27 lines
899 B
Solidity
27 lines
899 B
Solidity
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/*
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* @source: https://github.com/SmartContractSecurity/SWC-registry/blob/master/test_cases/weak_randomness/random_number_generator.sol
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* @author: -
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* @vulnerable_at_lines: 12,18,20,22
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*/
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pragma solidity ^0.4.25;
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// Based on TheRun contract deployed at 0xcac337492149bDB66b088bf5914beDfBf78cCC18.
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contract RandomNumberGenerator {
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// <yes> <report> BAD_RANDOMNESS
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uint256 private salt = block.timestamp;
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function random(uint max) view private returns (uint256 result) {
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// Get the best seed for randomness
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uint256 x = salt * 100 / max;
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// <yes> <report> BAD_RANDOMNESS
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uint256 y = salt * block.number / (salt % 5);
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// <yes> <report> BAD_RANDOMNESS
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uint256 seed = block.number / 3 + (salt % 300) + y;
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// <yes> <report> BAD_RANDOMNESS
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uint256 h = uint256(blockhash(seed));
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// Random number between 1 and max
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return uint256((h / x)) % max + 1;
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}
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}
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