智能合约安全-parity多重签名钱包安全漏洞

漏洞原因：

因为initWallet函数是公开函数( public function) ，攻击者调用initWallet，重新初始化钱包会把之前合约钱包所有者覆盖, 即可改变钱包所有者。

漏洞代码：

  // constructor - just pass on the owner array to the multiowned and

  // the limit to daylimit

  function initWallet(address[] _owners, uint _required, uint _daylimit) {

    initDaylimit(_daylimit);

    initMultiowned(_owners, _required);

  }

  // constructor - stores initial daily limit and records the present day's index.

  function initDaylimit(uint _limit) {

    m_dailyLimit = _limit;

    m_lastDay = today();

  }

  // 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) {

    m_numOwners = _owners.length + ;

    m_owners[] = uint(msg.sender);

    m_ownerIndex[uint(msg.sender)] = ;

    for (uint i = ; i < _owners.length; ++i)

    {

      m_owners[ + i] = uint(_owners[i]);

      m_ownerIndex[uint(_owners[i])] =  + i;

    }

    m_required = _required;

  }

修复方法：

设置 initMultiowned 和 initDaylimit 禁止外部调用，给initWallet添加only_uninitialized函数修改器，确保initWallt只被调用一次。

安全修复代码:

  // throw unless the contract is not yet initialized.

  modifier only_uninitialized { if (m_numOwners > ) throw; _; }

  // 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 - stores initial daily limit and records the present day's index.

  function initDaylimit(uint _limit) internal {

    m_dailyLimit = _limit;

    m_lastDay = today();

  }

  // 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) internal {

    m_numOwners = _owners.length + ;

    m_owners[] = uint(msg.sender);

    m_ownerIndex[uint(msg.sender)] = ;

    for (uint i = ; i < _owners.length; ++i)

    {

      m_owners[ + i] = uint(_owners[i]);

      m_ownerIndex[uint(_owners[i])] =  + i;

    }

    m_required = _required;

  }

POC

web3.eth.contract(MultiSigParityAbit).at(Vulnerable_Address).initWallet.getData([YOUR_ADDRESS], ,)

POC未测试，待测。

REF:http://shellcode.se/programming/simple-mistake-leads-to-30m-usd-theft/

巴特西

智能合约安全-parity多重签名钱包安全漏洞

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