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swarm: Fixes reentrancy bug allowing a malicious beneficiary to withdraw more

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funds than in the cheque through a recursive callback of cash() from the
default function of the contract at the beneficiary address.
This commit is contained in:
Daniel A. Nagy 2016-08-29 15:52:15 +02:00
parent d9fb99c4b3
commit 3c6cdf8821
1 changed files with 5 additions and 3 deletions
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8
swarm/services/chequebook/contract/chequebook.sol
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@ -28,9 +28,11 @@ contract chequebook is mortal {
// Attempt sending the difference between the cumulative amount on the cheque // Attempt sending the difference between the cumulative amount on the cheque
// and the cumulative amount on the last cashed cheque to beneficiary. // and the cumulative amount on the last cashed cheque to beneficiary.
if (amount - sent[beneficiary] >= this.balance) { if (amount - sent[beneficiary] >= this.balance) {
if (beneficiary.send(amount - sent[beneficiary])) { // update the cumulative amount before sending
// Upon success, update the cumulative amount. sent[beneficiary] = amount;
sent[beneficiary] = amount; if (!beneficiary.send(amount - sent[beneficiary])) {
// Upon failure to execute send, revert everything
throw;
} }
} else { } else {
// Upon failure, punish owner for writing a bounced cheque. // Upon failure, punish owner for writing a bounced cheque.