60 lines
1.6 KiB
Solidity
60 lines
1.6 KiB
Solidity
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/*
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* @article: https://blog.positive.com/predicting-random-numbers-in-ethereum-smart-contracts-e5358c6b8620
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* @source: https://etherscan.io/address/0xa11e4ed59dc94e69612f3111942626ed513cb172#code
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* @vulnerable_at_lines: 43
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* @author: -
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*/
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pragma solidity ^0.4.15;
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/// @title Ethereum Lottery Game.
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contract EtherLotto {
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// Amount of ether needed for participating in the lottery.
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uint constant TICKET_AMOUNT = 10;
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// Fixed amount fee for each lottery game.
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uint constant FEE_AMOUNT = 1;
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// Address where fee is sent.
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address public bank;
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// Public jackpot that each participant can win (minus fee).
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uint public pot;
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// Lottery constructor sets bank account from the smart-contract owner.
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function EtherLotto() {
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bank = msg.sender;
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}
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// Public function for playing lottery. Each time this function
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// is invoked, the sender has an oportunity for winning pot.
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function play() payable {
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// Participants must spend some fixed ether before playing lottery.
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assert(msg.value == TICKET_AMOUNT);
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// Increase pot for each participant.
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pot += msg.value;
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// Compute some *almost random* value for selecting winner from current transaction.
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// <yes> <report> TIME_MANIPULATION
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var random = uint(sha3(block.timestamp)) % 2;
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// Distribution: 50% of participants will be winners.
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if (random == 0) {
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// Send fee to bank account.
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bank.transfer(FEE_AMOUNT);
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// Send jackpot to winner.
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msg.sender.transfer(pot - FEE_AMOUNT);
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// Restart jackpot.
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pot = 0;
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}
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}
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}
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