The escrow whose rewritten guard locks out every caller
Historical Significance
A textbook De Morgan slip preserved on chain: the same rule that works when written as equals and or becomes unsatisfiable when rewritten as not equals and or.
Context
Deployed in the Homestead era, when an escrow was something you wrote yourself in twenty lines rather than something you called.
Key Facts
Description
Escrow holds ether for a buyer, a seller and an arbiter, with finalize paying the seller and refund paying the buyer. The guard here reads if the caller is not the buyer or is not the arbiter then revert, which is the wrong negation of an or: it demands that one caller be both parties at once, so neither function can ever run and the balance cannot move. An earlier deployment by the same account expressed the same rule positively and works. Deployed on 17 May 2017 by 0x1db3439a222c519ab44bb1144fc28167b4fa6ee6, the account of Vitalik Buterin, with 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 as the arbiter.
Source Verified
Executable runtime reproduces byte-for-byte from the reconstructed source with solc 0.4.11, optimizer on; only the swarm metadata hash differs. The buggy || guard (always true) is required to match. runtime sha256 b1e345aaecdee9afa5ddc48f57dbc700faafcbbf16250c0a35791825bfd65442.
Historian Categories
Heuristic Analysis
The following characteristics were detected through bytecode analysis and may not be accurate.
Spurious Dragon Era
Continued DoS protection. State trie clearing.
Bytecode Overview
Verified Source Available
This contract has verified source code.
View Verification ProofShow source code (Solidity)
// Verified by EthereumHistory (ethereumhistory.com)
contract Escrow {
address buyer;
address seller;
address arbitrator;
function Escrow(address _seller, address _arbitrator) {
seller = _seller;
arbitrator = _arbitrator;
buyer = msg.sender;
}
function finalize() {
if (msg.sender != buyer || msg.sender != arbitrator) throw;
seller.send(this.balance);
}
function refund() {
if (msg.sender != seller || msg.sender != arbitrator) throw;
buyer.send(this.balance);
}
}External Links
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