The 8 August 2015 messaging contract whose sendMessage always reverts, indexing a hash array that is never lengthened.
Historical Significance
An onchain messaging contract deployed on 8 August 2015 by 0x8674c218f0351a62c3ba78c34fd2182a93da94e2, the version where sendMessage tries to index the recipient's hash list. It reads the nonce, casts it to bytes32 as the message key, advances the nonce, writes Message(uint64(now), contents) into mapping (address => mapping (bytes32 => Message)) messages under the recipient's address, and then assigns hashes[to][n] = hash. That last line is the flaw: hashes[to] is never lengthened, so the index is always past the end of the array and the whole call reverts. Twenty five minutes later the author deployed the same contract with that line deleted. Recipients read their mail with getMessageTime and getMessageContents, both keyed on msg.sender, and deleteMessage clears a message and zeroes its entry in the caller's hash list. Source recovered by exact bytecode match: solc v0.1.1+commit.6ff4cd6 with the optimizer on reproduces all 1430 bytes of the creation transaction.
Context
Deployed 8 August 2015, the second day of the Ethereum Frontier network.
Key Facts
Description
An onchain messaging contract deployed on 8 August 2015 by 0x8674c218f0351a62c3ba78c34fd2182a93da94e2, the version where sendMessage tries to index the recipient's hash list. It reads the nonce, casts it to bytes32 as the message key, advances the nonce, writes Message(uint64(now), contents) into mapping (address => mapping (bytes32 => Message)) messages under the recipient's address, and then assigns hashes[to][n] = hash. That last line is the flaw: hashes[to] is never lengthened, so the index is always past the end of the array and the whole call reverts. Twenty five minutes later the author deployed the same contract with that line deleted. Recipients read their mail with getMessageTime and getMessageContents, both keyed on msg.sender, and deleteMessage clears a message and zeroes its entry in the caller's hash list. Source recovered by exact bytecode match: solc v0.1.1+commit.6ff4cd6 with the optimizer on reproduces all 1430 bytes of the creation transaction.
Source Verified
near_exact_match: reconstructed source with nonce-based sha3 hashing. All selectors confirmed via openchain.xyz (including affed0e0=nonce()).
Heuristic Analysis
The following characteristics were detected through bytecode analysis and may not be accurate.
Frontier Era
The initial release of Ethereum. A bare-bones implementation for technical users.
Bytecode Overview
Verified Source Available
Source verified through compiler archaeology (near-exact bytecode match).
Show source code (Solidity)
contract Messaging {
mapping(bytes32 => string) messageContents;
mapping(bytes32 => uint) messageTime;
mapping(address => bytes32[]) public hashes;
mapping(address => mapping(bytes32 => bool)) public messages;
uint public nonce;
function sendMessage(address to, string content) {
bytes32 h = sha3(msg.sender, to, content, nonce++);
messageContents[h] = content;
messageTime[h] = block.timestamp;
hashes[to].push(h);
}
function getMessageContents(bytes32 hash) constant returns (string) {
return messageContents[hash];
}
function getMessageTime(bytes32 hash) constant returns (uint) {
return messageTime[hash];
}
function deleteMessage(bytes32 hash) {
delete messageContents[hash];
delete messageTime[hash];
}
}External Links
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