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pragma solidity ^0.5.10;
/**
* @title CheckpointOracle
* @author Gary Rong<garyrong@ethereum.org>, Martin Swende <martin.swende@ethereum.org>
* @dev Implementation of the blockchain checkpoint registrar.
*/
contract CheckpointOracle {
/*
Events
*/
// NewCheckpointVote is emitted when a new checkpoint proposal receives a vote.
event NewCheckpointVote(uint64 indexed index, bytes32 checkpointHash, uint8 v, bytes32 r, bytes32 s);
/*
Public Functions
*/
constructor(address[] memory _adminlist, uint _sectionSize, uint _processConfirms, uint _threshold) public {
for (uint i = 0; i < _adminlist.length; i++) {
admins[_adminlist[i]] = true;
adminList.push(_adminlist[i]);
}
sectionSize = _sectionSize;
processConfirms = _processConfirms;
threshold = _threshold;
}
/**
* @dev Get latest stable checkpoint information.
* @return section index
* @return checkpoint hash
* @return block height associated with checkpoint
*/
function GetLatestCheckpoint()
view
public
returns(uint64, bytes32, uint) {
return (sectionIndex, hash, height);
}
// SetCheckpoint sets a new checkpoint. It accepts a list of signatures
// @_recentNumber: a recent blocknumber, for replay protection
// @_recentHash : the hash of `_recentNumber`
// @_hash : the hash to set at _sectionIndex
// @_sectionIndex : the section index to set
// @v : the list of v-values
// @r : the list or r-values
// @s : the list of s-values
function SetCheckpoint(
uint _recentNumber,
bytes32 _recentHash,
bytes32 _hash,
uint64 _sectionIndex,
uint8[] memory v,
bytes32[] memory r,
bytes32[] memory s)
public
returns (bool)
{
// Ensure the sender is authorized.
require(admins[msg.sender]);
// These checks replay protection, so it cannot be replayed on forks,
// accidentally or intentionally
require(blockhash(_recentNumber) == _recentHash);
// Ensure the batch of signatures are valid.
require(v.length == r.length);
require(v.length == s.length);
// Filter out "future" checkpoint.
if (block.number < (_sectionIndex+1)*sectionSize+processConfirms) {
return false;
}
// Filter out "old" announcement
if (_sectionIndex < sectionIndex) {
return false;
}
// Filter out "stale" announcement
if (_sectionIndex == sectionIndex && (_sectionIndex != 0 || height != 0)) {
return false;
}
// Filter out "invalid" announcement
if (_hash == ""){
return false;
}
// EIP 191 style signatures
//
// Arguments when calculating hash to validate
// 1: byte(0x19) - the initial 0x19 byte
// 2: byte(0) - the version byte (data with intended validator)
// 3: this - the validator address
// -- Application specific data
// 4 : checkpoint section_index(uint64)
// 5 : checkpoint hash (bytes32)
// hash = keccak256(checkpoint_index, section_head, cht_root, bloom_root)
bytes32 signedHash = keccak256(abi.encodePacked(byte(0x19), byte(0), this, _sectionIndex, _hash));
address lastVoter = address(0);
// In order for us not to have to maintain a mapping of who has already
// voted, and we don't want to count a vote twice, the signatures must
// be submitted in strict ordering.
for (uint idx = 0; idx < v.length; idx++){
address signer = ecrecover(signedHash, v[idx], r[idx], s[idx]);
require(admins[signer]);
require(uint256(signer) > uint256(lastVoter));
lastVoter = signer;
emit NewCheckpointVote(_sectionIndex, _hash, v[idx], r[idx], s[idx]);
// Sufficient signatures present, update latest checkpoint.
if (idx+1 >= threshold){
hash = _hash;
height = block.number;
sectionIndex = _sectionIndex;
return true;
}
}
// We shouldn't wind up here, reverting un-emits the events
revert();
}
/**
* @dev Get all admin addresses
* @return address list
*/
function GetAllAdmin()
public
view
returns(address[] memory)
{
address[] memory ret = new address[](adminList.length);
for (uint i = 0; i < adminList.length; i++) {
ret[i] = adminList[i];
}
return ret;
}
/*
Fields
*/
// A map of admin users who have the permission to update CHT and bloom Trie root
mapping(address => bool) admins;
// A list of admin users so that we can obtain all admin users.
address[] adminList;
// Latest stored section id
uint64 sectionIndex;
// The block height associated with latest registered checkpoint.
uint height;
// The hash of latest registered checkpoint.
bytes32 hash;
// The frequency for creating a checkpoint
//
// The default value should be the same as the checkpoint size(32768) in the ethereum.
uint sectionSize;
// The number of confirmations needed before a checkpoint can be registered.
// We have to make sure the checkpoint registered will not be invalid due to
// chain reorg.
//
// The default value should be the same as the checkpoint process confirmations(256)
// in the ethereum.
uint processConfirms;
// The required signatures to finalize a stable checkpoint.
uint threshold;
}