parity多签名合约漏洞分析

昨晚出事后看了安全公告：https://paritytech.io/blog/security-alert.html

分析合约代码后：https://etherscan.io/address/0x863df6bfa4469f3ead0be8f9f2aae51c91a907b4#code

发现漏洞由如下代码段引起:

  // constructor - just pass on the owner array to the multiowned and
  // the limit to daylimit
  function initWallet(address[] _owners, uint _required, uint _daylimit) only_uninitialized {
    initDaylimit(_daylimit);
    initMultiowned(_owners, _required);
  }


  // constructor is given number of sigs required to do protected "onlymanyowners" transactions
  // as well as the selection of addresses capable of confirming them.
  function initMultiowned(address[] _owners, uint _required) only_uninitialized {
    m_numOwners = _owners.length + 1;
    m_owners[1] = uint(msg.sender);
    m_ownerIndex[uint(msg.sender)] = 1;
    for (uint i = 0; i < _owners.length; ++i)
    {
      m_owners[2 + i] = uint(_owners[i]);
      m_ownerIndex[uint(_owners[i])] = 2 + i;
    }
    m_required = _required;
  }

这个函数假定创建者会调用initWallet函数，但是initWallet根本没有任何鉴权，任何人都可以成为owner，然后就可以调用kill函数杀死合约自身。

  // kills the contract sending everything to `_to`.
  function kill(address _to) onlymanyowners(sha3(msg.data)) external {
    suicide(_to);
  }

自杀之后，唯一可以用的函数只有

  // gets called when no other function matches
  function() payable {
    // just being sent some cash?
    if (msg.value > 0)
      Deposit(msg.sender, msg.value);
  }

parity是我现在用的eth客户端，速度快，体验好，然而安全问题是0容忍的，出现安全事故也是挺震惊的。

事件追踪：
https://paritytech.io/blog/parity-technologies-multi-sig-wallet-issue-update.html
https://paritytech.io/blog/security-is-a-process-a-postmortem-on-the-parity-multi-sig-library-self-destruct.html