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Add fix for the approve() mitigation.

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This commit is contained in:
Mikko Ohtamaa
2017-05-17 01:33:13 +03:00
parent ff61c7d92d
commit a3446507ec
1 changed files with 7 additions and 0 deletions
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7
contracts/token/StandardToken.sol
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@ -29,6 +29,13 @@ contract StandardToken is BasicToken, ERC20 {
} }
function approve(address _spender, uint _value) { function approve(address _spender, uint _value) {
// To change the approve amount you first have to reduce the addresses`
// allowance to zero by calling `approve(_spender,0)` if it is not
// already 0 to mitigate the race condition described here:
// https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
if ((_amount!=0) && (allowed[msg.sender][_spender] !=0)) throw;
allowed[msg.sender][_spender] = _value; allowed[msg.sender][_spender] = _value;
Approval(msg.sender, _spender, _value); Approval(msg.sender, _spender, _value);
} }