09.SWC-109_Uninitialized Storage Pointer
2023-07-13 15:51:25 # 09.SWC

SWC-109_Uninitialized Storage Pointer

Uninitialized Storage Pointer

  • Description: Uninitialized local storage variables can point to unexpected storage locations in the contract, which can lead to intentional or unintentional vulnerabilities.

  • Remediation: Check if the contract requires a storage object as in many situations this is actually not the case. If a local variable is sufficient, mark the storage location of the variable explicitly with the memory attribute. If a storage variable is needed then initialise it upon declaration and additionally specify the storage location storage.

    Note: As of compiler version 0.5.0 and higher this issue has been systematically resolved as contracts with uninitialised storage pointers do no longer compile.

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pragma solidity ^0.4.19;

// CryptoRoulette
//
// Guess the number secretly stored in the blockchain and win the whole contract balance!
// A new number is randomly chosen after each try.
//
// To play, call the play() method with the guessed number (1-20). Bet price: 0.1 ether

contract CryptoRoulette {

uint256 private secretNumber;
uint256 public lastPlayed;
uint256 public betPrice = 0.1 ether;
address public ownerAddr;

struct Game {
address player;
uint256 number;
}
Game[] public gamesPlayed;

function CryptoRoulette() public {
ownerAddr = msg.sender;
shuffle();
}

function shuffle() internal {
// randomly set secretNumber with a value between 1 and 20
secretNumber = uint8(sha3(now, block.blockhash(block.number-1))) % 20 + 1;
}

function play(uint256 number) payable public {
require(msg.value >= betPrice && number <= 10);

// fixed: Game memory game
Game game; // Uninitialized Storage Pointer
game.player = msg.sender;
game.number = number;
gamesPlayed.push(game);

if (number == secretNumber) {
// win!
msg.sender.transfer(this.balance);
}

shuffle();
lastPlayed = now;
}

function kill() public {
if (msg.sender == ownerAddr && now > lastPlayed + 1 days) {
suicide(msg.sender);
}
}

function() public payable { }
}
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2023-07-13 15:51:25 # 09.SWC
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