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parity-bridge-research
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This commit is contained in:
Alexander Kolotov 2018-02-23 04:14:26 +03:00
parent e94004d09a
commit 421aba08db
1 changed files with 144 additions and 86 deletions
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230
erc20/bridge/contracts/bridge_erc20_foreign_optimized.sol
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@ -5,7 +5,7 @@ pragma solidity ^0.4.19;
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++) {
for (uint256 i = 0; i < array.length; i++) {
if (array[i] == value) {
return true;
}
@ -15,10 +15,10 @@ library Helpers {
// returns the digits of `inputValue` as a string.
// example: `uintToString(12345678)` returns `"12345678"`
function uintToString(uint inputValue) internal pure returns (string) {
function uintToString(uint256 inputValue) internal pure returns (string) {
// figure out the length of the resulting string
uint length = 0;
uint currentValue = inputValue;
uint256 length = 0;
uint256 currentValue = inputValue;
do {
length++;
currentValue /= 10;
@ -26,7 +26,7 @@ library Helpers {
// allocate enough memory
bytes memory result = new bytes(length);
// construct the string backwards
uint i = length - 1;
uint256 i = length - 1;
currentValue = inputValue;
do {
result[i--] = byte(48 + currentValue % 10);
@ -34,6 +34,35 @@ library Helpers {
} while (currentValue != 0);
return string(result);
}
/// returns whether signatures (whose components are in `vs`, `rs`, `ss`)
/// contain `requiredSignatures` distinct correct signatures
/// where signer is in `allowed_signers`
/// that signed `message`
function hasEnoughValidSignatures(bytes message, uint8[] vs, bytes32[] rs, bytes32[] ss, address[] allowed_signers, uint256 requiredSignatures) internal pure returns (bool) {
// not enough signatures
if (vs.length < requiredSignatures) {
return false;
}
var hash = MessageSigning.hashMessage(message);
var encountered_addresses = new address[](allowed_signers.length);
for (uint256 i = 0; i < requiredSignatures; i++) {
var recovered_address = ecrecover(hash, vs[i], rs[i], ss[i]);
// only signatures by addresses in `addresses` are allowed
if (!addressArrayContains(allowed_signers, recovered_address)) {
return false;
}
// duplicate signatures are not allowed
if (addressArrayContains(encountered_addresses, recovered_address)) {
return false;
}
encountered_addresses[i] = recovered_address;
}
return true;
}
}
@ -46,6 +75,10 @@ library HelpersTest {
function uintToString(uint256 inputValue) public pure returns (string str) {
return Helpers.uintToString(inputValue);
}
function hasEnoughValidSignatures(bytes message, uint8[] vs, bytes32[] rs, bytes32[] ss, address[] addresses, uint256 requiredSignatures) public pure returns (bool) {
return Helpers.hasEnoughValidSignatures(message, vs, rs, ss, addresses, requiredSignatures);
}
}
@ -83,10 +116,11 @@ library MessageSigningTest {
library Message {
// layout of message :: bytes:
// offset 0: 32 bytes :: uint (little endian) - message length
// offset 0: 32 bytes :: uint256 (little endian) - message length
// offset 32: 20 bytes :: address - recipient address
// offset 52: 32 bytes :: uint (little endian) - value
// offset 52: 32 bytes :: uint256 (little endian) - value
// offset 84: 32 bytes :: bytes32 - transaction hash
// offset 116: 32 bytes :: uint256 (little endian) - home gas price
// bytes 1 to 32 are 0 because message length is stored as little endian.
// mload always reads 32 bytes.
@ -108,8 +142,8 @@ library Message {
return recipient;
}
function getValue(bytes message) internal pure returns (uint) {
uint value;
function getValue(bytes message) internal pure returns (uint256) {
uint256 value;
// solium-disable-next-line security/no-inline-assembly
assembly {
value := mload(add(message, 52))
@ -125,6 +159,15 @@ library Message {
}
return hash;
}
function getHomeGasPrice(bytes message) internal pure returns (uint256) {
uint256 gasPrice;
// solium-disable-next-line security/no-inline-assembly
assembly {
gasPrice := mload(add(message, 116))
}
return gasPrice;
}
}
@ -134,13 +177,17 @@ library MessageTest {
return Message.getRecipient(message);
}
function getValue(bytes message) public pure returns (uint) {
function getValue(bytes message) public pure returns (uint256) {
return Message.getValue(message);
}
function getTransactionHash(bytes message) public pure returns (bytes32) {
return Message.getTransactionHash(message);
}
function getHomeGasPrice(bytes message) public pure returns (uint256) {
return Message.getHomeGasPrice(message);
}
}
@ -148,14 +195,14 @@ contract HomeBridge {
/// Number of authorities signatures required to withdraw the money.
///
/// Must be lesser than number of authorities.
uint public requiredSignatures;
uint256 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;
uint256 public estimatedGasCostOfWithdraw;
/// Contract authorities.
address[] public authorities;
@ -164,32 +211,16 @@ contract HomeBridge {
mapping (bytes32 => bool) withdraws;
/// Event created on money deposit.
event Deposit (address recipient, uint value);
event Deposit (address recipient, uint256 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;
}
_;
}
event Withdraw (address recipient, uint256 value);
/// Constructor.
function HomeBridge(
uint requiredSignaturesParam,
uint256 requiredSignaturesParam,
address[] authoritiesParam,
uint estimatedGasCostOfWithdrawParam
uint256 estimatedGasCostOfWithdrawParam
) public
{
require(requiredSignaturesParam != 0);
@ -204,31 +235,44 @@ contract HomeBridge {
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();
}
event DebugInt(uint256);
event DebugAddress(address);
event DebugBytes32(bytes32);
/// an upper bound to the cost of relaying a withdraw by calling HomeBridge.withdraw
function getWithdrawRelayCost() public view returns (uint) {
return estimatedGasCostOfWithdraw * tx.gasprice;
}
/// final step of a withdraw.
/// checks that `requiredSignatures` `authorities` have signed of on the `message`.
/// then transfers `value` to `recipient` (both extracted from `message`).
/// see message library above for a breakdown of the `message` contents.
/// `vs`, `rs`, `ss` are the components of the signatures.
/// anyone can call this, provided they have the message and required signatures!
/// only the `authorities` can create these signatures.
/// `requiredSignatures` authorities can sign arbitrary `message`s
/// transfering any ether `value` out of this contract to `recipient`.
/// bridge users must trust a majority of `requiredSignatures` of the `authorities`.
function withdraw(uint8[] vs, bytes32[] rs, bytes32[] ss, bytes message) public {
require(message.length == 116);
// check that at least `requiredSignatures` `authorities` have signed `message`
require(Helpers.hasEnoughValidSignatures(message, vs, rs, ss, authorities, requiredSignatures));
/// 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);
uint256 value = Message.getValue(message);
bytes32 hash = Message.getTransactionHash(message);
//This works
//uint256 homeGasPrice = Message.getHomeGasPrice(message);
//Debug(message);
uint256 homeGasPrice = 1000000000 wei;
// if the recipient calls `withdraw` they can choose the gas price freely.
// if anyone else calls `withdraw` they have to use the gas price
// `homeGasPrice` specified by the user initiating the withdraw.
// this is a security mechanism designed to shut down
// malicious senders setting extremely high gas prices
// and effectively burning recipients withdrawn value.
// see https://github.com/paritytech/parity-bridge/issues/112
// for further explanation.
//require((recipient == msg.sender) || (tx.gasprice == homeGasPrice));
// The following two statements guard against reentry into this function.
// Duplicated withdraw or reentry.
@ -236,18 +280,21 @@ contract HomeBridge {
// 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();
uint256 estimatedWeiCostOfWithdraw = estimatedGasCostOfWithdraw * homeGasPrice;
// charge recipient for relay cost
uint valueRemainingAfterSubtractingCost = value - estimatedWeiCostOfWithdraw;
uint256 valueRemainingAfterSubtractingCost = value - estimatedWeiCostOfWithdraw;
DebugAddress(recipient);
//DebugAddress(msg.sender);
DebugInt(value);
//DebugBytes32(hash);
DebugInt(valueRemainingAfterSubtractingCost * 1);
DebugInt(this.balance);
// pay out recipient
recipient.transfer(valueRemainingAfterSubtractingCost);
//recipient.transfer(valueRemainingAfterSubtractingCost);
recipient.transfer(this.balance)
// refund relay cost to relaying authority
msg.sender.transfer(estimatedWeiCostOfWithdraw);
@ -265,8 +312,20 @@ contract ERC20 {
contract ForeignBridge {
/// Number of authorities signatures required to withdraw the money.
///
/// Must be lesser than number of authorities.
uint public requiredSignatures;
/// Must be less than number of authorities.
uint256 public requiredSignatures;
uint256 public estimatedGasCostOfWithdraw;
// Original parity-bridge assumes that anyone could forward final
// withdraw confirmation to the HomeBridge contract. That's why
// they need to make sure that no one is trying to steal funds by
// setting a big gas price of withdraw transaction. So,
// funds sender is responsible to limit this by setting gasprice
// as part of withdraw request.
// Since it is not the case for POA CCT bridge, gasprice is set
// to 1 Gwei which is minimal gasprice for POA network.
uint256 homeGasPrice = 1000000000 wei;
/// Contract authorities.
mapping (address => bool) authorities;
@ -291,37 +350,37 @@ contract ForeignBridge {
mapping (bytes32 => bool) tokenAddressAprroval_signs;
mapping (address => uint256) num_tokenAddressAprroval_signs;
/// Event created on money deposit.
event Deposit(address recipient, uint value);
/// triggered when relay of deposit from HomeBridge is complete
event Deposit(address recipient, uint256 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);
event Withdraw(address recipient, uint256 value, uint256 homeGasPrice);
/// Collected signatures which should be relayed to home chain.
event CollectedSignatures(address authority, bytes32 messageHash);
event CollectedSignatures(address authorityResponsibleForRelay, bytes32 messageHash);
/// Event created when new token address is set up.
event TokenAddress(address token);
/// Constructor.
function ForeignBridge(
uint requiredSignaturesParam,
address[] authoritiesParam
uint256 _requiredSignatures,
address[] _authorities,
uint256 _estimatedGasCostOfWithdraw
) public
{
require(requiredSignaturesParam != 0);
require(requiredSignaturesParam <= authoritiesParam.length);
requiredSignatures = requiredSignaturesParam;
for (uint i = 0; i < authoritiesParam.length; i++) {
authorities[authoritiesParam[i]] = true;
require(_requiredSignatures != 0);
require(_requiredSignatures <= _authorities.length);
requiredSignatures = _requiredSignatures;
for (uint i = 0; i < _authorities.length; i++) {
authorities[_authorities[i]] = true;
}
estimatedGasCostOfWithdraw = _estimatedGasCostOfWithdraw;
}
/// Multisig authority validation
/// require that sender is an authority
modifier onlyAuthority() {
require(authorities[msg.sender]);
_;
@ -358,7 +417,7 @@ contract ForeignBridge {
/// from 91169 to 89348 (solc 0.4.19).
///
/// deposit recipient (bytes20)
/// deposit value (uint)
/// deposit value (uint256)
/// mainnet transaction hash (bytes32) // to avoid transaction duplication
function deposit(address recipient, uint value, bytes32 transactionHash) public onlyAuthority() {
require(erc20token != address(0x0));
@ -405,7 +464,7 @@ contract ForeignBridge {
require(msg.sender == address(erc20token));
require(erc20token.allowance(_from, this) >= _value);
erc20token.transferFrom(_from, this, _value);
Withdraw(_from, _value);
Withdraw(_from, _value, homeGasPrice);
return true;
}
@ -419,14 +478,13 @@ contract ForeignBridge {
///
/// for withdraw message contains:
/// withdrawal recipient (bytes20)
/// withdrawal value (uint)
/// withdrawal value (uint256)
/// 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);
// ensure that `signature` is really `message` signed by `msg.sender`
require(msg.sender == MessageSigning.recoverAddressFromSignedMessage(signature, message));
// Valid withdraw message must have 84 bytes
require(message.length == 84);
require(message.length == 116);
bytes32 hash = keccak256(message);
bytes32 hash_sender = keccak256(msg.sender, hash);