.
function transferLocal(address recipient, uint value) public {
require(balances[msg.sender] >= value);
// fails if value == 0, or if there is an overflow
require(balances[recipient] + value > balances[recipient]);
balances[msg.sender] -= value;
balances[recipient] += value;
Transfer(msg.sender, recipient, value);
}
/// Should be used as sync tool
///
/// Message is a message that should be relayed to main chain once authorities sign it.
///
/// Usage several maps instead of structure allows to reduce gas consumption
/// from 265102 to 242334 (solc 0.4.19).
///
/// for withdraw message contains:
/// withdrawal recipient (bytes20)
/// withdrawal value (uint)
/// foreign transaction hash (bytes32) // to avoid transaction duplication
function submitSignature(bytes signature, bytes message) public onlyAuthority() {
// Validate submited signatures
require(MessageSigning.recoverAddressFromSignedMessage(signature, message) == msg.sender);
// Valid withdraw message must have 84 bytes
require(message.length == 84);
bytes32 hash = keccak256(message);
bytes32 hash_sender = keccak256(msg.sender, hash);
uint signed = num_messages_signed[hash_sender] + 1;
if (signed > 1) {
// Duplicated signatures
require(!messages_signed[hash_sender]);
}
else {
// check if it will really reduce gas usage in case of the second transaction
// with the same hash
messages[hash] = message;
}
messages_signed[hash_sender] = true;
bytes32 sign_idx = keccak256(hash, (signed-1));
signatures[sign_idx]= signature;
num_messages_signed[hash_sender] = signed;
// TODO: this may cause troubles if requiredSignatures len is changed
if (signed == requiredSignatures) {
CollectedSignatures(msg.sender, hash);
}
}
/// Get signature
function signature(bytes32 hash, uint index) public view returns (bytes) {
bytes32 sign_idx = keccak256(hash, index);
return signatures[sign_idx];
}
/// Get message
function message(bytes32 hash) public view returns (bytes) {
return messages[hash];
}
}