smartbugs-curated/dataset/bad_randomness/blackjack.sol

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/*
* @article: https://blog.positive.com/predicting-random-numbers-in-ethereum-smart-contracts-e5358c6b8620
* @source: https://etherscan.io/address/0xa65d59708838581520511d98fb8b5d1f76a96cad#code
* @vulnerable_at_lines: 17,19,21
* @author: -
*/
pragma solidity ^0.4.2;
library Deck {
// returns random number from 0 to 51
// let's say 'value' % 4 means suit (0 - Hearts, 1 - Spades, 2 - Diamonds, 3 - Clubs)
// 'value' / 4 means: 0 - King, 1 - Ace, 2 - 10 - pip values, 11 - Jacket, 12 - Queen
function deal(address player, uint8 cardNumber) internal returns (uint8) {
// <yes> <report> BAD_RANDOMNESS
uint b = block.number;
// <yes> <report> BAD_RANDOMNESS
uint timestamp = block.timestamp;
// <yes> <report> BAD_RANDOMNESS
return uint8(uint256(keccak256(block.blockhash(b), player, cardNumber, timestamp)) % 52);
}
function valueOf(uint8 card, bool isBigAce) internal constant returns (uint8) {
uint8 value = card / 4;
if (value == 0 || value == 11 || value == 12) { // Face cards
return 10;
}
if (value == 1 && isBigAce) { // Ace is worth 11
return 11;
}
return value;
}
function isAce(uint8 card) internal constant returns (bool) {
return card / 4 == 1;
}
function isTen(uint8 card) internal constant returns (bool) {
return card / 4 == 10;
}
}
contract BlackJack {
using Deck for *;
uint public minBet = 50 finney; // 0.05 eth
uint public maxBet = 5 ether;
uint8 BLACKJACK = 21;
enum GameState { Ongoing, Player, Tie, House }
struct Game {
address player; // address игрока
uint bet; // стывка
uint8[] houseCards; // карты диллера
uint8[] playerCards; // карты игрока
GameState state; // состояние
uint8 cardsDealt;
}
mapping (address => Game) public games;
modifier gameIsGoingOn() {
if (games[msg.sender].player == 0 || games[msg.sender].state != GameState.Ongoing) {
throw; // game doesn't exist or already finished
}
_;
}
event Deal(
bool isUser,
uint8 _card
);
event GameStatus(
uint8 houseScore,
uint8 houseScoreBig,
uint8 playerScore,
uint8 playerScoreBig
);
event Log(
uint8 value
);
function BlackJack() {
}
function () payable {
}
// starts a new game
function deal() public payable {
if (games[msg.sender].player != 0 && games[msg.sender].state == GameState.Ongoing) {
throw; // game is already going on
}
if (msg.value < minBet || msg.value > maxBet) {
throw; // incorrect bet
}
uint8[] memory houseCards = new uint8[](1);
uint8[] memory playerCards = new uint8[](2);
// deal the cards
playerCards[0] = Deck.deal(msg.sender, 0);
Deal(true, playerCards[0]);
houseCards[0] = Deck.deal(msg.sender, 1);
Deal(false, houseCards[0]);
playerCards[1] = Deck.deal(msg.sender, 2);
Deal(true, playerCards[1]);
games[msg.sender] = Game({
player: msg.sender,
bet: msg.value,
houseCards: houseCards,
playerCards: playerCards,
state: GameState.Ongoing,
cardsDealt: 3
});
checkGameResult(games[msg.sender], false);
}
// deals one more card to the player
function hit() public gameIsGoingOn {
uint8 nextCard = games[msg.sender].cardsDealt;
games[msg.sender].playerCards.push(Deck.deal(msg.sender, nextCard));
games[msg.sender].cardsDealt = nextCard + 1;
Deal(true, games[msg.sender].playerCards[games[msg.sender].playerCards.length - 1]);
checkGameResult(games[msg.sender], false);
}
// finishes the game
function stand() public gameIsGoingOn {
var (houseScore, houseScoreBig) = calculateScore(games[msg.sender].houseCards);
while (houseScoreBig < 17) {
uint8 nextCard = games[msg.sender].cardsDealt;
uint8 newCard = Deck.deal(msg.sender, nextCard);
games[msg.sender].houseCards.push(newCard);
games[msg.sender].cardsDealt = nextCard + 1;
houseScoreBig += Deck.valueOf(newCard, true);
Deal(false, newCard);
}
checkGameResult(games[msg.sender], true);
}
// @param finishGame - whether to finish the game or not (in case of Blackjack the game finishes anyway)
function checkGameResult(Game game, bool finishGame) private {
// calculate house score
var (houseScore, houseScoreBig) = calculateScore(game.houseCards);
// calculate player score
var (playerScore, playerScoreBig) = calculateScore(game.playerCards);
GameStatus(houseScore, houseScoreBig, playerScore, playerScoreBig);
if (houseScoreBig == BLACKJACK || houseScore == BLACKJACK) {
if (playerScore == BLACKJACK || playerScoreBig == BLACKJACK) {
// TIE
if (!msg.sender.send(game.bet)) throw; // return bet to the player
games[msg.sender].state = GameState.Tie; // finish the game
return;
} else {
// HOUSE WON
games[msg.sender].state = GameState.House; // simply finish the game
return;
}
} else {
if (playerScore == BLACKJACK || playerScoreBig == BLACKJACK) {
// PLAYER WON
if (game.playerCards.length == 2 && (Deck.isTen(game.playerCards[0]) || Deck.isTen(game.playerCards[1]))) {
// Natural blackjack => return x2.5
if (!msg.sender.send((game.bet * 5) / 2)) throw; // send prize to the player
} else {
// Usual blackjack => return x2
if (!msg.sender.send(game.bet * 2)) throw; // send prize to the player
}
games[msg.sender].state = GameState.Player; // finish the game
return;
} else {
if (playerScore > BLACKJACK) {
// BUST, HOUSE WON
Log(1);
games[msg.sender].state = GameState.House; // finish the game
return;
}
if (!finishGame) {
return; // continue the game
}
// недобор
uint8 playerShortage = 0;
uint8 houseShortage = 0;
// player decided to finish the game
if (playerScoreBig > BLACKJACK) {
if (playerScore > BLACKJACK) {
// HOUSE WON
games[msg.sender].state = GameState.House; // simply finish the game
return;
} else {
playerShortage = BLACKJACK - playerScore;
}
} else {
playerShortage = BLACKJACK - playerScoreBig;
}
if (houseScoreBig > BLACKJACK) {
if (houseScore > BLACKJACK) {
// PLAYER WON
if (!msg.sender.send(game.bet * 2)) throw; // send prize to the player
games[msg.sender].state = GameState.Player;
return;
} else {
houseShortage = BLACKJACK - houseScore;
}
} else {
houseShortage = BLACKJACK - houseScoreBig;
}
// ?????????????????????? почему игра заканчивается?
if (houseShortage == playerShortage) {
// TIE
if (!msg.sender.send(game.bet)) throw; // return bet to the player
games[msg.sender].state = GameState.Tie;
} else if (houseShortage > playerShortage) {
// PLAYER WON
if (!msg.sender.send(game.bet * 2)) throw; // send prize to the player
games[msg.sender].state = GameState.Player;
} else {
games[msg.sender].state = GameState.House;
}
}
}
}
function calculateScore(uint8[] cards) private constant returns (uint8, uint8) {
uint8 score = 0;
uint8 scoreBig = 0; // in case of Ace there could be 2 different scores
bool bigAceUsed = false;
for (uint i = 0; i < cards.length; ++i) {
uint8 card = cards[i];
if (Deck.isAce(card) && !bigAceUsed) { // doesn't make sense to use the second Ace as 11, because it leads to the losing
scoreBig += Deck.valueOf(card, true);
bigAceUsed = true;
} else {
scoreBig += Deck.valueOf(card, false);
}
score += Deck.valueOf(card, false);
}
return (score, scoreBig);
}
function getPlayerCard(uint8 id) public gameIsGoingOn constant returns(uint8) {
if (id < 0 || id > games[msg.sender].playerCards.length) {
throw;
}
return games[msg.sender].playerCards[id];
}
function getHouseCard(uint8 id) public gameIsGoingOn constant returns(uint8) {
if (id < 0 || id > games[msg.sender].houseCards.length) {
throw;
}
return games[msg.sender].houseCards[id];
}
function getPlayerCardsNumber() public gameIsGoingOn constant returns(uint) {
return games[msg.sender].playerCards.length;
}
function getHouseCardsNumber() public gameIsGoingOn constant returns(uint) {
return games[msg.sender].houseCards.length;
}
function getGameState() public constant returns (uint8) {
if (games[msg.sender].player == 0) {
throw; // game doesn't exist
}
Game game = games[msg.sender];
if (game.state == GameState.Player) {
return 1;
}
if (game.state == GameState.House) {
return 2;
}
if (game.state == GameState.Tie) {
return 3;
}
return 0; // the game is still going on
}
}